9.10 New Features

CAD package for electromagnetic and thermal analysis using finite elements

FLUX® 9.10

2D and 3D Applications

New features

Copyright – February 2005

FLUX software : Copyright CEDRAT/INPG/CNRS/EDF CAOBIBS software : Copyright ECL/CEDRAT/CNRS/INPG FLUX documentation : Copyright CEDRAT

FLUX’s Quality Assessment 2D Application : Electricité de France, registered number AQMIL002 3D Application : Electricité de France, registered number AQMIL013

This user’s guide was published on 11 February 2005

Ref. :

K101-A-910-EN-02/05

CEDRAT 15, Chemin de Malacher - Inovallée

38246 MEYLAN Cedex France

Phone: +33 (0)4.76.90.50.45 Fax : +33 (0)4.56.38.08.30

Email : [email protected]

Web : http://www.cedrat.com

FLUX® 9.10 CONTENTS

TABLE OF CONTENTS

USER'S GUIDE PAGE A

CONTENTS FLUX® 9.10

PAGE B USER'S GUIDE


CONTENTS

1. Foreword 1 1.1. Version 9 and the 2D/3D unification project 2 1.2. The software documentation 3

1.2.1. The software documentation: whatever is available so far 4 1.2.2. The user’s guide and the 2D/3D unification project 5 1.2.3. The user’s guide: the versions (on paper and on line) 6 1.2.4. The tutorials and the technical papers for the 2D applications 7 1.2.5. The tutorials and technical papers for the 3D applications 8

2. Introduction to the novelties of FLUX version 9.10 9 2.1. The new FLUX pre-processor 11

2.1.1. FLUX environment and management of data 12 2.1.2. Import of geometry/meshing and correction tools 13 2.1.3. Description of the physical properties 14

2.2. Other novelties 15

3. Working environment and data management 17 3.1. Working environment and graphic representation 19

3.1.1. Presentation of working environment 20 3.1.2. Modifying the environment 24 3.1.3. Graphic 25

3.2. Data management 27 3.2.1. Entities handling: “indirect” creation 28 3.2.2. Entities handling: array editing 29

USER'S GUIDE PAGE C


4. Geometry/mesh importation: principles 31 4.1. Geometry/mesh importation: overview 33

4.1.1. Importation formats 34 4.1.2. Principle of conversion and options for conversion 35

4.2. Geometry importation (IGES, STEP, DXF, STL, FBD, INTER formats) 39 4.2.1. Process of geometry importation 40 4.2.2. Stage of conversion 41 4.2.3. Stage of geometry checking: concept of geometric fault 43 4.2.4. Stage of geometric faults correction / geometry simplification 45 4.2.5. Geometry importation: strategies 48

4.3. Mesh importation (NASTRAN, PATRAN, UNV Ideas formats) 49 4.3.1. Process of mesh importation 50 4.3.2. Stage of conversion 51 4.3.3. Stage of fusion 52 4.3.4. Stage of positioning 55 4.3.5. Mesh importation: strategies 56

5. News of physical preprocessor 59 5.1. List of principal new features 61

5.1.1. Physical description 62 5.1.2. Physical applications: magnetic, electric, thermal 63 5.1.3. Materials databases 64

5.2. Advices for 2D users 65

6. News of 3D postprocessor 67 6.1. Storage of physical quantities in the nodes 69

6.1.1. Storage of quantities in the nodes: foreword 70 6.1.2. Storage of quantities in the nodes: computation - direction of use 71

6.2. New post processing mode (menu compute FE quantities) 73 6.2.1. Necessity of a new menu: compute FE quantities 74 6.2.2. Computation a posteriori: principle 76 6.2.3. QUANTITY RESULT: definition (structure) 77 6.2.4. QUANTITY RESULT: creation, edition, deletion 78 6.2.5. QUANTITY RESULT: stored results post-processing 79

7. Computation of iron losses: principles 81 7.1. Computation of losses: general presentation 83

7.1.1. The losses in the electromechanical devices: general 84 7.1.2. The magnetic losses: general computation methods 86 7.1.3. Energy, instantaneous power, average power: reminder of definitions 88

7.2. Computation of the magnetic losses by means of the formulas of Bertotti 89 7.2.1. General expression of the magnetic losses: formulas of Bertotti 90 7.2.2. Computation of the losses in Steady state AC Magnetic applications (formulas) 91 7.2.3. Computation of the losses in Transient Magnetic applications (formulas) 93 7.2.4. Estimation of the coefficients of Bertotti 94 7.2.5. Analysis of the results: the post processable quantities 95

7.3. Computation of the magnetic losses with the LS model 97 7.3.1. General presentation of the LS model 98 7.3.2. The characterized materials (nuances of sheets) 100 7.3.3. Computation of the losses with the LS model 101 7.3.4. Analysis of the results: the post-processable quantities 102

PAGE D USER'S GUIDE


8. Computation of iron losses: software aspects 103 8.1. Iron losses: computation in 2D (FLUX 2D application) 105

8.1.1. Iron losses 2D (formulas of Bertotti): foreword 106 8.1.2. Iron losses 2D (formulas of Bertotti): computation – directions of use 107 8.1.3. Iron losses 2D (LS model): foreword 109 8.1.4. Iron losses 2D (LS models): computation – directions of use 110

8.2. Iron losses: computation in 3D (FLUX 3D application) 115 8.2.1. Iron losses 3D (formulas of Bertotti): foreword 116 8.2.2. Iron losses 3D (formulas of Bertotti): computation – directions of use 117 8.2.3. Iron losses 3D (LS model): foreword 120 8.2.4. Iron losses 3D (LS model): computation – directions of use 121

9. Skew slots: principles 123 9.1. Skew slots: general presentation 125

9.1.1. Interest in Skew slots 126 9.1.2. Skew slots modeling: 2D, 3D or 2½D ? 127

9.2. Skew slots: what FLUX models 129 9.2.1. Skew slots: presentation and typical example 130 9.2.2. Skew slots: principle of the method 131

9.3. Skew slots: description principle in FLUX 133 9.3.1. Boundaries of the study domain 134 9.3.2. Specifity of the module 135 9.3.3. Kinematic coupling 136 9.3.4. Circuit coupling 137

9.4. Skew slots: results analysis 139 9.4.1. Post-processing quantities: multilayers 2D method 140 9.4.2. Post-processing quantities: extruded method 3D 141

USER'S GUIDE PAGE E


PAGE F USER'S GUIDE

FLUX®9.10 Foreword

1. Foreword

Introduction This document describes the main new elements of the 9.10 version of FLUX.

This new version: • is part of the unification project of the FLUX 2D and FLUX 3D software. • and it is accompanied by a new, more modern, man/machine interface.

This foreword places version 9 within the FLUX project and presents the software-connected documentation associated to this version.

Contents This foreword covers the following topics:

• Version 9 and the 2D/3D unification project • The software documentation

USER'S GUIDE PAGE 1

Foreword FLUX®9.10

1.1. Version 9 and the 2D/3D unification project

Introduction The FLUX project comprises:

• on the one hand, the unification of the FLUX 2D and FLUX 3D software • on the other hand, the design of a new, more modern, interface

History …and perspectives

To place version 9 within the FLUX project, we present the main phases of this project in the table below:

Phase Description

Version 8 2D/3D unification of geometrical preprocessor Version 9 2D/3D unification of physical preprocessor Version 10 Carrying out of a modern interface for

the 3D solver and the 2D postprocessor Version 11 General unification of the 2D and 3D applications

Today … FLUX occurs in two main applications (Application 2D and Application 3D),

as can be seen from the table below.

FLUX 2D Application

FLUX 3D Application /

Skewed

Geometrical and physical preprocessor

(Preflux)

Interface Windows unified 2D/3D

Solver 2D

(SOLVER_2D) Interface Windows specific to 2D

Post Processor 2D

(POSTPRO_2D)

Solver 3D Post Processor 3D

(FLUX 3D)

Interface Non Windows specific to 3D

Ultimately, the 2D has been completely reconstructed: forgotten are now preflu, prophy, modpro, coppro, …

As to 3D, we must still wait for one more version in order to get both the solver and the postprocessor in the same package.

PAGE 2 USER'S GUIDE

FLUX®9.10 Foreword

1.2. The software documentation

Introduction The software documentation associated to version 9 is also included in the

2D/3D software unification project.

Contents This section covers the following topics:

• The software documentation: whatever is available so far • The user’s guide and the 2D/3D unification project • The user’s guide: the versions (on paper and on line) • The tutorials and the technical papers for the 2D applications • The tutorials and technical papers for the 3D applications

USER'S GUIDE PAGE 3

Foreword FLUX®9.10

1.2.1. The software documentation: whatever is available so far

Whatever is available so far

The software documentation comprises: • an installation guide • a user’s guide (which is the document you are reading now) • tutorials permitting an assisted initial implementation of the software for

various physical applications (magnetostatic, electrostatic, thermal, motor, linear drive).

• technical papers which provide support in the modeling of more complex devices, …

Where can these documents be found?

These documents are available (in pdf): • on your working post in the installation folder

C:\Cedrat\Doc_examples\Documentation\…

PAGE 4 USER'S GUIDE

FLUX®9.10 Foreword

1.2.2. The user’s guide and the 2D/3D unification project

Structure The user’s guide is included in the FLUX project.

It comprises: • a unified description of the part which is common to both 2D and 3D

applications • a separate description of the parts which are specific to the 2D and 3D

applications, respectively

The general structure of the user’s guide is presented in the table below.

FLUX (2D and 3D applications)

Volume 1 General tools

(FLUX environment) Geometry and meshing

Volume 2 Physical description, Cinematic coupling, Circuit coupling

Volume 3 The physical applications: Magnetic, Electric, Thermal, …

FLUX: Specificity

2D Applications FLUX: Specificity 3D Applications

Volume 4 Solve and Results General tools

(FLUX 3D environment) Solve and Results

Volume 5 Physical applications

(complements for advanced users)

USER'S GUIDE PAGE 5

Foreword FLUX®9.10

1.2.3. The user’s guide: the versions (on paper and on line)

Introduction The user’s guide appears in two versions:

• one version corresponding to the document on paper (or pdf) • one version corresponding to the online support

Why two versions?

The two versions of the user’s guide are not identical: • The document on paper comprises the necessary information in order to

understand well what can be carried out with FLUX (pre-requirement) • The online support includes the information mentioned above, to which the

necessary information is added in order to make good use of the proposed software.

In order to identify information easily …

For each of the important stages of a finite elements project, the information has been therefore split into two: • the ‘theoretical’ aspects (or principles) • the ‘practical’ aspects (or implemented at the level of the software)

These two aspects are dealt with in different chapters, as presented in the table below.

The chapters headed … comprise information of the type : …

Geometry: principles Meshing: principles Physical: principles …

• general information, reminders of physics • modeling principle (with FLUX) • software operation (its strengths and limits) • advice in view of modeling: strategy, choice,

… • general start, sequencing of operations

Geometry: software aspects Meshing: software aspects Physical: software aspects …

• structure of FLUX objects • manipulation of FLUX objects • description of commands for specific actions

Concretely … The contents of the two versions of the user’s guide is presented in the table

below.

Document on paper Online support The theoretical aspects: Chapters headed: « … : principles »

The theoretical aspects: Chapters headed: « … : principles »

The practical aspects: Chapters headed: « … : software aspects »

PAGE 6 USER'S GUIDE

FLUX®9.10 Foreword

1.2.4. The tutorials and the technical papers for the 2D applications

Definition A tutorial has the objective to show how to use the software by means of a

simple example. This type of document is useful for self formation as regards the software. All the commands are described.

A technical paper has the objective to demonstrate the features of the software on a realistic technical example (emphasizing the interesting results which can thus be obtained). All the technical data are presented in the document, but the commands are not described in details.

Tutorials (2D) The available tutorials for the 2D applications are listed in the table below.

Tutorial: Application 2D Magneto Static Electro Static Thermal Permanent and Transient

Basic applications

Blushless Permanent Magnet Motor

Translating Motion

Magnetic applications with: Cinematic coupling Circuit coupling

Induction Heating Application Magneto thermal

Technical papers (2D)

The technical papers available for the 2D applications are listed in the table below.

Technical paper: 2D Application Scalar command of a machine (FLUX to Simulink Technology) Single phase and three phase transformer Superconductors (FLUX 2D version 7.60)

USER'S GUIDE PAGE 7

Foreword FLUX®9.10

1.2.5. The tutorials and technical papers for the 3D applications

Definition The objective of a tutorial is to show how to utilize the software by means of

a simple example. This type of document is useful for self formation as regards the software. All the commands are described.

A technical paper is meant to show the software features on a realistic technical example (emphasizing the interesting results which can thus be obtained). All the technical data are presented in the document, but the commands are not described in details.

Tutorials (3D) The available tutorials for the 3D applications are listed in the table below.

Tutorial: Application 3D Magneto Static Basic applications

Translating Motion Magnetic applications with: Cinematic coupling Circuit coupling

Technical papers (3D)

The technical papers available for the 3D applications are listed in the table below.

Technical paper: 3D Application Varying studies and rotating motion Rear-view mirror motor analysis with FLUX 3D End Windings characterization with FLUX 3D Permanent magnet machine Magneto Thermal Non Destructive Testing with FLUX 3D Application

PAGE 8 USER'S GUIDE

FLUX® 9.10 Introduction to the novelties of FLUX version 9.10

2. Introduction to the novelties of FLUX version 9.10

Introduction This chapter presents the novelties of FLUX version 9.10.

It lists the main novelties and provides the references of the chapters in which the information is detailed.

Contents This chapter covers the following topics:

• The new FLUX preprocessor • Other novelties

USER'S GUIDE PAGE 9

Introduction to the novelties of FLUX version 9.10 FLUX® 9.10

PAGE 10 USER'S GUIDE


2.1. The new FLUX preprocessor

Introduction The main novelties of version 9.10 refer to the preprocessor of FLUX.

Indeed, this new version: • accomplishes the unification, at the level of the physical description, of the

FLUX 2D and FLUX 3D software • is accompanied by a still more improved interface


• FLUX environment and management of data • Import of geometry/mesh and correction tools • Description of the physical properties

USER'S GUIDE PAGE 11


2.1.1. FLUX environment and management of data

Introduction Important modifications have been introduced to the FLUX environment

from version 8.10 to version 9.10.

Where to find the information?

These novelties are presented in this section and they are detailed in chapter 3 concerning the ‘Working environment and data management’.

Working environment

As to the working environment, the modifications have been operated at the level of the general presentation: windows, toolbars, …

As to the general functioning, from now on the user has access to the assembly of entities independent of the context via: • the data tree • the Geometry, Mesh, Physics menus.

The choice of a context gives access to the icon bars specific to that context.

Data management

As to the basic operations of handling the entities, certain additions have been brought about.

From now on it is possible to: • create entities in an indirect manner (in flight) • edit a group of entities in a table (and carry out a ‘grouped’ modification)



2.1.2. Import of geometry/mesh and correction tools

Coupling with the CAD

The coupling with the CAD is significantly improved. From now on it is possible to import the geometry under various formats (Step, Iges, Dxf) while having automatic correction tools of the geometrical defects.

Furthermore, the meshing of the complex geometries (uneven surfaces imported from the CAD) is from now on possible.


These novelties are presented: • for the theoretical aspects in this document, see chapter 4 “Import of

geometry/mesh: principles” • for the practical aspects in the on-line help, see chapter “Import of

geometry/mesh: software aspects”.



2.1.3. Description of the physical properties

Introduction The main novelty of version 9.10 concerns the physical preprocessor.

Indeed, for this version, the physical preprocessor is integrated in the new FLUX environment; and at the same time there is a fusion of description mode of the physical properties between the applications 2D and 3D.


The main information concerning the physical preprocessor is grouped in the documents presented in the table below.

In the document … read the chapter(s) on …

The novelties (V9.10) Novelties of the physical preprocessor (Chapter 5)

User’s Guide (volume 2*)

The description of the physical properties in FLUX (Mainly Chapter 1, and possibly 2, 3, 4 and 5)

User’s Guide (volume 3*)

The physical applications available in FLUX (Assembly of all the chapters of this volume)

*Attention, these documents comprise only the chapters pertaining to the theoretical aspects (or principles)

For the ‘practical’ aspects (or carried out at the level of the software), refer to: the on-line help (which will be updated with the following patches)



2.2. Other novelties

Introduction The other novelties are briefly presented in this section.

For more information on these novelties please refer to the appropriate chapters (see the following blocks).

Computation of iron losses

The computation of magnetic losses (or iron losses) a posteriori is proposed from now at the level of the 3D postprocessor. To carry out this computation two methods are proposed: • the computation of the iron losses starting from the formulas of Bertotti • the computation of the iron losses with the LS (Loss Surface) model

These novelties are detailed (for the applications 2D and 3D) in the following chapters: • Chap 7: “Computation of the iron losses: principles” • Chap 8: “Computation of the iron losses: software aspects”

A new menu in 3D (Results)

New computations are proposed in FLUX Application 3D at the level of the postprocessor (result module), such as the computation of the magnetic losses (or iron losses), …

The a posteriori computations, integrally carried out in the result module, require the storage of an assembly of results of different types (values, curves, … ). Consequently, a new menu, for the carrying out and the management of these computations (compute FE quantities), is brought in FLUX.

The user will equally be able (by means of this menu) to carry out the storage of the physical quantities to the nodes.

These novelties are detailed in chapter 6 “Novelties of the 3D postprocessor”.

Continued on next page



Skew slots A new FLUX module (midway between the 2D and the 3D) is proposed for

the modeling of the rotating machines with skew slots.

This module (named Skew slots or) permits: • The modeling of the machines which comprise a rotor or a stator with skew

slots • Starting from a 2D description of this machine

The interestingness of this module is the facility of carrying out a quasi 3D or a 2 ½ D study on the basis of a 2D description. The post-processing of the results is carried out with the 3D postprocessor.

These novelties are detailed in chapter 9 “Skew slots: principles”

Coupling with Simulink

Variable time step in the coupling between FLUX and SIMULINK (not detailed in this document)


FLUX® 9.10 Working environment and data management

3. Working environment and data management

Introduction This chapter presents new features concerning:

• on the one hand, the working environment • on the other hand, the data management

Content This chapter contains the following topics:

• Working environment and graphic representation • Data management


Working environment and data management FLUX® 9.10



3.1. Working environment and graphic representation

Introduction This section concerns the working environment i.e.:

• the description and role of different zones presented in the FLUX window • the customization possibilities proposed to the user

Content This section contains the following topics:

• Presentation of working environment • Modifying the environment • Graphic



3.1.1. Presentation of working environment

FLUX window The general FLUX window consists of several zones. These different zones

are identified in the figure below.

Title bar

Menus bar

Data tree

Graphic scene

toolbars

Status bar

Context bar

Graphic scene

History

Menus toolbars

Configuration of the window

Preflux desktop is automatically depends of: • Dimension of the application (2D or 3D) • The physical application defined (no physic defined, magneto static,

electrostatic, …) • The context : Geometry, Mesh or Physics • Or sub context (sub context for healing the geometry…)




Role of zones The different zones and their principal roles are briefly described below:

Element Function Title bar General information:

• Software name and version number • Application (2D Steady Thermal) • Name of the current project

Menu bar Access to the different menus: • Project, Application, View, Display,

Select • Geometry, Mesh, Physic, Tools,

Help Context bar

Access to the toolbar corresponding to the contexts: • Geometry, Mesh, Physic

Menus Toolbars Project

Commands of Project menu: • New, Open…, Save, Close, Exit

Tools

Commands of Tools menu: • Undo

Contexts toolbars: Geometry Context Commands of Geometry context:

• Creation of the geometric entities

• Propagate / Extrude Line, Face …

• Build Faces, Volumes, Assign

Regions

• Measure geometry (distance between

two points …)

• Check of the geometry Mesh Context Commands of Mesh context:

• Creation of mesh entities • Actions on the mesh • Check of the mesh

Physic Context Commands of Physic context:

• Creation of physic entities

• Actions on the physic • Check of the physic




Menus Toolbars (in the graphic scene): View Commands of the View menu:

• Refresh view, Zoom all, Zoom region

• Standard 1 view, Standard 2 view, Opposite

view, Direction of view, View on X, View on Y, View on Z, Four views mode

Display Commands of the Display menu: General

• Display of coordinate systems, points, lines, faces, volumes, surface regions, volume regions

in the Geometry context

• Display of surface elements, points numbers,

lines numbers in the Mesh context

• Display of mesh points, mesh lines, nodes,

surface elements in the Physic context

• Display of non meshed coils

Selection Commands of the Select menu:

• Activate the selection filter, Select points, Select lines, Select faces, Select volumes, Select surface regions, Select volume regions




Role of zones (continued)

Element Function Entities tree

Entities tree of the FLUX project

History

Information concerning different current actions (project evolution): • Restoring of data during a project

opening, • Comments about the current

actions, • Advance of computation during the

solving process, … Zone Command (masked)*

Command echo

Command

Access to functioning mode by commands in Python language.

*This zone is masked. To display this zone, see § « Modifying the environment ».



3.1.2. Modifying the environment

Modify the background color

To modify the background color (reverse video): • In the View menu, click on Reverse video

Display/ mask zones

To display / mask zones: • Use the arrows located on the zones sides (see example in the block below)

Display the Python command zone

The zone for the commands in Python language is masked (by default). To display this zone: • Click on the arrow located on the bottom of the history zone as shown in

the figure below.

Arrow to display the Python command zone

⇒



3.1.3. Graphics

Modes of rotation

Preflux3D 9.1 offers to users three modes for rotating geometries with left button of the mouse (two modes with the 8.1 version). User can see the active mode thanks the different cursors.

Mode for 3D rotation Mode activation Cursor

2D planar rotation around the center of the view.

Left button of the mouse Mouse far away from the center of the view

3D rotation around the center of the object

Left button of the mouse Mouse close from the center of the view

3D rotation around the point defined by mouse cursor

Left button of the mouse Shift button pushed





3.2. Data management

Introduction The building of a FLUX project consists in the handling of the entities.

The basic operations for handling the entities are: • on the one hand the creating, editing (modifying) and deletion operation • on the other hand the selection operation

New features on this subject are presented in this section.

Contents This section contains the following topics:

• Entities handling: “indirect” creation • Entities handling: array editing



3.2.1. Entities handling: “indirect” creation

“Indirect” creation

The 9.10 allows the “indirect” creation of entities. What is it?

In most of description process (geometric, physical, … description), it is necessary to respect a certain order in entities creation: points before lines, materials before regions, …

Now, if the logical order of entities creation is not respected, and if some entities are forgotten, it is possible to create these entities in an indirect way as shown on the example below.

The example below shows the process of an indirect material creation at the moment of volume region creation.

4. Enter B(H) properties of the material

3. Enter a name and a comment

1. Click on the arrow

2. Click on New

5. Click on OKThe material becomes available in the list of materials



3.2.2. Entities handling: array editing

Presentation FLUX version 9.10 offers a new editing mode for entities. This is the edition

of a group of entities in a table.

Example (figure below): Edition in a table of a group of geometric parameters.

Entities table With this new editing mode, information relative to an assembly of entities

(notion of group) is displayed in a table.

1 2 3

Entities Modify all Entity n°1 … Entity n°i …Entity Type Nom Name_1 Name_i Comment Comment_1 Comment_i Type Characteristics Initials values Char_1 Char_i …

The role of different zones is presented in the table below.

Column Function

1 Outline the structure of the Entity Type (group) 2 Concern data relatives to the group

Allow modification of all values (for the group) 3 Concern data relatives to the entities (group)

Allow modification of one particular value

Interest With this new editing mode, it is possible:

• to quickly check set of data (for an entities group) and to correct values if necessary

• to give the same value (for a characteristic) to all the entities (of a group); i. e. to modify, in one step, all values located on the same line




Modify in a table

To modify a particular value in a table: • position the cursor on the wanted area (column 3) • replace the display value by the wanted value

To give the same value to all the entities of the group: • position the cursor on the wanted area (column 2) • replace Initials values by the common wanted value


FLUX® 9.10 Geometry/mesh importation: principles

4. Geometry/mesh importation: principles

Introduction This chapter presents:

• on the one hand, the different possibilities of geometry/mesh importation with FLUX and the general options for conversion

• on the other hand, the principle of importation (importation of geometry starting from geometrical files or importation of geometry starting from mesh files)

Contents This chapter contains the following topics:

• Geometry/mesh importation: overview • Geometry importation (IGES, STEP, DXF, STL, FBD, INTER formats) • Mesh importation (NASTRAN, PATRAN, UNV Ideas formats)


Geometry/mesh importation: principles FLUX® 9.10



4.1. Geometry/mesh importation: overview

Introduction This section presents a general point of view concerning the authorized

formats for importation and the principle of conversion.


• Importation formats • Principle of conversion and options for conversion



4.1.1. Importation formats

Authorized formats

The authorized formats for importation can be divided in two categories: • geometry importation:

- in standard format: IGES, STEP, DXF, STL - in proper format: FBD, IF3 (INTER)

• mesh importation: - in standard format: NASTRAN, PATRAN, UNV

Importation formats

The various formats of geometrical files accepted by FLUX are gathered in the table below.

File format Extensions

IGES (Initial Graphics Exchange Specification) *.IGES, *.IGS STEP (Standard for Exchange of Product) *.STEP, *.STP DXF (Draw eXchange File) *.DXF STL (STereo Lithography) *.STL FBD (FLUX2D geometry) *.FBD INTER (IGES for FLUX3D) *.IF3

The various formats of mesh files accepted by FLUX are gathered in the table below.

File format Extensions

NASTRAN neutral *.NAS, *.DAT PATRAN neutral *.PAN, *.DAT UNV (UNiVersel Ideas Master Serie) *.UNV

Type of accepted file

For importation FLUX accepts only files in text format. The binary files are not accepted.

Attention: It is not possible to import the assembly file of several IGS files (*_ASM.IGS).

Multiple importation

Multiple importation is available. FLUX is able to import the files with different formats (DXF, STL, etc) in the same project.



4.1.2. Principle of conversion and options for conversion

Principle of conversion

Importation is an operation that convert the initial file entities into FLUX entities (geometric entities of Point, Line, … type).

Options for conversion

To perform the data conversion, different options are proposed to the user.

These options are of two types: • general options, available for all formats • particular options, specific to the format

Only the general options are described in this section.

General options for conversion

The general options for conversion available for all formats are following: • choice of a coordinate system: to place the imported geometry in the FLUX

project • choice of the unit: to choose the units of the device dimensions • choice of precision: to define the minimal distance enabling to distinguish

two points

These options are detailed in the following blocks.

Coordinate system

At the moment of importation, a coordinate system is created in the FLUX project with the name XXXi (where XXX = extension corresponding to the imported format). This coordinate system coincides with the principal coordinate system XYZ1. Then the user can displace the device (for example, with respect to the infinite box, etc.) by modifying the position of the imported coordinate system.

At the moment of importation, the user can position the device in one of the following coordinate systems: • the proper coordinate system of the device: XXXi • a predefined coordinate system : XYZ1, Z_ON_OX, Z_ON_OY • an user coordinate system: …




Length unit The device is described in proper units in the initial file, but the information

about the length unit is not present in this file.

At the moment of importation, the user can choose a length unit as follows: • by default: meter • another possibility: meter * conversion factor

The conversion factor is the ratio between the length unit chosen by the user and the FLUX length unit, which is the meter.

Examples of conversion are presented in the table below.

If the entities in the initial file are in …

and the conversion factor is equal with …

the unit in the FLUX project is …

Meter 1 Meter Millimeter 0.001 Millimeter

Micron (micrometer) 10-6 Micron

Caution: The length unit previously chosen is automatically assigned to the imported coordinate system XXXi.

If the device is imported in another coordinate system, the user must assure that the length unit of this coordinate system is compatible with the importation length unit.

Precision The absolute precision is the minimum distance between two points of the

geometry (or between two nodes of the mesh) from which the two points (or the two nodes) of the initial file are represented by only one point in the FLUX project.

Absolute precision

Initial file:distance between 2 points (or nodes)

FLUX file:1 point

The absolute precision is: • either imposed by the user • or automatically computed by FLUX (automatic precision)




Automatic precision

The automatic precision, quantity automatically computed by FLUX, is obtained by means of the following formula: Absolute precision = Relative precision * Diagonal where: • Relative precision, also called relative epsilon, is a coefficient independent

of the length unit, fixed to 10-5 for the importation • Diagonal is the distance between two faraway points of the box

surrounding the device (see the figure below)

3D geometry 2D geometry





4.2. Geometry importation (IGES, STEP, DXF, STL, FBD, INTER formats)

Introduction This section deals with the importation of geometry starting from geometrical

files.

The formats which enable the geometry importation are following: • standard formats:

- Initial Graphics Exchange Specification (extensions: *.IGES, *.IGS) - Standard for Exchange of Product (extensions: *.STEP, *.STP) - Draw eXchange File (extension: *.DXF) - STereo Lithography (extension: *.STL)

• proper formats - FLUX2D geometry (extension: *.FBD) - IGES for FLUX3D (extension: *.IF3)

Interest of FLUX for IGES / STEP formats

The geometry importation from a file in IGES / STEP standard format enables the consideration by the FLUX projects of complex geometries with uneven surfaces.

These surfaces cannot be directly built with the FLUX tools.


• Process of geometry importation • Stage of conversion • Stage of geometry checking: concept of geometric fault • Stage of geometric faults correction / geometry simplification • Geometry importation: strategies



4.2.1. Process of geometry importation

Introduction The importation of a geometry from a file is an operation that consists in

converting the geometry of the initial file (specific to the format) into FLUX entities (geometric entities of Point, Line, …type).

Question It is important to note that in FLUX, the user should build the geometry

without faults. A fault, in the FLUX sense, is an error of the geometrical construction of intersection of lines type, of superposition of points type, etc.

If there are geometrical faults in the origin file (intersection of lines, superimposed points, etc.), these can hinder and also block the process of geometry building: impossibility of building faces and/or volumes.

So, after the geometry importation, it is necessary that complementary actions should be taken in order to search (identify) and correct the geometric faults.

Importation process

The process of importation is a process involving the three stages briefly describing in the table below and detailed in the following paragraphs.

Stage Description

1 Conversion 2 Geometry checking / search geometric faults 3 Correction of geometric faults

and/or geometry simplification



4.2.2. Stage of conversion

Introduction The first stage of importation is a stage of conversion of the imported

geometry into the FLUX format.

Operation principle

The principle of operation of the importation is following: all the geometric entities of the initial file (specific to the standard and proper formats) are converted into the FLUX format (geometric entities of type Point, Line...) in the final file.

Conversion of entities

The entities of the initial file are read and converted into the FLUX entities. The summary table is presented below.

The file in the format

…

contains entities CAD

… which are converted into FLUX entities …

points points defined by parameterized coordinates lines lines of type:

• segment defined by extremity points • arc defined by origin, intermediary and

extremity points • curve (for the unspecified lines)

IGES / STEP

faces faces of type: • automatically defined by plane, cylindrical

or conical surfaces • uneven type, defined by any kind of

surfaces POINT points defined by parameterized coordinates LINE lines of segment type defined by extremity

points POLYLINE N lines of segment type ARC, CIRCLE

lines of arc type defined by origin, intermediary and extremity points

DXF

3DFACE faces of automatic type, with triangular shape, defined by a plane surface

VERTEX points defined by parameterized coordinates STL FACET faces of automatic type, with triangular shape,

defined by a plane surface




Conversion of entities (continued)


…

contains entities CAD

… which are converted into FLUX entities …

points points defined by parameterized coordinates lines lines of type


extremity points faces automatic faces geometric parameters

geometric parameters

FBD

regions regions points points defined by parameterized coordinates

IF3 lines lines of type:


extremity points



4.2.3. Stage of geometry checking: concept of geometric fault

Introduction The second stage is the geometry checking.

This stage is the stage of a research (identification) of the geometric faults; as to the correction, this will be carried out in the following stage (stage 3).

Before describing the modes of faults search, the different fault types are described in the following blocks.

Geometric faults

The geometric faults can hinder or block the geometry building process.

The following can be therefore discerned: • blocking faults (intersections and superpositions):

these faults must be identified and corrected before building the geometry in FLUX.

• non-blocking faults (very small lines and faces, wires not closed, …): these faults do not impede the geometry building in FLUX, but they can influence in a negative manner the quality of the geometry building and/or the meshing

The geometric faults are presented in the table below.

Fault Example (or type) Consequence

blocking

• intersection of type: - line/line - line/face - face/face*

• superposition of type: - point/point (confused points) - line/line (superimposed lines)

building of the faces and volumes impossible

• entities of small dimensions: - small line (line shorter than …) - small face (face shorter than …)

difficulties of meshing

• open wire missing face non-blocking

• superposition of type: - point/line (point on a line) - point/face (point on a face)

entities not used in the building of geometry

*In the next figure, the faces building after the importation of the geometry will generate the intersection of the faces. This type of fault is not identified by FLUX in the Geometric Fault entity, but it is blocking for the further volumes building. The connecting the points P1 and P2 by a new line before the faces building enables to avoid the intersection of the faces.

P1 P2




Faults research modes

The research of the geometric faults can be carried out in two ways: • by type of fault (described as research by type) • for the assembly of types of faults (described as global checking of the

geometry)

Research result Whatever the research mode, the result is the following:

• FLUX creates a geometric entity of the Geometric fault type for each fault found (this entity contains the information about the fault localization: number of concerned points, lines or faces)

• FLUX highlights this entity in a graphic window (specific display)



4.2.4. Stage of geometric faults correction / geometry simplification

Introduction The third stage is the stage of correction of geometric faults and/or geometry

simplification.

Correction principle

The principle of correction proposed by FLUX for the various types of geometric faults is presented in the tables below.

Fault of the superposition type Principle of correction

Confused points ⇒ Suppression of a point Superimposed lines

P2

P4 P3

⇒

Cutting of the lines

L2 P4 P3

P1 P2

L1 L1 L3

P1

L2

Fault of the intersection type Principle of correction Intersection of two lines

P4

P3

L1

P1

L2

P2

⇒

Cutting of the lines

L12 L11

L22

L21

P4

P1

P2

P3

P5

Intersection of a line and a face ⇒ Correction is to be made by the user

Fault of the type Principle of correction Line shorter than ...

(value fixed by the user) L2 L1

L1

L2

⇒

Removal of the L2 line by fusion of the lines L1 and L2

L1

L1

Face shorter than ...

(value fixed by the user) F1L1

L2

⇒

Removal of the F1 face by confusion of the lines L1 and L2

L1




Fault of the type Principle of correction

Open wire P2 P1 L1

⇒

Closing of contour by prolongation of the L1 line

P1 L2

L2 L1

Fault of the type Principle of correction Point on a line

P3 P1

L1

P2

⇒

Suppression of the point

P3 P1

L1

Point on a face

F1 P1

⇒

Suppression of the point

F1

Simplification principle

The principle of simplification proposed by FLUX consists to remove some lines and points and thus “to reduce” the geometry. Simplification is expected only for the lines of the segment type and arc of circle type.

The principle of simplification is presented in the table below.

Geometry of type Principle of simplification

Segments located on the tangent of the straight lines

P4P3 P1 P2 L3L1 L2

⇒

Removal of the lines L2 and L3 and suppression of the points P2 and P3 by fusion of the lines L1, L2 and L3

P4P1 L1

Arc of circle having the same curve angle

L1 P2 P1

P3 P4

Removal of the lines L2 and L3 and suppression of the points P2 and P3 by fusion of the lines L1, L2 and L3

P1 P4

L1

L2 L3




Algorithms of automatic correction / automatic simplification

To facilitate the process of correction, the algorithms of automatic correction / automatic simplification are proposed. They are presented in the table below.

The algorithm of … enables the correction …

automatic correction of all blocking faults (superpositions and intersections)

automatic simplification of all faults of type: lines shorter than …

Note: These algorithms are planned especially for the 2D geometry, the result in 3D is not guaranteed.

Manual correction

To correct the other faults the user must carry out a manual correction with the tools presented in the table below. The use of these various commands is detailed in section “Correction of geometric faults” of chapter “Geometry/mesh importation: software aspects”.

To correct the faults

of type ... the user should ...

Intersection of lines Superposition of lines

Cut line on a point Cut line on intersection

Line shorter than … Fuse lines

Face shorter than … Confuse lines

Open wire Extend line to point Extend line to line



4.2.5. Geometry importation: strategies

Introduction Although it is possible and necessary to correct the geometric faults after

importation, it is preferable to prepare the initial file so that the operations of correction in FLUX are minima.

The checking of the geometry and the correction of possible geometric faults are essential.

Prepare the initial file

To prepare the initial file in general way: • define the points, lines, faces, … by respecting the characteristics of the

FLUX geometry building module • remove the intersections of lines, lines and faces, the superpositions of

faces, … The characteristics of geometry building module (description: the authorized shapes of faces and volumes, prohibited intersections and superpositions, …) are given in chapter “Geometry: principles”.

Constraints of FLUX software

It is not possible to perform the following operations in an imported geometry (containing lines of list edges type and faces of list facets type): • modify the imported faces/lines • propagate/extrude the imported faces/lines • mesh the faces/volumes using mapped mesh generator

Capabilities of FLUX software

It is possible to perform the following operations in an imported geometry: • build the faces/volumes • mesh the faces/volumes using automatic mesh generator



4.3. Mesh importation (NASTRAN, PATRAN, UNV Ideas formats)

Introduction This section deals with the importation of geometry starting from mesh files,

named the mesh importation.

The standard formats which enable the mesh importation are following: • UNiVersel Ideas Master Serie (extension: *.UNV) • NASTRAN neutral (extensions: *.NAS / *.DAT) • PATRAN neutral (extension: *.PAN / *.DAT)

Interest The importation of a geometry starting from mesh file enables the

consideration by the FLUX projects of complexes geometries with uneven surfaces.

These surfaces cannot be directly built with the FLUX tools.


• Process of mesh importation • Stage of conversion • Stage of fusion • Stage of positioning • Mesh importation: strategies



4.3.1. Process of mesh importation

Introduction The importation of a geometry starting from mesh file is an operation which

enables the building of the device geometry based on mesh information of an initial file. This approach enables the introduction in FLUX projects of uneven surfaces in the form of “cut surfaces”, but has the disadvantage of generating an important number of geometric entities (volumes, faces, lines). As consequence, the result of the mesh file conversion is not always compatible with the requirements of FLUX analysis (for example, the use of sliding cylinder, …).

At the moment of mesh importation (or right afterwards) additional operations are necessary, in order to simplify and adjust the imported data.

Importation process

The mesh importation process involves three stages, briefly described in the table below and detailed in the next paragraphs.

Stage Description

1 Conversion 2 Fusion of the multiples faces and lines coming from the mesh

importation (facets and edges) 3 Positioning of the faces on a reference plan/cylinder



4.3.2. Stage of conversion

Introduction The first stage is a stage of conversion of the mesh entities into geometric

entities.

Volume element: reminder

In FLUX, a volume element of the mesh is characterized by vertexes, edges and facets, as shown in the next figure

side

edge

vertex

Principle of conversion

The principle of conversion shown in the scheme below is the following: all the vertexes, edges and facets of volume elements of initial file are converted into points, lines and faces in the final file.

Importation in FLUX

1 square face meshed with 6 elements

i l i

6 faces, 12 lines, 7 points

The group concept, regrouping volume elements having the same material in the initial file, enables the creation of volumes in the FLUX project.

Conversion of entities

The entities of the initial file are read and converted into FLUX entities, as presented in the table below.


…

contains entities CAD …

which are converted into FLUX entities …

nodes points defined by parameterized coordinates

line elements lines of edges list type face elements faces of facets list type

NASTRAN / PATRAN

/ UNV groups: component or material

volumes

Structure of data

In FLUX, the geometric entities resulting from the mesh importation differ from “standard” geometric entities: • the faces resulting from mesh importation are faces of facets list type • the lines resulting from mesh importation are lines of edges list type



4.3.3. Stage of fusion

Introduction Following the importation, the geometry of the imported device has multiple

lines and faces deriving from multiple facets and edges of the initial file.

The second stage is the stage of fusion (regrouping of the entities), which enables the reduction of number of lines and faces, and facilitates their handling, as well as the visualization of the device.

Fusion of faces: use

Although strongly advised, the fusion of faces/lines is optional. This operation becomes compulsory for the faces in the cases presented below.

If … The fusion …

kinematic coupling of dissociation faces (sliding cylinder, boundary of mobile mechanical set and compressible mechanical set)

symmetry and/or periodicity planes of faces located on these planes

… is compulsory

Concept of fusion

We call fusion of faces/lines the operation of regrouping faces/lines to form the main faces/lines of the device geometry.

Principle of fusion of faces and data structure

The principle of fusion of faces is shown on the scheme below. During fusion all faces belonging to the same surface are regrouped in one face.

Fusion

Set of faces that resultsfrom facets of the initial

file

A single face thatcontains many

facets

The faces resulting from mesh importation are faces defined by a list of facets. • Before the fusion of faces:

every face (of facets list type) contains a single facet • After the fusion of faces:

every face (of facets list type) contains many facets




Regrouping surface and angle of fusion

The surface of regrouping is defined by the user, using an angle named angle of fusion. All adjacent faces whose angle is less than the fusion angle are regrouped in a single face (See figure of example below).

Example : Three adjacent faces are regrouped in a single face with a fusion angle α

Angle [ ]α;0°∈

Angle [ ]α;0°∈

The regrouping surfaces can be of different shapes (plane, cylindrical, …) and depend on the chosen value of fusion angle as follows: • for an angle of small value (between 0 and 1°), the regrouping surface is a

planar surface • for a larger angle, the regrouping surface can be of any shape

Precaution So that the simplified geometry approaches with more real geometry, it is

necessary to take some care as for the choices of an angle of fusion, the risk being to gather faces, which should remain separate.

In general, it is advised to comply with the following rule: • start with an angle that is inferior or equal to 1° - to identify the plane faces • gradually increase the value of the angle - to identify the others faces

Attention The fusion process does not create even surfaces. The regrouping surface is

an uneven surface, although this surface looks like an even one.

And for the lines …

The principle of lines fusion is the same with the one of faces fusion. It is illustrated in figure below.

Fusion

Set of lines that resultsfrom edges of the initial

file

A line thatcontains many

edges




Rules of fusion Two faces (lines) can be regrouped if they belong to same volumes (faces).

The mesh importation of a quarter cylinder before and after the fusion of faces and lines is shown in figure below.

Geometry created in FLUX starting from an imported mesh

Geometry in FLUX after fusion of faces and lines



4.3.4. Stage of positioning

Introduction After importation of mesh and simplification of geometry, the quality of the

faces obtained starting from mesh data can be unsatisfactory for the FLUX further operations (see examples below). In this case, it is necessary to adjust the geometry.

Examples: • If we want to impose the condition of periodicity on two faces which

theoretically form an angle of 60°, but in reality the imported faces form an angle of 59.9999°, it is necessary to adjust the geometry in such way that the real angle between the two faces to be 60°.

• If we want to use the sliding cylinder entity and if the face corresponding to the surface of dissociation not be really carried by a cylindrical surface, it will then be necessary to adapt the consequently geometry.

Positioning of faces: use

The positioning of the faces is optional but becomes compulsory for the faces in the following cases:

If … the positioning …

kinematics coupling of dissociation faces (sliding cylinder, boundary of mobile mechanical set and of compressible mechanical set)

Symmetry and/or periodicity planes of faces located on these planes

… is compulsory

Concept of positioning

We call positioning of a face on a plan or on a cylinder the operation that consists in projecting the face on a reference plan or cylinder, defined by the user.

The positioning is not intended to orient differently the plans with respect to imported geometry, but to homogenize this geometry in order to ensure a good FLUX further operation.

Principle of positioning

The positioning of a face F on a surface S means the projection of points, nodes of F on S, the edges follow the movement. Thus, the use of positioning of faces by their displacement with many degrees with respect to the initial geometry can results in a geometry deformation.

Many successive displacements can emphasize the deformation of the geometry even if we return to an arrangement conform to the imported geometry.



4.3.5. Mesh importation: strategies

Strategies of mesh importation

Previous to mesh data importation is important to choose a strategy for the importation. It is possible: • to import a complete geometry of the device, i.e. all its components, the

including box and the complete mesh of the study domain • to import the geometry and the mesh of a only one component or of a part

of the device and to complete the description of geometry and mesh in FLUX.

The further steps of the project depends on the chosen strategy.

Strategy 1 The first strategy consists in importing the whole study domain. The process

of importation can be presented as follows:

Stage Description 1 Preparation of initial file in the origin software:

• full description of the device geometry • addition of an air region or of a box including the device • meshing of study domain

2 Data importation into FLUX by using the option: • with mesh (mesh data importation)

3 Simplification of file: • fusion of faces/lines

4 Direct passage to physics

Strategy 2 The second strategy consists in importing a specific meshed part of the

device. The process of importation can be presented as follows:

Stage Description 1 Preparation of initial file in the origin software CAD (ex. rotor):

• description of the geometry of the device part • mesh of this part

2 Data importation into FLUX by using the option • without mesh

3 Simplification and adjustment of file: • fusion of faces/lines • positioning of faces

4 Building in FLUX of the rest of the device geometry (ex. stator) : • geometrical construction of other device parts • construction of faces and volumes • mesh of the whole computation domain

5 Direct passage to physics

Important: The device parts, added by FLUX, do not have to touch the imported geometry (imported parts).




Constraints of FLUX software

It is not possible to perform the following operations in an imported geometry containing lines of list edges type and faces of list facets type: • modify the imported faces/lines • propagate/extrude the imported faces/lines • modify the mesh of imported objects; the initial mesh is entirely preserved

Capabilities of FLUX software

It is possible to perform the following operations in an imported geometry: • build the faces/volumes • mesh the faces/volumes using automatic mesh generator

Preparation of initial file

During the preparation of the initial file: • you must verify if the mesh is non-conform (ex: the addition of two parts

separately meshed is forbidden) • when the periodicity is present, you should perform an identical mesh on

the faces concerning the periodicity

Attention: A non-conform mesh in the initial file may generate intersections that cannot be removed.




FLUX® 9.10 News of physical preprocessor

5. News of physical preprocessor

Introduction This chapter refers to news of physical preprocessor.


• List of principal new features • Advices for 2D users

Reading advice The general information concerning the physical preprocessor is detailed in

the following documents: • Volume 2*:

Physical description, Circuit coupling, Kinematic coupling • Volume 3*:

The physical applications: Magnetic, Electric, Thermal

*Attention, these documents comprise only the chapters pertaining to the theoretical aspects (or principles) For the ‘practical’ aspects (or carried out at the level of the software), refer to the on-line help (which will be updated with the following patches)


News of physical preprocessor FLUX® 9.10



5.1. List of principal new features

Introduction This section gives the list of principal new features of physical preprocessor.


• Physical description • Physical applications: magnetic, electric, thermal • Materials databases



5.1.1. Physical description

Boundaries conditions

Boundaries conditions are handled by the intermediate of: • periodicity • symmetry • regions

- line regions (or point) in 2D - face regions (or line) in 3D

In 3D, surface constraints are suppressed.

Import of materials

In a FLUX project, the user can, from now on, import materials from several materials database.

With the command Import Material, 3 banks are proposed. These banks are those located on the following directories: “shared”/ “local” / “current directory” (cf. § Materials databases)

To import a material: • In the Physics menu, point on Material and click on Import Material

Materials orientation

To orient materials: • In the Physics menu, point on Material and click on Orient Material for

face (or volume) regions



5.1.2. Physical applications: magnetic, electric, thermal

Magnetic applications (general)

A new model for magnet is put forward: non linear magnet spline with transversal mu

Magnetic applications (3D)

For FLUX 3D user’s: • inductors are suppressed and replaced by the electric component Coil

Conductor • a new mode for the description of composed coils is proposed • coils of dipole type are suppressed and replaced by a new type of source of

magnetic field Magnetic field created by a magnetic dipole

Electric applications

A new type of region is proposed for perfect conductors modeling (in Electro Static and Steady state AC Electric): Perfect conductor

Thermal applications

The physical description could be done with a user temperature unit (ex: Celcius degree).



5.1.3. Materials databases

News FLUX allows the use of several material databases. In a FLUX project, the

user can, from now on, import materials from several materials database.

The material databases

From the user’s point of view, it is possible to distinguish: • external databases:

this is those supplied with the software (CEDRAT, IMPHY, …) • internal databases :

this is those created by the user

Location Depending on their use, databases could be placed at different location as

presented in the table below.

Database Location Name

external Installation directory: C:\Cedrat\Materials

FLUX_910_MATERI.DAT IMPHY_910_MATERI.DAT

Directory : • indifferent (choice of the user) ***MATERI.DAT internal • current (opening FLUX) ***MATERI.DAT

Database choice The choice of a database is carried out in the supervisor.

To choose a database:

Step Action 1 In the Tools menu, point on Options 2 In the Options box, General tab, Material zone:

Choose one of following possibilities:

Shared Local Current dir. (In the install

directory …) Chose a directory (Prédéfined directory)

Chose an external database Chose a database (database

MATERI.DAT)



5.2. Advices for 2D users

Introduction This section gives some advices for 2D users.

General This part explains how to describe classical problems in 2D.

How to …? Do Set an application From the main menu:

• point on Application / Define • select an application

Create a TRA file From the main menu: • point on Project / Export / Export physics • click on Export physics to a TRA file

Magnetic applications

This part explains how to define current sources in magnetic applications.

How to …? Do

Define a conducting region (with total current defined)

• Choose the correct type of region: “Coil conductor region”

• Define the orientation of the current (positive or negative)

• Define the value of the current in the field “Coil Conductor Region component” ( the arrow will help you to define the circuit component corresponding to the total current source)

Define a conducting region (with current density defined)

• Choose the correct type of region: “Region with current density”

• Define the value of the current in the field “Current density by spatial formula”: - Uniform current density: ex : 0.1 A/mm² - Non uniform current density: enter a spatial formula



Magnetic applications

This part explains how to define current sources in magnetic applications.

How to …? Do

Create a sine supply in Transient Magnetic application

Enter a formula of type A*sin(B*time+C)

Where: • A is the magnitude • B pulsation, can be B’*PI • C is the phase

Create a trapezoidal supply in Transient Magnetic application

Enter a formula of type TRAPEZPER(TIME,A,B,C,D,E,F,G)

Where • A is the minimum value • B is the maximum value • C is the period • D is the duration of the ascending slope • E is the duration of the upper constant part • F is the duration of the descending slope • G is the time origin shift

Kinematic coupling

This part explains how to use kinematic coupling.

How to …? Do

Use a rotating airgap

Create: • a fixed mechanical set to assign to

fixed face regions • a compressible mechanical set to assign to

the airgap face region • a moving mechanical set to assign to

moving face regions Use a translating airgap

Create • a fixed mechanical set to assign to

fixed face regions • a compressible mechanical set to assign to

the airgap and the displacement face regions • a moving mechanical set to assign to

moving face regions


FLUX® 9.10 News of 3D postprocessor

6. News of 3D postprocessor

Introduction This chapter refers to news of 3D postprocessor.


• Storage of physical quantities in the nodes • New post-processing mode (menu compute FE quantities)

Complement / reading advice

Computation of magnetic losses (or iron losses) a posteriori is now proposed in the 3D postprocessor. Information relative to iron losses computations (for 2D and 3D applications) is detailed in the following chapters: • Chap 7 “Computation of iron losses: principles” • Chap 8 “Computation of iron losses: software aspects”


News of 3D postprocessor FLUX® 9.10



6.1. Storage of physical quantities in the nodes

Introduction This section refers to storage of physical quantities in each node of the

meshing.


• Storage of quantities in the nodes: foreword • Storage of quantities in the nodes: computation - direction of use



6.1.1. Storage of quantities in the nodes: foreword

Introduction In some cases, we need to store quantities in each node of the meshing.

• for magneto thermal application, we need to store losses by Joule effect in nodes of regions

• for an hysteresis model, we need to store H and B in nodes of regions for each time step

• …



6.1.2. Storage of quantities in the nodes: computation - direction of use

To store To store quantities in the nodes of the meshing

Step Action 1 Activate the following command sequence:

compute FE quantities / Prepare computation 2 Select STORED_QUANTITY 3 Define the post-parameter (for values storage)

• enter a spatial formula • enter a name and a comment • enter a unit

4 Choose the region for computation: • choose the region type (volume, surface, line) • select a (some) region(s) and finish by par END_LIST

5 Choose a type of continuity: • CONTINUOUS • CONTINUOUS_BY_ELEMENT • CONTINUOUS_BY_REGION

Creation of QUANTITY_RESULT_… executed. Creation of post-parameter executed





6.2. New post-processing mode (menu compute FE quantities)

Introduction New computations are proposed in FLUX Application 3D at the level of the

postprocessor (result module), such as the computation of magnetic losses (or iron losses), …

The a posteriori computations, integrally carried out in the result module, require the storage of an assembly of results of different types (values, curves, … ). Consequently, a new menu, for the carrying out and the management of these computations (compute FE quantities), is brought in FLUX.


• Necessity of a new menu: compute FE quantities • Computation a posteriori: principle

• QUANTITY RESULT: definition (structure) • QUANTITY RESULT: creation, edition, deletion • QUANTITY RESULT: stored results post-processing



6.2.1. Necessity of a new menu: compute FE quantities

Standard working

As part of standard FLUX simulation, the user: • achieve one* Finite Element computation (solve module) • then a result analysis (result module)

*in fact this is a mono solving process for a Steady state AC Magnetic, but a multi solving process for a transient Magnetic Application.

Standard post- processing

For result analysis, the general post-processable quantities are: • on the one hand, local quantities, post-processable in all the points of the

study domain • on the other hand, global quantities, resulting from an integration, post-

processable over the entire study domain or on a part of this domain

The different post-processing mode of theses quantities are presented in the chapter concerning result post-processing (volume 4). • graphic representation of local quantities directly on the 3D view (menu isoval and arrow) or on a spatial support (menu cUrve or Relief), …

• evaluation of global quantities by interactive integration (menu inteGral) or predetermined computation (menu compuTations).

The different post-processable quantities available for the different physical application are presented in the chapter relative to physical applications (volume 3).

Necessity of a new post-processing mode

With the new version (version 9.10), the user can achieve complementary computations a posteriori such as magnetic losses (or iron losses) computation, …

In this case, the user achieve: • one* Finite Element computation (Solve module) • then several computations a posteriori for iron losses (Bertotti formula, LS

model, …) (Result module)

For each computations a posteriori, the user keep information such as instantaneous power in a point, average power in a region, …

*in fact this is a mono solving process for a Steady state AC Magnetic, but a multi solving process for a transient Magnetic Application.




FLUX new features

This is why FLUX offers: • a new menu for computations a posteriori :

the menu compute FE quantities • a new type of entity (QUANTITY_RESULT) to store a set of results relative

to a computation a posteriori These new features are presented in the table below.

With the menu … you can compute … Exemple

compuTa-tions

a global quantity … The value (scalar, vectorial, real or complex) is measurable with a SENSOR The computed value is stored in an entity of RESULT type

FLUX_INDUCTOR, MAGNETIC_ENERGY MAGNETIC_FORCE …

compute FE quantities

a set* of local or global quantities Values are not measurable with a SENSOR The computed values are stored in an entity of QUANTITY_RESULT type

BERTTOTI_IRON_LOSSES LS_IRON_LOSSES_REGIONS LS_IRON_LOSSES_POINT STORED QUANTITIES

*The set of computed quantities depends on the type of computation realized.

It could be: • values in nodes • one or several curves • one or several values of particular results



6.2.2. Computation a posteriori: principle

Process A computation a posteriori could be broken up in several elementary stages

as presented in the table below.

Stage Description 1 Achievement of a computation a posteriori (post-computation) 2 Saving of a set of results (post-results)

relative to the realized computation (post-computation) 3 Post processing on the set of results (post-results)

relative to the realized computation (post-computation)

It is important to note that several computations a posteriori could be done (in the same project FLUX), that’s imply a management of set of results relative to each of these computations.

Practically … All that concern management of computations a posteriori is placed in a new

FLUX menu: compute FE quantities.

The FLUX commands relative to the different stages presented in the previous block are presented in the table below

Stage Description Commandes FLUX

1 Achievement of a computation a posteriori (or post-computation)

Prepare computation

2 Saving of a set of results (or post-results)

Automatic creation of an entity of QUANTITY_RESULT type

3 Results post-processing (or post-results)

Display values Draw curves Display isoval arrow

The commands Display values and Draw curves of the menu compute FE quantities send the user on the general commands of the Result menu of FLUX 3D.



6.2.3. QUANTITY RESULT: definition (structure)

Introduction An entity of QUANTITY RESULT type is an entity which allow the storage of

a set of results in the case of a computation a posteriori.

Definition An entity of QUANTITY RESULT type is defined by:

• a name • a type corresponding to the type of computation realized,

with information relative to the computation • a set of computation results

with information relative to these results - stored curves - post-parameters created - computed values

• the spatial support on which the computation has been done (point, region, …)

Name The name to identify the entity is set automatically by FLUX, during the

creation of this one. It is built as following : COMPUTATION_TYPE_1, … (See. block hereafter).

Types Les différents types de calcul proposés sont présentés dans le tableau ci-

dessous.

Type Définition

BERTTOTI_IRON_LOSSES Iron losses by means of the formula of Bertotti in regions

LS_IRON_LOSSES_REGIONS Iron losses with the LS model in regions

LS_IRON_LOSSES_POINT Iron losses with the LS model on a point

STORED QUANTITIES Stored quantities in each node of the meshing

Stored results The different stored results that could be saved are:

• stored curves • post-parameters created • computed values



6.2.4. QUANTITY RESULT: creation, edition, deletion

Commands of data handling

Entities of QUANTITY RESULT type are automatically created by FLUX, and couldn’t be modified.

The effect of general commands of data handling is presented in the table below.

Commande Commentaire

Create Automatic creation by FLUX with the achievement of the computation (command Prepare computation)

sHow Display in the dialog window of the entity of QUANTITY RESULT type selected

Modify

prInt Print in the print file (.PRT) and display in the dialog window of the entity of QUANTITY RESULT type selected

Delete

Reach general information

To reach general information relative to a computation (entity of QUANTITY RESULT type): • use the general command sHow

Results example: QUANTITY RESULT(1) = NAME(TEST) STORED_QUANTITY(...) PARAMETER_POST(TEST) SURFACE_REGIONS(...)

QUANTITY RESULT(2) = NAME(LS_IRON_LOSSES_POINT) LS_IRON_LOSSES_POINT(...) CURVES(NAME(LS_IRON_LOSSES_POINT),...) COMPUTED_VALUES(...)

Delete To delete set of results (entity of QUANTITY RESULT type)

• Activate the following sequence of commands: compute FE quantities / Delete computation



6.2.5. QUANTITY RESULT: stored results post-processing

Stored results post-processing

To realize the results post-processing, you have to use the commands of the menu compute FE quantities.

These commands allow reaching the different results stored in the entity of QUANTITY RESULT type.

The command … allows the post-processing …

Display values of computed values Draw curves of stored curves Display isoval arrow of post-parameters created




FLUX® 9.10 Computation of iron losses: principles

7. Computation of iron losses: principles

Introduction This chapter deals with the computation of magnetic losses, from the point

of view of principles.


• Computation of losses: general presentation • Computation of the magnetic losses by means of the formulas of Bertotti • Computation of the magnetic losses with the LS model


Computation of iron losses: principles FLUX® 9.10



7.1. Computation of losses: general presentation

Introduction This section deals with the computation of losses in electromechanical

devices, from a general perspective.

Content This section covers the following topics:

• The losses in the electromechanical devices: general • The magnetic losses: general computation methods • Energy, instantaneous power, average power: reminder of definitions



7.1.1. The losses in the electromechanical devices: general

Losses: general aspects

The power losses in the electromechanical devices are mainly of three types: • the magnetic losses in the magnetic circuits (also called ‘iron losses’) • the losses by Joule effect in the coils (also called ‘copper losses’) • the mechanical losses (mainly by friction and ventilation in the rotating

machines)

Losses in magnetic materials

The power losses in magnetic materials are connected to the phenomena associated with the time variation of the magnetic field.

They are classically subdivided into hysteresis losses, of microscopic origin and Foucault currents losses, of macroscopic origin. In fact it is a matter ofeddy current in both cases. • The hysteresis losses are generated by the time variation of the magnetic

microstructure of the matter, mainly by the movement of the walls of the magnetic domains (Weiss);

• The Foucault losses are caused by the Joule effect of the induced (eddy) currents, whose intensity is proportional to the frequency of the excitation magnetic field. Thus, these losses are proportional to the square of frequency of the excitation magnetic field.

Magnetic losses and the hysteresis cycle

When the magnetic field has a cyclic variation in time, the magnetic materials are characterized by the locus of points (B, H), which is a closed curve.

The process of cyclic magnetization determines the transformation of a part of the electromagnetic energy into thermal energy. In terms of power, it deals with the magnetic losses due to the cyclic magnetization.

The cyclic variation in time of the magnetic field determines Foucault (eddy) currents in the magnetic materials which have electro-conductive properties. The Joule effect of these currents determines the Foucault currents losses.

For reduced values of the frequency (f < 1Hz), the closed curve B(H), called static hysteresis cycle, does not depend on the frequency. The corresponding magnetic losses, called hysteresis losses, are proportional to the area of the static hysteresis cycle and with the frequency.

When the frequency increases, the area of the closed curve B(H), usually called dynamic hysteresis cycle, increases. In this case, the magnetic losses, due to the cyclic magnetization, are greater than the hysteresis losses. The losses that correspond to the difference between the area of the dynamic hysteresis cycle and that of the static hysteresis cycle are usually called supplementary magnetic losses. In case of magnetic steels, these losses can be negligeable for frequencies equal to or under 50 Hz, but they become important for frequencies of the kHz order of magnitude.




Magnetic losses and the hysteresis cycle (continued)

Modeling … A more thorough study demonstrates that the losses are a response to very

complex phenomena, often interconnected and pertaining to the microstructure of the magnetic alloys. Consequently, their dependence on the frequency and on the magnetic flux density is often difficult to model, and it depends on the studied alloys.



7.1.2. The magnetic losses: general computation methods

Introduction The computation of the magnetic losses and the modeling of the soft magnetic

materials are two utterly interdependent points.

That is why the computation of the losses can be envisaged in two ways, as presented in the table below, and in the following sections.

Principle of the method

1 • the hysteresis is taken into consideration at the level of the magnetic behavior law B(H)

• the computation of the magnetic losses is therefore carried out directly

2 • the hysteresis is neglected at the level of the magnetic behavior law B(H)

• the computation of the magnetic losses is carried out a posteriori starting from theoretical or experimental formulas

Modeling of hysteresis (1)

The first approach concerns the modeling of hysteresis at the level of the magnetic behavior law B(H). It deals with the integration of the B(H) dependence in the direct solving of the problem.

Even if all the numerical problems of convergence and of management of the history of the magnetization process are solved out, this approach requires important computation time and memory size, which makes the simulations extremely difficult in the case of rotating machines.

Computation a posteriori (2)

With this second approach, the hysteresis is not introduced at the level of the magnetic behavior law B(H).

Neglecting the magnetic hysteresis in the direct solving of the problem results from the need for simplification, but also from the hypothesis that the hysteresis does not modify in an essential manner the repartition of the magnetic flux in the device.

The computation of the spatial and temporal repartition of the magnetic flux density is carried out by means of an univocal B(H) characteristic. Then, starting from this distribution, the magnetic losses are calculated by means of the theoretical or experimental formulas.




Literature: computation of the magnetic losses

In order to calculate the power correspondent to the magnetic losses, the following expressions are found in the literature: • for the magnetic losses by hysteresis :

hysteresis) where: η is the coefficient of Steinmetz, ranging from 1.6 to 2.0 f is the frequency B

η

= maxhh BfkP (

max is the pick value of the magnetic flux density • for the losses generated by the Foucault (eddy) currents : (eddy currents) 2

max2

ecec BfkP =

With FLUX … FLUX proposes the users two modes of computation of the magnetic losses.

In both cases, it is a matter of an a posteriori computation of the magnetic losses. The hysteresis is therefore not modeled directly at the level of the solving process and the B(H) magnetic behavior law is an univocal relationship.

The two proposed modes of computation are presented in the diagram below and detailed in the next sections.

FLUX simulation in Steady state AC Magnetic

Value of B in each node of the meshing

Calculus of the losses by means of the

formulas of Bertotti

Solver 2D or 3D

Post Processor 2D or 3D

Introduction of the B(t) signal in the LS model and calculus of losses

FLUX simulation in Transient Magnetic

Signal B(t) in each node of the meshing



7.1.3. Energy, instantaneous power, average power: reminder of definitions

Introduction Before approaching the computation of the magnetic losses for the Steady

state AC Magnetic and Transient Magnetic applications of FLUX, this paragraph reminds what the physical quantities calculated in FLUX are: energy, instantaneous power, average power.

Post-processable quantities

The post-processable quantities in the 3D problems are of two types: • local quantities, post-processable in all the points of the study domain • global quantities, resulting from an integration, post-processable over the

entire study domain or on a part of this domain

These physical quantities are presented in the two tables below.

Local quantity Name Obtained by Unit Volume density of

instantaneous power dP(t) W/m3

Volum density of energy over the period dW ( )dttdPdW

T

0∫=

J/m3

Volume density of average power over a period dPmoy ( )dttdP

T1dP

T

0moy ∫= W/m3

Global quantity Name Obtained by UnitInstantaneous

power P(t) ( ) (∫∫∫=reg

dvtdPtP ) W

Energy over the period W ( )∫=

T

0dttPW

∫∫∫=reg

dvdWW J

Average power (over a period) Pmoy ( )dttP

T1P

T

0moy ∫=

∫∫∫=reg moymoy dvdPP W

Vocabulary Therefore in this document we speak about:

• Instantaneous power of the losses, or Instantaneous losses • Energy of the losses over the period • Average power of the losses, or Average losses



7.2. Computation of the magnetic losses by means of the formulas of Bertotti

Introduction This section deals with the computation of the magnetic losses in FLUX by

means of the formulas of Bertotti.


• General expression of the magnetic losses: formulas of Bertotti • Computation of the losses in Steady state AC Magnetic applications

(formulas) • Computation of the losses in Transient Magnetic applications (formulas) • Estimation of the coefficients of Bertotti • Analysis of the results: the post processable quantities

Bibliography Supplementary information on the modeling of the magnetic losses by means

of the theory of Bertotti is available in the paper: «An improved approach to power losses in magnetic lamination under non sinusoïdal induction waveform» - F. Fiorillo and A. Nokinov – IEEE Trans. on Magn. Vol 26 n°5 sept. 1990



7.2.1. General expression of the magnetic losses: formulas of Bertotti

Decomposition of the losses

The total magnetic losses can be decomposed into three categories: • the losses by hysteresis (P1), proportional to the frequency f, which are the

most significant component of the magnetic losses at low frequency • the classical Foucault currents losses (P2), proportional to 2f • the supplementary losses or losses in excess (P3), proportional to 23f

The separation of the two last types of losses is artificial. They can be regrouped in one term and they therefore correspond to the losses associated with the cyclic magnetization process.

Expression of the losses

The theory of Bertotti gives us the expression of the magnetic losses in function of the frequency and of the peak value of the magnetic flux density.

The density of power is expressed by means of the relationship:

=dP fBc 2m1 + ( )2

m2 fBc + ( ) 2/3m3 fBc

↑ ↑ ↑ P1 P2 P3 where: • c1 is the coefficient of losses by hysteresis • c2 is the coefficient of classical Foucault currents losses • c3 is the coefficient of supplementary losses or in excess losses • f is the frequency • Bm is the maximum induction attained

The coefficients c2 and c3 are expressed by means of the following relationships:

6dc 222 σπ= where:

• σ is the electric conductivity of the magnetic material • d is the thickness of the sheet (lamination)

SVGc 03 σ= where:

• G is a constant without dimension • S is the cross-section of the sheet (lamination)

• V0 is a constant field, which depends on the difference of coercitive magnetic field strength between two magnetic objects (Mos) according to the theory of Bertotti



7.2.2. Computation of the losses in Steady state AC Magnetic applications (formulas)

Steady state AC Magnetic: reminder

In a Steady state AC Magnetic application we are interested to study the permanent sinusoidal time variation of the magnetic field.

The unknown (potential) variables and the derived physical quantities (magnetic field strength and magnetic flux density) are supposed to vary in a sinusoidal manner in function of time.

The complex representation is therefore utilized, and the solution can be obtained in one solving.

Power As far as the magnetic losses are concerned, the volume density of average

power dPmoy is written:

=moydP fBk 2mh + ( )2

m

22

fB6

dσπ + ( ) 67,8.fBk 2/3me (1)

↑ ↑ ↑ Losses by

hysteresis Classical losses Losses

in excess

where: • kh is the coefficient of losses by hysteresis • ke is the coefficient of losses in excess • σ is the conductivity of the material • d is the thickness of the lamination • f is the frequency • Bm is the peak value of the magnetic flux density which becomes, within the computation frame of FLUX:

( ) ( ) f2/3

me2

m

222mhmoy k67,8.fBkfB

6dfBkdP ⎥

⎦

⎤⎢⎣

⎡+

σπ+= (2)

where: • kf is the coefficient of filling (close to 1). This coefficient considers the

electrical insulation of the laminations of the magnetic core. The average power dissipated in a volume region is written as: dvdPP

reg moymoy ∫∫∫=




Limits of validity (case of asynchronous machines)

It is important to note that in the previous formula the Bm variable stands for the peak value of the magnetic flux density.

The software utilizes the value of the magnetic flux density in each point. Consequently, it is convenient to be very careful with the results concerning the problems represented by the rotating machines with the Steady state AC Magnetic simulation.

Indeed, for this type of simulation the rotor has a fixed position with respect to the stator, and the real rotor movement is modeled by changing the resistivity of the conductors of the rotor electric circuit. Thus, the calculated magnetic flux density in a point is dependent on the given position of the rotor in relationship with the stator. This value in a point can be different from a rotor-stator position to another, reflecting the space harmonics of the magnetic field. It follows that the calculated magnetic flux density does not correspond to the peak value of the magnetic flux density over a period in the time domain if the rotor were turning. Consequently, the computation of the magnetic losses must be utilized in this case with much caution.

Moreover, in the case of a non-linear approximation for the magnetic behavior law B(H), the saturation phenomenon, introduced by means of an equivalent model of magnetization, can alter the local values of the magnetic flux density.



7.2.3. Computation of the losses in Transient Magnetic applications (formulas)

Transient Magnetic: reminder

In a Magneto Transient application, we are interested to study the variable regime or the transient time variation of the magnetic field.

The computation carried out is of step by step in time domain type.

Instantaneous power

As regards the magnetic losses, the volume density of the instantaneous power dP(t) is written:

( ) =tdP fBk 2mh + ( )

22

tdtdB

12d

⎟⎠⎞

⎜⎝⎛σ + ( )

2/3

e tdtdBk ⎟

⎠⎞

⎜⎝⎛ (3)

↑ ↑ ↑ Losses by

hysteresis Classical losses Losses in

excess

where: • kh is the coefficient by hysteresis • ke is the coefficient of losses in excess • σ is the conductivity of the material • d is the thickness of the lamination • Bm is the peak value of the magnetic flux density which becomes, within the frame of FLUX computation:

( ) ( ) ( ) f

2/3

e

222mh kt

dtdBkt

dtdB

12dfBktdP

⎥⎥⎦

⎤

⎢⎢⎣

⎡⎟⎠⎞

⎜⎝⎛+⎟

⎠⎞

⎜⎝⎛σ+= (4)

where: • kf is the coefficient of filling (close to 1). This coefficient considers the

electrical insulation of the laminations of the magnetic core.

Average power over a period

The volume density of the average power over a period, dPmoy is written as:

( )dttdPT1dP

T

0moy ∫=

which becomes:

( ) ( ) dtktdtdBkt

dtdB

12d

T1kfBkdP f

T

0

2/3

e

22

f2mhmoy ∫

⎥⎥⎦

⎤

⎢⎢⎣

⎡⎟⎠⎞

⎜⎝⎛+⎟

⎠⎞

⎜⎝⎛σ+= (5)

The average power dissipated in a volume region is written as:

dvdPPreg moymoy ∫∫∫=



7.2.4. Estimation of the coefficients of Bertotti

Necessary coefficients

In order to calculate the magnetic losses by the formula of Bertotti, we have to define the coefficients for the concerned regions, which are presented in the table below.

Coefficient Unit

kh coefficient of magnetic losses by hysteresis WsT-2m-3 σ conductivity (coefficient of classical Foucault

currents losses) Sm-1

ke coefficient of losses in excess W(Ts-1)-3/2m-3 d thickness of the sheet m kf coefficient of filling (0 < kf ≤ 1) - f frequency (except in Steady state AC Magnetic) Hz

Estimation of coefficients

In order to determine the coefficients kh and ke, we have to refer to the data provided by the manufacturers of laminations.

Generally, the manufacturers provide the value of iron losses for given values of the magnetic flux density and frequency. Two values of losses, for two different values of magnetic flux density and/or frequency are enough in order to determine these coefficients by the equation (1) given below.

Example: For the lamination Fe V 1000-65-H (with σ = 4739300 Sm-1 and d = 0,65 10-3m), the volume losses for the frequency f = 50 Hz, for Bm = 1.0 T and Bm = 1.5 T allow to define the coefficients kh and ke.

Typical values: • kh = 363 WsT-2m-3 • ke = 16,2 W(Ts-1)-3/2m-3



7.2.5. Analysis of the results: the post processable quantities

The post-processable quantities

The post-processable quantities are: • on the one hand, the density of the iron losses

(local quantity, post-processable in all the points of the study domain) • on the other hand, the iron losses (global quantities, resulting from an

integration, post-processable over the entire study domain or on a part of this domain)

Local quantities

The available local quantities are presented in the table below. The instantaneous quantities are quantities calculated only for a Transient Magnetic application.

Quantity Name Unit Interpretation Instantaneous density of iron losses: dP(t)

DP_…_INST W/m3

Average density of iron losses: dPmoy

DP_…_MOY W/m3 ( )dttdPT1dP

T

0moy ∫=

The density of iron losses is a density of total iron losses, which can be decomposed into three terms: • the density of partial iron losses by hysteresis • the density of classical partial iron losses by Foucault currents • the density of supplementary or in excess partial iron losses

These different terms are equally accessible (only in 3D).

Global quantities

The available global quantities are presented in the table below. The instantaneous physical quantities are physical quantities calculated only for a Transient Magnetic application.

Quantity Name Unit Interpretations Instantaneous iron losses: P(t)

P_… _INST W ( ) ( )∫∫∫=

regdvtdPtP

Average iron losses: Pmoy

P_… _MOY W ( )dttP

T1P

T

0moy ∫=

∫∫∫=reg moymoy dvdPP

Energy of iron losses: W

WP J ( )∫=T

0dttPW

∫∫∫=reg

dvdWW

The iron losses are total iron losses, which can be decomposed into three terms: • the partial iron losses by hysteresis • the classical partial iron losses by Foucault currents • the supplementary partial iron losses

These different terms are equally accessible (only in 3D).





7.3. Computation of the magnetic losses with the LS model

Introduction This section deals with the computation of the magnetic losses in FLUX by

means of the LS model (Loss Surface).


• General presentation of the LS model • The characterized materials (nuances of sheets) • Computation of the losses with the LS model • Analysis of the results: the post-processable quantities



7.3.1. General presentation of the LS model

Introduction The LS (Loss Surface) model is a method of estimation of the magnetic losses

a posteriori, based on a model of dynamic hysteresis associated to a finite elements simulation.

Principle The detailed principle of the method is given in the appendix. Only certain

main points are described in this section.

The LS model requires that the magnetic behavior of a material be perfectly well defined, having knowledge of a characteristic surface H(B,dB/dt) (determined experimentally).

Thus, for a B(t) signal of a certain shape and frequency, we can go up via the H(B,dB/dt) surface to the H(t) field, and thus reconstruct the dynamic cycle of hysteresis corresponding to it.

This principle is represented in a schematic manner in the figure below.

Signal B(t) of a certain shapeand frequency

Reconstruction of signal H(t)(Reconstruction of dynamic hysteresis cycle)

Characteristic H (B, dB/dt) surface of thematerial measured experimentally

Calculus of losses

Characteristic surface H(B,dB/dt)

For each of the materials, the characteristic surface H(B,dB/dt) can be obtained by using a Epstein type device for magnetic measurements in medium frequency.

An example of this type of surface is represented in the figure below.




Reconstruction of the cycle

An analytical model permits the reconstruction of the signal H(t) of the magnetic field strength starting from the signal B(t) of the magnetic flux density:

H(B,dB/dt) = Hstatic(B) +Hdynamic (B,dB/dt)

B(H) curves like those in the figure below can therefore be obtained, permitting the computations of iron losses quite accurately.

-1.6

-1.2

-0.8

-0.4

0

0.4

0.8

1.2

1.6

-1800 -1200 -600 0 600 1200 1800

H (A/m) Estimated Measured

Sinusoidal magnetic flux density + 5th harmonic at 200Hz

With FLUX … This model of magnetic losses is not a generic model. It requires the

following information for each of the materials: • knowledge of the characteristic surface H(B,dB/dt), which must be

measured experimentally • a reconstruction of the H(t) signal

That is why this model is described in FLUX by means of the subroutines* (one subroutine to each quality of laminations). *Note : this is not user subroutines.



7.3.2. The characterized materials (nuances of sheets)

Available materials

The LS model is assigned to different nuances of laminations, which have been especially described to this purpose.

These are (by the international nomenclature IEC 60404-8-4-1998): • M100065D • M60065A • M80065A • M60050A • M40050A • M33065A • M33035A • M27035A • M100065NR ( = M100065D but Non Annealed) • M33035 A ARCELOR • M80050A

If you will wish to add a new material, get in touch with Cedrat and the L.E.G. (Laboratoire d’Electrotechnique de Grenoble); you should expect a minimum delay of approximately six months.



7.3.3. Computation of the losses with the LS model

Magneto Transient: reminder

In a Transient Magnetic application, we are interested to study the variable regime or the transient time variation of the magnetic field. The computation carried out is of step by step in time domain type.

The calculable powers …

As regards the magnetic losses, it is possible to calculate: • the volume density of instantaneous power dP(t) via the analysis carried

out by means of the LS model • the volume density of average power over a period dPmoy :

( )dttdP

T1dP

T

0moy ∫=

• the average power over a period , dissipated over a region:

dvdPP

reg moymoy ∫∫∫=

Problematic Within a Transient Magnetic application, it is the computation of the

Instantaneous power of losses, or Instantaneous losses over a region, which is carried out for each of the time steps. In order to calculate the Average power of the losses or Average losses over a region, we have to get the average of the Instantaneous power of the losses, over a period. The user must therefore define the period for the computation of this average value.

Definition of the period

In practice, for each of the proposed computations at the level of the post processor, the user has to define the time interval corresponding to a period. In reality, one can define a time interval which represents a complete period or a portion of a period (period, half-period, quarter of a period). The various possibilities are presented in the table below.

Choice Description

Period If the period involves N time steps, the user selects the time steps 1 and N+1 (The time steps 1 and N+1 are identical)

Half-period If the period involves 2N time steps, the user selects the time steps 1 et N+1 (FLUX reconstitutes the electrical period which comprises 2N+1 time steps. The time steps 1 and 2N+1 are identical)

Normal symmetry f(T/2+t) = - f(t)

Aperiodic FLUX does not take into consideration this period.



7.3.4. Analysis of the results: the post-processable quantities

The post-processable quantities

The post-processable quantities in the 3D problems are of two types: • local quantities, post-processable in all the points of the study domain • global quantities, resulting from an integration, post-processable over the


These physical quantities are presented in the two tables below.

Local quantities

The available local quantities are presented in the table below. The instantaneous quantities are quantities calculated only for a Transient Magnetic application.

Quantity Name Unit Interpretation B reconstituted: BLS BMAG1_LS T H reconstituted: HLS HMAG1_LS A/m Density of instantaneous iron losses: dP(t)

DP_…_INST W/m3

Density of average iron losses: dPmoy

DP_…_MOY W/m3 ( )dttdPT1dP

T

0moy ∫=

Global quantities

The available global quantities are presented in the table below. The instantaneous quantities are quantities calculated only for a Transient Magnetic application.

Quantity Name Unit Interpretation Instantaneous iron losses: P(t)

P_… _INST W ( ) ( )∫∫∫=

regdvtdPtP

Average iron losses: Pmoy

P_… _MOY W ( )dttP

T1P

T

0moy ∫=

∫∫∫=reg moymoy dvdPP

Energy of iron losses: W

WP J ( )∫=T

0dttPW

∫∫∫=reg

dvdWW


FLUX® 9.10 Computation of iron losses: software aspects

8. Computation of iron losses: software aspects

Introduction The computation of magnetic losses, or iron losses, is an a posteriori

computation, which is carried out at the post processing level (2D or 3D) of FLUX.

This chapter presents the operational modes for the computation of losses, starting from the formulas of Bertotti, or by means of the LS model (Loss Surface): • on the one hand, for the computations carried out in 2D (FLUX 2D

Application) • on the other hand, for the computations carried out in 3D (FLUX 3D

Application )


• Iron losses: computation in 2D (FLUX 2D application) • Iron losses: computation in 3D (FLUX 3D application)

Reading advice This chapter deals only with the practical aspects (implemented at the level of

the software). For the theoretical aspects (principles), please refer to the «Computation of iron losses: principles» chapter.


Computation of iron losses: software aspects FLUX® 9.10



8.1. Iron losses: computation in 2D (FLUX 2D application)

Introduction This section deals with the computation of magnetic losses, or iron losses in

2D (FLUX application 2D), starting from the formulas of Bertotti, and by means of the LS model.


• Iron losses 2D (formulas of Bertotti): foreword • Iron losses 2D (formulas of Bertotti): computation – directions of use

• Iron losses 2D (LS model): foreword • Iron losses 2D (LS models): computation – directions of use

Attention !! The iron losses computation:

• starting from the formulas of Bertotti is carried out by means of the ‘standard’ post processor of FLUX 2D: POSTPRO_2D

• with the LS model it is carried out by means of the ‘ancient’ postprocessor of FLUX 2D: EXPGEN



8.1.1. Iron losses 2D (formulas of Bertotti): foreword

Module FLUX The computation of magnetic losses, or iron losses is an a posteriori

computation, which is carried out at the level of the ‘standard’ postprocessor of FLUX 2D: POSTPRO_2D.

Applications The computation of magnetic losses, or iron losses, starting from the formulas

of Bertotti can be carried out with the following magnetic applications: Steady state AC Magnetic and Transient Magnetic.

Effected computations

Within the frame of a Steady state AC Magnetic application, it is the computation of the Average Power of losses (or Average losses) that is carried out.

Within the frame of a Transient Magnetic application, it is the computation of the Instantaneous Power of losses (or Instantaneous losses) that is carried out.

Process in two stages

The computation process is carried out in two stages as presented in the table below.

Stage Description

1 Allocating of the «Bertotti coefficients» to the region(s) concerned by the computation

2 Computation of the iron losses over one or some of the regions: • for a Steady state AC Magnetic application (Mag Harm) :

computation of average losses • for a Transient Magnetic application (Mag Trans) :

computation of instantaneous losses in function of time

It is important to note that the assembly of coefficients is set at 1 by default.



8.1.2. Iron losses 2D (formulas of Bertotti): computation – directions of use

Introduction The operating mode for the computation of losses starting from the formulas

of Bertotti is presented for the Mag Harm and Mag Trans applications.

Allocate the coefficients

In order to allocate the values of the «Bertotti coefficients» to the region(s) concerned by the computation:

Step Action 1 In the Physics menu:

point on Coefficients … and click on Modify … 2 In the dialogue box Physics properties/ tab Coefficients:

• for the desired region : click on Iron losses coefficients in the Losses column

3 In the dialogue box Iron losses coefficients: • enter the values of the following coefficients :

hysteresis losses coefficient (kh) W.s.T-2.m-3 classical losses coefficient (σ) S.m-1 losses in excess coefficient (ke) W.(T.s-1)-3/2.m-3

thickness of lamination (d) m stacking factor (kf) - frequency of the sources (f) Hz

• click on OK 4 In the dialogue box Physics properties / tab Coefficients:

• resume from stage 2 for the following region or • click on OK to finish the sequence

Bertotti computation in Mag Harm

In order to calculate the average iron losses over one of the regions in Steady state AC Magnetic, starting from the Bertotti formulas:

Step Action

1 In the Computation menu: Click on On a support …

2 In the box Computation on a support manager: • select a region • click on the button Properties…

3 In the box Computation properties • click on Scalar iron losses / Total core losses / Add • click on OK

4 In the box Computation on a support manager: • click on Compute

The result is displayed in the box Computation on a support manager




Bertotti computation in Mag Trans

In order to trace the evolution of the instantaneous iron losses over one or some regions in Transient Magnetic, calculated starting from the formulas of Bertotti:

Step Action

1 In the menu Computation: Click on 2D curves manager…

2 In the box 2D curves manage: • in the zone Curve description

choose Parameter • in the zone First axis

choose Time • in the zone Second axis

choose Scalar iron losses • in the zone Third data

choose the region for the computation

• click on the button Create or the icon Create and Display The curve is displayed in the 2D Curve sheet …

Attention The losses are given by the average value of the instantaneous losses

calculated over a period. In transient magnetic this computation must be carried out over a complete period.



8.1.3. Iron losses 2D (LS model): foreword

Module FLUX The computation of the magnetic losses, or iron losses, is an a posteriori

computation, which is carried out at the level of the ‘ancient’ post processor of FLUX 2D: EXPGEN

This module is accessible at the level of the supervisor (tab FLUX 2D): Compatibility / Analysis compatibility / Result with Expgen

Applications The computation of the magnetic losses, or iron losses with the LS model can

be carried out only by the Transient Magnetic applications. The simulation is a simulation carried out step by step in time.


Within a Transient Magnetic application, it is the computation of the Instantaneous power of losses (or Instantaneous losses) that is carried out.



8.1.4. Iron losses 2D (LS models): computation – directions of use

Exploitation of results

It is possible to carry out the exploitations of the following results: • display of the density of iron losses over one region

in color shade form • evaluation of the density of iron losses in a point

and tracing of B and H reconstituted in that point (curve B(H)) • computation of the iron losses in a region

It is equally possible to achieve: • the export of the densities of iron losses to the nodes of the meshing

(for a possible thermal computation)

Display the density of iron losses in color shade form

In order to display the density of iron losses over a region in color shade form, the sequence of questions/answers described in the table below should be followed:

The starting point is the main menu of EXPGEN.

Question Answer Chosen command Select [1_Display] What view you choose Select [5_Color shades] Chosen region Choose from among:

• [1_Whole] • [2_Group regions] … • directly one region

What quantity you want to treat Select [K_Iron power_dens.] Sample to be treated Select [BEGIN_END]

Choose the interval: • click on the 1st time step • click on the 2nd time step

Type of sheets Choose a material from the list Part of period represented by the time steps

Choose from among: • [1_full cycle] • [2_half cycle] • [4_no cycle]




Evaluate the density of iron losses in a point

In order to evaluate the density of the iron losses in a point and to trace B and H reconstituted in that point (curve B(H)), the sequence of questions/answers described in the table below should be followed: The starting point is the main menu of EXPGEN.

Question Answer Chosen command Select [6_Time variation] Sample to be treated Select [BEGIN_END]


Type of size Select [1_Point] What quantity you want to treat Select [K_LS_Iron_Density] Choose a point of computation Select [1_Coordinates]

X (mm): Enter the value of X Y (mm): Enter the value of Y

Type of sheets Choose a material from the list Part of period represented by the time steps


How should the values be used Choose from among: • [Quit] • [1_Print] • [2_Display] • [4_Mean Values] • [5_Integrals] • [6_Spectrum]

Remark: If the point of computation belongs to the rotor, the point turns with the rotor. The components X and Y of FLUX 2D are in fact the components R and θ associated to a cylindrical coordinates system, turning with the rotor. For example, for a point belonging to a magnet turning in the air, the components R and θ are time independent.

Example of curved obtained

An example of a curve obtained is represented in the figure opposite right.




Calculate iron losses in one region

In order to calculate the iron losses in a region, the sequence of questions/answers described in the table below should be followed. The starting point is the main menu of EXPGEN.

Question Answer Chosen command Select [6_Time variation] Sample to be treated Select [BEGIN_END]


Type of quantity Select [2_Region] What quantity you want to treat Select [LS_iron_losses] Chosen region Choose from among:

• [1_Whole] • [2_Group Regions] … • directly one region

Type of sheets Choose a material from the list Portion of period represented by the time steps


How should the values be used Choose from among: • [Quit] • [End_Time variation] • [1_Print] • [2_Display] • [4_Mean values] • [5_Intgrals] • [6_Spectrum]

Remark: • The average value that corresponds to the searched iron losses over the

region, for the period considered, must be displayed. • If the region belongs to the rotor, the points of computation turn with the

rotor. In this case, the iron losses correspond well to the variations of flux viewed by the rotor.

Example of curve obtained

An example of curve obtained is represented in the figure opposite right.




Export In order to export the values of the densities of the iron losses to the different

nodes of the finite elements meshing (for a possible thermal computation), the sequence of questions/answers described in the table below should be followed. The starting point is the main menu of EXPGEN.

Question Answer

Chosen command Select [C_Extract] Chosen region Choose from among:

• [1_Whole] • [2_Group regions] … • directly one region

What quantity you want to treat Select [6_LS_Iron_Density] Sample to be treated Select [BEGIN_END]


Type of sheets Choose a material from the list Portion of period represented by the time steps






8.2. Iron losses: computation in 3D (FLUX 3D application)

Introduction This section deals with the computation of the magnetic losses or iron losses

in 3D (FLUX application 3D), starting from the formulas of Bertotti, and with the LS model.


• Iron losses 3D (formulas of Bertotti): foreword • Iron losses 3D (formulas of Bertotti): computation – directions of use

• Iron losses 3D (LS model): foreword • Iron losses 3D (LS model): computation – directions of use

Reading advice Complementary information on the novelties of the 3D post processor is

presented in the chapter ‘New mode of exploitation (compute FE quantities).



8.2.1. Iron losses 3D (formulas of Bertotti): foreword

Module FLUX The computation of the magnetic losses, or iron losses is an a posteriori

computation, which is carried out at the level of the post processor (Results module).

Applications The computation of the magnetic losses, or iron losses starting from the

formulas of Bertotti, can be carried out by means of the following magnetic applications: Steady state AC Magnetic and Transient Magnetic.


Within a Steady state AC Magnetic application, it is the computation of the Average Powers of losses or Average losses that is carried out.

Within a Transient Magnetic application, it is the computation of the Instantaneous powers of losses (or Instantaneous losses) that is carried out.



Stage Description

1 Carrying out of an a posteriori computation with Recording of the assembly of results concerning the computation carried out

2 Exploitation of the assembly of results concerning the computation carried out

It is important to remark that several computations a posteriori can be carried out within the same FLUX project, which requires the need for a management of the assembly of results pertaining to each of these computations.



8.2.2. Iron losses 3D (formulas of Bertotti): computation – directions of use

Introduction The operating mode for the computation of the iron losses starting from the

formulas of Bertotti is presented for the Mag Harm and Mag Trans applications.

Bertotti computation in Mag Harm

In order to calculate the average iron losses over one or some regions in Steady state AC Magnetic starting from the formulas of Bertotti:

Step Action 1 Activate the following command sequence:

compute FE quantities / Prepare computation 2 Select BERTOTTI_IRON_LOSSES 3 Choose an assembly of regions (finish by END_LIST)

Enter the values of the following coefficients: hysteresis losses coefficient (kh) W.s.T-2.m-3 classical losses coefficient (σ) S.m-1 losses in excess coefficient (ke) W.(T.s-1)-3/2.m-3


4 To continue with another assembly of regions resume stage 3 or finish the operation by END_LIST

The computation of average losses is achieved. A QUANTITY RESULT entity is created (name: BERT_IRON_LOSSES_RG_1, …)) and the calculated values are displayed.

Assembly of recorded results

The assembly of results of the computation (BERT_IRON_LOSSES_RG_1, …) comprises: • created post-processing parameters:

- density of the average losses DVOL_MEAN_BERT_L - density of energy of the losses DVOL_BERT_LW

• calculated values : - average total losses total over the region - average partial losses by hysteresis over the region - classical average partial losses over the region - average partial losses in excess over the region


It is possible to achieve the following exploitations of results: • Display in color shade:

- density of average losses over the regions, … - density of the energy of the losses over the regions, …




Bertotti computation in Mag Trans

In order to calculate the losses* over one or some regions, in Transient Magnetic starting from the formulas of Bertotti: *It is about instantaneous losses for each time step, and the average losses over a specified time interval

Step Action

0* Activate the command sequence vAr select / TIME Choose the initial time step (different from the first two time steps)

1 Activate the following sequence of commands: compute FE quantities / Prepare computation

2 Select BERTOTTI_IRON_LOSSES 3 Choose an assembly of regions (finish by END_LIST)

Enter the values of the following coefficients: hysteresis losses coefficient (kh) W.s.T-2.m-3 classical losses coefficient (σ) S.m-1 losses in excess coefficient (ke) W.(T.s-1)-3/2.m-3


4 To continue with another assembly of regions resume stage 3 or finish the operation by END_LIST

5 Choose the final time step The computation of instantaneous losses is carried out for each

time step; then the computation of the average losses is carried out for the specified time interval. A QUANTITY RESULT entity is created (name: BERT_IRON_LOSSES_RG_1, …) and the calculated values are displayed.

*The 0 stage permits the choice of the initial time step. If this is not carried out, then it is the current time step that is the initial time step.

Assembly of recorded results

The assembly of the computation results (BERT_IRON_LOSSES_RG_1, …) comprises: • a stocked curve:

- the instantaneous losses INST_BERT_LOSSES in function of TIME • created post-processing parameters:

- density of the average losses DVOL_MEAN_BERT_L - density of energy of the losses DVOL_BERT_LW

• calculated values : - average total losses over the region - average partial losses by hysteresis over the region - classical average partial losses over the region - average partial losses in excess over the region





It is possible to carry out the exploitations of the following results: • Tracing of curves (stocked curves):

- density of instantaneous losses in a point in function of time • Displaying in gradation of color:

- density of average losses over the regions, … - density of energy of losses over the regions, …

Remark The commands relative to the exploitation of results in the menu compute

FE quantities are presented in the chapter 6.



8.2.3. Iron losses 3D (LS model): foreword

Module FLUX The computation of the magnetic losses, or iron losses is an a posteriori

computation, which is carried out at the level of the post processor (Results module).

Applications The computation of the magnetic losses, or iron losses with the LS model can

be carried out only in the Transient Magnetic applications. The simulation is a simulation carried out step by step in time.


Within a Transient Magnetic application, it is the computation of the Instantaneous powers of losses (or Instantaneous losses) that is carried out.



Stage Description

1 Carrying out of an a posteriori computation with Recording of the assembly of results concerning the computation carried out

2 Exploitation of the assembly of results relative to the computation carried out

It is important to remark that several computations a posteriori can be carried out within the same FLUX project, which requires the need for a management of the assembly of results pertaining to each of these computations.



8.2.4. Iron losses 3D (LS model): computation – directions of use

Introduction The operating mode for the computation of the iron losses with the LS model

is presented for the Transient Magnetic application.

LS iron losses computation

In order to calculate, with the LS model: • the iron losses in a region • the density of the iron losses in a point

Step Action

0 Activate the sequence of command vAr select / TIME Select the initial time step (!! different from the first two time steps !!)

1 Activate the following sequence of commands: compute FE quantities / Prepare computation

2 Activate one of the following sequences of commands:

Computation over one (some) region(s)

Computation in a point …

LS_IRON_LOSSES_REGION LS_IRON_LOSSES_POINT Choose one (some) region(s) Choose a point Finish by END_LIST Finish by VALIDATE

Choose a type of sheet (LS model) Resume the operation or

finish by END_LIST

3 Select the final time step 4 Define the part of period represented by the time steps:

• FULL CYCLE

• HALF CYCLE

• NO CYCLE The computation of instantaneous losses is carried out for each time

step; then, the computation of the average losses over a period is carried out (by means of a specified time interval).

A QUANTITY RESULT entity is created (name: LS_IRON_LOSSES_REGION_1 or LS_IRON_LOSSES_POINT_1) and the calculated values are displayed.




Assembly of recorded results (in a point)

The assembly of computation results (LS_IRON_LOSSES_POINT_1) comprises: • stocked curves:

- density of instantaneous losses DINST_LS_LOSSES in function of time TIME

- BLS (BMAG1_LS) or HLS (HMAG1_LS) in function of TIME - HLS (HMAG1_LS) in function of BLS (BMAG1_LS) or mutually

• calculated values: - density of average losses - density of the energy of the losses

Assembly of recorded results over one region

The assembly of the computation results (LS_IRON_LOSSES_REGION_1) comprises: • stocked curves:

- instantaneous losses INST_LS_LOSSES in function of TIME • created post-processing parameters:

- density of average losses DVOL_MEAN_LS_LOSSES - density of the energy of the losses DVOL_LS_LW

• calculated values: - average losses - energy of the losses


It is possible to carry out the exploitations of the following results: • Tracing of the curves (stocked curves):

- density of instantaneous losses in a point in function of time - instantaneous losses over the regions, … in function of time - BLS or HLS in a point in function of time - HLS in a point in function of BLS in a point or mutually

• Display in gradation of color: - density of average losses over the regions, … - density of the energy of the losses over the regions, …

Remark The commands relative to the exploitation of results in the menu compute

FE quantities are presented in the chapter 6.


FLUX® 9.10 Skew slots: principles

9. Skew slots: principles

Introduction This chapter deals with the Skew slots module and answers following three

questions: • What is possible to model with FLUX? (conceivable modeling, typical

example) • How to describe the problem in FLUX ? (module specific for the

description of material media, of sources, of boundary conditions, …) • How are results analyzed with FLUX? (module specific and explanation of

results, …)


• Skew slots: general presentation • Skew slots: what FLUX models • Skew slots: description principle in FLUX • Skew slots: results analysis

Reading advice The Skew slots module comprises the different standard magnetic

applications of FLUX (Magneto Static, Transient Magnetic, Steady state AC Magnetic), as well as the possibilities of kinematic coupling and circuit coupling.

Only the specific aspects of the Skew slots module are dealt with in this section. For the other aspects, see the concerned chapters.

Another document

A complete example of a machine dealt with this module is described in Induction Motor with Skewed Rotor technical paper.


Skew slots: principles FLUX® 9.10



9.1. Skew slots: general presentation

Introduction This section deals with the Skew slots module from a general point of view.


• Interest in Skew slots • Skew slots modeling: 2D, 3D or 2½D



9.1.1. Interest in Skew slots

History At its origin, the utilization of the skew slots rotor was used in order to

provide a starting torque in the case of motors having an equal number of stator and rotor slots.

Interest Although it has been demonstrated that the start of an asynchronous machine

could be obtained by a judicious choice of the number of stator or rotor slots the swinging principle of armatures has never been abandoned in the conception of electromotors (synchronous and asynchronous).

Indeed, the swinging of an armature can minimize certain drawbacks, such as the torque pulsations, the supplementary losses and the harmonics (of torque and current).



9.1.2. Skew slots modeling: 2D, 3D or 2½D ?

Modeling in 2 or 3 dimensions

The progressive improvement of the computation power and speed of computers has permitted the utilization, as an industrial tool, of the transient analysis of motors by the finite element method.

For most of the electrical machines, a two-dimensional modeling (2D) is enough.

The three-dimensional modeling (3D) provides more precise results, but it remains very costly in terms of software resources.

Modeling in 2½ dimensions

The skew of the rotor or stator slots in the machines represents a problem for the two-dimensional calculus because of the axial variations of the magnetic field due to the changing orientation of the rotor as to the stator.

For an analytical resolution method, the swinging can be taken into consideration by means of a factor called skew factor.

As to the numerical resolution methods, it is often modeled by means of a technique called ‘Multilayers’. Equally, we speak of modeling in 2½ dimensions.





9.2. Skew slots: what FLUX models

Introduction This section deals with the Skew slots module and answers the following

questions: • What is possible to model with FLUX? • What is the operating principle?

Contents This section covers the following topics :

• Skew slots: presentation and typical example • Skew slots: principle of the method



9.2.1. Skew slots: presentation and typical example

Presentation This Skew slots module permits:

• the modeling of machines having a rotor or stator with Skew slots • starting from a 2D description of this machine

Caution: the machine compulsorily has the same depth of rotor and stator.

Interest The interest of the module consists in the facility of carrying out a quasi-3D

study or 2½ D (acc. to the next paragraph) on the basis of a 2D description.

In practice: • the geometrical description and the meshing in the 2D plan are carried out

by the user • the geometrical construction and the 3D meshing of the machine are

automatically carried out by the software on the basis of the specific data (machine depth, slots skew, …) provided by the user.

Couplings and magnetic applications

The usable applications are the standard magnetic ones of FLUX: Magneto Static, Transient Magnetic or Steady state AC Magnetic; used with a kinematic coupling (compulsory) and possibly with the circuit coupling (optional).

Example type A full example of a machine treated with this module is described in

Induction Motor with Skewed Rotor technical paper.



9.2.2. Skew slots: principle of the method

Quasi 3D (or 2½ D) computations

The computations carried out with the Skew slots module of FLUX is called quasi 3D (or 2½ D), as: • the 3D aspects of the field are taken into consideration in the thickness of

the machine • the edge effects on one edge and the other of the machine are not modeled

(the air at one edge of the machine and the other one are not represented)

Proposed methods in FLUX

The quasi 3D (or 2½ D) computation is carried out utilizing one of the following two methods (presented in details in the next sections): • the method called «multilayers 2D» • the method called «extruded 3D» (development in progress)

Principle of proposed methods

The multilayers 2D method is based on the splitting of the machine into n layers, with swinging of the layer to each other in function of the number of layers and of the slots skew angle.

The extruded 3D method is based on a volumetrical construction of the machine.

An example of a machine treated in 2D and 2½ D is presented in the figure below.

FIXE_AIR STAT_FER

ROT_AIR

ROT FER

MAGNET_1

MAGNET_2

Computation 2½ D Multilayers 2D

Computation 2 ½ D Extruded 3D




Multilayers 2D method

The multilayers 2D method is presented in details in the table below. The process starting point is the 2D description of the machine.

Phase Description

1 Construction by propagation of an assembly of n layers starting from the base faces (2D description of the machine): • by translation for the right part • by helicoidal transformation for the skewed part

2 2D computation on the set of layers (all together) 3 Computation by integration on the set of layers of of all post-

processed global quantities (torque, energy, …)

The right part (the skewed part) can be the rotor or stator of the motor (and vice versa).

An example of a rotor cut into slices is represented in the figure below.

Shaft

1

2

3

4

5

Layer no.

Skew slot

3D extruded method

The 3D extruded method is presented in details in the table below. The process starting point is the 2D description of the machine.

Phase Description

1 Construction by extrusion of an assembly of volumes starting from the base faces (2D description of the machine): • by translation for the right part • by helicoidal transformation for the skewed part

2 3D computation on the machine 3 3D analysis on the motor

The right part (the skewed part) can be the rotor or stator of the motor (and vice versa).



9.3. Skew slots: description principle in FLUX

Introduction This sections deals with the Skew slots module from the point of view of the

description in FLUX.

Contents This section covers the following topics :

• Boundaries of the study domain • Specifity of the module • Kinematic coupling • Circuit coupling



9.3.1. Boundaries of the study domain

Study domain The geometric description and the meshing of the machine are carried out by

the user in a 2D study domain.

This one is limited by: • external borders • conditions of periodicity

External borders

As to the external borders: • the infinite box technique cannot be utilized • the boundary conditions are automatically fixed by FLUX (default

boundary condition: magnetic field tangent and electrical field normal at the border)



9.3.2. Specifity of the module

Introduction The Skew slots module comprises the various standard magnetic applications

of FLUX (Magneto Static, Transient Magnetic, Steady state AC Magnetic).

From a practical point of view, the user will be able to select one of the three following applications: • Rotating machine (helicoidal model) in Magneto Static • Induction rotating machine (helicoidal model) in Steady state AC Magnetic • Rotating machine (helicoidal model) in Transient Magnetic

Specific data The specific data necessary for solving up of an application are as follows:

• Choice of method used (model: Multilayers 2D / Extruded 3D) and associated characteristics

• Choice of the mechanical assembly which presents the Skew slots (fixed mechanical set or mobile mechanical set)

• Geometrical characteristics of the skew

These data are detailed in the following sections. From the software viewpoint, these data are entered during the definition of the application.

Method and associated characteristics

Now only one computation method (or mode) is proposed. This is the 2D multilayers method (splitting in slices of the machine to be studied). The user must define the characteristics presented in the table below.

Method Characteristics

Multilayers 2D Number of layers

Extruded 3D Number of elements of the mesh line assign to the lines in the direction of extrusion

Geometric characteristics

The skew is applied on one or the other of the following mechanical set: mobile or fixed.

The slots skew on the rotor or stator parts is defined by means of the following characteristics: • elevation: distance OO’ • rotation angle: angle QO’Q’

rotation angle



9.3.3. Kinematic coupling

Introduction The Skew slots module comprises the possibilities of the kinematic coupling.

Reminder: strategy 2D / strategy 3D

By reason of the specific characteristics of the 2D (FLUX2D) and 3D (FLUX3D) solvers, the description of the mechanical set is carried out in a different manner for the 2D applications and the 3D applications.

For a 2D application solved by the 2D solver: the rotating air-gap is described by means of a mechanical set of the compressible type.

For the 2D and 3D applications solved by the 3D solver: there is no rotating air-gap, but there is a sliding surface.

Warning The Skew slots module utilizes the 3D (FLUX3D) solver. The strategy to be

adopted for the description of the mechanical assemblies is therefore that of 3D.

In practice: • creation of two mechanical assemblies: a fixed one and a mobile one • NO mechanical assemblies of the compressible type; that is NO rotating

air-gap



9.3.4. Circuit coupling

Introduction The Skew slots module comprises the possibilities of the circuit coupling.

Reminder: automatic management of symmetries/ periodicities

In order to take into consideration the symmetries/periodicities in the flux computation (for stranded conductor coils), a specific coefficient called coil coefficient is introduced in FLUX. This coefficient, automatically calculated by FLUX, takes into consideration the number and type of symmetries and/or periodicities.

The flux obtained by numerical integration over the finite element domain is multiplied by the coil coefficient in order to obtain the real flux through by the assembly of coil turns.

Except for special cases, the user must therefore describe the entire electrical circuit in order to obtain a coherent result in FLUX.

Warning 2D users have the habit of describing the circuit for the part of the machine

which is represented (1/n), while 3D users represent the circuit for a complete machine, even if, in the finite element domain, only one part of the machine is represented (1/n).

Consequently, it might be necessary to readjust the coil coefficient in order to take into consideration these differences: • if the circuit is described for 1/n of the machine, the coil coefficient is

adjusted by the user and set at 1 • if the circuit is described for the complete machine, the coil coefficient is

automatically adjusted by FLUX.





9.4. Skew slots: results analysis

Introduction This section deals with the Skew slots applications and answers the following

question: How are results analyzed with FLUX?


• Post-processing quantities: multilayers 2D method • Post-processing quantities: extruded method 3D (development in progress)

Reading advice For the interpretation of results with the standard magnetic applications of

FLUX (Magneto Static, Transient Magnetic, Steady state AC Magnetic), as well as with the kinematic coupling and the circuit coupling, refer to the concerned chapters.



9.4.1. Post-processing quantities: multilayers 2D method

Introduction The post-processable quantities in the 2D problems are of two types:

• local quantities, post-processable in all the points of the study domain • global quantities, resulting from an integration, post-processable over the


Local quantities The local quantities are those available for the concerned application

(Magneto Static 3D, Transient Magnetic 3D, Steady state AC Magnetic 3D).

The post-processing can be carried out for each of the modeled layer.

Attention, the last visible layer does not correspond to the upper limit of the machine (See figure on the right).

Shaft

1

2

3

4

5

Layer no.

Skew slot

Example Exploitation of results on a layer or on the assembly of n layers.

Global quantities

The global quantities are those available for the concerned application (Magneto Static 3D, Transient Magnetic 3D, Steady state AC Magnetic 3D): magnetic torque, magnetic energy, …

The calculated values are the average of the values calculated over the n layers.



9.4.2. Post-processing quantities: extruded method 3D

Introduction The post-processable quantities in the 3D problems are of two types:

• local quantities, post-processable in all the points of the study domain • global quantities, resulting from an integration, post-processable over the


Local quantities The local quantities are those available for the concerned application

(Magneto Static 3D, Magnetic Transient 3D, Steady state AC Magnetic 3D).

The post-processing can be carried out in the same manner as for any 3D magnetic application.

Example Exploitation of results on the upper face or on the assembly of the machine.

Global quantities

The global quantities are those available for the concerned application (Magneto Static 3D, Transient Magnetic 3D, Steady state AC Magnetic 3D): magnetic torque, magnetic energy, …




Documents

9.10 New Features