EMCW 2015 Conference Program 2015 0329files.ctctcdn.com/64a4a0fb001/85500a7a-9d4c-4f56-b... · electromagnetic core. This presents additional design challenges. Practical issues related

EMCW 2015 Conference

Co-sponsored by IEEE Milwaukee

PELS, IAS/IES, PES, and GOLD Chapters

Wisconsin Convention Center

400 W. Avenue, Milwaukee, WI 53203

Wednesday, May 13, 2015

9:00am – 4:00pm

Chair

Dan M. Ionel, Regal Beloit Corp., and Marquette University

Co-Chairs

Gennadi Sizov, Rockwell Automation

Nathan Weise, Marquette University

Conference, Milwaukee, WI, Wednesday, May 13, 2015

2

Schedule

9:00 am – Electromagnetic and Thermal Design Considerations for High

Performance Servo Permanent Magnet Synchronous Motors, Gennadi Sizov,

Rockwell Automation

9:30 am – Simulation of Efficiency Maps for Synchronous Permanent Magnet

and Induction Machines, Mark Solveson and Emad Dlala, ANSYS

10:00 am – Rotational Cutting as an Alternative in the Processing of Electrical

Steel Strip, Markus Hubert and Jörg Franke, Friedrich-Alexander-Universität

Erlangen-Nürnberg (FAU)

10:30 am – Alternative Manufacturing Method for Concentrated Wound

Machines, Jason Kreidler, Regal Beloit Corp.

11:00 am – Unbalanced Magnetic Force and Vibration Characteristics of Flux

Switching Permanent Magnet Machines with and without Eccentricity, Silong

Li and Bulent Sarlioglu, University of Wisconsin - Madison

11:30 am – Rapid Estimation of Induction Machine Stator Core Losses,

Sreekanth Narayana Pillai and Ian P. Brown, Illinois Institute of Technology

12:00 pm – Break

12:30 pm – Benefits of High Thermal Conductivity Potting Materials for

Improving Electric Machine Performance, Dan Barber, LORD Corporation

1:00 pm – High-Frequency “Airgap” Windings for High-Power Density

Electrical Machines, Jonathan Martin and Kiruba Haran, University of Illinois -

Urbana Champaign

1:30 pm – Linear actuators: A Very Diverse Landscape, Bruno Lequesne,

E-Motors Consulting, LLC

2:00 pm – Modern Heat Extraction Systems for Electrical Machines –

A Review, Mircea Popescu, Motor Design, Ltd.

2:30 pm – Synchronous Reluctance and PM Assisted Motors, Steven J. Stretz,

Regal Beloit Corp.

3:00 pm – Permanent Magnets for Electric Machines: Current Performance

and Research Trends, Melania Jasinski, Heeju Choi, and Jinfang Liu, Electron

Energy Corp.

3:30 pm – Common-Mode Voltage Mitigation in Multilevel-Inverter-based

Adjustable Speed Motor Drives, Chad Somogyi and Nabeel A.O. Demerdash,

Marquette University


3

9:00 am

Electromagnetic and Thermal Design

Considerations for High Performance Servo

Permanent Magnet Synchronous Motors

Gennadi Sizov, Rockwell Automation In this presentation aspects related to electromagnetic and

thermal design of servo permanent magnet synchronous motor

design will be discussed. Servo motors are designed at the

thermal limits of the materials used in the construction of the

electromagnetic core. This presents additional design challenges.

Practical issues related to thermal-EM motor design and motor-

drive system design will be highlighted. Detailed FEA-based

motor-drive system simulation including the effects of PWM will

be used to analyze the motor-drive interaction and its effects on

thermal performance.

Gennadi Sizov received the B.S., M.S., and Ph.D. degrees in electrical

engineering from Marquette University, Milwaukee, WI, in 2005, 2007, and

2013, respectively. He is currently working as a Senior Motor Development

Engineer at Rockwell Automation, Mequon. He had previously worked with

R&D departments of A. O. Smith, ABB Low Voltage Drives, and Bucyrus

International (Caterpillar Mining). His areas of interest include the analysis,

modeling, design, and condition monitoring of electric machines and

adjustable-speed drives.


4

9:30 am

Simulation of Efficiency Maps for Synchronous

Permanent Magnet and Induction Machines

Mark Solveson and Emad Dlala, ANSYS

Accurate calculation of electric machine efficiency over a torque-

speed range is a valuable tool for machine engineers. It allows

them to better determine design trade-offs, such as reducing

magnet size and cost versus a potential reduction in efficiency or

increase in torque ripple throughout the operating speed. A

description of the simulation approach using magnetic Finite

Element Analysis will be presented for a Synchronous Permanent

Magnet machine and includes validation with a measured

efficiency map. In addition, methods for calculating efficiency

maps for induction machines will also be presented.

Mark Solveson is Lead Application Engineer with ANSYS, Inc., where he

specializes in simulation using electromagnetic finite-element analysis and

multi-domain system simulation software for power distribution, automotive,

off-road vehicle, healthcare, aerospace and renewable energy industries. Prior

joining ANSYS, he acquired eleven patents with the Research and Development

group at Eaton Corporation as well as an M.S.E.E from Marquette University.


5

10:00 am

Rotational Cutting as an Alternative in the

Processing of Electrical Steel Strip

Markus Hubert and Jörg Franke, Friedrich-Alexander-

Universität Erlangen-Nürnberg (FAU)

Improving the efficiency in production is always the aim. In many

applications where progressive stamping approaches the

technological limits, rotational cutting is successful. Relevant

applications to name are the processing of paper, card boxes,

packaging and simple perforated steel profiles. The main limiting

factors of the stamping technology are the accelerations and

decelerations in sheet feed and stamping motion. In contrast

rotational cutting is a continuous process that leads to greater

speeds and higher output. While performing the electrical steel

strip between two cylindrical tools in stamp and die arrangement,

the laminations are cut out. Rotational cutting in the manufacture

of laminations is a great challenge and researched at the Bavarian

Technology Center for Electric Drives at the FAU. This

presentation provides the main technological differences

between progressive stamping and rotational cutting regarding

the process structure. Furthermore the geometric and technical

parameters of the rotational cutting process are described

mathematically. Finally, a sophisticated device for the tooling

setup is introduced and the first cutting results of laminations are

presented.

Markus Hubert received a diploma in Mechanical Engineering from the Georg

Simon Ohm University of Applied Sciences Nuremberg. Since 2012 he is

working at the Institute for Factory Automation and Production Systems (FAPS)

of the Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Germany.

Jörg Franke heads the Institute for Factory Automation and Production Systems

(FAPS) at the Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) since

2009. In FAPS he focuses the research on manufacturing of mechatronic

products, starting from packaging of electronic circuits, structured metallization

of circuit carriers, surface mount technology, assembly of electric motors,

automation solutions and ending with engineering, planning and simulation of

complex mechatronic systems. Previously, Prof. Dr.-Ing. Franke held different

management positions with global responsibilities e.g. at McKinsey&Co, Robert

Bosch GmbH, ZF AG, Schaeffler AG and ABM Greiffenberger AG.


6

10:30 am

Alternative Manufacturing Method for

Concentrated Wound Machines

Jason Kreidler, Regal Beloit Corp.

As the price and availability of rare earth materials came into

question an effort into maximizing the use of this material in a

PMAC machine became critical. In order to achieve power density

in the stator which matches the power density of rare earth

materials higher slot fills needed to be achieved. To meet these

criteria Regal Beloit embarked on a project to construct an

automated stator manufacturing line capable of maximum slot

fills. This paper will discuss the benefits and challenges of design,

and implementation of an automated stator line.

Jason Kreidler manages the Enabling Technology Team for Commercial and

Industrial Motors at Regal Beloit Corporation. Jason started his career in

electric motors 19 years ago working in various development engineering roles.

He received his degree in Mechanical Design form Lakeshore Technical College

and is currently enrolled at University of Wisconsin – Stout studying Business

Management.


7

11:00 am

Unbalanced Magnetic Force and Vibration

Characteristics of Flux Switching Permanent Magnet

Machines with and without Eccentricity

Silong Li and Bulent Sarlioglu, University of Wisconsin -

Madison

The flux switching permanent magnet (FSPM) machine, which has

both magnet and armature winding on the stator, and has a

salient pole rotor similar to switched reluctance machine (SRM),

become very popular in recent years. The research on FSPM

machines is mainly focused on electromagnetic performances

analysis, but the mechanical and structural analyses are very

limited. However, the salient pole rotor structure of FSPM

machine is prone to produce high vibration and acoustic noise.

Additionally, manufacturing issues such as eccentricity and

bearing defect could also lead to unbalanced magnetic force

(UMF) and vibration in the FSPM machine. In order to fill this

knowledge gap, this presentation/paper will investigate the UMF

and vibration characteristics of FSPM machine with and without

eccentricity. Simulations with 2D and 3D FEA will be presented. Silong Li received the B.S. degree in electrical engineering & automation from

Xi’an Jiaotong University, Xi’an, China in 2011, and the M.S. degree from

University of Wisconsin Madison, in 2014. He is currently working toward the

Ph.D. degree in electrical and computer engineering at the University of

Wisconsin-Madison. His research interests include novel permanent magnet

machines design, and high performance electric machine drives.

Bulent Sarlioglu is a Professor at University of Wisconsin–Madison, and

Associate Director of Wisconsin Electric Machines and Power Electronics

Consortium (WEMPEC). He received the Ph.D. degree from University of

Wisconsin–Madison. Dr. Sarlioglu spent more than ten years at Honeywell’s

aerospace division, most recently as a staff systems engineer, earning

Honeywell’s technical achievement award in 2003 and an outstanding engineer

award in 2011. He contributed many internally or externally funded R&D

programs including Boeing Sonic Cruiser and 7E7 and realization of many

technology development programs including Airbus A350 and A380. Dr.

Sarlioglu is the inventor or co-inventor of sixteen US patents. His current

research interests include novel electric machines, high-speed electric

machines, and wide bandgap device based power electronics.


8

11:30 am

Rapid Estimation of Induction Machine Stator

Core Losses

Sreekanth Narayana Pillai and Ian P. Brown, Illinois

Institute of Technology

An induction machine finite element analysis technique for the

estimation of stator core losses using a series of magneto-static

simulations is presented. This technique unites two previously

proposed simulation procedures: one for determining the average

torque in the induction machine under field oriented conditions

and another for the rapid analysis of synchronous machine core

losses. Stator winding and sinusoidally distributed rotor bar

currents are imposed at discrete rotor positions where a

magneto-static finite element solution is computed. Electric and

magnetic symmetries are exploited to reconstruct or approximate

the stator flux density waveforms. From the reconstructed or

approximate waveforms the stator core loss is estimated.

Sreekanth Narayana Pillai graduated with a Bachelors in Technology in

Electrical and Electronics Engineering from Mahatma Gandhi University,

Kottayam, Kerala, India in 2008. He is currently pursuing a M.S. in Electrical

and Computer Engineering at the Illinois Institute of Technology.

Ian P. Brown received the B.S. degree in engineering from Swarthmore College,

Swarthmore, PA, USA, in 1999 and the M.S. and the Ph.D. degrees in electrical

engineering from the University of Wisconsin, Madison, WI, USA, in 2003 and

2009, respectively. Since 2012, he has been with the Illinois Institute of

Technology, Chicago, IL, USA. Previously, he was with the Corporate

Technology Center, A. O. Smith Corporation, Milwaukee, WI, USA. His main

research interests are high-performance electrical drives and the design of

electric machines.


9

12:30 pm

Benefits of High Thermal Conductivity Potting

Materials for Improving Electric Machine Performance

Dan Barber, LORD Corporation

Thermal losses in electric machines are well-known to degrade

power output and efficiency, and excess heat or hot spots can

reduce reliability of motors and shorten their lifetime. Good

thermal management in electric machines and their power

electronic drives can minimize losses, particularly copper losses,

and yield improved performance, reliability and efficiency. Recent

work has shown that encapsulation of the stator or overmolding

the end windings with high thermal conductivity (3 W/m∙K),

electrically insulating silicone material can decrease the average

electric machine coil temperatures by 30 to 50 degrees Celsius

and can provide a more even temperature distribution

throughout the machine. These results will be reviewed, and

more recent data using silicone and epoxy materials with thermal

conductivity ranging from 1 to 4 W/m∙K will be presented.

Performance data will include temperature average and

distribution at various operating conditions, copper losses and

efficiency determination, and available reliability test data.

Thermal simulation results will be presented that show good

agreement with experiment and that predict lower rotor

temperatures as an additional benefit of the thermally conductive

stator potting. Dan Barber received his B.S. in Chemistry from Furman University, Greenville,

SC, and his Ph.D. in inorganic chemistry from the University of Virginia,

Charlottesville, VA. He joined LORD in 2005 as a research & development

scientist developing magnetorheological fluids and since then has led customer

technical interactions for various global business development projects. He is

currently a Staff Scientist in Open Technology Innovation working to develop

new solutions for customer needs related to thermal management, electronic

materials and structural adhesives.


10

1:00 pm

High-Frequency “Airgap” Windings for High-Power

Density Electrical Machines

Jonathan Martin and Kiruba Haran, University of Illinois -

Urbana Champaign

The University of Illinois is currently working on high-power

density megawatt-scale electrical machines for aerospace

applications. One key feature is the use of very high-frequency

armature windings ranging from 3 kHz to 10 kHz. The high

frequency currents, especially in an “airgap”-winding

configuration pose significant AC loss challenges, and thereby

require highly stranded Litz conductors. This presentation will

discuss detailed AC loss calculations that have been performed, as

well as review results from manufacturing trials and bench tests

carried out to refine the machine design.

Jonathan Martin graduated with a B.A. in Physics from Colgate University in

2014. He is currently pursuing a M.S. degree in electrical engineering under

Professor Kiruba Haran with focus on electric machines at the University of

Illinois, Urbana-Champaign.

Kiruba Haran obtained a BS in Electrical Engineering from OAU, Nigeria, in

1994, and a PhD in Electric Power Engineering from RPI, Troy, NY in 2000. He is

currently an Associate Professor and Associate Director of the Grainger Center

for Electric Machinery at the University of Illinois at Urbana-Champaign. He

moved to UIUC in 2014 after 13 years at GE Research. At GE, Dr. Haran was the

manager of the research group developing advanced electrical machine

technology for all of GE’s industrial businesses, including Wind, Oil & Gas,

Aviation, Transportation and Energy Services. Dr. Haran has 35 US patents,

several more global patents, and has published 20 journal papers and given

dozens of conference presentations. He is a registered PE in NY, and is a fellow

of the IEEE.


11

1:30 pm

Linear actuators: A Very Diverse Landscape

Bruno Lequesne, E-Motors Consulting, LLC

Many mechanisms ultimately require linear motion, from fuel

injection to aircraft launches. The presentation will provide an

overview of the many technical solutions developed for such

applications. An important distinction will be made between

devices where the motive force is perpendicular to the airgap, as

opposed to parallel. This distinction exists in the rotary world as

well but is seen much less frequently. For linear actuation it

generally separates shorter from longer motions. For longer

travels, the option of retaining a rotary machine, paired with a

rotary-to-linear mechanism has many advantages in a number of

cases. Ultimately, choosing one approach over another involves

both a deep understanding of electromagnetic force generation

as well as a system approach.

Bruno Lequesne received the Certified-Engineer degree from the Ecole

Supérieure d'Electricité (CentraleSupélec), France, in 1978, and the PhD degree

in electrical engineering from the Missouri University of Science and

Technology, Rolla, MO, USA, in 1984. He worked for 30 years in the automotive

industry with General Motors, Delphi, and Eaton on transportation

electrification research before starting his own consultancy, E-Motors

Consulting, LLC, in 2014. Dr. Lequesne holds 49 patents with 4 more pending,

primarily on sensors, linear actuators, and automotive applications. He is the

recipient of ten Best Paper Awards, seven from the IEEE Industry Applications

Society (IAS), and three from the Society of Automotive Engineers. He was

elected an IEEE Fellow in 1997. He is also past president (2011-2012) of the

IEEE IAS and is currently on the steering committee of the IEEE Transportation

Electrification Community.


12

2:00 pm

Modern Heat Extraction Systems for Electrical

Machines – A Review

Mircea Popescu, Motor Design, Ltd.

The thermal stress on the electrical machines is created by the

losses dissipated in the system which will heat different

components of the machine, like windings, rotor cages, magnets,

and needs to be dissipated. One can thermally protect the

electrical machines by reducing the local losses, i.e., the induced

eddy-current losses in the electrical conducting regions, iron

cores, magnets, retaining sleeves, and/or using an efficient

cooling system. Depending on the application, cooling systems

can be employed with natural convection (totally enclosed non-

ventilated), forced convection (air or liquid cooling), or radiation

cooling (in the case of electrical machines, operating in vacuum

environment). Heat can be extracted through conduction,

convection (natural and forced) and radiation. The thermal

management of electrical machines is a 3-dimensional problem

which requires complex heat extraction phenomena to be

addressed; e.g., heat transfer through complex composite

components such as the wound slot, temperature drop across

interfaces between components and complex turbulent air flow

within the end-caps. This study presents modern various solutions

for an efficient heat extraction or thermal management of the

electrical machines.

Mircea Popescu is the Vice President of Engineering for Motor Design, Ltd., a

software and consultancy company headquartered in the UK and with offices in

the US, and has more than thirty years of engineering experience. Earlier in his

career, he was with Helsinki University of Technology (now Aalto University) in

Finland and with the SPEED Lab at University of Glasgow, UK. Dr. Popescu

published more than one hundred papers and his publications have received

three IEEE best paper awards. His consultancy contributions for industry are

incorporated in many state-of-the-art products. Current major projects include

electrical machines and drives for hybrid/electrical vehicles, and formula-e

racing cars. An IEEE Fellow, Dr. Popescu is the Chair of the IEEE Industry

Application Society (IAS) Electrical Machines Committee and a Distinguished

Lecturer for IEEE IAS Region 8.


13

2:30 pm

Synchronous Reluctance and PM Assisted Motors

Steven J. Stretz, Regal Beloit Corp.

Synchronous reluctance machines and their PM assisted varieties,

which incorporate magnets in the flux barriers, are being

considered for variable speed power electronic converter -fed

applications. The presentation will cover fundamental concepts,

optimal computer-aided design, and practical demonstrations of

the technology. The advantages of employing PM assisted rotor

topologies with cost competitive ferrites will be quantified in

terms of improved power factor, specific power, and efficiency.

Numerical and experimental results for a 10hp 1,800rpm typical

rating will be discussed.

Steven J. Stretz is Chief Engineer with Regal Beloit Corporation and is based in

Grafton, WI. He received the B.S. degree in electrical engineering from the

University of Wisconsin Milwaukee followed by post graduate studies in

Engineering Management. Mr. Stretz has more than 40 years of experience in

various engineering and management roles in the electric machine industry and

introduced to manufacturing many new products. He has been a working

member of IEEE and NEMA involved in the development of standards for

electric machines.


14

3:00 pm

Permanent Magnets for Electric Machines:

Current Performance and Research Trends

Melania Jasinski, Heeju Choi, and Jinfang Liu, Electron

Energy Corp.

In this presentation we will review the performance of permanent

magnets for electric machine applications and discuss the trade-

off between the performance and cost, density of magnetic flux

and thermal stability, etc. We will also present lesser known

magnet grades, such as ultra-high temperature Sm-Co magnets,

temperature compensated Sm-Co magnets, sequentially

laminated magnets, and new grades of Nd-Fe-B magnets. The

latest research activities in the US, recently funded by the

Advanced Research Projects Agency-Energy, as well as worldwide

major research programs on rare earth and non- rare earth

magnets and their objective-accomplishment status, will be

discussed in the context of preparing the engineering community

for possible new generations of permanent magnets.

Melania Jasinski is the Manager of Process Technology at Electron Energy

Corporation. She received her PhD in Physics in 2003, from A.I.Cuza University,

while also working as a researcher at the National Institute for Research and

Development, in Iasi, Romania. She joined EEC in 2007, leading the R&D group

in material research activities under more than a dozen government and

industry funded projects. Dr. Jasinski co-authored more than 50 peer-reviewed

papers and 8 patent applications and serves as a reviewer for several journals

and government research-funding agencies.


15

3:30 pm

Common-Mode Voltage Mitigation in Multilevel-

Inverter-based Adjustable Speed Motor Drives

Chad Somogyi and Nabeel A.O. Demerdash, Marquette

University

The three-level neutral-point-clamped (NPC) ASD is a popular

multilevel inverter topology used in low- and medium-voltage

regenerative/non-regenerative motor drive applications because

of its ability to produce lower levels of total harmonic distortion

(THD) and withstand higher voltages while preserving rated

output power compared to two-level ASDs. While multilevel PWM

schemes to mitigate or eliminate CMV have been proposed in

literature, many of these methods do not consider real-world

conditions and requirements, such as switch dead-time, polarity

reversals in the output line voltage, etc., for safe and efficient

operation of three-level ASDs and motor loads. This paper will

review the harmful effects of CMV and introduce several carrier-

based multilevel PWM strategies that reduce and/or eliminate

CMV produced by three-level NPC motor drives. Simulation and

experimental results based on a laboratory scale 7.5 kVA three-

level NPC ASD will be presented to verify the introduced PWM

strategies for mitigating the CMV in ASDs. Chad Somogyi received a B.S. in electrical engineering technology from

Milwaukee School of Engineering University, Milwaukee, Wisconsin in 2012. He

is currently working on his M.S. in electrical engineering at Marquette

University, with a research focus on common-mode voltage mitigation for

multilevel-inverter-based adjustable speed motor drives.

Nabeel A. O. Demerdash has pioneered since the 1970’s finite element

techniques for low frequency electromagnetics and their applications for

electric machines and drives. In the 1980’s as part of a NASA project he

designed and built one of the very first rare-earth brushless DC motor drives for

electric vehicles. He has published more than 100 IEEE Transactions papers,

and is the winner of the 1999 IEEE Nikola Tesla Technical Field Award, which

represents the highest IEEE recognition for work on electrical machine topics.

Professor Demerdash is an IEEE Life-Fellow, a member of the American Society

of Engineering Education, the Sigma Xi, and the Electromagnetics Academy.


16

EMCW 2015 Best Student Paper Award

Papers authored and presented by a student will be considered

for the EMCW 2015 Best Student Paper Award. Selection will be

made based on the audience’s secrete vote. The award consists of

a certificate and a $250 honorarium.

Conference Organizing Committee

Dan M. Ionel, EMCW 2015 Conference Chair, is Chief Engineer with Regal

Beloit Corp. and Research Professor with Marquette University in Milwaukee,

WI. After completing postdoctoral research with the SPEED Laboratory,

University of Glasgow, he worked in industry and academia in the UK and the

US. Dr. Ionel was granted more than thirty patents and has published more

than one hundred papers, including two winners of IEEE IAS best paper awards.

He is the Editor-in-Chief of the Electric Power Components and Systems

Journal, an IEEE Fellow, the Chair of the IEEE PES Electric Motor Subcommittee,

and of the IEEE Milwaukee Power Electronics Chapter.

Gennadi Sizov, EMCW 2015 Conference Co-Chair, received the B.S., M.S., and

Ph.D. degrees in electrical engineering from Marquette University, Milwaukee,

WI, in 2005, 2007, and 2013, respectively. He is currently working as a Senior

Motor Development Engineer at Rockwell Automation, Mequon. He had

previously worked with R&D departments of A. O. Smith, ABB Low Voltage

Drives, and Bucyrus International (Caterpillar Mining). His areas of interest

include the analysis, modeling, design, and condition monitoring of electric

machines and adjustable-speed drives.

Nathan Weise, EMCW 2015 Conference Co-Chair, is an Assistant Professor

with Marquette University in Milwaukee, WI. He received the Ph.D. from

University of Minnesota, Minneapolis, MN and worked in industry as an

electrical engineer at Cummins Power Generation and General Electric Global

Research. Before joining Marquette University in 2014, he was an Assistant

Professor at the University of Maine, Orono, ME. His current interests include

power electronics, electrification of transportation, control of renewable

energy sources, motor drive systems, wave energy converters, HVDC, and grid

connected converters.


17

http://www.coilwinding.org/

http://electricalmanufacturing.org/

EMCWA Mission Statement

The Electrical Manufacturing and Coil Winding Association, Inc. is

a non-profit voluntary organization dedicated to the furtherance

of the conception, research, design, manufacturing, marketing

and use of electrical products. The association shall provide an

array of educational opportunities which will enhance the

development, knowledge and use of electrical technology and

products. Providing a forum to display products, ideas, and

innovations is a key element in the educational process.

Ver. 2015 0329

Documents

EMCW 2015 Conference Program 2015 0329files.ctctcdn.com/64a4a0fb001/85500a7a-9d4c-4f56-b... · electromagnetic core. This presents additional design challenges. Practical issues related