HTS Rotating Machines - Prizztech Oy · PDF fileCooling System for Model Machine Cold Head ... the design of the Siemens model machine ... Measured Electrical Data Siemens HTS demo

Copyright © Siemens AG 2006. Alle Rechte vorbehalten.

Corporate Technology

HTS Rotating MachinesBasicsConcepts Siemens DemonstratorPossible applicationsDevelopments worldwide (+Siemens)Challenges to be overcome

Dr. Wolfgang Nick

Siemens AG, Corporate Technology,

Power & Sensor Systems

[email protected]

European Summer School, Pori, Finnland, 2008

Seite 2 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3

BasicsBasics

Electrical machines: motors and generators (+ transformers)

electrical power mechanical power

extremely large range: ~ mm to 10m, µW to 1000 MWslow, high force/torque high speedalmost everywhere !

basic principle: Lorentz force force / length = current I x induction B+ forces on magnetic dipoles, ferromagnetic parts …

different configurations: rotating vs. linear, cylindrical vs. plane, …


Utilization of Superconductor

How to use superconductivity for electric machines? what machines?

Which properties to utilize?

Machine concepts: - completely innovative designs(based on specific sc material behaviour),

or- “improved conventional designs“(high current density, zero losses)

Meissner effectcoil = permanent magnetflux pinningdc current capacityhigh current density...

low temperature rangerequiring unefficient coolingac lossesmechanical limits (esp. HTS)costly...

Which create difficulties?


Overview of Machine Concepts

Hysteresis machine

Induction machine

No good superconducting solution!

Synchronous machine = standard for efficient, high-power application(more specific: electrically excited, radial flux synchronous machine)

Reluctance machine

Pictures taken from:

A.Sfetsos et al. “Flux Plot Modelling of Superconducting Hysteresis Machines“


Induction Machine

rotor needs no coils, just a conducting layer, at least “squirrel cage“

slower (rotor) speed than rotating stator fieldsinduced currents, rotor magnetizationinteract with driving stator fields to generate torque

advantage: very simple rotor

at first: seems easy to replace cage by sc structure

but: ac conditions, lossescryogenic cooling required no longer simple !

“work horse“ for most applications

B stator


Synchronous Machine

rotor with DC excitation windingrotates synchroneously in AC generated stator field

2 types:a) cylindrical rotor machineb) salient pole machine:

b) is well suited for implementation of (flat) HTS coils !


Calculation of Torque and Power

torque / length ~ n*Istat * Br * R ~ A1*R * Br * R

power = torque * speed~ A1 * Br * R² *L * speed

power/volume ~ A1 * Br * speed

How can we increase this?

Br : radial magnetic inductionof rotor at position of stator

A1 [A/m]: ~stator current per circumference


Comparison: Conventional Design

Stator core Stator winding (Cu)

Rotor iron Rotor winding (Cu)

Stator tooth

Laminated stator core with teeth

Stator copper winding

Rotor copper winding

B = 1 T

A1 = 1 p.u.

P = 1 p.u.

(1:stator 2:rotor)

Losses:

PCu1 = 1 p.u.

PCu2 = 1 p.u.

PFe = 1 p.u.


Let‘s switch to HTS Design !

Stator core Stator winding (Cu)

Rotor iron Rotor winding (Cu)

Stator tooth

HTS winding

Laminated stator core without teeth

Stator copper winding

Rotor HTS winding

B = 2 T (-x)

A1 = 2 p.u.

P ≈ 4 p.u. (-y)

Losses:

PCu1 = 2 p.u.

PCu2 = 0 p.u. + PCooling

PFe = 0.6 p.u.


Task of Siemens Model Machine

Goals to be demonstrated:high power density at improved efficiency

But is it technically achievable ?

Check feasibility:

rotating HTS windings

robust rotor cooling system

air gap stator winding

interaction of innovative componentstest in different configurations…

goals of 400kW HTS model machine

1999 – 2002funded by BMBF


Mechanical & Cryogenic Concept

• rotor = rotating cryostat

• torque transmission (cold warm) with minimum heat influx

• stator: without iron teeth, iron yoke, and housing

• cooling via hollow shaft (needs a rotating seal)

drive end

vacuum insulation

room temperaturecooling

magnetic air gap


Cooling Options

Needed: High current density in large background field HTS < 40KPossible coolants: Neon - Hydrogen - Helium gas or liquid

Tliquid at 1bar 27K 20K > 4.2K =4.2KProblem:Transfer of cooling power from (ext.) refrigerator to rotating HTS coilsAvail. cooling modes: thermal conduction

forced convectionheat pipe / thermosiphon

Avail. refrigerators: LHe liquefiers GM refrigerators (1-/ 2-stage)Stirling machinePulse Tube Refrigeratorothers…


Capability of Neon Thermosiphon (Heat Pipe)

Copperat RT

10 cm²

L=1 m

20°C

30°C

ΔT =

10

K4

W 40 W

heat pipe

liquid/gaseousNeonat ~26K

1 cm²

L=1m or more

ΔT <

0,5

K

26K +x

26,0 K

Evaporation

Condensation

Thermosiphon

1000 times

more powerful !!!

x=ΔTcond

+ΔTevap


Cooling System for Model Machine

Cold Head

Condensor

Evaporator

Thermosiphon(Heat Pipe)

• GM Cryocooler 40W @ 25K (commercially avail.: up to 100W)

• heat transfer by thermosiphoninto center of rotor

• Cooling medium: Neonboiling point ~ HTS operation point

• modular• robust• reliable

Compressor

Rotating Feedthrough


Let‘s design an HTS 4-pole rotor!

This is essentially the design of the Siemens model machine


Cross Section in FE Analysis

distribution of |B | in coil cross section

stack ofHTS pancake coils

resulting deformation (enlarged) due to rotation and EM forces

prestressed bandage


Winding of Rotor Coils

100 150 200 25030

35

40

45

50

Charge NST 90607(SIE#56)

I C in

A

Länge in m

100 150 200 2500,15

0,20

0,25

0,30

0,35

0,40

Lei

terd

icke

in m

m

Länge in m

100 150 200 2502,52,62,72,82,93,03,13,23,33,43,5

Lei

terb

reit

e in

mm

Länge in m

Quality control for HTS:- performance at operating cond.- dimensions- insulation


Manufacturing Rotor of HTS Model Machine


Manufacturing Stator of HTS Model Machine

Air Gap Stator Winding

• placed into a G10-structureto take the forces/moments

• winding of coils using Litz wire to reduce eddy losses

• passages for air cooling• to be inserted into yoke • torque transmission

by G-10 support structure


CAD of 400kW Model Machine

HTS rotor winding

torque transmission

telemetry

air core stator winding

hollow shaft for rotor cooling

iron yoke

rotating cryostat


Testing

HTS machine connected to conventional load machine

operation: as motor or as generator• as generator: connected to grid or to ohmic load• as motor: driven by grid directly, or by variable frequency inverter

“short“ experiments: overload, load switching, short circuit“long“ experiments: temperatures, efficiencies, limits

Master-DriveAC-Umrichter

Q2Q1Q3

*)

••

400 V, 50 Hz

20 kV, 50 Hz20 kV, 50 Hz

Belastungs-widerstand

••

••

HTSL

Konstantstromgerät

Stromrichter

=Belastungsmaschine

••

exciterconst. current

load machine

HTS machine

resistor bank


Electrical Characteristics of Conventional Machine

0,0

0,2

0,4

0,6

0,8

1,0

1,2

0 10 20 30 40 50 60

If (A)

U,

I only small excitation voltage (no load)

large addl. excitation to overcome armature response

Open Loop / No Load

Short Circuit Characteristic

with varying powerexcitation has to be controlled !


Characteristics of HTS Machine

opposite behaviour,

compared to conventional machines !

0,0

0,2

0,4

0,6

0,8

1,0

1,2

0 10 20 30 40 50 60

If (A)

U,

I

open loop

short circuit

HTS machine

dashed lines: plot for conv. machine


Excursion: Phasor Diagrams (schematic)

U1 = Up - I1*Xd

for conventional machine: large Xd

for HTS machine with air gap armature: xd << 1

I1

I1

U1

Up

Up

I1 * Xd

I1 * Xd

phase angle φload angle θ

large Xd

→ large load angle θ

small Xd

→ small reaction → small load angle θ→ full stability

for any phase φ


Measured Electrical Data

Siemens HTS demo machine

• nominal rating: 380 kW, 1500 rpmmeasured: 450kW (short term: 600kW)

• field winding current: 49 A (HTS)

• armature: 400 V, 560 A

• total harmonic distortion: < 0.15%(conventional: ≤ 3%)

• low noise

• synchronous reactance: xd = 0.15(conventional ~ 2.3)

• however: large excitation time constant !(high inductance / low resistance of HTS winding)

• sensitive to grid harmonics

0,0

100,0

200,0

300,0

400,0

500,0

600,0

0 10 20 30 40 50 60 70

If (A)

U (

V)

open loop

measured

calculated

-400

-300

-200

-100

0

100

200

300

400

0 20 40 60 80

time (ms)

open loop voltage

very smooth


Losses and Efficiency

0

4

8

12

16

20

Asynchronmaschine400 kW, cos = 0,87

Synchronmaschine400 kVA, cos =1,0(leistungsoptimiert, hohe Stromdichte)

HTS-Modellmaschine380 kW

Ve

rlu

ste

[k

W]

Kryokühler

Läufer-Cu+ Erregung

Ständer-Cu

Zusatzverluste,Wirbelströme

Eisen

Lager+Lüfter

99 %

98 %

97 %

96 %

Efficiency

Stator

Rotor

Compressorfor Cryocooler

Induction machine400 kW, cosϕ = 0,87

conventional Synchronous machine

400 kW, cosϕ = 1,0(power optimized)

400 kW HTSModel Machine(not optimized)


Dynamic Behaviour

small load angle: 8° measured at 400 kW

0

1

2

3

0 10 20 30 40 50 60 70 80 90

Load Angle (degrees)

To

rqu

e (

rel.

un

its

)

conventional machine

HTS machine

extremely large pull-out torque ( ≈ 700%!)

very stable behaviourno problems with underexcited operation→ well suited for reactive power compensation

stable voltage (ΔU ≈ 0) subject to full (ohmic) load switching without any excitation control

-500

-400

-300

-200

-100

0

100

200

300

400

500

1120 1140 1160 1180 1200 1220 1240 1260 1280

Zeit in msU

in

V

-2000

-1600

-1200

-800

-400

0

400

800

1200

1600

2000

I in

A

Strom

Spannung


Pro‘s and Con‘s of HTS Machines

Advantages

increased efficiencymore compact, lighterbetter stability, high overload capabilityvoltage qualityreactive power capabilityless noise and vibration(no armature teeth)higher speeds possible(due to smaller rotor size)

Challenges

HTS conductor material

cryogenic cooling + vacuum technology

remove losses from high-power-density stator winding

get end-users accustomedto operation procedures

has to compete with well-optimized “cheaper“conventional products


Potential Application Fields

15 rpm 150 rpm 1500 rpm 15,000 rpm

where efficiency and/or compactness and/or dynamic performanceprovide valuable customer advantages !

high torqueship propulsion (5 -30 MW)

wind power geno's (2 -10 MVA)

industry geno's (20 -50 MVA)

high speed geno's (directly coupled to gas turbine)

utility generators (100 - 900 MVA)

industrial motors (1 -10 MW)


Application: Compact Generator for Island Grids

Idea: replace slow Diesel motor driving a large generator

by a compact gas turbine with directly coupled small, fast HTS generator

7,47

13,40

5,17

20,0

6,60

ηGen=97,3%

400rpm

MAN B&W 18PC4.2B

330t + 45t= 375 t

4,40

12,80

11,40 1,40HTS-Generator

ηGen=99,8%

4,20

6100rpm

113t + 10t= 123 t


Step: Prototype 4MVA Generator at 3600 rpm

Goals: - product size - realistic spec - testing capability

Parameters as built:

Nominal Power 4 MVASpeed 3600 rpmVoltage 6.6 kV (3~ 60 Hz) Current 350 A

Nom. Torque 10.6 kNmProtection IP 44Bearings Sleeve B.Rules GL

Dimensions incl. cryocoolersL x W x H 3.7m x 1.9m x 1.9mShaft Height 500 mmFoot Print L x W 1.9m x 1.2mTotal weight 6.9 t

compare size to conventional machine

compare efficiency

manufacturing


Manufacturing of 4MVA HTS Generator


Size Comparison for 4MVA HTS Generator

conventional machine

2600 2200

3700 1900

2700

1800

11 t

4 MVA HTS machinevs.80

0

500

weight 11 t weight 7 t

7 t


Efficiency Comparison for 4MVA HTS Generator

η = 97.0 %

0%

20%

40%

60%

80%

100%

Conventional HTS

Lo

sses

CryoRotor field ohmicStray loadArmature ohmicCoreFriction & Windage

HTS

η = 98.7 %


4MVA HTS Generator

CAD artist‘s view - and finally reality !

shown in presentation 2004

June 2005 in A&D LD System Test Facility


Worldwide Overview of Developments

GE

1995 2000 2005 2010

AmSC+ partners

Siemens

Korea

Alstom ConverTeam

200 kW1500 rpm

100 hp(+Reliance)

400 kW1500 rpm

100 hp1800 rpm

8 MW/1800 rpmSynch.Condenser

4 MW120-190 rpm

5 MWship motor

1,25 MVAHydro-Gen.

40 MVA1800 rpm

36 MW120 rpm

5 MW230 rpm

1000 hp1800 rpm

(+Reliance)

100 MVA3600 rpm

5000 hp1800 rpm

4 MVA3600 rpm

1 MW3600 rpm


Application: Ship Propulsion Motor

POD propulsion

pod-drives provide improvement of maneuvring capability and hydrodynamic efficiency!

American SuperconductorCorp. has built a 36.5MW 120rpm ship propulsion motor !for US Navy (2003 – 2007)

after a prototype 5MW/230rpm (2001-2004)

high torque machines offer best improvement in terms of dimensions and weight, however require large quantity of HTS material !

HTS machines are attractive especially for the latest trend = all-electric ships (AES),

maybe even all-superconducting solution !- HTS generator (coupled to gas turbine)- HTS transformers- HTS current limiters (connecting diff. sub-grids)- HTS propulsion machines !


HTS Ship Propulsion Motor Development at Siemens

Parameters:• power 4 MW• speed 120rpm nom.

190 rpm max• torque 320 kNm (!)

Advantages• 1/3 less mass + volume

compared to conv. technology• efficiency ~97-98%

Challenges• 30x torquecompared to 4MVA generator

• 50km HTS (from EHTS)• size, logistics...

to be completed 2009


Challenge: HTS Wire: 1G 2G

Ongoing transition to YBCO coated conductors- potential for lower cost- robust mechanical properties- additional design choices

Looks like a complicated layer structure,but tech. possibility for reduced HTS prices

to enable competitive HTS machines !

However,- performance +cost levels not yet achieved- drop-in replacement into ex. machine designs?

NOT YET DEMONSTRATED !

AmSC

SuperPower


Challenge: Excitation System

Somehow “neglected“, but vital component!

Many applications require capability to quickly control power (real/reactive)- steady operation: large current, low (~zero) voltage- ramps, changes: high voltage due to large inductance

current controlled scheme required

2 systems: “standard“ current source + slip ringsvs.

brushless excitation via rotating transformer + rot. converteradditional functionalities: - HTS coil protection

- data transmission

highly complex electronic systemon rotating frame, exposed to centr. forces

NEEDS MORE ATTENTION !

photo: AmSC 5MW


Challenge: Refrigeration for Rotor Cooling

Cryogenic refrigeration is major difference to conv. technology!goal: “invisible“ cooling system

Requirement: up to some 100W @30Kbest fit today: GM 1-stage cryocoolers

Drawbacks:- oil-lubricated compr.: large, maintenance

threat of regenerator contamination- moving displacers sensitive to vibration/shock- power ≤ 120W, sev. units in parallel- orientation dependence of compressor (+cooler)

New developments:- pulse tube refrigerators, however less. efficient- oil-free linear compressors

NOT YET TECHNICALLY MATURE !


Challenge: Develop/verify Computational Tools

More complex design precess than conventional

HTS sensitive to AC fields, +eddy currentsesp. in operation with electronic power converter

comp. short system with large airgap field fringing3D FE analysis essential

failure scenarios like short circuits !must guarantee mech. +elect. integrity(torque tube, stator teeth, damper, HTS coil)update of simulation tools: equiv. circuit models for HTS machines incl. damper cylinder

Limited experience, even less verification of calculated results!

KEY CAPABILITY TO CREATE CONFIDENCEfor CONSERVATIVE CUSTOMERS !

2900 3000 3100 3200 3300 3400 3500 3600 3700 3800 3900 40004000

3000

2000

1000

0

1000

2000

3000

4000

Zeit [ms]

3965 V

2900 3000 3100 3200 3300 3400 3500 3600 3700 3800 3900 4000-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

Läuf

ersp

annu

ng [V

]

-0.93 V

U-PhaseV-PhaseW-PhaseLäufer

2900 3000 3100 3200 3300 3400 3500 3600 3700 3800 3900 4000-1.5

-1

-0.5

0

0.5

1

1.5x 104

Zeit [ms]

-1.18e+004 A

2900 3000 3100 3200 3300 3400 3500 3600 3700 3800 3900 4000

60

80

100

120

140

160

180

Läuf

erst

rom

[A]

166.3 AU-PhaseV-PhaseW-PhaseLäufer

2900 3000 3100 3200 3300 3400 3500 3600 3700 3800 3900 4000-4

-3

-2

-1

0

1

2x 106

Zeit [ms]

-3.43e+006 Nm

-2.0973e+006 Nm

-1.8285e+006 Nm

1.6181e+006 Nm1.6137e+006 Nm

5.5817e+005 Nm

Läufer gesamtDämpferLäufer kalt


Challenge: Robust Manufacturing + Acceptance Tests

HTS machines as “advertised“ todayare manufactured in labs by top engineers and skilled workersneed to come to cost-efficient small-scale production

Also needed: accepted test procedurescustomers need to learn a minimum of SC + CT + VT...

Few activities today, but ESSENTIAL FOR MARKET SUCCESS !


HTS on its way to Power Applications...

Presently in a decisive stage:

• applications are growing models demonstrators prototypes (market)

• but at the same time getting in economic competition with conventional solutions, that have been optimized for decades !

• HTS components are to be parts of well integrated conventional systems, customers are not eager to switch to different (~ “improved“) properties.

• HTS power cables

• HTS fault current limiters

• HTS motors and generators

• HTS transformers

Requirement: Reliability, operational robustness, + easiness to use – at least as good as in todays existing technology !


Good Prospects for HTS Ship Propulsion

We should have cared better about those

compact HTS machines ...

Documents

HTS Rotating Machines - Prizztech Oy · PDF fileCooling System for Model Machine Cold Head ... the design of the Siemens model machine ... Measured Electrical Data Siemens HTS demo