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
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, …
Seite 3 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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?
Seite 4 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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“
Seite 5 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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
Seite 6 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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 !
Seite 7 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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
Seite 8 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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.
Seite 9 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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.
Seite 10 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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
Seite 11 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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
Seite 12 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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…
Seite 13 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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
Seite 14 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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
Seite 15 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
Let‘s design an HTS 4-pole rotor!
This is essentially the design of the Siemens model machine
Seite 16 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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
Seite 17 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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
Seite 18 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
Manufacturing Rotor of HTS Model Machine
Seite 19 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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
Seite 20 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
CAD of 400kW Model Machine
HTS rotor winding
torque transmission
telemetry
air core stator winding
hollow shaft for rotor cooling
iron yoke
rotating cryostat
Seite 21 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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
Seite 22 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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 !
Seite 23 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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
Seite 24 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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
Seite 25 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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
Seite 26 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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)
Seite 27 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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
Seite 28 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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
Seite 29 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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)
Seite 30 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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
Seite 31 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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
Seite 32 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
Manufacturing of 4MVA HTS Generator
Seite 33 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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
Seite 34 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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 %
Seite 35 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
4MVA HTS Generator
CAD artist‘s view - and finally reality !
shown in presentation 2004
June 2005 in A&D LD System Test Facility
Seite 36 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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
Seite 37 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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 !
Seite 38 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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
Seite 39 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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
Seite 40 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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
Seite 41 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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 !
Seite 42 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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
Seite 43 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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 !
Seite 44 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
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 !
Seite 45 June 2008 © Siemens AG, Corporate TechnologyW. Nick, CT PS 3
Good Prospects for HTS Ship Propulsion
We should have cared better about those
compact HTS machines ...
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