PERMANENT MAGNET MATERIAL PROPERTY
CRITERIA IN WIND POWER APPLICATION
14th of June 2012
1
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CONTENTS
The Switch
Turbine technology
Generator types
PMG rotor designs for WP
Demagnetization risk
Usage of magnets in different generator types
Other requirements for magnetic circuit in
generators
Cost reduction options
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BUSINESS
“We are setting the standard for modern drive train
technology. Currently, we are in close to 20 wind
turbine designs and are building the capacity for them.”
– Jukka-Pekka Mäkinen,
President and CEO
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THE SWITCH AREAS OF
OPERATION
WIND POWER
EMERGING BUSINESSES
Solar & fuel cell converters
Variable speed genset drive trains
Industrial electrical drive trains
THE SWITCH DRIVE™
The soul of every reliable wind turbine
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LOCATIONS
The Switch
Headquarters
Vantaa, Finland
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Silkeborg,
Denmark
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Hudson, NH,
USA
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Vaasa, Finland
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Gumi-City,
Korea
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Beijing, China
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Lu’an, Anhui,
China
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Barcelona, Spain
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Hamburg,
Germany
Medium Size Electrical
Machines
Deyang, Sichuan, China
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Lappeenranta,
Finland
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Hangzhou, China
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Chennai,
India
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Hong Kong, China
WIND TURBINE
Turbine automation
• Yaw control
• Pitch control
• Speed control
• Torque control
Electric drive
• Traditional wind turbine:
Gear + high speed IM
• Direct drive without gear
Source:http://windeis.anl.gov/guide/basics/turbine.html
AN EXAMPLE
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
Cooler
Generator
Automation
Anemometer
Coupling
Mechanical brake
Gearbox
Main shaft
Yaw gear
Machine bed
Main bearing
Hub control
Pitch controller
Blade
Source: Vestas V82-1.65 MW broshure
TYPICAL POWER CURVE:
V82-1.65 MW
Source: Vestas V82-1.65 MW broshure
GENERATOR OPTIONS
Directly net coupled induction machine
Double fed induction generator
Electrically excited synchronous generator
Permanent magnet synchronous generator
PRODUCT PORTFOLIO
POWER
5.9 MW/1100rpm
6.0
5.6 MW/1200rpm
5.0
4.25 MW/16 rpm
FD: 3.2 MW/346 rpm
4.0
3.3 MW/136 rpm
3.0
2.0
1.0
1.65 MW/17 rpm
3.3 MW/1500 rpm
3.3 MW/365 rpm
3.3 MW/13 rpm
3.2 MW/414 rpm
1.65 MW/150 rpm
1.65 MW/120 rpm
3.3 MW/1000 rpm
2.7 MW/1000 rpm
2.7 MW/1500 rpm
2.2 MW/1000 rpm
2.2 MW/1500 rpm
1.6 MW/1000 rpm
1.6 MW/1500 rpm
1.1 MW/1000 rpm
1.1 MW/1500 rpm
1.4 MW/292 rpm
SPEED
LOW
MEDIUM
1000
1500
GENERATOR CONSTRUCTION
Options
Machine
construction
Turbine
technology
Cooling
arrangement
Magnet
assembly
Winding
Voltage
Inner rotor
Low-speed/
Direct driven
IP 54
Air/air
Surface-mounted
magnet modules
Random
wound
Low voltage
Mediumspeed
IP54
Air/water
Surface-mounted
magnets
Form
wound
Medium
voltage
High-speed
IP23
Embedded
magnets
Litz
wire
Outer rotor
HS
MS
12 I © The Switch 2011
DD
In standard platform
Option
DIRECT-DRIVE GENERATORS
Efficiency (%)
96
94
92
• Increasing efficiency towards partial loads
90
• Best overall drive-train efficiency
88
86
• No gearbox, no fast-rotating parts
0
1000
2000
3000
kW
→ Increased reliability
• Highest torque density due to large cooling area in active parts
• Mechanical interface design for turbine in co-operation with turbine
designer
• Generator bearing can act as a turbine main bearing
• Large generator size due to high torque
• Possibility to integrate break system to generator construction
4000
5000
DIRECT-DRIVE GENERATORS
Outer rotor generators
3.3 MW, 13 rpm direct-drive outer rotor
generator. Frame size: 3000
1.65 MW direct-drive outer rotor
Generator Frame size: 2250
DIRECT-DRIVE GENERATORS
Down wind generators
4.25 MW, 16 rpm direct-drive generator in test setup
Frame size: 3150
GEARED GENERATORS
Medium speed generators
• 1- or 2-stage gearbox
• Generator speed is usually 100 to 500 rpm
• Typically flange mounting between generator
and gearbox
• Integrated drive train with a simplified
structural design (FusionDrive®)
• Lowest nacelle weight
• Improved total turbine cost effectiveness
GEARED GENERATORS
High-speed generators
• 1000 to 2000 rpm speed range with 3-stage gearboxes
• Small generator size, high efficiency
• Stand-alone component
→ Can be used with different turbine designs
• Rotor has embedded magnets
→ Well protected against centrifugal forces and corrosion
• Typically leg-mounted
• Air-to-air or air-to-liquid cooling
• Easily possible to replace existing DFIG without changing nacelle layout
• Requires heavy gearbox with high-speed shaft
GEARED GENERATORS
High-speed generators
2.2 MW, 1500 rpm
Frame size: 500
5.9 MW, 1100 rpm
Frame size: 710
ROTOR DESIGN
Surface mounted magnets
• For direct –drive
• and medium-speed generators:
• → Allow the maximum power to be captured from the magnet
• Maximum flux in air gap
• Typically protected with a module construction (hermetically sealed)
• Must be firmly fastened against centrifugal forces
3.3 MW medium-speed
generator
Magnet modules in an outer rotor
direct-drive generator
ROTOR DESIGN
Embedded magnets
•
•
•
•
For high-speed generators:
Magnets are built inside a sealed corrosion-resistant metal enclosure
No threat due to centrifugal forces
Hermetic sealing provides protection from the environment
(rotor is impregnated)
• Tangentially multiple magnets / pole
3.3 MW high-speed generator rotor
Magnet grade
Most critical raw materials:
Neodymium (Nd) mainly to increase remanence flux (together with
Praseodym; PrNd ~50 €/kg (5/2012)
Dysprosium (Dy) to increase coersivity (demag. resistance); FeDy
~550 €/kg
Terbium (Tb) to increase coersivity; ~1200 €/kg
Grade
Dy
PrNd
Tb
Typical use
4X SH
3...4 %
26...27 %
0
Direct drive
40 UH
5...6 %
25...26 %
1...2 %
Medium speed
38 EH
3...4 %
24...25 %
2...3 %
High-speed
Raw material sources outside China
Case study with nine mines / known recourses
Mine
1
2
3
4
5
6
7
8
9
Country
Australia
Australia
Canada
Canada
South Africa
Greenland
Australia
USA / Ca
USA / Wo
Location
Dubbo
Nolans
Nechalacho
Hoidas lake
Steenkampakraal
Kvaenefjeld
Mt. Weld
Mt. Pass
Bear Lodge
Company
Alkane Recources Ltd
Arafura Recources Ltd
Avalon Rare Metals Inc
Great Western Minerals Group
Great Western Minerals Group
Greenland Minerals & Energy Ltd
Lynas
Molycorp Minerals LLC
Rare Element Recources Ltd
RE recources in 9 mines (kton):
Pr
Nd
Tb
Dy
Sum
3 MW PMG consumes RE-materials (not magnets):
- Direct Drive
800 kg
- Medium speed 130 kg
- High speed
80 kg
Generator capasity built with 9 mines recources:
PrNd
Dy
DD
8980
2628
MS
56125
16425
HS
114292
12483
GW
GW
489
1606
20
104
2220
(E-3) Tesla
HS
250
Demagnetization
0
CURVE C2D_13
Flux density / Normal component
Path_5
Time (s.) : 0,038
Magnet grade is selected based on the demagnetization
-250
calculation
mm
TOIM_P12_NL
100
200
External field
300
(E-3) Tesla
300
Rotor temperature
MS
Typical factors
200
100
CURVE C2D_5
Flux density / Normal component
Path_1
Time (s.) : 26,1E-3
Rated frequency / speed (HS worst – DD easiest)
0
Air-gap length
-99,999
Tangential tention
-200
mm
3PH_SC_HOT
0
50
100
(E-3) Tesla
700
DD
600
500
CURVE C2D_232
Flux density / Normal component
Path_1
Time (s.) : 184,799999E-3
400
300
200
mm
0
50
100
Critical level 100 °C
Demagnetization risk
Typical requirements (worst case):
Max ambient temp ~45 °C => max rotor temperature
Min 12 m/s wind
Short circuit in terminal box
Against present design criteria says:
Places where the above conditions is even theoretically possible are few
A short circuit in terminal box or winding would destroy the machine anyway. In
case of a short circuit further away cable impedance will restrict the sc-current and
field
Statistical reasons
Other typical requirements in WP
Life time 25 years (< 2% flux reduction)
< 1% ( or even < 0.5 %) cogging
Magnet shape
Skewing
Rotor
Stator
Forming Air-gap shape
Asymmetry
Rotor poles
Stator slots
IP54 construction (rotor typically requires air circulation for cooling)
Sea environment (salt)
REDUCING MAGNET GRADE (COST) BY
DIRECT COOLING WITH INPUT FILTER
Typical requirement IP54 =>
Water jacket (+ air circulation)
Internal air circualtion + heat exchanger
Replace HEX with Goretex filter and exhaust pipe
10...15 °C cooler air for cooling => upgrade or lower grade
magnets
Is applicable for symmetric or asymmetric cooling arrangement
Filter has to be changed every 3...5 years
Is not real IP54
Requires change of thinking
EXAMPLE ON DE-RATING
•
Normally generator is designed for
worst possible operating conditions
that occur very rarely (blue circle =
rated point)
•
By lowering the design temp by 10
°C, generator would be able to deliver
3.3 MW (green circle = rated point)
•
How often the ambient really exceeds
40 °C while there is nearly full wind?
In europe once a year?? Now the
generator designs are according to
such conditions
2.5 MW HS-turbine alternatives
140
120
Power [%]
100
80
Current
design
60
Increased
power
40
20
0
0
10
20
30
40
Ambient temperature [°C]
50
60
•
Each drop of ~20 °C enables using
one grade cheaper magnets
Thank You
Äyritie 8 C
FI-01510 Vantaa, Finland
Tel +358 20 783 8200
Fax +358 20 783 8570
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