Dr. Longya Xu
The Ohio State University
April, 2010
1.



2.
Introduction
Major Wind Power System Configurations
Challenges to Remain in Power Grid
Why PM Direct-Driven WTG Getting Popular
Initial Design and Performance
Analysis

Specifications and Sizing
Stator and Rotor Design
Performance Evaluation
3.
Conclusions


V Rated(V, rms)
I Rated(A, rms)
KW Rated
690
1700
2,000
Frequency
Speed
Torque (peak)
5~11Hz
10~22 rpm
850kNm
The reason for low speed at:10~22 rpm
Tip Speed of Wind Blades: vtip = 115 meters/sec.
The reason for low Frequency at:5~11 hz
Consider the electrical and magnetic loadings are relatively
constant, we have a traditional sizing equation:
Te   r D L
2
r
(1)
where subscript “r” indicates rotor related variables.
In (1) the electrical loading refers the current along the airgap in the unit of Ampere per Meter (A/M).
The magnetic loading refers the magnetic flux density
passing through air-gap in the unit of Tesla.
Te   0 D L
3
0
(2)
where subscript “o” indicates the stator related variables
and  0 a coefficient proportion to the current density and
magnetic flux density.
Here current density is in the unit of Ampere per Square
Meter and magnetic flux density in Tesla.
 0 is also closely Do/Dr related and at certain value of Do/Dr,
 0 is maximized, or D03 L minimized.
Combining (1) and (2), we have two new sizing
equations, one in terms of stator OD
Te   D L
'
0
2.5
0
(3)
another in terms of rotor OD
Te   D L
'
r
2.5
r
(4)
In sizing an electric machine, the new equations
take many variables into consideration: electrical
loading, magnetic loading, Do/Dr ratio, and slot
current density.
Sizing Results
Stator OD
3820mm
Pole #
60
Stator ID
3500mm
Slot #
288
Stack L
1300mm
Air-gap
6mm
Stack length: 1300
Airgap: 6
R1750
R1910
21x120
17.2
Stator current
density at 2
MW
4 2
78
0.77(A/mm2)
12
Stator Slot Shape
and Dimensions
Inner Rotor
Outer Rotor
Estimated Copper Losses
Pcu= 3I2R = 2.7~3 kw
Assume equal amount of iron and other losses
PFe+other = ~3 kw
Expected energy efficiency
Effi. = 97%
(1) Outer Rotor with 360 Stator Slots
In order to keep copper losses the same in
comparison, some changes are made as
follows:
• Cross-section of stator slot for conductor:
1400mm2 (288 slots) vs.
1120mm2 1400*288/360 (360 slots)
•
Current (peak) flow in each conductor:
1300A(288 slots) vs.
1040A (360 slots)1300*8/10
(1) Outer Rotor with 360 Stator Slots
XY Plot 1
Ansoft Corporation
Outer rotor3
20.00
Curve Info
FluxLinkage(WindingA)
Setup2 : Transient
15.00
FluxLinkage(WindingB)
Setup2 : Transient
10.00
FluxLinkage(WindingC)
Setup2 : Transient
Winding
Flux
Linkage
0.00
-5.00
-10.00
-15.00
-20.00
0.00
20.00
40.00
60.00
80.00
100.00
120.00
140.00
Time [ms]
XY Plot 5
Ansoft Corporation
Outer rotor3
800.00
Curve Info
Moving1.Torque
Setup2 : Transient
600.00
Torque
Production
Moving1.Torque [kNewtonMeter]
Y1 [Wb]
5.00
400.00
200.00
0.00
-200.00
-400.00
-600.00
-800.00
0.00
20.00
40.00
60.00
80.00
Time [ms]
100.00
120.00
140.00
(2) Outer Rotor with 288 Stator Slots
(2) Outer Rotor with 288 Stator Slots
XY Plot 1
Ansoft Corporation
Outer rotor
15.00
Curve Info
FluxLinkage(WindingA)
Setup2 : Transient
FluxLinkage(WindingB)
Setup2 : Transient
10.00
FluxLinkage(WindingC)
Setup2 : Transient
Winding
Flux
Linkage
0.00
-5.00
-10.00
-15.00
0.00
20.00
40.00
60.00
80.00
100.00
120.00
140.00
Time [ms]
XY Plot 5
Ansoft Corporation
Outer rotor
800.00
Curve Info
Moving1.Torque
Setup2 : Transient
600.00
400.00
Torque
Production
Moving1.Torque [kNewtonMeter]
Y1 [Wb]
5.00
200.00
0.00
-200.00
-400.00
-600.00
-800.00
0.00
20.00
40.00
60.00
80.00
Time [ms]
100.00
120.00
140.00
(3) Inner Rotor with 360 Stator Slots
(3) Inner Rotor with 360 Stator Slots
XY Plot 2
Ansoft Corporation
Innerrotor1
20.00
Curve Info
FluxLinkage(Winding1)
Setup1 : Transient
15.00
FluxLinkage(Winding2)
Setup1 : Transient
10.00
FluxLinkage(Winding3)
Setup1 : Transient
Winding
Flux
Linkage
0.00
-5.00
-10.00
-15.00
-20.00
0.00
20.00
40.00
60.00
Time [ms]
80.00
100.00
120.00
XY Plot 1
Ansoft LLC
Innerrotor1
800.00
Curve Info
Moving1.Torque
Setup1 : Transient
600.00
Torque
Production
Moving1.Torque [kNewtonMeter]
Y1 [Wb]
5.00
400.00
200.00
0.00
-200.00
-400.00
-600.00
-800.00
0.00
20.00
40.00
60.00
80.00
Time [ms]
100.00
120.00
140.00
(4) Inner Rotor with 288 Stator Slots
(4) Inner Rotor with 288 Stator Slots
XY Plot 3
Ansoft LLC
Innerrotor
15.00
Curve Info
FluxLinkage(WindingA)
Setup1 : Transient
FluxLinkage(WindingB)
Setup1 : Transient
10.00
FluxLinkage(WindingC)
Setup1 : Transient
Winding
Flux
Linkage
0.00
-5.00
-10.00
-15.00
0.00
20.00
40.00
60.00
80.00
100.00
120.00
140.00
Time [ms]
XY Plot 1
Ansoft LLC
Innerrotor
800.00
Curve Info
Moving1.Torque
Setup1 : Transient
600.00
Torque
Production
Moving1.Torque [kNewtonMeter]
Y1 [Wb]
5.00
400.00
200.00
0.00
-200.00
-400.00
-600.00
-800.00
0.00
20.00
40.00
60.00
80.00
Time [ms]
100.00
120.00
140.00