6-phase fault-tolerant permanent magnet traction drive for EVs

Transcription

European Conference on Nanoelectronics and Embedded Systems for Electric Mobility
“eMobility eMotion”
25-26th September 2013, Toulouse, France
6-phase Fault-Tolerant Permanent Magnet
Traction Drive for Electric Vehicles
Chris Gould, University of Sheffield
Vipulkumar Patel
Jiabin Wang
Dian Nugraha
Radovan Vuletic
Jonas Tousen
Jan Klenner
High Power Motor
Role of partners in supply chain
IGBT 650V
6~
IFAG
22 kW 22 kW
320 V 320 V
Gear ratio (8-10)
41 kW
320 V
USFD
VW
41 kW
Multi-phase inverter
with independent
control
Fault tolerant multiphase motor having
wide speed range
with high efficiency
Specifications and
Workbench tests
Key challenges for EV traction
A
A. Starting torque
at low speed
B
B. Acceleration
C. Efficiency
D. Speed range
E. Power density
F. Torque ripple
G. Reliability &
fault tolerance
D
H. Flexibility of
control
Drive train & design specifications
Motor
41 kW
Inverter 2
Inverter 1
32 kW
Battery
2800
Power train drive for
segment A vehicle
11000
Nominal DC link voltage
320 V
Maximum line-line voltage
650 V
Cooling medium
Water
Novel fault-tolerant 6-phase electric motor
Novel 6-phase, 18-slot, 8-pole winding configuration
 Improvement of safety and availability by designing the
machine topology as two independent balanced 3-phase
systems in single stator
 Fault tolerant as vehicle will continue to run with 50%
power/torque output even with loss of one 3-phase
system
 Lower torque ripple & cogging torque
 Lower eddy current losses in rotor PMs
 Lower copper losses due to shorter end-windings
Novel fault-tolerant 6-phase motor
Development of winding configuration
A+
F+
F+
B- A+
B+
B+
4
A-
B-
FF-
A+
6
1
7
B+
C-
C
8
C+ C+
A-
B-
B-
CC-
C-
3-phase, 9-slot, 8-/10-pole winding
F
A-
6
D+
D+
D+
EE-
5
F+
4
A
A+ A+
A+
3
2
14
14
B+
C-
7
A-
FF-
1
11
1
12
12 D
D
13
13
DDD- D-
C+
9
B-
10
10 B
A+
A 2
8
9
D+
D+
3
B
B+
B+
A-
5
B-
F+
F+
B+
FF-
15
C
C+
+
C
C+
+
C
16 17
16
E+
D-
E 1
18
18
E+ E+
AC
C+
+
EE-
CC-
EE-
C-
6-phase, 18-slot, 8-/10-pole winding
Normalized MMF space harmonics distribution
1
0.9
0.8
9-slot, 8-pole
18-slot, 8-pole
MMF (pu)
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
5
10
15
Order of harmonic
20
25
 The novel winding configuration eliminates many harmonics, which leads to lower
eddy current loss in PM and lower torque ripple in a machine.
Design Constraints for EV traction motor with PMs
Type of
constraints
Volumetric
Design parameter
Stator outer radius
mm
≤ 75.00
Stack length of the motor
mm
≤ 150.00
kg
≤ 1.2
mWb
≤ 74.7
mH
> 0.256
Inductance (to achieve high efficiency
in field weakening region)
mH
≤ 0.721
Copper winding temperature
˚C
≤ 180˚
Steel lamination temperature
˚C
≤ 225˚
PM temperature
˚C
≤ 150˚
Mass of PM material
Maximum flux linkage (derived from
maximum line-to-line voltage)
Electromagnetic Inductance (to achieve peak torque)
Thermal
Constraints
Design optimized against specifications, mechanical and thermal
constraints for maximum efficiency over NEDC
Cross-section of optimized design
MAGWID/2
LM
IPMHQ
Conceptual design
Optimized design
1.1 kg PM material
0.9 kg PM material
94.4% energy efficiency over NEDC
94.9% energy efficiency over NEDC
Performance of the optimized design – at rated & peak torque
150
140
130
Rated torque
Peak torque
120
110
Nm
75
140
%
2.5
4.2
rpm
2800
2800
A
74.0
172.5
A/mm2
9.7
22.7
140
Copper loss
W
809
4394
120
Iron loss
W
181
273
100
0.92
PM eddy current loss
W
8
56
80
0.9
Torque ripple
Speed
Peak current
Current density
Efficiency
%
95.7
89.7
100
90
80
70
60
50
0
60
120
180
240
Rotor angle (elect. deg)
300
360
0.96
Torque, Nm
Torque
Peak
Torque
Torque (Nm)
Rated
Torque
0.94
0.88
60
0.86
40
NEDC energy
efficiency
%
0.84
94.9
20
0
0.82
2000
4000
6000
Speed, rpm
8000
10000
12000
0.8
Prototype motor & inverter
Rotor assembly
Laminations
Stator frame
Stator assembly
Motor assembly
Inverter with instrumentation
Test bench for direct measurement of efficiency at USFD
 Comparison of prediction and test results at USFD
100
98
FEA Ph A
FEA Ph B
FEA Ph C
Test Ph A
Test Ph B
Test Ph C
60
Back EMF (V)
40
20
0
-20
97
96
95
Efficiency (%)
80
93
92
-40
-60
91
-80
90
-100
0
Measured
Predicted
94
60
120
180
240
Rotor Angle (deg, electrical)
Back EMF at 2800 rpm
300
360
89
0
10
20
30
40
50
Torque (Nm)
60
70
80
Efficiency at 2800 rpm
 The measured back EMF matches very well with the finite element analysis
predictions with a difference being just 2.7%.
 The efficiency at the base speed of 2800 rpm matches closely with the prediction.
Torque (Nm)
Torque (Nm)
 Measured efficiency map of inverter & motor with 320V at VW
Speed (rpm)
Speed (rpm)
Efficiency map of 6-phase inverter
Efficiency map of 6-phase motor
 Both the inverter and the motor exhibits high efficiency over the wide speed
range.
Torque (Nm)
 Measured efficiency map of power drive train at VW
Speed (rpm)
 The novel fault-tolerant motor-inverter drive system has a high efficiency over
wide speed range.
Conclusions
 Novel 6-phase motor is designed and developed to
enhance safety and availability of power train drive.
 The motor is inherently fault tolerant. Loss of one 3-phase
system does not result into complete loss of traction power.
 The new motor configuration exhibits high efficiency over a
wide speed range, which is one of the key requirement for
EV traction.
 Series of experimental measurements on a prototype
motor and inverter have validated the novel fault-tolerant
motor.

6-phase fault-tolerant permanent magnet traction drive for EVs

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