Performance/cost comparison of induction-motor &
permanent-magnet-motor in a hybrid electric car
Malcolm Burwell – International Copper Association
James Goss, Mircea Popescu - Motor Design Ltd
July 2013 - Tokyo
Is it time for change in the traction motor
supply industry?
Motor-types sold by
suppliers of vehicle
traction motors *
“[Our] survey of 123 manufacturers shows far too few
making asynchronous or switched reluctance
synchronous motors... this is an industry structured
for the past that is going to have a very nasty
surprise when the future comes.” *
* Source: IDTechEx research report “Electric Motors for Electric Vehicles 2013-2023: Forecasts, Technologies, Players”
www.IDTechEx.com/emotors
2
| Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013
The challenge for electric traction motors:
rare earth cost-levels and cost-volatility
3000
Permanent Magnet Motor Materials (“rare earths”)
Ne Oxide
Dy Oxide
2500
Dysprosium Oxide
2000
Neodymium Oxide
$ per kg
1500
Copper (for reference)
1000
$480/kg
$60/kg
$7/kg
500
0
2001 2002
2003 2004 2005 2006 2007 2008
2009 2010 2011 2012 2013
Source: metal-pages.com, Kidela Capital
3
| Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013
Background to this work
Today, the permanent magnet motor is the leading choice for traction drives
in hybrid vehicles
But permanent magnet motors have challenges:
•
•
•
High costs
Volatile costs
Uncertain long term availability of rare earth permanent magnets
This makes alternative magnet-free motor architectures of great interest
The induction motor is one such magnet-free architecture
4
| Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013
This presentation
The work presented here compares two equivalent 50kW tractions motors
for use in hybrid electric vehicles: a permanent magnet motor and an
equivalent induction motor
•
The main analysis has copper as the rotor cage material of an induction motor
•
Motoring and generating modes are modelled using standard drive cycles
•
Important outputs of the work, for each motor type, are:
•
5
•
Lifetime energy losses and costs
•
Relative component performance parameters, weights and costs
Top-level comments on aluminium cages are presented at the end
| Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013
Overview of the analysis covered in this
presentation
90
)
80
70
p
60
50
(
40
Total losses in the motor
Permanent
magnet motor
Copper rotor
induction
motor
City driving over 120,000 miles (UDDS)
p
30
20
10
0
0
500
1000
1500
1. Driving cycles
Induction Motor
5. Motor
Performance
1270 kWh
2240 kWh
Highway driving over 120,000 miles (HWFET)
610 kWh
1250 kWh
Aggressive driving over 120,000 miles (US06)
1430 kWh
2510 kWh
Combined average losses over 120,000 miles
1100 kWh
2000 kWh
Extra energy cost (grid price of $0.25/kWh)
0
$220
Extra energy cost (internal combustion engine cost of $0.294/kWh)
0
$260
6. Energy Losses
& Costs
Materials per motor
2. Vehicle Model
Permanent
Magnet Motor
Magnetics
3. Powertrain
Model
6
Heat Flows
4. Motor Models
| Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013
7. Inverter
Currents
9. Battery
Capacities
Permanent magnet
motor
Copper rotor induction
motor
Weight
Cost
Weight
Cost
Stator Copper
4.5 kg
$31
9.1 kg
$64
Steel
24 kg
$24
24 kg
$24
Permanent magnets
(2011/2013 prices)
1.3 kg
$200-540
0
0
Rotor cage
0
0
8.4 kg
$59
Increased inverter cost
-
0
-
$50
Total
29.8 kg
(100%)
$260-590
41.5 kg
(140%)
$200
Reduction of consumer
purchase price*
-
0
-
$150-980
8. Motor Weights
& Costs
10. Breakeven
Analysis
Main conclusions from this work
•
•
•
•
Comparing a 50kW copper-rotor induction motor to a 50kW permanent magnet motor:
•
No rare earth metals used
•
-25% torque density
•
+40% weight
•
+10-15% peak inverter current
However, the induction motor is a good alternative because:
•
Total motor+inverter unit costs are $60-$390 less (=$150-980 lower sticker price)
•
It uses only $260 in extra energy over 120,000 miles
•
Increased inverter costs are modest at ~$50/vehicle
Battery size:
•
Can optionally be increased to match increased motor losses
•
Unit cost savings are larger than increased battery costs up to 27kWh battery size
Using aluminum instead of copper in the rotor of a 50kW induction motor for an HEV:
•
7
Increases losses by 4%
| Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013
•
Lowers torque density by 5%
1. Vehicle drive cycles
Three standard drive cycles are used for the comparison of two traction
motors: a permanent magnet motor and a copper rotor induction motor.
The 120,000/10year vehicle life is assumed to be composed equally of these
three types of driving
90
Speed (miles per hour)
80
70
60
50
40
30
Distance
Average
speed
City
(UDDS)
7.5 miles
20 mph
Highway
(HWFET)
10.3 miles
48 mph
8.0 miles
48 mph
Aggressive
(US06)
20
10
0
0
500
1000
Time (seconds)
8
Driving
cycle
| Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013
1500
2. Vehicle Model
A standard vehicle model is used to convert drive cycle information into
powertrain torque/speed requirements.
Faero
Frolling
9
Ftraction
| Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013
3.1 Powertrain model
A standard two motor/generator hybrid powertrain architecture is used
•
Consists of two electrical motor/generators, MG1 and MG2 and an internal
combustion engine, all connected through a planetary gear set
•
Rotational speed of the internal combustion engine (ICE) is decoupled from
the vehicle speed to maximise efficiency
•
We analyze MG2 for performance/cost
•
We assume that MG2:
•
Has a rated power of 50kW
•
Couples to the drive wheels through
a fixed gear ratio
•
Provides 30% of motoring torque
•
Recovers up to 250Nm braking
torque
•
The ICE and brakes supply the rest
10 | Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013
3.2 Motor torques/speeds produced during driving
cycles
By applying the vehicle and powertrain models we convert the driving cycle
data into motor torque/speed data points. One data point is produced for
each one second of driving cycle
Highway cycle MG2 loads
(HWFET)
Aggressive cycle MG2 loads
(US06)
150
150
100
100
100
50
50
50
0
-50
-100
MG2 torque (Nm)
150
MG2 torque (Nm)
MG2 torque (Nm)
City cycle MG2 loads
(UDDS)
0
-50
-100
0
-50
-100
-150
-150
-150
-200
-200
-200
-250
0
1000
2000
3000
4000
MG2 Speed (rpm)
5000
-250
0
1000
2000
3000
4000
MG2 Speed (rpm)
11 | Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013
5000
-250
0
1000
2000
3000
4000
MG2 Speed (rpm)
5000
4.1 Magnetic models of permanent magnet
motor and induction motor
The two motor types were modeled for similar torque/speed performance:
same stator outside diameters, same cooling requirements but different
stack lengths
Stator OD = 270mm
Rotor OD = 180mm
Stator OD = 270mm
Rotor OD = 160mm
Stack Length = 105mm
Stack Length = 84mm
Permanent
Magnet Motor
Copper Rotor
Induction Motor
8
Poles
8
48
Stator Slots
48
-
Rotor Bars
62
12 | Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013
4.2 Reference permanent magnet motor
model
The modelled permanent magnet motor is a well-documented actual motor
used in a production hybrid vehicle.
13 | Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013
4.3 Validation of the motor performance
model
The model of the permanent magnet motor was validated against test data
from the actual motor
g
88
91
86
0
4000
5000
6000
82
80
Model data (including mechanical losses)
90
94
96
95
88
880
9628
9
0710
949
8880
81
238
8
48
5
88
0
960
2
89
70
96 96
1000
2000
3000
4000
Speed (RPM)
88
5000
93
890
7
86
85
10
32
88
88
84
6000
14 | Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013
80
Model Data (excluding mechanical losses)
Our analysis continues using
motor performance which
excludes mechanical losses
Test data from actual motor (including mechanical losses)
84
94
82
94
94
89
92
91
94
91 88 87
93
93 9590
93 9590
81
82
92
80
83
84
85
92
86
880 87
83
60
70
81
80
82
84
0
70
80
60
81
8290
86
83
89 9189
85
84
86
85
88 87
70
60
0
86
99
07
8
36
95
96
Torque (Nm)
92
93
60
70
8132
8880
84856
87
50
0
90
9387
95
89
93
93
60
70
882
81
80
834
90 85867 88
9932
91 89
89
88 87
90
92
91
Torque (Nm)
80
81
83 82
84
85
88 87 86
89
90
80
83 82
81
84
85
86
84
88 88
97 88883465 88
012
87
86
85
84
8182
83
80
94
60
3000
Speed (RPM)
150
92
589
28348
88801
0897910
962
90
88
8182
80
200
100
089
94
880
8883465
91880129
96
7
0
92
91
87 89
86
p
4
608
8589
Model and
actual data
correspond
well
92
91
8
90
87 9
88
838485 86
82
81
80
0
1000
2000
87
50
88
8 82
9
100
250
90
89
0290
801
8883465 91
150
87
200
92
88
250
y
8
60
708
880
1
23
8
0
300
94
Efficiency (%)
oss
89
ota
83
81
82
0
84
85 80
4.4 Thermal Performance Comparison
Steady-state thermal analysis was used to equalize
cooling system requirements for both motors at a
118 Nm/900 rpm operating point
Permanent Magnet
Motor
Copper Rotor
Induction Motor
92%
Efficiency
88%
780 W
Stator Copper Loss
940 W
0W
Rotor Loss
230 W
0W
Stray Load Loss
140 W
100 W
Iron Loss
180 W
880 W
Total Loss
1490 W
105°C
Coolant Temperature
105°C
2.4 gallons/min
Coolant Flow Rate
2.4 gallons/min
156°C
Maximum Winding Temp
156°C
15 | Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013
5.1 Torque/speed/efficiency maps of the
permanent magnet motor and induction motor
The two motors have similar torque/speed performance, with the induction
motor having ~5% lower efficiencies
Permanent magnet motor
p
96
962
8099710
88808128
348
59806
880
60
70
80
81
82
83
84
85
86
87
89 88
90
92
91
90
89
-300
89
90
88
80
8046
57760
88
9123
89
5000
6000
6700
80
82
81
83
84
85
86
87
91
92
08
880191
283
91
89
-250
92
8589
6087
8576
884
90
91
16 | Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013
-150
88
87
86
85
84
83
82
81
80
4000
92
91
88
4
6070 888081823
84
70
80
81
82
83
84
85
8687
89 88
90
80
81
82
83
84
85
8687 88
89
90
91
-100
-200
89
91
90
Speed (rpm)
8887
86
85
8834
82
81
80
93
92
0
-50
88
87
86
85
84
81
82
83
80
760
3000
2000
1000
0
0
89
90
87
86
85
84
83
82
81
80
70
60
-250
88
87 89
386
888184
285
80
70
60
95
94
91 89
93
92
8
87 8
86
8845
82
83
80
81
70
60
880
93 87
94
-200
-300
95
98936
807
85
834
94 0 888012
9791
96280
70
289
960
86
90
91
90
90
670
96
90
-150
96
0
88
88
91
88898012345
67768
008
92
8887
86
85
84
83
82
81
80
94
95
93
50
0
Generating torque (Nm)
58883210
884
88 890
786
93
-50
-100
80
Speed (rpm)
60
70
60
86
85
70
81
84
80
83
8290
86
85
88 87
89
88 87
0
83
60
70
84
82
80
81
880 87
86
85
92
84
83
81
91
82
93 9590 9189 94
92
94
890189
93
93 9590
92
94
96 96
89
Generating torque (Nm)
0
96 96
93
94
786
88 890
8584
94
91
93
93 9590
93 9590 9189 94
81
82
92
80918992
83
8883210
8584
92
86
880 87
83
84
82
81
70
60
80
0
88 87
86
89
86
85
84
82
8390
85
60
81
70
80
88 87
7060
0
1000
2000
3000
4000
5000
6000
100
89
82
89
0
84
0 88888
012
838488576
96280790
94
760
95
96
50
880
150
60
70
80
81
82
83
84
85
86
87 8
90 89 8
91
92
94
95
96
86
60
70
91 89
88
90
60
70
83
81
880
82
848587
6
9932
962890
791
94 08880
8182384
985936807
90
92
100
88
880
95
200
94
92
90
150
90
9387
Efficiency (%)
94
Motoring torque (Nm)
89
91
88
92
93
90
58960
2348
888018
0897910
962
200
250
608
8888018243956778
91
60
70
80
81
82
83
84
85
86
87
92
90
94
880
250
96
300
6087
8589
Motoring torque (Nm)
y
700
96
23848576
818
0 8880
89 88
82
80
Efficiency (%)
g
607088808123
4
0
300
Copper rotor induction motor
5.2 Torque/speed loads during drive cycles:
permanent magnet motor
Torque/speed points from the vehicle/powertrain model of the driving
cycles are applied to the performance map of the permanent magnet motor
to determine total motor losses during driving:
89
91
88
90
94
95
96
Speed (rpm)
70
60
0
89
88 87
88 87
86
85
86
85
84
8390
82
80
81
70
60
880 87
83
84
82
81
70
80
60
86
85
92
84
83
92
81
91
82
93 9590 9189 94
890189
93
93 9590
94
92
94
96 96
58883210
884
88 890
786
93
94
-50
-300
95
0
4
6070 888081823
807
8936
895
834
94 0 888012
89791
9620
880
962
8097910
88808128
348
58960
93 87
94
-200
-250
96
880
-150
95
8589
6087
-100
84
0
88
70
289
960
80
Efficiency (%)
92
93
60
70
80
81
82
83
84
85
86
87
91 89
88
60
70
83
81
880
82
848587
6
9932
96280790
94
89
Generating torque (Nm)
962
8097910
88808128
348
58960
880
90
94
95
Motoring torque (Nm)
89
91
88
92
93
60
70
80
81
82
83
84
85
86
87
90
8589
6087
Generating torque (Nm)
962
8097910
88808128
348
58960
880
0
89
8589
6087
86
880
82
91
Generating torque (Nm)
95
88
89
17 | Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013
50
93
92
91
4
6070 888081823
962890
791
94 08880
8182384
985936807
96
90
88
89
0
100
88
880
95
87
86
85
84
83
82
81
80
70
60
93
92
87
86
85
84
83
82
81
80
70
60
91
-300
880
93 87
94
-200
-250
95
807
8936
895
834
94 0888012
89791
9620
70
289
960
150
90
9387
95
94
91 89
93
92
8
87 8
86
8845
82
83
81
80
70
60
-150
96
0
88
92
94
90
-100
95
200
96
94
-50
94
89
58883210
884
88 890
786
93
250
96 96
93
94
786
88 890
8584
94
91
93
93 9590
93 9590 9189 94
81
82
92
80918992
83
8883210
8584
92
86
880 87
83
84
82
81
80
0
70
60
86
85
88 87
84
89
86
85
8390
82
81
80
70
60
88 87
7060
0
6000
4000
5000
2000
3000
1000
0
Speed (rpm)
70
60
0
88 87
89
88 87
86
86
85
84
81
80
60
8290
83
85
70
880 87
83
84
81
70
60
82
80
86
85
92
84
83
92
81
91
82
93 9590 9189 94
890189
93
93 9590
94
92
94
96 96
90
88
4
6070 888081823
0
95
94
91 89
93
92
8
87 8
86
8845
82
83
80
81
70
60
93
92
0
807
8936
895
834
94 0 888012
89791
9620
880
93 87
90
87
86
85
84
83
82
81
80
70
60
-300
95
94
-200
-250
96
96280790
94
96
96
95
94
91 89
93
92
8
87 8
86
8845
82
83
80
81
70
60
-150
90
-100
70
289
960
95
880
96 96
93
94
786
88 890
8584
94
91
93
93 9590
93 9590 9189 94
81
82
92
80918992
83
8883210
8584
92
86
880 87
83
60
0
70
82
81
80
84
60
70
81
80
84
83
8290
85
86
85
86
88 87
89
88 87
7060
0
1000
2000
3000
4000
5000
6000
90
94
0
88
91 89
50
0
Speed (rpm)
95
96
89
0
-50
962890
791
94 08880
8182384
985936807
89
96 96
93
94
786
88 890
8584
94
91
93
93 9590
93 9590 9189 94
81
82
92
80918992
83
8883210
8584
92
86
880 87
83
60
70
80
81
82
84
0
70
60
80
81
8290
85
84
83
85
88 87
86
86
89
88 87
7060
0
1000
2000
3000
4000
5000
6000
g
y
p
0
70
6
0
0
70
81
60
83
82
86
85
84
80
86
85
88
87
89
88
87
90
88 87
83
60
70
81
82
80
84
0
86
85
92
84
83
92
81
58883210
82
91
93 9590 9189 94
890189
93
93 9590
94
884
92 88 890
786
94
93
96 96
880
95
88
100
60
70
83
80
881
82
848587
6
9932
96280790
94
9387
90
90
94
95
95
96
50
880
Motoring torque (Nm)
89
91
88
92
93
60
70
80
81
82
83
84
85
86
87
91 89
88
60
70
83
80
881
82
848587
6
9932
90
96
150
89
Motoring torque (Nm)
100
962890
791
94 08880
8182384
985936807
89
Permanent magnet motor
880
95
94
96
58960
2348
888018
0897910
962
150
200
p
880
9387
58960
2348
888018
0897910
962
58960
2348
888018
0897910
962
94
880
880
200
250
y
607088808123
4
0
300
6087
8589
6087
8589
250
g
607088808123
4
0
300
6087
8589
607088808123
4
0
300
Highway driving cycle loads Aggressive driving cycle loads
(HWFET)
(US06)
96
City driving cycle loads
(UDDS)
5.3 Torque/speed loads during drive cycles:
copper rotor induction motor
Highway driving cycle loads Aggressive driving cycle loads
(HWFET)
(US06)
60
70
80
81
82
83
84
85
86
87
89 88
90
92
91
60
70
80
81
82
83
84
85
86
87 8
8
90 9 8
91
92
91
88898013254
67786
080
86
3000
84
-250
92
08
880191
823
576
8884
90
670
89
91
89
90
0036
8
57760
888
9124
89
88
5000
70
80
81
82
83
84
85
8687
89 88
90
92
90
-300
4000
80
81
82
83
84
85
8687 88
89
90
91
0 88888
018
238488576
-200
88
87
86
85
84
83
82
81
80
Speed (rpm)
-100
-150
91
90
6000
6700
80
82
81
83
84
85
86
87
91
-50
89
88
87
86
85
84
81
82
83
80
760
2000
760
88
91
92
08
880191
823
Motoring torque (Nm)
90
92
91
90
670
1000
0
Generating torque (Nm)
60
70
80
81
82
83
84
85
86
87
89 88
89
0
91
90
89
0 88888
018
238488576
88
60
70
80
81
82
83
84
85
86
87 8
90 89 8
91
92
60
70
88
87 89
386
888184
285
80
92
18 | Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013
89 88
88
90
8887
86
85
8834
82
81
80
90
90
-300
90
23848576
818
0 8880
90
92
50
70
60
91
89
-250
89
600
97
92
93
90
576
8884
92
-200
6700
80
82
81
83
84
85
86
87
100
0
6000
94
91
-150
760
92
-100
80
1245
80
67760
88
93
89
150
89
08
880191
823
92
91
90
670
-50
88
87
86
85
84
83
82
81
80
5000
70
80
81
82
83
84
85
8687
89 88
90
80
81
82
83
84
85
8687 88
89
90
91
8887
86
85
8834
82
81
80
89
Speed (rpm)
0
90
89
0 88888
018
238488576
90
23848576
818
0 8880
0
89
88
87
86
85
84
81
83
80
82
760
3000
4000
70
60
92
8887
86
85
8834
82
81
80
760
89
600
97
89 88
91
90
88
87 89
86
85
888184
23
80
1000
2000
89
91
90
70
60
-300
576
8884
91
6700
80
82
81
83
84
85
86
87
91
60
70
92
6000
90
91
90
200
8887
86
85
84
83
82
81
80
80
81
82
83
84
85
8687 88
89
90
91
89
-150
5000
70
80
81
82
83
84
85
8687
89 88
90
-100
-250
4000
91
88898012345
67768
008
92
50
8887
86
85
84
83
82
81
80
Generating torque (Nm)
3000
Speed (rpm)
0
Motoring torque (Nm)
90
92
91
2000
88
87
86
85
84
83
82
81
80
Generating torque (Nm)
60
70
80
81
82
83
84
85
86
87
89 88
Motoring torque (Nm)
60
70
80
81
82
83
84
85
86
87 8
8
90 9 8
91
92
1000
89
80
8036
57760
88
9124
89
93
250
92
0
88
87
86
85
84
81
82
83
80
760
91
90
96
90
88
87 89
386
888184
285
80
91
90
100
p
608
8888018243956778
91
90
92
50
150
y
90
93
200
92
92
100
91
88898013254
67768
008
250
90
90
150
-200
g
300
608
8888081329456778
91
608
8888018243956778
91
200
-50
p
90
90
250
0
y
600
97
23848576
818
0 8880
89 88
82
80
Efficiency (%)
g
300
300
60
70
City driving cycle loads
(UDDS)
8887
86
85
84
83
82
81
80
Copper rotor induction motor
Torque/speed points from the vehicle/powertrain model of the driving
cycles are applied to the performance map of the copper rotor induction
motor to determine total motor losses during driving:
6.1 Motor losses during driving cycles
From the motor models, cumulative losses during each driving cycle can be
calculated:
Cumulative losses over driving cycle (Wh)
Time (seconds)
Aggressive driving cycle losses
(US06)
Cumulative losses over driving cycle (Wh)
Highway driving cycle losses
(HWFET)
Cumulative losses over driving cycle (Wh)
City driving cycle losses
(UDDS)
Time (seconds)
Permanent magnet motor
19 | Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013
Time (seconds)
Copper rotor induction motor
6.2 Combined losses over life of the motor
The total difference in electrical running costs between the permanent
magnet motor and the copper rotor induction motor are $220-$260. Over
a typical lifetime of 120,000miles and 10 years, this is an insignificant
cost.
Total losses in the motor
Copper rotor
Permanent
induction
magnet motor
motor
City driving over 120,000 miles (UDDS)
1270 kWh
2240 kWh
Highway driving over 120,000 miles (HWFET)
610 kWh
1250 kWh
Aggressive driving over 120,000 miles (US06)
1430 kWh
2510 kWh
Combined average losses over 120,000 miles
1100 kWh
2000 kWh
Extra energy cost (grid price of $0.25/kWh)
0
$220
Extra energy cost (internal combustion engine cost of $0.294/kWh)
0
$260
20 | Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013
7. Cost of increased inverter for copper
motor induction motor
The copper rotor induction motor/generator requires 10-15% more current
to achieve maximum torque. This requires that the power electronics cost
~$50 more than for a permanent magnet motor.
Copper rotor induction motor
Speed (rpm)
21 | Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013
Peak phase current (A)
Motoring torque (Nm)
Peak phase current (A)
Motoring torque (Nm)
Permanent magnet motor
Speed (rpm)
8. Component cost comparison
The copper rotor induction motor saves between $60 (at 2013 magnet
prices) and $390 (at 2011 magnet prices) costs per vehicle. This translates
into $150-980 purchase price savings for the consumer
Materials per motor
Permanent magnet
motor
Copper rotor induction
motor
Weight
Cost
Weight
Cost
Stator Copper
4.5 kg
$31
9.1 kg
$64
Steel
24 kg
$24
24 kg
$24
Permanent magnets
(2011/2013 prices)
1.3 kg
$200-540
0
0
Rotor cage
0
0
8.4 kg
$59
Increased inverter cost
-
0
-
$50
Total
29.8 kg
(100%)
$260-590
41.5 kg
(140%)
$200
-
$150-980
Reduction in consumer
0
purchase price*
* Assumes materials-cost/consumer-price ratio = 40%
22 | Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013
9. Cost of increased battery capacity to cover
increased motor losses
Using a copper rotor induction motor can require the vehicle designer
to increase the battery size by ~7%. This would allow a customer to
perceive no difference in overall vehicle performance.
Key assumptions used in costing the required increase in battery
capacity:
•
•
•
•
•
Motor must at some time provide all motoring and braking torque in the
highway driving cycle (like a plug-in hybrid electric vehicle)
Induction motor uses 7% more motoring energy than a permanent
magnet motor
Induction motor recovers 6% less braking energy than the permanent
magnet motor
Total braking energy is 20% of the motoring energy over the driving cycle
75% of battery energy is used for motoring, 25% for auxiliary systems
(cabin conditioning, lights, radio, electronics)
23 | Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013
10. Break-even for using copper motor
induction motor
Induction motor cost savings ($)
If the designer chooses to increase battery size for a 50kW system, a
copper rotor induction motor saves total vehicle costs when the battery
size for a permanent magnet motor system is less than 27kWh
600
500
2011 break-even
Additional battery cost*
400
$390 unit cost savings
(2011 Rare Earth prices)
300
2013 break-even
200
$60 unit cost savings
(2013 Rare Earth prices)
100
0
0
10
20
30
Permanent magnet motor battery capacity (kWh)
24 | Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013
40
* Assumes 2020 battery
pricing of $200/kWh and 7%
battery capacity increase for
copper rotor induction motor
Possible use of aluminum in the rotor of an
induction motor
Aluminum has only 56% of the conductivity of copper, which leads to an
inferior performance when used in the rotor of an induction motor. In a
first-pass analysis of a 50kW aluminum rotor induction motor, losses were
4% higher and power/torque densities 5% lower than the equivalent copper
rotor motor.
Aluminum rotor induction motor
96
86
0
88
87 89
86
85
8880818234
0
1000
2000
88
87
86
85
84
81
82
83
80
760
3000
89
91
90
4000
88
91
90
88
0036
57760
88
9124
89
88
87
86
85
84
83
82
81
80
5000
6000
60
70
80
81
882
88345
86
87
88
89
90
91
92
88
76
8988800814253670
8
86
90
91
92
50
100
84
90
92
90
150
60
70
81
82
83
88480
85867
8
898
90
90
91
60
70
80
81
82
83
8
884
5
867 8
90 89 8
91
92
91
88898013254
67786
080
200
92
93
94
90 91
92
100
88
90
150
Motoring torque (Nm)
90
91
92
92
250
4586078
6
788808123
88
89
90
94
608
8888018243956778
91
200
96
300
Efficiency (%)
60
70
80
81
82
83
8845
86
87
89 88
250
90
Motoring torque (Nm)
300
82
80
Speed (rpm)
25 | Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013
50
0
90
8889
87
86
85
84
83
82
80
81
2000
1000
92
91
90
8889
87
86
85
84
83
82 80
81
4000
3000
Speed (rpm)
84
688081286
7
3
4
5
898870
89
88
87
86
85
84
83
82
80
81
6000
5000
82
80
Efficiency (%)
Copper rotor induction motor
Main conclusions from this work
•
•
•
•
Comparing a 50kW copper-rotor induction motor to a 50kW permanent magnet motor:
•
No rare earth metals used
•
-25% torque density
•
+40% weight
•
+10-15% peak inverter current
However, the induction motor is a good alternative because:
•
Total motor+inverter unit costs are $60-$390 less (=$150-980 lower sticker price)
•
It uses only $260 in extra energy over 120,000 miles
•
Increased inverter costs are modest at ~$50/vehicle
Battery size:
•
Can optionally be increased to match increased motor losses
•
Unit cost savings are larger than increased battery costs up to 27kWh battery size
Using aluminum instead of copper in the rotor of a 50kW induction motor for an HEV:
•
Increases losses by 4%
26 | Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013
•
Lowers torque density by 5%
Thank you
For more information please contact
malcolm.burwell@copperalliance.org
Phone: +1 781 526 5027
james.goss@motor-design.com
mircea.popescu@motor-design.com
Phone: +44 1691 623305
27 | Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013