EV traction motor comparison - Techno Frontier 2013 - M Burwell - International Copper Accociation
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A technical and cost comparison between induction motors and permanent magnet motors for traction in hybrid electric vehicles

A technical and cost comparison between induction motors and permanent magnet motors for traction in hybrid electric vehicles

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EV traction motor comparison - Techno Frontier 2013 - M Burwell - International Copper Accociation Presentation Transcript

  • 1. 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
  • 2. 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
  • 3. 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
  • 4. 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
  • 5. 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
  • 6. Overview of the analysis covered in this presentation 90 ) 80 70 p 60 50 Total losses in the motor ( Permanent magnet motor Copper rotor induction motor City driving over 120,000 miles (UDDS) 40 p 30 20 0 500 1000 Induction Motor 2510 kWh 2000 kWh 0 $220 Extra energy cost (internal combustion engine cost of $0.294/kWh) 5. Motor Performance 1250 kWh 1100 kWh Extra energy cost (grid price of $0.25/kWh) 1. Driving cycles 2240 kWh 1430 kWh Combined average losses over 120,000 miles 1500 610 kWh Aggressive driving over 120,000 miles (US06) 0 1270 kWh Highway driving over 120,000 miles (HWFET) 10 0 $260 6. Energy Losses & Costs Materials per motor Permanent magnet motor Copper rotor induction motor Weight 2. Vehicle Model Magnetics 3. Powertrain Model 6 Heat Flows 4. Motor Models | Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013 9.1 kg $64 24 kg $24 24 kg $24 1.3 kg $200-540 0 0 Rotor cage 9. Battery Capacities Cost $31 Permanent magnets (2011/2013 prices) 7. Inverter Currents Weight 4.5 kg Steel Permanent Magnet Motor Cost Stator Copper 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
  • 7. Main conclusions from this work • Comparing a 50kW copper-rotor induction motor to a 50kW permanent magnet motor: • • -25% torque density • • No rare earth metals used +40% weight • +10-15% peak inverter current However, the induction motor is a good alternative because: • • It uses only $260 in extra energy over 120,000 miles • • Total motor+inverter unit costs are $60-$390 less (=$150-980 lower sticker price) 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%
  • 8. 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 Driving cycle 50 40 30 7.5 miles 20 mph 10.3 miles 48 mph 8.0 miles 48 mph Aggressive (US06) 20 10 0 0 500 1000 Time (seconds) 8 Average speed Highway (HWFET) 60 Distance City (UDDS) 70 | Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013 1500
  • 9. 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
  • 10. 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
  • 11. 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 City cycle MG2 loads (UDDS) Highway cycle MG2 loads (HWFET) Aggressive cycle MG2 loads (US06) 100 100 50 50 50 0 -50 -100 MG2 torque (Nm) 150 MG2 torque (Nm) 150 100 MG2 torque (Nm) 150 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
  • 12. 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
  • 13. 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
  • 14. 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 88 0 92 691 87 0 9490803 81 4 888 8 2 8 5 88 0 92 70 60 89 96 96 1000 2000 3000 4000 Speed (RPM) 88 5000 93 890 5 30 7 6 82 88 84 1 8 88 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 95 9493 92 94 91 88 87 930 9089 91 88 87 88 9590 840 89 9394 81 82 92 92 86 83 91 6 89 83 60 70 81 80 82 84 70 80 60 81 82 86 90 83 85 84 86 0 87 85 8 70 0 85 0 86 996 7 8 30 95 96 Torque (Nm) 92 93 60 70 80 81 2 83 888 456 87 50 0 90 9387 95 89 93 93 60 70 885 81 80 82 3 4 90 8867 88 92 93 91 89 89 88 87 90 92 91 Torque (Nm) 80 83 81 84 82 85 88 87 86 89 90 83 80 84 81 85 82 86 84 88 88 97 8884 8 83 80 6 1 5 2 87 85 84 86 81 83 8082 94 6 0 3000 Speed (RPM) 150 92 9 858 34 08 882 881 10 89 6097 92 90 88 81 8082 200 100 089 94 0 88 884 836 59 8 1819 0 2 96 7 0 92 91 87 89 86 p 4 0 8 96 858 Model and actual data correspond well 92 91 8 90 87 9 88 84 81 8082 0 83 85 86 1000 2000 87 50 88 8 82 9 100 250 90 89 2 00 1 809 86 85 84 83 91 150 87 200 92 88 250 y 60 80 7088 81 83 2 0 300 94 Efficiency (%) oss 89 ota 83 5 80 0 84 81 8 82
  • 15. 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
  • 16. 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 92 687 91 090 882 808 83 14 859 80 6 88 0 60 70 80 81 82 83 84 85 86 87 89 88 90 92 91 90 89 -300 89 90 88 805 86 4 3 26 8807 0 917 89 5000 6000 7 6 80 0 820 81 83 84 85 86 87 91 92 08 80 91 82 13 8 91 89 -250 92 858 96 8 07 6 87 45 88 90 91 16 | Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013 -150 88 87 86 85 83 82 81 8084 4000 92 91 88 4 83 60 881 70 88 02 84 8070 81 82 83 84 85 86 87 89 88 90 80 81 82 83 84 88 85 86 87 89 90 91 -100 -200 89 91 90 Speed (rpm) 8887 86 4 885 83 82 81 80 93 92 0 -50 88 87 85 8186 82 83 8084 70 6 3000 2000 1000 0 0 89 90 87 86 85 84 83 82 81 80 70 60 -250 88 89 87 8286 8885 13 8084 70 60 95 94 91 89 93 92 8 87 8 886 84 825 83 81 80 70 60 0 88 93 87 94 -200 -300 95 30 9967 8 38 8 5 828 81 4 94 0 80 91 89 27 960 89 2 70 960 86 90 91 90 90 60 7 96 90 -150 96 0 88 88 91 881 884 92 06 37 56 7 80 8 0 92 8887 86 85 83 82 81 8084 94 95 93 50 0 Generating torque (Nm) 82 8 88 890 841 7 6580 88 3 93 -50 -100 80 Speed (rpm) 60 86 0 85 70 84 81 80 83 82 85 88 87 90 9089 91 88 87 880 878583 0700 83 70 60 84 82 81 80 89 86 86 82 6 92 81 91 92 9493 95 9394 9 92 9493 9590 848 189 96 96 89 Generating torque (Nm) 0 96 96 93 7 6 30 88 84 2 94 95 9394 91 92 88 890 5 881 9493 95 91 81 89 92 8 8 92 86 83 89 8693 90 840 6 83 84 82 81 70 60 80 88 87 90 9089 91 88 87 880 87 8582 70 0 86 0 85 84 82 83 85 81 60 70 80 0 1000 2000 3000 4000 5000 6000 100 89 82 89 0 84 0 88 8828 88 08 87 1356 4 960 0 27 89 94 60 7 95 96 50 88 0 150 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 70 835 80 81 84 82 8 87 86 92 93 968 209 97 1 94 0881 808 828 38 456 9987 30 90 92 100 88 88 0 95 200 94 92 90 150 90 9387 Efficiency (%) 94 Motoring torque (Nm) 89 91 88 92 93 90 80 596 38 84 81 802 08 91 89 607 92 200 250 4 0 3 16 60 8 8 8057 8827 8 89 91 60 70 80 81 82 83 84 85 86 87 92 90 94 0 88 250 96 300 07 8 86 859 Motoring torque (Nm) y 60 7 90 8 8 2 14 6 08 7 8835 0 88 89 88 82 80 Efficiency (%) g 60 882 70803 1 84 0 300 Copper rotor induction motor
  • 17. 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) 88 87 90 9089 91 88 87 880 878583 0700 86 0 85 85 84 83 82 81 80 70 60 83 84 82 81 70 80 60 89 8693 90 848 6 86 82 92 92 81 92 91 9493 95 94 95 9394 9189 96 96 8 82 88 890 841 88 3 7 6580 93 94 -50 -300 95 0 024 83 70 88 60 881 30 9967 8 38 8 5 828 81 4 94 0 80 91 89 27 960 0 88 92 687 91 090 882 808 83 14 859 86 0 93 87 94 -200 -250 96 88 0 -150 95 858 96 8 07 -100 84 0 88 2 70 89 960 80 Efficiency (%) 92 93 60 70 80 81 82 83 84 85 86 87 91 89 88 60 70 835 80 81 84 82 8 87 86 92 93 960 0 27 89 94 89 Generating torque (Nm) 92 687 91 090 882 808 83 14 859 86 0 88 0 90 94 95 Motoring torque (Nm) 89 91 88 92 93 60 70 80 81 82 83 84 85 86 87 90 858 96 8 07 Generating torque (Nm) 92 687 91 090 882 808 83 14 859 86 0 88 0 0 89 858 96 8 07 86 88 0 82 91 Generating torque (Nm) 95 88 89 17 | Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013 50 93 92 91 024 83 60 881 70 88 968 209 97 1 94 0881 808 828 38 456 9987 30 96 90 88 89 0 100 88 88 0 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 0 88 93 87 94 -200 -250 95 30 9967 88 8 5 81 4 038 94 0882 89 91 27 960 2 70 89 960 150 90 9387 95 94 91 89 93 92 8 87 8 886 84 825 83 81 80 70 60 -150 96 0 88 92 94 90 -100 95 200 96 94 -50 94 89 8 82 88 890 841 88 3 7 6580 93 250 96 96 93 7 6 30 88 84 2 94 95 9394 91 92 88 890 5 881 9493 95 91 81 89 92 8 8 92 89 8693 90 840 6 83 84 82 81 80 70 60 86 0 85 88 87 90 9089 91 88 87 88 87 8582 70 0 84 85 0 86 83 83 82 81 80 70 60 0 6000 4000 5000 2000 3000 1000 0 Speed (rpm) 88 87 90 9089 91 88 87 880 878583 0700 86 0 85 84 81 80 60 83 82 85 70 83 84 81 70 60 82 80 89 8693 90 848 6 86 82 92 92 81 92 91 9493 95 94 95 9394 9189 96 96 90 88 024 83 60 881 70 88 0 95 94 91 89 93 92 8 87 8 886 84 825 83 80 81 70 60 93 92 0 30 9967 8 38 8 5 828 81 4 94 0 80 89 91 27 960 0 88 93 87 90 87 86 85 84 83 82 81 80 70 60 -300 95 94 -200 -250 96 960 0 27 89 94 96 96 95 94 91 89 93 92 8 87 8 886 84 825 83 80 81 70 60 -150 90 -100 2 70 89 960 95 88 0 96 96 93 7 6 30 88 84 2 94 95 9394 91 92 88 890 5 881 9493 95 91 81 89 92 8 8 92 86 83 89 8693 90 840 6 83 60 70 82 81 80 84 60 70 81 80 84 83 82 85 86 0 85 88 87 90 9089 91 88 87 880 87 8582 70 0 0 1000 2000 3000 4000 5000 6000 90 94 0 88 91 89 50 0 Speed (rpm) 95 96 89 0 -50 968 209 97 1 94 0881 808 828 38 456 9987 30 89 96 96 93 7 6 30 88 84 2 94 95 9394 91 92 88 890 5 881 9493 95 91 81 89 92 8 8 92 86 83 89 8693 90 840 6 83 70 60 81 80 82 84 70 80 60 81 82 85 84 83 85 88 87 90 9089 91 88 87 880 87 8582 70 0 86 0 0 1000 2000 3000 4000 5000 6000 g y p 0 70 81 60 83 82 86 0 85 84 80 85 88 87 90 9089 91 88 87 880 878583 0700 83 70 60 82 81 80 84 89 8693 90 848 6 86 82 8 82 92 92 81 92 88 890 841 91 9493 95 94 95 9394 9189 88 3 7 6580 93 96 96 88 0 95 88 100 60 70 835 81 80 84 82 8 87 86 92 93 960 0 27 89 94 9387 90 90 94 95 95 96 50 88 0 Motoring torque (Nm) 89 91 88 92 93 60 70 80 81 82 83 84 85 86 87 91 89 88 60 70 835 81 80 84 82 8 87 86 92 93 90 96 150 89 Motoring torque (Nm) 100 968 209 97 1 94 0881 808 828 38 456 9987 30 89 Permanent magnet motor 88 0 95 94 96 0 86 859 34 08 81 882 08 91 89 607 92 150 200 p 0 88 9387 80 596 38 84 81 802 08 91 89 607 92 0 86 859 34 08 81 882 08 91 89 607 92 94 0 88 0 88 200 250 y 70803 60 882 1 84 0 300 07 8 86 859 07 8 86 859 250 g 60 882 70803 1 84 0 300 07 8 86 859 60 882 70803 1 84 0 300 Highway driving cycle loads Aggressive driving cycle loads (HWFET) (US06) 96 City driving cycle loads (UDDS)
  • 18. 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 89 88 90 91 92 91 881 885 93 06 27 48 7 60 0 8 86 3000 84 -250 92 08 80 91 88 13 2 6 85 47 88 90 7 60 89 91 89 90 817 06 06 4 3 8885 0 927 89 88 5000 8070 81 82 83 84 85 86 87 89 88 90 92 90 -300 4000 80 81 82 83 84 88 85 86 87 89 90 91 0 88 8888 88 02 87 1356 4 -200 88 87 86 85 83 82 81 8084 Speed (rpm) -100 -150 91 90 6000 7 6 80 0 820 81 83 84 85 86 87 91 -50 88 89 87 85 8186 82 83 8084 70 6 2000 70 6 88 91 92 08 80 91 88 13 2 Motoring torque (Nm) 90 92 91 90 60 7 1000 0 Generating torque (Nm) 60 70 80 81 82 83 84 85 86 87 89 88 89 0 91 90 89 0 88 8888 88 1356 02 87 4 88 60 70 80 81 82 83 84 85 86 87 8 90 89 8 91 92 60 70 88 89 87 8286 8885 13 8084 92 18 | Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013 89 88 88 90 8887 86 4 885 83 82 81 80 90 90 -300 90 8 8 2 14 6 08 7 8835 0 88 90 92 50 70 60 91 89 -250 89 7 60 90 92 93 90 6 85 47 88 92 -200 7 6 80 0 820 81 83 84 85 86 87 100 0 6000 94 91 -150 60 7 92 -100 805 17 2 86 4 8807 0 936 89 150 89 08 80 91 88 13 2 92 91 90 7 60 -50 88 87 86 85 83 82 81 8084 5000 8070 81 82 83 84 85 86 87 89 88 90 80 81 82 83 84 88 85 86 87 89 90 91 8887 86 4 885 83 82 81 80 89 Speed (rpm) 0 90 89 0 88 8888 88 1356 02 87 4 90 8 8 2 14 6 08 7 8835 0 88 0 88 89 87 85 8186 83 8084 70 82 6 3000 4000 70 60 92 8887 86 4 885 83 82 81 80 7 60 89 70 6 90 89 88 91 90 88 89 87 8286 8885 8084 13 1000 2000 89 91 90 70 60 -300 6 85 47 88 91 7 6 80 0 820 81 83 84 85 86 87 91 60 70 92 6000 90 91 90 200 8887 86 85 83 82 81 8084 80 81 82 83 84 88 85 86 87 89 90 91 89 -150 5000 8070 81 82 83 84 85 86 87 89 88 90 -100 -250 4000 91 881 884 06 92 37 56 7 80 8 0 92 50 8887 86 85 83 82 81 8084 Generating torque (Nm) 3000 Speed (rpm) 0 Motoring torque (Nm) 90 92 91 2000 88 87 86 85 83 82 81 8084 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 89 88 90 91 92 1000 89 805 86 4 3 26 8807 0 917 89 93 250 92 0 88 87 85 8186 82 83 8084 70 6 91 90 96 90 88 89 87 8286 8885 13 8084 91 90 100 p 2 0 4 0 8 8 8057 816 6 8837 8 89 91 90 92 50 150 y 90 93 200 92 92 100 91 881 884 92 06 37 56 7 80 8 0 250 90 90 150 -200 g 300 4 2 1 0 86 8 805 6 883778 89 91 2 0 4 0 8 8 8057 816 6 8837 8 89 91 200 -50 p 90 90 250 0 y 70 6 90 8 8 2 14 6 08 7 8835 0 88 89 88 82 80 Efficiency (%) g 300 300 60 70 City driving cycle loads (UDDS) 8887 86 85 83 82 81 8084 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:
  • 19. 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
  • 20. 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
  • 21. 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)
  • 22. 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 - $150-980 Reduction in consumer 0 purchase price* * Assumes materials-cost/consumer-price ratio = 40% 22 | Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013
  • 23. 9. Cost of increased battery capacity to cover increased motor losses Using a copper rotor induction motor can require the vehicle designer to increase the battery size by ~7%. This would allow a customer to perceive no difference in overall vehicle performance. Key assumptions used in costing the required increase in battery capacity: • • • • • Motor must at some time provide all motoring and braking torque in the highway driving cycle (like a plug-in hybrid electric vehicle) Induction motor uses 7% more motoring energy than a permanent magnet motor Induction motor recovers 6% less braking energy than the permanent magnet motor Total braking energy is 20% of the motoring energy over the driving cycle 75% of battery energy is used for motoring, 25% for auxiliary systems (cabin conditioning, lights, radio, electronics) 23 | Comparison of IM & PMM in a hybrid electric car - Tokyo - July 2013
  • 24. 10. Break-even for using copper motor induction motor Induction motor cost savings ($) 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
  • 25. 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 89 87 86 8885 13 8884 02 0 1000 2000 88 87 85 8186 82 83 8084 70 6 3000 89 91 90 4000 88 91 90 886 06 05 4 3 8817 0 927 89 88 87 86 85 83 82 81 8084 5000 6000 60 70 80 81 82 83 84 85 86 87 88 89 90 91 92 88 60 70 81 4 3 89880 5 6 7 82 8 86 90 91 92 50 100 84 90 92 90 150 60 70 8180 82 835 84 86 887 88 89 90 90 91 60 70 80 81 82 83 84 85 86 87 8 90 89 8 91 92 91 881 884 93 06 27 58 7 60 0 8 200 92 93 94 90 91 92 100 88 90 150 Motoring torque (Nm) 90 91 92 92 250 4 8 03 6 885 0 681888 782 7 89 90 94 16 60 4 3 8 8 8057 8827 8 89 91 200 96 300 Efficiency (%) 60 70 80 81 82 83 84 85 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 88 87 89 86 85 84 83 82 81 80 2000 1000 92 91 90 8889 87 86 85 84 83 80 82 81 4000 3000 Speed (rpm) 84 608 7817 88 4 3 6 5 2 89880 89 88 87 86 85 84 83 82 80 81 6000 5000 82 80 Efficiency (%) Copper rotor induction motor
  • 26. Main conclusions from this work • Comparing a 50kW copper-rotor induction motor to a 50kW permanent magnet motor: • • -25% torque density • • No rare earth metals used +40% weight • +10-15% peak inverter current However, the induction motor is a good alternative because: • • It uses only $260 in extra energy over 120,000 miles • • Total motor+inverter unit costs are $60-$390 less (=$150-980 lower sticker price) 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%
  • 27. 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