A Switched-Reluctance Motor/Generator for Mild Hybrid Vehicles

1. A Switched-Reluctance Motor/Generator forMild Hybrid Vehicles Peter Watterson, Wei Wu, Bruce Kalan, Howard Lovatt, Glen Prout, John Dunlop, Stephen Collocott CSIRO Materials Science and Engineering, Australia ICEMS 2008, 18 October 2008, Wuhan, China

2. Objectives • Low cost reduction in petrol consumption (and CO2 emission) • Mild hybrid drive for automatic car • Parallel electric motor/generator MG - Internal Combustion Engine ICE • Flywheel Alternator Starter (FAS) topology • MG to replace the starter motor, flywheel, and alternator • MG between ICE and gearbox with no increase in length • MG outside the torque converter • No additional clutch, so MG rotor fixed to and synchronous with the crank shaft CSIRO. A Switched-Reluctance Motor/Generator for Mild Hybrid Vehicles

3. Flywheel Alternator Starter (FAS) topology Internal Combustion Engine rear wheels electric motor/generator differential gearbox torque converter CSIRO. A Switched-Reluctance Motor/Generator for Mild Hybrid Vehicles

4. Motoring: cold start of the ICE low emission warm start and launch assist from ICE off at idle input power set by battery and/or supercapacitor size Generating: 2000 W over broad speed range Specification CSIRO. A Switched-Reluctance Motor/Generator for Mild Hybrid Vehicles

5. Switched Reluctance (SR) motor SR found superior to Permanent Magnet (PM) machines due to: • the broad (9:1) speed range required • the difficulty of field-weakening PM machines and the consequent high iron loss at high speed • the high ambient temperature between ICE and gearbox and the lower permissible maximum temperature for PMs • Maximised average torque by 2D Finite Element Analysis (FEA) 2D correction factors co-energy phases (3) rotor teeth CSIRO. A Switched-Reluctance Motor/Generator for Mild Hybrid Vehicles

6. Average torque by 2D FEA CSIRO. A Switched-Reluctance Motor/Generator for Mild Hybrid Vehicles

7. Lamination notching inaccuracy • Prototype had a slight step at middle of rotor tooth: stator tooth gap 0.69 mm gap 0.63 mm rotor tooth CSIRO. A Switched-Reluctance Motor/Generator for Mild Hybrid Vehicles

8. 3D FEA mesh CSIRO. A Switched-Reluctance Motor/Generator for Mild Hybrid Vehicles

9. 3D FEA solution, stepped gap CSIRO. A Switched-Reluctance Motor/Generator for Mild Hybrid Vehicles

10. 3D FEA solution close-up around gap CSIRO. A Switched-Reluctance Motor/Generator for Mild Hybrid Vehicles

11. Calculated torque v. angle, one phase active current (A) stepped gap uniform gap unaligned aligned CSIRO. A Switched-Reluctance Motor/Generator for Mild Hybrid Vehicles

12. Calculated 3-phase torque, 90 A peak, low speed smaller gap trailing averages smaller gap leading CSIRO. A Switched-Reluctance Motor/Generator for Mild Hybrid Vehicles

13. Static torque test rig SR motor load arm (1 m) scales CSIRO. A Switched-Reluctance Motor/Generator for Mild Hybrid Vehicles

14. Measured v. calculated torque, single phase current (A) calculated measured unaligned aligned CSIRO. A Switched-Reluctance Motor/Generator for Mild Hybrid Vehicles

15. Conclusions • Peak Torque 350 Nm for 6375 W input at 10 rpm for about 30 s • If volume based on cylinder then Torque/Volume = 26.5 kNm/m3 • But if volume based on annulus then Torque/Volume = 51.1 kNm/m3 • Higher torque/volume possible for greater input power. • Active masses: • Silicon steel 24 kg • Copper 4.1 kg • Specification achieved, for low machine cost and minimum modification to a production vehicle CSIRO. A Switched-Reluctance Motor/Generator for Mild Hybrid Vehicles

16. Contact Us Phone: 1300 363 400 or +61 3 9545 2176 Email: enquiries@csiro.au Web: www.csiro.au Thank you CSIRO Materials Science and Engineering Peter Watterson Principal Research Scientist Phone: 61-2-94137529 Email: Peter Watterson@csiro.au Web: www.csiro.au/science/ElectricMachines.html