The motor magnetic core size for inductance are inverse with rising magnetic field frequency before eddy current losses start to rise with higher order effects.
- 8 pole motor has 3 phases and 2 slots per phase per pole seems to optimize the weight, torque, power over a wide speed range for their load using rotating rare earth magnets.
Torque current is inverse to winding resistance so optimization is done to minimize L/Rs=T for commutation cycle 1/f while minimizing RsDCR for no load and full load.
Commutation losses are reduced significantly with commutation frequency with dead-time-shoot thru fixed at max current losses proportional to f switch.
The Nissan LEAF motor specs are;
Brushless Interior Permanent Magnet
Litz eqjuiv 20 x AWG20
max RPM 10,390 = 173Hz
Max power 80 kW
Goal: constant power & high Efficiency (Torque*RPM) from 2000 to 8000 RPM is almost achieved
Goal to minimize core loss and copper loss are tradeoffs with hot spot rise @ 7,000 RPM, torque vs Hp in this design yet 90% of losses are choice of low core loss yet copper peak losses are 1.5x core loss for short durations during acceleration.