Comparison of torque-to-copper loss ratio in switched reluctance and induction motors for EV applications

A comparison theory is presented for torque at starting and high speeds between a switched reluctance (SR) and a squirrel-cage induction motor (IM) of comparable size. It is shown that L_max-L_min of the SR motor corresponds to the secondary inductance L₂ in the IM and a comparison theory is developed for the starting performance considering copper loss and high-speed behavior. It is concluded that the SR motor is superior to the IM in the starting torque per copper loss and the use of continuous-current mode makes the SR advantageous at high speeds, as well.