Slot combination for electromagnetic noise suppression of EV driving induction motor

Designs with high torque, wide speed range and light weigh are pursued by motor designers for electric vehicle (EV) drives. Such designs have resulted in a wide frequency band of the normal electromagnetic force acting on stators and rotors of motors. The maximum frequencies of the electromagnetic forces are likely to be close to or higher than the corresponding modal frequencies of the motor structure, which will produce big electromagnetic noise. A slot combination selection method was analyzed for the suppression of electromagnetic noise produced by EV driving induction motors. The orders and maximum frequencies of the possibly existed electromagnetic forces were predicted for different slot combinations. The normal modal frequencies of the motor structure were computed by the finite element method. The maximum frequencies of the electromagnetic forces were compared with the modal frequencies of the motor structure at the speed range of EV driving induction motors. In the condition of enough torque, the slot combination, whose maximum frequencies of electromagnetic forces are lower than and far from the corresponding modal frequencies of the motor structure, is chosen.