Optimal Design and Cogging Torque Minimization of a Permanent Magnet Motor for an Electric Vehicle

With the increase of electric vehicle mobility, the integration of an electric motor inside the vehicle wheel is an interesting architecture for electric vehicles. This solution has the advantage of a great compactness of the motor and the elimination of mechanical transmission. This paper deals with the analytical modeling and the optimal dimension's finding of an in-wheel motor. An optimization procedure, based on Sequential Quadratic Programming SQP, is performed. The main objectives are the minimization of the machine weight and the maximization of its efficiency. While respecting constraints, an optimal machine with a weight of 11.61 kg and an efficiency of 93% is reached. To verify the satisfaction of the design requirements and the motor performances, finite element analysis (FEA), was applied. The comparison of induction results shows a good accuracy with a maximum error of 14%. The output torque and the air gap flux density are assessed. A maximum output torque of 90 Nm is achieved, and the slotting effect is noticed. Then the cogging torque of the machine is investigated; different rotor structures were studied. It is concluded, from results, that the topology with circular segmented magnets has the lowest cogging torque which does not exceed 7 Nm.