Optimal sizing of motor — Battery system for in wheel electric vehicles

Electric vehicles (EV) have become popular because of environmental concerns. In order to improve the efficiency, vehicles with in-wheel motors are used, eliminating the need for a gear box. The use of in-wheel motors for lighter vehicles such as scooters and bikes is widespread. The main requirements of an in-wheel motor are high power density and efficiency along with rugged construction. Further, the space available for the motor is constrained. It is shown in this paper that for the minimum size of the motor with insignificant effect on inverter kVA rating, it is beneficial to operate the motor primarily in the constant torque region of its characteristics. Brushless DC motor (BLDC) is most widely used for in-wheel EV application. However, in this paper Segmented rotor Switched Reluctance Motor (SSRM) is considered for its rugged construction, fault tolerant operation, less initial cost and higher reliability. Further, regenerative braking of SSRM for in wheel electric vehicle is investigated and the optimum braking strategy is determined. Reduction in battery capacity due to regenerative braking is estimated.