Modified Halbach design for torque profile improvement in a permanent magnet synchronous motor dedicated to an electric city bus

Abstract

In this work, a permanent magnet synchronous motor is designed for an electric city bus. The unit winding factor is considered for torque capability enhancement and completely open slots are adopted for low-cost rectangular wire winding implementation. Accordingly, extremely large pulsating torques that are predictable should be mitigated through the rotor design possibilities. In this regard, a modified Halbach pole configuration, named axially segmented Halbach, that is capable of producing considerably smooth torque as well as retaining the large mean torque is proposed. First, an optimised conventional Halbach array is calculated as the initial design. Then, following a detailed introduction to the new design concept, the modified Halbach pole parameters are obtained through the proposed 2D model-based optimisation algorithm. A rotor step skewing scheme is also evaluated to make the final comparisons, which are carried out via 3D FE models. The results demonstrate the admirable performance of the proposed Halbach configuration as an effective solution for torque profile improvement.