Analysis of a fractional slot permanent magnet machine for a series hybrid truck

Purpose - The purpose of this paper is to discuss the performance of a proposed machine design for an in-wheel motor with the required torque-speed characteristic. Design/methodology/approach - Calculation of the winding factor of the machine with the star of slots theory is performed first. The field weakening capability of the machine is investigated and the operating speed range is determined. The tooth contour modeling method for calculating the performance of the machine with a limited number of elements is introduced. The method is used to construct two models of different complexity and the results obtained with the models are compared with the results obtained by finite element models. Findings - The 14 pole 12 slot in-wheel PMSM discussed in this paper is able to meet the stringent performance requirements. The results obtained with the tooth contour models show good agreement with the results obtained with finite element models despite the limited number of elements. Increasing the number of elements in the model allows for modeling of armature reaction and increases the accuracy of the model. Research limitations/implications - This work can be continued with investigating the possibilities to model the armature reaction more accurately. Originality/value - This paper proposes a modeling method which accurately describes the performance of a PMSM with limited number of elements. With this method, the calculation procedure can be easily used for optimization of the machine design.