Design and evaluation of a PM vernier machine

This paper presents the design optimization and performance evaluation of an outer-rotor vernier machine with surface mounted permanent magnets. First the design specifications of the machine are described, then the design strategy and the optimization procedure are given in detail. A prototype based on the optimum design is manufactured and experimentally evaluated. The measured performances compare favourably with the predicted ones. In addition, a comparison with a more conventional PM machine with non-overlap windings is presented. It shows that, despite the disadvantage of low power factor at high torque, vernier machines can be a competitive alternative to conventional PM machines in some applications.