A Cost-Effective Design Approach for Permanent Magnet Brushless Machines

Abstract

Small-power electric machines that use permanent magnets for providing field excitation are becoming increasingly attractive for use in various industrial applications, including those with high-torque requirements andspace limitations. There exists a wide range of designs based on different topologies and different types of magnetic materials. The cost-effectiveness of permanent magnet (PM) machine designs couldbe affected to a great extent by the choice of the magnet material, the overall size of the machine, and the selection of the most appropriate materials, taking into consideration their relative costs and properties. This paper presents an analytical approach to design a surface-magnet electric machine with optimum use of materials on cost basis. Influence of major design parameters is examined, as well using sensitivity analysis. The results show that the optimum split ratio is inversely related to the remanence of the chosen magnet. Also, the impact of the core saturation level on the overall machine cost is investigated.