A cost-effective design approach for permanent magnet brushless machines

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