Optimal Design of a Spoke-type Permanent Magnet Motor for Extension of its Speed Range

Abstract

This paper presents the optimal design for a spoke-type permanent magnet (PM) motor to extend the speed range of its constant power region. This is accomplished by optimizing the three design factors of the leakage reluctances without decreasing the maximum attainable torque. To extend the speed range of the PM motors, the characteristic current has to be the same as the maximum current of the inverter. First, by analyzing the magnetic equivalent circuit (MEC), it is deduced that the characteristic current is affected by the leakage reluctances that are sensitive to the stator slot opening width, rotor slot opening width, and rotor shaft rib length. Next, the effects of the three design factors on the speed range of the spoke-type PM motors are investigated using sensitivity analyses. Moreover, the three design factors are optimized using the finite element method (FEM) such that the characteristic current is the same as the inverter’s maximum current. Finally, it is verified that the characteristic current and the inverter’s maximum current values can be matched so that the speed range of the optimal model is extended without decreasing the maximum torque compared to the initial model.