Optimal Design of Spoke-Type IPM Motor Allowing Irreversible Demagnetization to Minimize PM Weight

Abstract

In this study, we introduce an optimal design for a spoke-type interior permanent magnet (IPM) motor that can minimize PM weight by allowing irreversible demagnetization, unlike the conventional motor design method that does not allow irreversible demagnetization. The spoke-type rotor structure has the advantage of concentrating the magnetic flux around the rotor core. However, part of the PM near the surface of the stator tooth becomes sensitive to the armature reaction and external magnetic factors. Therefore, typical spoke-type rotor construction follows a limited design process that does not allow irreversible demagnetization. Although the manufacturing process allows tolerance for the demagnetization rate, motor design without considering the demagnetization rate in all the design stages becomes a design constraint and limits the performance area. In this study, the performance improvement is examined, when irreversible PM demagnetization is allowed up to −3%, and is not zero. For optimal design, Latin hypercube sampling (LHS), the kriging model, and genetic algorithm (GA) are utilized. With the proposed design process, motors are effectively designed to reduce the PM weight by 23.7%, compared to the initial design model while maintaining an efficiency almost similar to that of the initial design model.

Keywords

• Brushless AC motor
• spoke-type interior permanent magnet motor
• NdFeB magnet
• irreversible demagnetization
• demagnetization rate
• armature reaction