Optimal Design and Control of a Spoke-Type IPM Motor with Asymmetric Flux Barriers to Improve Torque Density

Abstract

This paper studies the optimal design and control scheme of a spoke-type interior permanent magnet motor (SIPM). An asymmetric rotor structure with flux barriers is designed to improve the torque density of SIPM. The design method improves the torque density by approximating the maximum value of the magnetic torque and the reluctance torque, wherein the torque components are separated by the frozen permeability method (FPM) to evaluate the contribution. This scheme does not increase the amount of permanent magnets or the motor size, and reduces motor weight while increasing motor torque output. Firstly, the asymmetric flux barriers are applied in a 27/4 SIPM to illustrate the design principle. Further, by optimizing the width of flux barriers, based on finite-element analyze (FEA), a higher torque density is obtained. Compared with the basic model, the output torque and the torque density of the optimal model are both increased. Based on the optimal model, an angle scanning method is proposed to orient the flux vector and dq-axis. Then, the mathematical model of the optimal model is established, and the maximum torque per ampere (MTPA) control system is designed. Compared with the conventional control system, the proposed control system has a higher torque per ampere (TPA), which shows that the designed control system can give full play to the advantages of the high torque density.