A vernier permanent magnet motor with high power factor for electric vehicle applications

Abstract

Electric vehicles require the motor to provide enough torque to meet the requirements of short-term acceleration and maximum climbing. Due to the limited package size, there are strict requirements on the size of the motor. PMVM motors have the advantage of high torque density and have broad development prospects in electric vehicles. This paper summarizes previous research on permanent magnet vernier motors and proposes a surface-mount Halbach array PMVM. The main contents are as follows: First, the development and research status of permanent magnet, vernier, and Halbach array motors are introduced. The PMVM magnetic gear effect and the magnetic field modulation principle are deduced using the formula. Through the power factor phase diagram and expression, two methods to improve the power factor are proposed. The reason for the enormous torque of PMVM is explained by formula derivation. The advantages of the Halbach array are analyzed from the perspective of magnetic field line distribution and air gap flux. The principle of magnetic field modulation of Halbach array PMVM is deduced using the formula, which provides a theoretical basis for motor design. Second, a surface-mount PMVM was designed and compared with a surface-mount PMSM of the same size through finite element analysis to study the performance of the two motors. The software simulation results show that the designed PMVM has higher output torque, lower cogging torque, higher no-load back EMF, higher iron loss, and lower power factor. Finally, a Halbach array PMVM is designed, and its performance is compared with traditional PMVM and traditional PMSM. The results show that the Halbach array PMVM has the highest output torque, the lowest cogging torque, and the highest no-load back EMF among the three motors. Compared with the traditional PMVM, the power factor of the Halbach array PMVM is greatly improved, and the ideal effect is achieved.