기계적 피로를 고려한 EV용 IPMSM의 회전자 특성 해석

Abstract

Due to the recent oil energy exhaustion and the strict environmental regulation, the development of vehicle for the future with new method is being widely studied replacing the existing engine driving method. Therefore, hybrid electric vehicle (HEV), electric vehicle (EV), and plug-in hybrid electric vehicle (PHEV) are being actively developed in order to replace the conventional diesel-powered or gasoline-powered vehicles that are targeted as the major cause of air pollution. In case of HEV, it's already in the market for sale. The requirements for performance of this type of EV traction motor are high torque, high speed, high power, high efficiency and miniaturization. The Interior Permanent magnet Synchronous motor (IPMSM) for EV traction increases in output value per unit volume. However, the rotor of IPMSM is connected directly to the mechanical load rotating in high speed, thus the stable stress must be evenly distributed and designed to tolerate the critical speed. Therefore the structural design of rotor becomes an important technology. When designing the structure of rotor, the width of centerpost according to the magnet position affects the operation characteristics of the IPMSM. When the width of centerpost is narrowed, its sending all the magnetic flux generated by the magnet of rotor toward the air-gap direction eventually increasing the torque. However, when the width of centerpost is narrowed, that increasing highly the risk of damage or destruction of IPMSM by centrifugal force in case of high speed driving. Therefore, in this paper width of centerpost which affects the performance characteristics of IPMSM has been adjusted and the characteristics of IPMSM according to this adjustment have been examined with 2-D numerical analysis using finite element method. Moreover, the stress analysis has been performed to test the structural safety of IPMSM and guarantee the safety factor of centerpost. As the result, it was confirmed through the electromagnetic field analysis that the operation characteristics of IPMSM were more improved when the width of air-barrier got wider. Cogging torque did not show significant effect on the width of air-barrier. However, in case of both the average and maximum torques about 2 % of increase was obtained depending on the adjustment of width of air-barrier. Moreover, we verified that the torque ripple which exerts harmful influence on the driving characteristics of IPMSM became lesser when the width of air-barrier got wider. Also, the optimum width of structural limit of air-barrier's width was confirmed through the stress analysis by grasping the stress of centerpost.