In a hybrid electric vehicle (HEV), an interior permanent magnet (Nd-Fe-B) synchronous motor is widely used. However, the flux density of the Nd-Fe-B magnet is sensitive to the temperature variation. Particularly, in a HEV, the heat coming from internal combustion engine causes high temperature rise of the motor. It degrades the flux density and output torque. In this paper, a maximum torque per ampere (MTPA) control scheme for IPM motor is proposed considering the temperature dependence of the magnet field. With the use of an empirical look-up table, saturation effect is also considered. The effectiveness of the proposed control method is demonstrated through MATLAB/Simulink simulation and experiment.
