Electromagnetic thermal coupling characteristics of permanent magnet synchronous motor for electric vehicles

To investigate the influence of the internal temperature change in an automotive permanent magnet synchronous motor on the electromagnetic parameters and output performance of the motor, motor temperature, motor loss, magnetic saturation, and other factors were considered comprehensively. A motor electromagnetic thermal dynamic coupling model under maximum torque per ampere (MTPA) and weak magnetism control was established. The electromagnetic-thermal coupling characteristics of the motor under ideal three-phase current excitation, as well as the dynamic, vibration, and energy consumption characteristics of the motor under MTPA and weak magnetic control, were studied. Under ideal three-phase current excitation, an increase in the motor temperature caused a decrease in the motor magnetic field strength, alternating flux, and magnetic circuit saturation degree, which reduces the motor induced electromotive force and flux linkage. This resulted in a decrease of 5.7% and 13.5% in the mean values of the electromagnetic torque and pulsation amplitude respectively, and a decrease of 9.5% in the mean value of the radial electromotive force compared with the initial temperature. Under MTPA and weak magnetic control, the mean value of the electromagnetic torque was basically unchanged with increasing temperature. Its pulsation amplitude decreased by 8.4%, and the main harmonic components of the electromagnetic torque and radial electromagnetic force decreased compared with the initial temperature, indicating that the electromagnetic vibration caused by both was lower than that at the initial temperature. With increasing temperature, the stranded loss increased by 45.2% from the initial temperature of 22°C, which is greater than the core loss decay of 8.26%; The total loss increased by 9% from the initial temperature, and the efficiency decreased by 0.84%.