Accurate Demagnetization Analysis of Outer Rotor In-wheel Motor Under Braking Condition

In this paper, considering the effect of iron saturation and motor drive system, a decoupling demagnetization analysis model is proposed to efficiently analyze the demagnetization of outer rotor in-wheel motor under braking condition. The accuracy of the proposed model is verified by the direct co-simulation model and the simulation speed is more than 100 times faster. Then, the max demagnetization ratio (MDR) and the average demagnetization ratio (ADR) of various current amplitudes and angles are evaluated explicitly to analyze the influence of different dq-axis current on demagnetization. It is found that both large current amplitude and demagnetizing magnet field will intensify the demagnetization level. The influence of PWM switching frequency, drive performance, motor speed and moment of inertia on demagnetization are analyzed. It is concluded that higher PWM switching frequency, smaller current amplitude overshoot and smaller demagnetizing magnet field in motor drive can effectively reduce demagnetization under braking condition.