Magnet Temperature Estimation of Traction Motor in Standstill With Considering Spatial Harmonics

Abstract

In this article, a magnet temperature estimation method applicable to an interior permanent magnet synchronous machine (IPMSM) at a standstill has been newly devised. First, it is analyzed that an inductance of IPMSM varies according to not only a magnet temperature but also a rotor angle, which is spatial harmonics. The analysis is verified in a small-scaled motor-generation set (MG-set), where magnet temperatures can be directly measured. Based on the analysis and experimental results, it is demonstrated that spatial harmonics can make no negligible error in the magnet temperature estimation. Therefore, the estimation method has been newly devised in this article, considering spatial harmonics. As a result, the devised method can reduce the maximum estimation error from 25.3 to 6 degrees C based on experimental results in the small-scaled MG-set. Additionally, the devised method has been verified as feasible for use in the small-scaled motor and the traction motor of a mass-produced electric vehicle. As a result, the proposed method can estimate the magnet temperature accurately at every rotor position of both motors. Through this online estimation, the maximum estimation error is less than 5 degrees C even when the stator winding temperature is varying in both a small-scaled motor and the traction motor.