Stator Winding Temperature and Magnet Temperature Estimation of IPMSM Based on High-Frequency Voltage Signal Injection

Abstract

The interior permanent-magnet synchronous motor (IPMSM) has been widely used as the traction motor in electric/hybrid vehicles because of its high torque density and wide operating speed range. During the operation of the IPMSM, the stator winding temperature and magnet temperature should be monitored to prevent winding insulation breakdown and irreversible demagnetization and to improve the torque accuracy. This article devised a method involving the use of a high-frequency (HF) resistance and an HF inductance for estimating these two temperatures at low motor speeds. The relationship between the HF impedance and both temperatures was determined and verified using an experimental setup in which both temperatures could be measured. Based on the relation, the temperature estimation method has been proposed, in this article, and verified by the experimental test. The proposed method was used to estimate the stator winding and the magnet temperatures simultaneously for 6000 s, and the maximum error was 6 °C and 3 °C for the stator winding and magnet temperature, respectively, even when the load and the temperatures varied considerably.