I. Introduction
The unique structure of the PMSM allows it to be used in a wide range of industries, but it also comes with some drawbacks [1]. The high power density and small size of PMSM lead to more losses per unit volume of the motor than other types of motors, and the limited heat dissipation conditions of the motor inevitably make the motor temperature rise [2]. When the temperature is too high, it will affect the electromagnetic performance of the motor, motor efficiency, etc. In addition, the winding resistance and magnetic chain parameters of the motor will change with the temperature change. At present, most of the thermal analysis of the motor is still chosen to analyze the steady-state temperature, while most of the control strategies rely on the temperature-sensitive stator winding resistance and magnetic chain parameters, so the steady-state temperature analysis is not conducive to the transient control of the motor, and the real-time thermal analysis of the motor will help the motor control and motor design. Due to the limitations of motor structure, size, and the number and location of sensors, it is difficult to measure the motor temperature by filling in thermal sensors. Therefore, it is necessary to estimate the transient temperature of the motor online.