Estimation of Stator and Magnet Temperatures of IPMSM From Active and Reactive Energies at Medium and High Speeds

Interior permanent magnet synchronous machines (IPMSMs) have a wide range of applications, such as in electric vehicles, home appliances, and robots, because of their high torque density and wide operating speed range. In the case of machines, the stator winding and magnet temperatures are generally crucial to guarantee the system's safety and control accuracy. This study developed a method to estimate magnet and stator winding temperature by analyzing reactive and active energies. First, IPMSM model involving stator winding and magnet temperatures was derived. In the derived IPMSM model with temperatures, a relationship between reactive energy and magnet temperature was found. Based on the relationship, magnet temperature can be estimated regardless of stator resistance information. Stator winding temperature is estimated based on the active energy using the estimated magnet temperature. As a result, the proposed method can estimate magnet and stator temperatures simultaneously, considering the speed effect on motor parameters and inductance variation with the magnet temperature. Online estimation was performed to demonstrate the feasibility and validity of the proposed method. Through the online estimation, the maximum estimation errors in magnet and stator temperatures are less than 5 °C and 10~^{\circ }\text{C} , respectively.