Temperature Estimation of IPMSM by Using Fundamental Reactive Energy Considering Variation of Inductances

In this article, a method to estimate the temperature of an NdFeB magnet in an interior permanent magnet synchronous motor (IPMSM) has been developed in medium and high speed operating conditions. Fundamental reactive energy is newly brought out and directly used in the developed method to estimate the magnet temperature accurately, which results in higher sensitivity with respect to the magnet temperature variation compared to the conventional methods. It is because the variation of the reactive energy caused by the magnet temperature includes variations of inductances in addition to that of the magnet flux linkage. In the proposed method, a stator resistance error effect caused by a stator temperature is inherently removed without any additional temperature sensor on stator winding. Moreover, the proposed method is robust to an inverter nonlinearity effect and ac resistance effect. As a result, the proposed method can estimate the magnet temperature accurately in real time, even in load variation, regardless of the stator temperature variation. The magnet temperature estimation error has been less than 3.7 °C in the online estimation for 10 000 s under wide speed and torque variations.