An Online Rotor Flux Estimation Technique Based on Intermittent Stator De-Energization for Rotor Temperature Estimation of Permanent Magnet Machines

Temperature monitoring of the permanent magnet (PM) is crucial for a reliable operation of PM machines. Overheating is the main reason leading to demagnetization of PM, which may lead to catastrophic failures. Nevertheless, direct measurement of the temperature of the PM on rotor is difficult for PM machines. Based on the linear correlation between the PM temperature and flux, a novel method is proposed in this article for PM temperature online monitoring utilizing the backelectromotive force of one specific phase, which is acquired through intermittent de-energization of the stator winding during the motor's normal operation. Matched with the estimated speed derived through a sliding window algorithm, the precise PM flux and corresponding temperature estimation can be obtained. Simulation and experimental tests are conducted to verify the accuracy and feasibility of the proposed method. It is shown that this method is capable of providing online monitoring of PM temperature with errors less than 4.5 degrees C, which is feasible in most applications. The advantage of the proposed method is its nonintrusiveness, i.e., no additional temperature sensor or modification is required inside the PM machine.