Non-Uniform Demagnetization Detection Considering Load Unbalance for SPMSMs Based on Motor Current Derivative Analysis

In the literature, motor current signature analysis (MCSA) has been widely used in the fault diagnosing of non-uniform demagnetization (NUD) for permanent magnet synchronous motors. However, motor current is affected by quantities of factors such as unbalanced load, and MCSA is also unable to directly and quantitatively assess the severity of NUD fault. To deal with the drawbacks of MCSA, a NUD fault identification method based on motor current derivative analysis (MCDA) is proposed in this paper. Using MCDA, the major information of back electromotive force (EMF) can be acquired when the motor is under working condition. Extracting the fault-related harmonics in the acquired back EMF, NUD fault can be detected. Compared with MCSA, both the sensitivity and quantitative evaluation of NUD fault are improved using the proposed MCDA method. Experiments with healthy and non-uniformly-demagnetized SPMSMs are carried out to implement the algorithms of NUD fault diagnosis, and the results can validate the effectiveness of proposed MCDA method and its robustness to external load disturbance.