Research on the Stator Inter-turn Short Circuit Fault Diagnosis Method of PMSM Based on the Continuous Spectrum Zoom

Stator inter-turn short circuit fault is the cause of most occurring stator faults, and thus whether this fault can be detected in time is the key to ensure the operation reliability of the permanent magnet synchronous motor. The magnitude of the third harmonic in motor current can be used as the stator fault signature. However, in practice, as a result of small amplitude and spectrum leakage, it is difficult to extract the third harmonic component correctly, leading to misdiagnosis. To solve this problem, a continuous spectrum zoom Fourier analysis method based on the FFT and FT is proposed to correct the spectrum error, which has advantages of high frequency resolution and high amplitude calculation accuracy. Firstly, the cause of the third harmonic characteristic in motor current is analyzed. Then, the principle of continuous spectrum zoom method is introduced briefly. Furthermore, the extraction of the characteristic is described as three steps: fundamental frequency calculation, third harmonic frequency and its zoom frequency range computation, and the continuous spectrum zoom analysis. Finally, the experimental results verify the proposed continuous spectrum zoom method. It can be seen from the results that the amplitude of the third harmonic of the fault motor is larger than that of the health motor, where the amplitude increases as the number of the shorted turns, which proves that the third harmonic in motor current is an effective component to recognize the stator inter-turn short circuit fault.