Partial Demagnetization Fault Analysis and Diagnosis for Fractional Slot Concentrated Winding PMSMs Based on DQ-Axis Components

As one of the most widespread faults in permanent magnet synchronous motors (PMSM), demagnetization faults can dramatically degrade the performance of the motor system. Extensive research has been conducted on partial demagnetization faults in existing literature, providing the harmonic range of the back electromotive force (EMF) when demagnetization faults occur. In order to enhance the specificity of fault characteristics in practical application scenarios, this paper analyzes the characteristic faulty signature associated with motor topologies in the back EMF and currents for fractional slot PMSMs experiencing partial demagnetization faults. The back EMF reduction model under faulty conditions is constructed. An analysis is conducted on the specific faulty harmonic components of PMSMs with three distinct pole-slot combinations, using the dq-axis reference frame. The research reveals that in concentrated winding fractional slot PMSMs, the specific harmonic order of partial demagnetization fault in the dq-axis is determined by the ratio of the number of slots to the number of pole pairs. The effectiveness of the proposed conclusion is validated by finite element (FE) simulation and experiment results.