Eccentricity Fault Diagnosis in Multimodule Permanent Magnet Synchronous Machines Based on Zero-Sequence Voltage Component

Multimodule permanent magnet synchronous machines (PMSMs) are identified as a better choice for superior fault-tolerant ability. However, as one of the most common faults, eccentricity makes the performance of PMSMs deteriorate. Without timely diagnosis and maintenance, negative effects caused by eccentricity further worsen the fault severity, even resulting in catastrophic accidents. In this article, the inherent rotational asymmetry of partition stator in multimodule PMSMs is utilized in the proposed zero-sequence voltage component (ZSVC)-based eccentricity fault diagnosis method with advantages of noninvasiveness, higher sensitivity, and the capacity to differentiate eccentricity types. Specifically, different from the previous ZSVC-based method monitoring multiple harmonics, the proposed method achieves that only the dominant 3rd ZSVC harmonic is extracted by short-time Fourier transform (STFT) in each unit of multimodule PMSMs. The variation of 3rd harmonic amplitude with rotor position shows asymmetry feature under static eccentricity (SE), fluctuation feature at mechanical rotating frequency under dynamic eccentricity (DE), and the above features under mixed eccentricity (ME). Then, the fault indicators are defined to detect the different eccentricity types. Furthermore, the influence factors are discussed exhaustively. Finally, experiments are implemented on an 8-pole/48-slot 4-module PMSM with SE shields and DE rotor to verify the effectiveness of the proposed approach.