Influence of Inter-turn Short-Circuit Fault Considering Loop Current on Electromagnetic Field of High-Speed Permanent Magnet Generator with Gramme Ring Windings

As a kind of emergency power supply in military field, the high-speed permanent magnet generator (HSPMG) has attracted wide attention to its healthy condition. The loop current (LC) of the inter-turn short-circuit (ITSC) fault seriously endangers the generator unit operation stability and power supply reliability. In order to study the influence of pulsating magnetic field produced by LC on the electromagnetic field, the two-dimensional finite element model (FEM) of the 117 kW, 60000 rpm HSPMG is established. By comparing calculation result and test data, the accuracy of the model is verified. The field-circuit coupling method is used to reveal the change mechanism of magnetic field symmetry when ITSC fault occurs. By comparing the spatial distribution of the air-gap flux density, the relationship among the spatial distribution of the air-gap flux density, the elliptical rotating magneto-motive force (MMF) and the current phase angle is determined. The variation of the amplitude of the air-gap flux density space harmonic under different fault degree is studied, and the fault characteristics of ITSC fault are obtained, which provides a reference for ITSC fault diagnosis and fault degree identification. In addition, the research also laid a theoretical foundation for the next analysis of the loss and temperature field.