Online Diagnosis of the Interturn Fault for Permanent Magnet Machines Based on Voltage Oscillation Characteristic

Interturn short-circuit is typical asymmetrical fault of stator windings. The online diagnosis is significant for preventing the slight fault from further development into serious failure. To realize accurate detection of incipient interturn fault, specific oscillation modes involving entire phase winding are designed, which is generated during the cut-off transient process of antiparallel diode. Based on the characteristic frequency, the ratio of inductances between three phases can be calculated, which reflects the severity of the asymmetry between three phase windings. In the meanwhile, the oscillation frequency is not affected by the operating condition, which can be regarded as an inherent property of stator windings. This provides a superiority for online condition monitoring. In addition, the asymmetric fault of permanent magnet, such as the partial demagnetization, can be accurately distinguished. Online experimental tests are conducted to verify the feasibility of the proposed strategy.