Experimental determination of stator winding failure behavior

In the design of fault-tolerant or fail-safe systems, detailed knowledge of potential failure processes is required. One failure mode in electrical machines is an inter-turn, or turn-to-turn short-circuit, which can cause very large local heating and subsequently, progression of the fault. This paper experimentally determines the failure process and mode of enameled wire coils after occurrence of an initial fault. Step currents are applied to dummy coils and the failure process is monitored. Various current levels are applied to single and three layer coils. The results demonstrate a high repeatability between identical tests; a calibrated adiabatic model can predict the time-to-failure. Stepwise changes in the terminal resistance indicate that failure of individual turns occurs and can be distinguished. Lastly, the results prove that that multilayer coils can sustain larger total currents due to formation between the layers.