Short-circuit faults in high-speed PM machines with parallel strands and coils

Abstract

Electrical machines for safety critical applications need to be able to withstand all possible short-circuits, including those between individual turns. In high-speed machines multiple parallel strands may be used to reduce AC losses in the winding, increasing the likelihood of a turn-level short-circuit. This paper considers the consequences of using parallel strands on the short-circuit losses. Additionally, the effect of using a PWM voltage supply is also considered. It is found that using multiple parallel strands reduces the local losses that occur during a short-circuit, but at the same time slightly increases the total losses. Also, local fault currents can be reduced better with a remedial terminal short-circuit when using parallel strands, suggesting a small safety benefit. The effect of supply voltage harmonics on the maximum short-circuit losses is found to be negligible.

Impact of SiC semiconductors switching transition speed on insulation health state monitoring of traction machines

“…Another issue is that remaining life cannot be ascertained. Especially methods that are presented in [20][21][22][23] to diagnose insulation problems are better suited for detection of an existing fault than detecting an imminent degradation of turn-to-turn insulation of the stator winding.…”