Implications of shorted turn faults in bar wound PM machines

The paper discusses the effect of single turn short-circuits in the windings of fault tolerant permanent magnet machines. It is shown that previously recognised methods for dealing with shorted turns do not work for larger bar-wound machines, and a new method for protecting the windings against single turn faults is therefore proposed. The new method depends on rapid detection of the fault and injection of a current (of appropriate magnitude and phase) into the faulted winding. The paper gives a theoretical analysis supported by finite element simulations of the fault conditions and illustrates these with a case study taken from the aerospace industry.