Uniform demagnetization fault diagnosis in permanent magnet synchronous motors by means of cogging torque analysis

A demagnetization fault in permanent magnet type motors is a common fault that can lead to deterioration of the machine performance, and would introduce secondary problems. Detection of this type of fault, and establishing diagnosis methods to detect such a fault, requires knowledge of a motor working principles and its structure. Moreover, a uniform demagnetization type of fault is extremely hard to detect, because it results-in no asymmetry in the output/terminal signals, and hence, motor current signal analysis (MCSA) methods fail to diagnose such faults. In this paper, internal permanent magnet synchronous motors (IPMSMs) with two different rotor configurations are studied/simulated using a two-dimensional finite element (2D-FE) method, by means of which the cogging torque signal is computed under healthy and faulty conditions. Uniform demagnetization is studied and a proper fault diagnosis index is introduced which can successfully detect this type of fault.