Identification of Demagnetization Faults in Axial Flux Permanent Magnet Synchronous Machines Using an Inverse Problem Coupled With an Analytical Model

This paper presents an analytical method for permanent magnet demagnetization detection in an axial flux permanent magnet synchronous machine. First, a forward model is built to calculate the three phase terminal voltages with inputs of three phase currents, the geometry of the machine, and the electromagnetic properties of the machine. To model the demagnetization fault, the scalar potential equation is solved. The magnetization waveform is a square wave corrected with magnetization factors that represent the individual magnetization of every magnet. Second, the forward model is inverted so that the magnetization factors are computed out of the three phase currents and the three phase terminal voltages. The forward model is validated with experimental data and finite element simulations.