Magnet eddy-current losses in interior permanent magnet machines with concentrated windings - Analysis and reduction of the major source

This paper deals with an analysis of the major source of magnet eddy-current losses in interior permanent magnet machines with traditional concentrated windings. An analytic model suitable for this type of machine is derived and employed to understand the flux density variation inside the magnets. On the basis of the model, the key differences between even- and odd-numbered stator harmonics are derived and important factors influencing harmonic flux pulsations inside the magnets are deduced. A parameter study is performed using the analytic model to highlight the particular significance of the pole arc to pole pitch ratio. The results are, consequently, compared to the FEA yielding a good agreement. By taking the findings into account, an improved design of a traction machine with clearly reduced magnet losses is developed.