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.
A known drawback of interior permanent magnet synchronous machines are the high eddycurrent losses in the stator teeth, especially in the field-weakening region. For a deep analysis of this phenomenon, an analytic loss modeling approach solely based on fundamental machine parameters like the inductances, the permanent magnet flux, and the magnet configuration is derived. Due to its formulation, the method allows a hybrid modeling with numerically calculated inductances and thus yields reasonable results even at the presence of saturation. It provides a deep understanding of key influencing parameters and reveals the dependency of eddycurrent losses in the stator teeth on the direct and quadrature component of the stator current. Different parameter studies are performed with the model and compared to FEM simulations to underline the validity of the derived formulation.
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