Harmonic superposition of conductor losses in switched reluctance machines

Commonly known analytical prediction methods for winding loss in switched reluctance machines provide comparatively inaccurate results but are very fast. Finite element analyses, however, yield rather exact results but at high computational cost. This paper introduces harmonic superposition as a third approach that promises sufficiently accurate loss estimations at low computational cost. At that point, the method of superposition, which is also used in all analytical methods, is reinvestigated. Conventional analytical approaches use analytical approximations to calculate the harmonic loss components, which are superposed. The proposed approach determines the harmonic components by finite element analyses during a one-time preprocessing step. The results of this pre-simulation are examined by calculating the resistances of every single conductor. Their dependency on frequency, rotor position and current is presented. In addition to the improved calculation of the harmonic components, a modified superposition method is presented. This modified superposition method takes leakage flux and saturation effects into account. Both superposition methods are applied at an exemplary operating point and the results are compared to a transient finite element simulation. Simulation results are presented for an automotive SRM.