Efficiently modeling rotor eccentricity in switched relcutance machines

Practical experience has shown that parasitic effects such as rotor eccentricity can have crucial influence on the performance of switched reluctance machines. Strong eccentricity can even be a knock-out criterion as it potentially causes additional acoustic noise and increased bearing wear. Nowadays only very few publications consider simulation methods without online finite-element analysis regarding the topic of rotor eccentricity. This paper develops a look-up table based representation of rotor eccentricity which uses time-consuming finite-element analysis only in a preprocessing step. Hence, different operating points can be calculated very fast. The standard models of centric machines were extended to cover static and rotating eccentricity. It was found that the type of coil connection determines whether a flux-based or a current-based model has to be applied. The simulation results show that coils which are connected in parallel are strongly preferable to a series-wound configuration. The parallel type greatly lowers the unbalanced magnetic pull such that acoustic noise and bearing wear is limited.