Influence of Rotor Eccentricity on Radial Electromagnetic Force Characteristics in Switched Reluctance Motors and Compensation

Abstract

Aiming at the problem of severe unbalanced magnetic force (UMF) of the switched reluctance motors (SRMs) caused by eccentricity, this paper analyses the radial electromagnetic force’s spatial distribution and frequencies under eccentricity and conduct a compensation method for the UMF. Firstly, the expression of the radial electromagnetic force under eccentricity is derived by using the method of magnetomotive force multiplying permeance, combining with the modification of the permeance. Secondly, the UMF is reduced by applying compensation current to the two stator poles of the permeance-descending phase. The selection of the stator poles and the calculation of the compensation current are decided according to the direction and the value of the unbalanced flux density. Dynamic eccentricity (DE) will produce new frequencies and spatial orders of the radial electromagnetic force, and the static eccentricity (SE) only produces the new spatial orders. The results obtained by the finite element model prove that this method can effectively reduce the UMF without sacrificing the output torque performance.