Determining degrees of freedom for eccentricity fault in SRM based on nonlinear static torque function

Abstract

PurposeThe purpose of this paper is to determine the degrees of freedom (DOF) for eccentricity fault in switched reluctance motor (SRM) based on nonlinear static torque function to minimize torque ripple for maximum performance in motoring operation.Design/methodology/approachAn algorithm based on nonlinear torque function versus rotor position and percent of rotor eccentricity for the SRM operation is introduced. This algorithm enables accurate determination of different modes of motor operations namely, healthy and faulty conditions. In this approach, SRM is first analyzed by a 3D finite element method for estimation of nonlinear torque function and then the function is approximated by least square, cubic spline and piecewise cubic Hermitian methods. The minimization is performed by random search method and genetic algorithm.FindingsA new procedure for computing the DOF of eccentricity in SRM based on nonlinear torque function is proposed and analyzed. It computes the legal intervals for the radial airgap length as well as the regions of the motor operation under different conditions. The functionability and the feasibility of this algorithm is illustrated by employing it on a three‐phase 6/4 SRM.Practical implicationsThe proposed method and its results can improve the motor control while the implementation is simple and practical. The proposed method can be used for other motors as well.Originality/valueThe boundary of motor operation under fault must be calculated to attain smooth control on motor to achieve high performance expected from the machine. To the best knowledge of the authors, this is the first time such a study has been conducted on SRM.