Optimum design for eddy current reduction in permanent magnet to prevent irreversible demagnetization

Irreversible demagnetization which occurs in permanent magnet (PM) due to high temperature is main issue in design of traction motor for hybrid electric vehicle. In order to prevent irreversible demagnetization, eddy current loss in PM should be minimized. This paper deals with the optimum design to reduce eddy current loss in PM. Indirect method is used to instead of direct calculation of eddy current loss which uses 3D transient magnetic field analysis. To estimate eddy current loss indirectly, magneto-static field analysis is employed and the obtained flux density variation in PM is used based on the fact that eddy current loss is proportional to square of flux density and frequency. Response surface methodology coupled with design of experiment is used for optimum design in the objective function of peak-peak value and total harmonic distortion of flux density variation in PM Motor design process ensuring minimum variation of flux density in PM is presented and a transient analysis is used for verification of optimum design.