Total loss optimization in varying pole pair radial magnetic bearing using theoretical and genetic algorithm approach

Abstract

A typical problem of radial magnetic bearing is chosen and bearing involving n-pole pairs, where n = 2,3,4,6,8, are designed. Various losses occurring in magnetic bearings such as copper loss, eddy current loss, hysteresis loss, windage loss are summarized as total loss and the methods of evaluating are discussed. Each individual loss and total loss in each case are computed for different rotor speeds. Total loss analysis was performed and the results are compared. It is found that there is a drastic decrease in the total loss from two pole pair to four pole pair. Later there is slow increase of total loss with number of pole pairs. On the whole, it is found the four pole pair to give the minimum total loss for all the speeds. Further a better analysis of total loss in four-pole pair radial magnetic bearing is performed using genetic algorithms. Objective function considered represents the total power loss, expressed as a function of seven design variables. It is found that the optimum total loss obtained by considering seven design parameters is much less than that of theoretical results. The genetic algorithm is showing the optimum losses nearly 50% of those theoretically predicted losses. On the whole, the total loss is found to increase with speed. Sensitivity analysis of various design parameters has been performed to see the effect on individual loss and changes in bearing performance parameters.