End magnet optimisation for the reduction of the thrust ripple of linear switched-flux machines

Abstract

Thanks to the usage and the placement of permanent magnets, linear switched flux machines exhibit a good performance even at a moderate cost. However, these machines are affected by high detent force and on load thrust force ripples. The placement of additional magnets in the ends of the machine is one of the possible solutions to deal with the thrust ripples. However, depending on the magnet width sizing approach, this solution may increase the value of the peak to peak detent force. In this paper, two new end magnet optimisation approaches are presented and compared to the conventional approach. The results show that both the detent force and the thrust ripple can be lowered with either of the new approaches, while lowering the volume of the end PMs in 66.49 % and 54.02 %.