REDUCTION OF COGGING FORCE IN SLOTLESS LINEAR PERMANENT-MAGNET MOTORS

There are two potential causes of cogging force in linear permanent ma gnet motors, resulting from the slotting and the finite length of the iron-cored armature. The paper is concerned with slotless motors, for which a. technique is described for minimising the cogging force which is produced when the armature has a mild steel sleeve (yoke). By anal ysing the cogging-force waveform developed at one end of the sleeve an d optimising its axial length so that an opposing cogging-force wavefo rm is developed at the other end, it is possible to obtain nearly zero resultant force. The technique has been validated on a prototype moto r and found to be effective and simple to implement.