Delta-star pam

Pole changing by pole amplitude modulation (PAM), using a delta-star winding configuration, is described. Speed changing is achieved by simple parallel/series switching of the delta-star winding, using precisely the same type of switch and the same number of motor leads as any other PAM winding. The new winding is shown to have properties superior to conventional windings, particularly in relation to MMF harmonic content. It needs two sets of coils and different numbers of turns and wire sizes, one for each of the delta and star components, and so is likely to find application in small motors only. Examples of windings for 2/10 poles and 10/14 poles are included.