Armature reaction field and inductances of tubular modular permanent magnet machines

Abstract

The paper describes an analytical technique which has been developed to predict the armature reaction field of tubular modular permanent magnet (PM) machines in which the fundamental of the stator magnetomotive force (mmf) has fewer poles than that of the permanent magnet armature, the thrust force being developed by the interaction between a higher-order mmf harmonic with the permanent magnet field. The analytical solution also allows the prediction of the self- and mutual-winding inductances of a tubular modular machine in closed forms and facilitates dynamic modeling, as well as the evaluation of any partial irreversible demagnetization of the magnets which might occur under various operating conditions. The utility and accuracy of the developed technique are demonstrated by extensive finite element analyses and measurements on a nine-slot/ten-pole tubular modular PM machine.