Analysis of two-part rotor, axial flux permanent magnet machines

This paper presents a study of the effects obtained when a portion of permanent magnet material is replaced by a soft magnetic composite piece over the rotor poles of an axial flux machine. This technical solution can be adopted to increase the machine inductance in order to limit short circuit currents or to increase the motor saliency and implement sensorless control schemes based on high frequency signal injection. Some design rules for the design of the soft magnetic poles have been derived in order to obtain the desired inductance and/or saliency. The analysis has been validated with finite element analisys and numerical simulations using Matlab/Simulink environment. Some preliminary experimental results have also been reported. © 2011 IEEE.