An alternative energisation mode for the 4-phase, variable-reluctance stepping motor

An energisation sequence is proposed which enables satisfactory static torque/angular position characteristics to be obtained with the 4-phase, single-stator, variable-reluctance (VR) stepping motor when operating in the halfstep mode. It is shown to be advantageous to utilise 3-phase excitation, where a substantial increase in holding torque is obtained when the distribution of magnetomotive force (MMF) among the phases is optimally proportioned, subject to the thermal constraint on the stator-winding losses. Experimental results are presented, and a simple analysis of the magnetic arrangement is developed.