Harmonic analysis of permanent magnet DC motors operated by chopper control circuits

A computer-aided 2-D finite-element method is used, in conjunction with chopper-machine system analysis and experimental work for verification purposes, to predict the chopper current and voltage waveforms of a permanent-magnet DC motor operated by a chopper control circuit. The armature current waveforms at different chopping frequencies are analyzed numerically, and harmonic contents are computed. Armature core losses due to distorted waveforms of flux densities resulting from the chopped armature current are obtained and compared with the core losses of the motor when it is supplied from a pure DC source at the same operating conditions. These results and their implications are discussed