Calculation of stray losses due to distorted flux density waveforms of DC motors operated by chopper control circuits

A computer-aided modeling approach to the prediction of the armature current waveforms of chopper-operated permanent magnet DC motors is presented. The model is used to separate the effect of AC ripple in the current on the ohmic losses from the ohmic losses due to the DC component. Thus the effects of the chopper on stray-load losses can be determined. This approach was further used to compute the effect of choppers on the magnetic armature core losses in such motors, and hence on stray core losses. Whenever feasible, supporting experimental work was performed to obtain data to verify some key computed parameters and performance results. Conclusions are drawn regarding the effects of chopper operation on such permanent magnet DC motors