A qualitative investigation of flux pulsations in a DC machine with input current ripple

Thyristor control of DC machines has presented machines designers and users with problems of assessing the effects of the ripple introduced by the switching action of the devices. Distortions of a DC machine flux pattern when it has input current ripple are shown to consist of: pulsation of the main flux due to armature reaction; pulsation of interpole flux which influence current reversal in the machine; and deviation of the armature MMF from the steady triangular waveshape to a pulsating triangular form whose limits depend on the amount of ripple fed to the motor. It is noted that the oscillograms of gap flux contain considerable slot ripple which mask the ripple effects of interest