Question

A dc machine, having a symmetrical closed-circuit armature winding and a sinusoidal air-gap flux-density distribution, will have a sinusoidal voltage induced in the individual coils. The resultant brush-to-brush voltage will have a waveform
1. Sinusoidal with the negative-half reversed
2. Unidirectional and constant without any ripples
3. Unidirectional and constant with ripples superimposed
4. Sinusoidal positive-half and zero negative-half, in each cycle

Answer 1

Correct Answer - Option 3 : Unidirectional and constant with ripples superimposed

Brush to Brush voltage is resultant of the voltage induced in all coils which are sinusoidal, and this induced voltage is collected through brushes that are connected to the commutator.

DC machine with symmetrical closed-circuit armature winding and sinusoidal air gap flux and a sinusoidal voltage induced in the coil has a resultant brush to brush voltage unidirectional and constant with ripples Superimposed waveform.