Explanation: The effect of short pitched coil is to reduce the generated EMF, and it improves waveform of EMF generated per phase, and as the windings are placed closed to each other, copper will be saved. 18. The DC machines are designed with flat topped flux density waves because
A. average value of brush voltage is more for a flat topped B-wave
B. average value of brush voltage is less for a flat topped B-wave
C. losses for flat topped B-wave are less
D. none of the mentioned
Answer:A
Explanation: The effect of short pitched coil is to reduce the generated EMF, and it improves waveform of EMF generated per phase, and as the windings are placed closed to each other, copper will be saved. 18. The DC machines are designed with flat topped flux density waves because
A. average value of brush voltage is more for a flat topped B-wave B. average value of brush voltage is less for a flat topped B-wave C. losses for flat topped B-wave are less D. none of the mentioned
Explanation: For the same value of peak flux density Bp, it is easy to see that average value of brush voltage could be more for a flat topped B-wave than for a sinusoidal flux density wave.