## Electrical Machines DC motors are stopped by opening line switches and not by forcing the handle of the motor starter back to OFF position. This is due to occurance of

Heavy sparking at the first stud of starting resistance steps.
None of these.
Both of above.
Heavy sparking at brushes.

## Electrical Machines The synchronous speed of an induction motor will be increased by

increasing number of poles.
decreasing of frequency.
increasing of frequency.
speed can not be increased.

## Electrical Machines A bipolar dc machine with interpoles has a main-pole flux of ф per pole and an interpole flux of Фᵢ per pole. The yoke of the machine is devide into four quadrants by the main-pole axis and The commutation axis. The flux-distribution in the quadrants will be

½ ( ф + фᵢ ) in two adjacent quadrants and ½ ( ф - фᵢ ) in the remaining two quadrants
½ ( ф - фᵢ ) in all the four quadrants
½ ( ф + фᵢ ) in all the four quadrants
½ ( ф + фᵢ ) in two diametrically opposite quadrants and ½ ( ф - фᵢ ) in the remaining two Quadrants

## Electrical Machines Exciting current of an induction motor is

none of these.
equal as power transformer.
higher than power transformer.
lesser than power transformer.

None of these
AC and DC
AC
DC

## Electrical Machines Which of the following DC motors has almost constant speed over their full load range?

Shunt.
Compound (cummolative).
Series.
none of these.