## Electrical Machines The shaft torque of a dc motor is less than the electromagnetic torque because of

ohmic losses.
eddy current losses.
mechanical losses.
hysteresis losses.

## Electrical Machines A 3 - φ induction motor can also be referred to as a

shunt motor.
transformer.
repulsion motor.
asynchronous motor.

## Electrical Machines Consider the following statements about commutating poles which are fitted on most large dc Shunt motors: 1. The commutating poles are placed in the geometric neutral plane and their number is usually Equal to the number of main poles 2. The winding on the commutating poles is connected in series with the shunt-field winding on the main poles 3. The polarity of the commutating pole must be that of the next pole further ahead 4. The commutating poles neutralize the reactance voltage produced in the coil undergoing Commutation. Of these statements,

2, 3 and 4 are correct
1, 2 and 4 are correct
1, 2 and 3 are correct
1 and 4 are correct

## Electrical Machines Which of following DC generator will be in a position to build up without any residual magnetism in the field?

Compound.
Series.
Shunt.
Separately excited.

## Electrical Machines In a DC generator the emf generated by the armature is maximum when

induced voltage is high.
rate of change of flux is maximum.
shaft rotation is high.
rate of change of flux is minimum.

## Electrical Machines The direction of rotation of conductor of a DC motor can be determined by

Fleming's right hand rule.
Lenz's law.
Fleming's left hand rule.
Ampere law.