1. In a single phase induction regulator, the voltage boost is maximum when armature mmf and rotor mmf make an angle of ____________
a) zero degrees
b) 45 degrees
c) 90 degrees
d) 180 degrees
Explanation: To obtain a maximum of the voltage in induction regulator, the stator mmf and rotor mmf should be stationary and aligned to each other.
2. An alternator is to be used for generation purpose in an aircraft. The most suited operating frequency of the alternator should be ____________
a) of 400 Hz to remove extra bulk
b) of 400 Hz to reduce losses
c) of 50 Hz to remove extra bulk
d) none of the mentioned
Explanation: The components to be used in aircrafts are made to operate at very high frequencies so that the size of the components to be used is reduced.
3. A 3-phase synchronous alternator is connected to the infinite bus is over excited, that corresponds to ______________
a) capacitor
b) inductor
c) variable inductor
d) any of the mentioned
Explanation: As the machine is over excited, it will act as source of reactive power and it is positive.
Q=V (Ecos (delta)-V)/X.
4. What is Commutator?
a) rotating segment to which brushes are attached
b) stationary segment to which rotating brushes are attached
c) rotating segment to which rotating brush segment is attached
d) any of the mentioned
Explanation: Commutator is a rotating segment to which brushes are attached.
5. Commutator action is analogous to _________ in analog electronics.
a) full wave rectifier
b) half wave rectifier
c) comparator
d) amplifier
Explanation: Commutator converts the alternating voltage induced at the armature to the unidirectional voltage at the slip rings.
6. What is Inductive kick?
a) reactance voltage in commutator segments
b) reactance voltage in shorted commutator segments
c) impulsive voltage in commutator segments
d) none of the mentioned
Explanation: Inductive kick is the name given to the reactance voltage which occurs at the commutation taking place in the commutator.It occurs due to the high circulating current during the commutation.
7. Inductive kick causes ________
a) sparking at the brushes of the machine
b) similar problems when neutral phase shift takes place in the armature
c) large current to flow in the equalizer rings
d) none of the mentioned
Explanation: Inductive kick is the name given to the reactance voltage which occurs at the commutation taking place in the commutator.It occurs due to the high circulating current during the commutation.
8. Operation of a dc machine will ________
a) not be affected by commutating poles
b) be affected by commutating poles
c) be affected significantly upto 30% spread of commutating poles
d) none of the mentioned
Explanation: Commutating poles are placed under the armature poles and it compensates only poles under these regions.
9. A 200 V dc machine working at rated speed. Voltage across the commutating terminals should ideally be ________
a) zero
b) 2 V
c) 1 V
d) 200 V
Explanation:The commutating poles undergoing commutation should have zero voltage across it so that there is no reactive voltage induced.
So it will not cause large circulating current in the winding.
10. For a four pole, 16 slot armature with two coil-side/slot having lap connected progressive winding has single turn coils. Then number of commutator segment is?
a) 16
b) 32
c) 4
d) 8
Explanation: Commmutator segment is equal to number of coil slots.