Question 1

If load (or torque) angle of a 4-pole synchronous motor is 6° electrical, its value in mechanical degrees is
A)2
B)3
C)4
D)6

Accepted Answer

The load (or torque) angle in mechanical degrees is half the electrical degrees for a 4-pole motor. Since the electrical angle is 6°, the mechanical angle is 6°/2 = 3°.

Question 2

For V-curves for a synchronous motor the graph is drawn between
A)field current and armature current
B)terminal voltage and load factor
C)power factor and field current
D)armature current and power factor

Accepted Answer

V-curves for a synchronous motor are plotted between field current and armature current, showing how the armature current varies with changes in field current at constant load.

Question 3

The back e.m.f. of a synchronous motor depends on
A)speed
B)load
C)load angle
D)all of the above

Accepted Answer

The answer of The back e.m.f. of a synchronous motor...

Question 4

A synchronous motor can operate at
A)lagging power factor only
B)leading power factor only
C)unity power factor only
D)lagging, leading and unity power factors

Accepted Answer

A synchronous motor's power factor can be adjusted to operate at lagging, leading, or unity power factor by varying its field excitation. This flexibility makes it useful for power factor correction in electrical systems.

Question 5

In a synchronous motor which loss varies with load ?
A)Windage loss
B)Bearing friction loss
C)Copper loss
D)Core loss

Accepted Answer

Copper loss varies with load because it is dependent on the current flowing through the motor's windings, which changes with the load.

Quiz 1: Synchronous Motors: Part A

If load (or torque) angle of a 4-pole synchronous motor is 6° electrical, its value in mechanical degrees is

For V-curves for a synchronous motor the graph is drawn between

The back e.m.f. of a synchronous motor depends on

A synchronous motor can operate at

In a synchronous motor which loss varies with load ?