MCQs on Electrical Machines

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01․ In synchronous motor, the damper winding is generally used to
reduce the eddy currents.
reduce noise level only.
provide starting torque only.
prevent hunting and provide the starting torque.

Under construction.
02․ In a synchronous motor, damper windings are provided on
rotor shaft.
stator frame.
pole faces.
none of the above.

Under construction.
03․ Hunting in a synchronous cannot be due to
windage friction.
variable frequency.
variable supply voltage.
variable load.

Under construction.
04․ The torque angle, in a synchronous motor, is the angle between
the rotating stator flux and rotor flux.
magnetizing electric current and back emf.
the supply voltage and the back emf.
none of the above.

Under construction.
05․ A synchronous motor will deliver maximum power when
load angle is equal to internal angle θ.
load angle is 45°.
load angle is 0°.
input power factor is unity.

Under construction.
06․ In a synchronous motor hunting can be reduced to minimum possible by
using a flywheel.
designing the motor for adequate synchronizing power.
providing damper winding in the rotor pole faces.
any of above methods.

Under construction.
07․ The damper windings also called the squirrel cage windings or damper grids
consists of short-circuited copper bars embedded in the field pole faces.
are provided in a synchronous motor to make it self starting.
are provided on the stator for improving power factor.
both (A) and (B).

Under construction.
08․ When a synchronous motor is running at synchronous speed, the damper winding produces
no torque.
damping torque.
eddy current torque.
torque aiding the developed torque.

Under construction.
09․ During hunting of a synchronous motor
field excitation increases.
damper bar develops torque.
negative phase sequence currents are generated.
harmonic are developed in the armature circuit.

Under construction.
10․ In a synchronous motor when the rotor speed exceeds the synchronous speed during hunting
the damper bars develop synchronous motor torque.
the damper bars develop induction generator torque.
the damper bars develop induction motor torque.
negative sequence currents are generated.

Under construction.
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