Practice Electrical Machines Multiple Choice Multiple Choice Questions with Answers Quiz-1

Q.1.

The coupling angle or load angle of a synchronous motor is defined as the space angle between __________

a) rotor and stator poles of opposite polarity
b) rotor and stator poles of same polarity
c) rotor and stator teeth
d) rotor and resultant magnetic field

Explanation

Q.2.

What is Synchronizing power?

a) i,ii
b) ii, iii
c) iii, i
d) i, ii, iii

Explanation

Q.3.

Large stiffness coefficient represents ____________

a) motor speed remains practically constant
b) large fluctuations due to mechanical load
c) motor speed is variable to changes
d) no such significance with speed

Explanation

Q.4.

An over excited synchronous machine is more stable than under excited.

a) True
b) False

Explanation

Q.5.

Consider the below remarks for an alternator.

a) (i) is True, (ii) is False
b) (i) is False, (ii) is True
c) (i) is True, (ii) is True
d) (i) is False, (ii) is False

Explanation

Q.6.

As load angle is increased, degree of stability __________

a) reduces
b) increases
c) remains same
d) no change in stability

Explanation

Q.7.

Synchronizing power is __________

a) transient in nature
b) steady state in nature
c) pulsating at small frequencies
d) constant for a machine

Explanation

Q.8.

Which of the following makes synchronizing power to come to play in the machine?

a) Disturbance in power mover
b) Disturbance in field current
c) Disturbance in load
d) All of the mentioned

Explanation

Q.9.

Which of the following is/are used in synchronous machines to maintain mechanical stability?

a) Damper winding
b) Interpole winding
c) Compensating winding
d) Equalizer rings

Explanation

Q.10.

For a 4-pole 3 phase,alternator has synchronizing power ofunits. Then the synchronizing power per mechanical degree is?

a) 300
b) 1200
c) 900
d) 600

Explanation

Q.11.

Electromagnetic torque is present in rotating machines when ____________

a) both stator and rotor windings carry current
b) rotor windings carry current
c) stator windings carry current
d) any of the mentioned

Explanation

Q.12.

The operation of a synchronous motor operating on constant excitation across infinite bus will not be stable if power angle δ?

a) exceeds internal angle θ
b) is less than θ
c) is more than θ/2
d) is less than θ/2

Explanation

Q.13.

In a synchronous motor the back emf peak set up in the stator depends on ___________

a) rotor excitation
b) supply voltage
c) rotor speed
d) load on the motor

Explanation

Q.14.

Variation in the dc excitation of a synchronous motor causes variation in ___________

a) armature current and power factor
b) power factor
c) armature current
d) speed

Explanation

Q.15.

Which motor can conveniently operate at lagging as well as leading power factor?

a) Synchronous motor
b) Slip ring induction motor
c) Squirrel cage induction motor
d) Stepper motor

Explanation

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