Explore topic-wise MCQs in Electrical Machines.

This section includes 27 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Machines knowledge and support exam preparation. Choose a topic below to get started.

1.

(I)For constant power of an isolated alternator, V-curves can be obtained. (II)For constant power of an alternator connected to IBB, V-curves can be obtained.

A. I is true, II is false
B. Both the statements are true
C. I is false while II is true
D. Both are false
Answer» D. Both are false
Discussion
2.

(I) Speed of an isolated alternator can be altered. (II) Speed of an alternator connected to IBB can be also altered.

A. I is true, II is false
B. Both the statements are true
C. I is false while II is true
D. Both are false
Answer» B. Both the statements are true
Discussion
3.

For a synchronous motor, mark the appropriate.

A. A-Inductor, B-Capacitor
B. A-Capacitor, B-Resistor
C. A-Inductor, B-Inductor
D. A-Capacitor, b-Inductor
Answer» B. A-Capacitor, B-Resistor
Discussion
4.

Synchronous compensators are ________

A. over excited synchronous motor with no mechanical load
B. over excited synchronous motor with mechanical load
C. under excited synchronous motor with no mechanical load
D. normally excited synchronous motor with no mechanical load
Answer» B. over excited synchronous motor with mechanical load
Discussion
5.

For a power system having induction motor loads, an overexcited synchronous motor is also attached. The induction motor will now operate at ________

A. lagging
B. leading
C. reduced power factor
D. increased power factor
Answer» B. leading
Discussion
6.

For a power system having induction motor loads, an overexcited synchronous motor is also attached. Then the over all power factor?

A. improves
B. degrades
C. becomes upf
D. remains same
Answer» B. degrades
Discussion
7.

The inverted V plots is plotted between ________

A. power factor vs field current for constant shaft load
B. field current vs power factor for variable shaft load
C. armature current vs field current
D. terminal voltage vs power factor
Answer» B. field current vs power factor for variable shaft load
Discussion
8.

The armature current is _______ at UPF than motor at lagging power factor.

A. minimum
B. maximum
C. zero
D. none of the mentioned
Answer» B. maximum
Discussion
9.

When the excitation voltage is increased from 1 to 1.3 pu of a 3-phase synchronous motor. Then load angle for the constant power operation ________

A. must be decreased
B. can also be increased
C. increased
D. decreased
Answer» B. can also be increased
Discussion
10.

When a constant power output is desired to maintain ________

A. Ef*sinδ and Ia*cosθ are to be maintained constant
B. Ef*sinδ is be maintained constant
C. Ia*cosθ is to be maintained constant
D. Ef*sinδ and Ia*sinθ are to be maintained constant
Answer» B. Ef*sinδ is be maintained constant
Discussion
11.

The excess flux in synchronous motor is neutralized by ________

A. armature winding by drawing demagnetizing component of the current from ac supply
B. armature winding by drawing magnetizing component of the current from ac supply
C. field winding by drawing demagnetizing component of the current from dc supply
D. field winding by drawing magnetizing component of the current from dc supply
Answer» B. armature winding by drawing magnetizing component of the current from ac supply
Discussion
12.

FOR_A_POWER_SYSTEM_HAVING_INDUCTION_MOTOR_LOADS,_AN_OVEREXCITED_SYNCHRONOUS_MOTOR_IS_ALSO_ATTACHED._THEN_THE_OVER_ALL_POWER_FACTOR?$

A. improves
B. degrades
C. becomes upf
D. remains same
Answer» B. degrades
Discussion
13.

Synchronous compensators are$

A. over excited synchronous motor with no mechanical load
B. over excited synchronous motor with mechanical load
C. under excited synchronous motor with no mechanical load
D. normally excited synchronous motor with no mechanical load
Answer» B. over excited synchronous motor with mechanical load
Discussion
14.

For a power system having induction motor loads, an overexcited synchronous motor is also attached. The induction motor will now operate at$

A. lagging
B. leading
C. reduced power factor
D. increased power factor
Answer» B. leading
Discussion
15.

The active power delivered by an alternator will _______ when the prime mover input is increased for the alternator connected to infinite bus bar.

A. increases
B. decreases
C. remains constant
D. no relation exists between the power and prime mover droop characteristic
Answer» B. decreases
Discussion
16.

The operating frequency and voltage of an isolated alternator ________ if the prime mover input to motor is increased.

A. increases
B. decreases
C. remains constant
D. no relation exists between the power and frequency
Answer» B. decreases
Discussion
17.

(I)For constant power of an isolated alternator, V-curves can be obtained.

A. For constant power of an alternator connected to IBB, V-curves can be obtained
B. I is true, II is false
C. Both the statements are true
D. I is false while II is true
Answer» D. I is false while II is true
Discussion
18.

(I) Speed of an isolated alternator can be altered.

A. Speed of an alternator connected to IBB can be also altered.
B. I is true, II is false
C. Both the statements are true
D. I is false while II is true
Answer» B. I is true, II is false
Discussion
19.

The inverted V plots is plotted betwee?

A. power factor vs field current for constant shaft load
B. field current vs power factor for variable shaft load
C. armature current vs field current
D. terminal voltage vs power factor
Answer» B. field current vs power factor for variable shaft load
Discussion
20.

The armature current is _______ at UPF than motor at lagging power factor?

A. minimum
B. maximum
C. zero
D. none of the mentioned
Answer» B. maximum
Discussion
21.

The armature current is ________ at UPF when compared to leading power factor.

A. minimum
B. maximum
C. equal
D. none of the mentioned
Answer» B. maximum
Discussion
22.

When the excitation voltage is increased from 1 to 1.3 pu of a 3-phase synchronous motor. Then load angle for the constant power operation

A. must be decreased
B. can also be increased
C. increased
D. decreased
Answer» B. can also be increased
Discussion
23.

When a constant power output is desired to maintain

A. Ef*sinδ and Ia*cosθ are to be maintained constant
B. Ef*sinδ is be maintained constant
C. Ia*cosθ is to be maintained constant
D. Ef*sinδ and Ia*sinθ are to be maintained constant
Answer» B. Ef*sin‚âà√≠¬¨‚Ä¢ is be maintained constant
Discussion
24.

The V-curves of synchronous motor is plotted between ________

A. Ia Vs If with constant shaft load
B. If Vs Ia with constant shaft load
C. power factor vs If
D. power factor vs Ia
Answer» B. If Vs Ia with constant shaft load
Discussion
25.

The excess flux in synchronous motor is neutralized by

A. armature winding by drawing demagnetizing component of the current from ac supply
B. armature winding by drawing magnetizing component of the current from ac supply
C. field winding by drawing demagnetizing component of the current from dc supply
D. field winding by drawing magnetizing component of the current from dc supply
Answer» B. armature winding by drawing magnetizing component of the current from ac supply
Discussion
26.

A 3 phase synchronous motor is working at normal excitation, then the flux deficient in circuit is ________

A. given by armature winding mmf
B. given by field winding mmf
C. supplied to armature winding mmf
D. supplied to field winding mmf
Answer» B. given by field winding mmf
Discussion
27.

The magnetization current drawn from an AC supply a synchronous motor is used to _________

A. set up flux in magnetic circuit of device
B. compensate core losses
C. set up magnetizing armature reaction
D. all of the mentioned
Answer» B. compensate core losses
Discussion