Question 1

Which of the following motors is used for unity power factor ?
A)Hysteresis motor
B)Schrage motor
C)Universal motor
D)Reluctance motor

Accepted Answer

Schrage motors are designed to operate at a unity power factor by adjusting the rotor winding connections and using a commutator.

Question 2

The motor used for the compressors is
A)d.c. series motor
B)shaded pole motor
C)capacitor-start capacitor-run motor
D)reluctance motor

Accepted Answer

Capacitor-start capacitor-run motors are commonly used for compressors because they provide high starting torque and efficient running performance, which are essential for the start-up and continuous operation of compressor units.

Question 3

Which of the following motors is used in a situation where load increases with speed ?
A)Induction motor
B)Three-phase series motor
C)Schrage motor
D)Hysteresis motor

Accepted Answer

Three-phase series motors are suitable for applications where the load increases with speed, as they have characteristics that allow them to handle such conditions effectively.

Question 4

In repulsion motor, zero torque is developed when
A)brush axis is 45° electrical to field axis
B)brush axis coincides with the field axis
C)brush axis is 90° electrical to field axis
D)both (b) and (c)

Accepted Answer

In a repulsion motor, zero torque is developed when the brush axis either coincides with the field axis or is 90° electrical to the field axis. This is because, in both positions, the interaction between the magnetic field and the current in the rotor conductors (which is induced due to the brushes' position) does not produce a torque.

Question 5

Centrifugal switch disconnects the auxiliary winding of the motor at about ____ percent of synchronous speed
A)30 to 40
B)70 to 80
C)80 to 90
D)100

Accepted Answer

The answer of Centrifugal switch disconnects the auxiliary winding of...

Question 6

Starting winding of a single phase motor of a refrigerator is disconnected from the circuit by means of a
A)magnetic relay
B)thermal relay
C)centrifugal switch
D)none of the above

Accepted Answer

The answer of Starting winding of a single phase motor...

Question 7

If a single phase induction motor runs slower than normal, the most likely defect is
A)worn bearings
B)short-circuit in the winding
C)open-circuit in the winding
D)none of the above

Accepted Answer

Worn bearings can cause friction, leading to the motor running slower than normal.

Question 8

Which of the following motors is used in tape-recorders ?
A)Hysteresis motor
B)Reluctance motor
C)Capacitor-run motor
D)Universal motor

Accepted Answer

Hysteresis motors are commonly used in tape recorders due to their smooth and silent operation, which is essential for the quality recording and playback of audio. They provide precise speed control and low noise, making them ideal for this application.

Question 9

Which of the following statements regarding two value capacitor motor is incorrect ?
A)It is a reversing motor
B)It is preferred to permanent-split single-value capacitor motor where frequent reversals are required
C)It has low starting as well as rush¬ing currents
D)It has high starting torque

Accepted Answer

The answer of Which of the following statements regarding two...

Question 10

Two-value capacitor motor finds increased application as compressor motor in small home air-conditioners because
A)it is comparatively cheaper
B)it has almost non-destructible capacitor
C)it has low starting as well as running currents at relatively high power factor
D)it is quiet in operation

Accepted Answer

Two-value capacitor motors are preferred for compressor motors in small home air-conditioners because they have low starting and running currents while maintaining a relatively high power factor, which is efficient for such applications.

Question 11

If the centrifugal switch of a two-value capacitor motor using two capacitors fails to open then
A)motor will not come upto speed
B)motor will not carry the load
C)current drawn by the motor will be excessively high
D)electrolytic capacitor will, in all probability, suffer break down

Accepted Answer

The answer of If the centrifugal switch of a two-value...

Question 12

In a universal motor, the most common cause of brush sparking is
A)open armature winding
B)shorted armature winding
C)shorted field winding"
D)all of the above

Accepted Answer

In a universal motor, brush sparking can be caused by various issues including open armature winding, shorted armature winding, and shorted field winding. Each of these conditions can disrupt the normal current flow or create imbalances in the magnetic fields, leading to sparking at the brushes.

Question 13

If starting winding of a single-phase induction motor is left in the circuit, it will
A)run faster
B)spark at light loads
C)draw excessive current and overheat
D)run slower

Accepted Answer

Leaving the starting winding in the circuit of a single-phase induction motor causes it to draw excessive current, leading to overheating, because the starting winding is designed for short-term use to start the motor and not for continuous operation.

Question 14

Most of the fractional horsepower motors have either
A)hard and annealed bearings
B)ball or roller bearings
C)soft and porous bearings
D)plain or sleeve bearings

Accepted Answer

Most fractional horsepower motors use plain or sleeve bearings due to their simplicity, cost-effectiveness, and sufficient performance for the lower loads and speeds these motors typically encounter.

Question 15

Which of the following statements regarding reluctance-start motor is incorrect ?
A)It is similar to reluctance motor
B)It is basically an induction motor and not a synchronous one
C)So far as its basic working principle is concerned, it is similar to shaded pole motor
D)the air-gap between rotor and salient poles is non- uniform

Accepted Answer

The reluctance-start motor is not just similar to a reluctance motor; it is a type of induction motor designed to start like a reluctance motor but operates as an induction motor once it reaches near synchronous speed. This distinction is important because while it utilizes the principle of reluctance for starting, its operation and design are more aligned with induction motors, making it fundamentally different from a pure reluctance motor in overall functionality.

Question 16

To reverse the direction of rotation of acapacitor start motor while it is running we should
A)disconnect motor from the supply till it stops then reconnect it to supply with reversed connection of main or auxiliary winding
B)disconnect motor from supply and immediately reconnect it to supply with reversed connections of the main winding
C)reverse the direction of connection of the auxiliary winding and after motor comes to rest then connect auxiliary winding to the supply
D)reverse the direction of connections of the auxiliary winding and im-mediately connect it to supply

Accepted Answer

The answer of To reverse the direction of rotation of...

Question 17

In case of a reluctance motor, when the load is increased so that it cannot maintain synchronous speed the motor will
A)become unstable
B)draw excessive armature current and may burn out
C)fall out of synchronism and come to stand still
D)run as induction motor

Accepted Answer

When a reluctance motor cannot maintain synchronous speed due to increased load, it falls out of synchronism but continues to run as an induction motor. This is because the rotor design typically allows for induction motor operation under such conditions.

Question 18

Which of the following motors has two separate windings on the motor ?
A)Repulsion motor
B)Repulsion induction motor
C)Repulsion start induction run motor
D)None of the above

Accepted Answer

The repulsion induction motor has two separate windings: one for the repulsion start and another for the induction run.

Question 19

A shaded pole motor does not possess
A)centrifugal switch
B)capacitor
C)commutator
D)all of the above

Accepted Answer

A shaded pole motor does not have a centrifugal switch, capacitor, or commutator. These components are associated with other types of motors, such as split-phase motors, capacitor-start motors, and DC motors, respectively. Shaded pole motors are simple in construction, using only a shaded pole for starting.

Question 20

In a A.C. series motor armature coils are usually connected to commutator
A)through resistance
B)through reactances
C)through capacitors
D)solidly

Accepted Answer

The answer of In a A.C. series motor armature coils...

Quiz 4: Motor Types and Applications

Which of the following motors is used for unity power factor ?

The motor used for the compressors is

Which of the following motors is used in a situation where load increases with speed ?

In repulsion motor, zero torque is developed when

Centrifugal switch disconnects the auxiliary winding of the motor at about ____ percent of synchronous speed

Starting winding of a single phase motor of a refrigerator is disconnected from the circuit by means of a

If a single phase induction motor runs slower than normal, the most likely defect is

Which of the following motors is used in tape-recorders ?

Which of the following statements regarding two value capacitor motor is incorrect ?

Two-value capacitor motor finds increased application as compressor motor in small home air-conditioners because

If the centrifugal switch of a two-value capacitor motor using two capacitors fails to open then

In a universal motor, the most common cause of brush sparking is

If starting winding of a single-phase induction motor is left in the circuit, it will

Most of the fractional horsepower motors have either

Which of the following statements regarding reluctance-start motor is incorrect ?

To reverse the direction of rotation of acapacitor start motor while it is running we should

In case of a reluctance motor, when the load is increased so that it cannot maintain synchronous speed the motor will

Which of the following motors has two separate windings on the motor ?

A shaded pole motor does not possess

In a A.C. series motor armature coils are usually connected to commutator