Single phase induction motors Archives

71.

smaller brush width

less number of field turns

series motor as compared to

less air gap E. all of the above

Detailed Solution

72. A capacitor-start single phase induction motor is switched on to supply with its capa-citor replaced by an inductor of equivalent reactance value. It will

start and then stop

start and run slowly

start and run at rated speed

not start at all

Detailed SolutionA capacitor-start single phase induction motor is switched on to supply with its capa-citor replaced by an inductor of equivalent reactance value. It will

73. Hysteresis motor is particularly useful for high-quality record players and tape-recorders because

it revolves synchronously

it is not subject to any magnetic or mechanical vibrations

it can be easily manufactured in extremely small sizes of up to 1 W output

it develops hysteresis torque which is extremely steady both in amplitude and phase

Detailed SolutionHysteresis motor is particularly useful for high-quality record players and tape-recorders because

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

It is a reversing motor

It is preferred to permanent-split single-value capacitor motor where frequent reversals are required

It has low starting as well as rushing currents

It has high starting torque

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

75. After the starting winding of a single phase induction motor is disconnected from supply, it continues to run only on

running winding

rotor winding

field winding

compensating winding

Detailed SolutionAfter the starting winding of a single phase induction motor is disconnected from supply, it continues to run only on

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

Magnetic relay

Thermal relay

Centrifugal switch

None of the above

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

77. Burning out of winding is due to

short circuited capacitor

capacitor value hiving changed

open circuiting of capacitor

none of the above

Detailed SolutionBurning out of winding is due to

78. Which of the following single-phase motors has relatively poor starting torque ?

Universal motor

Repulsion motor

Capacitor motor

All single phase motors have zero starting torque

Detailed SolutionWhich of the following single-phase motors has relatively poor starting torque ?

79. The rotor of a hysteresis motor is made of

aluminium

cast iron

chrome steel

copper

Detailed SolutionThe rotor of a hysteresis motor is made of

80. If a particular application needs high speed and high starting torque, then which of the following motor will bepreferred ?

Universal motor

Shaded pole type motor

Capacitor start motor

Capacitor start and run motor

Detailed SolutionIf a particular application needs high speed and high starting torque, then which of the following motor will bepreferred ?

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