Single phase induction motors
smaller brush width
less number of field turns
series motor as compared to
less air gap E. all of the above
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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
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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
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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
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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
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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
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77. Burning out of winding is due to
short circuited capacitor
capacitor value hiving changed
open circuiting of capacitor
none of the above
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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
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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
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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
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