Single Phase Induction Motor MCQ

101. A universal motor runs at

(a) higher speed with dc supply and with less sparking.
(b) higher speed with ac supply and with less sparking.
(c) same speed with both ac and dc supplies.
(d) higher speed with ac supply but with increased sparking at the brushes.

102. Speed of the universal motor is

(a) dependent on frequency of supply.
(b) proportional to frequency of supply.
(c) independent of frequency of supply.
(d) none of the above.

103. Direction of rotation of a universal motor can be reversed by

(a) interchanging the brush leads.
(b) interchanging the supply terminals.
(c) either (a) or (b).
(d) none of these.

104. The speed of a universal motor is usually reduced by using

(a) V-belts.
(b) gearing.
(c) chains.
(d) brakes.

105. The speed of a universal motor can be controlled by

(a) introducing a variable resistance in series with the motor.
(b) tapping the field at various points.
(c) centrifugal mechanism.
(d) all of the above steps.

106. In a universal motor the most common cause(s) of brush sparking is/are

(a) open armature winding.
(b) shorted armature winding.
(c) shorted field winding.
(d) high commutator mica.
(e) all of the above.

107. Under no load operating condition, the speed of a universal motor is limited by

(a) windage and friction.
(b) armature reaction
(c) armature weight.
(d) supply frequency.

108. The armature reaction in a large sized universal motor is neutralized by

(a) shifting the brushes.
(b) connecting a compensating winding in series with the armature.
(c) increasing the number of armature coils.
(d) using low resistance brush.

109. In case of a high speed universal motor ………. needs maximum attention.

(a) air gap
(b) end play
(c) balancing of rotor
(d) insulation of rotor

110. In universal motors, normally the ratio of width of brushes to the width of commutator segments is

(a) 2 : 1
(b) 1 : 1
(c) 1 : 2
(d) 4 : 1

112. Repulsion motor

(a) receives its armature current by induction.
(b) is similar to a series motor except that rotor and stator windings are inductively coupled.
(c) can be directly switched on to supply line.
(d) has high starting torque and high speed on no load.
(e) all of the above.

113. A repulsion motor is equipped with

(a) slip rings.
(b) centrifugal switch.
(c) commutators and brushes.
(d) all of the above.

 

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