MCQ on single phase motor 120-140

120. 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

121. 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 immediately connect it to supply

122. 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✔

123. 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

124. A shaded pole motor does not possess
(a) centrifugal switch
(b) capacitor
(c) commutator
(d) all of the above✔

125. In a A.C. series motor armature coils are usually connected to commutator
(a) through resistance✔
(b) through reactances
(c) through capacitors
(d) solidly

126. Which of the following statements regarding a reluctance motor is incorrect ?
(a) It cannot be reversed, ordinarily✔
(b) It requires no D.C. field excitation for its operation
(c) It is nothing else but a single-phase, salient pole synchronous-induction motor
(d) Its squirrel cage-rotor is of unsym-metrical magnetic construction in order to vary reluctance path between stator and rotor

127. A universal motor is one which
(a) can be operated either on D.C. or A.C.✔ supply at approximately the same speed and output
(b) can be marketed internationally
(c) runs at dangerously high speed on no-load

128. A repulsion motor is equipped with
(a) slip rings
(b) commutator✔
(c) both (a) and (b)
(d) none of the above

129. The capacitors used in single-phase capacitor motors have no
(a) voltage rating
(b) dielectric medium
(c) polarity marking✔
(d) definite value

130. If a D.C. series motor is operated on A.C. supply, it will
(a) spark excessively
(b) have poor efficiency
(c) have poor power factor
(d) all of the above✔

131. After the starting winding of a single phase induction motor is disconnected from supply, it continues to run only on
(a) running winding✔
(b) rotor winding
(c) field winding
(d) compensating winding

132. Which of the following statements regarding repulsion-start induction motor is incorrect ?
(a) It requires more maintenance of commutator and other mechanical devices
(b) It makes quite a bit of noise on starting
(c) In fractional horse power motors, it has replaced the capacitor motors✔
(d) It is not easily reversed

133. A.C. series motor as compared to D.C. series motor has
(a) smaller brush width
(b) less number of field turns
(c) more number of armature turns
(d) less air gap
(e) all of the above✔

134. Locked rotor current of a shaded pole motor is
(a) equal to full load current
(b) less than full load current
(c) slightly more than full load curren✔
(d) several times the full load current

135. Speed control of a universal motor is achieved by
(a) varying field flux with tapped field windings
(b) connecting rheostat in series
(c) applying variable voltage by means of silicon controlled rectifier
(d) applying variable voltage by means of variable auto-transformer
(e) all of the above methods✔

136. Hysteresis motor is particularly useful for high-quality record players and tape-recorders because
(a) it revolves synchronously
(b) it is not subject to any magnetic or mechanical vibrations
(c) it can be easily manufactured in extremely small sizes of up to 1 W output
(d) it develops hysteresis torque which is extremely steady both in amplitude and phase✔

137. Which of the following statements regarding hysteresis motor is in incorrect ?
(a) It is extremely sensitive to fluctuations in supply voltage✔
(b) Its high starting torque is due to its high rotor hysteresis loss
(c) It is extremely quiet in operation
(d) It accelerates from rest to full-speed almost instantaneously

138. Which of the following statements regarding single-phase induction motoris correct ?
(a) It requires only one winding
(b) It can rotate in one direction only
(c) It is self-starting
(d) It is not self-starting✔

139. The starting winding of a single-phase motor is placed in
(a) armature
(b) field
(c) rotor
(d) stator✔

140. The speed of a universal motor is usually reduced by using
(a) gearing✔
(b) belts
(c) brakes
(d) chains