Objective Type Question or MCQ of Induction Motors page-16

151. Unbalanced supply voltage for an induction motor will cause

A) lower losses
B) less heating of rotor
C) negative sequence component in the rotating magnetic field
D) all of the above.

Ans : (C)

152. When the supply voltage for an induction motor is reduced by 10% which of the following will not decrease

B) Percentage slip
C) Starting current
D) All of the above.

Ans : (B)

153. In a three-phase slip ring induction motor high starting torque is achieved by

A) Increase supply voltage
B) Increase supply frequency
C) Connecting a capacitor across the motor terminals
D) Connecting a star-connected resistance across the slip ring terminals of the motor.

Ans : (D)

154. If the supply frequency for an induction motor is reduced by 5%, the synchronous speed will

A) increase by 10%
B) increase by 5%
C) decrease by 5%
D) decrease by 10%.

Ans : (B)

155. If the supply frequency for an induction motor is reduced by 5%, which of the following will also decrease ?

A) Temperature rise on full load
B) Starting current
C) Maximum running torque

Ans : (D)

156. When the supply voltage for an induction motor is reduced by 10%, the maximum running torque will nearly

A) increase by 20%
B) increase by 10%
C) decrease by 20%
D) decrease by 10%.

Ans : (C)

157. When the supply voltage for an induction motor is reduced, which of the following will increase ?

A) % slip
C) Maximum temperature rise on full load
D) All of the above.

Ans : (D)

158. For a three-phase induction motor, if the supply frequency is increased, which of the following will also increase ?

A) Synchronous speed
B) Temperature rise on full load
D) Starting torque.

Ans : (A)

159. The range of slip for induction motors is normally

A) 1% to 25%
B) 0 to 5%
C) 0.1% to 0.5%
D) 0 to 1%.

Ans : (B)

160. When the supply voltage for an induction motor is increased by 10%, the maximum running torque will increase by about

A) 5%
B) 10%
C) 20%
D) 40%.

Ans : (C)

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