Choose the correct answer 1- In an induction motor, if the air gap is increased (A) Its speed will reduce (C) Its power factor will reduce (B) Its efficiency will improve (D) Its breakdown torque will reduce 2- In an induction motor, when the number of stator slots is equal to number of rotor slots (A) There may be a discontinuity in torque slip characteristics (B) A high starting torque will! (C) The maximum torque will be high (D) The machine may fail to sti available 3-The starting torque of an induction motor is maximum when (A) rotor resistance equals rotor reactance (C) rotor resistance is 1/2 the rotor reactance 4- Crawling is happened in three-phase induction (A) Low voltage (C) Bad mechanical design of the machine (B) rotor resistance is twice the rotor reactan (D) None of the above motor due to --- (B) Heavy loads connected to rotor (D) Harmonics 5- If the applied rated voltage per phase is reduced to one-half, then the starting torque of squir cage induction motor becomes ---------- (A) 4 times the initial value (C) 1/2 times the initial value (B)) 1/4 of the initial value (D) 2 times the initial value 6- The injected e.m.f. in the rotor of induction motor must have (A) zero frequency (C) the same phase as the rotor e.m.f. (B) the same frequency as the slip frequency (D) high value for the satisfactory speed control 7-In double cage induction motor the inner cage has (A) high resistance and high leakage reactance (C) low resistance and high leakage reactance 8- During plugging of an induction motor (A) phase sequence is reversed (C) one phase is open circuited (B) high resistance and low leakage reactar (D) low resistance and low leakage reactan (B) a dc source is connected to stator (D) power is fed back to mains 9- In a 3-phase induction machine, motoring, generating and braking operations take place in the range of slip "s" is (A) 1>s>0, 0>s>-2 and s>1 (C) s > 1, 0>s>-1 and 1>s>0 0>s>-1 (B) s>1, 1>s>-1 and (D) 0>s>−1, s>1 and 1>s> 0 10- When stator resistance starter is used, the factor by which stator voltage reduces is say x. If x<1, then due to stator resistance starter, the starting torque. (A) Increases by fraction x (C) Reduces by fraction x (B) Reduces by fraction x A 2 (D) Increases by fraction x A 2

Choose the correct answer 1- In an induction motor, if the air gap is increased (A) Its speed will reduce (C) Its power factor will reduce (B) Its efficiency will improve (D) Its breakdown torque will reduce 2- In an induction motor, when the number of stator slots is equal to number of rotor slots (A) There may be a discontinuity in torque slip characteristics (B) A high starting torque will! (C) The maximum torque will be high (D) The machine may fail to sti available 3-The starting torque of an induction motor is maximum when (A) rotor resistance equals rotor reactance (C) rotor resistance is 1/2 the rotor reactance 4- Crawling is happened in three-phase induction (A) Low voltage (C) Bad mechanical design of the machine (B) rotor resistance is twice the rotor reactan (D) None of the above motor due to --- (B) Heavy loads connected to rotor (D) Harmonics 5- If the applied rated voltage per phase is reduced to one-half, then the starting torque of squir cage induction motor becomes ---------- (A) 4 times the initial value (C) 1/2 times the initial value (B)) 1/4 of the initial value (D) 2 times the initial value 6- The injected e.m.f. in the rotor of induction motor must have (A) zero frequency (C) the same phase as the rotor e.m.f. (B) the same frequency as the slip frequency (D) high value for the satisfactory speed control 7-In double cage induction motor the inner cage has (A) high resistance and high leakage reactance (C) low resistance and high leakage reactance 8- During plugging of an induction motor (A) phase sequence is reversed (C) one phase is open circuited (B) high resistance and low leakage reactar (D) low resistance and low leakage reactan (B) a dc source is connected to stator (D) power is fed back to mains 9- In a 3-phase induction machine, motoring, generating and braking operations take place in the range of slip "s" is (A) 1>s>0, 0>s>-2 and s>1 (C) s > 1, 0>s>-1 and 1>s>0 0>s>-1 (B) s>1, 1>s>-1 and (D) 0>s>−1, s>1 and 1>s> 0 10- When stator resistance starter is used, the factor by which stator voltage reduces is say x. If x<1, then due to stator resistance starter, the starting torque. (A) Increases by fraction x (C) Reduces by fraction x (B) Reduces by fraction x A 2 (D) Increases by fraction x A 2

Delmar's Standard Textbook Of Electricity

7th Edition

ISBN:9781337900348

Author:Stephen L. Herman

Publisher:Stephen L. Herman

Chapter32: Three-phase Motors

Section: Chapter Questions

Problem 6RQ: Name three factors that determine the torque produced by an induction motor.

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