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Total Questions : 473 | Page 45 of 48 pages
Question 441. 9.  The single-phase induction motor is started with
  1.    capacitarcP concoction
  2.    inductance connection
  3.    resistance connection
  4.    shaded pole arrangement
 Discuss Question
Answer: Option B. -> inductance connection
Question 442. 0. Low voltage starting of induction motors is prescribed because
  1.    high starting current at full voltage would damage the windings
  2.    it facilitates smooth acceleration
  3.    it increases the life of the motor
  4.    it is mandated by electric supply authorities to prevent voltage dips at other consumer premises
 Discuss Question
Answer: Option A. -> high starting current at full voltage would damage the windings
Question 443. 1.  While plugging a 3-phase induction motor, if one supply terminal gets disconnected, then the motor will
  1.    Continue to run in the same direction
  2.    stop
  3.    start rotating in the opposite direction at the same speed
  4.    start rotating in the opposite direction at reduced speed
 Discuss Question
Answer: Option A. -> Continue to run in the same direction
Question 444. 2.  The stator of a 415V, 50Hz, 6-pole, 970 rpm, 3-phase slipring induction motor is fed with normal voltage. The rotor with slip rings open-circuited is rotated at 500 rpm along the normal direction of its rotation. The frequency of the voltage across slip rings will be
  1.    1.5 Hz
  2.    25 Hz
  3.    26.5 Hz
  4.    75 Hz
 Discuss Question
Answer: Option B. -> 25 Hz
Question 445. 3. The given figure shows typical torque-speed curves of the following induction motors A. Ordinary cage B. Double cage C. Deep bar rotor D. Slip ring motor 1 The correct matching of the motors and torque-speed curves is Codes :
  1.    2,3,4,1
  2.    3,2,1,4
  3.    4,2,1,3
  4.    4,1,2,3
 Discuss Question
Answer: Option D. -> 4,1,2,3
Question 446. 6.  Consider the following statements : As a 3-phase induction motor is loaded from noload to rated load,I. there is an improvement in the power factor.2. the torque increases almost in proportion to slip.3. the air-gap flux falls shorply. Of these statements :
  1.    1, 2 and 3 are correct
  2.    1 and 2 are correct
  3.    2 and 3 are correct
  4.    1 and 3 are correct
 Discuss Question
Answer: Option B. -> 1 and 2 are correct
Question 447. 4.  Consider the following statements about the operation of a three-phase induction motor running at full load : If one of the supply line fuse blows off, the motor will stall. 2. continue to run with increased slip, 3. continue to run with normal supply current 4. continue to run with excessive supply current Of these statements
  1.    1 alone is correct
  2.    3 alone is correct
  3.    2 and 3 are correct
  4.    2 and 4 are correct
 Discuss Question
Answer: Option D. -> 2 and 4 are correct
Question 448. 7.  In a 3-phase induction motor, if the angular speed of the stator field is w and, the actual angular speed of the rotor is wr, and the stator induced emf is given by es = N1 wKws Qisin wt, (N1 being the stator turns/phase), the rotor emf with N2 as the rotor/turns phase will be (Kws = stator winding factor and Kwr =rotor winding factor)
  1.    er = N2 co Kwr sin cot
  2.    er = N2 cor Kwr sin cort
  3.    er = N2 (co? cod Kcorcp sin (co ? cor)t
  4.    er = N2 (Co + cod Kmr(1) sin (w + (Or)t
 Discuss Question
Answer: Option A. -> er = N2 co Kwr sin cot
Question 449. 5.  The phenomenon of crawling is usually not formed in slip-ring because these motors have
  1.    no space harmonics
  2.    high resistance rotor windings
  3.    no zig-zag leakage
  4.    comparatively large air-gap
 Discuss Question
Answer: Option C. -> no zig-zag leakage
Question 450. 8. A 3-phase induction motor requires a stater
  1.    because there is no back emf induced in the stator winding during starting
  2.    because the motor does not possess an inherent starting torque
  3.    because the induced secondary voltage and hence the currents in the windings are abnormally high during starting
  4.    to increase the starting torque
 Discuss Question
Answer: Option C. -> because the induced secondary voltage and hence the currents in the windings are abnormally high during starting

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