Induction Motor MCQ Part 4

Induction Motor MCQ Part 4

Electrical Engineering MCQ on Induction Motor.

What is the approximate efficiency of a 3 phase, 4, 60 Hz induction motor running at an RPM 1200

What is the approximate efficiency of a 3 phase, 4, 60 Hz induction motor running at an RPM 1200:

  1. 50%
  2. 66.66%
  3. 78.98%
  4. 86%

Correct answer: 2. 66.67%

Solution:

Solution: Ns = 120*f/P = 1800

s = (Ns – N)/Ns = 0.33

Approximate efficiency = 1 – s = 1 – 0.33 = 0.66 = 66.66%

A voltmeter gives 180 oscillations per minute when connected to the rotor of the induction motor. Calculate the slip if the supply frequency is 60 Hz

A voltmeter gives 180 oscillations per minute when connected to the rotor of the induction motor. Calculate the slip if the supply frequency is 60 Hz:

  1. 2%
  2. 5%
  3. 8%
  4. 11%

Correct answer: 2. 5%

Solution:

f’ = 180/60 = 3

s = f’/f = 3/60 = 0.05 = 5%

Value of rotor reactance as compared to rotor resistance at starting instance of 3 Phase Induction Motor

The rotor reactance of 3 phase induction motor at the instance of starting is ___________ as compared to rotor resistance:

  1. Smaller
  2. Identical
  3. Larger
  4. None of the above

Correct answer: 3. Larger

If a 3 phase induction motor is running at certain slip s. Then rotor copper losses expressed mathematically are

If a 3 phase induction motor is running at certain slip s. Then rotor copper losses expressed mathematically are:

  1. s * rotor input
  2. (1 – s) * rotor input
  3. (1 + s) * rotor input
  4. 2s * rotor input

Correct answer: 1. s * rotor input

The induction motor is best described in three words as

The induction motor is best described in three words as:

  1. Singly excited machine
  2. Doubly excited machine
  3. Triply fed machine
  4. Quad fed machine

Correct answer: 1. Singly fed excited machine

More MCQ on Induction Motors

  1. The Correct Statement about DC field current in Induction Motor
  2. The Induction Motor Runs at the Speed
  3. The Correct Relationship between Slip, Synchronous, and Rotor speed of Induction Motor
  4. Formula for Synchronous Speed of Induction Machine
  5. Five
  6. The synchronous speed of 4 pole, 50 Hz induction Motor is
  7. A 4 pole, 60 Hz Induction Motor Has a Slip of 5%. The Speed of motor is
  8. A 4 pole, 50 Hz Induction Motor Has a Slip of 5%. The Speed of motor is
  9. Size of Single Phase Induction Motor vs Three Phase Induction Motor for Same Ratings
  10. Usually, a Single Phase Induction Motor has number of poles
  11. The rotor frequency of a 4 pole, 60 Hz induction motor having full load slip of 5% at rated load is
  12. If rotor of Induction motor is rotating at synchronous speed the torque will be
  13. What is No-load slip value in induction motor
  14. The current in the starting winding of capacitor-start single-phase motors has what relationship with voltage [49]
  15. What will happen to a single-phase motor when its capacitor is short-circuited
  16. With reference to a capacitor-start and run motor the function of the running capacitor in series with the auxiliary winding is
  17. WREF capacitor-start motor the phase displacement between starting and running winding can be nearly
  18. In a split-phase induction motor which winding is connected through centrifugal switch

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