multiple choice questions on induction machines # 19

                            Hi friends, this post is about induction motor objectives. These are some of the questions asked in previous question papers of Gate, IES and other competitive exams. check out and comment if you have any doubts....

objectives on induction machines #19

1) A squirrel cage induction motor having a rated slip of 4% of full load has a starting torque same as the full load torque. Which one of the following statements is correct? The starting current is
A) equal to the full-load current
B) twice the full-load current
C) four times the full-load current
D) five times the full-load current

Ans:D

2) An induction motor having full-load torque of 60 Nm when delta connected develops a starting torque of 120 Nm. For the same supply voltage, if the motor is changed to star-connection, the starting torque developed will be
A) 40 Nm
B) 60 Nm
C) 90 Nm
D) 120 Nm

Ans:A

3) A 3-phase, 480 V, 60 Hz induction motor is to be operated at 50 Hz supply. The most satisfactory supply voltage for the machine would be
A) 480 V
B) 400 V
C) 600 V
D) 440 V

Ans:B

4) If a 3-phase 350 V, 50Hz, 1440 rpm induction motor is operated on 420 V, 60 Hz supply, then the torque will
A) increase
B) decrease
C) remain unchanged
D) none of these

Ans:C

5) The starting torque of an induction motor varies as
A) f
B) 1/f^2
C) 1/f
D) f^2

Ans:B

6) With the increase in supply frequency.....................decrease
A) starting current
B) starting torque
C) full load current
D) maximum running torque
E) starting and full load currents and starting and maximum running torque

Ans:E

7) This size of a high speed motor is .................... in comparison to that of a lower speed motor for the same Kw output
A) smaller
B) larger
C) almost the same
D) unpredictable

Ans:A

8) Which of the following induction motors will operate on the lowest value of power factor?
A) 7.5 Kw, 950 rpm
B) 7.5 Kw, 1440 rpm
C) 15 Kw, 950 rpm
D) 15 Kw, 1440 rpm

Ans:A

9) For starting a 3-phase induction motor.................... winding is to be connected to 3-phase supply
A) rotor
B) stator
C) both stator and rotor
D) none

Ans:B

10) The starting current of a 3-phase induction motor is about .................. of its full-load rated current
A) half
B) twice
C) 5 to 7 times
D) 15 to 20 times

Ans:C

                   These are some of the objectives of induction machines.. If you like my post share it with your friends and subscribe for latest updates..
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