Electric Drives (3160919) MCQs

MCQs of Control of slip ring induction motor

Showing 11 to 20 out of 22 Questions
1 2 3
11.

The drawback of speed control of a slip ring induction motor with the help of resistance in the circuit is that

(a)

It is applicable only to motors having power of more than 100 kW
(b)

It results in high losses
(c)

With reduction in speed, the torque decreases significantly
(d)

The speed can be controlled only very broadly
Answer:

Option (b)

12.

In static scherbius drive, if 's' is slip, 'Pg' is power transferred to rotor and 'ω' is speed then developed torque is given by

(a)

T=Pg/(s.ω)
(b)

T=Pg.s/ω
(c)

T=Pg.s.ω
(d)

T=1/Pg.s.ω
Answer:

Option (a)

13.

In static scherbius drive, maximum value of α (firing angle) is restricted to _______° for safe commutation of inverter thyristor

(a)

90
(b)

180
(c)

165
(d)

145
Answer:

Option (c)

14.

The slip recovery scheme is a part of the synchronous speed changing technique.

(a)

True
(b)

False
Answer:

Option (a)

15.

In the rotor voltage injection method, when an external voltage source is in phase with the main voltage then speed will ___________

(a)

Increase
(b)

Decrease
(c)

 Remain unchanged
(d)

First increases then decrease
Answer:

Option (a)

16.

If P2 is the rotor input power, Pm is the gross mechanical power developed and s is the slip of induction motor, then the gross mechanical power developed is

(a)

s P2
(b)

(1-s) P2
(c)

P2 / s
(d)

P2 / (1-s)
Answer:

Option (b)

17.

“By adding external resistance to rotor till it becomes equal to rotor reactance, the maximum torque can be achieved at start”. This statement holds for

(a)

Slip ring induction motor
(b)

Squirrel cage induction motor
(c)

 Both a and b
(d)

Neither a nor b
Answer:

Option (a)

18.

A 50 Hz, 3 phase slip ring induction motor, has 6 poles on stator and 4 poles on rotor. Then the machine will run at

(a)

1000 rpm
(b)

1500 rpm
(c)

1400 rpm
(d)

Machine will not run at all
Answer:

Option (d)

19.

The disadvantages of scherbius system used for speed controlling in 3 phase induction motor is

(a)

It cannot be used for slip ring induction motors
(b)

It cannot be used for squirrel cage induction motors
(c)

It can be used for large induction motors
(d)

None of these
Answer:

Option (b)

20.

Kramer system for controlling the speed of 3 phase induction motor is mostly used for motors of

(a)

Above 4000 kW
(b)

 Below 4000 kW
(c)

Below 3000 kW
(d)

None of these
Answer:

Option (a)

Showing 11 to 20 out of 22 Questions
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