Electric Drives (3160919) MCQs

MCQs of Chopper fed DC drive

Showing 1 to 10 out of 20 Questions
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1.

The starting torque of a D.C. motor is independent of which of the following?

(a)

Flux
(b)

Speed
(c)

Armature current
(d)

Flux and armature current
Answer:

Option (b)

2.

Which of the following motors are preferred when quick speed reversal is the main consideration?

(a)

Squirrel cage induction motor
(b)

Wound rotor induction motor
(c)

Synchronous motor
(d)

D.C. motor
Answer:

Option (d)

3.

For the high-frequency choppers, the device that is preferred is

(a)

TRIAC
(b)

Thyristor
(c)

Transistor
(d)

GTO
Answer:

Option (c)

4.

If the current in the armature of d.c series motor is reduced to 5%, the torque of the motor will become:

(a)

50% of the Previous Value
(b)

25% of the Previous Value
(c)

150% of the Previous Value
(d)

100% of the Previous Value
Answer:

Option (b)

5.

The efficiency of the DC motor at maximum power is

(a)

90%
(b)

100%
(c)

Around 80%
(d)

Less than 50%
Answer:

Option (d)

6.

Which speed control method preferred for constant torque drive?

(a)

Field control
(b)

Armature voltage control
(c)

Mechanical loading system
(d)

None of above
Answer:

Option (b)

7.

A step up chopper has input voltage 110 V and output voltage 150 V. The value of duty cycle is

(a)

0.32
(b)

0.67
(c)

0.45
(d)

0.27
Answer:

Option (b)

8.

A step - down choppers can be used in

(a)

Electric traction
(b)

Electric vehicles
(c)

Machine tools
(d)

All of these
Answer:

Option (d)

9.

The average value of the output voltage in a step - down dc chopper is given by

(a)

V 0 = V s
(b)

V 0 = D V s
(c)

V 0 = V s / D
(d)

V 0 = V s / ( 1 - D )
Answer:

Option (b)

10.

Choppers is a

(a)

AC - DC converters
(b)

AC - AC converters
(c)

DC - AC converters
(d)

 DC - DC converters
Answer:

Option (d)

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