Electric Drives (3160919) MCQs

MCQs of DC motor characteristics

Showing 41 to 50 out of 71 Questions
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41.

 When the speed of the DC motor is Increases its Armature current

(a)

Increases
(b)

Decreases
(c)

Remain Constant
(d)

Any of the above
Answer:

Option (b)

42.

The amount of back e.m.f. of a shunt motor will increase when

(a)

When the Load is Increased
(b)

When the Field is Weakened
(c)

When the Field is strengthed
(d)

None of the above
Answer:

Option (b)

43.

A 250 V, DC shunt motor takes a line current of 20 A. The resistance of shunt field winding is 200Ω and resistance of the armature is 0.3 Ω Find the armature current and the back e.m.f.

(a)

18.75 A, 245 V
(b)

25.32 A, 225 V
(c)

15.65 A, 100 V
(d)

10 A, 150 V
Answer:

Option (a)

44.

A 4 pole, 250 V, dc series motor has a wave-connected armature with 200 conductors. The flux per pole is 25 mWb when the motor is drawing 60 A from the supply. The armature resistance is 0.15 Ω while series field winding resistance is 0.2 Ω.Calculate the speed under this condition.

(a)

1500 RPM
(b)

1470 RPM
(c)

1300 RPM
(d)

1374 RPM
Answer:

Option (d)

45.

A 500 V shunt motor runs at its normal speed of 250 RPM when the armature current is 200 A. The resistance of armature is 0.12 Ω. Calculate the speed when resistance is inserted in the field reducing the shunt field to 80% of normal value and the armature current is 100A.

(a)

420 RPM
(b)

540 RPM
(c)

320 RPM
(d)

1500 RPM
Answer:

Option (c)

46.

The shaft torque (Tsh) in a d.c motor is less than total armature torque (Ta) because of ____________ in the motor.

(a)

Copper losses
(b)

Field Losses
(c)

Iron and Friction losses
(d)

None of the above
Answer:

Option (c)

47.

The torque developed by a d.c motor is directly proportional to

(a)

Flux per pole × Armature current
(b)

Armature resistance × Applied voltage
(c)

Armature Resistance × Armature current
(d)

Square of armature resistance
Answer:

Option (a)

48.

A 4 pole d.c motor takes a 50 A armature current. The armature has lap connected 480 conductors. The flux per pole is 20 mWb. Calculate the gross torque developed by the armature of the motor.

(a)

76.32 N-m
(b)

80.34 N-m
(c)

50 N-m
(d)

25.45 N-m
Answer:

Option (a)

49.

Armature reaction in a DC motor is increased

(a)

When the armature current decreases
(b)

When the armature current Increases
(c)

When the field current increases
(d)

By Interpoles
Answer:

Option (b)

50.

In flux control method the speed of DC motor is obtained _____

(a)

Above Base speed

 
(b)

Below base speed

 
(c)

Both above and below base speed

 
(d)

Remain constant
Answer:

Option (a)

Showing 41 to 50 out of 71 Questions
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