MCQs of DC Machines (Electrical Machine - I - 3140913)

Electrical Machine - I (3140913) MCQs

MCQs of DC Machines

Showing 101 to 110 out of 167 Questions

101.

DC series motors are used

(a)	Where load changes operating frequently
(b)	Where constant operating speed is needed
(c)	Where load constant
(d)	Where operating speed is variable and starting torque is high

102.

In the case of DC Shunt Motor electromagnetic torque developed is

(a)	Proportional to the square of armature current
(b)	Proportional to the armature current
(c)	Inversely proportional to the armature current
(d)	None of above

103.

A 240 V DC series motor takes 40 A when giving its rated output at 1500 rpm. Its resistance is 0.3 ohms. The value of resistance which must be added to obtain rated torque at 1000 rpm is

(a)	1.9 ohms
(b)	2.2 ohms
(c)	5.7 ohms
(d)	6 ohms

104.

Interpoles in a DC motor must be

(a)	Series excited and should have the same polarity as that of the ahead main pole in the direction of rotation of the armature
(b)	Shunt excited and should have the same polarity as that of the ahead main pole in the direction of rotation of the armature
(c)	Series excited and should have the same polarity as that of the behind main pole in the direction of rotation of the armature
(d)	Shunt excited and should have the same polarity as that of the behind main pole in the direction of rotation of the armature

105.

Which DC motor will have the least percentage increase of input current, for the same percentage increase in the torque

(a)	DC Series Motor
(b)	DC Shunt Motor
(c)	Compound Wound DC Motor
(d)	Separately Excited DC Motor

106.

Two DC series motors are connected in series and are driving the same mechanical load. If the motors are now connected in parallel the speed will become

(a)	half
(b)	one fourth
(c)	four times
(d)	double

107.

For a given torque, reducing diverter resistance of a DC series motor causes

(a)	decrease in speed demanding less armature current
(b)	decrease in speed but armature current remains the same
(c)	increase in speed but armature current remains the same
(d)	increase in speed demanding more armature current

108.

Field diverter method of speed control of a DC series motor gives speed above rated one due to reduction of

(a)	Line current
(b)	Field current
(c)	Armature current
(d)	None of the above

109.

The field diverter resistance for a DC series motor is of an order of

(a)	0.1
(b)	1
(c)	10
(d)	100

110.

In speed control of DC Series motor, speed lower than the rated speed can be obtained by

(a)	Connecting an additional resistance in the stator circuit
(b)	Connecting an additional resistance in the armature circuit
(c)	Connecting an additional resistance in the field circuit
(d)	Any of the above

Showing 101 to 110 out of 167 Questions