Question is ⇒ In variable speed motor, Options are ⇒ (A) a stronger commutating field is needed at low speed than at high speed, (B) a weaker commutating field is needed at low speed than at higt speed, (C) same commutating field is needed at low speed than at high speed, (D) none of the above is correct, (E) , Leave your comments or Download question paper.

Question is ⇒ In variable speed motor, Options are ⇒ (A) a stronger commutating field is needed at low speed than at high speed, (B) a weaker commutating field is needed at low speed than at higt speed, (C) same commutating field is needed at low speed than at high speed, (D) none of the above is correct, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	In variable speed motor
A.	a stronger commutating field is needed at low speed than at high speed [Wrong Answer]
B.	a weaker commutating field is needed at low speed than at higt speed [Correct Answer]
C.	same commutating field is needed at low speed than at high speed [Wrong Answer]
D.	none of the above is correct [Wrong Answer]
View Answer 4 -3 Explanation:- Answer : B Discuss it below : Subhadip santikary Said on 2020-02-05 11:13:14 What is the reason behind it? !! OOPS Login [Click here] is required to post your answer/result Help other students, write article, leave your comments

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⇒ The losses occurring in a D.C. generator are given below. Which loss is likely to have the least proportion ?
Magnetic losses
Armature copper losses
Mechanical losses
Field copper losses

⇒ The starting resistance of a D.C. motor is generally
low
around 500 ohms
1000 ohms
infinitely large

⇒ Compensating winding in a D.C. machine is placed
on yoke in the pole faces
on yoke in the interpolar gap
on armature
none of the above

⇒ In hazardous area of gassy mines, material transportation is done by vehicles powered by
A.C. mains
D.C. mains
I.C. engines
batteries

⇒ If the no-voltage release of a D.C. motor starter fails to work on resumption of supply after a break, the motor will
not start automatically
start automatically without trouble
get damaged
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⇒ For the same H.P. rating and full load speed, following motor has poor starting torque
shunt
series
differentially compounded
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⇒ The current drawn by the armature of D.C. motor is directly proportional to
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up to 10 H.P.
up to 15 H.P.
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run at lower Speed
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motor will burn
motor will not run at all
motor will run at very slow speed
motor will run at very high speed

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The direction of rotation will reverse
Motor will stop
Motor will run at speed lower than the normal speed in the same direction
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power output X efficiency

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commutator
size of conductor
yoke

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limit the armature current
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none of the above

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T_a ∝ I_a
T_a ∝ I/I_a
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⇒ In D.C. machines the residual magnetism is of the order of
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10 to 15 per cent -
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50 to 75 per cent

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the torque increases rapidly
the speed increases rapidly
the current drawn increases rapidly

⇒ Which of the following law/rule can he used to determine the direction of rotation of D.C. motor ?
Lenz's law
Faraday's law
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Cumulative compound motor
Differentially compound motor
Shunt motor
Series motor

⇒ Which D.C. motor will be preferred for machine tools ?
Series motor
Shunt motor
Cumulative compound motor
Differential compound motor

⇒ Which D.C. motor has got maximum self relieving property ?
Series motor
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hysteresis loss
field copper loss
armature copper loss
eddy current loss