Question is ⇒ For the same H.P. rating and full load speed, following motor has poor starting torque, Options are ⇒ (A) shunt, (B) series, (C) differentially compounded, (D) cumulatively compounded, (E) , Leave your comments or Download question paper.

Question is ⇒ For the same H.P. rating and full load speed, following motor has poor starting torque, Options are ⇒ (A) shunt, (B) series, (C) differentially compounded, (D) cumulatively compounded, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	For the same H.P. rating and full load speed, following motor has poor starting torque
A.	shunt [Wrong Answer]
B.	series [Wrong Answer]
C.	differentially compounded [Correct Answer]
D.	cumulatively compounded [Wrong Answer]
View Answer 7 -3 Explanation:- Answer : C Discuss it below : !! OOPS Login [Click here] is required to post your answer/result Help other students, write article, leave your comments

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⇒ As there is no back e.m.f. at the instant of starting, a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit
a resistance is connected in series with armature
a resistance is connected parallel to the armature
armature is temporarily open circuited
a high value resistor is connected across the field winding

⇒ What will happen if the back e.m.f. of a D.C. motor vanishes suddenly?
The motor will stop
The motor will continue to run
The armature may burn
The motor will run noisy

⇒ Which of the following motors have almost constant speed over their full load range ?
A.C. series motors
D.C. series motors
D.C. shunt motors
Low resistance squirrel cage motors

⇒ A direct on line starter is used for starting motors
up to 5 H.P.
up to 10 H.P.
up to 15 H.P.
up to 20 H.P.

⇒ In D.C. machines the residual magnetism is of the order of
2 to 3 per cent
10 to 15 per cent -
20 to 25 per cent
50 to 75 per cent

⇒ For which of the following applications a D.C. motor is preferred over an A.C. motor ?
Low speed operation
High speed operation
Variable speed operation
Fixed speed operation

⇒ In a D.C. motor, unidirectional torque is produced with the help of
end plates
bushes
commutator
both (b) and (c)

⇒ If the field of a D.C. shunt motor gets opened while motor is running
the speed of motor will be reduced
the armature current will reduce
the motor will attain dangerously high speed
the motor will continue to run at constant speed

⇒ VVhat is the effect produced by the electric current in an electric motor ?
Heating effect only
Magnetic effect only
Heating as well as magnetic effect
Heating as well as chemical effect

⇒ All motors, basically, operate on the principie of either repulsion or
induction
semi-conduction
capacitance
electro-magnetism

⇒ In a D.C. motor constant torque is produced due to
rotor laminations
end-plates
pole shoes
commutator

⇒ The speed of a motor falls from 1100 r.p.m. at no-load to 1050 r.p.m. at rated load. The speed regulation of the motor is
0.0236
0.0476
0.0677
0.0884

⇒ In case the back e.m.f. and the speed of a D.C. motor are doubled, the torque developed by the motor will
remain unchanged
reduce to one-fourth value
increase four folds
be doubled

⇒ If a D.C. motor designed for 40°C ambient temperature is to be used for 50°C ambient temperature, then the motor
of lower H.P. should be selected
of higher H.P. should be selected
can be used for 50°C ambient temperature also
is to be derated by a factor recommended by manufacturer and select the next higher H.P. motor

⇒ Speed control by Ward Leonard method gives uniform speed variation
in one direction
in both directions
below normal speed only
above normal speed only

⇒ The purpose of retardation test on D.C. shunt machines is to find out
stray losses
eddy current losses
field copper losses
windage losses

⇒ In Ward-Leonard control the lower limit of speed is imposed by
residual magnetism of the generator
core losses of motor
mechanical losses of motor and generator together
all of the above

⇒ The function of a field regulator for compound motors is to
control the flux
limit the armature current
demagnetise the field partially
none of the above

⇒ Speed control of a cumulatively compounded D.C. motor can be effected through change of
field resistance
armature resistance
armature voltage
any of the above

⇒ Which of the following motor is preferred for operation in highly explosive atmosphere ?
Series motor
Shunt motor
Air motor
Battery operated motor

⇒ Which of the following application requires high starting torque ?
Lathe machine
Centrifugal pump
Locomotive
Air blower

⇒ In case the conditions for maximum power for a D.C. motor are established, the efficiency of the motor will be
1
around 90%
anywhere between 75% and 90%
less than 50%

⇒ The main disadvantage of Hopkinson's test for finding efficiency of the shunt D.C. motors is that it
needs one motor and one generator
requires two identical shunt machines
requires full-load power
ignores any change in iron loss

⇒ The use of armature divertor in the rheostatic method of speed control for a D.C. shunt motor makes the method
less expensive
less wasteful
suitable for rapidly changing loads
unsuitable for changing loads

⇒ Which loss in a D.C. generator varies with load ?
Copper loss
Eddy current loss
Hysteresis loss
Windage loss

⇒ Which of the following loss of D.C. motor decreases with increase in load ?
Friction and windage loss
Core loss
Brush contact loss
none of the above

⇒ In variable speed motor
a stronger commutating field is needed at low speed than at high speed
a weaker commutating field is needed at low speed than at higt speed
same commutating field is needed at low speed than at high speed
none of the above is correct

⇒ No-load speed of which of the following motor will be highest ?
Shunt motor
Series motor
Cumulative compound motor
Differentiate compound motor

⇒ The power mentioned on the name plate of an electric motor indicates
the power drawn in kW
the power drawn in kVA
the gross power
the output power available at the shaft

⇒ The operation of electric generators and motors depend on the interaction between magnetic field and
copper conductors
electric field
electric current
commutator