Question is ⇒ Where D.C. motor of H.P. 12 or more requires frequent starting, stopping, reversing and speed control, Options are ⇒ (A) drum type controller is used, (B) three point starter is used, (C) four point starter is used, (D) all above can be used, (E) , Leave your comments or Download question paper.

Question is ⇒ Where D.C. motor of H.P. 12 or more requires frequent starting, stopping, reversing and speed control, Options are ⇒ (A) drum type controller is used, (B) three point starter is used, (C) four point starter is used, (D) all above can be used, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	Where D.C. motor of H.P. 12 or more requires frequent starting, stopping, reversing and speed control
A.	drum type controller is used [Correct Answer]
B.	three point starter is used [Wrong Answer]
C.	four point starter is used [Wrong Answer]
D.	all above can be used [Wrong Answer]
View Answer 10 -3 Explanation:- Answer : A 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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⇒ Which of the following steps is likely to result in reduction of hysteresis loss in a D.C. generator ?
Providing laminations in armature core
Providing laminations in stator
Using non-magnetic material for frame
Using material of low hysteresis coefficient for armature core material

⇒ Torque developed by a D.C. motor depends upon
active length of the conductor
current flow through the conductors
number of conductors
radius of armature

⇒ The hysteresis loss in a D.C. generator varies with the frequency of magrietic reversals as
1/f
f
f^1.6
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⇒ The condition for maximum efficiency for a D.C. generator is
eddy current losses = stray losses
hysteresis losses = eddy current losses
copper losses = 0
variable losses = constant losses

⇒ 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

⇒ 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
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be doubled

⇒ In a D.C. motor, unidirectional torque is produced with the help of
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⇒ Where D.C. motor of H.P. 12 or more requires frequent starting, stopping, reversing and speed control
drum type controller is used
three point starter is used
four point starter is used
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⇒ 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 current drawn by the armature of D.C. motor is directly proportional to
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none of the above

⇒ Which of the following tests will be suitable for testing two similar D.C. series motors of large capacity ?
Swinburne's test
Hopkinson's test
Field test
Brake test

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it increases the input power consumption
commutator gets damaged
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none of the above

⇒ A D.C. motor can be easily identified by
winding
commutator
size of conductor
yoke

⇒ If the speed of a D.C. shunt motor is increased the back e.m.f. of the motor will
decrease
increase
remain same
become zero

⇒ In the D.C. motor the iron losses occur in
the field
the armature
the brushes
the commutator

⇒ Regenerative braking on shunt motors is used when
the load is variable
the load is constantly decreasing
the load acts as a braking force
the load has overhauling characteristics.

⇒ In an overloaded motor main danger arises due to
winding getting overheated
busbars getting heated
starter getting damaged
bearings getting overheated

⇒ A 230 V D.C. shlint motor takes 32 A at full load. The back e.m.f. on full load, if the resistance of motor armature and shunt field windings are 0.2 Ω and 115 Ω respectively, will be
210 V
215 V
220 V
224 V

⇒ A series motor is started without load. The effect is that
the back e.m.f. decreases
the torque increases rapidly
the speed increases rapidly
the current drawn increases rapidly

⇒ During rheostatic braking the braking torque is proportional to
speed
(speed)²
(speed)^-1
(speed)^-2

⇒ The armature voltage control of D.C. motor provides
constant voltage drive
constant current drive
constant torque drive
none of the above

⇒ D.C. series motors are used
where load is constant
where load changes frequently
where constant operating speed is needed
in none of the above situations.

⇒ Which of the following can be used to control the speed of a D.C. motor ?
Thermistor
Thyristor
Thyratron
Transistor

⇒ Which of the following load normally needs starting torque more than the rated torque?
Blowers
Conveyors
Air compressors
Centrifugal pumps

⇒ Speed ,control by varying the armature circuit resistance, in a D.C. motor, provides a
constant torque drive
variable torque drive
constant power drive
variable power drive

⇒ Which of the following methods is most effective in finding out the no load losses in a large D.C. shunt motor ?
Field's test
Ward-Leonard test
Block rotor test
Swinburne's test

⇒ Which of the following tests can be used to determine no-load losses in a D.C. shunt motor ?
Running down test
Swinburne's test
Field test
Brake test

⇒ Which of the following methods gives the greatest breaking torque ?
Regenerative braking
Plugging
Rheostatic braking
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⇒ Which D.C. motor will be preferred for cónstant speed line shafting ?
Cumulative compound motor
Differentially compound motor
Shunt motor
Series motor

⇒ In D.C. shunt motors as load is reduced
the speed will increase abruptly
the speed will increase in proportion to reduction in load
the speed will remain almost constant
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