Question is ⇒ Which of the following tests can be conducted on all types of D.C. machines ?, Options are ⇒ (A) Hopkinson's test, (B) Running down test, (C) Block rotor test, (D) Field's test, (E) Brake test, Leave your comments or Download question paper.

Question is ⇒ Which of the following tests can be conducted on all types of D.C. machines ?, Options are ⇒ (A) Hopkinson's test, (B) Running down test, (C) Block rotor test, (D) Field's test, (E) Brake test, Leave your comments or Download question paper. Previous question Next question


Q1.	Which of the following tests can be conducted on all types of D.C. machines ?
A.	Hopkinson's test [Wrong Answer]
B.	Running down test [Wrong Answer]
C.	Block rotor test [Wrong Answer]
D.	Field's test [Wrong Answer]
E.	Brake test [Correct Answer]
View Answer 6 -3 Explanation:- Answer : E 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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Also Read Similar Questions Below :

⇒ The mechanical power developed by a D.C. motor is equal to
power input + losses
back e.m.f. X armature current
power output X losses
power output X efficiency

⇒ 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

⇒ Which of the following loss in a D.C. generator varies significantly with the load current ?
Field copper loss
Windage loss
Armature copper loss
None of the above

⇒ In a D.C. series motor, if the armature current is reduced by 50%, the torque of the motor will be equal to
100% of the previous value
50% of the previous value
25% of the previous value
10% of the previous value

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

⇒ D.C. generators are normally designed for maximum efficiency around
full-load
rated r.p.m.
rated voltage
all of the above

⇒ The retardation test is applicable to shunt motors and generators and is used to find
the copper losses
the stray losses
the friction losses
the eddy current losses

⇒ The hysteresis loss in a D.C. machine least depends on
Frequency of magnetic reversals
Maximum value of flux density
Volume and grade of iron
Rate of flow of ventilating air

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

⇒ 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

⇒ For the same H.P. rating and full load speed, following motor has poor starting torque
shunt
series
differentially compounded
cumulatively compounded

⇒ If B_max is the maximum flux density, then eddy cu rrent loss will vary as
B_max
(B_max)²
(B_max)^1.2
(B_max)^2.4

⇒ Which losses can be determined by performing the retardation test ?
Friction losses
Eddy current losses
Stray losses
Copper losses

⇒ 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

⇒ A D.C. series motor, as compared to shunt and compound motors, has the highest torque at the start because of its comparatively
stronger series field
lower armature resistance
large armature current
fewer series turns

⇒ 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.

⇒ 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

⇒ If T_a be the torque and Ia the armature current for a D.C. motor, then which of the following relation is valid before saturation ?
T_a ∝ I_a
T_a ∝ I/I_a
T_a ∝ I_a²
T_a ∝ ^I/_{I_a²}

⇒ 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

⇒ If the terminals of armature of D.C. motor are interchanged, this action will offer following kind of braking
regenerative
plugging
dynamic braking
none of the above

⇒ D.C. shunt motors are used for driving
trains
cranes
hoists
machine tools

⇒ While starting a differential compound motor, it is best to short the series field in order to avoid
excessive starting period
motor starting in wrong direction
tripping of the circuit breaker
large in rush of current

⇒ 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
Coloumb's law
Fleming's left-hand rule

⇒ Which D.C. motor will be preferred for cónstant speed line shafting ?
Cumulative compound motor
Differentially compound motor
Shunt motor
Series motor

⇒ For starting a D.C. motor a starter is required because
it limits the speed of the motor
it limits the starting current to a safe value
it starts the motor
none of the above

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

⇒ Why are the D.C. motors preferred for traction applications ?
Torque and speed are inversely proportional to armature current
Torque is proportional to armature current
Torque is proportional to square root of armature current
The speed is inversely proportional to the torque and the torque is proportional to square of armature current

⇒ Which of the following motors is most suitable for signalling devices and many kinds of timers ?
D.C. shunt motor
D.C. series motor
Induction motor
Reluctance motor

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

⇒ 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