Question is ⇒ Hopkinson's test is conducted at, Options are ⇒ (A) no load, (B) part load, (C) low load, (D) full load, (E) , Leave your comments or Download question paper.

Question is ⇒ Hopkinson's test is conducted at, Options are ⇒ (A) no load, (B) part load, (C) low load, (D) full load, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	Hopkinson's test is conducted at
A.	no load [Wrong Answer]
B.	part load [Wrong Answer]
C.	low load [Wrong Answer]
D.	full load [Correct Answer]
View Answer 4 -1 Explanation:- Answer : D 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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⇒ The armature voltage control of D.C. motor provides
constant torque drive
constant voltage drive
constant current drive
none of the above

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

⇒ In a D.C. shunt motor, under the conditions of maximum power, the current in the armature will be
almost negligible
rated full-load current
less than full-load current
more than full-load current

⇒ 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

⇒ In which of the following tests only one motor is required ?
Brake test
Hopkinson's test
Field's test
Swinburne's test

⇒ 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

⇒ In Ward Leonard method of speed control of a D.C. motor, change in speed of motor is obtained by the
change in armature voltage of D.C. motor
change in the field excitation of the D.C. motor
change in armature current of D.C. motor
change in supply voltage

⇒ Which of the following motor has the poorest speed regulation ?
Shunt motor
Series motor
Differential compound motor
Cumulative compound motor

⇒ Speed control by the variation of flux, in a D.C. shunt motor, will give
constant torque drive
variable torque drive
constant power drive
variable power drive

⇒ Which loss in a D.C. generator does not vary with load as well as flux density ?
Copper loss
Eddy current loss
Hysteresis loss
Windage loss

⇒ Which of the following motors, on removal of load, will run at the highest speed ?
Shunt motor
Series motor
Differential compound
Cumulative compound

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

⇒ 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

⇒ In electric motors carbon brushes are used to
provide a path for flow of current
prevent sparking during commutation
prevent overheating of armature windings
brush off carbon deposits on the commutator

⇒ 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.

⇒ 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

⇒ Ward-Leonard control is basically a
voltage control method
field divertor method
field control method
armature resistance control method

⇒ In D.C. machines fractional pitch winding is used
to improve cooling
to reduce copper losses
to increase the generated e.m.f.
to reduce the sparking

⇒ Which one of the following is not the function of pole shoes in a D.C. machine ?
To reduce eddy current loss
To support the field coils
To spread out flux for better uniformity
To reduce the reluctance of the magnetic path

⇒ Which of the following methods of braking is used in rolling mills ?
Dynamic braking
Plugging
Regenerative braking
Mechanical brakes

⇒ 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

⇒ Regenerative method of braking is based on that
back e.m.f. is less than the applied voltage
back e.m.f. is equal to the applied voltage
back e.m.f. of rotor is more than the applied voltage
none of the above

⇒ 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
the speed will reduce

⇒ Three point starter can be used for
series motor only
shunt motor only
compound motor only
both shunt and compound motor

⇒ Which method of braking is generally used in elevators ?
Plugging
Regenerative braking
Rheostatic braking
None of the above

⇒ As compared to an induction motor, the air gap in a D.C. motor is
less than 50%
between 50% and 90%
same
more

⇒ The speed of a D.C. shunt motor more than its full-load speed can be obtained by
decreasing the field current
increasing the field current
decreasing the armature current
increasing the armature current

⇒ In D.C. motor which of the following can sustain the maximum temperature rise?
Slip rings
Commutator
Field winding
Armature winding

⇒ Buses, trains, trolleys, hoists, cranes require high starting torque and therefore make use of
D.C. series motor
D.C. shunt motor
induction motor
all of above motors

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