1201.
Which D.C. motor is generally preferred for cranes and hoists ?
A
Series motor
B
Shunt motor
C
Cumulatively compounded motor
D
Differentially compounded motor
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Which D.C. motor is generally preferred for cranes and hoists ?
Series motor
Shunt motor
Cumulatively compounded motor
Differentially compounded motor
Which D.C. motor has got maximum self relieving property ?
Series motor
Shunt motor
Cumulatively compounded motor
Differentially compounded motor
Which D.C. motor has got maximum self loading property?
Series motor
Shunt motor
Cumulatively compounded motor
Differentially compounded motor
Where D.C. motor of H.P. 12 or more requires frequent starting, stopping, reversingand speed control
four point starter is used
all above can be used
drum type controller is used
three point starter is used
When two D.C. series motors are connected in parallel, the resultant speed is
normal speed
zero
more than the normal speed
loss than the normal speed
When the armature of a D.C. motor rotates, e.m.f. induced is
back e.m.f.
none of the above
self-induced e.m.f.
mutually induced e.m.f.
What will happen if the back e.m.f. of a D.C. motor vanishes suddenly?
The armature may burn
The motor will run noisy
The motor will stop
The motor will continue to run
Ward-Leonard control is basically a
field control method
armature resistance control method
voltage control method
field divertor method
Usually wide and sensitive speed control is desired in case of
steel rolling mills
colliery winders
centrifugal pumps
elevators
Torque developed by a D.C. motor depends upon
current flow through the conductors
all above factors
magnetic field
active length of the conductor
To get the speed of D.C, motor below the normal without wastage of electrical energy is used.
any of the above method
none of the above method
Ward Leonard control
rheostatic control
Three point starter can be used for
compound motor only
both shunt and compound motor
series motor only
shunt motor only
These days D.C. motors are widely used in
electric traction
machine shops
pumping sets
air compressors
The type of D.C. motor used for shears and punches is
differential compoutid D.C. motor
cumulative compound D.C. motor
shunt motor
series motor
The total losses in a well designed D.C. generator of 10 kW will be nearly
1000 W
1500 W
100 W
500 W
The starting resistance of a D.C. motor is generally
1000 Q
infinitely large
low
around 500 Q
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
6.77%
8.84%
2.36%
4.76%
The speed of a D.C. shunt motor more than its full-load speed can be obtained by
decreasing the armature current
increasing the armature current
decreasing the field current
increasing the field current
The speed of a D.C. shunt motor is required to be more than full load speed. This is possible by
reducing the field current
decreasing the armature current
increasing the armature current
increasing the excitation current
The speed of a D.C. shunt motor can be increased by
increasing the resistance in armature circuit
increasing the resistance in field circuit
reducing the resistance in the field circuit
reducing the resistance in the armature circuit