In D.C. machines the residual magnetism is of the order of
2 to 3 per cent
50 to 75 per cent
20 to 25 per cent
10 to 15 per cent
2 to 3 per cent
In a D.C. shunt motor under the conditions of maximum power the current in the armature will be
more than full-load current
rated full-load current
almost negligible
less than full-load current
more than full-load current
In case-the conditions for maximum power for a D.C. motor are established the efficiency of the motor will be
anywhere between 75% and 90%
less than 50%
1
around 90%
less than 50%
In D.C. motor which of the following can sustain the maximum temperature rise?
Field winding
Slip rings
Commutator
Armature winding
Field winding
The speed of a D.C. series motor is
proportional to field current
proportional to the square of the armature current
proportional to the armature current
inversely proportional to the armature current
inversely proportional to the armature current
By looking at which part of the motor it can be easily confirmed that a particular motor is D.C. motor?
Frame
Shaft
Commutator
Stator
Commutator
Which of the following load normally needs starting torque more than the rated torque?
Conveyors
Centrifugal pumps
Air compressors
Blowers
Conveyors
The starting resistance of a D.C. motor is generally
low
1000 Q
around 500 Q
infinitely large
low
In a D.C. series motor if the armature current is reduced by 50% the torque of the motor will be e toqual
10% of the previous value
25% of the previous value
100% of the previous value
50% of the previous value
25% of the previous value
The current drawn by the armature of D.C. motor is directly proportional to
the torque required
the speed of the motor
the voltage across the terminals
none of the above
the torque required
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