GATE EE 2018 Set 1 — Question 34
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Electrical Machines → DC Machines → Generator & Motor Characteristics
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Question
A separately excited dc motor has an armature resistance . The field excitation is kept constant. At an armature voltage of , the motor produces a torque of at zero speed. Neglecting all mechanical losses, the no-load speed of the motor (in radian/s) for an armature voltage of is _____ (up to 2 decimal places).
Correct answer
600 to 600
Solution
For a separately excited DC motor:
Torque
Back EMF
Voltage equation Step 1: Find from the zero-speed condition.
At zero speed, , so .
.
Given :
.Step 2: Find no-load speed at .
At no-load, neglecting mechanical losses, .
.
.
Torque
Back EMF
Voltage equation Step 1: Find from the zero-speed condition.
At zero speed, , so .
.
Given :
.Step 2: Find no-load speed at .
At no-load, neglecting mechanical losses, .
.
.
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