GATE EE 2021 Set 1 — Question 54
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Electrical Machines → DC Machines → Generator & Motor Characteristics
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Question
A belt-driven DC shunt generator running at 300 RPM delivers 100 kW to a 200 V DC grid. It continues to run as a motor when the belt breaks, taking 10 kW from the DC grid. The armature resistance is , field resistance is , and brush drop is 2 V. Ignoring armature reaction, the speed of the motor is ______ RPM. (Round off to 2 decimal places.)
Correct answer
273 to 277
Solution
1.Generator Mode:
kW, VLine current A
Field current A
Armature current A
Generated EMF V
Speed RPM
2.Motor Mode:
kW, VLine current A
Field current A (constant since and are constant)
Armature current A
Back EMF V
3.Speed Calculation:
Since flux is constant ( is same), RPM.
Rounding to 2 decimal places, we get 275.19 RPM.
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