GATE EE concept:separately-excited PYQs & Answers

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concept:separately-excited

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Questions 1–6 of 6. Imported answers require independent review unless marked reviewed.

Topic practice 6 questionsPage 1 of 1

A single-phase full-controlled thyristor converter bridge is used for regenerative braking of a separately excited DC motor with the following specifications:

Specification	Value
Rated armature voltage	210 V
Rated armature current	10 A
Rated speed	1200 rpm
Armature resistance	1 Ω
Input to the converter bridge	240 V at 50 Hz
The armature of the DC motor is fed from the full-controlled bridge and the field current is kept constant.

Assume that the motor is running at 600 rpm and the armature terminals of the motor are suitably reversed for regenerative braking. If the armature current of the motor is to be maintained at the rated value, the triggering angle of the converter bridge in degrees should be ______ (rounded off to 2 decimal places).

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A separately excited DC motor rated 400 V, 15 A, 1500 RPM drives a constant torque load at rated speed operating from 400 V DC supply drawing rated current. The armature resistance is 1.2 Ω. If the supply voltage drops by 10% with field current unaltered then the resultant speed of the motor in RPM is __________ (Round off to the nearest integer).

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A 280 V, separately excited DC motor with armature resistance of 1 Ω and constant field excitation drives a load. The load torque is proportional to the speed. The motor draws a current of 30 A when running at a speed of 1000 rpm. Neglect frictional losses in the motor. The speed, in rpm, at which the motor will run, if an additional resistance of value 10 Ω is connected in series with the armature, is __________. (round off to nearest integer)

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A separately excited dc motor has an armature resistance

. The field excitation is kept constant. At an armature voltage of 100 V, the motor produces a torque of 500 Nm at zero speed. Neglecting all mechanical losses, the no-load speed of the motor (in radians/s) for an armature voltage of 150 V is ____ (up to 2 decimal places).

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A 220 V, 10 kW, 900 rpm separately excited DC motor has an armature resistance

. When the motor operates at rated speed and with rated terminal voltage, the electromagnetic torque developed by the motor is 70 Nm. Neglecting the rotational loss of the machine, the current drawn by the motor from the 220 V supply is

Your answerChoose one option.

34.2 A

30 A

22 A

4.84 A

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A separately excited DC generator supplies 150 A to a 145 V DC grid. The generator is running at 800 RPM. The armature resistance of the generator is 0.1Ω. If the speed of the generator is increased to 100 RPM, the current in amperes supplied by the generator to the DC grid is ________. (Give the answer up to one decimal place.)

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GATE EE concept:separately-excited PYQs

How to practice concept:separately-excited

Question 65

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