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GATE 2020: Electrical Machines Rapid Mini Mock (App update required to attempt this test)

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Question 1

Distributed winding and short chording employed in AC machines will result in

Question 2

A three-phase, three-stack, variable reluctance step motor has 20 poles on each rotor and stator stack. The step angle of this step motor is

Question 3

The dc motor, which can provide zero speed regulation at full load without any controller, is.

Question 4

Group I lists different applications and Group II lists the motors for these applications. Match the application with the most suitable motor and choose the right combination among the choices given thereafter

Question 5

A separately excited DC generator has an armature resistance of 0.1Ω and negligible armature inductance. At rated field current and rated rotor speed, its open-circuit voltage is 200 V. When this generator is operated at half the rated speed, with half the rated field current, an unchanged 1000 μF capacitor is suddenly connected across the armature terminals. Assume that the speed remains unchanged during the transient. At what time (in microsecond) after the capacitor is connected will the voltage across it reach 25 V?

Question 6

A three phase squirrel cage Induction motor has a starting current of five times the full load current if a star delta starter is used to start the motor the per unit starting torque will be. (the full load slip is 6%)______?

Question 7

A DC machine running at 800 rpm induced voltage is 220V. What will be percentage increase in field flux if the induced emf is 240V at 600 rpm?

Question 8

The emf induced in a conductor of machine driven at 600 rpm, the peak value of flux density is 1 Wb/m2, diameter of machine 2 m and length of machine 0.3 m is ______ V.

Question 9

A 11/6.6/0.5kV, star/star/delta, three winding transformer has a magnetizing current of 3A. At rated voltages, the secondary supplies a balanced load of 300 kVA at 0.8 pf lag and tertiary supplies a balanced load of 150 kW at 0.9 pf lead. The magnitude of primary phase current (in Amp) will be

Question 10

A belt driven dc shunt generator runs at 1500 rpm delivering 10 kW, at 220 V bus bars. The belt breaks, following which the machine operates as a motor drawing 2 kW power. What will be its speed as a motor? The armature and field resistances are 0.25 ohms and 55 ohms respectively. Ignore armature reaction and assume the contact drop at each brush to be 1 V.

Question 11

The power input to a 415V, 50 Hz, 6 pole, 3-phase induction motor running at 975 rpm is 40 kW. The stator losses are 1kW and friction and windage losses total 2 kW. The efficiency of the motor is

Question 12

A 500 V series motor of resistance 0.5

runs at 600 rpm when the current is 50 A. If an identical motor is mechanically coupled and joined in series,___________ A will be when the set runs at 200 rpm and exerts twice the original gross torque?

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ESE & GATE EE Electrical Machines

Dec 23ESE & GATE EE