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GATE EE 2021: Electrical Machine Rapid Quiz 2 (App update required to attempt this test)

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Question 1

A 250 V dc shunt machine has armature circuit resistance of 0.6 Ω and field circuit resistance of 125Ω. The machine is connected to 250 V supply mains. The motor is operated as a generator and then as a motor separately. The line current of the machine in both the cases is 50 A. The ratio of the speed as a generator to the speed as a motor is ____________.

Question 2

A transformer is working at its full load and its efficiency is also maximum. Its iron loss is 1 kW then find the copper loss at half load in kW.

Question 3

A 3-phase, 4-pole, 50 Hz, induction motor has a rotor impedance of (0.04 + j1.8) Ω. Neglect stator impedance. The value of external resistance connected in rotor terminal, so that starting torque is 40 % of the maximum torque.

Question 4

The impedances of main and auxiliary windings of a 50 Hz capacitor start single phase induction motor are Zmain = (5+j3) Ω and Zaux = (9+j3.5) Ω. The value of capacitor to be connected in series with the auxiliary winding to achieve a phase difference of 90o between the currents of two windings at starting is

Question 5

A three phase alternator has negligible stator resistance. A short circuit test is conducted on this alternator. At a particular speed a field current is required to drive the rated armature current. If the speed of the alternator is reduced to one-fourth, the field current required to maintain rated armature current is

Question 6

In the magnetic circuit shown in figure, the areas of cross-section of limbs B and C are respectively 0.01 m2 and 0.02 m2. Air gaps of lengths 1.0 mm and 2.0 mm respectively cut in the limbs B and C . If the magnetic medium can be assumed to have infinite permeability and flux in limb B is 1.0 Wb, the flux in limb A is

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Shivang AgrawalShivang AgrawalMember since Jan 2020
M.tech(NIT Nagpur) GATE Ranker[2015-18]
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