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SSC JE 2017: Electrical Machines Rankers Quiz 6

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Question 1

The secondary load impedance of a step-up transformer is The primary impedance will be

Question 2

A single phase transformer has a full-load secondary current of 500 A ; the primary current being one-fifth of this value. The transformer has the following parameters :

If the secondary is short-circuited, find the primary voltage required to circulate full-load current. Neglect no-load current.

Question 3

In a transformer, the iron loss is and full-load Cu loss in The efficiency of the transformer at full-load at 0.8 p.f. lagging is

Question 4

If the slip of a 3-phase induction motor increases, the p.f. of the rotor circuit ………………………

Question 5

An 8-pole alternator runs at and supplies power to a 6-pole induction motor which has a full-load slip of 3%. The full-load speed of the motor is

Question 6

The starting torque of a 3-phase induction motor has maximum value. The rotor power factor is then

Question 7

Commutation conditions at full-load for a large D.C. machine can be checked by _________.

Question 8

The break test for the determination of efficiency of a D.C. machine is _______.

Question 9

How are transformers generally cooled for installations rated at less than 5 kVA?

Question 10

The losses in a transformer are:
(a) copper loss
(b) hysteresis loss
(c) eddy current loss
The constant power loss in a transformer is given by ;
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Jan 6ESE & GATE EE