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BARC EE : Electrical Machines Quiz-1

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Question 1

A 10-pole lap wound DC armature has a total of 200 conductors, each with a current carrying capacity of 10 A. The average induced emf per conductor is 10 V. The power rating of the DC machine is

Question 2

The full load output current when the maximum efficiency for a transformer having core loss of 200 W occurs at 80% loading and equivalent resistance referred to secondary of 2.5 Ω is:

Question 3

What is the condition of retrogressive winding in dc machines?

Question 4

Buchholz’s relay is used in:

Question 5

Two DC machines are mechanically coupled. One is operating as a motor and the other as generator. The iron and frictional losses of the machines will be identical when:

Question 6

The full load copper loss of a transformer working at unity power factor is W_c watts. The copper loss at full load 0.8 Pf will be?

Question 7

If the current drawn by a DC series motor is increased from 10 A to 12 A (neglect saturation), what is the increase in torque expressed as percentage of initial torque?

Question 8

Find the percentage loading at which maximum efficiency occur in a single phase transformer with full load iron and copper losses as 3 kW and 8 kW respectively.

Question 9

For a DC shunt generator at 800 rpm critical field resistance of 200 Ω. Now speed increased by 200 rpm. Change in critical field resistance is

Question 10

Which of the following combinations of three phase transformer is rarely used due to harmonic considerations?

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ESE & GATE EE Electrical Machines

Nov 23ESE & GATE EE