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GATE 2022: Electrical Machines - 56

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Question 1

In Scott connection, if the turns ratio of primary to secondary of main transformer is K, then the teaser transformer has the transformation ratio of

Question 2

Which of the following statement is true for a DC machine. (Here ϕ is flux per pole)

Question 3

A 2500/ 250V, 25 kVA, transformer is connected as an auto transformer to 2500/2750 V. Its rating would be:

A. 250 kV

Question 4

A transformer has iron loss of 90 W at 60 Hz supply and 52 W at 40 Hz supply. Both losses being measured at same peak flux density. The total iron loss in the transformer at 50 Hz supply will be:

Question 5

A 4 pole, 3-phase, 50 Hz, induction machine has rotor resistance and reactance of 0.02 and 1.2 Ω respectively at standstill. If the slip at maximum torque is 0.1.What will be the percentage improvement in power factor after addition of external resistance?

Question 6

The figure shows plots of speed (N) Vs. armature current (Ia) of a dc motor for two different operating conditions. Which one of the following features is relevant?

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Jun 25ESE & GATE EE

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Chetan GoyalChetan GoyalMember since Mar 2021
AIR 1805, GATE2021
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