MGVCL Exam Paper (30-07-2021 Shift 1)
A transformer designed for operation at 60 Hz supply is working at 50 Hz supply system without changing its voltage and current ratings. Compared to the full load efficiency at 60 Hz, the full load transformer efficiency at 50 Hz.

decreases marginally
increases marginally
increases by 30%
remains unaltered

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MGVCL Exam Paper (30-07-2021 Shift 1)
Determine the ohmic value of the current limiting reactor per phase external to a 30 MVA, 11 kV, 50 Hz, three phase synchronous generator which can limit the current on short circuit of 5 times the full load current. The reactance of the synchronous generator is 0.05 pu.

0.405 Ω
0.605 Ω
0.305 Ω
0.805 Ω

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MGVCL Exam Paper (30-07-2021 Shift 1)
A coil having an inductance of 100 mH is magnetically coupled to another coil having an inductance of 900 mH. The coefficient of coupling between the coils is 0.45. Calculate the equivalent inductance if the two coils are connected in series aiding.

932 mH
1270 mH
1135 mH
730 mH

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