MGVCL Exam Paper (30-07-2021 Shift 2)
The voltage applied to a transformer primary is increased keeping V/f constant. With this, the core loss ____ and the magnetizing current (Im) ____

increases, remains constant
increases, increases
remains constant, decreases
decreases, increases

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MGVCL Exam Paper (30-07-2021 Shift 2)
In a 3-phase, 4-wire, 400/230 V system, a lamp (L1) of 100 W is connected to one phase and neutral and a lamp (L2) of 150 W is connected to the second pahse and neutral. If the neutral wire is disconnected accidently, then

100 W lamp (L1) becomes dim and 150 W lamp (L2) becomes brighter
100 W lamp (L1) becomes brighter and 150 W lamp (L2) becomes dim
both 100 W lamp (L1) and 150 W lamp (L2) becomes brighter
both 100 W lamp (L1) and 150 W lamp (L2) becomes dim

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MGVCL Exam Paper (30-07-2021 Shift 2)
The line currents in amperes in phases a, b and c respectively are 500 +j150, 100 – j600 and – 300 + j600 referred to the same reference vector with phase sequence of abc. Find the symmetrical component of currents.

Ia₀ = (100+j50) AIa₁ = (200+ j107.75) AIa₂ = (200-j107.75) A
Ia₀ = (100+j50) AIa₁ = (546.41+ j165.47) AIa₂ = (546.41-j165.47) A
Ia₀ = (100+j50) AIa₁ = (146.41+ j65.47) AIa₂ = (546.41-j165.47) A
Ia₀ = (100+j50) AIa₁ = (546.41+j165.47) AIa₂ = (-146.41-j65.47) A

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MGVCL Exam Paper (30-07-2021 Shift 2)
Interposing current-transformer (CT) is used in differential protection of a transformer to

limit the main CT secondary current
increase the sensitivity of the relay
minimize the effect of saturation of the main CTs
match the standard ratio of CTs used on both sides of the transformer winding

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