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MCQs 1: While connecting three phase transformer in star-star connection, the terminals of secondaries are wrongly joined. Then the mutual phase angle and magnitude of line to line voltages of secondaries will

Equal to 120 degree and equal as before Not equal to 120 degree and different Equal to 120 degree and different None of these
Answer Explanation

MCQs 2: For the parallel operation of three phase transformers, which among the following connection is not applicable?

Δ - Δ to Y – Y Y - Δ to Δ - Y Y - Y to Y – Y None of these
Answer Explanation

MCQs 3: Due to presence of third harmonic component in the star-star connection of three phase transformer, the frequency of the circuit component becomes

Three times of the circuit frequency One third of the circuit frequency Remains same None of these
Answer Explanation

MCQs 4: The phase shift in a star-star connected three phase transformer is

0 degree 30 degree 60 degree 120 degree
Answer Explanation

MCQs 5: If K is the transformation ratio, then the secondary phase voltage of delta-delta connected three phase transformer will be

1 / K times of the primary phase voltage Equal to the primary phase voltage 1 / K ∧ 2 times of the primary phase voltage K times the primary phase voltage
Answer Explanation

MCQs 6: For large low voltage transformers, the most commonly used connections are

Star - star connection Delta - delta connection V connection All of these
Answer Explanation

MCQs 7: In case of delta-star connection of three phase transformer, secondary line voltage with respect of primary line voltage is at

0 degree 30 degree leading 30 degree lagging 60 degree lagging
Answer Explanation

MCQs 8: The most commonly used connections for power systems as a step - up and step - down transformers are

Star - delta, star - star Delta - star, star - delta Star - star, delta - delta Star - delta, delta - star
Answer Explanation

MCQs 9: The load carried by V - V connection is

47.7% of the original load 57.7% of the original load 67.7% of the original load 87.7% of the original load
Answer Explanation

MCQs 10: Consider three transformers connected in delta-delta fashion and supplying their rated load. Now if one of the transformer is removed then each of the remaining two transformer is overloaded. The overload on each transformer is given as

1 1.232 1.732 1.872
Answer Explanation

MCQs 11: The average power factor at which V-V bank is operating is less than that with the load. The power factor is

57.7% of the balanced load power factor 66.7% of the balanced load power factor 86.6% of the balanced load power factor None of theses
Answer Explanation

MCQs 12: With a bank of two single phase transformers connected in V - V fashion supplying a balanced three phase load with Cosφ as power factor. The power factor of the two transformers is given by

Cosφ , Cosφ Cosφ, Cos(30+φ) Cos(30-φ), Cos(30+φ) Cos(30-φ), Cosφ
Answer Explanation

MCQs 13: In T-T connection, the percentage tapping of main transformer and teaser transformer are

50%, 86.6% 50%, 50% 86.6%, 86.6% 86.6%, 50%
Answer Explanation

MCQs 14: In T-T connection, the ratio of actual capacity to the available capacity is

1 0.928 1.928 0.5
Answer Explanation

MCQs 15: Scott connection is used for the conversion of

Single phase to three phase Three phase to single phase Single phase to two phase All of these
Answer Explanation

MCQs 16: In Scott connection, the voltage across the teaser leads the mains by

30 degree 60 degree 90 degree 120 degree
Answer Explanation

MCQs 17: In a single phase, full wave bridge circuit and in three phase, delta full wave bridge circuit, the ripple voltage frequency is always

Twice the line frequency, six times the line frequency Both will be twice the line frequency Both will be six times the lines frequency None of these
Answer Explanation

MCQs 18: Most familiar application of zig - zag transformer is as

Ground reference on an ungrounded system Converting single phase to two phase Reducing harmonics All of these
Answer Explanation

MCQs 19: In double delta transformation, a double delta refers to the case where there are two delta transformations in

Parallel Series Both series and parallel Neither series nor parallel
Answer Explanation

MCQs 20: A differential relay comparator used for the protection of three phase transformers has

One comparator Two comparator Three comparator Six comparator
Answer Explanation

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