267.  Two transformers of identical voltages but of different capacities are operating in parallel. For satisfactory load sharing
A. impedences must be equal
B. per-unit impedences must be equal
C. per-unit impedences and ratios must be equal X
D. impedences and R ratios must be equal

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268.  Supply to one terminal of a delta-wye connected three-phase core type transformer which is on no-load, fails. Assuming magnetic circuit symmetry, voltages on the secondary side will be
A.23,02,30,115
B.23,01,15,115
C.34,51,15,115
D. 345,0,345

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269.  (a) to provide insulation and cooling
A.(b) to provide protection against lightning
B.(c) to provide protection against short circuit
C.(d) to provide lubrication
D.

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270.  Auto-transformer is used in transmission and ditribution
A. when operator is not available
B. when iron losses are to be reduced
C. when efficiency consideration can be ignored
D. when the transformation ratio is small

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271.  The efficiency of a 100 KVA transform is 0.98 at full as well as at half load. For this transformer at full load the copper loss.
A. is less than core loss
B. is equal to core loss
C. is more than core loss
D. none of the above

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272.  The magnetising current in a transformer is rich in
A. 3rd harmonic
B. 5th harmonic
C. 7th harmonic
D. 13th harmonic

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273.  A 10 kVA, 400 V/200V single phase transformer with 10% impedance draws a steady short circuit line current of
A. 50A
B. 150A
C. 250 A
D. 350 A

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