15. Two transformers A and B having equal outputs and voltage ratios but unequal percentage impedances of a 4 and 2 are operating in parallel. Transformer A will be running overload by ?percent.
16. Which of the following parallel combination is not possible for three-tothree phase transformer connection?
A. Y ? Y to ? A
B. Y ? to ? A
C. Y ? to ? Y
D. Y ? Y to Y ? Y
17. Which of the following three-to-three phase transformer connections are possible for parallel operation?
A. Y ? Y to ? Y
B. ? Y to Y ? A
C. A ? Y to ? Y
D. A ? to ? Y
18. If three transformers in A ? A are delivering rated load and one trans former is removed, then overload on each of the remaining transformers is ? precent.
19. A T-T connection has higher ratio of utilization than a V-V connection only when
A. identical transformers are used
B. load power factor is leading
C. load power factor is unity
D. non-identical transformers are used
20. For 3-to-3 phase conversion, which of the following given polyphase connections would you select?
21. When two identical transformers are available, then the best method to find their efficiency under load conditions is the test.
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