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Electrical Engineering Objective Questions { Transformers }

309. Three units of 1:5 transformers are connected in A-Y to supply a 3-phase load from a 400 V, 3-phase source. The line voltage on the load side is
A. 1000 V
B. 80 V
C. 3464 V
D. 803 V
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310.  A normal A ? A connected 3 phase transformer is obtained by Pnnnecting three single-phase transformers I, II and III as shown above.If transformer III is removed, the system, would now operate in"open-delta" mode. Under this condition, if voltage Vab is designated byV/60?, the voltage Vca is
A. V/60?
B. V/180?
C. V/-180?
D. V/-60?
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311.  A single-phase two-winding transformer shown above in Fig. 8.8, is connected as an autotransformer shown in Fig. 8.9. If the connections of the 100 V winding are reversed as shown in Fig. 8.10, what is the value of the voltage Vi required to be applied across terminals X2 and H2 to obtain the same 400 V output?
A. 500 V
B. 400 V
C. 300 V
D. 100 V
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312.  Two transformers with identical voltage ratings are working in parallel to supply a common load. The percentage impedance of one transformer is higher compared to that of the other. The load sharing between the two transformerswill
A. be proportionate to their percentage impedances
B. be independent of their percentage impedances
C. be inversely proportional to their respective impedances
D. depend on the resistance to leakage reactance ratio of each transformer
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