Questions and answers for exam Preparation

MCQs

Total Questions : 631 | Page 61 of 64 pages

Question 601. 5. A 3-phase Y/A transformer has per phase turn ratio 'K' and line voltage ratio `K1'. If the voltage of A winding lags the voltage of Y winding by an angle 4), then K, K1 and (pare related as

K1 = K and 4) = -30?
K1 = ?17 and = -30?
K1 = %R. K and (1) = -30?
K1 = JK and (1) = -30?

Discuss Question

Answer: Option B. -> K1 = ?17 and = -30?

Question 602. 9. 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

1000 V
80 V
3464 V
803 V

Discuss Question

Answer: Option C. -> 3464 V

Question 603. 1. 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?

500 V
400 V
300 V
100 V

Discuss Question

Answer: Option C. -> 300 V

Question 604. 0. 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

V/60?
V/180?
V/-180?
V/-60?

Discuss Question

Answer: Option D. -> V/-60?

Question 605. 2. 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

be proportionate to their percentage impedances
be independent of their percentage impedances
be inversely proportional to their respective impedances
depend on the resistance to leakage reactance ratio of each transformer

Discuss Question

Answer: Option C. -> be inversely proportional to their respective impedances

Question 606. 6. 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

1000 V
80 V
3464 V
803 V

Discuss Question

Answer: Option C. -> 3464 V

Question 607. 9. 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

be proportionate to their percentage impedances
be independent of their percentage impedances
be inversely proportional to their respective impedances
depend on the resistance to leakage reactance ratio of each transformer

Discuss Question

Answer: Option C. -> be inversely proportional to their respective impedances

Question 608. 8. 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?

500 V
400 V
300 V
100 V

Discuss Question

Answer: Option C. -> 300 V

Question 609. 7. 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