MULTIPLE CHOICE QUESTIONS
Q.1 Which of the following connections is best suited for 3-phase, 4-wire service ?
(A) Δ − Δ
(B) Y − Y
(C) Δ − Y
(D) Y − Δ
Q.2 In a three-phase Y-Y transformer connection, neutral is fundamental to the
(A) suppression of harmonics
(B) passage of unbalanced currents due to unbalanced loads
(C) provision of dual electric service
(D) balancing of phase voltages with respect to line voltages.
Q.3 As compared to Δ − Δ bank, the capacity of the V − V bank of transformers is ......... percent.
(A) 57.7
(B) 66.7
(C) 50
(D) 86.6
Q.4 If three transformers in a Δ − Δ are delivering their rated load and one transformer is removed, then overload on each of the remaining transformers is ......... percent.
(A) 66.7
(B) 173.2
(C) 73.2
(D) 58
Q.5 When a V − V system is converted into a Δ − Δ system, increase in capacity of the system is ......... percent.
(A) 86.6
(B) 66.7
(C) 73.2
(D) 50
Q.6 For supplying a balanced 3 − φ load of 40-kVA, rating of each transformer in V − V bank should be nearly ......... kVA.
(A) 20
(B) 23
(C) 34.6
(D) 25
Q.7 When a closed − Δ bank is converted into an open − Δ bank, each of the two remaining transformers supplies ......... percent of the original load.
(A) 66.7
(B) 57.7
(C) 50
(D) 73.2
Q.8 If the load p.f. is 0.866, then the average p.f. of the V – V bank is
(A) 0.886
(B) 0.75
(C) 0.51
(D) 0.65
Q.9 A T − T connection has higher ratio of utilization that 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.
Q.10 The biggest advantage of T - T connection over the V - V connection for 3-phase power transformation is that it provides
(A) a set of balanced voltages under load
(B) a true 3-phase, 4-wire system
(C) a higher ratio of utilization
(D) more voltages.
