A wye-delta transformer has a turns ratio of 2:1. It has a secondary line voltage of 480 V. The secondary is connected to a wye-connected three-phase resistive load of 50 Ω in each phase. What is the primary line current?
A) 1.6 A
B) 1.924 A
C) 2.77 A
D) 3.2 A

Question

Quizplus · Accepted Answer

The turns ratio of 2:1 means that the primary voltage is twice the secondary voltage. Therefore, the primary line voltage is 480 V * 2 = 960 V. The secondary line current is 480 V / 50 Ω = 9.6 A. The primary line current is the secondary line current divided by the turns ratio, which is 9.6 A / 2 = 4.8 A.

A Wye-Delta Transformer Has a Turns Ratio of 2:1