A wye-delta transformer has a primary line voltage of 7200 V and a secondary line voltage of 480 V. What is the turns ratio?

A) 8.66:1
B) 9: 66
C) 10:15
D) 15:1

The turns ratio of a transformer is determined by the ratio of the primary voltage to the secondary voltage. For a wye-delta transformer, the primary and secondary line voltages are used to calculate this ratio. Given a primary line voltage of 7200 V and a secondary line voltage of 480 V, the turns ratio is 7200/480 = 15:1. However, because the question involves a wye-delta transformer, we must adjust this ratio to account for the √3 factor that comes into play due to the configuration difference. The correct calculation is (7200/√3) / (480) = 2400 / 480 = 5:1. This appears to be a misunderstanding in the explanation provided, as the calculation provided does not match any of the given options directly, and the correct interpretation should involve understanding the relationship between line and phase voltages in wye and delta configurations. The correct answer, based on the options provided and typical understanding of transformer turns ratios, should be derived from the direct line voltage ratio, which was initially calculated as 15:1. However, none of the options directly reflect the correct calculation for a wye-delta transformer considering the standard approach. Given the options and typical calculations, there seems to be a mistake in the explanation process. The closest correct approach based on standard calculations without considering the √3 factor adjustment (which was incorrectly applied here) would lead to recognizing the direct ratio of 7200 to 480, aiming for an answer that reflects the relationship between these two voltages. The confusion arises from the incorrect application of the √3 factor in this context. The correct answer choice intended might be a misunderstanding in the explanation process, as none of the options directly match the typical calculation for a wye-delta transformer's turns ratio based on the provided voltages.