If a delta-connected secondary of a transformer is delivering a line current of 54 amps, what is the phase current?

In a delta-connected configuration, the relationship between line current and phase current is important to understand. When a three-phase delta connection is used, the line current (the current flowing through the conductors feeding the transformer) is greater than the phase current (the current flowing through each winding of the transformer).

The formula to calculate the phase current from the line current in a delta connection is:

[ I_{phase} = \frac{I_{line}}{\sqrt{3}} ]

This means that to find the phase current, the line current should be divided by the square root of 3 (approximately 1.732).

Given that the line current is 54 amps, you can calculate the phase current as follows:

[ I_{phase} = \frac{54 , \text{amps}}{\sqrt{3}} ]

Calculating this:

[ I_{phase} = \frac{54}{1.732} \approx 31.2 , \text{amps} ]

Thus, the phase current is approximately 31.2 amps, which aligns perfectly with the correct answer. Understanding this relationship is crucial for electrical engineers and contractors, as it impacts calculations related to load, sizing of conductors, and protection