To determine the 3-phase voltage from your configuration, I need to know more about it. Specifically, I need to understand how the transformer is wired and what the single-phase voltage is feeding the transformer.Here's a breakdown of the possibilities and what I need to know

Common Scenarios and How to Tell the Difference
240V Delta (High-Leg Delta)

This is less common but results in 240V 3-phase.

What to look for

The presence of a "high leg" (also known as a "red leg" or "wild leg"). One phase will have a voltage to ground significantly higher than the other two (around 208V).

208V Wye

This is common in commercial buildings.

How to identify

Measuring the voltage from each phase to ground; it should be roughly 120V. The phase-to-phase voltage will be 208V.

480V/277V Wye

This is less common.

How to identify

Measuring the voltage from each phase to ground; it should be roughly 277V. The phase-to-phase voltage will be 480V.

What I Need to Know for Certain


Primary Voltage

What is the voltage feeding the transformer? (e.g., 240V single-phase, 480V 3phase)2.

Transformer Nameplate

The transformer nameplate should clearly state the secondary voltage. (e.g., 240/120V Delta, 208Y/120V Wye). Even better, a picture of the nameplate.3.

Wiring Diagram

If possible, a wiring diagram of the transformer connections would be incredibly helpful.4.

Voltage Measurements

If you have a multimeter and it is safe to do so, measure: Voltage from each phase to ground. Voltage between each pair of phases (A-B, B-C, C-A).

Without this information, I cannot accurately determine the 3-phase voltage. Please provide more details so I can give you a definitive answer.

Safety Note: Working with electrical systems can be dangerous. If you are not qualified, consult a licensed electrician. Flag for review