Wye vs delta: what it means for the Texas exam

Bonding Jumper editorial teamSources checked 26 Oct 20263 min read

Wye and delta are the two ways to connect the three windings of a three-phase transformer or motor. In a wye, one end of each winding meets at a common center point, which can serve as a neutral. In a delta, the windings form a closed triangle with the lines at the corners, so there is no natural center point.

Two diagrams side by side: a Y shape with three windings meeting at a center labeled neutral, with phase voltage 120 and line voltage 208 marked, and a triangle of three windings with lines at the corners, line voltage 240 marked and a center tap on one side marked for the high-leg system — Wye: a shared center and two voltages. Delta: a closed loop, line voltage across each winding.

Voltages and currents

Wye. Each winding sits between a line and the neutral, so the phase voltage is line to neutral. The line-to-line voltage is 1.732 times the phase voltage: 120 × 1.732 is about 208, and 277 × 1.732 is about 480. The line current equals the winding current. That is why a 208Y/120 or 480Y/277 system gives two voltages, one for lighting and receptacles and one for motors.

Delta. Each winding sits directly between two lines, so the line voltage equals the winding voltage. The line current is 1.732 times the winding current, because each line is fed by two windings. A plain delta has no neutral.

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The high-leg delta

A common older service is a 240-volt delta with one winding center-tapped to make a neutral, giving 120/240 volts for single-phase loads from two of the phases. The third phase, measured to that neutral, reads about 208 volts. It is the high leg, sometimes called the wild leg. The NEC requires it to be identified, by an orange finish or another effective marking, and it cannot serve 120-volt loads. Panel position rules apply to it too; find them in your own 2026 NEC.

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Where each shows up

Wye is the usual building distribution system, because the neutral serves single-phase loads and makes grounding straightforward.
Delta is common on transformer primaries, on some industrial systems and in motors. A delta-wye transformer, with a delta primary and a wye secondary, is a standard way to create a 208Y/120 system from a 480-volt supply.

Common mix-ups

Using 1.732 in the wrong place. In a wye it relates voltages; in a delta it relates currents.
Connecting 120-volt loads to the high leg. The high leg to neutral is about 208 volts.
Thinking a delta cannot be grounded. It can be, at a corner or a center tap; it simply has no natural neutral.
Mixing up phase and line values in a formula. The three-phase power formula uses line voltage and line current. See single-phase vs three-phase.

On the Texas journeyman exam

System connections sit in definitions, theory and plans and in the services and separately derived systems area, which together carry 15 scored items across both portions under the PSI bulletin. Study to find a voltage or current in either connection and to recognise a high-leg system.

Practice it

The transformer calculator works three-phase kVA to amperes on each side. See transformer kVA for the rating itself. Every term in this set is in the electrical terms glossary.

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Not affiliated with or endorsed by TDLR, PSI or NFPA. NEC and National Electrical Code are registered trademarks of NFPA.

Sources

Show the list

Candidate Information Bulletin, Texas electricians (updated 9/15/2026), PSI for the Texas Department of Licensing and Regulation.
NFPA 70, National Electrical Code (2026 edition), NFPA. Free read-only access with an account.

Facts checked 26 October 2026 against the sources listed above. If something has changed, tell us and we will correct it within 2 business days.

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