Wye and delta

Wye and delta are the two ways to connect a three-phase set of windings. Wye ties one end of each winding together at a common point — which can give you a neutral. Delta connects them end to end in a closed loop, with no neutral coming from the windings themselves.

The shapes, and what follows from them

Picture three windings. Join one end of all three at a single node and fan the other ends out, and you have drawn a Y — that shared node is the neutral, and the fanned ends are the three lines. Now instead connect the end of the first winding to the start of the second, the second to the third, and the third back to the first, and you have drawn a closed triangle — a delta, with a line taken off each corner and no common node anywhere.

Those shapes decide the voltage and current relationships. In a wye the line current is the same as the current in a winding, but the voltage between two lines is √3 (about 1.732) times the voltage from a line to the neutral. In a delta it flips: the line voltage equals the winding voltage, and the line current is √3 times the current in a winding. Knowing which connection you are looking at tells you which of those relationships to use — get the connection wrong and every calculation downstream is off by that √3.

Questions people ask

What is the difference between wye and delta?

They are two ways to connect three windings. Wye joins one end of each winding at a shared point, which can give a neutral. Delta connects the windings end to end in a closed loop, with no neutral coming from the windings themselves.

Why does wye give a neutral and delta does not?

Because the shared point in a wye is the neutral — three windings meeting at one node create it naturally. A delta is a closed triangle with no common node, so there is nowhere for a winding-derived neutral to be.

How do line and phase values differ?

In a wye, the line current equals the phase current, but the line-to-line voltage is √3 times the line-to-neutral voltage. In a delta it is the mirror image: line voltage equals phase voltage, and line current is √3 times the phase current. Which relationship applies changes your maths.

Power factor
Phase formulas sheet — the √3 in the three-phase equations.
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