Three Phase Circuit Wye and Delta Basics

3 Phase WYE (Y)

A 3 Phase-Wye connected system consists of three hot lines, or phases, commonly referred to as X, Y, Z, a neutral, and a ground wire for a total of five wires in a power distribution cable.

In North America the most common 3 Phase-Y voltages are either 120/208 VAC or 277/480 VAC, while internationally the most common 3 Phase voltage is 230/400 VAC. The lower voltage in each case is the country’s standard utilization voltage and is measured Line-to-Neutral, while the higher voltage is measured Line-to-Line. The Line-to-Line voltage is always 1.732 times higher than the Line-to-Neutral voltage in a Wye configured 3 Phase system.

The line current supplied to the load is also the same as the phase current. It is important to note that when all three “Hot” phases of the system are loaded equally, the net current draw in the neutral line is zero!

3 Phase Delta (Δ)

A 3 Phase-Delta connected system consists of three hot lines, commonly referred to as X, Y, Z, and a ground wire for a total of four wires in a power distribution cable.

In North America the most common 3 Phase-Δ voltages are either 208VAC or 240VAC, while internationally the most common 3 Phase voltage is 230 VAC. These phase voltages are measured Line-to-Line and are typically the country’s standard utilization voltage.

Since there is no neutral line in a Delta-connected system, there is no Line-to-Neutral voltage! However, the line current in a Delta-connected system is 1.732 times the phase current supplied to the load(s).

Proper care must be taken to correctly size cables in a Delta system because the line currents are much higher than the load (or phase) currents.

Delta systems typically have lower line voltages but higher line currents than Wye-connected systems.