Single Phase Two Wire, Three Wire and Split Phase

Single phase two wire

One hot conductor and one neutral. You get a single voltage, commonly 120 volts, and nothing else. It is what a small service or a single circuit looks like, and it is what most of the world outside North America uses at 230 volts. It cannot give you two voltages because there is only one winding section to draw from.

Single phase three wire, which is split phase

Two hot conductors and a neutral taken from the centre of the secondary winding. That is the standard North American residential service. 240 volts between the two hots, 120 volts from either hot to the neutral. Three wire and split phase describe the same thing, the three wires being the two legs and the neutral.

Two phase is not split phase

A genuine two phase system had two windings 90 degrees apart and was used briefly around 1900 before three phase won. Almost nobody has seen one. When someone says two phase in a modern conversation they nearly always mean split phase, the ordinary 120/240 residential service, where the two legs are 180 degrees apart rather than 90. The distinction matters because a real two phase motor and a split phase motor are different machines.

Which one you have

Count the conductors at the service and read the panel. Two conductors and 120 volts is single phase two wire. Three conductors with 240 between the outer two and 120 to the middle is single phase three wire. Four conductors with 208 or 480 between any two is three phase. The transformer nameplate states it as well, which is the answer that settles arguments.

What does 1 phase 3 wire mean

Two hot conductors and a neutral, with the neutral taken from the centre of the transformer secondary. It gives 240 volts between the hots and 120 volts from either hot to neutral. It is the standard North American residential service and is also called split phase.

What is 1 phase 2 wire

One hot conductor and one neutral, giving a single voltage with no second option. Common for small services and for most of the world outside North America at 230 volts.

Is split phase the same as two phase

No. Split phase has two legs 180 degrees apart taken from one winding with a centre tap. True two phase had two windings 90 degrees apart and was abandoned around 1900. People usually say two phase when they mean split phase.

What are the three wires coming out of a transformer

On a single phase 120/240 volt secondary they are the two hot legs, X1 and X3, and the grounded neutral from the centre tap, X2. On a three phase delta secondary they are the three phases with no neutral.