Three-phase voltage refers to three voltages that vary by 120 electrical degrees or one third of a cycle from one another. These voltages apply to alternating current circuits.
The three-phase voltage goes through a phase sequence or peak in a regular order. It can be obtained by using six wires with two wires specially for each phase. But, normally, three wires are used to supply three-phase voltages. Each phase voltage is from one of the three possible pairing of three wires, and four wires sometimes are used for generating three-phase voltages. The additional wire is used as a grounding or neutral wire. Three-phase voltages are shown in effective or rms values.