How to Wire a Three-Phase Plug

Written by hannah ardeb | 13/05/2017
How to Wire a Three-Phase Plug
Three phase plugs have five holes instead of the standard three (Jupiterimages/ Images)

A normal household current is an alternating current (AC). Alternating current means that the voltage in the wiring changes 50 to 60 times a minute. Since the voltage is not a constant, the load that is attached to the power supply has to be able to deal with an alternating current. Three-phase power allows for smoother and higher performance by attaching the load to three currents out of phase of one another to allow the load to see one relatively nonfluctuating current.

Open up the three-phase plug using a screwdriver. When you have the plug open, look for any inscriptions in the socket. There should be five slots inside the plug corresponding to the five wires you will be attaching. These slots should be labelled "1," "2," "3" and "0," with one exhibiting a picture of a line on top of a T shape.

Strip the wires you will be placing in the plug. Stripping involves using the knifelike portion of a pair of electrical pliers to lightly clamp down on the wire about 1/4 inch from the end of the wire. Clamp down until the pliers have cut through the insulation, or the plastic portion covering the metal centre, and twist the pliers making sure not to press too hard so as to cut the metal centre of the wire. After you have cut the insulation, pull it off by using the pliers to clamp down on the freed insulation. Pull it free from the wire.

Insert the stripped wires into the sockets in the plug as follows: black in 1, or L1; red in 2, or L2; blue in 2, or L2; white in 0; and green in the picture with the line and T symbol. Note that these colours may only apply in the US.

Tighten the wires into the sockets using a screwdriver and the screws located on top of the sockets. Close the plug using the same screws that you used to open the plug. Before you use the plug, make sure that there are no loose wires sticking out and that the whole plug is tightly held in place.


Electricity can be lethal. Make sure that no loose wires are exposed before plugging any electrical device.

Tips and warnings

  • Electricity can be lethal. Make sure that no loose wires are exposed before plugging any electrical device.

Things you need

  • Screwdriver
  • Three-phase plug
  • Electrical pliers

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