How to connect 3 phase power

Written by eric w. thompson
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How to connect 3 phase power
Three-phase electrical systems use three power leads instead of the one power lead used in residential systems. (electrical panel switch image by jimcox40 from

Electrical systems in industrial manufacturing facilities require three-phase power systems to distribute high voltage current to motors and machines rated for high voltage. The multiple phases in the three-phase system provides a continuous flow of alternating current unavailable in single-phase systems. Connecting three-phase power to industrial motors requires a breaker specifically rated for three-phase systems. While conventional breakers are able to receive only one lead, these special breakers are able to accommodate the three power leads used in three-phase systems.

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Things you need

  • Ratchet and socket
  • Flathead screwdriver
  • Megger
  • Wire strippers
  • Padlock

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  1. 1

    Remove power from the main breaker panel by shutting the main breaker off. Lock the breaker closed as a precaution.

  2. 2

    Open the panel and insert the three-phase breaker. Secure the breaker in place using a flathead screwdriver.

  3. 3

    Set out four lengths of wires. Three wires are power leads, and one wire is for grounding. Run the grounding wire from the breaker box grounding screw to the grounding screw on the electrical device. Run the three leads from the breaker to the electrical device.

  4. 4

    Strip the ends of the wires with wire strippers, and terminate them at their points using a flathead screwdriver. One end of the power leads will insert into the three holes in the breaker, and the other end will insert to inputs L1, L2 and L3 on the electrical device.

  5. 5

    Run a megger test on the circuit, then restore power and test the electrical device.

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