Three-phase power is a method of electrical power transmission that makes use of three wires to deliver three independent alternating electrical currents. The current in each wire is set off from the others by one-third of a complete cycle, with each current representing one phase. This means that a device operating off this type of power source receives a more stable flow of electricity than it would from single-phase distribution system. Some three-phase power systems actually have four wires; the fourth is a neutral wire that allows the system to use a higher voltage.

The three currents, together, deliver a balanced load, something not possible with single-phase alternating current. In alternating current (AC), the current alternates direction, flowing back and forth in the circuit; this means that the voltage alternates as well, constantly changing from maximum to minimum. Three-phase power combines the three wires to off-set the maximum and minimum oscillations, so that a device receiving this type of power does not experience such a wide variation in voltage. This makes three-phase power a very efficient form of electrical power distribution. Consequently, a three-phase electric motor uses less electricity and normally lasts longer than a single-phase motor of the same voltage and rating.