A common method of alternating current electric power transmission is called a 3 phase electric power. This is used by electric power distribution grids all over the world to distribute power. It is also used to power large motors and other large loads.

A 3 phase motor system is generally more economical than others because it uses less conductor material to transmit electric power than the equivalent single phase or two phase systems at the same voltage. In a 3 phase system, there are three circuit conductors carrying 3 alternating currents of the same frequency. These 3 reach their instantaneous peak values at different times. The delay between phases results to the transmission of constant power over each cycle of the current.