High Quality Content by WIKIPEDIA articles! Three-phase electric power is a common method of alternating-current electric power generation, transmission, and distribution. It is a type of polyphase system and is the most common method used by electrical grids worldwide to transfer power. It is also used to power large motors and other heavy loads. A three-phase system is generally more economical because it uses less conductor material to transmit electrical power than equivalent single-phase or two-phase systems at the same voltage. The three-phase system was invented by Galileo Ferraris and Nikola Tesla in 1887 and 1888.