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.
Three-Phase Power. This article was intended to give non-electrical engineers a basic understanding of three-phase power and its application in AC motors. If you have any questions, feel free to post them in the comments below.
Three-phase electricity is a smoother form of power than single or two-phase systems allowing machines to run more efficiently and extending their lifetime. 220 – 240 VAC single phase supplies are derived from 400 VAC three phase systems and 100-127 VAC single phase supplies from 200 VAC three phase systems.
Most AC power today is produced and distributed as three-phase power where three sinusoidal voltages are generated out of phase with each other. With single-phase AC power there is only one single sinusoidal voltage. Real Power. Line to line voltage: W applied = 3 1/2 U ll I cos Φ = 3 1/2 U ll I PF (1) where. W applied = real power (W, watts)
The three conductors are away from phase & space 120º distant from each other. Three phase power supplies are utilized as a single-phase AC power supply. For the small load, 1-phase AC power supply, as well as neutral, can be chosen from the 3-phase AC power supply system. This supply is constant and not at all totally falls to zero.
Three-phase AC power is the more common form of electrical power generation, transmission, and distribution, simply because the 3-phase power envelope (again, Figure 4) never goes through a zero power transition as each of the three contained single-phase AC sources do.
In a three-phase AC power distribution circuit, three single-phase AC sources are interconnected in either a wye or delta configuration to form a 3-wire supply in the alternator, transformer, or electric motor, and sometimes a 4-wire supply in the alternator or transformer.
Dual Phase or Split Phase power is also Single Phase because it’s a two wire Alternating Current (AC ) power circuit. In the US, this is the standard household power arrangement with two (Phase A, Phase B) 120V power wires (180 degrees out of phase with one another) like two bicycle pedals and one neutral wire.
In 3-phase power, at any given moment one of the three phases is nearing a peak. High-power 3-phase motors (used in industrial applications) and things like 3-phase welding equipment therefore have even power output. Four phases would not significantly improve things but would add a fourth wire, so 3-phase is the natural settling point.
Although single-phase electricity is used to supply common domestic and office electrical appliances, three-phase alternating current (ac) systems are almost universally used to distribute electrical power and to supply electricity directly to higher power equipment.