A three-phase circuit is a polyphase system that uses more than one phase of electricity to generate, transmit and distribute power. It is the most common system used in electricity grids worldwide.
Three-phase circuitry comes in two configurations: Delta and Wye. Delta circuits use three wires, whereas Wye setups use an additional neutral wire that is typically grounded. In three-phase circuit systems, three conductors carry alternating currents of identical frequencies and voltage amplitudes, all with a common reference. When the load is balanced and linear, the currents cancel each other out and the sum is zero. This system can produce a rotating magnetic field, which makes the design simpler.
The three-phase circuit is commonly used in groups of domestic properties, but most commercial buildings and industrial facilities use three-phase four-wire configurations because of their flexibility and power density. Using this arrangement reduces electrical construction and energy costs by lowering the amount of energy converted to heat. It also reduces generator and motor vibrations.
A balanced system produces voltages of equal magnitudes, whereas unbalanced loads result in significant power loss and use the transformer capacity ineffectively. Three-phase configurations are generally more economical than single- or two-phase systems, as they transmit power using less conductor material.