Three Phase

Three phase is a common method of electric power transmission. It is a type of system used to power motors and many other devices. Three phase systems may or may not have a neutral wire. A neutral wire allows the three phase system to use a higher voltage while still supporting lower voltage single phase appliances. In high voltage distribution situations it is common not to have a neutral wire as the loads can simply be connected between phases – phase-to-phase connection. Three phase has properties that make it very desirable in electric power systems. Firstly, the phase currents tend to cancel one another (summing to zero in the case of a linear balanced load). This makes it possible to eliminate the neutral conductor on some lines. Secondly, power transfer into a linear balanced load is constant, which helps to reduce generator and motor vibrations. Finally, three-phase systems can produce a magnetic field that rotates in a specified direction, which simplifies the design of electric motors. Three is the lowest phase order to exhibit all of these properties. Most domestic loads are single phase. Generally, three phase power either does not enter domestic houses at all, or where it does, it is split out at the main distribution board. The three phases are typically indicated by colors which vary by country.