What is three phase power?

A three-phase (3-phase) supply carries power on three live conductors (L1, L2, and L3), plus a neutral and an earth. The alternating current on each conductor is 120 degrees out of phase with the other two, so at any moment at least one phase is near its peak, and the power delivered never drops to zero. In the UK, each phase is 230V to neutral, and the voltage between any two phases is 400V, both at 50Hz. Three-phase is the standard supply for data centres, large commercial buildings, and industrial sites. Smaller offices and homes normally have a single-phase 230 V supply.