Before exploring single-phase and three-phase power, it's helpful to understand exactly what a phase it is. Generally, in electrical terms a phase is the voltage between an existing wire and a neutral wire. Phases are defined by the electrical load distribution in relation to the type of unit, either a single or three-phase system.
Single-phase power is the most basic type of electrical power that involves a single alternating current (AC) waveform, typically with one power wire (the phase wire) and one neutral wire, with flowing currents between the power wire and the other way on the neutral wire.
Whilst it is often considered basic compared to three-phase power, single-phase power is indispensable in many settings. It is commonly used in residential and small business settings where power demand is relatively low, while larger industries and data centers use a three-phase supply.
Single-phase power usually runs at 120V or 240V, with a standard frequency of 50Hz in other countries and 60Hz in the US.