Q:

# What Is the Difference Between Single-Phase and Three-Phase Power?

A:

Single-phase power propagates as a single waveform, with intermittent peaks in power occurring at regular intervals, while three-phase power propagates as three distinct waveforms, with intermittent peaks in power occurring at equidistant intervals such that peaks occur three times as frequently as in the single-phase counterpart. Power is a function of voltage and current.

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Voltage is the driving force behind alternating current. Voltage varies in amplitude over time in a regular pattern, forming peaks at the points where the power is highest and troughs where the power is lowest. The distance between two peaks is called the wavelength, and the transition from one peak to the next peak is called a cycle. A cycle consists of a turn of 360 degrees. Three-phase power consists of three distinct cycles, carried along three separate wires, with peaks that are 120 degrees apart, each with the same wavelength as its single-phase counterpart.

Most homes use single-phase power because it is efficient, economical and safe when used to power devices typically found in homes, such as small motors and low-power light sources. Industries commonly use three-phase power for more power-hungry applications such as large motors, high numbers of bright lights or large banks of computers.