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As well being the most efficient way to distribute power over long distances, three-phase power also enables industrial equipment to operate more efficiently. Three-phase power is characterised by three single-phase waves that are offset in their phase angle by 120 degrees, or one third of the sine wave period (see Figure 1 below).
Three-phase voltage can be measured from each phase to neutral or from one phase to any other. The voltage relation between phase to neutral and phase to phase is a factor of square root of three (e.g.230V versus 400V).
Conversely, single-phase power is distributed through household outlets to power everyday equipment such as laptops, lighting andtelevisions. As shown in Figure 2, if you were to look at the voltage coming from a single-phase outlet on an oscilloscope, you would see a single wave. This is because single-phase power is obtained by simply using one phase of a three-phase system. Its RMS voltage is 230V and it oscillates at 50 Hz (or 50 times a second).
