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Physics, Techniques and Procedures

Three-phase alternating current

way of providing electrical power as alternating current AC . AC is usually provided either as a single phase or as a three phase alternating current, supplied to buildings and to heavy-duty electrical equipment. When present the fourth, or neutral, wire is maintained at ground potential. The power source provides a sinusoidally-varying potential on each of the three wires with respect to the neutral wire. Voltages on these three wires have the same amplitudes and frequencies, however, each is a third of a cycle out of phase with respect to the other two. Since each cycle represents 360 of sinusoidal variation, each of the three phases is 120 shifted with respect to the others. Alternating current is produced by electrical generators.

DT