Two-phase electric power

As a two -phase alternating current, also two-phase system, in electrical engineering, a special form is referred to by two fixed temporally concatenated AC currents and AC voltages. As the three-phase alternating current is also the two-phase alternating current a form of polyphase alternating current, but plays only a minor role in the electric power industry.

In the two- phase system - it is an asymmetric two-phase system, which is composed of a four-phase system by omitting two phases - the two sinusoidal waveform, phase-shifted by 90 °, as sketched in the adjacent figure. Thereby, a rotating field will be produced and therefore of electrical machines, such as the two-phase synchronous motor can be driven directly. However, at least three conductors for electric power transmission as in the three-phase system is required to be loaded to different degrees. This results in the two-phase system a worse utilization of available conductor cross-sections.

A two-phase alternating current can be extracted from the three-phase AC by means of the Scott connection. Other possibilities are, especially for the control of two-phase synchronous motors, electronic inverter.

Most stepping motors can be viewed as a two- phase engines.

The widespread especially in North America single-phase three-wire system for public electricity supply and is sometimes incorrectly referred to as two-phase system, although it is a single-phase system in the base installation.

Literature sources

• Terrell Croft, Wilford Summers (ed ): American Electricians ' Handbook. 11th edition. McGraw Hill, New York 1987, ISBN 0-07013932-6, pp. 3-10, Figure 3-23.