Two-phase electric power

In the early days of electrical engineering, it was easier to analyze and design two-phase systems where the phases were completely separated.

[4] It was not until the invention of the method of symmetrical components in 1918 that polyphase power systems had a convenient mathematical tool for describing unbalanced load cases.

Two-phase circuits also have the advantage of constant combined power into an ideal load, whereas power in a single-phase circuit pulsates at twice the line frequency due to the zero crossings of voltage and current.

Two-phase circuits typically use two separate pairs of current-carrying conductors.

The vector sum of balanced three-phase currents, however, is zero, allowing for the neutral wires to be eliminated.