Three-Phase Power

Three-Phase Generator

"Three-phase Power" is designed especially for large electrical loads where the total electrical load is divided among the three separate "phases." As a result, the Wire and Transformers will be less expensive than if these large loads were carried on a single-phase system.

Three-phase Generators usually have three separate "windings," each producing their own separate single-phase voltage. Since these "windings" are staggered around the Generator circumference, each of the single-phase voltages is "out of phase" with one another.

Three-Phase Power Sine Wave Pattern

That is, each of the three reaches the maximum and minimum points in the AC cycle at different times.

Electricity is generated at Power Companies in these three phases. But, if three-phase power is better than single-phase, why not four-, five- or six-phase? Theoretically, these would be even better, but equipment manufacturers would have to build Motors to use it; and that just would not be cost-effective (given the installed base of Three-phase Equipment that must continue to be powered).

The word "phase" is often abbreviated using the Greek letter "phi" and is written as a "zero" with a slash mark through it (φ ).

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