Three Phase (3 Phase) Electrical Power Explained

Summary: There are lots of electrical distribution systems out there. This article describes how one of these works.

Three-phase power is a popular method of electric power transmission and a common form of power. This is because of its inherent benefits for high power transmission along with a smooth wave form quality that allows electrical equipment such as three phase transformers and transformer rectifier units to last longer and run smoothly.

The Benefits

There are a number of benefits when inductors and other electrical equipment have three-phased power. It gives all three wires the capability to carry the same current. Another benefit is that power transfer is constant in a balanced and linear load.

Most power that domestic utility and single phase transformers supply are in one phase only. In many cases, three phase power is not available from a utility company to rural businesses, farms, and houses at all. In rare cases, it is separated at the main distribution board.

Aside from that, the three phase power that is created today has closer voltage tolerances making it better balanced. Unlike utility supplied power, it has a smoother wave form. For this simple reason, three phase power output from a three phase generator is preferred for use in sensitive equipment

Three Phase Power Generation

An electrical generator at a utility station converts a set of alternating electrical current with a DC to AC inverter using mechanical power. The currents all at the same frequency are sinusoidal functions of time. In a three power system such as a generator, all phases are spaced equally.

The Wiring color Coding

The three phases are usually indicated through colors in electrical diagrams. Conductors on a generator are typically marked by a color code. This is to ensure the right phase rotation for and balance loading for three phase inductors. Colors used differ widely and may follow no standards.

They can even vary within an installation. The National Electric Code of 2005 does not mandate color identification of inductors aside from neutral, ground, and, in case of High Leg Delta Systems, an orange color should be used to identify the High Leg

Power Transmission and Distribution

After numerous further changes in the distribution and transfer network, three phase power is transformed to the standard main voltage. The power may already be split into a single phase at this point, or it may still be three phase power. The output of a three phase transformer where the step down is three phase is usually connected with the standard main voltage.

Another system commonly used in the U.S. is to connect a three phase transformer to a delta secondary with a center tap located on one of its windings supplying the neutral and ground. This allows for three different single phase voltage from as well as 240V three phase to be made available from the same supply.


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John Lawton creates guides about different power systems to help people understand how these technologies benefit their everyday lives. He also writes about the equipment that makes it possible. For more information about this equipment visit http://abbott-tech.com/

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Created on Dec 31st 1969 18:00. Viewed 0 times.

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