Three Phase Basics

Written By Ted " Smitty" Smith  November 2003

The basic concept of three-phase power is to generate three separate sources of current with one machine and do it so that the current is not produced at the exact same time. 

A three-phase generator has three armatures in the magnetic field instead of one. The armatures are placed in the magnetic field 120 degrees apart. This makes them evenly spaced. Each one of the armatures produces a voltage a current as a single armature does in a single-phase system. 
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This power generation system allows for power to be produced efficiently. Looking at the sine wave graph below, you will see that the sine waves are evenly spaced 120 degrees apart and further that one sine wave is always at a peak value. This allows for the most efficient production and use of power.



Three-phase alternating current, electrical power is commonly used in all commercial and industrial applications. It is a highly efficient method of delivering large amounts of power using lower levels of current. It also allows us to place large electrical demands onto the grid with relative small infrasturcuture wire. 

It is also very confusing at times. We have developed this page to help you to understand the basics of three-phase power. 

Let's begin with the purpose of three phase-power. Imagine a wheel made out of stone. The wheel weighs 300 lbs. It has a single handle, 12 inches long, protruding from it. This handle is used to turn the wheel. You can imagine that it would require someone of great strength to turn the wheel. Now imagine what could be done to make the job of turning the wheel easier.


One way to make the job easier would be to use the law of physics and leverage. We could lengthen the handle and then it would be easier to turn the wheel. 

Another method of making the job easier would be to get some help from our friends. We could add two more equally long handles and have two of our friends help us turn the wheel. 

You can see that either method will make the job much easier. 

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