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What's the Difference Between Single Phase and Three Phase Generators?

Posted by: Cooper MechanicalWednesday, June 14, 2017

Last week we looked at some of the reasons why a commercial generator could be critical to keeping your South Carolina business functioning and profiting in the case of major power failure. Hurricane season is upon us and weather experts are forecasting an "above-normal" hurricane season due to the lack of an El Niño system in the Atlantic. 

If you've been looking at generators, you've probably noticed that some are "single phase" and others are "three phase." You've probably also noticed that a "three phase" generator usually comes with a significantly higher price tag. In this post we will offer simplified explanations of single and three phase power along with some things to consider when deciding which is best for you.

Speaking with our resident commercial generator specialist at Cooper Mechanical Services is highly advised. Our team is happy to educate, advise and assist all potential consumers. We will make sure you get the generator that fits your needs, not ours. 

Single Phase Power

In the United States, single phase voltage is 120 volts, and the standard for delivering it is alternating current, commonly referred to as AC power. Single phase systems power comes in through a two wire AC circuit, one wire is the 120 current and the other is neutral. The alternating current flows between the load wire and the neutral wire in a cyclical manner with the current flow changing in magnitude and direction.

This cyclical alternating current can be graphed as a single wave (see image below). The wave actually cycles so fast (about 60 times per second) that fluctuations in voltage is not observable to human senses. This form of power is what we all use in our home or non-industrial workplaces for lights, appliances, and even small motors.

single, split and three phase power wave

Three Phase Power

Three phase power uses a four wire AC circuit with three power wires and one neutral wire. Each of the three power lines are operating slightly "out of phase" with each other (precisely 120 degrees difference, if you are curious). Imagine an engine with three pistons, each pumping at the same capacity, but alternating between the three. 

Three phase power has the advantage of providing more power with the same current as well as guaranteeing that the wave never comes to "zero" (see image above). 

Most industrial workplaces use three phase systems because the power is denser. In a generator system, this is ideal for "power hunger" businesses: grocery stores, hospitals, manufacturing. Additionally, this is necessary for data centers.

Curious About Commercial Generators?

Cooper Mechanical Services is excited to help businesses of all sizes plan and prepare for the inevitable power outages that come with living and working in the Myrtle Beach and greater coastal Caroline region.

Please contact Cooper to learn more.