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What Is 3 Phase Power?

What is three phase power? Do I have it? Do I need it? These are all questions you might be asking right now.

A Little Lesson In Power

Power can be thought of a little like pedaling on a bike, each push of the pedal is similar to the push electric current makes on the electrons in the wire. In Single-phase power its like riding a bike with one leg, you get one push for every cycle the pedal makes. This works well for things like lights and small appliances. Most home electrical panels are fed with two “legs” of Single-phase power, this means that each “phase” will reach it maximum voltage at a point in time that is exactly opposite of each other. The term Dual-phase is not often used but refers to both of the Single-phase legs being used together to run a motor, heat or other larger appliance; many people refer to this as a 240V or 220V circuit. Dual-phase power is like pedaling a bike with two legs, each leg pushes when it reaches the top, with the other leg directly opposite it at the bottom of its cycle. Three-phase power refers to power that provides three alternating currents (in essence three separate electrical “legs” all slightly out of phase with each other). This means that each “phase” will reach its maximum voltage at a point in time that is separated by 1/3 of the time in a full cycle. It’s a little more difficult to imagine this on a bicycle since you would need three pedals and three legs, but if you were a three legged wonder you could see how this type of pushing would be more constant. What this translates to in practical terms is that the power supplied by all three alternating currents remains constant. That consistency in power has a major benefit; three-phase motors, with one set of windings for each phase, is highly efficient and allows three-phase motors to use far less current than the equivalent single-phase motor.

Do I Need 3 Phase Power?

The average homeowner and small business does not need 3 Phase power. However, hobbyists with specialized equipment may find a need for it. Larger commercial customers can also find that they have equipment that needs three-phase power.

Why Doesn’t Everyone Have 3 Phase If Its More Constant?

Higher voltage power distribution equipment and three-phase panels cost considerably more than Single-phase equipment. With the average person not needing three-phase power the price difference to supply something tha would rarely be used makes it cost prohibitive.

What If I Need 3 Phase Power And Don’t Have It At My Home or Business?

Depending on the situation a number of options exist. You can opt to replace the motor with a single-phase motor,

which might be a good option if you only have one piece of equipment that you are trying to run. Since a three-phase motor can not start on single-phase power but can often times remain running on single-phase, a Static Phase Converter can be used to start the motor. But, this comes at the price of a 2/3 reduction in the rated horsepower and a shorter life expectancy for the motor. A rotary converter acts as a generator and can produce nearly balanced threephase power. If you have multiple pieces of three-phase equipment this is an effective way to power your machinery.

One caveat to consider with rotary converters is that more than one load typically cannot be started at a time. Another factor to consider is that some loads fall into different classes of "difficulty to start", and will require the rotary converter to be oversized. For example, air compressors are considered one of the toughest starting loads, the recommended factor is at least 2, and this can get very expensive. If you have a new commercial building and need three-phase power, talking to your Utility about up grading may be cheaper in the long run. A Service up grade will require some changes to your existing electrical panels, as well as an added transformer for you single-phase loads, but the change is often possible.