Phase Converter

Single Phase to 3 Phase

I needed to power a 5 horsepower 3 phase electric motor but I only had access to single phase residential power.  After a lot of research I found that there are several solutions to this dilemma but at a cost of $1500 or more.  Below I will give you the opportunity to see how I built my rotary phase converter for under $500.  Yes it can be done.  I am running a 220V 4.8 HP 3 phase motor on 220V single phase power and it works very nicely.

So why even bother trying to use a phase converter?  220V single phase power is more common than 220V 3 phase power.  Most heavy duty industrial type tools and equipment are made with 3 phase electric motors because in addition to being less complex than single phase motors they are more efficient, powerful, and reliable than single phase motors.  Electric motors on tools that come from over seas often have 3 phase electric motors.  Used machinery with 3 phase motors typically sell for much less because of the 3 phase motors.  However, 3 phase motors are much more desirable than single phase motors especially where larger machine tools like mills, lathes, and saws are concerned.  So with a simple phase converter, those 3 phase motors can be put to good use.  Additionally, several 3 phase machines can be supplied 3 phase power by one converter.

There are several options available to get a three phase electric motor to run on single phase power. The first and most obvious option is to replace the machine's motor with a single phase motor.  But this may not be possible on most machines for a multitude of reasons.  Motor cost, shaft diameter, horsepower, and mounting limit this alternative almost every time.

Better alternatives are to use one of several single phase to three phase converter methods that will allow a three phase electric motor to run on single phase power. There are three basic types of converters: static, rotary and electronic.

Of the three, the static type phase converter is the least expensive. A static phase converter has no moving parts and needs to be sized for the motor it's running. Unfortunately, a static phase converter reduces the available horsepower of the motor by about a third and has difficulty starting air compressors and other machines with heavy starting loads. The reduced horsepower often isn't a problem and can be compensated for by reducing the feed rate or by taking lighter cuts. But overloading or stalling a motor hooked up to a static phase converter will cause destructive overheating of both the motor and the phase converter. A hard-to-start machine can be run by first starting another lightly loaded machine, an "idler" that serves as an electrical flywheel to start the second machine. A surplus three phase motor can be used as a dedicated idler that runs continuously to improve both the starting and the running of other motors hooked up to a static converter.

A rotary phase converter functions as both a motor and a generator. As a rotary phase converter is spun by single phase power, it generates three phase power to run other machines. More expensive than a static converter, a rotary phase converter costs around $600 for a 3-hp unit but doesn't have the starting and reduced power problems that occur with a static converter.  If you expect to own several three phase machines, buy a good sized rotary converter, which will be more economical in the long run.  I modified this method and ended up at a cost of less than $500 to power a 4.8 HP 3 phase motor which includes a 50' extension cord, plugs and receptacles, and ancillary parts.

An electronic phase converter is technically called an inverter and most catalogs will list this device under that name. An electronic inverter transforms single phase power into direct current and then uses microchip guided controls to simulate three phase alternating current. The electronics in an inverter allow you to control the motor's speed, torque and direction of rotation, and often allow for a soft start to bring the machine up to speed gradually. Most of the added control offered by an inverter would be wasted on a table saw but would be a great advantage on a lathe. Because it must be programmed, an inverter typically is dedicated to running only one machine 3 phase motor, but with compromises, it can be used to run several 3 phase motors. The price of inverters has been dropping steadily over the last few years but they are still expensive.  If you can afford the cost, in my opinion, this is the best way to convert single phase power to three phase power.

Choosing the right type and size of phase converter and hooking it up correctly can be complicated. You should do some research and get more advice before investing in a converter or an inverter. Manufacturers of converters and inverters offer extensive literature and phone consultations.  Should you choose to attempt to build one yourself, you should consult a qualified electrician or person experienced with working with electricity and electric motors before moving forward.

So that is about it.  You have all of the information you need to make an intelligent decision about what phase converter might suit your particular application.  However, if you want to consider making your own rotary phase converter and if you want the nickel tour of how I did it - no pun intended - I have detailed what I did with pictures and a couple of schematics in another web page.  You can purchase that information by selecting this button .  I show all of the details of how I put my phase converter system to work.  Motor sizes, wire sizes, receptacles, connections, and where I purchased my parts.  So how does this work?  When you select the "Show Me Details $5" button you will be taken to a shopping cart where you will fill out your billing information.  When that information has been submitted and approved, you will receive an email providing you with a link.  You will copy and paste this link into any web browser to access the additional information.

  Once you have been sent the link to the information there is no way for us to deny you access to the information, therefore, transactions are NOT refundable. 

Why $5?  It took some effort to get this thing to work right.  The information by way of pictures along with some very needed practical experience information will make everything clear as to how I did it and maybe keep you from hurting yourself or someone else.

How to tell if you have 220V single phase power in the first place?  What does 220V single phase even look like? 

Places to look for a 220V single phase outlet would be in a utility or laundry area where there is a close dryer.  If you have 220V single phase, you will find a fairly large 3 inlet receptacle.  The exact configuration will depend on the amperage of the circuit breaker in your fuse box.  This will generally be a 30 amp service.  Always use the correct plugs and receptacles that accommodate the supply voltage and amperage from your circuit breaker box.  In the diagram below the R stands for the receptacle (female) and P stands for the plug (male).  The number to the left of the P or R is the amperage.  You can see what the various plug / receptacles look like for 250V - 20, 30, and 50 amp configurations.  You must have 220V single phase power to run a 220V 3 phase motor.

phase converter receptacle and plug

You will need one of these receptacles somewhere in your house or garage.  If you have one of these receptacles , you have 220V single phase power. 



I needed to power a 4.8 HP 220/440V 3 phase motor that powers a hydraulic router head for profiling granite.  The machine is a $5000 machine that was worthless because I could not power the motor.  I didn't know anyone who had 3 phase power.  Not even some of the shops I went to had 3 phase power.  However, I did have 220V single phase power at my house and shop.  I built a rotary converter and it powers the hydraulic routers 3 phase motor.  The 3 phase motor does not get hot even when run for a long time.  It starts easily and  has full power.  I would have gladly paid someone $100 to tell me how to do this when I first need to power a 3 phase electric motor with single phase power.  I was initially looking at spending more than $1500 on a setup that I did not need.


Single Phase Power Running A Three Phase Electric Motor Using A 1 Phase to 3 Phase Converter