Replies

1. 
   Stuart | Oct 12, 2005 11:28pm | #1

   There are several ways to do it, whether it's worth the extra expense and fooling around is up to you.

   1) Use a rotary phase converter. It's basically a single phase motor connected to a three phase generator, you plug the single phase motor into the wall and the generator creates three phase power to run the saw.

   2) Use a static phase converter. It's a box you hang on the wall, and it creates a three phase output from a single phase input without any moving parts. One of the bigger manufacturers of these is Ronk (they also make rotary phase converters.) http://www.ronkelectrical.com/

   3) Use a variable frequency drive (VFD), also sometimes called adjustable speed drives (ASD) or inverters. Their main purpose is to control motor speed, but you can also use them to generate three phase power from a single phase power input. There are a number of companies selling these, from the big names (Allen-Bradley, Square D) to other companies like Fuji or Koyo. One place that sells them mail order is Automation Direct. http://www.automationdirect.com

   4) If you're handy with such things, there are plans floating around the Internet for building your own static phase converter.

   A homebuilt converter can be pretty cheap if you can scrounge the parts to build it, the other choices are fairly expensive (hundreds of dollars, probably) unless you can find them used. This is all assuming you're looking at a three phase tool that runs at 220/240VAC. If it's rated for 480VAC use, then you'd also have to have some sort of stepup transformer, and it rapidly becomes not very practical at all.

   
   

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   Edited 10/12/2005 4:42 pm ET by Stuart

2. 
   JohnWW | Oct 12, 2005 11:42pm | #2

   By the time I posted this, Stuart had beat me to it, we seem to agree on most points:

   To run a three phase motor on single phase service you will need a device that converts the single phase into some approximation of three phase power.  These devices come in three basic flavors:

   1.  Static converters, these are generally the cheapest, and don't allow the motor to develop full horse power, but you probably wouldn't notice the difference unless you are doing very heavy cutting.  Static converters are electrically matched to the machine they are running, so they can't be used to run several different machines.

   2.  Rotary converters, these are basically a three phase motor that's started up with either a single phase starter motor or a built in static converter and then the idling motor generates three phase power to run the saw motor.  Rotaries are heavier and more expensive than a static converter but you can run a whole shop full of machinery off of one with no problems.  It is fairly simple, and can be inexpensive, to make a rotary converter from a salvaged three phase motor.

   3.  Inverters, these are computer controlled power supplies that electronically slice and dice single phase incoming power and turn it into a very good approximation of three phase.  Inverters allow all sorts of fancy motor functions like speed control, braking, reversing, and the like, but these really aren't needed on something as simple as a table saw, but it is nice for a lathe or drill press.  The price on these has been coming down rapidly as they have become more popular so they may be competitive with the price of static converters.  Like the static converters, the inverters are typically matched to a single machine, so that additional units would have to be purchased if you added more three phase tools to your shop.

   In addition to the phase of the saw's motor, also check the motor's voltage, since none of these devices, with the possible exception of some inverters, can turn 220 volt power into the 440 to 460 volts used on some industrial machines.

   John W.   

   
   

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   Edited 10/12/2005 4:45 pm ET by JohnWW

1. 
   RickL | Oct 13, 2005 12:30am | #3

   I'm going to add to John's comment on static converters. Static converters are not really converters at all. It's using capacitors and a timer to add the third leg so a three phase motor will start.  Basically it helps the motor to start then does absolutley nothing after that.   A three phase motor will run on 220 single phase but it's running on two thirds power because it's missing the third leg.  For many applications with industrial machines and the home shop worker this loss of power isn't really noticable on many machines.

2. 
   Stuart | Oct 13, 2005 03:13am | #4

   I guess my description of a rotary converter wasn't quite right, but then again I've always tried to avoid using them so I'm not a real expert... :-)

   One other possibility that hasn't been mentioned is you *may* be able to retrofit a three phase saw with a single phase motor, but new motors aren't cheap and you'd have to find one that would bolt in place of the original.

3. 
   TJB | Oct 13, 2005 03:45am | #5

   I recently had the same issue with a 3 phase shaper I purchased thinking I could just swap out with a 2 or three hp single phase motor. Finding  a motor with the same mounting configuration was hard to find. When I did find one it was expensive ($400).

   What I did was find a rotary converter for about $350. That is including some heavy duty wire, breakers and shipping. It works like a charm. I have some knowlege of wiring and did the work myself. I figure now I can buy a 3 phase air compresor and run that as well or even a power feeder. Looking at how its put together the next time I need one I will make it myself with a used 3 phase motor and just scrounge the rest of the parts.