3 phase machines working on single phase ?

[bcarwell]

I've seen several good buys on 3 phase welders and was wondering: can they be altered cost effectively to run on single phase, and if so, what's involved and what does that do to the performance specs ?

And is 3 phase just for commercial establishments, e.g. can the power company do something at the service drop to your house on a farm/ranch to give you 3 phase, or is this cost prohibitive or impractical if all you would use it for is a welder and maybe a few other things.

Bob

 

[gordon21]

I don't know about the converting part, but I can tell you that if you have 3 phase power nearby, you MIGHT get it at a big cost. You would probably have to buy a commercial acct with the power company. Power companies usually restrict 3 phase to commercially zoned areas. Expect a demand meter too instead of a regular meter.

If 3 phase is a mile or more away, you don't even want to know the price quote to bring it to your property. Hint: it will have at least 4 zeroes on the end.

 

[shaley]

3 phase may not even be available in your area and it usually cost a lot for the service as well. I would think that most industrial transformer welders would have a set of taps on the inputs to allow for 460v 240v 220v single or 3 phase. Better check the tech specs with the mfg to be sure. Mine is a ESAB Heliarc 250 and it has several input settings. I run it on single 220v.

 

[Ford960]

You can use a rotary or static converter to obtain the 3 phase but you need to be sure that the converter can supply the power needed.
One other way to beat the high price of 3 phase from the power company is to use a generator. This is common for machine shops because a better finish can be obtained with 3 phase machines.
I have a 100kw 3 phase diesel generator but all my stuff is single phase, however if I come across some good deals that are more affordable because they are 3 phase I'm ready.
Or maybe I should just sell the generator, wonder how much it's worth?

 

[ultrarunner]

I run my home shop off a 3 phase rotary converter I made from an old 3 phase electric motor. Never had any problems running the Leblond Lathe or the Bridgeport Mill... never tried to run a 3 phase welder

One of the small medical clinics I work with had a 3 phase rotary converter powering their instrument sterilizer. The thing is NO ONE knew they had a converter. It quit running after running non-stop for more then 12 years with no maintenance.

The clinic priced 3 phase from the power company and found it would cost about 10 times the cost of replacing the converter just for the hook-up.

The new heavy-duty converter cost $1500, installed.

 

[MadReferee]

There is a forum on the Practical Machinist web site that deals with the issues surrounding VFD and 3-phase power. You might find something interesting there that will help you.

Practical Machinist Transformers, Phase Converters and VFD

 

[DieselPower]

It cost me over $8,000 to get the power company to run 3 phase to my garage and that was years ago. I wouldn't even want to guess what it's running now.

Like Ford960 said, a good "mobile" alternative is a 3 phase generator. I have one, not a huge 100K like his but a old military generator. It's a 10K I picked up for under $300 and will run every 3 phase machine I have.

 

[EddieWalker]

I've seen several good buys on 3 phase welders and was wondering: can they be altered cost effectively to run on single phase, and if so, what's involved and what does that do to the performance specs ?

The short answer is no, it's not cost effective to buy and use 3 phase equipment when you don't already have it available. The small savings on the equipment don't even come close to the expense it will cost to make it work.

Eddie

 

[dirtrod]

I too built my own rotary phase converter. It’s great because you find used industrial equipment like your welder, mills, lathes etc. that are great bargains because they are older 3 phase units. My converter is a 5hp unit and cost me about $80 to build with some parts scrounging. The output balance is within 5% between the phases from no load to full load. Works great.

 

[sandman2234]

Running 3 phase equipment from single phase power happens all the time. You can do it several ways, depending on your needs for balanced power legs.
Static converters are the cheapest, rotary converters are what most people use, adding capacitors to balance the legs makes them better, and then you have the ultimate, which is "Phase Perfect" which are a little pricey, but do the job everyone wants, the way it should be. If your running 3 phase CNC equipment on single phase power, then that is the best way to go.

Back in the mid '90s, I asked one of the electricians how to do it, and he said you couldn't. I later found out how, and went and showed him a drawing and he said it wouldn't work. We went to the shop, tried it, it worked, but the voltage didn't make sense when read with a meter, but there it was, still working. He let it run for two days trying to burn the motor up from single-phasing, but it never did.
As mentioned, Practical Machinist has a good forum for phase converters.
David from jax

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