3 phase to 1 phase inverter

[EEngel]

Hey guys,



I know there has to be at least 1 sparky among us.....



I recently got a Miller welder. However it's a 3 phase only. I only have single phase at the house and in the pole barn. I was told I could get a used inverter cheap. Well, I have been looking for a few weeks and have not found crap.



The unit claims it draws 33amps, so I assume on single phase it will draw 66. Does anybody know where I can find an inverter and what size I actually need.



Thanks!

 

[mikel]

Search around on the net, you should be able to pick up a used 3 phase motor (which will run on 1 phase power, it just won't start itself) and use it to genetate the other power leg that you need to run your 3 phase welder. There are some efficiency issues that you'll have to be aware of, but I have seen several of this type of setup in use and it seems to work pretty well.



If you want more info let me know and I'll try to dig up a couple of decent links that explain how to do this in pretty decent detail.



Good luck,

Mike

 

[Boomer II]

What Mikel said, I've been running my Mill and lathe on a rig like that for 20 years. I rope start the 3 phase motor then shoot the juice to it, it will generate the third leg.

Way cheaper than a store bought rig, just get the proper size 3ph motor.

 

[EEngel]

ya!!!!

Okay guys, I need more info on this theory. I have 3 phase motors all over the place. I work at an equipment design company. I think I have a nice 150hp sitting out in the lot right now. :-laf Actually, I know there are some small ones out there.



If you have a link to how to set this up, it would be great. I really don't want to pay $1000 for a phase converter.



TIA

 

[Boomer II]

I'm no electrician but here goes. Wire two hot legs to two of the legs on the motor. The third leg you run to the machine you want to run. I wrap a rope around the shaft of the motor and give it a spin, then I hit the breaker, it will run and generate a third leg for your other machine. Some lectrical whiz here can probably offer more detail.

 

[gregdoerfler]

so i can run a 3 phase motor to drive a piece of equipment on single phase? just by using any of the 2 legs?

 

[Boomer II]

A three phase motor will run on single phase, but it won't start, once you get it spinning you can shoot the power to it and it will run and generate power on the third leg. The hight dollar converters have a capacitor starter, but a small rope like a chain saw might have will work fine and cheap.

 

[Plazman]

converter

Finally, there is something I know a little bit about,

First off, you will need to make sure when you hook up the converter that the guys have mensioned, that you can isolate the control circuts, from the main power.

When you generate the third leg of power, it will not be the same voltage, ie 230, between any two legs.

You will most likely have a voltage of around 120, 120, and 175 to 195 to ground.

If you hooked up the 175 volts to the control circuits, they will fry, beleive me when I say that, experiance speaks loudly!!

A small converter will run run most motors in the 3 to 5 hp range with no problems, however when you go to demand close to max hp from the converter it will stall and most likely burn up.

I have a mill, lathe, cnc mill, surface grinder all on the same converter, it's the home made type like has been described, but with some major advantages like push button start and balanced voltage. I also have a 15 hp converter running a hydraulic pump in a machine that runs daily, it is a manufactuered unit and also has a balancing transformer.

If your unit requires about 33 amps total, thats probably a three phase rating, I would expect you to need a 7. 5 hp converter and hook it up to at least a 50 to 60 amp cicuit.

If you want look up http://www.gwm4-3phase.com/ , they will have the information you need to get going, just ask for a catalog and tell them what you want to do, there is wireing diagrams and other good stuuf in there.

Good luck on the project!

 

[nickleinonen]

at work, the gm locomotives use 3 phase cooling fans at ±230vac... when one phase blows open, the fans will run, but they will burn up pretty quickly...

 

[Alphacowboy]

any of you on here want to build a phase converter for me? My dad has one now (no motor type, just capsitors and relays) for his table saw, but he just picked up a 7. 5hp Dust collector, and it needs a phase converter as it is 3phase. Plus, he wants one that he doesnt have to turn on first, he wants to hit the switch for the dust collector and away it goes, make sense? thanks, Matt

 

[Plazman]

for the dust collector

Alphacowboy, I think your dad could use a static type converter for the collector, it will be only a starter, but will work fine for the load.

Those type of converterters only shift the phase for starting, and do not generate the 3rd leg, so you would actually be running only about 5hp, but that should be ok for the application.

They are fairly inexpensive at less than $200 for the one you would need, they offer HD models also, but I doubt he'll need that, just get one for the rated hp and away goes the dust!.

They are usually available at any electric motor distributer or repair company.

Look up phase-o-matic brand, they are easy to wire and are a good unit.

Good luck

 

[bmoeller]

We have a Roto-verter at one of the farms. Use it run the 3ph. motors. One is on a roller mill (cracks the corn), big cooling fan on a 25'x90' Harvestore silo and on the belt conveyors. It has its own breaker in the box. Probably running a total of 20hp worth of motors.



Kind of like these- http://www.ronkelectrical.com/pages/rotoverter.html

 

[barbwire]

Good info

 

[Alphacowboy]

man, for the prices to get the actual 7hp out of this, seems almost like just swapping the motor over to a 1ph 7hp motor would be cheaper. I would have to buy a new switch for it then though huh?

 

[BKenny]

Good info ,im an apprintice in the IBEW and we have been going over motors and controls this year. There are so many things to learn we have not gone over this yet . My only motor experiances so far have been industial aplications refineries ,peaker plants and buildings and we powerd them with 3 phases.

 

[Plazman]

Alphscowboy, to change out to a 7. 5 single phase would cost way more than a converter, you'll need new switches, new mag starter, overload protection, and new wireing most likely, as a new motor will prolly be around $550, plus the cost of the accessories! Try the static converter first.

Bkenny, if your in the IBEW, those guys just roll there eyes at guys like us that try and make their own three phase I have a relative that used to work for Alcoa, chief of electrical maintenance, he just grins at me!

But so far I have gotten by with what I do for three phase.