View Full Version : 3 phase conversion
10-30-2002, 07:51 AM
I am lookin at a hobart 400 amp 3 phase welder (used) my question is,, is it possible to convert a welder I have heard of converting motors but would like to here from you guys before i jump out and buy it.
Hobart Expert Rock
10-30-2002, 12:24 PM
SKINNER.............MANY THING TO CONSIDER BUT I DON'T THINK IT WILL WORK..........CONVERTERS FOR 3 PHASE LATH'S, BRIDGEPORTS, ETC......YES WORK WELL........ONLY USE FOR STARTING MOTORS AND KEEPING THEM RUNNING........HOWEVER WELDERS USE MUCH CURRENT PER LEG OF 3 PHASE WELDER............RECONSIDER NOT PRACTICAL....... LOOK AT A SINGLE PHASE WELDING MACHINE DO YOU REQUIRE 400 AMPS OR WILL A SMALLER MACHINE WORK........ALSO WHICH 400 AMP WELDER, DO YOU KNOW THE MODEL NUMBER...........OR EVEN SERIAL NUMBER WILL HELP..............LET ME KNOW.......ROCK
10-30-2002, 01:12 PM
the only reason I was considering this large a welder was because there seems to be some bargins out there on these thee phase units...f but it is probably not worth it
Thanks for the heilp
10-30-2002, 01:52 PM
is this a transformer or motor generator power supply?
10-30-2002, 02:12 PM
Bargins on Ebay are sometimes not a bargin, but if you do have 3 phase service in your building you can get those big welders for a song.
Here is a link that sells them:
At $1000.00 and up you'll be able to create 3 phase.
10-30-2002, 04:43 PM
Bad idea to try to use a phase converter to run a welder, so much electricty will be wasted in a phase converter that you might think the power company
is billing you for lighting Time Square on New Years Eve:D :D .
You don't need to spend anywhere neer $1000 for a converter.
A 3 phase motor and some electrolitic capacitors are all you need, I built a 10 hp converter for a friend who has a machine shop, he had to move to a new shop where 3 phase wasn't available. $60 in capacitors and a second hand motor were all that was needed to make the converter, I don't know what the people that make the $1000 converters put in to theirs, Gold maybe?:D .
10-31-2002, 07:39 AM
Thanks guys I appreciate your input.. I have seen these nice big three phase welders on ebay for next to nothing. I was just wondered if there was a way to take advantage of them, but from past experiences I think I am going to pass because I have screwed myself before by try to be a cheepskate (sp?) and I seem to be a bargin adict but I am working on that!!!!!!
10-31-2002, 03:08 PM
you probably have made a wise decision but i must tell you i have run three phase welder plus lathes, milling machines, and drill presses with a rotary phase converter i built over 15 years ago with no real problems. one starter switch and a couple of capacitors are the only things i have replaced. if converter legs are balanced with power factor capacitors they are quite efficient.
07-09-2003, 06:50 PM
i have the same promblem but i am just going ahead and doing it the welder is being given to me and he is setting it up though too
07-09-2003, 07:36 PM
You didn't mention the voltage on your posts. If this is a 230 volt unit, a phase converter would work. If it's a 460 volt unit you would have to use a transformer to raise 230 household voltage. This would be very costly.
I have built 3 phase converters commercially for sewage lift stations in residential areas where no three phase power available. I also have one in my garage to tun a South bend lathe
You need a 3 phase motor to match the current draw of your welder, start capacitors, wire in parallel to start your three phase motor, you need about 100 microfarad per hous power. A contactor for the start caps, a time delay relay rated about .5 seconds to time the start contactor. a motor starter rated for the size motor you will use.
Now comes the tricky part, an assortment of run caps to balance the three phases when the welder in under load. Also put a "Phase monitor in the panel to shut everything down if there's a problem with 3 phase.
If you can get the parts used/free, this would be affordable
I bid a lift station job for a converter in a NEMA 4X stainless enclosure to run two 7.5hp pumps for $4000.00 installed and tested.
There are a lot of webbsights with 3 phase information, try the chaski sight
07-10-2003, 09:37 AM
Fla Jim, What do ya think about the 3 phase VFD inverters? How big of a VFD do I need? I have heard anywhere from 3-5 hp to run a 2.5 hp motor.
07-10-2003, 12:24 PM
i as u know am haveing the same promblem and i think that u need at least a 10 hp motor and a solid state or static I HEAR will work well
07-10-2003, 05:13 PM
you need @70% for a rotary phase converter [i.e. a 7hp will start and run a 10hp]. it will start even more hp if you have other 3ph motors on line. they add to the generator/converter.
07-11-2003, 06:58 AM
I've worked with VFD's. Used on a single phase input they work great to generate the three phase output for a motor. The drawback is cost. If you can get used parts for a rotorary converter the cost will be a lot less You have to derate the VFD a 10 hp rated to run a 7.5 hp motor etc.
I've never used a VFD for a transformer load, but if you have it ramp up quick it might work.
How common is 3 phase power, out at the pole on the streets?
07-27-2003, 03:43 PM
Three phase is found at all heavy manufacturing sites, at most large office buildings, and increasing it's presence in many suburban areas.
Easy way to ID 3 phase is by number of insulated wires on the pole cross bar. ( these are the high voltage ones on top) If you see three of them, with a fourth ground wire(no big insulators on this one, where it connects to pole), that is 3 phase.
Although there are other wire configurations, the above holds true in most areas.