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welding info
daytona - 21/11/02 at 09:56 PM

have got the chance to buy a tig welder with AC/DC output for £200, the only problem is its 3 phase. Does anyone know if its possible to get it converted to single phase.


interestedparty - 21/11/02 at 10:06 PM

I'm going to guess that it would need a different transformer at least. You would probably do better getting one of those devices that converts single to three phase, trouble is, quite expensive

John


ProjectLMP - 22/11/02 at 04:06 AM

What amperage does it use? TIG welders generally use more amps than MIG. Professional single phase transformer based powersupplys can easily pull 100amps. A phase converter may be usable but they get really expensive for high current applications. You may not be able to supply the amount of current it requires from a domestic socket.


David Jenkins - 22/11/02 at 08:55 AM

quote:
Originally posted by interestedparty
I'm going to guess that it would need a different transformer at least. You would probably do better getting one of those devices that converts single to three phase, trouble is, quite expensive

John


A 3-phase converter wouldn't work - they take the single phase and 'fake' the other two with inductors & capacitors. When they are driving a 3-phase motor there is no problem, as the motor itself forces the phases into reasonable shape. You also have to buy a converter to match the motor size reasonably closely to aid this process.

The converter also gives a 'bump start' to help a 3-phase motor start before the phases are properly sorted by the motor.

The only way you could consider doing it is to use the converter to drive what is called a 'pilot motor' - a large 3-phase motor which spins without a load - which means that you get a reasonably realistic 3-phase supply permanently from the output.

(guess who went through all this when he bought a large 3-phase lathe )

As a guide, my converter cost over £200 and will only supply 15A starting current and under 10A running current - you won't run a welder off that!

So the answer is - keep looking for a decent 1-phase welder...

rgds,

David


Viper - 22/11/02 at 03:05 PM

quote:
Originally posted by daytona
have got the chance to buy a tig welder with AC/DC output for £200, the only problem is its 3 phase. Does anyone know if its possible to get it converted to single phase.


Do you know what the machine is? ie Miller, Kempi etc? if you can,t use it i might be interested...


daytona - 24/11/02 at 12:03 AM

not sure of the make although i know its american, capable of 300A with foot control


Wadders - 24/11/02 at 12:32 AM

I've also just bought a 3 phase lathe,and have been researching homemade rotary converters,try these links they may help.
Good luck

Al.
http://home.att.net/~waterfront-woods/Articles/phaseconverter.htm

http://home.att.net/~chipmaker/projpage.html
http://www.practicalmachinist.com/cgi-bin/ubbcgi/Ultimate.cgi


daytona - 24/11/02 at 12:35 AM

Hello wadders, what hp is your three phase motor as i have got single to three phase inverters for sale but only up to 1hp


Liam - 24/11/02 at 02:49 PM

Just a thought - you could find the other two phases at your local sub-station, and run a couple of extension leads to your house. "Nobody would mind!".

Sorry, I didn't even take my coat off...


Wadders - 24/11/02 at 05:48 PM

Hello wadders, what hp is your three phase motor as i have got single to three phase inverters for sale but only up to 1hp

Thanks for the offer Daytona,but unfortunately the lathe is 2 hp.

Cheers

Al.


interestedparty - 24/11/02 at 06:58 PM

If one wanted to buy a three phase lathe or other piece of motor driven machinery, wouldn't it be easier to just change the motor for a single phase unit?

John


Wadders - 24/11/02 at 07:11 PM

If one wanted to buy a three phase lathe or other piece of motor driven machinery, wouldn't it be easier to just change the motor for a single phase unit?

John

Valid point John,and correct to a degree,but single phase motors are between 30-50% less efficient than the equivelent 3 phase units,so in my case i would probably need a 3hp single phase motor,these aint cheap new,and hard to find second hand, then theres the hassle of mounting the thing.
I reckon i can build a rotary phase converter for peanuts,as large 3 phase motors ar worth nowt second hand.

ATB

Al.


bass - 24/11/02 at 07:47 PM

i run a 7HP motor off a converter, i did have an old converter that you had to run an other motor to make up the 2phs, but, it was a pain . starting up one motor just to use the b/saw, s/grinder, lathe ect. 3ph machines are a lot cheaper to buy s/hand plus the motors are smaller and last a lot longer. didnt like starating the compressor under load it burnt the motor out


stephen_gusterson - 24/11/02 at 08:02 PM

quote:
Originally posted by Liam
Just a thought - you could find the other two phases at your local sub-station, and run a couple of extension leads to your house. "Nobody would mind!".

Sorry, I didn't even take my coat off...



Actually, Liam, it wouldnt be as hard as that.

Three phases run down every street. Some houses are run from each phase, but I dont know what the 'firing order' is. But if you had a few friendly neighbours and long extension leads, you could give it a try.

This isnt a serious suggestion BTW!!!!






atb


steve


bass - 24/11/02 at 08:20 PM

some big houses, pubs, shops have 3ph


Wadders - 24/11/02 at 08:46 PM

some big houses, pubs, shops have 3ph

So do all lamposts,know what i'm saying?