convert AC welder to DC

I have a huge bridge rectifier I would like to use to convert an AC stick
welder to DC. It is as simple as just connecting the rectifier to the welder
or will I need something else like some sort of filtering.
Jimmie
Reply to
Jimmie D
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No real filtering but many have a high current coil (RF) in series and an arc-over plate set to help develop an arc. Not required and can be hard on the bridge by to high a voltage generated.
Martin Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net TSRA, Life; NRA LOH & Endowment Member, Golden Eagle, Patriot"s Medal. NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member.
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Jimmie D wrote:
Reply to
Martin H. Eastburn
> No real filtering but many have a high current coil (RF) in series > and an arc-over plate set to help develop an arc. Not required > and can be hard on the bridge by to high a voltage generated. > > Martin > Martin H. Eastburn > @ home at Lions' Lair with our computer lionslair at consolidated dot net > TSRA, Life; NRA LOH & Endowment Member, Golden Eagle, Patriot"s Medal. > NRA Second Amendment Task Force Charter Founder > IHMSA and NRA Metallic Silhouette maker & member.http://lufk> > I have a huge bridge rectifier I would like to use to convert an AC stick > > welder to DC. It is as simple as just connecting the rectifier to the welder > > or will I need something else like some sort of filtering. > > > Jimmie > >
Reply to
Too_Many_Tools
Do you have any part numbers or specs on the diodes? How do the specs compare with the peak voltage and current from the welder? Lots of voltage headroom is probably a good idea due to voltage transients. Probably also a good idea to actually measure the peak current that your welder can put out into a short circuit and be sure the diodes can handle that with ease.
An arc stabilizer coil is beneficial on the output of the bridge. Also, while I do not know, I suspect a modest value capacitor across the bridge output would, in combination with the coil, provide a filter to help block HF or voltage spikes from getting back to the diodes from the welding leads. It can be a low value like 0.1 microfarad at a few hundred volts since it only has to be effective at high frequencies.
awright
Reply to
awright
The diode stack is rated at 500 amps 500 PIV. It operated at 48 volts and around 200 AMP as as prt of a battery charger. They are leadless diodes compressed between the fins of the heat sink. The heatsink plates are 5/8 x 12 x12 inch plates of copper. Seems like some of the welders I have been inside of had a choke nearly as large as the transformer.
Jimmie
Reply to
Jimmie D
Jimmie, you may be interested in the looong thread on the topic of making a homemade smoothing coil by Rick V at the Welding Web forum:
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. Not a simple, "here's how to make a coil," but he reports on a lot of experimentation on building a coil for welding with car batteries. The last time I tried to access the thread I could only bring up the second page. I think the system is choking on all the pictures and figures he posted.
I don't endorse or have an opinion on his approach, but he presents a lot of experinental results.
As I recall, outfits like Northern Tool offered arc stabilizing coils for welders that were not too expensive.
awright
Reply to
awright
I was too sleepy!
The arc plate is between the input of the coil (coil continues on to output. It is so when a high voltage Oscillation of you trying to start current - it flies back in a sense and generates high voltage that then keeps the arc going to start high current. The voltage generated can be high -
so - now to the point - two sharp edges backed away from each other - guess - now maybe 1/8" don't have arc breakdown of air at all humid conditions... the arc points breakdown the HV and limit it to that value. It is a voltage regulator.
Very high voltage ones I have used in life (still alive) - were large spheres of plated copper that were hand cranked (life and death machine!) until the arc distance is set to xx mm and then that set the operating voltage. (The capacitors were in oil baths!) The big black switch was thrown and blue-white arc danced until we turned it off. With gloves and with hope and faith we would turn up/down the high voltage.
The LC circuit that generates is typically an L filter looking.
See if you can find some TIG designs as they have them also.
Martin
Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net TSRA, Life; NRA LOH & Endowment Member, Golden Eagle, Patriot"s Medal. NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member.
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Too_Many_Tools wrote: > >> No real filtering but many have a high current coil (RF) in series >> and an arc-over plate set to help develop an arc. Not required >> and can be hard on the bridge by to high a voltage generated. >> >> Martin >> Martin H. Eastburn >> @ home at Lions' Lair with our computer lionslair at consolidated dot net >> TSRA, Life; NRA LOH & Endowment Member, Golden Eagle, Patriot"s Medal. >> NRA Second Amendment Task Force Charter Founder >> IHMSA and NRA Metallic Silhouette maker & member.http://lufk>>> I have a huge bridge rectifier I would like to use to convert an AC stick >>> welder to DC. It is as simple as just connecting the rectifier to the welder >>> or will I need something else like some sort of filtering. >>> Jimmie >>
Reply to
Martin H. Eastburn
Yes, every one I've seen includes a large choke in series with the output after the rectifiers to act as a filter. I don't know if it's required, or if it's just there because it makes the arc more stable and easy to work with.
The high frequency circuit the other person was talking about is a feature on Tig machines. At least that's the only place I've seen them. They add a very high frequency (many Mhz) and high voltage (thousands of volts) but very low current output to the signal to cause it to start the arc without having to make contact between the electrode and the work. They use high voltage to make it start the arc across a wide gap, and they use high frequency to protect the person welding from the high voltage. High frequency current tends to travel only on the top of the skin and not though the deep tissues so the damage from being shocked by it is minimal.
This is done by a simple spark gap resonator circuit. It's basically a Tesla Coil with the high voltage step up transformer connected in series with the welding current output. If you add a high frequency generator, you need to add bypass capacitors around the rectifiers to prevent the high voltage from blowing out the rectifiers.
The HF unit is nice if you intend to do Tig work with your DC welder, but it's not needed if you are just trying to make a DC stick welder.
Reply to
Curt Welch
Got a link to those arc stabilizing coils?
I looked but could not find any.
Thanks
TMT
Reply to
Too_Many_Tools

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