After reading another post about inverters i also have a newarc inverta brought it 6/7 months ago with no paperwork or leads with it , was told just connect it to arc welder?? was told by local welding shop good job i didnt as would of blown it up, what i need is a Ac to Dc converter ,At the moment ime On my 5th week at colladge nights so just getting to grips with it ,, So As dont know much about tigwelding hopeing for a bit of advice/help How do i build an Ac to Dc converter? can/could sombody help with a diagram of what i need to buy and make ,,,,,,,, THANKS in advanced
- Thread starter john224
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If the "Newarc" has to be connected to a welder, then it sounds like it is a TIG Add-on Box, rather than an inverter. If it requires DC then the input connectors ( typically male Dinse plugs at the back ) will be marked "+" and "-". This is for connection to your welding current power source, which will have to be a DC Welding Power Source, not an AC buzz box or an oil-cooled Oxford. To convert the output of an AC welder to DC, then as rtbcomp said, you will need a bridge rectifier. That will have to be 4 big fat stud-mounted diodes, rated at about 100V and 100 or 200 Amps, mounted on a heatsink, possibly fan-cooled, plus maybe a choke ( inductor ) and some large smoothing capacitors. Unless you get lucky, none of these components will be cheap, and the chances of converting them to a sudden bang and some smoke are quite high too....
Sounds good - 400 Amp diodes - that should be enough! It may be helpful if you could describe the arc welder that you are planning to use ( make/model/specs/picture ). Ditto for the Newarc TIG box - pictures of front/back/inside & any data plates.
Looks like the Viper 2000 is a current product, with a .pdf data sheet on the newarc.co.uk website.
The manufacturer should be able to advise you, but I think that you will only need the rectifier. That involves mounting the four diodes on (a) suitable heatsink(s) and wiring them up with short thick cable. Can you post specs/pictures of the diodes?
The manufacturer should be able to advise you, but I think that you will only need the rectifier. That involves mounting the four diodes on (a) suitable heatsink(s) and wiring them up with short thick cable. Can you post specs/pictures of the diodes?
rtbcomp
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Have you looked here?
http://www.mig-welding.co.uk/forum/showthread.php?t=5016
It's best not to post pictures on external sites as they tend to get rempved.
SirDick Diodenob esquire
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I would try and buy a Murex Transarc Tradesman DC135 , the going rate on ebay is £35 to £50 , they were very popular in their day which was probably 20 years ago so they come up regularly for sale normally a bit battered about . You couldnt make something similar for anything near the price , they have a smooth DC output with a large choke and 100% duty cycle at 80amps , dinse sockets and you can probably lift it with one arm without getting a hernia . There is also a 200amp version if you need more current but for some reason they dont come up for sale very often and either could be used to supply your Newarc unit .
Just had a look on flebay for one of these But none on there?
Since you already have an AC arc welder and the four diodes, it shouldn't be too difficult to convert it to a DC set by making a rectifier. You will need three pieces of thick ( 5 to 10 mm ) sheet metal ( preferably aluminium ) as heat sinks. One piece should be twice the size of the other two, and it will have two of the diodes mounted on it. Depending on whether the diodes are "stud-cathode" or "stud-anode", this piece will become either the positive or the negative output of the rectifier. Use a voltmeter to check this polarity, before connecting to the TIG add-on box.
The other two pieces of metal will have one diode bolted to each of them. All three pieces will have to be mounted on a non-conducting base or chassis, so that they are insulated from each other. Depending on the load and duty cycle of your TIG welding work, the rectifier may need to be fan-cooled.
Using two short thick cables, join the tag or flexible cable ends of each of the two diodes that are paired on one heatsink to the studs of the other two, separate, diodes, and then on to the AC welder outputs.
Finally, the tag or flexible cable ends of the two separate diodes are linked together, and this will be the negative ( or positive ) output of the rectifier. As mentioned above, switch on the AC welder and use a DC voltmeter to verify that the rectifier output is DC, probably around 80V, and confirm the polarity, before connecting to the TIG add-on box.
The other two pieces of metal will have one diode bolted to each of them. All three pieces will have to be mounted on a non-conducting base or chassis, so that they are insulated from each other. Depending on the load and duty cycle of your TIG welding work, the rectifier may need to be fan-cooled.
Using two short thick cables, join the tag or flexible cable ends of each of the two diodes that are paired on one heatsink to the studs of the other two, separate, diodes, and then on to the AC welder outputs.
Finally, the tag or flexible cable ends of the two separate diodes are linked together, and this will be the negative ( or positive ) output of the rectifier. As mentioned above, switch on the AC welder and use a DC voltmeter to verify that the rectifier output is DC, probably around 80V, and confirm the polarity, before connecting to the TIG add-on box.
shenion
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Add 0.1 to .5uf 200V or better caps across the diodes. That will protect them from surges and from backfeed from the HF unit. Also helps emitted RF noise. On on the input and another on the output will help too.
A MOV across the +/- output would be good too to protect the diodes.
A MOV across the +/- output would be good too to protect the diodes.
