Building a bridge ...

"Snag" wrote in message news:JEuGg.40395$ snipped-for-privacy@bignews6.bellsouth.net... | Rectifier , that is . Scored four 275 amp/600 volt units for a net cost of | ten bucks each (shipping included) . | Got the circuitry and heat sinks figgered out ... but I recall some talk | in a recent thread about inductors to stabilize the arc . Would I be safe in | assuming the unit needs a fairly large (2X2X6 ?) laminated core with a | winding capable of carrying the max current the welder is rated for ? My | question is , how many turns is this thing gonna need ? Is field density a | linear function ? Ten turns ? Thirty ? | I'm going to build a fullwave bridge , shouldn't really have that much | ripple . I had some training in electronics a few years ago (a few , he sez | ...) and understand the theory of inductive current stabilization . Just | don't have the math ...

Figuring that a few turns of lead wire around an iron table leg is enough, I figure that I could take some lead wire or copper tubing and wrap it through a loop cut out of steel plate would about cover it, but only be experimentation will that be improved upon. I like to have my stuff integrated, with components serving multiple functions, so the mounting structure will serve as a heat sink and inductor core, I'm thinking at this point. Haven't had a chance to get out and actually start on it at this point. Work has me creatively wiped out and not too inclined to do creative things once I get home.

I can make and email you pictures of inductor in my Hobart CyberTig, rated for 200 amps.

Are you on single phase (you talk about 4 diodes, not six as there would be in a three phase bridge). If so, your ripple will be as bad as it gets.

I can send you a picture of my inductor, if you want.

i

If these are four stud mount diodes, then, I think, you need three heatsinks, all of which would carry potential. (not a problem if you are wrapping isolated wire)

from my old auction for Semikron stud mount diodes:

ack

I'd like that pic - and don't worry too much about file size , we gots DSL here . I meant that voltage/current ripple will be much less than if I used just one diode as a halfwave bridge . I wish I had 3 phase , but in a residential area , they can't/won't supply it . And I got no room for a phase converter ... I may do like Carl and make a few turns around a core with some copper tube I have . I remember Dad (he was an ET , and a very smart man) building an arc stabilixer for a neighbor's engine powered welder , it was a bar of conductor bent into multiple "s" curves about a foot or so long mounted on insulators and wired in series . I recall the neighbor was amazed at how well it worked . I wish Dad were still around ...

OK, I will try to do it tonight. I can tell you now that this inductor is about 7x8x7 inches and is probably quite heavy.

i

Iggy,

I think your polarities are incorrect in url:

The polarity of the negative and positive outputs are reversed. I am sure it was a typo/grapho.

b

Hi Buffalo, I am sure that you could very well be right. I will double check it.

i

>

double

Simple rule with diodes - they point to the positive when rectifying

AWEM