Hello folks ive just purchased a 1 farad cap to make a battery tab welder. im planning to use a automotive glow plug relay rated at 120A on the disharge side. -ve will be connected to cap and then to output electrode, the positive side on both the supply to the cap and the +ouput electrode will be switched, hope this makes sense. Hopefully completing soon will submit image and results.The primary of the glow plug relay will be switched by trigger switch attached to electrode(insulated of course), this switch will also switch primary feed to cap +ve either directly or by means of another 12v relay.
Supply via voltage reg set to 13.8v. (Lm317T)
Planning not to use Scr as these can be expensive for high current versions, and they have tendency to fail with this sort of set up.
Can anyone offer any further advice?

 

First, I think you have posted in the wrong forum. Perhaps a moderator will move your post to the new thread it deserves.

Second, You automotive relay will probably weld its contacts pretty soon after you start using it.

Third, we don't know where you are. I paid about $10 USD for my scr (used).

John

 

Hello bud trust me in the uk you can expect to pay $160+ for a good scr rated at 200A.

I dont think relay will melt down immediately, but might eventually fail, i will try anyway and post results.

 

Yes, but you are OT and in the wrong forum. Good luck.

 

Hello,

I moved the posts to a seperate thread.
In this thread you can have your own replies.

Bertus

 

Yes, but you are OT and in the wrong forum. Good luck.

What is OT?

Hello bud trust me in the uk you can expect to pay $160+ for a good scr rated at 200A.

I dont think relay will melt down immediately, but might eventually fail, i will try anyway and post results.

I think you are limiting yourself...

http://www.alliedelec.com/search/searchresults.aspx?N=0&Ntt=SCR&Ntk=Primary&i=0&sw=n&pn=2

They aren't that expensive, you need to refine your search.

 

Hello,

OT could be On Topic OR Off Topic.
The posts come from the thread of jpanhalt :
Project: Capacitor-discharge Spot Welder

Bertus

 

I bought a surplus IRKH91/12S90 SCR for $5. It's rated for 95A RMS continuous @12kv, and around 1,800A @ 60Hz one-time. I don't think I can afford enough capacitors to break it.

 

Hello,

OT could be On Topic OR Off Topic.

Yep, and I lose sleep worrying about whether NO means normally open, normally on, not open, or perhaps even, now okay.

I thought OT in context of the post was obvious. I will try to avoid that confusion in the future.

John

 

Instead of a glow plug relay, you might consider using a Ford starter solenoid. Those are available everywhere, and are capable of switching many hundreds of Amperes reliably.