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Registered Member #509
Joined: Sat Feb 10 2007, 07:02AM
Location:
Posts: 329
Well its really a bus bar, but with the 1/8" FR4 in the middle I guess you could call it a double sided 96 oz PCB.
Post soldering, and post cleanup of surface oxidation from soldering, all the bus bars laid out.
Everything laminated with neutral cure RTV, and bolted to some caps to keep it all clamped together. Kind of messy, but nothing a razor blade and some scotch brite cant fix.
Final bolt-up of the caps, all 11 hooked up. I still need to do mounting holes in the FR4, but its far enough away from the metal that I can do it without as-is. I'm also going to drill bolt-holes on the copper tabs for lugs
The obvious thing to do with a 1/2 farad bank of capacitors is see how big of a pop it will make. At 30 V, not horribly loud, did spew orange hot copper everywhere (used a ~18" length of 14 awg solid wire) It made decent gouges in the side so its definitely got a bit of bite behind if for only 30V
Thats (11) 50,000uF 50V nippon chemi-con capacitors in parallel on each bus bar assembly, each assembly is going to get its own thyristor to fire it in a capacitive discharge spot-welder that I'm making. But I figure even some of the SSTC guys would appreciate a low-inductance laminated bus.
Registered Member #1960
Joined: Thu Feb 05 2009, 11:57PM
Location:
Posts: 48
Thats a nice start.
For quality spot welds you need to be able to control weld energy and weld pressure.
If you're going with a thyristor you'll be forced to control the voltage of the bank. 30V will spew molten metal even with high clamping force.
I've got a basic CD welder myself, but I simply used a 1F audio capacitor. 11mOhms internal resistance gives a peak amperage of about 1kA. Doesn't fry my MOSFETS and welds 18650 battery terminals nicely. What's left is automation of weld pressure, doing this manually now.
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061
Heh, I tried this approach. The capacitor I had wasn't quite as good, as it seemed to have problems due to it being rated at 15V max. The ESR wasn't brilliant either, maybe it was damaged?
Registered Member #509
Joined: Sat Feb 10 2007, 07:02AM
Location:
Posts: 329
Storken wrote ...
Thats a nice start.
For quality spot welds you need to be able to control weld energy and weld pressure.
If you're going with a thyristor you'll be forced to control the voltage of the bank. 30V will spew molten metal even with high clamping force.
I've got a basic CD welder myself, but I simply used a 1F audio capacitor. 11mOhms internal resistance gives a peak amperage of about 1kA. Doesn't fry my MOSFETS and welds 18650 battery terminals nicely. What's left is automation of weld pressure, doing this manually now.
What are you going to weld?
I went with 50v capacitors because thats what jameco had on sale, and they were a good brand and good specs, so a little extra voltage never hurt. I was wary of 1F car audio caps as there are plenty of those which are counterfeit/filled with bricks etc... I'll be varying voltage with a smps or dc/dc on each bank, and I'll have the 3 cap arrays, so I can vary the size of the main bank from .55F to 1.65F. Maybe also play with a multi-pulse discharge for extending durations etc. Maybe a big anderson power pole on top of the unit with a shorting strap, that can be replaced with an air core inductor for slower/higher energy welds.
I also have a few more caps, and I'm looking at doing a small bank for an initial "cleaning" pulse i.e. like dual pulse units use, and perhaps a V-switch style setup to turn off the main thyristors.
I'm going to be welding ni-cd power tool packs, and maybe Li+ cells for flashlights if I end up doing some new ones. Maybe some of those craftsman robo-grip pliers would be good constant-force grip for heavier applications, if you dont need a huge reach. But if it ends up capable of doing light sheet metal, then I'll definitely use it for that too.
Conundrum wrote ...
Heh, I tried this approach. The capacitor I had wasn't quite as good, as it seemed to have problems due to it being rated at 15V max. The ESR wasn't brilliant either, maybe it was damaged?
-A
see my above comments about crappy caps, and for 2 examples of crap caps.
Dr. Dark Current wrote ...
Well was it printed? (as in Printed circuit board)
People that mill PCBs still call them PCBs, and there were prints involved at some point, so I'm gonna go with
Registered Member #509
Joined: Sat Feb 10 2007, 07:02AM
Location:
Posts: 329
EasternVoltageResearch wrote ...
Its not a PCB.
Its a Laminated Bus Bar.
and its almost a shame to have such a nice low inductance bus bar and only use it with 12v and a couple kA huh? instead of a nice hv bank and a rail gun, huh? ;p
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Thats not a pcb *THIS* is a PCB
(as in Printed circuit board)
