2.5kJ Capacitor Bank (Complete, finally!) / Projects / Forums

Forums

4hv.org :: Forums :: Projects

« Previous topic | Next topic »

2.5kJ Capacitor Bank (Complete, finally!)

previous 1 2 3 4 next

Move Thread

LAN_403

Mads Barnkob

Wed Feb 04 2009, 02:00PM

Registered Member #1403 Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968

Looking good with the new busbars instead of flattened pipe :)

aonomus

Wed Feb 04 2009, 04:50PM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

MadsKaizer wrote ...

Looking good with the new busbars instead of flattened pipe :)

They are flattened pipe...

aonomus

Thu Mar 05 2009, 02:05AM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

So I got tired of waiting for Fastenall to return my calls on whether or not they ordered my belleville washers (its been 2 weeks, they are no longer getting my business). I have been sitting on these aluminum bars for a while now, so I finally decided to drill the holes and bolt the things together.

Cost of aluminum bars ($3 per bar, 1-1/4" square, 4" long, likely 7075 alloy)
Cost of bolts ($20 for all the hardware!!?!)
Cost of SCRs ($5 a piece)
Making your own SCR clamps (Priceless).

Anyway, onto the pics.

The new and improved clamp, the thing weighs about 750 grams...

For the insulation I decided to use 2 layers of protoboard chopped up and placed between the clamp, and an aluminum flat for contact, with a washer to concentrate pressure in the centre. Just to be safe I oriented the pads on opposite sides (so there is a 2-layer thick portion of fiberglass board to insulate). This was repeated on both sides of the SCR, so the entire clamp itself is floating.

With these 2 clamps done, I will drill holes in the remaining buss bars to bolt the SCR clamps in, I think the entire capacitor bank will be laid out somewhat similar to a NST where the two HV connections come out either side of the box. This will reduce inductance inside the casing, and simplify internal connections.

Kolas

Thu Mar 05 2009, 11:47PM

Registered Member #102 Joined: Thu Feb 09 2006, 08:15PM
Location: Raleigh, NC
Posts: 169

Nice to see you went with the aluminum. It looks great aonomus. Are you planning on soldering those bus bars together? Oh and how about some more pics?

aonomus

Thu Mar 05 2009, 11:50PM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

Worked more on the cap bank today, more pics below.

SCR's mounted with the output terminals test fitted. Cap banks - they give you wings.

Close-up of the mounting

Test fit of the SCR clamps inside the case: these things just *barely* fit, the clamp on the right side scrapes against the plywood.

Arcstarter

Fri Mar 06 2009, 01:51AM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

:O :O :O :O

Very beautiful!
Looking forward to some stuff being shot and 'sploded.

Also, nice ingenious connections/construction, and the jokes are kool too (purposeful misspelling for the win!) :) :P

...

Fri Mar 06 2009, 03:33AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

That looks awesome!

One comment I might make, you might want to replace the Al bussbars with Cu ones, or at least make sure to star washers at the contacts (I believe you can get ones made out silver or copper for this purpose) to keep the oxidation from the Al from causing problems. I have heard of a few railguns having issues with bad connections to Al bussbars.

Keep up the good work!

aonomus

Fri Mar 06 2009, 04:29AM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

Yea, a few people have been asking me on IRC if I would deal with the contact issues, all the buss bars are only bolted together now, once construction is 100% complete will I sand down the joints, flux, and solder. This is just in case I need to re-measure things and change the configuration (I nearly had to as well since the SCR clamps turned out so huge).

Granted, solder isn't the best option, I suppose some silver solder would do well though?

Edit: late thought of the night
I could unroll some plumbing solder known to contain silver and measure resistance over distance x cross section area in mm^2, and compare to standard Pb/Sn solder... but at the gaps I'm going to fill (sub mm gaps) I don't think its an issue about what type...

Arcstarter

Sat Mar 07 2009, 11:52PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

Would solder actually work? Pulse discharge seems it would be quite hard on a little bit of solder! We shall see, i suppose.

aonomus

Sun Mar 08 2009, 12:00AM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

The solder should work since if the joint is properly made, it should fill the contact area voids between buss bars over a 1.5cm x 1.5cm area.

Also, I realized I forgot to mount rp181's gigantic stud diodes, these diodes are going in *series* with the capacitor bank so that they cut down most of the back-EMF to where small diodes (TO-XXX) can handle the remaining pulse. The diodes should also push every bit of energy into the work coil, and then some...

Also, the capacitor bank controls and charger will be mounted on the side of the capacitor bank, I will add a remote trigger so that I don't have to be so close to the bank, at least until I get longer lengths of welding cable (if I can afford them that is).

Anyway, more pics:

Isn't it so disarmingly benign looking? The blue protective plastic will be removed once I get the acrylic mounted with the hinge, just so I can avoid scratches.

And just to tease you guys :P

previous 1 2 3 4 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob