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Hints, Tips and Solutions (Do NOT post requests for help here) If you have any useful general hints and tips for vintage technology repair and restoration, please share them here. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

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Old 11th Nov 2020, 1:06 pm   #1
Al (astral highway)
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Default Heavy busbar design...PINK DIE 42's re-purposed.

I needed to make a very robust HT DC busbar, to supply gulps of current to a big old IGBT. This is part of a very large inverter build to run at HF, another iteration in a long-standing project that I will post about soon.

I tried various designs made from copper strip cut with shears and elaborately soldered, but...

1) the overall distance between the power supply and the action was still not ideal and I knew I could do better and shave off a few more nH of inductance.

2) The other problem was access in a confined space as I'll need to bolt the busbars axially to their homes. So I started over again and looked carefully at the materials I had already.

Lurking around was a set of PINK DIE 42 clamps. I have seen these used for the heavy connections to a giant earth return busbar used in large buildings. These are rated in some kA for use in a fault returning giant currents to earth.

My purpose will not only see a steady DC current on them but also large pulse currents.

I modified the components by filing down the angles of an M6 brass bolt until it was a very tight mechanical fit with a few taps from a hammer. I then soldered the bolt in place with a propane torch and high melting point solder containing a small amount of silver. Note the brass bolt in the second photo now has a copper colour, presumably because the Zn in the alloy boils off under the intense heat of a blowtorch.(

Two of the pieces were cut to allow an angled surface for clearance from the IGBT terminals.

There are four pieces that can be clamped together. I have fitted two to a large capacitor, axially. The other two are fitted to an IGBT module.

A voltage divider (which is actually a big old assembly, illustrated) will also clamp to the busbar. It needs a bit of polishing but is good to go mechanically and electrically. Pic is for illustration as there will be other connections.

I did all of this with no dedicated workshop and with hand-tools only. I found it very satisfying to reach a practical solution. I enjoy the aspect of this activity that is related to materials and their nature and capacities.

The result is not only fit for purpose in terms of very low inductance but also enables modules of the circuit to be disassembled for transport, which was one on the 'desirable' list.

And because the components will be bolted together, there will be no stress, axially, on the capacitor or IGBT terminals.

Finally, it enables very clear distinction between HT+ and -, for ease of measurements.

Happy days!
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Old 11th Nov 2020, 5:40 pm   #2
Al (astral highway)
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Default Re: Heavy busbar design...PINK DIE 42's re-purposed.

Oops. Not shown or described is the addition of small tinned brackets to the ends of two of the pieces. This has just been prepared for the addition of the bracket in photo 3.

Hopefully you can make this out in the photo of the IGBT module.
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Old 11th Nov 2020, 5:51 pm   #3
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Default Re: Heavy busbar design...PINK DIE 42's re-purposed.

Take a look at consumer unit busbars.
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Old 11th Nov 2020, 6:34 pm   #4
Al (astral highway)
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Default Re: Heavy busbar design...PINK DIE 42's re-purposed.

Quote:
Originally Posted by merlinmaxwell View Post
Take a look at consumer unit busbars.
Yes, I'm familiar with those. I've also seen where multiple building earths are bonded to a hefty great copper busbar with bolts under huge torque.

The challenge here wasn't the material, it was more about fitting a suitable conductor (with low inductance at DC and HF) axially by bolting (to the capacitor and IGBT module). Hence the need for some ingenuity and fettling.
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Old 12th Nov 2020, 9:50 pm   #5
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Default Re: Heavy busbar design...PINK DIE 42's re-purposed.

Astral- years ago when we had additions to racking in repeater stations, the 24v busbar was extended in aluminium and I remember where two busbars were joined, that the mating surfaces were cleaned using some sort of abrasive combined with petroleum jelly.
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