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What kind of jacks/terminals would be best for a bobbin?

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jpsmith123

Fri Jan 15 2010, 08:43PM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843

Well after many delays I've finally finished a few bobbins, but now, before winding them, I need to decide how to "connectorize" the things.

I could just drill holes and bring wire leads out, but that seems too crude and would create a weak spot. I suppose for the ground connection I could drill a hole and come out with a machine screw, but what to do for the HV leads? I suppose I could do the same there, but I'd rather use some kind of jack/terminal.

As the jack/terminal doesn't necessarily need to be insulated to withstand HV, something like a bananna jack comes to mind, but that seems too big and bulky. Something like the terminals used on ignition coils would be nice, but where do you get something like that?

Here's what the bobbins look like:

The winding length of the bobbins is 2.25 inches, and the radial build can be up to 0.525 inches. The bobbins are made of cpvc and snap together, but need to be glued for a permanent arrangement. There is also an optional outer casing (not shown) which can be snapped on and glued...and the assembly can be vacuum potted with epoxy or RTV.

With careful design, it seems to me that a transformer like this should be able to handle 5kw.

rp181

Fri Jan 15 2010, 10:13PM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
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Posts: 1529

I would drill it, and hold the end of the wire on with a brass screw. Then you can put a ring connector on the brass screw and a nut on top.

Erlend^SE

Sat Jan 16 2010, 12:00AM

Registered Member #1565 Joined: Wed Jun 25 2008, 09:08PM
Location: Norway
Posts: 159

Maybe you can use the HV wire from a TV (focus ones maybe? good for 10 KV compared to 40 KV for the main one).
If you drill a hole, put that wire into the hole and then seal the hole afterward, I think the isolation should be rather good :)

b.t.w. the iggy-connections? maybe get an old iggy coil to take it from?

b.t.w. there are many connection-methods used for printed circuit boards.. like flat-pins..
if it's good enough to use on a MOT.. maybe it will do for you too?

Hazmatt_(The Underdog)

Sat Jan 16 2010, 01:21AM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

I'm going to assume this is a PVC type material, so that means any hot metal will melt it.

I would make a small hole at the start of the winding and lead out the wire, solder that to a solder wick like braid, and epoxy that with some strain relief to the hole area.

Do your winding to fill the bobbin with one layer: at the end of the winding you insert the paper underneath the last turn and wrap around the coil until you come back on top, then start the winding again. This way the layers are kept nice and clean.

At the end of all of these layers you bring the last bit of wire through a heavy piece of insulating material in the middle, and put your terminal of choice there. This can be a piece of copper foil, a swedged terminal, large copper eyelit, or whatever you like.

Sulaiman

Sat Jan 16 2010, 06:28PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

When I use sturdy looking connectors/terminals I will tend to inadvertently use too much force tightening them, damaging the coil former.
I would slip a length of ptfe tubing over the wires and bring them out to a connector glued to the top ferrite piece.
For the eht (if any) wires I'd again use ptfe tubing but not connect to a terminal block
- leave the wires 'flying' and route them directly to wherever you need.
The ptfe tubing will protect the wire.

Patrick

Sun Jan 17 2010, 05:42AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Wow, cool bobbins. I use all thread-rod through a liquid tight aluminum oil tank for my 3Kw ferrite txmr.

the 500 volt 3-7amp inputs...ignore the cat 5 connector thats just for thermistors.

I will post high voltage connectors when I get a chance ... Im too drunk at the moment. They are soldered all-thread too.

-Patrick

jpsmith123

Mon Jan 18 2010, 05:17PM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843

That's a nice looking container you've got there, Patrick. Did you make it or buy it somewhere? My lathe is only 7x14", so that prevents me from trying to make something like that.

If I could buy a tank like that somewhere at a reasonable price, I would change my design and just put the transformer and multiplier in oil and be done with it.

Patrick

Tue Jan 19 2010, 03:03AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

100% made by me buddy, and dont any of you forget it...

lol ! I have only a CNC mill 14 wide 17 long 3 inch high milling volume. its a bridge frame i built it too, and i use kellyware's MaxStepper software ver4.0.01

Anyway i bought aluminim tubing 6 inch OD 8 inch tall, then two endplates then a polyehtylene lid with acrylic obround inulators.
ALL my own design, ALL milled by me for my Ion Lifter research and Masters degree thesis.

I am moving to Chico Ca, over the next few days. When i have the time i will post my HV connectors under those obrounds.

EDIT: Hey! ill send you a case if you give me the type and dimensions you want, and in lieu of money you turn a new spindle for my NC machine!? we can trade DXF files later...

Also, I see people use CPVC, is the dissipation factor better than normal PVC at frequency?

-Patrick

LutzH

Tue Jan 19 2010, 08:20PM

Registered Member #1721 Joined: Sat Sept 27 2008, 08:44PM
Location:
Posts: 136

Hello:

Real Cool!!! You are well on your way now, very nice construction so far, I am impressed. This beauty should perform very well, and be capable of an incredible amount of power.

What about just bending some 3/8" copper tubing into 2 rings which could be placed at the ends of the bobbin, and then soldered to the coil ends. This would give you a very smooth potential gradient at the coil ends?

I have seen this done in an X-ray HF HV transformer for a CT scanner, and in the one in the PDF below. One method used in X-ray application is to terminate the winding to a strip of copper foil, which is wrapped a full turn. The copper foil then looks to be connected at the ends. The copper strip would in effect be a shorted turn, so I cannot be 100% sure on this, but maybe its just not a problem. What it looks like they did is: Finish the winding, wrap a layer of Kapton insulation, then they added the copper foil strip (About 1 inch wide) , and connected it to the secondary winding end. This is followed by another insulation layer, from which a small square of insulation is cut out to make the final connection. The whole thing is then placed in oil.

Attached in a novel HFHV transformer, which has been posted before, but it does show the toroid shaped tube, winding termination method which I tried to explain above. I hope this is of use. Good job!!! I cannot wait to see the results once you post the pictures :)
]hvhf_transformer.pdf[/file]

Patrick

Tue Jan 19 2010, 11:17PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Hey LutzH and jpsmith123,

look and read carefully that PDF. You will see they mention and show those top and bottom rings are wrapped around the top and bottom of the bobbin, then the radius rings are cut all the way through in one place. This removes the shorted turn problem, and at power, a single loop would definatley be a problem.

This pdf was the reason why I built my tank, the way i did Lutz.

-Patrick

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