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Patrick

Tue Oct 05 2010, 02:26AM

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

jpsmith123 wrote ...

Anyway, I just started winding the second coil, and it's amazing how much better (and faster) it's going, based simply on the experience gained from the first one.

well thats good.

ill render some cad stuff and post it here.

jpsmith123

Tue Oct 12 2010, 01:48AM

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

Well my second coil came out good except for one section. I was talking to someone while doing it, and I got distracted and put too many turns in that section. It should still work, it just doesn't look right - and I'm irritated with myself for doing that.

Anyway, the next step is to pot the two coils - as soon as I decide what kind of potting material to use.

I'm wondering, are you any further along with your efforts, Patrick? I'm anxious to see exactly what your scheme is.

Patrick

Tue Oct 12 2010, 05:25AM

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

I'll post some stuff soon....

also, for your potting... i like vacuum - oil, or vacuum - polyester epoxy.
100 microns of vacuum, works well.

Niraj Joshi

Thu Oct 14 2010, 05:36PM

Registered Member #3291 Joined: Fri Oct 08 2010, 06:06PM
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Posts: 11

good work guys!!!

jpsmith123

Fri Dec 03 2010, 06:17AM

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

I kept thinking about the 30 gauge wire I used, instead of the 28 gauge wire I wanted to use, and it bothered me, so I made two more coil formers (yes, I know I'm crazy).

Anyway I made the grooves about 0.015" deeper, and that added enough room to get 425 turns of 28 gauge.

I just ordered some epoxy from MG Chemicals to pot it with.

The only issue right now is, I'm trying to figure out what's the best way to secure the loose end of the wire; I need to keep it secured somehow until it's potted and the epoxy cures.

I'm thinking about using a drop of crazy glue, but I'm not sure if the epoxy might weaken or dissolve the crazy glue before it cures. After all the work I've put into this so, far I'd hate for a little detail to go wrong and ruin things.

Patrick

Fri Dec 03 2010, 07:43AM

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

jpsmith123 wrote ...

I'm thinking about using a drop of crazy glue, but I'm not sure if the epoxy might weaken or dissolve the crazy glue before it cures. After all the work I've put into this so, far I'd hate for a little detail to go wrong and ruin things.

use the same epoxy your going to pot with, or use any other common epoxy after it cures, epoxies are generally compatable with each other. And i bet you wont have dissolving problems with super glue. cyano's are pretty stable and compatable with common epoxies. you dont need to worry so much about the chemistry.

Ash Small

Fri Dec 03 2010, 09:54AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Proud Mary wrote ...

.If your winding is neat, there's no reason why the PD between any adjacent, subjacent, or overjacent* turns should exceed the breakdown voltage is there?

A winding style sometimes used at high voltage has a triangular cross section, with each layer having less turns than the one beneath it. This maximizes the slant height distance between the highest voltage turns at the top, and the lower voltage turns at the bottom - it also prevents a higher voltage turn slipping down the side onto the next layer.

* Subjacent is a word usually only found in house conveyancing contracts to mean the flat/apartment below, and I invented 'overjacent' for want of an existing word!

The word you were looking for is 'superjacent'. (subjacent winding, adjacent winding, superjacent winding)

jpsmith123

Tue Dec 07 2010, 01:10AM

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

Patrick IIRC you were going to just put your transformer in oil.

Can I ask, how are you going to secure the end of the coil so it doesn't become loose and unwind, and also, what kind of oil are you going to use?

Patrick

Tue Dec 07 2010, 02:08AM

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

Yes, i wont pot my transformers, because i know i want to change the secondaries out, my pirmaries and secondaries are removeable/fixable. i will use either 100% vegatable oil from safeway, or i will use non-detergent 40 wheight motor oil, but remember 2 things:

-- I have 2.6 gallons of dielectric circulating into and out of a 3kW system, cost prohibits olive oil.
-- corn oil hardens (rock hard) PVC and vinyl aquarium tubing and i hope vegatable oil/motor wont,

if i had a small container, like a pint/quart or less and a transformer, I would use extra light virgin olive oil.
see my reasoning for olive oil here:

for wire handling:
-- i use a single hole in the plastic bobbin, loop the magnet wire through, tie it off, presto.
-- or i use crazy glue/epoxy. (i use the crazy glue with the brush in the bottle, so i can put a droplet down.)
then run a stranded wire or threaded stud nearby.

jpsmith123

Wed Dec 22 2010, 04:23AM

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

Patrick here is a paper you might find interesting which compares some properties of various vegetabe oils for purposes of service as an electrical insulating liquid.

I'm thinking more and more about abandoning the potting idea and just dunking everything in yellow olive oil or rapeseed oil.

The transformer is not the problem, but the multiplier seems like it could be problematic (with potting, that is).

For just putzing around making sparks, with low to medium power and/or with low duty cycle use, I think you don't have to worry too much about thermal issues of the diodes and capacitors in the multiplier. But for medium to high power applications and/or where the power supply might be running for a little while, I can see things getting too hot.

I can see the typical 2CL2FM HV diodes dissipating a few watts each, and the ceramic capacitors dissipating a few watts each (I'm trying to get more info on the DF of the cheap ebay ceramic capacitors to get a better idea), but I think with potting you would have to take steps to make sure your components don't overheat. IOW, I don't think you could just slap it together crudely and thoughtlessly and have it last a long time.

It's beginning to seem much easier to me to simply drown all the problems in vegetable oil.

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