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Grooved Bobbins For Segmented Windings

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Patrick

Wed Dec 22 2010, 05:23AM

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

jpsmith123 wrote ...

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

Glad to see you finnaly coming around.

its about time.

anyway my semester just ended, ill be making a new bobin in january... ill post all the devilish details for you in a thread. this way you can see my method, will read that link too.

Patrick

Wed Dec 22 2010, 05:29AM

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

EDIT: from earlier:

jpsmith123 wrote ...

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 have already read this artical it was decisive in convincing me to switch over to oils in general and food oils specifically. TY to Proud Mary, he posted this for me a long time ago.

OOPs this wasnt supposed to be a double post, been drinking dark Ale, clicky button being deceptive, sorry.

jpsmith123

Thu Dec 30 2010, 08:16AM

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

Believe it or not I just changed my mind back again. Yes, I realize this is getting silly now. I hope I'm done changing my mind for a while.

I just confirmed from the manufacturer of the cpvc material I'm using that "cooking oil", i.e., vegetable oil, is not compatible with CPVC.

Every time I endeavor to decide something, I subsequently find out I can't do it for some reason or another. It's starting to become quite burdensome...

Anyway, at first I wanted to use silicone potting compound, but it's hard to find anyone in the U.S. selling a small quantity of suitable material at a reasonable price. And to the extent I do find someone selling a small quantity at a reasonable price, it seems they don't have a complete set of specs on the material.

Same thing with epoxy but even worse.

Maybe I'm just being anal about it, but damn it, how can I compare products and pick the best one if I can't know what the thermal conductivity is, or the thermal expansion coefficient, or the dissipation factor? Or how these parameters vary with temperature?

Some manufacturers e.g., Loctite (formerly Dexter-Hysol) make an effort to provide a lot of this info, while others simply don't bother to mention it. But every time I find one I like, I find they only sell it in gallon or 5 gallon pails for a very high price.

If I'm going to use epoxy, I'd like a product with a relatively low viscosity (which would be easier to get the air out of); a relatively low dissipation factor; a relatively dielectric strength; a relatively high thermal conductivity; a relatively low hardness; a coefficient of thermal expansion that's somewhere close to that of CPVC; a relatively high "glass transition temperature"; and a not-too-short pot life.

If I could get this information on the all the prospective epoxies available at a reasonable price, I could pick one and do a little work with the numbers, and make sure that I won't have any thermal problems or thermally related issues.

But generally, unfortunately, no. Instead I find stuff like this:

, where you can buy two quarts for $30, apparently a good deal, but you don't get any info on thermal properties or dissipation factor.

So what good is that? It's beyond frustrating. I'm back to the beginning again with this potting nightmare.

Patrick wrote ...

jpsmith123 wrote ...

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

Glad to see you finnaly coming around.

its about time.

anyway my semester just ended, ill be making a new bobin in january... ill post all the devilish details for you in a thread. this way you can see my method, will read that link too.

Patrick

Thu Dec 30 2010, 08:09PM

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

what happens to the cpvc when exposed to oil?

jpsmith123

Thu Dec 30 2010, 09:54PM

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

Here's what they say about it:

"When CPVC pipe is installed in kitchen areas the pipe must be protected from contact with grease or cooking oils. Certain cooking oils can cause the CPVC piping to crack, leak or break when applied to the piping system. Consideration must be given to not only protecting the pipe from direct contact with cooking oils and/or grease, but also contact that may occur from airborne grease or oil from the environment such as cooking. Exposed piping in areas where CPVC pipe might come in contact with cooking oils and grease should be protected using a soffit system or with a complete coating of high quality water based paint that fully protects the piping system."

Patrick

Thu Dec 30 2010, 11:08PM

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

whoa! i did not know that.

jpsmith123

Fri Dec 31 2010, 05:33AM

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

Things may not be as bad as that statement implies, but I'm not going to chance it.

Apparently if one wants to use vegetable oil, one needs to go with a PE or PP coil form...and I'm already sick and tired of machining coil forms, so I'm just going to go ahead and use epoxy, as soon as I find one I like that's available in a small quantity at a reasonable price.

jpsmith123

Wed Mar 23 2011, 12:58AM

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

Well here's the latest (and I hope final) arrangement - before final assembly and potting:

In part because of concerns about high diode current and poor regulation, I decided to go with a full-wave quadrupler, thus necessitating an increase in secondary turns in order to get at least 12.5 kv peak out of the transformer (for 50 kvdc output).

This latest coil has 600 turns of 30 gauge magnet wire on grooved cpvc. What's not shown are the feed-through insulators that I'm still working on. (They will basically have an external geometry similar to a spark plug).

When I made these parts, I labored under the illusion that I was going to encapsulate the assembly with a certain epoxy that I had found, which not only had some available specs., but which specs. I thought would suffice for the application. But when I went to order the stuff from Ellsworth adhesives, they told me that it was no longer available. So the project now has to wait again until I find an affordable alternate material.

Patrick

Wed Mar 23 2011, 01:04AM

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

Oooooooooo very nice! can we get a pic thats of better resolution?

jpsmith123

Wed Mar 23 2011, 01:09AM

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

Thanks Patrick. I might have at least one of the insulators done by tomorrow...if so I'll post a better picture with at least one insulator installed.

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