potted transformers

[resident]

I found some cool boxes that can put a xformer inside and make it like potted. But what is this black material inside a potted xformer that makes it potted?

 

[djQUAN]

I think it's a mixture of sand and epoxy.

 

[mcs]

But don't pot power transformers. Many of them will overheat. Transformers have to be designed for potting.

Best regards,

Mikkel C. Simonsen

 

[resident]

I'd like to pot the OPTs.

 

[rcavictim]

Neon sign xfmers have always used a black tarlike substance. It melts and flows with high heat. Perhaps the hot liquid tar that municipal workers use to patch cracks in asphalt road surfaces would be good for potting output xfmers. I don't like the idea of epoxy for two reasons. It is way too expensive and you cannot get back in and do repairs if ever necessary.

 

[SY]

You want something that's thermally conductive, doesn't have a terrifically high dielectric constant, has low ionic content, low toxicity and ease of processing, and of course non-magnetic. All signs point to platinum-catalyzed electronic-grade silicones with a high beryllium oxide loading.

 

[Carondimonio]

Neon sign xfmers have always used a black tarlike substance. It melts and flows with high heat. Perhaps the hot liquid tar that municipal workers use to patch cracks in asphalt road surfaces would be good for potting output xfmers. I don't like the idea of epoxy for two reasons. It is way too expensive and you cannot get back in and do repairs if ever necessary.

That kind of tar melts at around 200 °C; I believe such a temp could damage the OPTs (at least the insulation layers between windings).

Cheers,

Bruno

 

[markp]

You can buy potting compound from most of the larger parts suppliers.

 

[Burnedfingers]

Just buy them potted?

 

[resident]

I allready have them!
And those boxes I found where very cool but I'll leave them unpotted.This potting compound is too expensive.I found it at Farnell.It doesn't worth it for two OPTs.
And there's no any difference btw potted and unpotted,anyway.

 

[Yvesm]

... And there's no any difference btw potted and unpotted,anyway.

Agreed ! DO NOT POT

Yves.

 

[NickC]

For OPT
Why not pot with wax? It great i have used it for 1kv opt.
The wax is light and flows deep in between the windings. That way it prevents corona discharge to a certain level, absorbs the moisture between windings and makes the trans sound better to me, Fuller sound. Also wax melts at arond 70C so when u pour it into the trans the varnish would not melt. Also to remove the wax, heat the whole potted trans in an oven at 100C and all the waxs can be poured out. Beats tar(black substance) any day in performance however it melts low and it is really expensive depending on what wax type u used. For estimate parafin is 4.5kg for USD10, microcystalline wax is 4 kg for USD 40 and beeswax(best in performance and superb smell) 600G for USD 10.

Hope this helps
Cheers
Nicholas

 

[rcavictim]

Wax is fine except that I think regular candle parrafin melts at too low a temperature. It could liquify inside the casing on the sides in close proximity to output tubes. It could leak out and make a real mess. There are higher temperature parafins for industrial electrical use.

How about cheap, garden variety potting soil? Kidding!

 

[SY]

Why not pot with wax?

It's OK as long as you can be certain that heat isn't an issue.

 

[Prune]

Someone on the newsgroup said they use the tar used for roofing for their power transformers.

 

[NickC]

They have this version of wax called hard wax melts at 100C. Fine for most OPT. Any way OPT should not reach that temperature but if u need to feel safe that use hard wax at 100C. If it melts than the OPT must be cooking too.

Cheers

 

[analog_sa]

Why not pot with wax? It great i have used it for 1kv opt

NickC

Have you listened to the transformers before and after? I wonder what the effect on the sound is.

 

[djQUAN]

while we're on the topic of transformers, I have a power transformer about 200-300VA, and it came as custom made but the windings aren't encased in varnish or anything. just the whole thing put together then it's there. I want to seal it off or something. there is the choice of varnish, wax, or anything that could be poured into it. any recommendations?

 

[SHiFTY]

Why bother potting at all? I just used painted tin cans to cover my ouput transformers. Easy to take apart if anything goes wrong.

 

[jlsem]

Microcrystalline wax and beeswax here:

http://www.freemansupply.com/index.htm

Most audio transformers are potted with one or the other. For high voltage stuff, silicon oil and glass beads works.

John