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Transformer potting material? what material?

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Just checking if you had specific needs, eg. due to existing problems such as vibrating laminations or windings, or stray field causing feedback into sensitive stages, or ugly looks, or safety concerns from touching wiring or insulation, or ?

Is the transformer vacuum impregnated already, or just a dry build?

They are not, and i dont want that. i want the material around the transformer.
 
The material generally (always) used by professionals is Epoxy. I think there is little point in not having the Transformer vacuum impregnated. The epoxy potting is used to suppress vibrations in the windings and laminated core , so it has to penetrate the fine interleaves to be efficient.
presumably it also helps with heat resistance / transfer capability (not sure how it does, but I was told so when visiting one of my customers factory (they make high power generators).

I'm not sure where to buy the "Transformer specific" Epoxy, but a pot of standard bi-compound Epoxy glue would probably do the trick if you're not after a very optimised potting...
 
The material generally (always) used by professionals is Epoxy. I think there is little point in not having the Transformer vacuum impregnated. The epoxy potting is used to suppress vibrations in the windings and laminated core , so it has to penetrate the fine interleaves to be efficient.
presumably it also helps with heat resistance / transfer capability (not sure how it does, but I was told so when visiting one of my customers factory (they make high power generators).

I'm not sure where to buy the "Transformer specific" Epoxy, but a pot of standard bi-compound Epoxy glue would probably do the trick if you're not after a very optimised potting...

Most of this is nonsense...

I don't use epoxy based potting compounds or impregnation resins anymore because I found out to be allergic for epoxy; there are equally well functioning alternatives based on polyyrethane.

Epoxy potting is not used for impregnating windings and laminations; it does not have the right viscosity to do that; you must use resins to do that job.

Not vacuum impregnating audio transformers makes sense as vacuum impregnating will cause more capacitance and that is what we don't need here. Air is the best dielectricum as long as we don't put our transformers in vacuum.
 
Most of this is nonsense...

I don't use epoxy based potting compounds or impregnation resins anymore because I found out to be allergic for epoxy; there are equally well functioning alternatives based on polyyrethane.

Epoxy potting is not used for impregnating windings and laminations; it does not have the right viscosity to do that; you must use resins to do that job.

Not vacuum impregnating audio transformers makes sense as vacuum impregnating will cause more capacitance and that is what we don't need here. Air is the best dielectricum as long as we don't put our transformers in vacuum.

I love this kind of blanket statement .... because you're allergic to it so the industry is using the wrong compound...

I'm just telling back what someone who is manufacturing transformers told me.... they vacuum pot, and use Epoxy (and confirmed by a google search.. epoxy is the most widely used potting material for transformer)

AFAIK Epoxy IS a resin, viscosity is only a matter of the epoxy formulation

Yes Air is a better dielectric, ...but I'm not sure what we're trying to achieve if the potting does not penetrates the windings.. (why potting in the first place???)
 
I love this kind of blanket statement .... because you're allergic to it so the industry is using the wrong compound...

I'm just telling back what someone who is manufacturing transformers told me.... they vacuum pot, and use Epoxy (and confirmed by a google search.. epoxy is the most widely used potting material for transformer)

AFAIK Epoxy IS a resin, viscosity is only a matter of the epoxy formulation

Yes Air is a better dielectric, ...but I'm not sure what we're trying to achieve if the potting does not penetrates the windings.. (why potting in the first place???)

The point is that potting is not the same as vacuum impregnating.
I pot unimpregnated (audio)transformers almost daily; the potting compound, epoxy or not-epoxy based, is rather thick, and therefore will not impregnate laminations and windings.
Potting is part of esthetic finishing; it hardly effects the transformer specifications.

Vacuum impregnating is meant to stabilize laminations and windings to fight resonance.
For this reason I vacuum impregnate power supply transformers and power supply chokes, not with potting compound but with dedicated and thinner impregnation resins.
Audio transformers, at least mine, do not need vacuum impregnation. I prefer not do impregnate these because there will be more (unwanted) capacitance.

Potting compounds and impregnation resins can be epoxy, polyurethane or whatever based as long as they work as required.
I prefer non-epoxy materials because of my allergy to epoxy, and also because epoxy based fluids produce more solvents which is not good, especially when used in small rooms like in my situation.
There has been quite some development in this stuff because safety regulations has become more severe. Like for instance water based solventless paints there has been comparable development in industrial compounds and resins.

Lundahl do not pot their transformers; vacuum impregnation is done to make the coils stable so that wires stay in place.
 
I love this kind of blanket statement .... because you're allergic to it so the industry is using the wrong compound...

Right.
It took me almost two years to find out that the epoxy based potting compounds and resins caused my skin problems. Medical tests did not point in the direction of epoxy because these tests are more oriented to find out the influence of all kinds of food and things like cat/dog hair, copper, a.s.o.
When I discovered the cause by trying polyurethane based compounds and resins (my skin problems disappeared) I talked to my supplier about it. He told that in larger transformer manufacturing companies where more people work with epoxy based stuff often one or more guys develop health problems. Then it is up to the boss wether he stops using epoxy (and must maybe invest in other equipment) or solves the problem otherwise.
 
Yikes!

Most windings are impregnated with a VARNISH.
The newer varnishes are no longer classic Glyptal varnish, but more modern alternatives.
You must vacuum impregnate if you want the material (a liquid) to reach fully into the transformer windings. Otoh, most motor winding shops do not vacuum impregnate.

For potting compound the classic material is TAR.
Black bituminous compound. Requires heat to melt.

I would avoid putting any metal into an epoxy and using that in the hope that it will transfer heat because it will also be conductive.

The commercial conductive compounds that I have seen are intended for thin applications, like small heatsinks on top of plastic ICs... but I suppose there are impregnated materials that are for thick/poured uses...

There are also silicone rubber potting compounds, but these are not intended for high heat transfer ability afaik.

Most epoxy compounds get softer as the heat goes up...

There is a difference between impregnating the windings and potting the entire transformer in a can.

The big question is why do you need much heat transfer in the first place?

_-_-bear

PS. if all you are looking for is the "look" like the Tango units shown, you do not NEED to fill the cans with anything at all! Also you can use fine grain sand too...
 
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