Potting / vacuum impregnating... I think we're playing with words here... the two techniques have exactly the same purpose, which is as you rightfully describe it "to stabilize laminations and windings to fight resonance"
Whether the whole thing is potted or not, is just a matter of packaging....
This is all about priorities here... capacitance vs resonance
and I personnally believe with most transformers the interwinding capacitance is secondary (especially because rvrazvan did not state he was using your perfectly wound transformers
)Better not start your answers with "most of this is nonsense" when you're actually expressing a personnal view against another view (shared with a lot of others in the industry), as amatter of respect..., and because you're confusing a lot of people ( I think starting with "Most of this is absolutely correct, but I have a slightly different view... in the case of MY wonderful transformers, potting is not needed, etc, etc " would have been more adequate.... but I know in the world of Audiophiles, it's always better to use absolutes and superlatives to justify such price or sell such snake oil)
Cheers
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I "believe" I may understand what the original poster is asking...
I also wind very high bandwidth output transformers that i prefer not to vacuum impregnate for the same reasons...keeping the winding capacitance at a minimum...
Now the key thing to mention about this is that you can no longer use traditional Kraft paper for interleaving when you are not vacuum impregnating....mainly because "raw" Kraft paper is not a proper electrical insulator until it is impregnated and baked....Raw Kraft paper can burn and arc through very easily....I typically use TEFLON for my interleaving material, and no impregnation is needed...You can also use MYLAR, KAPTON...ect...
As for POTTING...this is when the body of the transformer is "suspended" in a gel or tar-like material...Such as McIntosh transformers are suspended in a black tar within a canister....
This provides a very nice mechanical isolation....This type of tar is soft low density for very low mechanical resonace below a Hz..
When I worked doing transformers for space application, a blue gel was used as potting material...this was a space qualified gel since it was not susceptible to outgasing...plus it had a thermal impedance better than air...obviously no air in space so thermal conduction is the ticket and now these potted canisters come in handy when mounted properly...Typically a Finite Element Analysis will show the transfer of heat "energy" gradient is improved...
Chris
I also wind very high bandwidth output transformers that i prefer not to vacuum impregnate for the same reasons...keeping the winding capacitance at a minimum...
Now the key thing to mention about this is that you can no longer use traditional Kraft paper for interleaving when you are not vacuum impregnating....mainly because "raw" Kraft paper is not a proper electrical insulator until it is impregnated and baked....Raw Kraft paper can burn and arc through very easily....I typically use TEFLON for my interleaving material, and no impregnation is needed...You can also use MYLAR, KAPTON...ect...
As for POTTING...this is when the body of the transformer is "suspended" in a gel or tar-like material...Such as McIntosh transformers are suspended in a black tar within a canister....
This provides a very nice mechanical isolation....This type of tar is soft low density for very low mechanical resonace below a Hz..
When I worked doing transformers for space application, a blue gel was used as potting material...this was a space qualified gel since it was not susceptible to outgasing...plus it had a thermal impedance better than air...obviously no air in space so thermal conduction is the ticket and now these potted canisters come in handy when mounted properly...Typically a Finite Element Analysis will show the transfer of heat "energy" gradient is improved...
Chris
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Teflon however is known to have pinholes and also is soft enough in the case where there is sufficient force applied to "squish" and even push through...
Mr. Lazybutt, potting and vacuum impregnating are NOT the same things, they may be related and a vacuum may be used during potting, but that is a different thing... the OP talked about heat transfer... speaking of which where did he go??
_-_-bear
PS. the other purpose of potting is to hold the thing in place inside a can...
Mr. Lazybutt, potting and vacuum impregnating are NOT the same things, they may be related and a vacuum may be used during potting, but that is a different thing... the OP talked about heat transfer... speaking of which where did he go??
_-_-bear
PS. the other purpose of potting is to hold the thing in place inside a can...
Please.... I tried to explain that the two techniques do not have the same purpose, but apparently my efforts have no succes
This is all about priorities here... capacitance vs resonance
and I personnally believe with most transformers the interwinding capacitance is secondary (especially because rvrazvan did not state he was using your perfectly wound transformers
That is your opinion; in my experience minimizing winding capacitance is beneficial.
I don't know what "rvrazvan not using my perfectly wound transformers" has to do with the subject here....
I once more repeat that what you said was nonsense!
Actually you are confusing a lot of people by saying that potting and vacuum impregnating are the same procedure serving the same purpose.
This has nothing to do with a personnal view.
I will not speak of "my wonderful transformers" and what they need or not, I just wanted to point out what the difference is between potting and vacuum impregnating.
Hi Chris,
There has been quite some development in interleaving materials.
I don't vacuum impregnate audio transformers for the reason you mentioned, but nevertheless I use kraft paper. The material I use is actually a sandwich consisting of two layers of kraftpaper with a layer of mylar in between, and can withstand a voltage differential of 6 kV which should be good enough for audio transformers. Total thickness is 5 mils (0,13 mm).
I think paper has a slight advantage over mylar when we speak of dielectric, teflon is even better but pretty expensive and more difficult to apply.
Hi. Be careful because when you pot transformer it will run hotter.....
Coatings, Compounds. Varnish - John C. Dolph Company
Dolph's are really nice.....
Regards, Taj
Coatings, Compounds. Varnish - John C. Dolph Company
Dolph's are really nice.....
Regards, Taj
Agreed 100%....
When I use TEFLON or MYLAR I typically sandwich it between the KRAFT paper ...One reason is the price also TEFLON is too slippery to deal with...windings go over the KRAFT much nicer... The third reason is that the Mylar, TEFLON film can get damaged with direct pressure of the wires laid over the top of it...that is why KRAFT makes a great buffer...then under these conditions the raw KRAFT paper is fine to use...
Chris
Generally, potting done right reduces temperature by adding surface area connected to the part with a lower thermal resistance than air. Sometime the device is potted into a case with fins.
You can buy mineral filled potting compound with a lower thermal resistance than the pure resins or you can simply add some regular sand for large parts. Adding it yourself is cheaper.
The only "problem" with sand is it makes eventual hacking out of the part pretty much nonproductive.
You can buy mineral filled potting compound with a lower thermal resistance than the pure resins or you can simply add some regular sand for large parts. Adding it yourself is cheaper.
The only "problem" with sand is it makes eventual hacking out of the part pretty much nonproductive.
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The nice thing of the stuff I use is that it is a ready made foil; look at this (I am sorry in German):
TP Politrix
Would it be fair to say then that your need is really just aesthetics, as long as the can cover doesn't degrade performance in any way (eg. winding temperature rise), but if you can easily achieve other benefits along the path then you would be pleased to add them for that comforting diy feeling?
I'm back. Busy day
So back to the potting. I just want to pot them. no vacuum impregnation. I have good transformers, but i want them looking like those tangos and tamuras
As I said, you can just put some fine sand in there...a solid spacer between the terminals and the iron, ur done. No mess. A little extra weight, not much.
_-_-bear
Pieter, thanks for the tip on the kraft/mylar sandwich stuff!
Chris, wazzup?
Did I say they WERE the same thing ????
I'm saying in the case of audio transformers (such as the ones from Tamura, Tango, James, etc...) potting serves the same PURPOSE as impregnation which is to stabilize the windings and avoid vibrations (for which of course vacuum is strongly recommended in both case, or it will not serve its full purpose).... Now there IS (in that case) indeed a difference in packaging: in one case the whole transformer is encapsulated in a can/case, and in the other not....
Now before you go and claim that they ARE totally different and have absolutely NOTHING in common, let me add that potting and impregnation have different purposessssss anyway, that may or may not be the same, and depend on the application overall (heat transfer, water/weather proofing, mechanical strengthening, increasing pressure resistance, electrical insulation, increasing dielectric ability, hiding construction, etc, etc , etc........ and it seems even aesthetic !...although it would be very unfair to limit potting to this application..)
It seems misreading / misinterpretating is the rule on this forum..... I will rest my case on this topic anyway and leave the way to the technical experts... (please don't even bother replying).
Have fun!
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I suggest that 3.5kg OT is not that heavy.
In some ways, if the OT was really heavy (such as in a 200W OT), then the best mounting method is to mount the transformer direct to chassis, using the chassis cutout as one bell end. However the transformer windings (and field) then are under chassis, and may require some more layout management (eg. using large distances in a big guitar or PA chassis).
A transformer mounted in free air has a certain effective thermal resistance to ambient at the operating temp of the surfaces. To add an extra material between the transformer surfaces and air may end up having a higher thermal resistance to air - depending on the relative temperatures and material interface - and probably needs a FEA, or a direct comparison experiment based on winding temperature rise.
In some ways, if the OT was really heavy (such as in a 200W OT), then the best mounting method is to mount the transformer direct to chassis, using the chassis cutout as one bell end. However the transformer windings (and field) then are under chassis, and may require some more layout management (eg. using large distances in a big guitar or PA chassis).
A transformer mounted in free air has a certain effective thermal resistance to ambient at the operating temp of the surfaces. To add an extra material between the transformer surfaces and air may end up having a higher thermal resistance to air - depending on the relative temperatures and material interface - and probably needs a FEA, or a direct comparison experiment based on winding temperature rise.
LazyB, you said:
"Potting / vacuum impregnating... I think we're playing with words here... the two techniques have exactly the same purpose"
To me that says that they are "the same" - of course they are not the same thing in a mechanical/physical sense.
But you went on in your subsequent post to explain things nicely...
However, the OP has more or less an aesthetic purpose in mind, yes?
_-_-bear
"Potting / vacuum impregnating... I think we're playing with words here... the two techniques have exactly the same purpose"
To me that says that they are "the same" - of course they are not the same thing in a mechanical/physical sense.
But you went on in your subsequent post to explain things nicely...
However, the OP has more or less an aesthetic purpose in mind, yes?
_-_-bear
LazyB, you said:
"Potting / vacuum impregnating... I think we're playing with words here... the two techniques have exactly the same purpose"
To me that says that they are "the same" - of course they are not the same thing in a mechanical/physical sense.
But you went on in your subsequent post to explain things nicely...
However, the OP has more or less an aesthetic purpose in mind, yes?
_-_-bear
Yes i do. I like japanese style amps ! love'em
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