I dont know where this "pressure comes from" I've potted at least 10 transformers in potting epoxy and the only tim one didn't work it was because I hooked up the leads wrong.
The reaction is exothermic but once its completely fired off it one big hard rock with wires coming out. Electronics potting epoxy is not going to damage your choke.
The reaction is exothermic but once its completely fired off it one big hard rock with wires coming out. Electronics potting epoxy is not going to damage your choke.
I'm guessing that some folks will be of the opinion that a choke would 'sound better' if it's potted in a relaxed, unpressured, and generally zen-like state...
Epoxy certainly does exert pressure when it cures. I was involved in the non destructive testing industry for many years and built many types of probes and sensors. One particular style had several thousand turns of 50 gauge wire on a bobbin. We would have the probe connected to an ohm meter for the entire process of applying 5 minute epoxy. They would go open circuit just sitting on bench while the epoxy cured. So a certain percentage always failed during production. I tried to suggest using electronic grade silicone but was met with "we have always done it this way" argument. But I doubt anyone here would be using something that thin.
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You do get potting compounds from adhesive suppliers.
No harm in looking.
Buy the smallest, as those are time bound expiry, and as a hobby person, you do not need big quantities.
No harm in looking.
Buy the smallest, as those are time bound expiry, and as a hobby person, you do not need big quantities.
We've used this one with success.
https://www.homedepot.com/p/Crack-R...ect-Fire-Joint-Sealant-2085/205745400#overlay
Melt above 210F.
https://www.homedepot.com/p/Crack-R...ect-Fire-Joint-Sealant-2085/205745400#overlay
Melt above 210F.
I suppose the method is to heat the hot pour in a large Pyrex bowl with a pour spout in the oven at 350°F? How strong is the smell during heating?
Steel coffee can and a dumpster dove bbq will serve you well here.
Do it outdoors, away from food or cooking utensils. Put down cardboard or a drop cloth, you'll be making an enormous mess.
Do it outdoors, away from food or cooking utensils. Put down cardboard or a drop cloth, you'll be making an enormous mess.
If it’s really as bad as it’s being made out to be, I would just circle back to using a $7 cartridge of self-leveling polyurethane that doesn’t require a source of heat or produce fumes or require setup/teardown of a work space. The time and money saved is likely better spent on the extra isolation afforded by using rubber washers when mounting the transformer/choke.
Bee wax has low melt point, ceresin/paraffin is brittle and will crack. All of the above contain hard to remove water. While it's perhaps OK to impregnate transformer winding it's definitely not to pot. Old HV x-formers used some kind of tar/bitumen/asphalt, perhaps purified one.
What is the exact purpose in home environment? Moisture proofing or heat removal enhancement?
Epoxies without plasticizers are brittle, nor exacly water proof and shrink few per cent while curing. Dry ignition coils used to use epoxy of some kind. Preferred failure mode - crack.
What is the exact purpose in home environment? Moisture proofing or heat removal enhancement?
Epoxies without plasticizers are brittle, nor exacly water proof and shrink few per cent while curing. Dry ignition coils used to use epoxy of some kind. Preferred failure mode - crack.
- #45 seems to be a reasonable approach.
This keeps coming back to me, the wax melts too low of a temp I'm thinking. The tar above looks great but kind of a lot of setup effort. Epoxy may be fine but not sure if I want to make it rock hard. But for urethane I'd first have to test if it can cure totally if poured as thick as a container and doesn't just skin over for the top 12mm and just leaves a gooey center. If it can pass that test as fully curing if I fill up a paper coffee cup with it and cures to the center. It would meet many criteria, flexible but still hard, dense, wont melt, easy to use, etc. It needs to be tested, most brands specify 1/2 inch thickness for a bead thick curing is not mentioned.
Use baking paper (wax coated), as a former, and pour a tube, like those for sticky tape.
Even most plain plastic bags will work.
Just put the coil in the middle of an inner and an outer former.
And pour what you feel is right.
That will give you a tubular shape, which will be strong, and because of less thickness, cure through fully, no core softness to worry about.
Even most plain plastic bags will work.
Just put the coil in the middle of an inner and an outer former.
And pour what you feel is right.
That will give you a tubular shape, which will be strong, and because of less thickness, cure through fully, no core softness to worry about.
The test to see if self leveling urethane will fully cure is simple. Fill up a 20oz plastic drinking glass with urethane. Then seven days later saw it in half with a saw. If it has an uncured center then I know it is the type of product that will "skin over" rather than cure into a block. If it is wet in the center than we know its not an appropriate product to use for this purpose, seven days of not fully curing should be more than enough time.
I can tell you from experience that an expired tube of self-leveling poly cures solidly through, even when it’s never had it’s seal punctured. I’m sure you will be satisfied with the results of your test.
If you can find an expired cartridge on the store shelf, show it to the manager. Tell them you are just going to cut it in half and they may let you have it for free.
If you can find an expired cartridge on the store shelf, show it to the manager. Tell them you are just going to cut it in half and they may let you have it for free.
I wonder why someone would want to pot it. Shielding - yes, potting no. Properly done potting requires vacuum impregnation but by then instead of air between the windings you have a dieletric between them increasing interwinding capacitance.
In the past tar was used to stop insulation breakdown through humidity but modern wiring does not need it. YMMV
In the past tar was used to stop insulation breakdown through humidity but modern wiring does not need it. YMMV
If enamel coated wire is used, the leakage to dielectric will be prevented, I think.
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Potting with a solid filling compound under vacuum does fill any air gaps between windings, especially valid for bobbin edges. This starts to become useful at kV power transformers where the chance for corona discharges increases.
It also does help coil rattling noise, which is valid for high-leakage split bobbins transformers. They can rattle, especially with secondaries feeding large capacitor input filters. Potting gives additional mechanical rigidity to the coil and its surroundings.
Commercial impreg liquids for power transformer manufacture are specifically designed for high performance wetting in to coil voids - not something you want to splash on the floor and then have to clean up.
"Razors pain you,
Rivers are damp,
Acids stain you,
And drugs cause cramp.
Guns aren't lawful,
Nooses give,
Gas smells awful.
You might as well live."
-Dorothy Parker
Rivers are damp,
Acids stain you,
And drugs cause cramp.
Guns aren't lawful,
Nooses give,
Gas smells awful.
You might as well live."
-Dorothy Parker