Potting transformers - Page 1
Forum section: electronics / projects

author: Haenk
author_rank: Super Contributor
timestamp: January 23, 2025, 11:22:31 am
content: Need a bit of technical advice, if potting toroidal transformers is a) not a bad thing and b) DIY feasable.For the sake of looks and easier installation, I'd like to pot a couple of toroids. However I'm uncertain, if leads to problems with heat transfer (the transformer will likely be oversized by factor 2-4, due to availability). Also I'd like to hear about experiences with (acoustic) noise transfer.If that checks out OK (like "there is no major downside) - how feasable is a no-further-equipment DIY approach? Sure, I'll need good potting stuff (likely some 2-component epoxy), non-conductive, certified for electrical appliances. Is that thin enough to reliably reach all gaps? Or is a vacuum chamber a must-have?

author: jonpaul
author_rank: Super Contributor
timestamp: January 23, 2025, 04:34:03 pm
content: Volts? Freq? power? size? Ferrite/powdered iron/tapewoud or other material?j

author: CosteC
author_rank: Regular Contributor
timestamp: January 24, 2025, 08:21:53 am
content: In general potting may easily reduce thermal performance, but it highly depends on construction and cooling methods.There are some potting resins and silicones with enchanted thermal conductivity, usually heavy and not trivial to use, air bubbles reduce thermal and electrical performance.What is difficult, is to seal wire-potting joint. It may open due to thermal cycling, vibrations, ageing. Potting is stiff, insulation tend to be elastic. This may lead to invisible corrosion inside.There are some other approaches like here:http://www.techto.pl/pl/oferta/transformatory/separacyjnesee photo.

author: Zero999
author_rank: Super Contributor
timestamp: January 24, 2025, 08:41:46 am
content: Buy one already potted.https://www.digikey.co.uk/en/products/detail/talema-group-llc/70061K/3881319https://uk.rs-online.com/web/p/toroidal-transformers/1234036https://www.tme.eu/gb/details/6545k-p1s2/toroidal-transformers/talema/

author: Haenk
author_rank: Super Contributor
timestamp: January 24, 2025, 12:01:19 pm
content: Quote from: Zero999 on January 24, 2025, 08:41:46 amVery funny.I always try to go with Talema, but sometimes there are things that no money can buy, as they simply don't exist. And that is a transformer with that voltage combo I need - potted. At least I got close enough with an unpotted one. (Of course I could go with a BTO one, but that is quite costly when I need 4 of them, way beyond I'm willing to spend.)

author: wraper
author_rank: Unknown
timestamp: January 24, 2025, 12:24:41 pm
content: Quote from: Haenk on January 23, 2025, 11:22:31 amDepends on insulation used. If it's some impenetrable film, potting with no vacuum will be a waste of time. If it's some fabric, likely it will penetrate quite well. But it certainly won't fill all the gaps.

author: Haenk
author_rank: Super Contributor
timestamp: January 24, 2025, 01:48:16 pm
content: Thanks all. I'll stick to non-potting them.

author: temperance
author_rank: Super Contributor
timestamp: January 24, 2025, 04:47:36 pm
content: QuoteEpoxy thermal conductivity ratings are about 5...20 times higher than air and potting at the same time increases the radiation surface. The same goes for polyurethane potting compound.

author: jonpaul
author_rank: Super Contributor
timestamp: January 28, 2025, 04:46:23 pm
content: reduces relialbilty, chemical corrosion, curing stresses.Many failures after potting.Jon

author: garrettm
author_rank: Frequent Contributor
timestamp: January 29, 2025, 03:34:41 am
content: Depends on the potting material. Soft RTV silicone compounds work well to dampen magnetostriction and winding vibrations. But soft potting compounds aren't going to help with mounting a toroid. Though I guess two large nylon washers and a nylon bolt would probably work well enough with RTV.Epoxies on the other hand are complicated. Some produce heat when curing, and can actually get hot enough to damage the winding insulation. I'd personally stick with soft, thermally conductive RTV type potting compound used for high voltage transformers.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: January 31, 2025, 03:25:24 am
content: DIY potting toroidal transformers does not work well. At least with mains rated transformer, there is an insulating film between the primary and secondary winding, and your transformer will probably still hum afterward. You can try with vacuum, but I won't dare to give any guarantees.Another option is to buy your transformer. There are companies that make transformers with custom windings, and some even do this for low quanities (such as one).

author: Smokey
author_rank: Super Contributor
timestamp: January 31, 2025, 03:32:46 am
content: Are you potting it for mounting reasons (potting the center so you can put a bolt through it) or potting for insulation reasons (so you can't short against the outer windings).?