Toroidal transformer potting experiement - Page 1
Forum section: electronics / projects

author: Coordonnée_chromatique
author_rank: Frequent Contributor
timestamp: November 01, 2020, 02:10:13 pm
content: Hello all.I've constructed the half-wave dummy load that deform the waves at the input and induce some magnetostriction noise in the transformer core and i'm trying to muffle this noise with a thick and heavy encapsulation.So the first experiment is 10mm of paraffin all around the part... with no effectWill it be dangerous if i pot it into ten liters of parrafin ?Is this a good idea ?

author: jonpaul
author_rank: Super Contributor
timestamp: November 01, 2020, 03:12:53 pm
content: Bonjour Monsieur,Parafin is flammable so a fire hazard in case of fault or short ckt.Use only fire rated potting, epozy or silicon rubber intended for such use.The potting will not have much effect on noise or distortion unless the toroiid is defective, loose core strip.Bon chance,Jon

author: Yansi
author_rank: Super Contributor
timestamp: November 01, 2020, 03:23:14 pm
content: Also, by potting the transformer, you likely decrease its cooling capabilities, so it may overheat.

author: Coordonnée_chromatique
author_rank: Frequent Contributor
timestamp: November 01, 2020, 03:43:08 pm
content: Quote from: jonpaul on November 01, 2020, 03:12:53 pmQuote from: Yansi on November 01, 2020, 03:23:14 pmEvery transformer is noisy :https://www.plitron.com/news/low-noise-toroidal-technology/The parrafine is used as a dielectric coolant in large transformers :https://www.electrical4u.com/transformer-insulating-oil-and-types-of-transformer-oil/Thanks, but i'm more interested by the efficacy of the material barrier.

author: BravoV
author_rank: Super Contributor
timestamp: November 01, 2020, 03:48:52 pm
content: Quote from: Coordonnée_chromatique on November 01, 2020, 02:10:13 pmQuote from: Coordonnée_chromatique on November 01, 2020, 03:43:08 pmI guess you already answered your own question, aren't you ?Case closed ?

author: Coordonnée_chromatique
author_rank: Frequent Contributor
timestamp: November 01, 2020, 03:56:15 pm
content: Quote from: BravoV on November 01, 2020, 03:48:52 pmSorry but i don't know what you mean, the material flammability is a very minor consideration when we talk about the damping of sound waves, but i was expecting some isolation issues or bad skin effects with the AC voltage.

author: schmitt trigger
author_rank: Super Contributor
timestamp: November 01, 2020, 04:04:34 pm
content: Having worked in a factory making fluorescent and HID ballasts, the best noise-deadening potting compound is sand-filled bitumen. By volume 30% sand.However, to mix and pour correctly, it has to be heated between 135 to 145 degrees Celsius, and you have to do it in a well ventilated area.

author: sandalcandal
author_rank: Unknown
timestamp: November 01, 2020, 04:08:44 pm
content: Since it hasn't been mentioned, I've read hard potting of magnetics which mechanically restricts magnetostriction or just shrinks during curing (thus inducing mechanical stress on the core) results in greater magnetic losses.No personal experience with hard potted magnetics though so maybe someone else can comment. I don't think paraffin is likely to cause issues due to how soft it tends be be however.Paraffin is quite often used for potting in experimental/hobbyist high voltage applications. Searching 4hv.org (dead but once very active forum) and highvoltageforum.net be more helpful. As Jon said however, not ideal, especially for anything left unattended under power.If sound is the primary issue and replacing the magnetics with something designed to produce less noise isn't possible then focusing on acoustic isolation e.g. damping pads, foam, thick enclosure might be another path but I don't have any idea if it's likely be be more effective or not.

author: sandalcandal
author_rank: Unknown
timestamp: November 01, 2020, 04:12:47 pm
content: Quote from: Coordonnée_chromatique on November 01, 2020, 03:56:15 pmI don't know what your maximum voltage or dv/dt is but paraffin wax as a dielectric has long been used for potting >100kV, MHz level systems in DIY HV without apparent issues.

author: Coordonnée_chromatique
author_rank: Frequent Contributor
timestamp: November 01, 2020, 05:21:23 pm
content: I must admit that a large quantity of highly energized highly flammable liquid is not the best idea in a houseQuote from: schmitt trigger on November 01, 2020, 04:04:34 pmToo hot for me, have you tested some doped concrete, it is really cheap and you can improve the self damping of the material by adding some recyled rubber tyre granules ?https://gezolan.com/en/products/black-recycled-rubber-granules/Quote from: sandalcandal on November 01, 2020, 04:08:44 pmI can't mesure the soundfield in 3D, so i'm focusing on the souce in the nearest field as possible, as you can see the vast majority of energy is in the very low frequencies, so nothing will stop it except a radical solution like thick walls.https://sndup.net/3sh6/Hummer.flac

author: Coordonnée_chromatique
author_rank: Frequent Contributor
timestamp: November 01, 2020, 05:31:05 pm
content: I'm not totally right, the most disturbing harmonic is at 1K.https://sndup.net/4jr6/Hummer2.flac

author: Coordonnée_chromatique
author_rank: Frequent Contributor
timestamp: November 01, 2020, 05:43:00 pm
content: My analysis is pointless, the NF is damn too high