Tape for insulating windings in a high frequency transformer. - Page 1
Forum section: electronics / projects

author: Picuino
author_rank: Super Contributor
timestamp: July 08, 2021, 12:40:30 pm
content: What is the best tape for insulating windings in a Flyback transformer?Frequency = 130000 HzV_input = AC mains, 311Vdc rectifiedcan any polyester tape work?

author: bob91343
author_rank: Super Contributor
timestamp: July 08, 2021, 09:44:09 pm
content: Mylar tape is very common. It's available in various thicknesses for different voltage breakdown ratings.Its dielectric constant needs to be considered.

author: Picuino
author_rank: Super Contributor
timestamp: July 09, 2021, 11:22:13 am
content: Thank you.I can't find mylar tape on RS-Online, Digikey or Farnell.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 09, 2021, 12:38:26 pm
content: Mylar is DuPont's trade name for PET film. This is also called polyester, so you are on the right track already.

author: TimNJ
author_rank: Super Contributor
timestamp: July 09, 2021, 12:41:09 pm
content: The OG tape is 3M 1350-1. (1mil thick polyester film.)There are many other manufacturers

author: Faringdon
author_rank: Super Contributor
timestamp: July 10, 2021, 05:03:16 pm
content: Also, if you go to power integrations website, they show examples of SMPS and give the full transformer BOM, including the tape

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 10, 2021, 06:42:52 pm
content: Think this is the one I got, years ago... a roll lasts a long time.https://www.digikey.com/en/products/detail/3m/56-YELLOW-1-2-X72YD/1819325Polyimide also quite good, the silicone adhesive stuff is a bit less tacky (particularly around oils e.g. from handling) but doesn't flinch at all under soldering heat, it's quite versatile.Tim

author: floobydust
author_rank: Super Contributor
timestamp: July 11, 2021, 08:58:37 pm
content: There is a safety requirement for the insulating tape. With transformer inter-winding insulation, there are many agency approvals for temperature, flammability, CTI, corrosion etc. leading to the common polyester 130°C "UL yellow tape" you see used as the lowest cost option.https://www.3m.com/3M/en_US/p/c/tapes/electrical/3M electrical oem tapes ul matrix

author: jonpaul
author_rank: Super Contributor
timestamp: July 12, 2021, 07:33:52 am
content: Salut Picuino,We manufactured HV and SMPS magnetics for decades. Freq 25 kHz..500 kHz.You cannot use just any mylar tape,1 mil tape is too thin for power windings.Our std tape is 3M56, 2 mil Mylar polyester, with 0.2 mil adhesive, UL rated and temperate class 130 (or 155) I forget.All the usual electrical insulation distribs have this in standard widt .25...5...1...2" or can order it custom width.Putup is 72 ydshttps://multimedia.3m.com/mws/media/37390O/3m-polyester-film-electrical-tape-56.pdfBon chanceJon

author: Picuino
author_rank: Super Contributor
timestamp: July 12, 2021, 12:12:29 pm
content: Thank you very much everyone for the replies.

author: TimNJ
author_rank: Super Contributor
timestamp: July 12, 2021, 02:48:43 pm
content: Interesting about the recommendation for 3M #56. I suppose that really must be the "original yellow tape".https://multimedia.3m.com/mws/media/37390O/3m-polyester-film-electrical-tape-56.pdfhttps://multimedia.3m.com/mws/media/93191O/1350-1-1350-2-flame-retardant-tape.pdfFor what it's worth, if you compare #56 and #1350-1, the main difference is the latter is designated as flame retardant and the former is not. Only thing obviously different is the adhesive type.

author: jonpaul
author_rank: Super Contributor
timestamp: July 12, 2021, 05:33:57 pm
content: Rebonjour, YES 3M56 is the original yellow tape....Beware of low quality cheap Chine knockoffs, NOT the same property or quality as GENUINE 356!the old stock tapes (epay, gray mkt) may have ripples in the roll or uneven adhesive, especial if stored in hot or damp area.Avoid old stock for serious use!Flame retard tape is seldom used.Have built prod qty SMPS transformersused in UL, FAA and medical device approved application.Used 3M56, some time many layers, some parts required vacuum varnish impregnation. (Dolph)Distributors for 3M electrical:EIS = Electrical Insulation SpecialistsEssex BrownellSuperior EssexGraybarBon chanceJon