Transformer tape, what is this tape called?

one of my pass-times is dis-assembling switch mode transformers from junked TVs.
So I find this arrow in image

What do you call this tape ? not the yellow tape, but the tape on the end.whats it called in a catalogue and where to buy it ?
It looks like some sort of cardboard tape impregnated with varnish or similar?

I guess its used for filling in the edge of a winding. But I wonder if it helps in reducing
fringing magnetic flux from the winding below it too ?

you ask a very very good question.

You cannot buy that tape anywhere in the world....literally.

Its called Marghin Tape, and what of it that exists, is usually made by whichever transformer manufacturer is using it.

...you can make it yorself by cutting along insulation tape .

It is solely for insulation purpose....because otherwise the creepage distance between primary and secondary would be too close.

....Bit i gaurantee you, you will not find that tape anywhere.

3M and lodestonepacific.com are said to sell it....but they don't

Many new trafos dont use it cuzz they use furukawa insulated wire, (TEX-E)and then you dont need the margin tape

ok,thanks.I see your other thread now..https://www.edaboard.com/threads/218226/
I guess I can DIY with a bit of varnished thin cardboard and glue. I think I need this for the latest transformer I'm winding because high voltage turns will be
passing where terminals for low voltage is on the former. hmm..but what type of glue....i'll have to check what I have...

3M is a great company, but difficult to buy from in my experience, even when I lived next door. Typically, you have to go through a distributor for the correct market segment as defined by 3M. In other words, if you want to buy a double-stick tape used in medical practice, you cannot get it through an automotive distributor.

As for the tape you need, have you considered fiberglass or nylon tapes used for reinforcement (hobby suppliers) or hem tape from a fabric/sewing store. Hem tape can be made of nylon, polyester, polyamide (fusible) and maybe some other materials. Some of it comes sticky, usually both sides. If you get tape that is not already sticky, have you considered a spray adhesive, like Duro, 3m #77 (and other numbers), or art supply sprays. A light coating of the spray will hold it in position and will not affect penetration of the final varnish.

John

I wouldn't recommend cardboard but you can buy fibreglass tape from places like Farnell which should be suitable.

Keith

woops hold on...i am not sure if it is margin tape now...becase surely it would have been on both sides..........i think you are right in saying that you need that HV clearance.


Sounds like you are after HV glue....i think all glue is same as far as insulative proprties.

But some glue is acid based i think(?) and can dissolve metal wires over time.(?)

Another simple way to create "Margin Tape" simply buy mylar sheets of appropriate thickness and cut in narrow strip of required width.

Probably whatever it is, you can get the same effect with enough layers of mylar/kapton tape.

3M fiberglass tape is good stuff and you can find it at local electric supply and
sometimes hardware / home depot type stores. Painting it with some electric
varnish might help make it stiffer and improve breakdown further.