Transformer insulateing tape?

I like using 3M #56 polyester tape. I think you can get it from Newark, but you'll need to cut it yourself to proper width. If this is for commercial use, there are companies out there that will precision slit the tape for you. See if you can find some China knockoff tape.

--
Mark

3M transformer tape. Fish paper.

That is the product line. There are actually several vendors for that

3M tape, and even other makers, but 3M seems to be the most widely used by the industry.

You should utilize a slightly wider tape than the bobbin spool width. (about 40 mils) and you should never wind all the way to the bobbin face with each layer of wire. There should be several wire widths for fine wire. Larger wire will not likely give wire insulation issues because of the few number of turns. Never place more than about 150 turns per layer with fine wire (no random spool fills). Without insulation between turn

151 (approx) and the starting series of turns, the voltage difference can/will cause a breach of the insulation and fail the xformer. Finally vacuum impregnation with on of these if high repeatability and reliability are desired:

AC-43 is a common choice. It boils in a vacuum, so you have to bring it up slowly until that stops (it will eventually), then you can bring it up to nearly a full (industrially speaking) vacuum.

Then bake them out. (you should bake at 60C for about a half hour before impregnation as well to eradicate water.

It is very easy to find a vendor that will slit custom widths of that tape. They buy it in VERY wide rolls just for that purpose.

I think Larkin mention

, seems reasonable for small qty.

Cheers

You'll end up with a lot of leftovers (maybe $500 worth) if you just want part of a roll.

Here's a roll of dubious polyester tape from a dubious source for less than $3 delivered. They don't even say how thick it is.

Best regards, Spehro Pefhany

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Spoke too soon,

Your looking for Polyester Film Thermo setting tape, works like Diamond craft paper.

3M 54

Try

Any of the 3m tapes you'll have to buy in qty. I have yet to find open cases that you can buy a few rolls.

Cheers

Bullshit. Most of the vendors that *do* offer custom slit widths also have a huge line of standard cut widths.

The custom jobs are for those that know what they want, and are ready to make a minimum purchase and pay a tooling fee to get it.

Also, if one *does* make a single custom order, they do not require that they buy the whole roll, because they use the remaining bit to make standard cut widths. THEY buy those widths pre-cut in bulk, but when left with surplus on the lathe, they slit what remains up to sell as well.

Hmm Newark has a nice selection. I wish I would have thought about this when I placed an order last week for some caps and fuses and Fets etc.

I was hopeing just to get something locally and I think I may have found something.

This is available at my local homedepot.

Scotch® Premium Vinyl Electrical Tape 88-Super

Hoprfully the url doesnt get squashed.

Tinyurl if it gets squashed

Similiar charecteristics to the mentioned tapes.

This is just for a single PSU I have no intention of selling it or mass produceing it. I'm just after safe and reliable.

Would the super 88 tape be suitable under the mentioned circumstances?

This at least has specs and is available in single(2) rolls

Cheers

No! NOT vinyl. POLYMER. for high temp, high voltage, and flammability reasons. Let alone the 1 mil thickness (even 0.5mil is available)

As has been mentioned here, 3M's yellow polyester film is popular.

Farnell/Newark stocks it in three widths - 12mm, 19mm and 25mm. You can order a sinle 66 metre roll for a couple of dollars. The Farnell order codes are 726-977, 753-002 and 753-014.

If I remember rightly, the tape is 60 micron thick.

-- Bill Sloman, Nijmegen

I already posted the Farnell links, oh, great idiot that never reads the goddamned thread.

Folks around this industry use mils to describe thicknesses. Especially on things like tapes and films.

Granted microns can be used, but it has a lot less familiarity among folks, and also a lot less ability to look at something and declare a number. I can do mils fairly accurately, but calling something "1 mil" is a lot easier than trying to tag it with a micron numeric where the margin for error is higher.

are you making one transformer or many, and if so, are you using a coil form?

Just one. I'm using an ETD29 core with Bobbin. I've made several transformers for LVDC less then 50Vrms.This is my first transformer from scratch for a line powered supply. I usually just buy or get samples from places like coil craft, but I want a multiple output flyback 50W small light weight and I've got this down too fitting into a 5" x 3" x2.2" in enclosure. I know I could buy one for $50 to 100 plus but that's no fun;-)

I will be the only one using it. Its main purpose is to save bench space and to save me the hassle of having to continually dig out 317's

7812 or 7805's when I'm working on something that requires multiple voltages.

So its not going to be tested for EMC compliance (but I do have a line filter) or Hi Pot tested etc.

I originally did it up to operate of my Bench top PSU with an EFD20 core/ bobbin set (for 24W ) but I want to be able to eliminate the larger Bench top PSU so I don't have so much clutter on the bench.

Eventually I'll get around to building a half decent sized bench, but I just finished installing and painting seven new interior doors. That's my renovating fun for a couple of months anyway's. ;-)

Solid-core door plus off-the-shelf metal leg assemblies is what I did. ...Jim Thompson

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Primary turns, wire size desired

Secondary voltage and consumption level desired so that the secondary wire size can be determined/optimized.

Form factor

Post that.

[ snip]

I just got some hollow mdf doors, I kept my pine jambs I refinished them last year they turned out nice.

They actually look really nice after two coats of off-white semi gloss. They contrast well with the oak trim and pine jambs. I thought I might have made a mistake in not getting pine or oak doors $$ but it turned out well. There's enough wood in my house as it is.:-)

I cant complain for $250 after all is said and done.

Years ago for non critical apps, we used wax paper for layer insulation for winding multilayers..

We also had a back yard solution for potting coils that seem to work well. We would use a small jar of turpentine and place a soft rubber or PVC from something crap into it. Place a rag around the entry point to keep it from drying up while the base material was getting solidified into a pliable paste!. We'd used that to pot coils, do filling repairs etc.

Some where along the line, liquid tape sprung out from that..:)

Primary inductance 300uH, Dmax 0.4, switching frequency 60kHz +/- 10% Operateing mode (if it isnt already obvious) DCM.

N= 6 NP= 56

Gap 1mm

I used a current density of 5A/MM2 for the primary resulting in conductor area of 0.181 mm2 or larger I plan on useing 3x 30AWG for the primary.

Output voltages AC stacked +12 and +5 both at 2A countinous each.

Both at 3.55Arms the 5V winding will also carry the upper 12V load current.

Stacked windings translate to 9 turns 1.375 volts per turn. The five volts is regulated.

I used a current density of 6A/MM2 (few turns) conductor area for the

+12 is 0.592 mm2 twice that for the plus 5.

Negative output voltages -12 and -5 both at 0.6A countinous each.

Same winding startegy as above and turns rms current 1.06A