Transformer insulateing tape?

You said AC fed.

Jeez, you didn't even have to mention AC line if it was not a line transformer.

If it is a pot core, you may find a nice operating freq at 56-59kHz.

Generally about 57kHz. I also assume that you probably bought the same line of pot cores that the whole industry generally uses. YMMV.

Shouldn't matter, I know... but if you get it going at 60kHz, I'd almost bet money that it gets more efficient at the numbers I gave you.

That is from almost a decade of characterization. Could have been our circuits, but it was that way on several different designs, so I lean toward the core being 'happy'.

Also, I rarely need a gap of more than a few mils, but you are doing a flyback IIRC.

Will your primary be parallel wound (flat) or are you going to fashion an in-house Litz by twisting them into one stranded line? (YES, it IS Litz at that point and tests will prove it) Do not over twist. It should be no more than needed to keep them grouped. Use double strength mag wire insulation type. A twisted set will likely yield a bit more efficient operation than the flat wind will. Stacked bobbin breaks? or stacked winding schema where you stack by hand?

Also are you saying "stacked" as in would one over the top of the other, or stacked as in one at the bottom of the bobbin space, and one above that with the primary underneath?

The volts per turn choice looks great

I'll assume the misunderstanding is with my use of "DCM" I'm referring to Discontinuous Conduction Mode or complete energy transfer.

The converter is fed from the AC outlet but its not for APFC, its rectified and filter the tranny will see between 110Vdc to 185Vdc with about 20% ripple.Technically I guess the switch turns this to AC at least as far as the flyback inductors are concerned.

I'm using an etd/29/16/10 ferrite 3C90 this one from newark.

I'm using the 13 pin former that's shown in the data sheet.

Yes I'm hand twisting the wires and thanks for the tip about being to tight I had forgotten about the optimum twist per inch.

Here's is a picture of what I mean when I say AC stacked windings.

My minus output windings are configured the same as the positive ones shown in the pic. I'm using two pins for the return.

But I am also layering the primary 2 layers 1 as the first layer then the secondaries and bias winding then the second layer of the primary. This is supposed to increase coupling and reduce leakage.

he

So you did. If I'd read through the URLs that you gave, or clicked on the links, I'd have realised that you were directing the OP to Farnell. Sorry about that, but I usually treat URLs as meaningless character strings that point to real information, thus saving myself the time required to parse them.

Americans are particularly prone to do this.

The polyester backing film is nominally 1 mil thick, but with the adhesive it builds up to 2.5 mils - nominally 63.5 microns. We used it between layers of round wire, so presumably some of the adhesive was squeezed sideways into the gaps between the wires.

The electronics industry is infested with dimensions expressed in bizarre fractions of an inch and I don't think that tapes and films are any worse affected than - say - the lead pitches on ics and connectors.

We checked our tape and film thicknesses with micrometers, some of which were calibrated in microns, others in thous (thousandths of an inch or mills). Both gave the same margin of error.

-- Bill Sloman, Nijmegen

Yeah... I think ours was that or perhaps 3c85.

Anyway, we found that happy point over several product iterations we had that were fired in completely different manners, so we were pretty convinced it was the transformer.

Yeah, in a transformer especially, a tightly twisted set of wires actually introduces detrimental effects.

In a cable bundle it usually amounts to a mere binding of the cables, usually causing more tension on one than another. Not much problem with a short run inside a chassis, but a major factor on say a 150' long cable for a jolly green giant or the like. All the stresses have to be normalized.

Nope. Plenty of variations about.

I had a lot of .5 mil tape with .5 mil adhesive.

The taut use of the tape will cold flow it as far into any crevices it can. Then baking 'relaxes' it 'in' further.

This info helps quite a bit.

For a single unit you might be able to scavenge the yellow tape from a junked switching power supply from from a computer. Some peel apart if you smash the ferrite, some don't. Do avoid plain electrical tape- it creeps and "pressure" inside a coil with hundreds or thousands of turns can sink right though it.

Other sources of insulating material are in your junk pile. Those white plastic sheets that replace fish paper to keep pins from hitting close fitting chassies can be cut up and used. Junked computer power supplies have lots of goodies like this inside them.

It works fine for quick and dirty projects. secure it with scraps whatever tape you can peel from a transformer or inductor and you're good.

You would wind bobbin-less transformers on old newspapers if you wanted to.

The trick is to wind many coils at once next to each other, stop the winder and insert a sheet of [anything] and wind the next layer and repeat.

When done with all of that, you saw or cut the individual windings apart. Trying to make one coil that way would be almost impossible as the windings would slide off the edges and the insulating material would collapse at the edges as well.

Even if it would, the adhesive is pressure sensitive, and will have polymerized, and be unusable for subsequent use, unless you wanted to do it without the adhesive.

No, I would not.

Had you read the thread, you would have found that it was already covered. And the trick is not to "wind many coils". The trick is NOT to wind too many coils such that the mag wire insulation resistance gets compromised by the last turn being to near a lower voltage turn, such as the first or one of the early turns.

Also, he is winding ONE unit, not doing a production run, and with small transformers, especially HV jobs, one at a time is only slightly slower but yield a far higher prime pass yield.

If you wind on a gang, you place several individual bobbins on the winder, and when you are done, they all come apart just fine. No cutting and certainly no sawing.

It is a bobbin. It has bobbin faces, and if you do not know what a bobbin face is, you should not be expounding on transformer winding.

Hello,

A flyback needs low spreading inductance (to avoid excessive loss in the snubber). You don't want large barrier between your windings. Don't trust hobby tape, but try to get polyimide tape (brand name Kapton). It isn't cheap, but does the job.

Best regards,

Wim PA3DJS

Kapton is usually too thick and is cumbersome to wind with. the tapes that have been suggested are the right tapes to use. Polyester tapes will get the windings as close together as they can be.

Thanks for the suggestion.

I have two boxes of junk I can dig through. This is likely what I'll do next order to Newark I 'll get the proper tape for future projects.

pes

Hello Archimedes' Lever,

I assumed that he needs the tape to separate primary and secondary windings only. For example:

First half of primary turns in a layer two/three layers tape for safety insulation complete secondary winding two/three layers tape for safety insulation second half of primary turns in the last layer.

In such an arrangement, kapton / polyimide is not that difficult to use (from experience), however I fully agree that suitable polyester tape can do the job (cheaper, easier to work with and easier to get). The reason for mentioning the polyimide was that he can be almost sure to have something that is OK.

Before making final decision, he also has to find out the expected over voltage category and whether he requires single or double/ reinforced safety barrier in his transformer (as this also determines the required clearance and creepage distance).

Best regards and thanks for the info,

Wim PA3DJS

T to

ll

ng

BOBBIN IS WHAT YOU WERE DOING LAST NIGHT YOU SICK TROLL

DON'T WORRY ONE OF THESE DAYS YOUR LITTLE CABLE CONNECTION WILL BE GONE AND SO WILL YOU

I AM PROTEUS

On a sunny day (Sun, 20 Jun 2010 07:43:29 -0700 (PDT)) it happened Proteus IIV wrote in :

An other Apple user flips out.

FYI Steve Jobs wil die one day.

Yep there is a reason I KF anything from google groups to much spam and nutjobs. I rarely see any spam or wackos unless someone quotes them. There are some decent posters from google but far and away the junk is ridicoulous. I dont know how anyone can even keep track of anything in GG it gets spam bombed several times a day.

Their is already enough borderline wackos here I can live without a further contribution from Google.

Commonly:

This must be a usage of the word "bizarre" with which I am as yet unfamiliar.

;-)

We used to use "friction" tape for that kind of thing, haven't seen any for a while. Anyone have electrical data for "hockey" tape?

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