Pooh Bear wrote:

Patrick Turner wrote:

Pooh Bear wrote:

Since these came up in passing, I thought I'd post some info links.

They are *very* good btw. Better even than toroids in audio gear.

http://electroassemblies.com/r-core.htm
http://www.custommag.com/products/r-core.shtml
http://www.kitamura-kiden.co.jp/english/products_e.html
http://www.lenco-elect.com/r_core_transformers.htm

The O-core may be slightly better still but i haven't had the chance to try one
yet.
http://tortran.com/O-Cores.asp
http://www.manufacturingcenter.com/d...02fivestar.asp

Graham

Here is what one guy at one address above said about R cores, and I place my
comments within the text.......

I'm afraid your formatting got very garbled so can I ask you to repost ? I suspect
tabbing is the problem

Power Donuts

Rewinding at the core of these toroid transformers

Note this is about the newer O-cores ( not R-cores ) btw.

From what i see from the above addresses you give then the R core is wound through
the pre-wound bobbins. I quote...

snip quote

This means the core must be a long tapered variable width strip of GOSS sheet

To make the core it is.

and inserted around the wound cores presumably by a machine and with no sharp bending
of the material which would hurt the magnetic properties.

No, that's the clever bit. The core is made and the bobbins are assembled over it. They
are of 2 part construction. You need to see one to work it out, or maybe the links I
provided will point you in the direction of an example. They are really clever.

No need for me to un-garble the formatting. I just copied and pasted from the references
you gave;
if you have a look you'll see what I found.

For R cores I conclude the bobbins are in halves which clip together around the wound up
core.
They then can rotate the bobbin because its like as if its on a shaft, which is a straight
portion
of the core, and I guess that's how they could wind the wire without having to
pass the core strip in through the hole in pre-wound bobbins.

Machines would make it possible for easy core winding, and easy wire winding, perhaps
easier and faster than a toroid, done in perhaps 50 trannies at a time.

So when these dudes say its all more expensive that a toroidal with rectangular core and
better and its worth it, consider that they pull our legs and in fact the production of the

cores and wound trannies may be cheaper than any other form of transformer with regard to
labour. There would be waste when cutting the tapered strip of GOSS. But I bet the machine
does the best it can to reduce waste to negligible amounts, and offcuts might be used for
smaller transformers. Large volume makers pay a shirtload less that I do for their raw
GOSS sheet.
I pay usd $9.00 per Kg for annealed GOSS E&I lams at 50Kg minimum order.
But I bet these big makers pay only $3, so a large tranny with 40mm dia core may have only
4Kgs, or core material that cost the maker $12!
If they had to waste 50% to get the taper then they only threw away $6.

So let us NEVER cry a single tear for the mass makers who complain about the costs of raw
materials and
labour; they hardly use much of either; costs are with machines, capital investments and
absurd wages and conditions for the bosses.

So from what I see of R cores and O cores, the product should be cheaper, not more
expensive than all
the alternatives.

Patrick Turner.



Graham