Ian Iveson wrote:

Pooh Bear wrote

There is so much wrong with Ian's post below that after considering it I'm not
going
to even attempt to reply !

Cast and pressed cores my arse !

No, it's the previous post where I was a bit wrong, in that although some cores
use cast material, casting is not the process used to form the core. It is those
R-cores, cast and then wound, that I noticed have been commonly available for
some time. I have not been able to find any R-cores that are pressed, although
pressing is a common way of making other shapes of core.

Are you confusing pressing and stamping by any chance ? EI laminations are stamped
for sure.

As for casting, it plays no real roll in the production of GOSS. The material is
actually *rolled*. Sometimes called CRS ( cold rolled steel ).


Only small cores are pressed, such as for SMPS as far as I have been able to
discover,

Yes indeed. I don't know why you wanted to bring ferrites into this discussion. I
wasn't even sure if that was what you meant.


and I guess that R-cores are only feasible when they are relatively
large.

Really ? They start at about 15-20 VA.


OTOH, I still have not determined how the legs of a strip-wound R-core are
clamped or bonded. Perhaps they have a pressed jacket? Then the final core
production process would be pressing.

Uh ? The strip is wound and kept in shape by spot welding IIRC.


You may notice that I am asking questions, and you don't know the answers
any more than anyone else. That's OK, I don't expect you to know much about
production technology.

Eh ?

It's just you might have saved me the effort if you
hadn't pretended you do. You may find some of your time better spent finding out
the truth and giving it some thought.

I've used quite a few R-cores and I know plenty about their manufacture thanks.
Right down to internal safety margins and optimising winding area for lowest copper
losses.


Just to recap, you said that production of toroidal transformers is labour
intensive and you wondered, given the advantages of R-cores, why they are not
more widely used. You suggested they are a recent invention.

They are recent in relative terms.

In fact the production of toroidal transformers is no more labour intensive than
that of other kinds.

Utter nonsense.

Of course anything can be made in a more or less labour
intensive way. Take Patrick's EI transformers, for example, which are far more
labour intensive than the average toroid. Toroids actually favour machine
production, as Patrick testifies. They are especially hard to produce by hand.

R-core transformers have been fundamentally more difficult to produce.

Some aspects maybe.

Whereas
you can muddle through with a toroid, the same can't be said of an R-core. The
core itself presents serious manufacturing problems,

Transformer winders *buy* the cores ready made ! You *have* to use the dedicated
machiney - they realistically can't be hand wound.

in contrast to a toroidal
core which is a doddle. It is not a matter of invention, the principle is
obvious. It is a matter of solving the difficulties of production.

Casting or pressing are processes which would normally be used to create such
shapes.

What !!!!

Winding is pretty much the hardest way of making them. The only
fundamental reason they need to be wound if they are made of electrically
conducting material is to reduce eddy currents.

What steels used in cores have you come across that don't conduct ?

It also happens that GOSS is
easier to make thin, and amorphous strip can *only* be made thin, so winding or
stacking makes use of convenient raw materials.

That doesn't make any sense.

If you are not willing to learn, you may as well ignore my posts. If you can
contribute to my questions I would be grateful. Posturing will get you nowhere
in my estimation.

I'm certainly not going to learn anything about transformers from *you* nor do I
need to ! You have some very strange ideas.

Graham