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.

No I'm not. You are not very good at reading.

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

Of course GOSS is not cast. If it is not cold-rolled or cold-drawn it is not
GOSS. Not *all* cold-rolled steel is GOSS, however, so CRS is not a sufficient
description. Neither is cold rolling the *only* method of making GOSS, although
it may be the only one used for GOSS transformer laminations.

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.

Not a good enough excuse for saying they don't exist. I haven't mentioned
ferrites, either. You still haven't looked up amorphous, have you?

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

Really ? They start at about 15-20 VA.

Yes, really. Assuming you mean mains-frequency transformers, 15VA requires a
relatively large core compared to the pressed cores that I have found.

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.

Hmm, maybe. Welding is bad news for GOSS though, and for insulation, so if that
is the only way to do it, it detracts from the advantages. I wish I had enough
confidence in your knowledge and your discipline to believe you. Any references
to support your claim that spot welding is always used, and is sufficient
without any other form of bonding or clamping?

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 ?

I said that's OK, I don't expect you to know much about production technology.

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.

You don't need to know much about the production of an R-core to be able to do
those things, and I have little confidence in your estimation of what you can do
anyway. You often say you know things, but rarely say what you know, and when
you do it is often nonsense you read in a magazine, it seems to me.

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.

They may be recent, we don't disagree there. They are not a recent invention,
however.

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

Utter nonsense.

It is utter nonsense to suggest that the production of one commodity requires
more labour than another, in general. Labour intensiveness depends on the
technology applied, not on the commodity. It is also nonsense to say that some
products can be made many at a time, and others only one at a time, for the same
reason. You are obviously not a production engineer, and you have no experience
or knowledge of production control or management.

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.

Of course. It only takes one aspect to be difficult to make the whole thing
difficult though, doesn't it? You are squirming.

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.

A non-sequitur if ever there was one. It's you that said that toroids are labour
intensive. Cores don't grow on trees, they have to be made before they are
bought. We were talking about the production of transformers, not just the
windings. Of course R-cores are relatively easy to wind. I have suggested that
must be offset against the relative difficulty of making the cores.

Patrick realistically hand-winds. When it comes to labour-intensive methods, EI
is easiest. Given a long strip of GOSS and some wire, I am sure that Patrick
could make a good toroidal transformer entirely by hand. I bet he couldn't make
a decent R-core though.

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 !!!!

Tell me which bit you don't understand, and I will consider explaining it to
you. "Such shapes" refers to the R-core shape, BTW, which is not clear the way
you have quoted me.

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 ?

None. Why do you ask? Steel is not the only material that can be used to make a
core. Also I don't actually know whether amorphous is a good conductor, which is
why I asked. Do you? If you happen to have an amorphous core lying around,
perhaps you could check.

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.

Which part don't you understand? I will consider helping you if I can.

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.

Many truths seem strange to you, I am sure. Your life could be wasted if you
consistently refuse to learn on the grounds that you think you already know.
That is an illusion born of ignorance. It may have been blissful for a while,
but you are gambling with life. You may actually *need* to know something
sometime.

cheers, Ian