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

"Pooh Bear"
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.


** WHY post this in a group dominated by Tube Heads ??

Don't you know Tube Heads loathe toroidal and R core transformers ??

Tube Head logic is that since toroidals did not exist in the golden era of
tubes ( 1920 to 1965 ) it is pure sacrilege to even suggest using them now.

Just ask the Turneriod PITA.




........ Phil


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

Phil Allison wrote:



** WHY post this in a group dominated by Tube Heads ??

Don't you know Tube Heads loathe toroidal and R core transformers ??

Tube Head logic is that since toroidals did not exist in the golden era of
tubes ( 1920 to 1965 ) it is pure sacrilege to even suggest using them now.

That would also rule out those boutique and other modern capacitors as
well. Back to wax paper caps..... :-)

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.......




Power Donuts

Rewinding at the core of these toroid
transformers

Two reasons have been cited to explain the
efficiency of toroidal power transformers over
conventional stacked lamination designs:

1.The windings are placed directly on the
core, distributed over its entire
circumference and minimiz-ing the
amount of copper wire in the windings.
By comparison, in a stacked core
transformer the windings are placed on
bobbins surrounding only the core legs, thus producing a
larger diameter winding that
requires a greater amount of copper wire. As a result,
the winding resistance and losses
are higher than in the toroid.

I'd have to agree the R core or O core for toroids is better than rectangular
sections.
But one still must have sufficent iron to get low core losses and quiet operation
with rectifiers connected.


2.Cores used in toroidal line power transformers consist of
grain-oriented silicon steel
strip, wound into a flat tubular shape under controlled
tension.

Unless you have a special winder for toroids with rectangular section or for Ocore
section it is difficult
for the DIYer to use O cores.
But not impossible, and best results would be with Ocores using a hand held shuttle
to place turns slowy onto the
core and without the sharp bend around the corners.

The primary and
secondary windings are placed uniformly around the core,
with the magnetic flux parallel
to the grain orientation in all parts of the core. As a
result, there is a very low emitted
(stray) field. The core may also operate safely at 15-16
kilogauss, as opposed to 12-14
kilogauss common to an E-I design. Additionally, the core
ring draws a much lower
excitation current than a core made of stacked
laminations.

For PT in class A tube amps with rectifiers, one would never try to run at
above 0.9Tesla, no matter what the core.

Besides efficiency issues, toroids are physically smaller and
lighter than traditional
transformers, making them suited to companies pursuing
reduction in size of their products.
So, how does one improve on the toroid transformer?

The engineers at Alpha-Core Inc, Bridgeport, CT, say they
found an answer in the
construction of the core. The circumference of a circle is
about 12% less than that of a square
with the same area, and 18% less than a rectangle with the
same area and a 1:2 side ratio.
The O-core transformer line begins with the silicon steel
strip and slits it in such a fashion that
when wound into a core, the resulting cross section is a
perfect circle rather than a square or
a rectangle. This further reduces the length of wire needed to
circumscribe a given core cross
section, resulting in further weight and loss reduction.

The O-core does not require epoxy coating, which adds 20-30 %
to the cost of a bare toroid,
to protect the copper wiring from being nicked or cut on the
corners of a rectangular
cross-section. Taping with 50% overlap is sufficient core
insulation, in turn permitting the use
of heavier wire at lower winding tension. The O-core design
also eliminates the barrel shape
of windings placed on a square core. Practically, the larger
total cross section of wire in the
core ID leads to a substantially higher VA rating based on
core weight. This means a higher
copper/iron ratio than ordinary toroidal transformers, in a
smaller, lighter and more efficient
package.

The best toroids have permeable insulation which is soaked with varnish and then
all baked and the
"barrel" shape of the windings around the rectangle don't matter.
I can't find any cheap toroids wound with varnished windings so they remain quiet
with rectifiers so I will stick with E&I laminations.



From what i see from the above addresses you give then the R core is wound through
the pre-wound
bobbins. I quote...
R-core Transformers are manufactured using
the unique rectangular core with round cross
section known as R-core. The special feature
of this transformer is that the core is gap less
and continuous. The winding is done on
special round bobbins on two parallel legs of
the core.

This means the core must be a long tapered variable width strip of GOSS sheet and
inserted around the wound cores
presumably by a machine and with no sharp bending of the material which would hurt
the magnetic properties.

Buying precut coils of core material for use to insert around per-wound coils would
not be very
practical and would be expensive due to a high waste factor unless each core turn
of GOSS was a
strip of one turn in length and had a join.

I would imagine the use of R cores to be totally impractical and irrelevant to
DIYers; too difficult, too expensive,
and relatively unavailable.

Many years ago keen audio nutters would simply wind a normal winding on a
rectangular bobbin
they made themselves, then if they could buy some GOSS steel strip material say
38mm wide in bulk,
then they would cut 3 metre long strips of such material and wind it round and
round the winding by hand.
The few joins would be distibuted and not affect the maximum permeabilty of the
material.
Even if the material wan't GOSS, but non oriented Sife, or NOSS, then there was a
big increase in permeabilty
because of the wound core without the grain direction change and joins in an E&I
core

The benefits of R and O cores lie in the mass produced article.

Meanwhile the most effective and easy cores for general use for all types of OPT
and PT for quality
small volume makers are C-cores or E&I laminations.

The GOSS E&I lams I get from Sankey Aust have max permeability of 17,000 when fully
interleaved,
and core losses in a 1KVA core with B = 0.9T is about 3 watts. Such a tranny well
varnished is utterly
silent at 500VA draw which includes DC production or 250VA.
Any increases in permeability above say 10,000 gives negligible reductions in
transformer temperatures
because the copper losses determine the temp once core losses become less than 1/4
of the copper losses.

Maybe I could use Eilor cores
http://www.eilor.co.il/Articles/Arti...&CategoryID=79

But these are even more expensive than the E&I lams.

Patrick Turner

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.

Graham

robert casey wrote:

Phil Allison wrote:


** WHY post this in a group dominated by Tube Heads ??

Don't you know Tube Heads loathe toroidal and R core transformers ??

Tube Head logic is that since toroidals did not exist in the golden era of
tubes ( 1920 to 1965 ) it is pure sacrilege to even suggest using them now.

That would also rule out those boutique and other modern capacitors as
well. Back to wax paper caps..... :-)

There are problems with toroidal OPTs used in PP amps due to easy saturation if
the DC
becomes slightly imbalanced.

Tube head DIYers don't like bloomin toroids mainly becaise they are so difficult
to use.
The last 500VA power tranny I wound by hand took 3 days with a shuttle passed
around the core
at about 1 turn per 45 seconds average.

All the toroidals I have purchased for PT have been noisy even unloaded, and way
too noisy
with a rectifier connected; their winding doesn't include proper baked varnish or
epoxy imprgnation.

When i see a tube amp with all toroids in it I shudder, and usually it is a crap
product fron China.

But on the other hand the toroidals from Plitron are very decent, if anyone can
afford them...

I compared Auricaps to plain chap MKP Wimas and heard ZERO sound change.

Patrick Turner.

Patrick Turner wrote:

robert casey wrote:

Phil Allison wrote:


** WHY post this in a group dominated by Tube Heads ??

Don't you know Tube Heads loathe toroidal and R core transformers ??

Tube Head logic is that since toroidals did not exist in the golden era of
tubes ( 1920 to 1965 ) it is pure sacrilege to even suggest using them now.

That would also rule out those boutique and other modern capacitors as
well. Back to wax paper caps..... :-)

There are problems with toroidal OPTs used in PP amps due to easy saturation if the
DC
becomes slightly imbalanced.

That seems to me to be more of a problem with the circuitry than the transfomer. If
you'd accept ss electronics even as a servo, the bias could be dynamically adjusted
to prevent any DC component.


Tube head DIYers don't like bloomin toroids mainly becaise they are so difficult to
use.

Eh ? What's difficult ? It's a transformer dammit. What can be difficult about that ?



The last 500VA power tranny I wound by hand took 3 days with a shuttle passed
around the core
at about 1 turn per 45 seconds average.

You wind your *power* transformers ? I can understand OPTs but really !


All the toroidals I have purchased for PT have been noisy even unloaded, and way
too noisy
with a rectifier connected

You've been buying the wrong ones. That's a non-existent problemas far as I'm
concerned. Crikey, I've found E-Is to be noisy for heaven's sake !


their winding doesn't include proper baked varnish or epoxy imprgnation.

Doesn't need it if wound properly.


When i see a tube amp with all toroids in it I shudder, and usually it is a crap
product fron China.

Association like that is nuts.

But on the other hand the toroidals from Plitron are very decent, if anyone can
afford them...

I specify Toroid International.
http://www.toroid.se/


I compared Auricaps to plain chap MKP Wimas and heard ZERO sound change.

No surprise there. For there to be any difference there would need to be a scientific
explanation why ! And there isn't. Essentially all plastic film caps perform
identically for coupling.

Graham

Pooh Bear wrote:

Patrick Turner wrote:

robert casey wrote:

Phil Allison wrote:


** WHY post this in a group dominated by Tube Heads ??

Don't you know Tube Heads loathe toroidal and R core transformers ??

Tube Head logic is that since toroidals did not exist in the golden era of
tubes ( 1920 to 1965 ) it is pure sacrilege to even suggest using them now.

That would also rule out those boutique and other modern capacitors as
well. Back to wax paper caps..... :-)

There are problems with toroidal OPTs used in PP amps due to easy saturation if the
DC
becomes slightly imbalanced.

That seems to me to be more of a problem with the circuitry than the transfomer. If
you'd accept ss electronics even as a servo, the bias could be dynamically adjusted
to prevent any DC component.

About 10 years ago there was an article on Electronics World which advocated the use
of a pair of differential mode opamps to adjust grid bias so that balanced dc cathode
current is maintained.
The circuit filtered out the signal from small cathode R current sensors.
Since most PP amps are class AB the cathode current in output tubes is never constant in
class AB
and the current in both tubes rise with signal, and its the balance that needs to be
maintained
and not total dc current which must be allowed to rise above the idle Ia which stays
fixed for the first few watts
of class A.
I tried this thing with discrete connected darlington pairs which worked great until i
added NFB
and then there was much LF oscillation.
Having cores with a small gap or with not extremely hig µ will allow some bias imbalance.

I usually place a bias balance pot in PP amps and the balance can be adjusted with two
leds indicating
bias balance when operating at equal brightness.
No need for the servo circuit.





Tube head DIYers don't like bloomin toroids mainly becaise they are so difficult to
use.

Eh ? What's difficult ? It's a transformer dammit. What can be difficult about that ?

I meant difficult to use in a transformer they would wind themself.
OK for RF where a few turns are involved but not with audio OPT or PT where many
turns are needed.



The last 500VA power tranny I wound by hand took 3 days with a shuttle passed
around the core
at about 1 turn per 45 seconds average.

You wind your *power* transformers ? I can understand OPTs but really !

I wind all my own iron wound components because I cannt find anyone selling trannies
wound how I like them to be wound, or they take too long, charge too much etc.



All the toroidals I have purchased for PT have been noisy even unloaded, and way
too noisy
with a rectifier connected

You've been buying the wrong ones. That's a non-existent problemas far as I'm
concerned. Crikey, I've found E-Is to be noisy for heaven's sake !

The reason I wound the toroidal 500VA was because first I unwound something I'd bought
because it was too noisy for hi-fi and then re-wound it for B= 0.85T instead of the B=
1.25T it was set up for.
I once supplied a customer with a sub woofer amp with another toroid from another
supplier
and thought myself that the toroid was barely quiet enough, and sure enough my client
objected so I replaced it with
an E&I which is usually far easier to make quiet than a toroid.
Two other toroids from a third supplier were too noisy so I gave up, and have never
bothered with buying a single tranny since.



their winding doesn't include proper baked varnish or epoxy imprgnation.

Doesn't need it if wound properly.

Rubbish.

Windings on a tranny are subject to forces shoving the winding one way then the other
depending on ac flow direction.
The windings are like those on a motor armature but have no place to go. The tension in
the polyester tape insulation
may be high but it acts like a diaphragm which gives off sound when agitated.



When i see a tube amp with all toroids in it I shudder, and usually it is a crap
product fron China.

Association like that is nuts.

The chinese how to make an amp look nice but their OPTs fail to atact me ans their PTs
are barely passable.

I never buy chinese made anything if I can avoid it. I get numerous spams from china
offering all this cheap as dirt crap
and I email them back to tell them I'd happily pay 4 times the price if the standards
were higher, then I explain what i expect.
It is like emailing a brick wall to tell it to move. They think they are such masters but
they are merely arrogant
amateurs.

You should see the hi-fi amps in the shop here selling for about usd $2,000 with a pair
of 6L6 per channel
Toroidal OPTs, PT, and they are all just toys....



But on the other hand the toroidals from Plitron are very decent, if anyone can
afford them...

I specify Toroid International.
http://www.toroid.se/

I compared Auricaps to plain cheap MKP Wimas and heard ZERO sound change.

No surprise there. For there to be any difference there would need to be a scientific
explanation why ! And there isn't. Essentially all plastic film caps perform
identically for coupling.

I would agree but the audiophiles cannot. I just work as directed, and when asked to
install
Auricaps, I just install them.

Patrick Turner.



Graham

Partridge figured out that tolerance of up to 10% DC imbalance was a
necessity for the highest level of OPT performance and he was right.

Bret Ludwig wrote

Partridge figured out that tolerance of up to 10% DC imbalance was a
necessity for the highest level of OPT performance and he was right.

10% of what?

Thanks, Ian

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

Ian Iveson wrote:

Bret Ludwig wrote

Partridge figured out that tolerance of up to 10% DC imbalance was a
necessity for the highest level of OPT performance and he was right.

10% of what?

Thanks, Ian

In Tremain's Audio Encyclopedia there is a graph for IMD vs DC imbalance
between primary halves.
So where you have 45mA in one tube, and 55mA in the other, then you have a
20% imbalance,
since 10mA more Ia flows in one of the tubes compared to the other.

At low levels its should not cause too much trouble and if you work out
the dc magnetisation
in Tesla for an average OPT then as long as the dc field isn't more than
1T then
there is still some ability for ac magnetisation. The lower the effective
µ, the greater the
tolerance for dc imbalalance which is the equivalent of the net imbalance
applied from a to a so
maybe 10mA dc a-a in the case above.
I don't exactly know what 10mA dc will do with a toroidal OPT with max µ =
40,000,
amd say Afe = 50 mm x 30mm, ML = 350mm, and Np = 2,000 turns.

But a core of E&I won't magnetize so easily; placing a fine air gap in a
pair of C cores or E&I lams
in a PP tranny can still give plenty of primary inductance, but very much
improve the tolerance
for dc offset currents.

Patrick Turner.

Patrick Turner wrote:
[snip]

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.

Looking at the R-core transformers on my shelf (haven't gotten around to
building with them yet, other stuff ahead in the queue :-), they are
built in exactly that way. The bobbins are clearly made in 2 parts,
which fit around the core leg & snap together. Then put the thing in a
lathe with a special drive fitting, & spool on the wire. Quick & easy.

David R Brooks wrote:

Patrick Turner wrote:
[snip]

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.

Looking at the R-core transformers on my shelf (haven't gotten around to
building with them yet, other stuff ahead in the queue :-), they are
built in exactly that way. The bobbins are clearly made in 2 parts,
which fit around the core leg & snap together. Then put the thing in a
lathe with a special drive fitting, & spool on the wire. Quick & easy.

And the round bobbin with no corners allows the wire to lay better unlike a rectangular bobbin
which makes the first few layers difficult to wind since the wire trys to get gaps between turns
etc.

Patrick Turner.

Patrick Turner wrote:

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.

Correct.


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.

You got it. The bobbin even has a kind of gear tooth arrangement to fit the winding machine.


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.

Sounds about right.


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.

I reckon E-Is would be hard to beat on any count actually.

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.

I've never actually seen a comparative quote. Since the Asian guys quite like using R-cores,
I'd guess they pay less for them than toroids which *must* be quite labour intensive.

Graham

Patrick Turner wrote

Ian Iveson wrote:

Bret Ludwig wrote

Partridge figured out that tolerance of up to 10% DC imbalance was a
necessity for the highest level of OPT performance and he was right.

10% of what?

In Tremain's Audio Encyclopedia there is a graph for IMD vs DC imbalance
between primary halves.
So where you have 45mA in one tube, and 55mA in the other, then you have a
20% imbalance,
since 10mA more Ia flows in one of the tubes compared to the other.

snip...

Thanks. Could have meant anything.

cheers, Ian

Pooh said:

....toroids which *must* be quite labour intensive

Why?

cheers, Ian

"Ian Iveson"
Pooh said:

...toroids which *must* be quite labour intensive

Why?



** More steps are involved in winding a toroidal - plus their manufacture
uses a special "shuttle" winding machine that can do only one tranny at a
time.

R-cores have so many practical advantages it is a surprise how few you see
being used.

Maybe that is about to change.

My recently acquired ( Asian made) CRO has one for example.

http://www.filespoint.com/point/2689...00578.JPG.html




........ Phil

Ian Iveson wrote:

Pooh said:

...toroids which *must* be quite labour intensive

Why?

The processes don't easily lead to a high level of automation and are also quite
slow.

Graham

Phil wrote

...toroids which *must* be quite labour intensive

Why?

** More steps are involved in winding a toroidal - plus their manufacture
uses a special "shuttle" winding machine that can do only one tranny at a
time.


That doesn't have much bearing on how labour-intensive they are. You could say
much the same about many products made entirely by automated machinery involving
no hand work.

There is an anomoly in the common perception of China, incidentally. On the one
hand, it is said that they depend on cheap labour, and on the other that they
are likely to baulk at the prospect of making toroids because they are too
difficult. However, obviously if those difficulties can be overcome by intensive
labour, then one might expect the Chinese to favour toroids.

Another common assumption, and one that Patrick has made several times, is that
winding a toroid requires a shuttle. Not true...fortunately, because then the
machine really would be complicated.

The hard parts about making a toroid are clamping the workpiece, and traversing
the core with the bobbin. The machinery is more complex and expensive, and both
the machinery and the process are less versatile. Hence automation can only be
justified by large production runs of the same transformer.

Custom-wound toroids don't seem to be commonly offered. If the only problem was
the need for intensive labour, then they would be the perfect candidate for
boutique production. Actually they are just hard to make, no matter how you make
them.

R-cores have so many practical advantages it is a surprise how few you see
being used.

Yes, and come to think of it, why haven't they *always* been used? What are the
problems? They seem to be common when cast or pressed cores are used, but
winding strip into anything other than a toroid is fundamentally problematic.
How are the strips kept squashed together in the straight runs, and how does the
core keep its shape during and after the winding of the strip? Presumably it
must be annealed after winding and clamping, or bonded somehow. There is also
the need for precision-cutting of strip to a shape peculiar to each core size,
without leaving a burr on the edge. I wonder if that is done before or after the
insulating coating? That's quite a lot of tricky processing dedicated to each
core size.


Maybe that is about to change.

My recently acquired ( Asian made) CRO has one for example.

http://www.filespoint.com/point/2689...00578.JPG.html


Is that a strip-wound core?

cheers, Ian

Ian Iveson wrote:

Phil wrote

R-cores have so many practical advantages it is a surprise how few you see
being used.

Yes, and come to think of it, why haven't they *always* been used?

They were only 'invented' in relatively recent times.

What are the problems?

More expensive than common E-I.

They seem to be common when cast or pressed cores are used,

Eh ? Please give an example of a cast or pressed core !

but
winding strip into anything other than a toroid is fundamentally problematic.
How are the strips kept squashed together in the straight runs, and how does the
core keep its shape during and after the winding of the strip? Presumably it
must be annealed after winding and clamping, or bonded somehow. There is also
the need for precision-cutting of strip to a shape peculiar to each core size,
without leaving a burr on the edge. I wonder if that is done before or after the
insulating coating? That's quite a lot of tricky processing dedicated to each
core size.

The guys that make the cores and accesories have it sorted for sure. You need to buy
a special winding machine too.

Graham

"Ian Iveson Criminal Pedo- ****wit "



...toroids which *must* be quite labour intensive

Why?

** More steps are involved in winding a toroidal - plus their
manufacture uses a special "shuttle" winding machine that can do only one
tranny at a time.


That doesn't have much bearing on how labour-intensive they are.


** Yes it ****ING does ****HEAD !!


Labour = human labour.



Another common assumption, and one that Patrick has made several times, is
that winding a toroid requires a shuttle.

Not true..


** Shame it is true.

YOU ****ing ASININE CRIMINAL PSYCHOPATH .




Custom-wound toroids don't seem to be commonly offered.


** What " seems" to a lying, POMMY psycho**** is not fact.



Is that a strip-wound core?


** Abso- ****ing- lutely.


You ASININE PILE OF SUB HUMAN PUSTULANCE.






....... Phil

Phil Allison wrote:

You ASININE PILE OF SUB HUMAN PUSTULANCE.

...... Phil

Whereas you're simply more in the pestilence category.

Graham

Graham wrote

They seem to be common when cast or pressed cores are used,

Eh ? Please give an example of a cast or pressed core !

Search for "amorphous core".

There are two ways of making amorphous cores. One is to cast a glassy strip and
wind it, and the other is to press a powder very hard. Generally it seems the
first is used for larger cores, presumably because of the problems of pressing
big things. I am assuming amorphous is a poor electrical conductor...?

As it happens, it looks like amorphous R-cores are most commonly made using cast
strip. I guess this is because the problems of winding small bobbins in-situ?

Searching under "amorphous core" or "r-core" gave very different results from
last time I tried. Seems like suddenly *everyone* has jumped on the bandwagon.

Anyway, pressed R-cores aren't as common as I thought, although pressed
amorphous toroids are. Cast amorphous strip-wound is increasingly common. I
would like to know how they clamp the straight sections to stop the laminations
springing out or buzzing.

The guys that make the cores and accesories have it sorted for sure. You need
to buy
a special winding machine too.

Of course, otherwise it would be labour-intensive. As it happens it is
complicated-and-expensive-machine-time-intensive. Quite possibly such machines
require more minding, I'll grant you that. I just wanted to dispel the notion
that they are all hand made, and that a shuttle is required. That would not be a
viable proposition.

The (relatively) simple method is to wind the wire on to a split bobbin in-situ
(as with an R-core), and then wind it off the bobbin onto the core. Clever eh?

As for the idea that R-cores are a recent "invention", I just don't see
it...pretty obvious idea don't you think? I assume that practical realisation
has been the sticking point. Perhaps the existing technology for strip-winding
toroidal cores could be adapted at relatively low cost.

cheers, Ian

At low levels its should not cause too much trouble and if you work out
the dc magnetisation
in Tesla for an average OPT then as long as the dc field isn't more than
1T then
there is still some ability for ac magnetisation. The lower the effective
µ, the greater the
tolerance for dc imbalalance which is the equivalent of the net imbalance
applied from a to a so
maybe 10mA dc a-a in the case above.
I don't exactly know what 10mA dc will do with a toroidal OPT with max µ =
40,000,
amd say Afe = 50 mm x 30mm, ML = 350mm, and Np = 2,000 turns.

But a core of E&I won't magnetize so easily; placing a fine air gap in a
pair of C cores or E&I lams
in a PP tranny can still give plenty of primary inductance, but very much
improve the tolerance
for dc offset currents.


Some years ago, I used a power transformer for an output transformer in
an AM table radio. Without gapping it. Though the 60 or so ma of DC
from the single ended pentode feeding it didn't seem to bother it any.
The transformer was intended to produce 12V centertapped at around 3
amps. The speaker loads half the secondary.

I'd like to get a better understanding of what the DC and the audio is
doing to this transformer and why it seemed to work when it "shouldn't"...

Ian Iveson wrote:

Phil wrote

...toroids which *must* be quite labour intensive

Why?

** More steps are involved in winding a toroidal - plus their manufacture
uses a special "shuttle" winding machine that can do only one tranny at a
time.

That doesn't have much bearing on how labour-intensive they are. You could say
much the same about many products made entirely by automated machinery involving
no hand work.

There is an anomoly in the common perception of China, incidentally. On the one
hand, it is said that they depend on cheap labour, and on the other that they
are likely to baulk at the prospect of making toroids because they are too
difficult. However, obviously if those difficulties can be overcome by intensive
labour, then one might expect the Chinese to favour toroids.

Another common assumption, and one that Patrick has made several times, is that
winding a toroid requires a shuttle. Not true...fortunately, because then the
machine really would be complicated.

The shuttle I use to hand wind a toroidal is a piece of broom handle about 300mm
long
with deep notches at each end so that the wire for a winding can be loaded onto the
shuttlle so that one turn around the shuttle = 1 turn around the core. The wire for
a given winding must be preloaded onto the shuttelt with wire to spare.

But a toroidal winding machine has a circular shuttle in two halves which is clipped
together through toroid hole
and rotated on rollers to load it up before winding the wire back onto the core.
It is labour intensive and slow, but 20 times faster than the broom handle shuttle.

The toroid tranny method whatever it is isn't good where one wants to have an OPT
with say 4 primary windings for
the anode primary CFB primary ( 8 wire ends ), and say up to 24 winding ends for 12
windings which allow wasteless
low loss secondary configs for different impedance matches.

The E&I allow the winding ends to just come out each side of the wound bobbin.
OK, the leakage inductance is lower on toroidals than on E&I but then that is
because the
"traverse width" of the winding is the ccentre line distance around the core rather
than the distance across the bobbin. Capacitance may be higher with a toroid.

In any case i can wind E&I OPT very effectively with bandwidth at full power without
NFB using triodes
from 16Hz to 100kHz + very much easier than a damn toroid.



The hard parts about making a toroid are clamping the workpiece, and traversing
the core with the bobbin. The machinery is more complex and expensive, and both
the machinery and the process are less versatile. Hence automation can only be
justified by large production runs of the same transformer.

Chinese makers of transformer winding machines spammed me a couple of years ago but
the cheapest
one for E&I was forsale for aud $2,500 from an agent guy.
I said I built mine for 1 week's work and $200.
I never heard from them again.
The toroidal machines were dearer.


Custom-wound toroids don't seem to be commonly offered. If the only problem was
the need for intensive labour, then they would be the perfect candidate for
boutique production. Actually they are just hard to make, no matter how you make
them.

My attempts to get custom toroidals wound resulted in a high cost item unavailable
until months had passed
so I have given up trying to get anyone to wind my designs.
When they see what I want they go pale and vomit and I have to retreat.
I tell them I have wound all this stuff and they just don't wanna know.

Most consumer electronics tranny winding in Oz is 99.99% large number runs of mains
trannies operating at 1.2Tesla, and random wound coils, high noise, temperature, and
none I know possess or use a vac chamber and oven for varnish
impregnation.

There used to be skilled tradesmen and many women who wound spendid layer wound E&I
trannies but
not much now.
The imports of cheap nasty chinese crap is slowly but surely forcing the Oz tranny
winders to give up.
The labour in china is 26dB cheaper than Oz labour, so the chinese can gurrantee
their product for
5 years because if 10% failiures occur the replacements by the supplier doesn't
matter.



R-cores have so many practical advantages it is a surprise how few you see
being used.

Yes, and come to think of it, why haven't they *always* been used? What are the
problems?

They are still a lot more exensive than an E&I trannie.
The E&I are wound with 2 concentric bobbins, primary on one and any assortment of
secondaries on the other,
and large numbers of bobbins can be wound at the same time.
The cores are high grade GOSS with max µ = 17,000 if they were fully interleaved,
but they are
not interlaved at all and a block of E and block of I are placed around the
assembled bobbins by machine and
welded with machine welding machines. The resulting µ of the material is
sufficiently high to
give low iron losses. This production method is very cheap compared to anything
else.

So regardless of how much lighter or better an R core or toroidal might be, the
common denominator
price dominates the market so that 90% of all electronics looks like it has been
made at the same factory
with the same automation and what little labour is engaged is paid peanuts.



winding strip into anything other than a toroid is fundamentally problematic.
How are the strips kept squashed together in the straight runs, and how does the
core keep its shape during and after the winding of the strip? Presumably it
must be annealed after winding and clamping, or bonded somehow. There is also
the need for precision-cutting of strip to a shape peculiar to each core size,
without leaving a burr on the edge. I wonder if that is done before or after the
insulating coating? That's quite a lot of tricky processing dedicated to each
core size.

Ah, the wonders of the mechanised machines in factories have to be seen to be
believed....

Patrick Turner.




Maybe that is about to change.

My recently acquired ( Asian made) CRO has one for example.

http://www.filespoint.com/point/2689...00578.JPG.html


Is that a strip-wound core?

cheers, Ian

Patrick Turner" wrote

...But a toroidal winding machine has a circular shuttle in two halves which
is clipped
together through toroid hole
and rotated on rollers to load it up before winding the wire back onto the
core.
It is labour intensive and slow, but 20 times faster than the broom handle
shuttle.

Quite, as I have just explained, except for your use of the word "shuttle".

The essential thing about a shuttle is that it goes backwards and forwards. What
you describe here is not a shuttle. If the bobbin were repeatedly passed through
the hole in order to wind the wire onto the core, it would be a shuttle of
sorts, more or less, but it doesn't, it simply turns on its axis. "Spool" would
be a less misleading term.

It is not necessarily labour intensive. It can be machine-intensive instead. How
quick depends on how many machines or people are on the job, and how fast they
work. It would generally need to be more than 20 times faster than the broom
handle shuttle.


...The E&I are wound with 2 concentric bobbins, primary on one and any
assortment of
secondaries on the other,
and large numbers of bobbins can be wound at the same time.
The cores are high grade GOSS with max µ = 17,000 if they were fully
interleaved,
but they are
not interlaved at all and a block of E and block of I are placed around the
assembled bobbins by machine and
welded with machine welding machines. The resulting µ of the material is
sufficiently high to
give low iron losses. This production method is very cheap compared to
anything
else...

Perhaps this kind of construction partly explains Robert's observations using a
cheap power transformer for SE power output.

cheers, Ian

Patrick Turner wrote:
[snip]

Most consumer electronics tranny winding in Oz is 99.99% large number runs of mains
trannies operating at 1.2Tesla, and random wound coils, high noise, temperature, and
none I know possess or use a vac chamber and oven for varnish
impregnation.

I realise, Patrick, that you're over East, but here in Perth I would put
in a word for New Era Electro Service in Maddington. I had a couple of
mains transformers done there, & I recently tested them for noise, etc.
Practically inaudible (with my ear right up to them), at rated load.
Just audible with a triac light dimmer in the primary, driven at 50%
power (now that sorts 'em out
They are certainly varnish impregnated (it's a rather unsightly black
varnish, but there, we can't get everything). I can't state with
certainty if its vacuum applied, but it does look it.
The down-side? He only does power transformers: no chokes or OPTs.

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 !

Graham


Ian Iveson wrote:

Graham wrote

They seem to be common when cast or pressed cores are used,

Eh ? Please give an example of a cast or pressed core !

Search for "amorphous core".

There are two ways of making amorphous cores. One is to cast a glassy strip and
wind it, and the other is to press a powder very hard. Generally it seems the
first is used for larger cores, presumably because of the problems of pressing
big things. I am assuming amorphous is a poor electrical conductor...?

As it happens, it looks like amorphous R-cores are most commonly made using cast
strip. I guess this is because the problems of winding small bobbins in-situ?

Searching under "amorphous core" or "r-core" gave very different results from
last time I tried. Seems like suddenly *everyone* has jumped on the bandwagon.

Anyway, pressed R-cores aren't as common as I thought, although pressed
amorphous toroids are. Cast amorphous strip-wound is increasingly common. I
would like to know how they clamp the straight sections to stop the laminations
springing out or buzzing.

The guys that make the cores and accesories have it sorted for sure. You need
to buy
a special winding machine too.

Of course, otherwise it would be labour-intensive. As it happens it is
complicated-and-expensive-machine-time-intensive. Quite possibly such machines
require more minding, I'll grant you that. I just wanted to dispel the notion
that they are all hand made, and that a shuttle is required. That would not be a
viable proposition.

The (relatively) simple method is to wind the wire on to a split bobbin in-situ
(as with an R-core), and then wind it off the bobbin onto the core. Clever eh?

As for the idea that R-cores are a recent "invention", I just don't see
it...pretty obvious idea don't you think? I assume that practical realisation
has been the sticking point. Perhaps the existing technology for strip-winding
toroidal cores could be adapted at relatively low cost.

cheers, Ian

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.

Only small cores are pressed, such as for SMPS as far as I have been able to
discover, and I guess that R-cores are only feasible when they are relatively
large.

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.

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. 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.

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.

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

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.

cheers, Ian



They seem to be common when cast or pressed cores are used,

Eh ? Please give an example of a cast or pressed core !

Search for "amorphous core".

There are two ways of making amorphous cores. One is to cast a glassy strip
and
wind it, and the other is to press a powder very hard. Generally it seems the
first is used for larger cores, presumably because of the problems of
pressing
big things. I am assuming amorphous is a poor electrical conductor...?

As it happens, it looks like amorphous R-cores are most commonly made using
cast
strip. I guess this is because the problems of winding small bobbins in-situ?

Searching under "amorphous core" or "r-core" gave very different results from
last time I tried. Seems like suddenly *everyone* has jumped on the
bandwagon.

Anyway, pressed R-cores aren't as common as I thought, although pressed
amorphous toroids are. Cast amorphous strip-wound is increasingly common. I
would like to know how they clamp the straight sections to stop the
laminations
springing out or buzzing.

The guys that make the cores and accesories have it sorted for sure. You
need
to buy
a special winding machine too.

Of course, otherwise it would be labour-intensive. As it happens it is
complicated-and-expensive-machine-time-intensive. Quite possibly such
machines
require more minding, I'll grant you that. I just wanted to dispel the notion
that they are all hand made, and that a shuttle is required. That would not
be a
viable proposition.

The (relatively) simple method is to wind the wire on to a split bobbin
in-situ
(as with an R-core), and then wind it off the bobbin onto the core. Clever
eh?

As for the idea that R-cores are a recent "invention", I just don't see
it...pretty obvious idea don't you think? I assume that practical realisation
has been the sticking point. Perhaps the existing technology for
strip-winding
toroidal cores could be adapted at relatively low cost.

cheers, Ian

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

"Pooh Bear"

Really ? They start at about 15-20 VA.

They are recent in relative terms.




** My old Brother dot matrix printer ( model 1102 ? ) used a 12 VA,
R-Core.

Bought it way back in 1983.

Seen several Asian hi-fi amps dating from the early 80s ( Luxman for one)
using 300 VA R-Cores made by Orion.



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



** Iveson is TROLLING ****WIT mental case.





........ Phil

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

BTW, R-core is claimed as a trade mark by

http://www.kitamura-kiden.co.jp/english/

who reckon they introduced it to the world in 1978.

Why do they say it is round when it isn't? Presumably they mean rounded. The
cross-section is a rounded diamond shape, by the looks.

It may follow that the exact method of manufacture is unpublished. They have
loads of patents, they say. Is there anywhere on the net I can get copies of
patents for free?

Perhaps you, or anyone, can take a look at the core in this pictu

http://www.icl.co.jp/audio/english/RX40.htm

and suggest exactly how it is made. My guess is that the final forming is done
with a press, and I still can't see how it holds its shape unless the strip is
bonded along its whole length.

cheers, Ian

Ian Iveson wrote:

BTW, R-core is claimed as a trade mark by

http://www.kitamura-kiden.co.jp/english/

who reckon they introduced it to the world in 1978.

Yes, I believe that is correct. R-cores are also made by other suppliers under
license.


Why do they say it is round when it isn't? Presumably they mean rounded. The
cross-section is a rounded diamond shape, by the looks.

The cross section of the core itself is indeed round.


It may follow that the exact method of manufacture is unpublished. They have
loads of patents, they say. Is there anywhere on the net I can get copies of
patents for free?

If it's a US patent they are certainly available for free. Just Google.


Perhaps you, or anyone, can take a look at the core in this pictu

http://www.icl.co.jp/audio/english/RX40.htm

and suggest exactly how it is made. My guess is that the final forming is done
with a press, and I still can't see how it holds its shape unless the strip is
bonded along its whole length.

It's probably formed by winding on a mandrel I reckon.

Graham

On Mon, 19 Jun 2006 23:33:58 +0100, 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 !

Graham


Ian Iveson wrote:

Graham wrote

They seem to be common when cast or pressed cores are used,

Eh ? Please give an example of a cast or pressed core !

Search for "amorphous core".

There are two ways of making amorphous cores. One is to cast a glassy strip and
wind it, and the other is to press a powder very hard. Generally it seems the
first is used for larger cores, presumably because of the problems of pressing
big things. I am assuming amorphous is a poor electrical conductor...?

As it happens, it looks like amorphous R-cores are most commonly made using cast
strip. I guess this is because the problems of winding small bobbins in-situ?

Searching under "amorphous core" or "r-core" gave very different results from
last time I tried. Seems like suddenly *everyone* has jumped on the bandwagon.

Anyway, pressed R-cores aren't as common as I thought, although pressed
amorphous toroids are. Cast amorphous strip-wound is increasingly common. I
would like to know how they clamp the straight sections to stop the laminations
springing out or buzzing.

The guys that make the cores and accesories have it sorted for sure. You need
to buy
a special winding machine too.

Of course, otherwise it would be labour-intensive. As it happens it is
complicated-and-expensive-machine-time-intensive. Quite possibly such machines
require more minding, I'll grant you that. I just wanted to dispel the notion
that they are all hand made, and that a shuttle is required. That would not be a
viable proposition.

The (relatively) simple method is to wind the wire on to a split bobbin in-situ
(as with an R-core), and then wind it off the bobbin onto the core. Clever eh?

As for the idea that R-cores are a recent "invention", I just don't see
it...pretty obvious idea don't you think? I assume that practical realisation
has been the sticking point. Perhaps the existing technology for strip-winding
toroidal cores could be adapted at relatively low cost.

cheers, Ian
I have a R-40 core and bobbin on my desk. The core was wound on a
rectangular mandrel. The first and last layers have been spot welded.

The core has been vacuum impregnated with a thin epoxy. It is very
well done. The core is rock solid.

The lamination strip width on the first and last turn is .195" in
width. The width of the center turn is .812".

The available winding area for one bobbin is only 1.542" x .125" which
isn't much concidering the size of the core.

This lamination is very similar in size to UI75 lamination as shown in
Tempel Steel Corp. book. www.Tempel.com

Economics dictated that we utilize the UI lamination design because
of the difference in the core cost and overall labor cost. We utilized
high speed bobbin winders and automated lamination stackers. The
stray flux emanation was lower in the R-Core but the UI was
acceptable.

I think that I made this comparison in the very late 1970s for a
medical instrument.

Jerry

Jerry said

I have a R-40 core and bobbin on my desk. The core was wound on a
rectangular mandrel. The first and last layers have been spot welded.

The core has been vacuum impregnated with a thin epoxy. It is very
well done. The core is rock solid.

The lamination strip width on the first and last turn is .195" in
width. The width of the center turn is .812".

The available winding area for one bobbin is only 1.542" x .125" which
isn't much concidering the size of the core.

This lamination is very similar in size to UI75 lamination as shown in
Tempel Steel Corp. book. www.Tempel.com

Economics dictated that we utilize the UI lamination design because
of the difference in the core cost and overall labor cost.

...We utilized
high speed bobbin winders and automated lamination stackers.

The
stray flux emanation was lower in the R-Core but the UI was
acceptable.

I think that I made this comparison in the very late 1970s for a
medical instrument.


Much thanks, Jerry.

Yes it is wrapped round a mandrel...that's the only way to use a single
continuous strip as far as I can see.

The key for me in your description is what I couldn't see from the pictures: the
adhesive filler.

If you wind strip round a mandrel, then no matter what the shape of the mandrel,
the winding will eventually end up round. I dimly remember there is even a law
devoted to this phenomenon. The less plastic the strip, the harder it is to
maintain the shape of the mandrel. GOSS is hard and elastic, hardly plastic at
all, and winding a shape with straight sides is impossible even for a few turns.

Even if you clamped the core and tack welded the ends of the strip, then when
you took it off the mandrel it would spring into an oval shape, with some
awkward wriggling round the welds.

That's why I suggested that the final process must be clamping, and bonding the
strip along its whole length. This could be done either by impregnation, or by
using coated strip, with the former being much easier if the results are good
enough.

I wonder if a notched mandrel is used? Otherwise it must be difficult to get
successive layers of wider strip to sit true on thinner ones. If so, then two
half-mandrels are required (or possibly four quarters), perhaps held apart so
that the straight sections of core are left free for the tack welding. Once
wound, the mandrels could be moved together to free the core, which would spring
into whatever shape it fancies.

Finally, I suggest, it is impregnated and then pressed to hold it in shape until
the adhesive filler goes off.

Is the cross-section round, BTW? It doesn't look round in the pictures.

cheers, Ian

On Sat, 24 Jun 2006 02:49:17 GMT, "Ian Iveson"
wrote:

Jerry said

I have a R-40 core and bobbin on my desk. The core was wound on a
rectangular mandrel. The first and last layers have been spot welded.

The core has been vacuum impregnated with a thin epoxy. It is very
well done. The core is rock solid.

The lamination strip width on the first and last turn is .195" in
width. The width of the center turn is .812".

The available winding area for one bobbin is only 1.542" x .125" which
isn't much concidering the size of the core.

This lamination is very similar in size to UI75 lamination as shown in
Tempel Steel Corp. book. www.Tempel.com

Economics dictated that we utilize the UI lamination design because
of the difference in the core cost and overall labor cost.

...We utilized
high speed bobbin winders and automated lamination stackers.

The
stray flux emanation was lower in the R-Core but the UI was
acceptable.

I think that I made this comparison in the very late 1970s for a
medical instrument.


Much thanks, Jerry.

Yes it is wrapped round a mandrel...that's the only way to use a single
continuous strip as far as I can see.

The key for me in your description is what I couldn't see from the pictures: the
adhesive filler.

If you wind strip round a mandrel, then no matter what the shape of the mandrel,
the winding will eventually end up round. I dimly remember there is even a law
devoted to this phenomenon. The less plastic the strip, the harder it is to
maintain the shape of the mandrel. GOSS is hard and elastic, hardly plastic at
all, and winding a shape with straight sides is impossible even for a few turns.

Even if you clamped the core and tack welded the ends of the strip, then when
you took it off the mandrel it would spring into an oval shape, with some
awkward wriggling round the welds.

That's why I suggested that the final process must be clamping, and bonding the
strip along its whole length. This could be done either by impregnation, or by
using coated strip, with the former being much easier if the results are good
enough.

I wonder if a notched mandrel is used? Otherwise it must be difficult to get
successive layers of wider strip to sit true on thinner ones. If so, then two
half-mandrels are required (or possibly four quarters), perhaps held apart so
that the straight sections of core are left free for the tack welding. Once
wound, the mandrels could be moved together to free the core, which would spring
into whatever shape it fancies.

Finally, I suggest, it is impregnated and then pressed to hold it in shape until
the adhesive filler goes off.

Is the cross-section round, BTW? It doesn't look round in the pictures.

cheers, Ian


Well Ian, I measured the R40 core and found that the diameter of the
core is 2.75". The dimensions are .873" x .830" and give me an area
value of 94.8% of that of a perfect circle, so I would say that you
could consider it to be circular in nature.

Consider that the very long strip of core material has to have a width
of .195" which progresses to .812" when at half length then the with
progressively narrows back to .195" on the last layer. That is some
piece of computer operated equipment that does that. I would like
to see their equipment.

If we assume the thickness of the material to be .006" GOSS, there
would be about 138 layer. The strip of steel would be 1013" long.

For those who might fight with my lack of exact math, It is hard
to get precise dimensions because of the bobin wound coil.

Jerry

Jerry wrote

Well Ian, I measured the R40 core and found that the diameter of the
core is 2.75". The dimensions are .873" x .830" and give me an area
value of 94.8% of that of a perfect circle, so I would say that you
could consider it to be circular in nature.

Consider that the very long strip of core material has to have a width
of .195" which progresses to .812" when at half length then the with
progressively narrows back to .195" on the last layer. That is some
piece of computer operated equipment that does that. I would like
to see their equipment.

If we assume the thickness of the material to be .006" GOSS, there
would be about 138 layer. The strip of steel would be 1013" long.

For those who might fight with my lack of exact math, It is hard
to get precise dimensions because of the bobin wound coil.

Thanks.

I tried to find their US patents, unsuccessfully as far as the
winding-round-a-rectangular-mandrel is concerned.

I did find two patents for how to wind the copper onto a torroid that were
interesting, and confirm that the hard parts are clamping the workpiece and
traversing the core with the spool.

I also found several patents concerning the winding of GOSS strip into toroids
of circular cross-section. Mandrels with semi-circular trenches are proposed,
and winding and grinding (gulp!) the strip at the same time. IIRC the R-core
site says the strip is slit, not ground.

A rectangular mandrel would snatch and slop, so I guess that forces separation
of the processes of shaping the strip and winding it. OTOH, a round
cross-section toroid has only one of the advantages of an R-co the core can
completely fill the copper winding with no gaps. It's still hard to wind the
copper.

I also came across several schemes for winding the core around the copper coils.
Quite a feat.

cheers, Ian