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Re: Boost Converter Efficiency Improvements
Bill Sloman wrote:
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This example is most certainly not a cottage place. They have laser
alignment and even engineering capabilities, something you won't find at
Uncle Leroy's Coilwerks.


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Then they were fairly easy coils and did not need a custom bobbin and a
custom core.


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Well, when have you ordered your last coil and how small was it?

Example from my current project: The coil has to be over 100uH, under
2mm long, 200um in diameter and magnetically completely shielded. Yes,
that's micrometer. Try that at a cottage place.


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I don't use literature or even math for that. I prototype it and measure
the H-field, minimize it, then document the geometries and procedure for
production.


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That's for resistors, you can't wind a coil like that.


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What year was that and what kind of coil? I am talking real cutting edge
stuff, where the average cottage coil winder says it's impossible. For
the rest, I can wind 2-3 pieces myself.


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Yes, they are, but not for the very noise-critical ones.


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It never is, else they would not need a consultant to design it :-)

--  
Regards, Joerg

http://www.analogconsultants.com/

Re: Boost Converter Efficiency Improvements
On Saturday, 22 June 2013 00:18:26 UTC+10, Joerg  wrote:
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kkeling  
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Not as "easy" as the Bourns SRF parts that you can buy off the shelf, but a
 whole lot more suitable for what I wanted to do.
  
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Or try to buy it off the shelf.

This is a long way from the Bourns SRF coils you are touting.
  
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Re-inventing the wheel?
  
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Actually, you can. The other name for it - according to Rayner and Kibble -
 is the "bootlace technique" where you wind on half the turns progressively
, so that they are evenly spread around the toroid, then wind on the other  
half in the same sense, but coming back around the toroid, so that the end  
of the coil comes off at the same point as the start came in.

Since the wires cross from time to time, I suppose it might look like a boo
tlace ...  

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But you claim that then it is cheaper to go with the Bourns SRF coils, desp
ite the very limited range available - compared with what you can get wound
 onto off-the-shelf formers and cores.

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Depends on how they are used.
  
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What's obvious and easy for a consultant isn't necessarily obvious and easy
 for a wet-behind-the-ears customer who has never heard of an Ayrton-Perry  
wound inductor.

--  
Bill Sloman, Sydney

Re: Boost Converter Efficiency Improvements
Bill Sloman wrote:
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[...]

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The Bourns is not what I meant, that's a bone-simple inductor. "Not
easy" to me means something where many coil manufacturers have bowed out
with words like "that is impossible".


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So when did you?


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That cannot be bought off-the-shelf.


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I am not touting that, the SRF series is merely what David is using and
in his case it is the right choice. Unless he absolutely needs another
percent or two in efficiency, in which case bigger is usually better.


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No, I know how the wheel is built and I am designing one that's nicely
balanced. I do not need books for most of the stuff I design. Although I
must confess that when I had to do some heavy complex X+jY math a couple
weeks ago it produced some sweat beads. It's been so long ago that I did
it last time. However, a brief excursion onto the Internet was
sufficient to get back into that stuff.


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That's an old trick. I know it under the name backwards interleave but
there are probably many other names for it.


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It is cheaper. If you have the space and the efficiency is ok, why go
custom when you don't have to?


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RM cores are more noisy, there is no way around that. The more open a
magnetic path is the more stuff leaks.


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So where is your example of an Ayrton-Perry inductor?

--  
Regards, Joerg

http://www.analogconsultants.com/

Re: Boost Converter Efficiency Improvements
On Saturday, 22 June 2013 02:42:08 UTC+10, Joerg  wrote:
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<snip>

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I found it in Rayner and Kibble's "Coaxial AC Transformers".

William Ayrton died in 1908

http://en.wikipedia.org/wiki/William_Edward_Ayrton

so they have been around for a while. Ayrton was a student of Lord Kelvin (
of the Kelvin connection) so his stuff is part of the British electrical in
strument tradition, which I got turned on to by reading the Journal of Scie
ntific Instruments as a graduate student.

Herman K.P. Neubert's 1963 book "Instrument Transducers" was also influenti
al - he introduced me to the Blumlein bridge. Neubert was at the Royal Airc
raft Establishment at Farnborough in the UK. My current copy of the book ca
me, via Amazon, from the Sandia Corporation Library at Livermore, Californi
a - the address was stamped inside the cover and was subsequently over-stam
ped "discarded".

--  
Bill Sloman, Sydney

Re: Boost Converter Efficiency Improvements
Bill Sloman wrote:
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[...]

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Well, that's not exactly helping here. I do not believe they meant an
inductor with that. A part wound Ayrton-Perry style has, in its perfect
form, zero inductance.


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In those days most people didn't make it to a ripe old age, or rather,
61 was considered old back then.


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But even an inductor built by Her Royal Highness the Queen personally
will not be an inductor if wound Ayrton-Perry style. The whole purpose
of their winding technique is to reduce the inductance to a very small
value, ideally to zero.


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Sandia is one of the big research labs out here.

--  
Regards, Joerg

http://www.analogconsultants.com/

Re: Boost Converter Efficiency Improvements
On 22/06/2013 01:00, Joerg wrote:
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<snip>

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Agreed.
   http://en.wikipedia.org/wiki/Ayrton-Perry_winding

--  
Mike Perkins
Video Solutions Ltd
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Re: Boost Converter Efficiency Improvements
On Saturday, 22 June 2013 10:00:27 UTC+10, Joerg  wrote:
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<snip>

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A resistor wound Ayrton-Perry style has close to zero inductance. The think
ing that gave them that style of resistor also gave them an astatic inducto
r.

Presumably the common perception behind both astatic parts is what is memor
ialised in the "Ayrton-Perry" label. They probably published a paper somewh
ere ...
  
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His first wife died of TB in 1883. He seems to have died of "arterial disea
se"

http://www.oxforddnb.com/templates/article.jsp?articleid30%509&back=&ve
rsion20%04-09

which would probably have been fixed by Lipitor and a few stents - and mayb
e a by-pass operation - today. Coronary heart disease killed a lot of men i
n their sixties back then, including the great-grandfather for whom I was n
amed.

People did survive into their eighties and nineties, but not as many of the
m as do now. The aortic valve I had replaced in 2010 would probably be kill
ing me around now if I hadn't had the operation, and my two-years-younger b
rother had a quadruple by-pass a few months earlier. My arteries turned out
 to be a lot cleaner than his when checked out by cine-angiography. The thi
rd - even younger - brother, is a medico, and very careful about his his he
art.

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That's an Ayrton-Perry resistor. The Ayrton-Perry inductor was designed to  
have a minimum external magnetic field, which is the same idea, but what wo
rks for a resistor doesn't work in an inductor.
  
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and the Livermore Labs used to be name to be reckoned with.  

--  

Bill Sloman, Sydney

Re: Boost Converter Efficiency Improvements
Bill Sloman wrote:
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So, where is a live example (meaning at least on the web) of an
Ayrton-Perry inductor?

Or as the Romans said, hic Rhodus, hic salta :-)


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http://www.oxforddnb.com/templates/article.jsp?articleid30%509&back=&version20%04-09
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If it would have been successful that inductor would have shown up on
the web, wouldn't it?

[...]

--  
Regards, Joerg

http://www.analogconsultants.com/

Re: Boost Converter Efficiency Improvements
On Saturday, 22 June 2013 11:08:45 UTC+10, Joerg  wrote:
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If I had a toroid, I'd wind you one. Persuading a web-denizen to do somethi
ng that useful would take longer. It's actually totally obvious that the ap
proach would work - the interesting question is how nearly perfectly astati
c the toroidal inductor would be.

There's a well-known - and cute - form of liquid conductivity meter that us
es two stacked astatic toroids to measure the conductivity of the fluid in  
which they are both immersed on the basis that the current induced in the f
luid by the first - driven - toroid, which threads the second inductor, ind
uces a voltage in the second detecting toroid. Here's an example

http://www.mbhes.com/conductivity_measurement.htm

They don't say how they make their toroids astatic. They probably hope to h
ide it as a trade secret ...

<snip>

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Why? Inductors aren't fashionable, and people go way out of their way to av
oid designing transformers.

--  
Bill Sloman, Sydney

Re: Boost Converter Efficiency Improvements
Bill Sloman wrote:
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You can't sketch and scan it?


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Not sure what you mean astatic but simply back-threading on a toroid is
not an Ayrton-Perry winding.


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Sorry, but that's not more than an evasive answer.

--  
Regards, Joerg

http://www.analogconsultants.com/

Re: Boost Converter Efficiency Improvements
On Sunday, 23 June 2013 00:32:30 UTC+10, Joerg  wrote:
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Put it on my own web-site? It's not going to make you understand the idea any
better than you do now.
  
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"Astatic" - in this context, is just not generating an external magnetic field,
nor reacting to changes in an uniform external magnetic field.

Back threading a progressive winding with a single turn around the toroid
doesn't make the inductor you produce perfectly astatic, though it's a lot
better than it would be without that single turn.

Ayrton-Perry is a good deal closer to prefection, and the "wind half-way around
wind back over the full circumfernece of the toroid and then wind back half-way
around to get back to the start of the coil is presumably move nearly perfect
still.
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In the same way that your demand for an example on the web is an evasive
question. It would be nice if such an example existed, but absence of - a very
particular sort of - evidence isn't evidence of absence.

--  
Bill Sloman, Sydney

Re: Boost Converter Efficiency Improvements
Bill Sloman wrote:
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For example. Or on some free site.


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Au contraire, I have the feeling you don't understand :-)


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I suggest to take a closer look at what an Ayrton-Perry winding is and
what it is not. This is the real deal:

https://commons.wikimedia.org/wiki/File:Ayrton-Perry_winding.png

If you wind that onto anything, then ideally the resulting component has
no inductance. How is that doing any good on a toroidal inductor?


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No, I am simply stating there is no inductor with an Ayrton-Perry
winding. Because it makes no sense. It would be like a car with two
drive trains but each pulling in opposite direction.

--  
Regards, Joerg

http://www.analogconsultants.com/

Re: Boost Converter Efficiency Improvements
On Monday, 24 June 2013 00:34:01 UTC+10, Joerg  wrote:
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Enjoy your delusion, if it makes you feel better.
  
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That is the web-site I found for you. I wasn't paying enough attention, bec
ause it is a Ayrton-Perry non-inductive/astatic resistor and not the Ayrton
-Perry astatic/no-external-field inductor.

Ayrton and Perry were two historical characters who got their names attache
d to two different components - an astatic resistor and an astatic inductor
.

A web-site for the resistor doesn't make it the only "real deal" in town.
  
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Why  would you apply a scheme devised to make a non-inductive resistor, to  
an inductor? Ayrton and Perry invented a non-inductive resistor and a parti
cular way of making an astatic inductor. Their names are attached to both c
omponents but this doesn't make the two sorts of components interchangeable
, or even all that similar.

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Sadly, you are making a false statement. The Ayrton-Perry resistor and the  
Ayrton-Perry inductor are two distinct and different devices. The underlyin
g idea is the same, but the realisation of it in the resistor and the induc
tor are necessarily different.

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If you were to confuse a resistor with an inductor, you might think that.

--  
Bill Sloman, Sydney


Re: Boost Converter Efficiency Improvements
Bill Sloman wrote:
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[...]

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So why can't you simply point out the inductive example?


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Hic Rhodus, hic salta. Bring an example.


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Searching for "Ayrton-Perry inductor" gives zero hits. Maybe it doesn't
exist in the real world?

[...]

--  
Regards, Joerg

http://www.analogconsultants.com/

Re: Boost Converter Efficiency Improvements

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I found an "Aryton-Perry inductor" reference, but it is a variable
inductor, not necessarily astatic, although it does seem to be
iron-shielded.

<http://books.google.com/books?id=msU3AQAAMAAJ&pg=PA577&lpg=PA577&dq=Ayr
ton-Perry+inductor&source=bl&ots=Nu9OyS0WCM&sig=CvgKLJQUHOZE8sE0lI1u69LD
o2I&hl=en&sa=X&ei=uy3HUYzzAsS60gHm-YHYCA&ved0C%FoQ6AEwCg#v=onepage&q=Ayr
ton-Perry%20inductor&f=false>

Ref:  "Bulletin of the Bureau of Standards", vol 13, 1916, pages 570,
576, and 577.  Apparently there was a company making such a thing.  On
page 570, it states that the Ayrton-Perry inductor is not astatic.

Joe Gwinn

Re: Boost Converter Efficiency Improvements

[...]

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No, Bill's right Joerg, it does exist.

Here is a scan of it, from that book he's always going on about...

<
http://ee.devereux.me.uk/bills-transformer-1.jpg

<
http://ee.devereux.me.uk/bills-transformer-2.jpg


(really good book actually).

Perhaps it's called something else now.

--  

John Devereux

Re: Boost Converter Efficiency Improvements
John Devereux wrote:
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They may call it that way but it isn't an Ayrton-Perry winding. What is
in those two pictures is simply the old trick of winding around a toroid
and then shortly before reaching 360 degrees start winding backwards.

The windings all have the same orientation in terms of their magnetic
field, unlike in an Ayrton-Perry winding where their fields cancel.

The real Ayrton-Perry style is as shown in the lower right picture in
here, it has little to no inductance:

https://en.wikipedia.org/wiki/Ayrton-Perry_winding

--  
Regards, Joerg

http://www.analogconsultants.com/

Re: Boost Converter Efficiency Improvements

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haha, yes, perhaps it is just that book that calls it that.

The online references do seem to be to non-astatic variable inductors.

--  

John Devereux

Re: Boost Converter Efficiency Improvements
On Monday, 24 June 2013 18:22:57 UTC+10, John Devereux  wrote:
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't
  
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d  
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They don't have to be non-astatic - one of the references I dug up claimed  
that even the variable inductor could be made astatic, which is interesting
 - presumably if all the coils are paired in the right way the external fie
lds cancel while the internal fields can interact enough to provide the var
iability.

Pity Ayrton died before anybody could take a brain scan - his brain might h
ave been even more interesting than Einstein's.

--  
Bill Sloman, Sydney

Re: Boost Converter Efficiency Improvements
John Devereux wrote:
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Books have all sorts of misnomers in there. Often just an innocent error
and reviewers might not catch all of them because they can't be
famuiliar with 100% of the covered technologies. Sometimes it's more
gross though. My dad ran into some unexplainable discrepancies during
his master's thesis project. Until he found out that a widely accepted
formula (!) was wrong. It had been introduced in one publication and
then was, ivory-tower style, cited and copied in lots of other
publications. So often that it was at some point regarded as some sort
of law of nature. Yet it was clearly long.

--  
Regards, Joerg

http://www.analogconsultants.com/

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