interesting inductor

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https://www.digikey.com/products/en?keywords=RN%20242-6-02-1M8

That is technically a commmon-mode choke - which makes it cheap - but
is probably useful for a real-inductor need that we have now.  

It's spec'd at 1.8 mH per winding, but my AADE meter says about 2.5. I
should measure it some other ways to be sure.

(K seems to be over 0.99, so it would be a good common-mode filter but
not good for diff mode noise.)

I want an inductive DAC, namely a series of steps of inductance made
from inductors and relays. One of these could get me 2.5 uH, or 10 uH
with the windings in series. Two of the same part gives 0, 2.5, 5, 10,
and 20 mH, plus the oddball 12.5.

With 3 amps DC on both windings in series, it didn't get detectably
warm.

What I need to do, or actually delegate, is to measure L better, and
then L vs current. Need to hack up some rigs to do that.

Nice small PCB footprint. I can envision using this as a real
transformer, in power applications.  


Re: interesting inductor
On a sunny day (Sat, 17 Aug 2019 09:31:05 -0700) it happened
snipped-for-privacy@highlandsniptechnology.com wrote in

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I did that once for tuning a 30 kHz to 150 kHz or there about inductive loop driver,
Watch your voltages when the relays switch,
I wound the coils on potcores myself.

Schaffner is a very old company, already used their stuff in the sixties.
10 weeks lead time?


Re: interesting inductor
On Sat, 17 Aug 2019 17:08:04 GMT, Jan Panteltje

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I will have a uP controlling everything, so I can kill the source when
the relays switch. Cold switch.

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Yuk. I hate to wind coils.

Sometimes I have to.

https://www.dropbox.com/s/o2hz6oi08agzdy8/T850_Inductor.JPG?raw=1

Toroids are worse. I'm thinking that the Schaffner part is a ferrite
toroid.  

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Stock at Digikey.



Re: interesting inductor
On a sunny day (Sat, 17 Aug 2019 10:23:30 -0700) it happened
snipped-for-privacy@highlandsniptechnology.com wrote in

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OK, nice,



No problem here, for fine wire I put it on the dremel, a thousand turns is no problem.
Counting is.


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That circuit, I was thinking about that, is basically the same as a TV horizontal output no?
    +12V
     |    ____
     ||| (_____ defection coill
     )||  ------
     )|| ( HV coil
     ||| (____
     |-----------
     c    |      |
-- b     ---     |
     e   / \    ===  
     |   ---     | 'boost' cap  
     |    |      |
    ///  ///    ///

----- -------- base drive,  
    | |
    --

That gives a parabolic voltage pulse during flyback,
the HV coil is tuned to IIRC (was a discussion about that here long time ago) the third harmonic.
That pulse is the output you want,  
only you have a smaller coil, resulting in a higher frequency,  
The energy you store into the coil while the transistor is 'on' increases the longer it is on,
and the higher then the pulse is.
I have wound my own TV transformers both for tubes and transistors.

Never understood what the problem was with your coil.
:-)



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I dunno, I used their thyristor driver pulse transformers, also 4 kV isolation tested.  
Nice stuff.


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Re: interesting inductor
On Sat, 17 Aug 2019 19:39:07 GMT, Jan Panteltje

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My Dremel won't wind toroids! There is one trick for hand winding
toroids, where you make an H-shaped wire storage thing out of FR4 and
keep passing it through the hole, doling out wire. That helps a
little.

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No, not the same, more of a non-resonant HV pulse generator.

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I kept frying the inductors, two generations of Coilcraft parts. I was
well within the RMS current ratings, but skin effect apparently
dominated and the coils smoked.  

The clever horizontal output thing was originally tubes of course,
then bipolar transistors. I discovered that the c-b junction of one
high voltage horizontal-output transistor accidentally had the ideal
doping profile to be a kilovolt Grehkov drift step-recovery diode. Too
bad they don't make it any more.


Re: interesting inductor
On Sunday, August 18, 2019 at 3:23:38 AM UTC+10, snipped-for-privacy@highlandsniptechnology.com wrote:
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<snip>
  
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Toroid winding machines are cute. They depend on a split bobbin (two semicircular halves) which you put together so it goes through the hole in the torpid. You then wind the length of wire you need onto the bobbin, then wind it off again onto the toroid.

Elegant, but a pig to automate.

<snip>

--  
Bill Sloman, Sydney

Re: interesting inductor
On 17/08/2019 17:31, snipped-for-privacy@highlandsniptechnology.com wrote:
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But it would be saturated, surely?
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Cheers
--  
Clive

Re: interesting inductor
On Sat, 17 Aug 2019 18:16:30 +0100, Clive Arthur

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We'll have to find out. In a common-mode filter, I guess that they
assume that the line currents cancel in the core.


      dot
L1------/////////------->   load

L2------/////////-------<
      dot


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Re: interesting inductor
snipped-for-privacy@highlandsniptechnology.com> wrote in message  
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At what saturation current?  Q?  Tolerance?

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Good luck keeping 2.5mH at that current in anti-series.

The 2.5mH alone varies widely with ACV and manufacture.  Buy a dozen from  
different distributors and see if they measure the same.

Ungapped ferrite is the Z5U of magnetics.

CMCs typically saturate in the 10s of mA.

I don't have one of these handy to measure.  I have looked at the family  
before, and they have reasonable cost, and attenuation for EMC purposes,  
particularly at higher frequencies.


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Yes, CMCs are actually transformers, not coupled inductors.  Their leakage  
may not be great, but the isolation ratings are exemplary, making them  
tempting for such purposes as DC-DC converters.  It's hard to get more than  
a watt or so through them, however.

Tim

--  
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
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Re: interesting inductor
On Sat, 17 Aug 2019 12:31:46 -0500, "Tim Williams"

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I might want to output as much as 3 amps RMS. This will be a 3-phase
AC source, actually a PM alternator simulator with programmable
resistance and inductance. High inductances will be DSP simulated, but
I want some real L to be there for high frequencies. Maybe just one
real inductor would do. It's a messy simulation.


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That's the hazard. We'll have to measure it. If this won't work, we'll
have to buy a bunch of klunky single inductors.

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It's only about 15 mohms per winding, so there can't be many turns.

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This one should be good for lots of watts. Leakage L is only 17 uH!


Re: interesting inductor
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Yes, that's the point.

Would be alright for some watts as a resonant transformer, but you still  
need secondary side regulation for each output channel; no improvement over  
a bunch of discrete DC-DC modules.

Tim

--  
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
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Re: interesting inductor
On Saturday, 17 August 2019 18:31:13 UTC+2, snipped-for-privacy@highlandsniptechnology.com  wrote:
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That's because the series connection is the line current, so you only have differential inductance, probably 100 times lower than the common mode inductance of 1.8mH

The common mode inductance of 1.8mH saturates in the mA region

Cheers

Klaus

Re: interesting inductor
On Sat, 17 Aug 2019 13:57:55 -0700 (PDT), snipped-for-privacy@gmail.com
wrote:

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A thing that size should store a few mJ.


Re: interesting inductor
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A few uJ at best.

Look, I get it, you don't work with these things on a daily basis.  But you  
are still aware that saturation is a thing, right..?

Tim

--  
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
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Re: interesting inductor
On Sat, 17 Aug 2019 17:34:15 -0500, "Tim Williams"

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This is probably about the same size core as what's inside the CM
choke:

https://www.mouser.com/ProductDetail/JW-Miller/2324-V-RC?qs=sGAEpiMZZMsg%252By3WlYCkU4M2TElYYSkELQ4ZU27m%252Bck%3D

That's 1 mH, rated 2.4 amps, stores about 1.7 mJ at rated current.


You can store a few uJ in a really tiny inductor.

https://www.mouser.com/ProductDetail/KEMET/L1210R1R0MDWIT?qs=sGAEpiMZZMsg%252By3WlYCkUyI47vaDA87SCPoQ72WSmes%3D






Re: interesting inductor
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So what, you think they put the same core in that CMC?

Tim

--  
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
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Re: interesting inductor
On Sat, 17 Aug 2019 20:09:20 -0500, "Tim Williams"

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Ferrites store similar energy by volume.

Millijoules, not microjoules.

You snipped your "few microjoules" claim. We'll just forget you ever
said that.






Re: interesting inductor
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When gapped, yes.


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A mu_eff about 1000 times higher than the powdered iron core is both very  
likely for the choke, and fully accounts for the 1000 times lower energy  
rating.

Capacitors go as epsilon E^2 / 2, but high-k dielectrics have considerably  
lower Emax so store about the same energy (give or take how much you want to  
saturate them in the process).

Inductors go as B^2 / (2 mu), so a mu10%k core stores fuck-all energy at  
saturation.

Tim

--  
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
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Re: interesting inductor
On Sat, 17 Aug 2019 22:31:26 -0500, "Tim Williams"

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The estimate of a few mA to saturate this core corresponds to ballpark
10 nJ storage capacity.




Re: interesting inductor
On a sunny day (Sat, 17 Aug 2019 21:17:26 -0700) it happened
snipped-for-privacy@highlandsniptechnology.com wrote in

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John,
Tim may have a good point,
long ago I dissasembled (bought a load for 1 dollar or so on ebay)
one of those coils,
 http://panteltje.com/pub/mains_filter_coils_disssasembled_IMG_0149.JPG
core is very tiny.
Only one half shown here other is missing.

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