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Old 10th March 2011, 11:52 PM   #10991
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Quote:
Originally Posted by Pano View Post
Just as a sidebar to the main discussion:
Will these alleged effects be important to transformers that handle larger signals, such as ~1V in a line level transfo? Or even 100+ volts in an OPT?
Or are they just tiny signal problems that affect moving coil and ribbon mic signal levels?
Well, speaking for myself, I haven't seen anything yet that would cause me to start losing any sleep.

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Old 11th March 2011, 12:00 AM   #10992
SY is offline SY  United States
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As I mentioned before, I tried this with millivolt signals driving the primary of a large OPT (vintage 1980 or so, 1250 ohm: 16 ohm, CT) through series resistors to try to measure the phenomenon that Menno predicted. Couldn't find any issues despite the transformer having a very conventional EI oriented ss core and being made for large signals (600V at hundreds of milliamps). Maybe there was something special about this transformer that I wasn't aware of, but I doubt it.

And of course, we don't see any significant distortion from MC step-ups or good mike transformers, though to be fair, the MC step-ups driven by very low source Z.

So no sleep lost here, either, at least not because of this hypothesized aspect of transformers...
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Old 11th March 2011, 12:20 AM   #10993
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Which means that even a simple length of wire would also exhibit the same frequency dependent "eddy current noise," yes?

se
Yes, but in this case the real part of the frequency dependent impedance due to skin effect will contribute sqrt(4KTR). So we have experiment no 2.
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Old 11th March 2011, 12:27 AM   #10994
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even when natural gravitation examples such as tornados are around us. Everyone knows anti gravity is only pursued by fools.

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I see you have been reading the "vortex" folks. You can also keep a ball up with a backwards vaccum cleaner. The energy to make a tornado is staggering and it only gets you out of Kansas.

I do the Golf Channel now and some revisiting of Poe.
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Old 11th March 2011, 01:43 AM   #10995
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Thanks Joachim, your input has been very helpful.
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Old 11th March 2011, 05:38 AM   #10996
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Thanks. That pretty much answered my next question, too.
Now I can sleep better.
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Old 11th March 2011, 05:45 AM   #10997
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Quote:
Quote:
Originally Posted by Steve Eddy
Which means that even a simple length of wire would also exhibit the same frequency dependent "eddy current noise," yes?
Quote:
Quote:
Originally Posted by scott wurcer
Yes, but in this case the real part of the frequency dependent impedance due to skin effect will contribute sqrt(4KTR). So we have experiment no 2.
"Eddy Current Losses in Transformer Windings and Circuit Wiring"
http://focus.ti.com/lit/ml/slup197/slup197.pdf

Regards
George
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Old 11th March 2011, 06:14 AM   #10998
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Thanks. That pretty much answered my next question, too.
Now I can sleep better.
Yeah, but that'll just make the marketing departments work that much harder.

Click the image to open in full size.



se
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Old 11th March 2011, 06:24 AM   #10999
jam is offline jam  United States
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Steve,
..............here is something more your speed.

Transformer Animation - Alternating Currents | Tutorvista.com

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Old 11th March 2011, 06:42 AM   #11000
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"Eddy Current Losses in Transformer Windings and Circuit Wiring"
http://focus.ti.com/lit/ml/slup197/slup197.pdf
Yes, I read that earlier.

I see you emphasized "Losses" in the title, but you overlooked "Windings."

He says absolutely nothing about the core materials, which is what is being discussed here.

He's just talking about skin effect and proximity effect in the windings, specifically as it relates to transformers for switchmode power supplies which use high frequency pulses and depending on how much power is needed, rather large gauge wires which make skin and proximity effects much worse.

What we're talking about is audio transformers, which are using wires on the order of 42 gauge. With such small diameter wire, skin and proximity effect are effectively non existent at audio frequencies.

And again, it's not the windings that are at issue, but rather the alleged added noise due to eddy current losses in the core.

se
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