Auroratek demonstration from Bill Alek at TeslaTech conference

[G4RR3ττ]

Mark,

As I pointed out, the saturable reactor circuit is a close approximation of the first half of Alek's circuit--and by no means did I imply it was exactly the same to its entirety. As for my results, they demonstrate that coupling between secondary windings placed on isolated cores to a commonly wound primary winding can be very high. Nothing you've said refutes this. I want to point out that I didn't claim my circuit was exactly the same, only that certain elements are very similar.

I agree that his transformer would have a worse k factor than my circuit due to reasons I've already stated as well as the ones you have pointed out. We both agree that his exact arrangement will give a less than satisfactory k value. What we don't agree on is the exact amount of coupling physically possible. Obviously we both have our own experience and assumptions to support our arguments. Therefore, both of us need to prove our point more conclusively, either using a 3rd party authority (e.g. a texbook) or physical experiment.

[TinselKoala]

Is there anything in the way of circuitry on the "support board"? Sure seems like an expensive way to make a simple support for another part if there isn't any circuitry involved.


I realize that in this particular case it probably doesn't make much difference, but here is a question I would like to see asked, every time a demonstration of power happens and a scope channel is observed to be AC-coupled.

"Mister Alek, I notice that both your scope channels are set to AC-coupled. This removes any DC component in the signal, doesn't it? It is the equivalent of putting a capacitor in series with the probe tip as you measure, blocking any DC from reaching the scope's electronics, isn't it? So really, there could be literally any amount of DC power flowing in the system and your scope measurements would not show it. Is that right?"
Follow up:
"The AC coupling setting also moves the displayed trace up or down so that its average is on the channel baseline, doesn't it? What exactly does this do to the _values_ measured for peak voltages, the baseline zero crossings, and math that is done on the vertical values of the AC-coupled traces?"

[TinselKoala]

What, people don't think this is an issue, or that I am making it up? AC Channel coupling is by far _THE_ most misunderstood aspect of scoposcopy. Here is an excellent white paper from National Instruments that describes the issue, with waveform examples.

http://www.ni.com/white-paper/14753/en/

[G4RR3ττ]

TK,

Interesting point about the PCB. However I disagree with the AC-coupling at the scope, it would show everything but the DC-offset. Are you implying that a DC-offset is doing some magic in the background? It's entirely possible that the secondary and primary aren't galvanically isolated and the PCB may be involved in some underhandedness. Certainly not out of the question. To be honest I played around with what I felt was an "equivalent circuit" and proved many of Mark's points wrong regarding both coupling efficiency and the phase angle at the primary, but nothing was observed that paralleled Alek's SFT effects. Fundamentally the effect--if real and not a bunch of smoke up everyone's ace--must be one to do with physics of the core material. Otherwise I'm just not seeing how the effect can be had through classical lumped elements and transmission line theory.

All I see the NI article pointing out is basic high-pass filter phenomena when the AC-coupling is engaged, particularly important with rectangular waveforms where large harmonic content is prevalent (mostly affects the LF spectrum of the signal). Outside of this it's not that big of a deal in my book, and I stare at scopes all day long. But maybe I'm desensitized...

Evidence against the DC-offset theory is the fact that "TRMS" measurements really aren't taking place. Most DMMs do not compute the true RMS of both the DC and AC component at the same time ("AC+DC"). That is to say, only the DC or the AC values are being reported. Few meters actually compute the AC+DC or TRMS, one in particular is the venerable HP 3403C, which uses thermal methods and is good up to 100MHz. So I think its safe to say any DC-offset isn't being measured even if it is leaking into an un-isolated secondary winding.

[TinselKoala]

as I said it is probably not an important issue _in this case_ as far as the measurements per se go, but it indicates a certain non-expertise in measurement and scope use, which is why I would like to see the question posed just as I have presented it. Here we often deal with claims of OU that are close to the noise floor, and cases of  OU indications have been tracked down to improper use of channel coupling. This is a very easy way for someone to inject lots of power into an input if they want to be deliberately  misleading, or to deliberately under-read an output power. Whenever I see AC coupling used for anything other than examining small signals on top of large known DC offsets, I want to know exactly why the channel is coupled that way, and I want to know that it does not affect the math that is performed on the traces.
It has even come to my attention that some qualified professionals don't even know what AC actually _is_. The NI white paper is an example. The writer refers to a sinus signal that is 100 percent above baseline as "AC". It isn't, though. It is a fluctuating level of current that always flows in the same direction. It does not become AC until there is current reversal happening, and this will not happen until the voltage signal actually does dip below the zero baseline and become negative at the measurement point. IOW, if the DC offset is _greater_ than the amplitude of the ripple, you don't have any AC at all because the current does not alternate, it simply rises and falls in magnitude in the same direction. It is only correct to speak of "AC with DC offset" when the offset is smaller than the ripple and zero-crossing actually happens.
This is overly pedantic and I generally know what people mean when they speak about AC with DC offset, etc. but it's easy to prove what I'm saying, if you don't believe or agree, with an LED, the scope, and an FG that has adjustable offset and can put out a 1 Hz sine wave. You can display the same sinus signal and have the LED on 100 percent of the time, off 100 percent of the time, or anywhere in between depending on the DC offset setting of the FG. LED on 100 percent of the time: NO ac! And if the scope is AC-coupled the signal will look exactly the same _vertically_ and appear as the identical AC signal no matter whether the LED is on 100 percent, off 100 percent or anything in between. You will be able to report and demonstrate all kinds of strange behavior if you just keep your scope on AC-coupled.

So I think its safe to say any DC-offset isn't being measured even if it is leaking into an un-isolated secondary winding.

That is exactly  my point wrt the scope but I don't know about the meters. DC offsets could be contributing to the actual power IN without being measured on the scope. However I think they would show up on the output DMMs, being included in their math. This is an interesting issue and I don't know the answer wrt the DMMs. I wonder if Poynt99 or MarkE can speak to this issue.

ETA: both of Alek's output DMMs are Flukes, one is a 187 TRMS I believe and the other is more modern but also, I believe, a TRMS meter, possibly a 175. I refer you to page 3-4 in the manual:
http://assets.fluke.com/manuals/187_189_umeng0200.pdf

If it works... it's a FLUKE!

(also... we know that a ripply DC signal applied to a primary of a transformer will, unless the core is saturated by the DC, produce an AC output in the secondary, with an amplitude that is determined by the p-p amplitude of the original ripple on the DC input. Right?)