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Author Topic: Graham Gunderson's Energy conference presentation Most impressive and mysterious  (Read 193071 times)

Spokane1

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Well.... hmmm.

Now I'm confused. In previous posts you've said that the harvest pulse is turning the mosfets _off_ for a very brief time (see the diagram attached below) but now your mosfet Gate trace (CH4) looks like it's going HIGH and turning the mosfets _on_ for a very brief time and leaving them off for the remainder of the cycle.

So is the substantial current you are reading here, actually going through the mosfet body diode? What am I missing here?

What is that 50R, 10W load resistor? Is it a wirewound resistor?

Yes, I'll bet that ringing you are seeing is a "real artifact" in the sense that it is really happening but is something you don't want happening and may be caused by stray inductances due to wiring length or maybe the inductance of that load resistor.

Dear TK,

I have to check my wiring again. My intent was to have the MOSFET's on 99% of the time and then apply a short pulse to open them. But as you have noticed my pulse logic appears reversed. I even connected the gate drive logic to the complement output of the last timer to achieve this. I shall get right on this and see what is happening.

The load resistor is 2" long and about 0.250" in diameter. It is dipped in a brown ceramic like substance. It could be a carbon resistor, but it just as well could be something else. Would my new DE 5000 LCR Meter determine how much inductance we have here. Certainly worth a try. I shall also get a photo. Most all the power resistors I have above 5 Watts are the classical wire wound type. I understand that even the aluminum ribbed Gold ones are actually of the wire wound variety.

When my computer gets back from the evacuation exercise (The wife took off with it in her van) I shall do some simulations with added inductance across the back end storage capacitor.

I really doubt that I have enough bias magnets to saturate that huge iron core so I would suspect that this apparatus is still operating in classical mode, which is fine for now. I should probably look into making a purchase of some neo magnets.

If there is enough inductance to form a parallel tank circuit with the back end storage capacitor, then that would imply that those larges currents are actually oscillating around the loop as the Current Transformer reports.  I wonder how this is possible since that HF current (166 KHz) would have to flow through one winding. I would think that there would be a lot of attenuation there. I suppose that one winding could be in some kind of brief oscillation and not really impact the slower steady state of the core's magnetic flux very much.

Thanks for taking a look at this. I'm sure this issue will be one of many as we dig deeper.

Spokane1

Spokane1

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Dear TK,

That last scope shot was suffering from a misallocated ground reference connection (i.e. I plugged it into the wrong hole). The circuit was working properly but the scope was reading the wrong logic signal. The attached photo is what the last one should have looked like.

I adjusted the timing of the harvest pulse to a different part of the secondary current trace. In the second photo you can see the harvest pulse, but there is no impact to the secondary current. If there were some kind of parasitic resonance then I would think that I should get that ring no matter where the pulse took place, but I'm not sure of that.

The last photo is the load resistor in the circuit.

The next photo is the LCR meter measuring the resistance.

The next photo is the LCR meter reading the inductance of the resistor at 3.7 uH.  I haven't calculated what kind of resonate frequency takes place between a parallel 3.7 uH and a 1500 uF filter capacitor.

Perhaps this information will help determine what is going on.

Spokane

TinselKoala

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@Spokane1:

OK, thanks for the information. Your resistor is definitely a wirewound one with substantial inductance, but running the R and C values through my favorite resonant frequency calculator gives a frequency of about 2.1 kHz, much too low to explain the ringing you are seeing.
http://www.1728.org/resfreq.htm

Moving the harvest pulse as you have shown to a point near the zero-crossing produces much less ringing, since there isn't much current being interrupted. Plus, you've changed the vertical scale from 50 mV/div  in the ringing shot, to 100 mV/div in the non-ringing shot, so any ringing would show up correspondingly smaller anyhow.

Spokane1

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Dear TK,

After I replace some chips in my logic controller (that Smoke thing again) I shall explore making other measurements around the secondary and see what else is going on in the neighborhood.

I'm going to have to write up something to explain to people that we are working with two topologies here:

1. The Simplified single switch approach that I have been exploring because of its cost advantage.

2. The full Bridge and two logic signal approach that partzman is developing all those detailed simulations from.

Each approach serves its own purpose, but it is important that people new to this thread realize the difference.

Spokane1


Spokane1

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Dear TK,

Maybe I will not be swapping out my synchronous diode MOSFETS for the 200 Vdds models you recommended. Take a look at the Drain to Source voltage spike that is developed when the backend FETS turn off for 3 us. That spike is 575 Volts high, no wonder Graham uses the expensive 1.2 kV devices.

Normally I would be considering snubbing networks, MOV's, Zener Diodes, or added capacitance, but at this part of the circuit I fear that any of this could potentially diminish the OU effect we are looking for.

Do you happen to have a part recommendation that can handle these kinds of sharp voltage pulses? I suppose the price goes up with the Vdds rating.

Spokane1

Spokane1

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Dear All,

Here is one amateur's attempt at measuring the currents that are circulating around the synchronous diode. I'm sure that the well funded folks would be using three hall effect probes (at $1,500 to $3,000 each). In this approach I'm using three surplus current transformers that I got from eBay for $40 each. I figure the five (5) turns of wire through each probe adds some shunt inductance that is very small when compared to the 39 mH of the conversion transformer (mockup) winding.

What this experiment tells me is that I don't have any current circulating around one loop - the yellow trace. From the simulations I should have equal currents in each loop - less the 166 kHz burst, and that is not happening here.

Something to work on this weekend.

Spokane1

TinselKoala

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Are all three of the Pearsons on the secondary the same model 6164 with 0.05V/A sensitivity? Is the associated mosfet still working? The driver chip still working?

Spokane1

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Are all three of the Pearsons on the secondary the same model 6164 with 0.05V/A sensitivity? Is the associated mosfet still working? The driver chip still working?

Dear TK,

I believe that all the Pearson current probes are from the same manufacturing lot. Some one in the distant past scored a large lot of them (about a 100 or so) and was selling them at fire sale prices. I made a "Best Offer" and got lucky when I bought three of them.

I checked the Drain to Source voltage of both synchronous diode FET's and both reported the same 575V pulse, so it appears to me that the FET might be working, but I probably need to disconnect them and test them separately. I might have a bad (or improper) transformer connection as well.

This issue will keep me busy this weekend.

Thanks for the comments.

Spokane1

Spokane1

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Dear All,

Here are two scope shots contrasting opposed secondary's vs. aiding secondary's. The aiding topology results in greater current swings while the opposing approach reduces current swings. In each case the timing of the harvest pulse has to be adjusted since the peak currents take place at different times during the base period. By manually "tuning" the timing for maximum output the aiding connection will yield a 2 Watt output while the opposing output can only generate about 200 milliwatts at its maximum adjustment.

Please Understand that this is using a single front end switch (The simplified approach). If a full four switch H-Bridge were used then the results could be entirely different.

This exercise verifies that the three secondary currents can be observed. The impact of the current transformers on the circuit seem minimal with only 0.8 uH added on each transformer lead.

At this stage of exploration this mockup circuit is not even a very good DC-DC converter with 12 Watts in and only 2 Watts out for a COP of about 0.164.

The synchronous diode MOSFET Drain to Source voltage between the two approaches changes drastically. The third scope photo compares the two responses. The red trace is with the two secondary's opposing and it appears to suppress the voltage drop across the MOSFET's. The pink trace shows the same measurement with the secondary's aiding. Here the voltage drop is in excess of 250 Volts. This means that I will not be able to employ the more efficient 200V Vdds devices at this time. However I was able to swap out the input switch with the new device and got a 20% increase in output probably due to the lower Rds resistance.

First Photo - Aiding secondary's with harvest pulse timing in green at the bottom - blue trace is current through backend storage capacitor.

Second Photo - Opposing secondary's

Third Photo - Vds voltage rise during the MOSFET "off" time

Spokane1

Last Friday's scope trace was missing the yellow information due to a connection to the wrong tap.

k4zep

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Hi Mark,

Well you have your circuit working perfectly!  2 watts out, additive, 200 mw out, opposing.  I wonder what the output is with no harvest pulse, that is let the addition of the output pulses simply integrate into the output filter cap. This would show if the harvest pulse is adding to the mix!  It looks just like what a normal transformer would do under these conditions.  I'm way behind you in building, testing, etc.  Obviously we all are missing something here.  I would expect under normal conditions (without the implosion effect), we could get at least 70-80% output.  Have you considered looking at the output with only a capacitance that would resonate the output coils and see what the actual waveform is without the heavy integration. Perhaps this would also show if rectification of the ringing with the harvest pulse is occuring.  I'm sure all these questions are already on your mind. 

Thanks again for all the prodigious work you have done.

BTW, my K4ZEP email was hacked this weekend and everyone in all my saved list was sent an email with a funky message.
I fixed the problem (new 16 bit random generated password and 2nd level notification of susp. activity.)  It might slow the @@$@$ holes down that do this, I don't know.

Ben K4ZEP

Spokane1

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Dear All,

The value of the final load resistor has a large impact on the performance of this kind of circuit.

I started with a 50 Ohm 10 Watt resistor with an inductance of 3.4 uH. The performance was a COP of 0.167

I explored different values and the best one was a 10 Ohm power resistor with an inductance of .8 uH which raised the COP up to 0.274. That is a 60% improvement over the last reading.

This circuit appears to function best with the proper matching load, much like other AC circuits.

Spokane1

Enjoykin2017

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Dear All,

The value of the final load resistor has a large impact on the performance of this kind of circuit
....

Spokane1

Hello Spokane1

Why don´t use several parallel HEXFETs in linear mode as variable load resistor from couple of watts till some 200....300W ?
 
Thanks for interesting topic. Good luck !!  :)
Enjoykin


Spokane1

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Hello Spokane1

Why don´t use several parallel HEXFETs in linear mode as variable load resistor from couple of watts till some 200....300W ?
 
Thanks for interesting topic. Good luck !!  :)
Enjoykin
Dear Enjoykin,
A solid state variable resistor like you describe is certaily a viable option, but probably excessive in this appliction for the moment. I would jup for joy if I got 10 Watts of Output. I suspect that 20 Watts is probably the upper limit on this topology.
As it is I have a nice selection of classical low resistance rehostats on hand at the right price to carry on these preliminary experiments. Now if the power level gets beyond 20 Watts then a solution like what you recommend would be in order.
Spokane1
 

Enjoykin2017

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Dear  Spokane1

Thank you.!
I am waiting your further research.

Best wishes
Enjoykin

Enjoykin2017

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Ok, so, Scientifically, what do we know.

1: Input Winding appears to be 10, 12, 10, 12, 10, 12, possibly only 6 layers, of Litz Wire, about AWG 2 (6.54304 mm) @ approx 0.512664 Ohms per KM.

2: Output Coils consist of 4 Strands of Litz wire, each wound side by side, in a step winding configuration, Almost Bank Winding. Each set of winding's is divided into two parts. Each set of windings appear to be wound CW/CCW relative to the Core.

3: Output is DC, Rectified, via a circuit arrangement of possible 30 odd components.

4: Pulsed DC is the Input. As Reiyuki points out, about 33% 33% 33%

5: Permanent Magnets are arranged on the Device, thought to Bias, or partially saturate at least one half of the U Cores used.

6: U Cores are a Ferrite Material, apparently each has a different value of Permeability. No specifics that I know about have been shared as yet. (The below product guide, has an AL range from: 2300 to: 8700 (nH measured in combination with another ungapped core half))

7: U Core appears to be approximately square, a product selection guide can be found here: Ferroxcube, the largest U Core in this document is in the Picture below: (Which is about right, I have some magnets the same here (25 x 40 x 10) and they would fit about the same on the Core)

Chris Sykes
hyiq.org


Chris if your data are truth i can conclude only one thing. This device work on principles of parametric Ferro-Resonance in high flux ferrites.

Do you have valid frequency and timings of operation ??


PS: I think answer for existing phenomenon is here in this old Russian scientist´s book about Ferosondes.

The name of important topic is: "Еmployment of parametric resonance to increasing sensitivity of ferrosondes", with tuning procedures at end.

ps1: Tunning procedure obligatory need spectrum analyser // high bandwith // plus oscillograph.

ps2: Gunderson's huge ferrite core with help of strong permanent magnets can generate a lot of output power. At first estimation as far as 50 kWatt output but maybe a lot of more. Remember Tesla's car  "Pierce Silver Arrow", with 3 big ferrite rods.

Enjoykin2017