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Re: [TCML] predicting phase shift

Any time the current is changing dynamically the inductance also changes
--- it pure physics and basic E.E., not smoke and mirrors.

Dan McCauley addressed some of these concerns in his book on Modern DRSSTCs
which he wrote about 3 years ago.

You will see the light when you try it.  Been there, done that, about 7
years ago.

D.C. Cox

On Tue, Jun 23, 2009 at 7:48 AM, Finn Hammer <f-h@xxxx> wrote:

> DC Cox skrev:
>> Zapp's phase shift correct will not work.  Yes, like smoke and mirrors it
>> works in the circuit he has, but when he hooks it up to a real TC load it
>> is
>> not going to work properly.
> Since I am the only person having posted anything related to this subject,
> not just recently, but in all the 10+ years I have monitored and contributed
> to this list, I feel compelled to assume that you are referring to the
> contents in my paper: "The Hammertone Predikter".
> Let me first point out, that to you, sir,  I am Mr. Finn Hammer, of
> "Hammertone" fame.
> I also strongly object to your change of subject heading.
> It might also be a good idea to read the paper twice, and discover the
> finer points, like the link to this video.
> It shows the circuit driving what would appear to be a tesla coil:
> delivering 8+ feet of spark, with no snubber or any other overvoltage
> protection of the IGBT`s, despite the 800V buss voltage.
> http://www.youtube.com/watch?v=S533gY4R_QI
> Zero crossing under a load can be achieved as long as there is not change
>> --- no change in potential or no change in current.  What may look like
>> perfect zero crossing at full load may cause very high current switching
>> before you get to the full power level.  This is not shown on the video
>> because no load is connected.  When a real load is connected the
>> currents will definitely dynamically change.
> Others, and perhaps even you, will be interested in this video, showing the
> relationship between the predicting signal,  the tank current, and the
> voltage across the load:
> http://www.youtube.com/watch?v=nLcSoo3LcME
> What you see is a remarkably spikeless Voltage square wave, voltage being
> reversed quite close to the current zero crossing, and the feedback
> predicting signal, which does not change. Neither "rapidly, nor
> dynamically", as you so eloquently put it. This is with the primary current
> being varied between 50A and 500A.
> Those of us that sit down in front of a scope and find resolve to
> challenges in the nanosecond range find it hard to take terms like "Rapid
> change of signals" seriously, I might add.
>> With no load applied and just adjusting the firing angle of the gate
>> drives,
>> you can absolutely set perfect zero crossing.  When the load is
>> dynamically
>> applied there is a slight shift in phase angle because the inductance
>> changes due to the current changes --- which are very rapid and dynamic.
>> The overshoot he is trying to null out is not a zero cross over problem.
>> Overshoot, which is very high in his waveforms, and which he is trying to
>> null out, is caused by improper turns ratios on the gate drive
>> transformers.  This is where the overshoot problem is occuring, not from
>> the
>> phase angle.
>> If you watch the you tube video you will see the amplitude change and
>> there
>> is no change in phase shift.  You need to adjust and perfectly match your
>> gate drive transformers to correct this problem.
>> The only way to make it work is dynamically follow the rapidly changing
>> load
>> perhaps with a microprocessor.  This would be a step in the right
>> direction
>> to solving this problem which tends to amplify itself as coils get larger
>> and the power levels increase.  There is no simple, easy solution.  It can
>> only be solved in a dynamic fashion accurately tracking the currents.
> I see no point in responding to the rest of your complaints, as, to me,
> they are poppycock.
> But then, I asked for "peer review". Do you _really_ consider yourself as
> my peer?
> Cheers, Finn Hammer
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