RE: [TCML] RE: Splicing wires - Secondary Coil

["McCauley, Daniel H" <daniel.h.mccauley@xxxxxxxx>]

Steve,

Well, first of all don't, don't assume. I never said anything about a reflection or anything regarding secondaries behaving like transmission lines. I simply stated it was an impedance discontinuity at the point of splicing.  This could be as simple as a bad solder joint, poor connection, etc... at the splice due to poor workmanship.  Or maybe its the sharp point as you mentioned that causes some break-out and makes the system tune to that point.

And I don't have any measurements handy, but I have plenty of bad experience with splices.  Just last year, I had a magnetics house down in Mexico wind 100 small coils for a customer of mine.  These were for a small self-tuning SSTC coil.  After having each of the first (5) coils I tested fail about 85% up the coil, i began to suspect that something was amuck.  Upon close inspection of the coils, i noticed a splice point. After some discussions with the manufacturer, it was determined that the coils were all wound initially, but too short, so they decided to splice and continue winding the coil to spec.

Now electrically (with LCR meter), these spliced secondaries measured just fine, and from visual inspection, you would never even notice the splice unless you used a magnifying instrument.  But when connected to a self-tuning driver, they all failed at that splice point.

Now I certaintly don't claim to know all the theoretical and mathematical explanations to why this occurred, and I'm *certaintly* open to suggestions from other people regarding this, but I do know that they were all failing at this point, and the only thing I can think of is some sort of impedance discontinuity due to the splicing causing this problem.

So again, its my opinion that if you have a self-resonant system, i don't recommend splicing your secondaries.

Daniel McCauley
http://www.easternvoltageresearch.com
DRSSTC, SSTC, Flyback Kits and Components!


>If you are going to make your point #2, i demand to see some 
>measurements (or even simulations, >or even supporting math), otherwise i dont believe it for a second.  Of course i have seen the instability during ground arcing of a SSTC, but that really is a BIG change in impedance which >DOES cause the mode of the system to change.  And this was always with secondary coils that didnt have any splices in them, so we cant blame it on that.

Steve

On Sat, May 1, 2010 at 6:46 AM, McCauley, Daniel H < daniel.h.mccauley@xxxxxxxx> wrote:
> 2.  If you are running a self-resonant (antenna or current feedback
> based) coil, then it is NOT recommended to splice the wires.
>
> The reason for this is that with a self-tuning system, there will be 
> some impedance discontinuity at the point of splicing.  And the 
> self-tuning feedback network has a high probability it will detect 
> this continuity and tune the coil accordingly making that 
> discontinuity the node where voltage is maximum.  What happens next is 
> that your coil is now tuned at that point, and high voltage peaks and destroys your secondary at the splice point.
>
> This is one of the drawbacks with self-resonant systems.
>
> Which makes me think, maybe some sort of notch filter in the feedback
> network would prevent this.   Hmmmm . . . sounds like an idea!
>
> Daniel McCauley
> http://www.easternvoltageresearch.com
> DRSSTC, SSTC, Flyback Kits and Components!
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