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

[Steve Ward <steve.ward@xxxxxxxxx>]

Hey Dan,

Yeah, i think thats pretty plausible.  Which i guess in either case (self
tuning or not), a splice can be bad news, perhaps more so in a SSTC where
the high duty cycles can mean quite large I*I*R heating in the secondary
itself, in which case a weak splice would be a nice hot spot, which could
either promote electrical breakdown, or promote the splice to fuse open.  So
perhaps this is the real distinction, whether the coil is "CW" or
"transient" might dictate how detrimental a splice may be.  Transient coils
(SGTCs, DRSSTCs) can probably tolerate the extra resistance would be my
guess, but probably have a lot more voltage stress on the winding.  As they
say, "your mileage may vary".

Steve

On Mon, May 3, 2010 at 2:37 PM, McCauley, Daniel H <
daniel.h.mccauley@xxxxxxxx> wrote:

>
> Hi Steve,
>
> I suspect, as others have pointed, that it probably was an electrical
> break-down first at the splice point.  And since the winding broke apart
> (open circuit), the system just self-tuned to the "remaining" portion of
> secondary - of course, making the broken splice point a spectacular failure
> as now the max. voltage was occuring at this point.
>
> I think what i wanted to say was that if you had a bad splice point in a
> manually tuned system, and that splice broke open, that resulting collateral
> damage to the secondary coil would be minimal since the coil would now be
> detuned, and not producing as much output voltage.
>
> As opposed to a self-tuning system in which if the splice point broke apart
> (open circuit), that the coil would now retune to that splice point most
> likely damaging the secondary coil/coilform beyond repair making any
> salvaging of the secondary impossible as you would now have your max.
> voltage somewhere midway up the secondary or wherever the splice point
> occurred.
>
> Does that make any sense?
>
> Thanks
> Dan
>
>
> Hey Dan,
>
> Can you please elaborate on how they "failed"?  Do you mean the oscillating
> frequency was wrong? or you had electrical breakdown?  If it were *only*
> breakdown of the winding, then it sounds like the simple answer was that the
> insulation was compromised, or the e-field stress was higher due to the
> discontinuity in *geometry*.  Seems perfectly plausible.  But if the
> oscillating frequency of the self-resonant system changed due to this
> splicing, and yet the coil still measures the same L as a non-screwed-up
> coil, then im still confused by this.
>
> I guess its possible the point fails right away with a short, which would
> certainly change the Fres.
>
> Steve
>
> On Mon, May 3, 2010 at 7:20 AM, McCauley, Daniel H <
> daniel.h.mccauley@xxxxxxxx> wrote:
>
> >
> > 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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> > Tesla@xxxxxxxxxx
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> >
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