Re: remote location of NSTs - away from coil base?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>

Hi Bill,

> > Original poster: "resonance" <resonance@xxxxxxxxxxxx>
> >
> > Avoid using coax for any HV leads with either pole xmfrs or nsts.
> > It can produce incredible capacitive resonance effects where you
> > don't want them --- in your power supply.  Coax is great for DC but
> > not the best idea for AC.
> >
> > We used coax once with a pole xmfr and the resonance effect
> > (Blumlien effect) was so powerful the spark was jumping 16 inches
> > across at 14.4 kV bushing on the pole xmfr to get to ground.
>
> I thought the Blumlein (transmission line voltage reversal) effect
> has to do with the spark gap firing.  How would it matter whether the
> lines are carrying AC or DC then?
>
> > Use silicone GTO neon sign xmfr wiring (local neon shop) with 2
> > leads to send your power over to the base of your oscillator.
>
> Much more expensive, and how do I keep secondary strikes out of that
> wire?  That's why I wanted to use coax.
>
> > It's also nice to use a pair of 25 Amp Supercons (DigiKey
> > Electronics) plugs and matching receptacles to terminal the leads
>
> Are those the high current Superior Electric connectors?  I don't see
> them listed at DigiKey, not finding them with searches there - got a
> part #? Not that I'm likely to use them, I remember them being very
> expensive.
>
> > --- this allows you to rapidly plug/unplug your power leads into
> > the oscillator base.
>
> I had planned to make my own HV connectors, but that design wouldn't
> work with silicone or other soft-insulation wire - works best with
> solid-poly coax core.
>
> Why bother with a 25 amp connector for the HV leads?


I like using a length of surplus high voltage x-ray cable for the transmission
line from high voltage transformer to the primary tank circuit. High voltage
x-ray cable, which is used to transfer the HV DC from the x-ray transfor-
mer to the x-ray tube head, is pretty much designed like coax cable on
steroids! It's way too expensive for the hobby level budget when purchased
brand new on the retail market (I think it runs $10 to $12/ ft) but can some-
times be found surplus in good used condition on ebay for a small fraction
of this cost. I, like you, don't like the idea of streamers hitting 
and possibly
damaging my transmission line and this cable answers that issue well.

I am aware of the well documented Blumlein effect but "I" have personally
never witnessed its occurance to a noticable degree with my x-ray cables
when using them as HV transmission lines for my large Tesla coil. I HAVE
noticed it when hooking them up to the HVDC of an x-ray tranny and ran
up the HVDC output while leaving the live ends open circuit (really HOT
high voltage DC sparks start popping that are like the discharge of a HV
capacitor that will overvolt the x-ray transformer itself if one is 
not careful!)
You can run a "single" run of it from your transformer to your primary
circuit, using the center conductors as the "hot" and the outer braid shield-
ing as the "ground" lead. Of course you will need to make sure to seperate
the outer pig tank ground terminal (60Hz AC mains ground) from the "ground"
side output HV bushing of the pig (dedicated RF ground). You would need
a 2-bushing pole pig to keep the mains and RF grounds seperate in this setup.
BTW, since Blumlein is a result of capacitive resonance on the line, 
it seems to
me that even running plain high voltage GTO cable will still subject 
the cables to
some capacitance since they are going to be lying next to the ground
which would act like the opposite plate of a capacitor from the HV line
lead.? I suppose I just don't have the proper length (about 40 ft) of x-ray
cable to cause capacitive resonance with the pole pig's output to get the huge
Blumlein effect voltage gains.??

David Rieben