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Re: dual MOT Tesla coil design is complete (fwd)

Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

Hi David,
When I started coiling with a 10kva pig, I was using my 13.5" diameter coil, the transformer thumped with fast current changes. I came across a 10 ohm 3000W resistor (HUGE!!). The resistor was wire wound on a very thick ceramic cylinder. I measured to the center and snipped the winding. Thus, I had two 5 ohm resistors on the same ceramic cylinder. I then paralleled these windings for 2.5 ohms and used this in series with my variac ballast.
The thumping was gone. I used it for a couple years, but was never satisfied with spark length. I eventually removed it. Spark length was better and brighter. The thumping I had originally experienced never did show up again, but then the coil itself had changed over time (added 12" length to the secondary, new primary, new sparkgap, etc..).
I guess my experience is that it certainly did smooth out the change in current curves, but it does dissipate power which robs coil processing power. Not terribly though. I think there are systems where it's appropriate and systems where it's not necessary. The coil itself and the drive system powering it determine it's worth, in my mind. 

Take care,
Bart


Anyone else have data from using resistance in combo with
inductance for ballasting their large coils? In my experience,
the resistance does tend to smooth out the choppiness of an
overpowered/poorly quenching RSG (good), but it also
really waste power in the form of heat (bad).

David Rieben


----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Wednesday, November 01, 2006 11:07 PM
Subject: Re: dual MOT Tesla coil design is complete (fwd)


> Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
>
> Hi DC,
>
> What is this 1kw per foot of spark for classical coils???  It has
> always been a sqrt(power) and not a linear relationship, has it not?
>
> BTW, my 2KW (real wall power) classical coil generates over 7 foot
> arcs. So this would make it 285 watts per foot by this reasoning, yes???
>
> Gerry R.
>
>
> >Original poster: "resonance" <resonance@xxxxxxxxxxxx>
> >
> >
> >with IGBTs the rules are changing.  Their much higher switching
> >efficiency and lower losses of heat and light lead to 450 Watts / ft
> >of spark performance as opposed to 1 kW / ft required in classic coils.
> >
> >
> >Dr. Resonance
> >----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
> >To: <tesla@xxxxxxxxxx>
> >Sent: Wednesday, November 01, 2006 5:59 PM
> >Subject: Re: dual MOT Tesla coil design is complete (fwd)
> >
> >
> >>Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
> >>
> >>Hi Terry,
> >>
> >>This would be great, but what ever happened to the sqrt(power)
> >>relationship???
> >>
> >>Gerry R
> >>
> >>>Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>
> >>>
> >>>At 10:48 PM 10/30/2006, you wrote:
> >>>>Hi DC,
> >>>>
> >>>> From what you say below, it sounds like you have the design but
> >>>> have not built it yet??  If this is true, where did the 7.5 foot
> >>>> arcs come from??
> >>>>
> >>>>Gerry R.
> >>>
> >>>My SISG does about 28 inch arcs at 4800 SISG firing volts with a
> >>>165nF primary cap.  It would do about 42 inches if I let it loose
> >>>with one MOT...  If DC can get 4800 Watts out of two MOTs, then
> >>>the spark length directly doubles to 84 inches or 7 feet.  But he
> >>>is using a bit larger primary cap too...  So 7.54 feet is about
> >>>right.  I am a little concerned about getting 4800 Watts out of
> >>>just two MOTs.  But DC might know tricks I have never dreamed of ;-))
> >>>
> >>>I have not thought much about the dual MOT SISG system...  But
> >>>others are now thinking far faster than me on SISG things ;-)))))
> >>>
> >>>Cheers,
> >>>
> >>>         Terry
> >>
> >>
> >>
> >
> >
> >
>
>
>
>