RE: Terry's DRSSTC - First light ;-))

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Malcolm Watts" <m.j.watts@xxxxxxxxxxxx>

Hi Steve,
           One question in response to what you said at the bottom:

On 7 Mar 2005, at 7:28, Tesla list wrote:

> Original poster: "Steve Conner" <steve.conner@xxxxxxxxxxx>
>
> Hey Terry,
>
> Congratulations on your first light! It sounds like it went very well
> with no _unexplained_ failures.
>
> As to what happens when an arc hits the primary. The di/dt caused by a
> streamer hit is colossal. You're basically connecting a big metal lump
> charged to half a million volts to your circuit, through about a foot
> of "wire". The streamer channel oscillates around its quarter
> wavelength frequency (less because of toploading) which on your coil
> would be about 40MHz.
>
> If you take the whole thing to be a resonant circuit ringing at 40MHz,
> with 15pF capacitance charged to 500kV then you can see that one
> quarter cycle later the peak streamer current will be pretty big
> because the inductance is so small. I got over 10 million amps in a
> quick back of the envelope calculation.
>
> Obviously that's not true because the streamer channel is lossy, but
> it still shows that there is a LOT of RF current trying to fight its
> way to ground through your primary and H-bridge. Since it's such a
> high frequency it will cause thousands of volts worth of di/dt
> voltages to appear across "ground" wires and such like, screwing up
> your circuit completely.
>
> I have thought long and hard about how to protect against this and the
> only solution I can think of is "Don't let sparks hit the primary
> EVER"
>
>
> Also I noticed Steve Ward said-
>
>  >I put metal caging around the base
>  >of my coils, which seemed to work fine until i switched to primary
>  >feedback (now the fence sucks up a lot of power for some reason)
>
> It sounds like you switched poles and are on the lower one now. I had
> a third winding on my dummy resonators connected to a light bulb to
> help me with tuning. I found that on the upper pole, the light bulb
> didn't light even though lots of power was being transferred. On the
> lower pole it lit brightly. The reason (as far as I know) is that on
> the upper pole, the primary and secondary currents are 180' out of
> phase so their magnetic fields cancel in the space around the coils.
> On the lower pole the fields add. Strange but true.

Agree with the field analysis but, where is all that transferred
power being dissipated?

Malcolm

>
> Steve C.
>
>
>