Re: Terry's DRSSTC -"different" H-drive functions...

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Antonio Carlos M. de Queiroz" <acmdq@xxxxxxxxxx>

Tesla list wrote:
>
> Original poster: Steve Ward <steve.ward@xxxxxxxxx>

> So im curious if you see any benefit to this situation assuming that
> say 3/4 of the bang energy is used up in the streamer, and then the
> driver is shut down, but with 2 IGBTs shorting it so to speak.  I have
> shown with my tests that breakout is achieved quite early when maximum
> power is achieved, so this may be a plausible situation that most all
> of the energy is used up anyway, but it couldnt hurt to get all the
> energy out of there ;-).

At least this is a way to trap the energy in the system. It will be
moving back and forth between the primary and secondary circuits as
in a conventional Tesla coil before primary quenching. But the
current and voltage in the primary may double. Maybe more than
double depending on the tuning. If only streamers are being
generated, they consume the energy quite slowly, and a substantial
amount of energy may be still available for transfer back to the
primary after the driver is short-circuited. Specially if the
coupling is high, and the energy transfer occurs in just a few
cycles.

> A situation with NO breakout would somewhat also imply that there isnt
> much energy in the system anyway, so 2X the voltage and current
> flowing afterward, while maybe not useful (or would this energy, now
> manifested, be coupled back to the secondary?), probably wouldnt be
> that devistating to a well built system... in any case what is the
> point of a tesla coil that doesnt make sparks? ;-).

Streamers are a relatively light load. Only arcs to ground would
consume a lot of the energy immediately. With just streamer loading,
most of the available energy may be transferred back to the primary
if the driver is short-circuited.

>  > So, my conclusion is that it's best to operate in the second case,
>  > letting the free-wheeling diodes return to the power supply the
>  > unused energy.
>
> I would agree there as well, seems like the "safest" way, but one must
> be sure to have *minimal* resistance and inductance between the IGBTs
> and the DC filter caps.  Its interesting to see the buss voltage raise
> noticably from this event, though maybe my scope probe was just
> picking up noise...

Of course. The DC caps must be mounted close to the bridge. If the
energy returns while they are being recharged by the power lines,
some voltage rise above the normal is to be expected. This can be
avoided by ensuring, by synchronization with the power line
frequency, that the bangs occur only when the capacitor is not
being recharged (good for the power lines too). The voltage rise
can then at most return the voltage to almost the maximum level.

Antonio Carlos M. de Queiroz