Re: Thyristor driven coil ??

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Greg Leyh <lod@xxxxxxxxxxx>

Two performance parameters for thyristors limit their use in Tesla Coil 
work;  the dI/dt rating and the recovery time, or 'off-time' as called by 
some mfrs.

Most garage-scale coils have primary waveforms with dI/dt slopes of several 
kA/us.  Only the 'interdigitated gate' thyristors can handle such a slope.
More critical is the thyristor recovery time; the period after conduction 
before the device can once again support its rated voltage.
Typ times are 100's of usec, where considerably shorter times [10's of 
usec] are needed to properly quench.

-GL

> Original poster: "James Robinson" <james.robinson@xxxxxxxxx>
>
> Hi, just a speculative thought - has anyone ever tried (or would it work) 
> to use high power thyristors to replace the spark gap in a standard TC?  I 
> have seen modern "puck" thyristors capable of switching over 2kA at over 
> 8kV continuously and dV/dt ratings of several thousand V/us.  I may be 
> missing a vital point here - other that the extorsionate cost of the 
> things!)? One such problem might be the leakage current making it very 
> hard to get the tank cap to charge.
>
> It would have to be a BIG coil I suspect to get the resonant frequency 
> down as much as possible (a few 10s of kHz) thus reducing the dV/dt enough.
>
> just a thought...
>
> James R