Re: SIDAC Spark Substitute

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Peter Terren" <pterren1@xxxxxxxxxxxx>

Derek and Shaun
I am not sure what I can push the SIDAC's to and have not burnt them out 
yet although they get warm on a short run. Currently dumping 5.2kV 30nF cap 
(0.4j) a few times a second into 5 primary TC turns which is not enough for 
spark growth. I am not sure about how well they quench as well.  Clearly 
they do a lot better with a high inductance coil such as an ignition coil. 
I should try this on my 18 x 48 inch coil with Fres of 38Hz.  It may work 
better but still look proportionately small.
The di/dt is 125A/uS is enough to get to full rated current in one uS. Peak 
current is 130A for 10uS pulse for this small package .  By comparison a 
CDC cap of the larger size I use (0.33uF) has a 600A peak and 1900 V dV/dt.
I think I can do better as I have been cautious so far.  I need to do some 
CRO measurements first though and put them under oil. It is not likely to 
be a serious proposition for a TC (but what if they bring out a fast SIDAC 
'brick'?).
I have had a Plasmasonic 1 board for a year or so, unpopulated as yet.  Dan 
reassures me it will be worth a lot one day!  I have some CM300 IGBT's 
rated at 600A so aim for a DRSSTC or Royer type circuit at some stage.  I 
also have a 60kW transmitting valve for 30MHz so a 'small' VTTC is also on 
the wish list.
Peter (Tesla Downunder)
http://tesladownunder.iinet.net.au

> Original poster: Shaun Epp <scepp@xxxxxxx>
> ...It's a great idea in theory but unfortunatly not practical.  The SIDACs 
> wouldn't be able to handle the current which is hundreds of amps pulsed in 
> a tesla coil primary circuit.  I've never seen high current SIDAC's but 
> I've played with ignition coil like circuits too using them.
> You could look into OLTC type telsa coils(I'm not sure if they're simpler 
> or not compared to an SSTC) or obtain a PlasmaSonic board that someone on 
> the list isn't using and make yourself a SSTC.....
> Shaun Epp


> Original poster: "Derek Woodroffe" <tesla@xxxxxxxxxxxxxxx>
> ...I tried using a SIDAC device, to replace a spark gap, with poor results,
> They have similar DI/DT times as Triacs and that is what I put my bad
> performance down to. I also tried them in an OLTC type circuit with a
> capacitor and DC....> I must admit to being impressed with the IC sparks 
> though. They should work
> ok in very low Frez circuits e.g cored transformers, or maybe big TC's
> Derek

> ----- Original Message ----- : "Peter Terren" <pterren@xxxxxxxxxxxx>
> > This is a proof of principle coil rather than a big performer. It uses 
> > SIDAC's in place of a spark gap As set up at present it is driven by a 
> > MOT transformer with the associated 11kV diode and 0.95 uF 2KVAC cap 
> > wired as a voltage doubler to provide 5.6 KV or so. This is dumped by a 
> > SIDAC or rather 22 in series each shunted by 1 megOhm.  Each SIDAC is 
> > rated to breakdown at 240V and has a 1A RMS or 20A pulse capacity.  The 
> > string of 22 SIDAC's will nominally breakdown at 5280V.
> >
> > Peter (Tesla Downunder)