Re: [TCML] Using thyristor to dump energy in one half cycle?

[Carl Noggle <cn@xxxxx>]

I have always thought you could use an SCR with a back diode.  You would 
have to keep the gate turned on until the oscillations had died down, 
but that's not hard.  The problem would be the low impedance--unless you 
used a series string you would have to live with about 1kV, so you might 
have only a one- or two-turn primary.  For my coil using 10kV and 1800 
watts, you would have a one-turn primary running at 1000 volts and 1000 
amps.  Actually, that sounds like a lot of fun and a bit of a 
challenge.  You would need an SCR and a diode with a high I^2t rating, 
but these are easy to get.  For smaller coils, it would be even easier, 
of course.

A hollow-anode thyratron would serve, or a grounded-grid or back-lighted 
thyratron, or if you want to get hairy, an ignitron.  But the advantage 
over a spark gap might not be worth the $$$$$$$$$$$$$$$$.

Somebody should try an SCR TC.

---Carl









> Jolyon,
>
> Richard Hull tried something like this a number of years ago.  He used
> a hydrogen thyratron, but his coupling wasn't tight enough to take full
> advantage of the idea.  He considered using back to back thyratrons
> to let more than one half cycle pass.  Another idea would be to use
> a diode to pass the other half cycle.  It's hard to get very close
> coupling without primary to secondary arcing problems in a TC.
> Hydrogen thyratrons are damaged by reverse currents, so it's
> important not to let the current reverse.  There are special
> (expensive) thyratrons available that can handle some degree of
> reverse current.
>
> Cheers,
> John
>
>
>
>
>
>
>
> -----Original Message-----
> From: vatercox<vatercox@xxxxxxx>
> To: tesla<tesla@xxxxxxxxxx>
> Sent: Wed, Nov 16, 2011 12:01 pm
> Subject: [TCML] Using thyristor to dump energy in one half cycle?
>
>
>
>
> Dear List,
>
> I am asking if it would be possible to use a thyristor or thyratron as the
>
> switching element in a TC if it could be arranged that all the energy in the
>
> primary cap would be "dumped" (i.e. the capacitor completely discharged) within
>
> one half-cycle of the oscillatory period. I am under the impression that
>
> thyratrons and thyristors (possibly excepting  hydrogen thyratrons) are in the
>
> main considered practically useless for TC  due a reputation for "slow"
>
> switching. Would some kind of "hard" switching -e.g. extended application of the
>
> gate current in an SCR after the primary cap had discharged- be able to
>
> accomplish this and if so would it be of any benefit?
>
>
>
> Jolyon
>
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