Re: SSTC idea - DRSSTC ?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "chris swinson by way of Terry Fritz <teslalist-at-qwest-dot-net>" <exxos-at-cps-games.co.uk>



----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Wednesday, March 19, 2003 1:42 PM
Subject: Re: SSTC idea - DRSSTC ?


 > Original poster: "Stephen Conner by way of Terry Fritz
<teslalist-at-qwest-dot-net>" <steve-at-scopeboy-dot-com>
 >
 > At 10:16 18/03/03 -0700, you wrote:
 > >Original poster: "chris swinson by way of Terry Fritz
 > ><teslalist-at-qwest-dot-net>" <exxos-at-cps-games.co.uk>
 > >
 > >
 > >DRSSTC ?? Whats that all about, is there anything online which explains
the
 > >idea behind it ? It sounds interesting for sure!
 >
 > The DRSSTC (Dual-Resonant Solid State Tesla Coil) is a clever idea by
Jimmy
 > Hynes. I'm not sure if he ever wrote it up on the web. His intention was
to
 > make an SSTC that could compete with spark-gap coils in terms of streamer
 > length. This was the point of the OLTC too.
 >
 > http://hot-streamer-dot-com/chunkyboy86
 >


I can't seem to open the doc file ?  Does anyone have a basic diagram to how
this is setup and how it is supposed to work ?

cheers,
chris










 > The DRSSTC is like an ordinary SSTC, but the primary circuit is tuned with
 > a series capacitor. So, instead of getting a constant output, you get the
 > notched envelope waveform that you see with a spark-gap coil, but
 > backwards: it grows bigger with time instead of decaying. The control
 > circuit fires the inverter in a burst that lasts exactly one beat of the
 > envelope.
 >
 > Because it's running in very short bursts, you can really push the
 > circuitry to the limit, so primary currents of hundreds of amps are
 > expected. In this respect, it's similar to the OLTC, but the control
 > requirements are more challenging. The OLTC just turns all its transistors
 > on, waits till the first notch, and then turns them off on a current zero.
 > The DRSSTC driver has to fire out a pulse of RF at just the right
frequency.
 >
 > The drive circuits are trickier too because you are driving a full bridge
 > of IGBTs at hundreds of kHz. Plus, nobody actually knows if IGBTs can
stand
 > that much current in a high-frequency inverter, even though it is resonant
 > with zero-voltage/current switching. IGBTs are pretty slow compared to
 > MOSFETs. The switching losses might be massive. The drive frequency would
 > be critical too: passing that much current, if you wandered off the
 > zero-voltage/current switching instant, you'd be scraping the remains of
 > your IGBTs off the ceiling. Therefore you would probably need a
 > feedback-type circuit. And, being pulsed, it would have to start instantly
 > and reliably, which can be a problem with today's feedback SSTCs.
 >
 > On the other hand, the bang size might well be bigger for a given set of
 > transistors/supply voltage than in the OLTC. Then again it might not be:
 > Heating in the IGBTs is what limits the bang size in both OLTC and DRSSTC.
 > The DRSSTC will probably have higher losses. I'm betting on the OLTC,
which
 > is why I built one.
 >
 > Either way, the DRSSTC is serious cutting-edge stuff and I wish its
 > designer the best of luck. If it were me, I'd be inclined to build a small
 > prototype with MOSFETs that ran off 36 volts or thereabouts.
 >
 > P.S. The SSTC built by Vladimir Mazzilli might be a good basis for a big
 > DRSSTC. It already has the resonant primary, high-powered IGBTs, and
 > feedback driver (in fact the whole thing is a power oscillator) and all
you
 > would need to do is rig up an interrupter circuit with first-notch pulse
 > width, change the gate zeners to give 30 volts gate drive, and crank the
 > power supply voltage up to something suicidal like 500 volts. You may need
 > to reduce the value of the DC link inductor too. I don't know if this
would
 > affect the circuit in other ways.
 >
 > Steve C.
 >
 >
 >
 >
 >