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dc drive forT-coil and S-gap replacement?
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From: Greg Leyh [SMTP:lod-at-pacbell-dot-net]
Sent: Friday, January 23, 1998 6:32 AM
To: Tesla List
Subject: Re: dc drive forT-coil and S-gap replacement?
bmack wrote:
> >" Primary switch - Modified GTO
> > - no moving parts
> > - higher efficiency
> > - ultimate quenching capability
> > - much lower primary impedance(and therefore voltage) possible
> >
> > The coil itself would have a coupling between 0.25 and 0.35,
> > given the quenching ability of the GTO stack. Any energy that
> > was not absorbed by the arc would be actively switched back
> > from the secondary into the primary capacitor bank, thus reducing
> > considerably the actual demand from the prime power source. The
> > power factor would be around 0.98, due to the linear charging
> > ramp on the pri cap bank."
> >
> > -GL
> >
> Greg,
>
> Have you actually tried the this proposed circuit? Your monster coil runs
> at 38KHZ but you're using a rotory gap.
>
> So far as I know, thyristers are great at switching low frequency heavy
> loads, but have slow recovery times. Even 38khz is too fast for these
> devices- am I missing something?
I came _very close_ to going the GTO route, but given the number
of untested ideas (such as pri on the inside) that I had already
incorporated into the design, I didn't feel that I had enough time
for developing the pulse-forming networks and gate drive circuitry
for the GTO stacks. Besides, the prices for MGTO's are starting to
come down a little, now that the development costs have been
amortized by the good folks at CERN, and others.
The GTO's would have worked well for this coil, as the di/dt(max)
in the primary is less than 700V/uS. The di/dt rating is more
directly the limiting factor, rather than frequency. And as the
coil size becomes even larger, solid state switching becomes
ever so more the practical choice over a rotary gap.
Given the mechanical and dynamic problems I've encountered
with balancing a large 4-rotor system, I believe that this is
the last rotary gap that I will ever build.
-GL