Re: OLTC Thoughts

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

Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-qwest-dot-net>" <bert.hickman-at-aquila-dot-net>

Richard, Antonio, and all,

I've seen Richard Hull's thyratron powered coil in operation, and as
Rich Wall indicated, it only began to do an energy transfer from primary
to secondary, firing for 1/2 cycle, and then shutting off. It used a
small hydrogen (H2) thyratron (type 3C45) with no reverse conduction
diode. So, when fired, it conducted for the first half cycle, then shut
off at the next current zero crossing. There were many discussions about
using hydrogen diodes or high current high voltage rectifiers to conduct
the primary's reverse current since most thyratrons don't do this very
gracefully or for very long. For a complete energy transfer, multiple
triggers would be necessary, one for each positive half cycle until the
primary to secondary energy transfer completed. The beauty of the H2
thyratron switch was that is could quench "on a dime", permitting
tightly controlled quenching experiments. By triggering only once, only
a relatively small amount of energy was actually transferred to the
secondary. 

By using the MOSFETS to provide forward primary current, and then using
a high current diode to conduct in the reverse direction, Terry's OLTC
offers the capability to simply, yet tightly, control the degree of
quenching. 

Best regards,

-- Bert --
-- 
Bert Hickman
Stoneridge Engineering
"Electromagically" Shrunken Coins!
http://www.teslamania-dot-com


Tesla list wrote:
> 
> Original poster: "Wall Richard Wayne by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <rwall-at-ix-dot-netcom-dot-com>
> 
> Antonio,
> 
> > > Richard Hull's H2
> > > thyratron magnifier, by necessity, quenched at the first zero crossing
> of
> > > the wave form.  So only the positive half of the energy cycle was
> passed to
> > > the primary.  While a very interesting design, it is not a spectacular
> > > performer, if one measures performance by spark length.  It's a
> phenomenal
> > > research device though.
> >
> > This is quite strange. A Tesla coil, or a magnifier, can't operate
> > correctly without at least two polarity reversals in the primary
> > current.
> > If the current is interrupted after the first half-cycle, only a small
> > fraction of the primary energy is transferred to the secondary.
> > Where is this magnifier described?
> 
> Yes, it does seem quite strange.  Even though with only one half cycle
> there is still some energy transfer.  The coil does spark and has a
> peculiar harsh audible hum.  But, overall performance is inhibited.  I
> posted this point because Terry's OLTC will have similar very quick
> quenching which may inhibit expected performance.  I have no doubt he will
> figure out timing problems though.  A fly back diode on each switch will
> get it through one complete cycle.
> 
> Richard Hull designed and built this thyratron maggey.  He has demonstrated
> it at the TCBOR Teslathon.  I'm sure many on this list have seen this coil
> in action.  Richard is no longer on this list, but I'm sure he would advise
> you where it's written up.
> 
> RWW