Magnequench RSG (was magnetic field with flat spiral)

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

Original poster: "David Sharpe by way of Terry Fritz <twftesla-at-qwest-dot-net>" <sccr4us-at-erols-dot-com>

Ed, Marc

About 7 years or so ago, Alex Tajnsek, Richard Hull and I was doing experiments
at Richard's Lab using a 20 kV, 2.0kVA PT.  Alex setting on a LARGE piece
of PVC would pull a power arc off the single exposed power connection to
a ground target mounted at the end of a long (10') pvc pipe with grounding
rings midway up pipe (i.e. between Alex and discharger).  A very intimidating
BRIGHT arc would flair as long as 30-36" and was difficult to extinguish.

We then hung from ceiling rafters via a rope a large horseshoe electromagnet
out of a large W.W.II era magnetron.  The magnet was very heavy (about 30 lb..)
and had a throat clearance of about 2-3" between pole pieces, height was about
6-8".  When Alex attempted to pull an power arc, with the magnetic flux
passing horizontally across the power pole of the PT, as the arc was being
pulled upward, the arc sounded like a high frequency Bronx cheer (literally
:^) ), and could not be pulled longer then about 4-5" (maybe even 6" memory
is fuzzy).  It was being blown out (away) from the throat of the magnet as
fast as an arc would appear, and direction of blowout was completely
independent of AC utility wave instantaneous polarity (+/- didn't matter).

This was a dramatic demonstration of the magnetic blowout principle, in a
very cobbled up affair.  That why my comment of a C magnetic structure
with even ceramic magnets may provide enough field intensity to be beneficial
with quenching on the main HV electrodes of a RSG (AS or S)

Regards
Dave Sharpe, TCBOR
Chesterfield, VA. USA

Tesla list wrote:

> Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<evp-at-pacbell-dot-net>
>
> > > David Sharpe wrote:
> > >
> > > > Ed
> > > > Not doubting may have to go to NIB or SaCo to get
> > > > BH product high enough to do the job.  However if
> > > > I mount in a 'C' magnetic armature (1), and shape pole
> > > > faces to focus what magnetic flux we got (2), we may be
> > > > surprised at the available flux density.  The magnetron
> > > > ring magnets are cheap, compared to a rare earth, and
> > > > magnetic quenching was captured on a video tape at
> > > > Richards nearly 8 years ago, using a WWII Alnico
> > > > magnetic radar magnet.  These modern ferrite magnets
> > > > are at least 3X to 5X stronger then first (and second)
> > > > generation alnico products.  Worth giving it a whack
> > > > and see what falls out of it.
>
>         Not having access to that tape, and being too cheap to buy it, wonder
> if you could just give a word summary of what happened? Not sure what
> WWII magnetron magnet you used.  Typical flux density for the S-Band
> maggies was about 1000-1500 gauss across a gap of the order of 1-1/4",
> and for X-Band it was about 2500 gauss across a gap of the order of
> 5/8".  I don't have my magnetic properties handbook here at home, but
> think you're mistaken about the relative magnetizing power of the
> ferrite and alnico magnets.  If I can remember I'll take a look at that
> next week.  By the way, one of the permanent magnetic materials
> companies has some excellent reference data on magnets on its web page,
> but that is also bookmarked at work and not at home.  They most
> specifically compare the ferrites and more modern rare-earth magnets
> with the various alnico's and nickel-iron.
>
> > How about electromagnets? The time delay between initial current pulse
> > and magnetic activity would give an interesting twist to "tuning"?
> >  I think the diac\Triac pair would work, but then a real circuit?
> > I like it!
> >
> > Marc M.
>
>         Electromagnets were used for quenching during the entire era of ARC
> transmitters.  They were hooked in series with the arc and thus provided
> the stabilizing effect of series inductors.  The current in the magnet
> varied as the arc current varied, which may have provided some sort of
> current regulation, though don't remember seeing any discussion about
> that.  No doubt that electromagnets would work in Dave's application and
> have the advantage of adjustability, but it would take a lot of a magnet
> to equal what those little permanent magnets can do!
>
> Ed