Re: Magnequench RSG II - Corrections

["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, All
Several corrections from previous posting:
1.  Actually magnet used was a permanent Alnico magnet
     not electromagnet as erroneously posted.  It was from
     a very large magnetron, maybe post W.W.II.
2.  Wrote before thought...  :^P
     Direction of magnetic blow out of arc is dependent on
     right hand motor rule, and instantaneous direction of
     current in arc.
Sorry for confusion...
Regards
Dave Sharpe, TCBOR
Chesterfield, VA. USA

David Sharpe wrote:

> 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