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magnetic gaps

Original poster: "Mr Gregory Peters by way of Terry Fritz <twftesla-at-qwest-dot-net>" <s371034-at-student.uq.edu.au>

Dave, list,

Magnetically quenched gaps have successfully been used by Richard Hull
and the TCBOR for quenching magnifier systems up to 7kW when in series
with an async rotary. The theory is that a strong magnetic field is used
to pull ions away from the spark gap, rather than the usual air blast,
etc. Below is an email conversation I had with Richard recently:

> Richard,
> For a large coil system I am building (currently 7-8kW, later who
> knows?), I wish to use a static gap in series with my rotary (100-
> 400BPS, synchronous). However, I don't really have enough power
> available to run an air compressor or vacuum gap (I need as much energy
> as possible for the supply xformer). I was reading in your CSN guide
> about magnetically quenched gaps. This may be a viable option. Could
> you provide any suggestions on how to construct such a gap?

You will have to obtain some magnets that can survive heat (alnico) and
place them in an armature to concentrate the field in a narrow gap. This
gap with intense flux (>3000 gauss is then placed perpendicular to a
single static gap's air gap. Such a gap should be used in series with a
conventional rotary in a large system. RH

>I have noticed that no one seems to use static gaps with sync rotaries.
Do you
> know why? Are they really needed with sync gaps? I was thinking that
> maybe the high BPSs used with async gaps short the transformer more,
> and therefore quenching is more critical to prevent power arcing. Most
> modern sync gaps seem to run at 120 - 240 BPS.

The reasoning behind why others do not use series gaps with rotaries
eludes me. They should. They improve quench. RH  

Greg Peters
Department of Earth Sciences,
University of Queensland, Australia
Phone: 0402 841 677