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Re: magnetic quenched triggered gap



Original poster: "Malcolm Watts" <m.j.watts@xxxxxxxxxxxx>

Hi Ed, all,

On 5 Jun 2005, at 22:47, Tesla list wrote:

> Original poster: Ed Phillips <evp@xxxxxxxxxxx>
>
> "Scot, all,
>
> Yes, I have two 1.5" thk. x 4" dia. hockey puck sized N-48 neodymium
> magnets that got stuck together and are now ONE 3" thk. x 4" dia. mag-
> net!  Once they became "one" big magnet, I simply tightened a 4" hose
> clamp around the seam where their surfaces meet, because I'm certainly
> not going to be pulling these apart! As a matter of fact, these
> magnets are DANGEROUSLY strong and can severely pinch any body parts
> that happen to get caught between them (ask me how I know this) =^0
> They can also chip off pieces of flying neodymium/iron shrapnel if two
> of these magnets are allowed to fly into each other unimpeded. It's
> not likely that the AC electromagnetic fields are going to
> significantly affect one of these types of rare earth magnets. The
> only thing you really have to watch for with neodymium magnets is
> heat. If they get much over 200*F, they start losing magentism and
> neodymium magnets have one of the lowest Curie temperatures of
> permanent magnets. It seems to me that bringing the magnets close
> enough to the spark gap contacts to ef- fectively quench the plasma
> flux of the spark gap, while maintaining ade- quate thermal and
> electrical isolation from the SG contacts w/out the be- nefit of any
> cooling aids would prove to be a real design challenge. IMHO, at least
> with higher powered systems, its more practical to just utilize a
> rotary spark gap, with a possible seriesed forced air cooled
> stationary gap to further commutate the heat of the spark.
>
> David"
>
>  David's advice about the temperature is important to note; these
>  things
> don't like to get very hot.  Solution to this problem is to embed them
> in a suitable magnetic circuit (plain old cold-rolled steel would be
> fine) with suitable pole pieces where the spark is to occur; the field
> would be oriented perpendicular to the direction of the spark.  The
> question of interest would be is does the magnetic field do anything
> useful.  I've thought of making such a device but would rather see the
> results of someone else's measurements and experiments first.
>
>  As an aside, I doubt that the hose clamp is really necessary.  Those
> things are now together for all eternity unless someone goes through
> some real heroics!
>
> Ed

Has anyone who has used a lump of iron or other ferro-magnetic
material to extend the poles of a rare-earth magnet looked at the
effects of saturation on the iron and hence effectiveness of the
strategy? Saturation is mentioned all the time with regard to
transformer and choke cores but little if anything has been said
about material effectiveness with a powerful static magnetic field.

Malcolm