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Re: Antonio Nobel candidate
-----Original Message-----
From: Tesla List <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Wednesday, May 12, 1999 2:05 AM
Subject: Antonio Nobel candidate
>Original Poster: "Robert W. Stephens" <rwstephens-at-headwaters-dot-com>
>
>Tesla List wrote:
>>
>> Original Poster: "Antonio Carlos M. de Queiroz" <acmq-at-compuland-dot-com.br>
>> The other discussion about static charges in the surface of the
>> secondary gave me another idea: These racing sparks can be charges
>> deposited in the surface of the secondary, moving due to the
>> coil varying electric field. A varnished secondary coil can store
>> significant charge at the surface, capturing charges from the
>> ionized cloud that surround an operating coil.
>> The small distance to the primary would result in charge spraying
>> over the secondary coil by corona, enhancing the effect.
>> The combination of a grounded conductive layer (the coil wire) and
>> a thin dielectric(the varnish) create a large grounded capacitance.
>> These accumulated charges can create areas of relatively conductive
>> material at the surface of the varnish, that serve as terminals and
>> charge supply for the racing sparks.
>> (A similar phenomenon is what makes MOS transistors conduct.
>> Charges at the surface of a charged vertical capacitor move when
>> excited by a lateral electric field.)
>> If this is true, coils that show racing sparks would also
>> retain significant charges after turned off. The idea of gluing
>> plastic rings spaced along the coil, or blocking corona from the
>> primary with well rounded surfaces and added insulation could then
>> be effective against "racing sparks". Another, more strange,
>> idea would be to make the surface of the varnish slightly
>> conductive to impede the slow accumulation of static charges.
>>
This is probably the same mechanism that makes the breakdown along an
insulator's surface significantly less than that in free space (why those
powerline insulators and "hockeypuck" HV rectifiers have ridges). It's also
related to the really long sparks you can get on an insulated surface over a
conductor or across the surface of a liquid. There is a discussion of this
in Bazelyan and Raizer, "Spark Discharge", pp256-260, but their analysis is
somewhat qualitative, and is also oriented towards single impulses. I don't
recall if it was in Naidu or in Khalifa, but one of them said that the
breakdown in a gap with an insulating column in the middle of the gap was
1/3 that of the same gap without the column.
The suggestion of semiconductive coatings is novel. I wonder though, if the
dynamic behavior might screw you up (the time constant of the R(coating) and
C(self) would be pretty long, so the charge would accumulate and the spark
would form before it had a chance to dissipate). The spark propagation
speeds are in the submicrosecond range.