speaking of mmc's .Re: mini coil

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "david baehr" <dfb25@xxxxxxxxxxx>


.........where is a good source for caps for a MMC cap ?

>From: "Tesla list" <tesla@xxxxxxxxxx>
>To: tesla@xxxxxxxxxx
>Subject: Re: mini coil
>Date: Thu, 30 Dec 2004 11:02:40 -0700
>
>Original poster: Finn Hammer <f-h@xxxx>
>
>My thinking on this subject:
>
>Plastic is heated by RF, when it is subjected to an electrical
>field, not to a magnetic field. This means when it is used as a
>dielectric to separate potentials, not just because it is sitting
>inside a coil.
>
>Look at the secondary former: The electrical field is lengthwise on
>the coil, means, one end grounded, the other alternating at extreme
>potential. So: what we really ought to worry about is a short coil,
>since it will be stressed more than a long one, potentials equal.
>However, the field strength is orders of magnitude lower than the
>breakdown field strength, measured along the length of the coil.
>Radially outwards, from coil center to surroundings, the field is
>even, so there is no dielectric action in that direction.
>A couple of numbers:
>Dielectric strength of PVC: ~300V/mill -> 300.000 V/Inch -> a 20
>inch slab of PVC is good for 6MV, but a 20 inch long tesla coil
>probably only produces about 300-400kV.
>I think this is the reason we get away with using PVC as a secondary
>former in the first place: no particular dielectric stress at all,
>as opposed to in a capacitor, where PVC would fail miserably, along
>with polyester (mylar) another famous insulator.
>Well, due to MMC`s, thanks all!, we don`t have to worry about that
>anymore.
>
>I wish you all a happy new year, and DC a continuing recovery.
>
>Cheers, Finn Hammer
>
>Tesla list wrote:
>
>>Original poster: "claudio masetto" <claudmas@xxxxxxxxxxxxxxx>
>>
>>I am thinking of making a mini coil with a secondary of 2.375" x
>>12" pvc pipe. It has a fairly thick wall of about 3/16". Would it
>>make much of a difference in performance if I use a thinner wall
>>pvc pipe.
>>
>>Thanks
>>Claude.
>>
>>
>>
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