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Re: Ceramic Tank Circuit Caps



At 12:05 AM 10/12/98 -0500, you wrote:
>Gwyn,
>
>Most coilers who use ceramic caps tend to use the more common doorknob
>type. Unfortunately these provide correspondingly poor results due to
>their relatively poor metal system, relatively high ferroelectric loss,
>and their changing capacitance versus temperature. The low-loss ceramic
>laser pulse caps you're employing should provide much better
>performance. These are quite nice if you can get them at the right
>price! However, these still will be significatnly lossier than PP or
>LDPE pulse cpas. I assume the oil is used to remove heat?
>
>-- Bert --
>
>

	There are two general types of "doorknob" high voltage ceramic caps.
Cheap lossy ones used in DC applications which will heat and fail in TC
applications.  Then there are the High-Q ones used in high power
transmitters and such.  The high Q variety will easily stand up to TC use
if the voltage rattings are meet properly.  The cost difference is very
dramatic, however.
	A Murata 5000pF water cooled has the following ratings:

HF peak		20000 v
Rated power		2500KVA
Rated current	250 Arms

About the size of a small coffee can.

Note that the KVA and current ratings are for continous use.  The picture
in the book looks like these devices were made to handle much more than a
TC could ever put out.  The lesser caps in the book, look like they could
easily meet Q and power requirements with some care.  The book is Murata
disk and high voltage catalog # C-20-A.

	Terry




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