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Re: Oil-immersed RFCs
From: Owen Lawrence[SMTP:owen-at-iosphere-dot-net]
Sent: Tuesday, September 02, 1997 9:21 PM
To: Tesla List
Subject: Re: Oil-immersed RFCs
> From: Thomas McGahee[SMTP:tom_mcgahee-at-sigmais-dot-com]
> Sent: Monday, September 01, 1997 5:02 PM
> To: Tesla List
> Subject: Re: Oil-immersed RFCs
(snip)
> You are correct. The reason for many sets of windings is MORE to
> insure adequate breakdown voltage protection than to gain
> inductance... although you obviously get BOTH. If you increase the
> width of each section you increase the number of turns and thus the
> inductance of each section, but the voltage rating of that section
> will then DECREASE.
Here's a quote from the Radio Amateur's Handbook:
"Many of the popular sizes of RF chokes consist of a number of small,
flat sections of wire, called pies, separated about an eighth of an inch on
a ceramic form. The wire itself is wound in a honey-comb pattern, so that
the turns are slightly separated. The purpose of both spacings is to
minimize the capacitance action between adjacent wires and groups of wires.
This must be taken into consideration because it has the unwanted effect
of turning the choke into a resonant circuit all by itself or of nullifying
its choking action by providing a low-impedance path of its own to the very
RF currents the choke is supposed to block off."
No doubt this was meant to apply to lower voltages, but it still suggests
that there are other reasons chokes have the geometry that they do. I'm
just mentioning this (out of my own ignorance) because this is the first
time that I ever heard that having many sets of windings is for increasing
breakdown voltage protection. Comments?
- Owen -