Re: chokes (fwd)
---------- Forwarded message ----------
Date: Sat, 23 May 98 16:38:38 EDT
From: Gary Lau 23-May-1998 1623 <lau-at-hdecad.ENET.dec-dot-com>
Subject: Re: chokes
>From: Mad Coiler <tesla_coiler-at-hotmail-dot-com>
>Subject: Re: chokes (fwd)
>>I would recommend dumping the chokes and using 300-500 pF bypass caps
>>with series resistors and safety gaps on each side of an NST.
>Assuming for the moment that I do as you suggest: I have a bag of 1nF
>6kV ceramic caps that I could series for use as bypass caps. What kinda
>resistor values we talking about? What V rating for the caps should I
>need? Are you grounding the center of the bypass cap network or just
>going from terminal to terminal on the NST's?
>Sorry so many questions but I am getting so many different responses
>regarding the use of chokes. I think experimentation is going to be the
>best way to figure what works better for my setup.
Experimentation is great when the success or failure can be easily
determined. Unfortunately with NST protection networks, success does not
result in measureable coil performance, but in a longer life of your NST.
It's hard to know you're doing the wrong thing until it's too late, and
may be highly dependant upon the history and condition of the NST you're
using :-( That's why there's such a lack of consensus on this.
Your ceramic caps should do fine for bypass caps, I'd recommend sets
of four in series, 24KVDC, with 1-2 sets of four (250-500 pF total) from
each of the NST HV terminals to your RF ground. Safety gaps (~.25")
should be in parallel with each bypass cap cluster. Then a BIG resistor,
like 500-1.5K, 50-100W from each NST terminal to the main gap. I don't
know why they dissipate so much power but they do, at least if your main
cap is well matched to the NST and is mains-resonant to draw maximum
Waltham, MA USA