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In Reply to: sharing resistor sizing... posted by Vinnie on May 2, 2007 at 16:59:03:
Decided to take a look at the old set of national radio institute home study (circa 1940)books my wife found for me at a flea market. Been meaning to "take the course" but just haven't had the time. Anyway..... these dudes are all about practical application and here is what they say about about dividing resistors for caps in seriesfor paper dielectric caps of high ohmeric value such as 10 meg
electrolytic caps have a much higher leakage current so low ohmeric values (10k to 50k) should be used
I am going try the 10 meg resistors on my .47uf mpp caps tonight so I will let you know how it works. This is the first thing I have found in any of my references about this.
Follow Ups:
> electrolytic caps have a much higher leakage current so low ohmeric values (10k to 50k) should be usedThose values can't be applied as absolute numbers; the designer must consider the voltage, number of capacitors and excess current the resistors will draw. It's an exaggeration I know, but what if you had a 10,000 volt supply with only two caps? A pair of 50K resistors would consume a huge amount of power unnecessarily (and probably go up in smoke). There's no need to agonize about this. Anything from 120K (which is what I used in my HV supply) to 220K should work fine. The primary function is to equalize the voltage across the caps. If the caps have sufficient safety margin in terms of their voltage rating, none of this is critical.
I
by trial and error it looks like 400k across .47 caps in series works, or at least allow voltage to flow. There just has to be some logic to all this and a simple formula for calcultating the values of the resistors..
Well, that didn't work either. No matter what resistors I try I can't seem to get voltage past the end cap. Must be doing something wrong but I don't know what it is. Any ideas folks? I'm high centered at the moment.
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