[Prev][Next][Index][Thread]
RE: Dialectrics in Plate Capacitors
First and foremost, I will say this: There are no absolutes!
After all, we "know" we have to go to 3xDC rating for building caps.
But then Terry comes along and actually runs over the DC rating for some
time, in his EMMC :)
That being said:
>
> 60 mil is not adequate for 15 kV Erms which will hit well over 20
> kV peaks.
It can be. Depends on how it is constructed. While I personally now
use 90 mil as 3 30mil units in series, I know of some that are running
at less just fine. But a 90 mil single unit *will* fail. It's just too
much potential to prevent corona even under oil.
My rule of thumb is to aim for <5KV RMS potential for each unit in a
capacitor.
> Recommend at least 90 mil. Professional manufacturers use .002
> mil and then
I'll assume you mean 2 mil? or even .2 mil? I doubt you mean 2 microinch.
Myself, i use 5 ply 6mil.
>
> 1 inch will not provide enough creepage path across the plastic to avoid
> tracking especially at RF frequencies. Go at least 2 inches.
I am living proof that this is not an absolute. Flat plate capacitors.
1 inch (or less) around the foil. Been running fine at various power levels
for quite some time. I have *NEVER* had a capacitor failure due to creepage
or blow through. Have had one fail because a helpful student dropped it :/
Again, many units in series is the solution. My caps are used 3 in series
for 15KV.
Michael Baumann
Coiler, Homebrewer, Nerd...mycroft-at-access1-dot-net
http://www.access1-dot-net/mycroft