Can someone recommend best-practices for potting a passive DC high voltage (<20 kV) circuit? I'd like to eliminate a micro-discharge problem we are seeing.
Details of our use-case follow:
I have a a DC high voltage system (<20 kV) which passes though a low pass (RC) filter to eliminate ripple and other noise before passing into a vacuum chamber. I can monitor the AC component to see its effectiveness
I can get good results from the filtering component; however we potted our most recent build and are seeing micro-discharges: these appear as 1V+ dips in the output voltage. The number of these per unit time increase substantially above about 15 kV, until at 20 kV they appear every 20 ms or so.
I am wondering if there is any surface-prep we can do to the resistor/capacitor leads and or if someone can recommend a specific potting compound that would work better.
We did a thorough mix and vacuum degas the compound before pouring it into the enclosure. I didn't use a primer however. We used Krayden DC170 compound for the potting
Best Answer
Increase the diameter of the conductors. This will decrease the electric field strength at the surface. It sounds like you only need to halve the field strength, so only need to double the radius of curvature.
Where you use connecting, use thicker wire. Where that wire is a component lead, then you could wrap some wire or foil around it, or slip a metal tube over it. If you have soldered joints, make sure you have not left any sharp edges or points where you've cut wires. Use some extra solder and let it ball up under its own surface tension.