[Amps] Hi pot test - normal leakage current of vacuum cap

LB3HC rezycle.bin at gmail.com
Mon Oct 10 12:51:18 PDT 2011

Looks like mine behaves similar to your number 4. Several sources state that the clunks are OK to get rid of impurities as long as there is not too many clunks heard. Another cap of similar type, however with less vacuum chamber "volume", also clunked when hipot tested, but reads zero leakage current at full 16 kV. This leads me to believe that I have a bad cap. However, does it actually matter with a small current? It will not arc it looks like. If we assume the leakage current is non reactive, then 10KV*50uA will dissipate 0,5W. Hardly a problem. The RMS voltage will not be near 10KV when run on my GS35B design. OR: will there be problems down the road with a leaky vaccum cap?


On 10.10.2011 00:45, Dan Hearn wrote:
> OM: I have a commercial Hipot tester which can be varied from 0 to 9kv. I tested several vac variables I have and here are the leakage results.
> 1. 1000pf @ 5kv. 1ua at 5kv, 5ua @ 7.5kv.
> 2. 1000pf @ 3kv. 1/2 ua at 3kv, 4ua @ 4.5 kv.
> 3. 1000pf @ 3kv, 1/2 ua at 3kv, 6ua @ 5.5 kv.
> 4. 300pf   @ 15kv 3 ua at 3kv and current flickers. 25ua @ 4.5kv,  bad unit. 
> All are Jenning units. I see increasing leakage current a bit above the rated voltage on good caps. I would never increase the voltage until it arcs because
> I am concerned that an arc will damage the smooth surface. The increasing leakage current, I believe, will separate a bad cap from a good one.
> 73, Dan, N5AR
> On Sat, Oct 8, 2011 at 6:05 AM, LB3HC <rezycle.bin at gmail.com <mailto:rezycle.bin at gmail.com>> wrote:
>     Hi experts! I have hipot tested a 1000pF UR4LL vacuum capacitor today.
>     It did clunk a couple of times at approx 4 kV and then it settled
>     down. The it clunked a couple times at 8 kV and settled down. Now it
>     handles 14 KV without any internal arc overs. However... it draws
>     approx 50 uA leakage current @ 14KV. Is that normal or do I have a bad
>     vacuum (gassy cap) here?
>     73
>     LB3HC
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> -- 
> Dan Hearn
> N5AR

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