Re: Capacitor test results
>From Esondrmn-at-aol-dot-comThu Jun 6 21:56:17 1996
>Date: Thu, 6 Jun 1996 11:23:51 -0400
>Subject: Capacitor test results
>Well, I finally got my capacitor back from Condenser Products yesterday.
>Last night I set up a bench test using a 120 volt 10 amp variac, 12kv 30 ma
>neon transformer, my high voltage filter board, the capacitor and a
>cylindrical spark gap. The high voltage mains from the filter board were
>connected directly to the capacitor. One half of the cylindrical gap was
>connected directly across the capacitor (three .030 gaps).
>The gaps would not fire. I noticed a slight buzzing from my filter caps
>(which has probably always been there but masked by the noise from the gaps
>firing and the coil running). I disconnected the filter caps and tried it
>again, still the gaps would not fire.
>Next I shorted one gap so there was only two .030 gaps in series. It still
>would not fire.
>Then I removed the filter board entirely. Now the transformer was connected
>directly to the capacitor. It still would not fire.
>Then I removed one more gap and now had only one .030 gap across the
>capacitor. I did finally fire now but sounded weak. Definitely not the hot
>staccato machine gun like noise that I remember from a couple of months ago
>when all this started.
>I tested the transformer several times during all of this and it seemed fine.
> I produces a hot arc about one to one and a half inches long.
>Anybody have any ideas? I know C.P. just tested this cap and pronunced it
>good, but it sure doesn't look good to me.
In your test lashup as described you are attempting to test charge a
0.025? mfd capacitor which has a 60 Hz reactive impedance of 106K
ohms. At 12 KV you will need 113 milliamps to swing this capacitor
to the full voltage of the transformer. Your transformer in this
case can only source 30 milliamps, thus it cannot charge the cap in a
60 Hz cycle to full voltage, and that is why your gap only starts to
fire when you really close it down small. You are probably only
getting a couple of thousand volts charge.
As a rule of thumb, when using neons, I like to size the neon at
least 30% higher in current sourcing ability than the reactance of
the RF capacitor demands. This ensures more firings of the gap per
cycle and better overall streamer activity.
Unless you can come up with 120 milliamps worth of neon power for
this test, you may have to go back onto your pole pig.
Good luck, rwstephens