RE: Residual charge left on caps

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>

Hi Gary,

Mine were the Panasonic.  But, I think if you try this test tomorrow, the 
other caps might do it then.  And on Wednesday, it will be all different 
again...  It may be that the CD caps just were not having corona or some 
other chancy thing was going on to cause the effects you saw.

On test would be to pre charge the caps to:

0V, 1000V, 0V, -1000V...

Then run the coil.  Afterward, those voltages should still be there.  If 
they all have gone to zero, something odd is working to stabilize and 
discharge them.  Of course, if they are all sorts of odd numbers now, 
goodness only knows what is going on...  Corona, different losses at 
different voltages or frequencies,....

  Cheers,

         Terry

At 06:46 PM 1/19/2004, you wrote:
>I had a little time to do some experiments on this topic.
>
>I ran my mini coil with 4 Geek Group CD942C 0.1uF/2000V caps in series 
>with no bleeder resistors.  After running maybe 10 seconds, I unhooked one 
>end of the string, and using a DC multimeter and one of the passive 990Meg 
>HV probes, attempted to read the residual charge on each cap.  I saw nothing.
>
>I replaced the CD caps with a string of 4 BC Components 383-MMKP 
>0.1uF/1600V caps.  Ran the coil, tried to measure a residual charge and 
>saw none.  What the...  I KNOW I had seen residual charges enough to make 
>a good -snap- when I shorted them in the past...
>
>I replaced the 383-MMKP string with a string of 4 BC Components 376-MMKP 
>0.047uF/1600V caps.  These are the ones that I first used when I saw the 
>residual charges.  I retuned and ran the coil for a few seconds, 
>disconnected one end of the string, and sure enough, there was the charge, 
>plain as day!  I tried several iterations, and each time the charge on 
>each cap varied, I think the highest value I saw over 3 iterations was 
>about 610V.
>
>The two different BC caps have identical case sizes and were wired with 
>identical geometries.  Clearly some types of caps are more prone to this 
>effect than others.  For others who have seen the residual charges, which 
>type of caps were they?
>
>Gary Lau
>MA, USA