RE: EMMC Value Drift


I'm running the heck out the same Panasonic caps (the ECW series).  My setup
is slightly different in that I'm using two strings of ten .033uf for a
total C=6.6nf  

Initial measurements after construction were 6.6?nf (I didn't document the
accuracy any further at that point).  I re measured the assembly last night
and found they are 6.64nf (no degradation that I can see).  I then ran them
hard for 5-min straight and on and off for another 5-min. Measurements after
they returned to ambient temp. remained at 6.64nf  I'll continue to monitor
them as they log some more time (30+ min at this point).

Testing is on my Mini-Twin (bipolar coil), driven with a 12/30NST, and a
loaded frequency of approximately 500khz. These caps took a lot of abuse
while I was setting up this coil (including a primary strike). Last nights
settings are as follows:

1)135v input to NST
2)NST Safety gap set so it just doesn't fire at 135v
3)RQ widened until Safety gap just starts to fire
Hope this is of some value and keep up the great EMMC work
Brian D. Basura

-----Original Message-----
From: Tesla List [mailto:tesla-at-pupman-dot-com]
Sent: Wednesday, July 07, 1999 10:27 AM
To: tesla-at-pupman-dot-com
Subject: Re: EMMC Value Drift

Original Poster: Ed Phillips <evp-at-pacbell-dot-net> 

Tesla List wrote:
> Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>
> Hi All,
>         I seem to be noticing a very slight capacitance value drift in my
> cap.  It has 10 caps per string and has 5 strings of 1600 Volt 0.056uF
> Panasonic high voltage pulse caps.  The total value has gone from 27.9nF
> 27.7nF.  Each individual string seems to have drifted the same amount
> (-0.7%).  This is close to the limits of my LCR meter but the drift seems
> real.  After lasts week's run, it seemed to drop by about 0.3%.  I ran it
> very hard this 4th and it seems to have drifted another 0.4% with that
>  I run this 16000 volt cap at about 22000 volts so it is stressed in
> voltage.  The strings seem to be fine current wise.  I wonder if the dv/dt
> thing is degrading the internal connections??  Perhaps it will level out
> with more use but it seems to be continuing in a linear way with the
> of use.  If it continues, eventually it will fail and I can dissect the
> remaining caps to see what the cause is.
> Cheers,
>         Terry