Re: EMMC Value Drift

To: tesla-at-pupman-dot-com
Subject: Re: EMMC Value Drift
From: Ed Phillips <evp-at-pacbell-dot-net> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
Date: Wed, 07 Jul 1999 11:27:22 -0600
Approved: twftesla-at-uswest-dot-net
Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

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
EMMC
> 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 to
> 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 use.
>  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 amount
> of use.  If it continues, eventually it will fail and I can dissect the
> remaining caps to see what the cause is.
> 
> Cheers,
> 
>         Terry

	Are those metallized plate capacitors?  If so, there may be some loss
in area due to deterioration of the metallization.

Ed