Re: caps

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

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

DC Filter duty puts mechanical and electrical stress on the capacitor "all
the time", compared with the usual rated pulse duty, where the capacitor is
discharged most of the time, slowly charged to max voltage, then rapidly
discharged.  If you look at the "average (over time)" mechanical and
electrical stress on the capacitor, pulse duty is much lower than DC filter
duty.

There are also oscillatory stress issues (why voltage reversal is bad for
life) and thermal dissipation issues (why AC is worse than DC).

As one of the Maxwell data sheets or articles points out: capacitor life
and reliability is a very complex subject.  Their standard technique is to
build a sample capacitor (or similar section using well known (to them)
scaling laws ) and test it under conditions identical to the expected
application.  This is why you won't find many "tesla coil usage" ratings,
but you will find things like "1pps, 20%VR", or "1000pps, 80%VR", or "25
Amps RMS, 25kA peak", and so forth.

Tesla list wrote:
> 
> Original poster: "Ray Haynes by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<ray.haynes-at-home-dot-com>
> 
> Just curious, why would this be?
> 
> <SNIP>
> 
> >You will notice that Maxwell Labs warns against using their pulse
> >capacitors
> >as intended use DC filter caps evn though they might seem rough and
> tough
> >enough for the "ligher" job.
> 
> >KEN