Re: GECKOS 201

--- In CAD_CAM_EDM_DRO@y..., "Carol & Jerry Jankura"
<jerry.jankura@s...> wrote:

> One other thing about 'higher ripple' - taken to an extreme (ie too

high a

> value of ripple) it can cause premature capacitor failure.
>
> -- Jerry
>

To be precise (and we ARE a group of precision loving guys)the ripple
does not cause the failure. In electroyltics the failure would be
caused by heat generated by IR losses from the value of capacitive
reactance plus the losses in effective series resistance (ESR) at the
specific frequency of the waveform (120HZ in this case). Capacitors
are very much frequency dependent devices. The smaller the value of
the cap the less it will filter if one side is grounded conversly it
will have less losses. If you put a .01MFD cap across a 120HZ
recitifed voltage it will not even get tepid. Large value filter
caps on the output of a rectifier see huge amounts of ripple current
for the first few cycles. Depending on the load the DC level builds
up and the ripple drops to a level that is defined by the
time constant of the current waveform the value of the cap and the
load current.

What all this means is that lower values of caps as filters do not
present a failure issue for themselves. Other filter caps downstream
should not fail because of ripple unless their ESR is high enough to
cause heating. Noise and bypass caps are effected little. Small
caps (Tantalum) of large MFD values when presented with high (25% or
more) ripple will start to overheat and eventually fail.

Overvoltage is a much worse killer of electrolytics than ripple.