Re: Warming up

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

Original poster: "BunnyKiller by way of Terry Fritz <twftesla-at-uswest-dot-net>" <bigfoo39-at-telocity-dot-com>

Tesla list wrote:

> Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<Leik3-at-aol-dot-com>
>
> Hi all,
> I had a quick question about warming up caps: Is this warming up, just an
> initial process (do you only have to do it the first time) or do you have to
> "warm into" them every use?? Do you ahve to only break in homemade caps or
> will I have to break in the caps that Terry is sending me too??

snipperzzz..

Hi Dennis ...

MMC caps are made to go into usage with out a "break in " period ...  altho
home
mades are a differrent story.

99.99999% of the time home made caps have air between the dielectric and plates
and if you were to apply a full load to them without any "prepping" they
blow up
99.99999% of the time.

Prepping a home made cap for usage can consist of hooking a voltage supply
( a NST
would be great) to a variac and slowly raising the voltage to about 1/4 of the
variac dial and let it sit for a couple of hours. ( the "pulsing" of the plates
and dielectric works out a good portion of the air) You then again apply
about 1/2
the variac voltage to the NST  ( which is connected directly to the cap  no
gaps)
for about 15 - 30 min. And finally you can apply about 80 - 90% of the variac
voltage to the NST for about a minute or 2 with a 10 minute cool off period (
power off)  several times. This "should" get rid of most of the air in the home
made cap.  ( best bet is to make a MMC  save yourself the heart ache and lost
money on home mades ) !!


As far as the "warming up" of a cap this is a term used to describe the
capacitors
physical behavior. when a coil is started "cold"  ( ambient temperature)
the value
of the cap may not be 100% accurate of the original rating ( lets say it
was rated
for .04uF ) the actuall rating may be +/- 5%. As the cap is energized by
the coil,
the resulting heat in the cap begins to increase.  This increase changes the
capacitors value a bit which in turn changes the frequency of the primary
coil set
( thus a need to retune the primary) the only way i know of that one could keep
the temp from changing is by placing it into a nitrogen bath ( BUT this
would be
bad ).


Scot D