Re: Inductive Kick LTR Pig Systems

["Metlicka Marc" <mystuffs-at-orwell-dot-net> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Tesla list wrote:

> Original poster: Terry Fritz <twftesla-at-uswest-dot-net>
>
> Hi Marc,
>
>         The RMS current through those caps should be the same as any PFC
> application.  My first thought is the 680uF is a pretty large continuous AC
> cap value and perhaps it is a motor start or intermittent duty cap.

yes they were motor start caps, it never occurred to me that i was using them
in the wrong application? (hind sight again)

> I
> think you save these two caps in series for 340uF but that should not
> explain the heating.  It is also possible that there is some resonance
> going on between these large caps and the pt somehow.
>
> In the configuration that the two 680uFs were overheating, Could you tell
> us what the connections were (I assume in series across the AC line right
> before the PT.  Also if you could mention the PTs specs too.

the caps were paralleled across the line after the main contactor, before the
pt. the new caps are mallory 40-48uf, 220ac. these exhibited some warming but
that was after one old one that i used in other experiments blew, i think i
hurt it? i am getting some more caps to build a new matched bank. the Pfc. for
the 2kva  stepper trans. are the new Mallory's and they seemed to warm also but
not much and maybe my imagination?
the pt is a 110/33000, 300-1 unit. single terminal. i am running 120v into the
stepper and 70v out to the pt.
there are things on the pt label that make no sense to me but if you or anyone
would like to decipher it i'll post.
marc

>
>
> Cheers,
>
>         Terry
>
> At 10:30 AM 8/27/00 -0400, you wrote:
> >terry, all
> >i would like to say here that on my pt system i had been using two 625uf
> >caps rated 240v. these got hot rather quickly limiting me to short runs.
> >the recent improvement to banks of 1- 1000uf and 6- 48uf motor run caps
> >has lessened this substantially, although i blew one old 48uf in the run
> >they still got warm.
> >i would think that for a pig system that a large bank of caps would
> >distribute the stress out over a broader area?
> >of coarse until someone try's it on a pig i can't say for sure since
> >i've only as yet worked with the pt. the addition of a cap bank on the
> >step down trans.dropped my current draw from the mains from 30 amp down
> >to 19 amp. i know this because without them i had to adjust my breaker
> >to trip at 32 amp, with them i could get it down to 20 for 2-3 minute
> >runs and at 19 it would trip after about a minute.
> >don't know if this information helps any but i'm throwing it out there
> >just in case.
> >marc
> >