Re: Inductive Kick LTR Pig Systems

["Bert Hickman" <bert.hickman-at-aquila-dot-com> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Tesla list wrote:
> 
> Original poster: "Area31 Research Facility" <rwstephens-at-hurontario-dot-net>
> 
> Terry, All,
> 
> Is it possible that the unusual heating of Marc's PFC cap was due to
dielectric
> losses as it tried to shunt RF kickback coming out through the mains wiring?
> His PFC cap might have had a mylar or perhaps even more lossy dielectric to
> RF.  From personal experience I know there can be enough nasty RF on the
> primary side of a pig system to smoke a large variac if bypassing
measures are
> not employed.
> 
> Robert W. Stephens
> Director
> AREA31 Research Facility
> <http://www.area31-dot-org>www.area31-dot-org
> >
> > ----- Original Message -----
> > From: <mailto:tesla-at-pupman-dot-com>Tesla list
> > To: <mailto:tesla-at-pupman-dot-com>tesla-at-pupman-dot-com
> > Sent: Sunday, August 27, 2000 14:48
> > Subject: Re: Inductive Kick LTR Pig Systems
> >
> > Original poster: Terry Fritz
> <<mailto:twftesla-at-uswest-dot-net>twftesla-at-uswest-dot-net>
> >
> > Hi Bart,
> >
> > <snippage>
> >
> > I would be surprised if this has not been known.  But stranger things have
> > happened in this hobby ;-)  The heating Marc saw on his caps is strange...
> > <more snippage>
> > Cheers,
> >
> > Terry
> >

All,

This topic did indeed come up several years ago, and there was agreement
that PFC's wouldn't hurt.. in fact they could offer several advantages.
Some thoughts:

1. PFC's offer similar advantages to inductively ballasted pigs as they
do with NST's - their use can significantly improve the power factor of
your setup, allowing for more efficient running at a given current
level. This is particularly true for systems sized with a smaller than
resonant tank cap. In this case, using PFC's should allow more "real"
power to go into sparks before popping the mains breaker. Oversizing the
PFC bank will simply help offset the effects of other inductive loads in
your house - induction motors, transformers, fluorescent lamps.

2. The only real disadvantage to using PFC's is that a significant
amount of non-polarized capacitance is required. However, that fact that
a pig-powred system will be running off 240 VAC helps to reduce the
amount of capacitance to reasonable levels versus 120 volt NST's (by a
factor of four). Unfortunately, PT-powered systems don't have this
advantage. Large PFC's are often found at very reasonable prices at
Hamfests or surplus stores.

3. As Rob suggest4ed, another significant benefit is that PFC's also
help to absorb transients/kickbacks/RF coming back into the LV side of
the pig. Large MOV's (3000 Joule) at your supply mains won't hurt
either... and they can help protect your electrical gear from
external switching or lightning-induced transients as well.

4. The voltage rating of the PFC's should be at least 440 - 660 VAC.
Based upon a number of transient voltage measuremements that were made
on pig-powered systems several years ago, 220 VAC caps may not be
adequate. 

5. Marc saw excessive heating because he employed motor starting
capacitors in his configuration... BUT, the true mystery is why more of
his PFC's didn't blow up sooner... :^)

-- Bert --
-- 
Bert Hickman
Stoneridge Engineering
Email:    bert.hickman-at-aquila-dot-com
Web Site: http://www.teslamania-dot-com