Re: MMC Residual charge

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

Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com> 


Yes, it's caused by unequal charge distribution and sharp points off a wire
junction.  Throw some caps in a clear tank and charge them to HV and you can
actually see the moving oil.  It occurs in caps and power xmfrs as well.

Dr. Resonance

Resonance Research Corporation
E11870 Shadylane Rd.
Baraboo   WI   53913
 >
 > D.C. - by "circulating currents", are you really suggesting that there is
 > fluid-motion, some sort of convection, moving the oil about the internal
 > plates, or is there some other meaning?
 >
 > I don't think that this effect is due to dissimilar cap values or
 > dielectric leakage resistance.  As I mentioned, I was unable to get a
 > simulator to replicate a charge accumulation.  I feel an experiment coming
 > on...
 >
 > 1) Document the residual charge on each cap of my 4-element MMC on my 4kV
 > mini coil, without resistors
 > 2) See if residual charge is dependant on capacitor orientation
 > 3) See if there must be HF oscillations to leave residual charges, or if
 > just having HV 60Hz cycling is sufficient.
 > 4) See if the magnitude of residual charge is linear /wrt charge/discharge
 > voltage, or if it only occurs above some corona threshold.
 >
 > Round Tuits are hard to come by in a house with small children, so it may
 > take me a couple weeks.  Stay tuned.
 >
 > Gary Lau
 > MA, USA
 >
 >
 > Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>
 >
 > Hi D.C.,
 >
 > At 09:10 PM 1/13/2004, you wrote:
 >
 >  >Actually, Terry, you were correct.
 >
 > Oh Goody!! ;-))
 >
 >
 >  >Cooper told me they had incredible headaches with metallized type caps
in
 >  >air.  They would discharge one section and by doing this, it would
actually
 >  >charge up another section.  A lot of crazy things were happening in air.
 >
 > Yeeeeaaaap!!!
 >
 >
 >  >In oil, the circulating currents neutralize the cap potentials.  This is
one
 >  >reason why most all their HV caps are in oil.  Also, of course, the edge
of
 >  >foil tracking currents are much less.
 >
 > Fascinating!!  Oil can "flow around" and re-deposit charges as needed to
 > neutralize things...  So cool!!!!
 >
 >
 >  >He said there are 3 different reasons that can produce these strange
charges
 >  >in air:
 >  >
 >  >(1) Unequal cap values.  They match their caps at 0.5% or better.  More
 >  >specifically the dielectric leakage in individual caps is important.
It's
 >  >not good in metalized foil caps.
 >
 > MMCs always have that "self heeling thing" to fall back on...
 >
 >
 >  >(2) Dielectric polarization.  Even partial polarization produces
 >  >displacement currents and unequal charge distribution.
 >
 > Yeap!!
 >
 >
 >  >Most important factor (3) In oil, the small circulating currents
equalize
 >  >and discharge the caps.  This is due to the dielectric hysteresis
effects in
 >  >energy discharge caps.
 >  >
 >  >Bob said most of their HV filter caps contain internal discharge
resistors.
 >  >He said the high Q energy discharge caps do not because of the oil
currents
 >  >and hysteresis effects.
 >
 > So the oil acts just like discharge resistors to move the charges around
 > and neutralize things and make things safe...  Resistors are probably far
 > far faster and more predictable.   For an MMC cap, the added resistance is
 > expected and no problem.  "Real" cap maker's would have problems
explaining
 > the added resistance...
 >
 >
 >  >Safety first:  In conclusion, we should continue to use bleeder
resistors
 >  >across all metalized foils caps operated in air.  I always use pcs in
 >  >series, 4.7 megOhm each.  Each resistor has 1/2 watt rating.  Also, even
 >  >after discharging each section, Cooper warns, always handle them with
rubber
 >  >gloves if you are not using bleeder resistors!!!
 >
 > Sounds like all is coming into agreement with some exciting new info from
 > our "pro" buddies ;-))
 >
 > We have discussed MMCs "in oil" in the past.  Oil is so messy, we all "ran
 > away" from the idea.  But maybe it could eliminate the resistors...  But
 > the effect of oil on the cap's plastics and such is scary!!  Mineral oil
 > may just dissolve the cap's plastics over time...  Me, I just use the
 > resistors and am all happy ;-))))))
 >
 > Maybe the pro cap makers should just do Tesla coil caps where everything
is
 > so much simpler :o)))))))))))  Hey!!  We probably know our application
 > better than most of their other customers :o)))))))))))
 >
 > Many thank for you insights and the contributions from you pro pals
 > here!!!  To give something back...  Maybe they could add materials to
their
 > oil to help the resistance or equalization.  We have resistance and charge
 > transfer going on...  Self healing must be a big deal too, but
intellectual
 > property problems must abound too...
 >
 > Cheers,
 >
 >           Terry
 >
 >
 >
 >  >Dr. Resonance
 >  >
 >  >Resonance Research Corporation
 >  >E11870 Shadylane Rd.
 >  >Baraboo   WI   53913
 >  >----- Original Message -----
 >  >From: "Tesla list" <tesla-at-pupman-dot-com>
 >  >To: <tesla-at-pupman-dot-com>
 >  >Sent: Tuesday, January 13, 2004 6:04 PM
 >  >Subject: Re: Magnifier Primary Capacitors - EQUIDRIVE vs. STANDARD
 >  >
 >  >
 >  > > Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>
 >  > >
 >  > > Hi D.C.,
 >  > >
 >  > > It will be interesting to here what they say!  Unlike MMCs, these
caps
 >  >will
 >  > > be damaged if residual or unbalanced charges happen to cause a
breakdown
 >  >in
 >  > > a cell.  My guess is, the oil is so very slightly conductive.
 >  > >
 >  > > Of course, this would not be the 20th time I have been proven wrong
;-))
 >  > >
 >  > > Cheers,
 >  > >
 >  > >          Terry
 >  > >
 >  > >
 >  > > At 02:19 PM 1/13/2004, you wrote:
 >  > >
 >  > > >Terry has encountered this phenomonea with MMC caps which is quite
 >  >unusual
 >  > > >because Maxwell and PCI caps both use a series of small caps
connected in
 >  > > >series inside the box --- I know Beau Meskin, when I visited the PCI
 >  >factory
 >  > > >in Chicago, showed me the interior of a 0.1 uF 30 kV cap and it has
22
 >  > > >separate small caps all series connected.  This construction would
 >  >simulate
 >  > > >the series connected MMC technique that we are all presently using,
so
 >  >why
 >  > > >would there be any difference?  Unless, as Dave Sharpe noted, there
are
 >  >some
 >  > > >different effects going on with the equi-drive system.
 >  > > >
 >  > > >I plan on calling my friends Bob Cooper and Randy Hartsock who are
the
 >  > > >senior design engineers at Maxwell and pose this question to them.
 >  >Perhaps
 >  > > >we can get to the bottom of this mystery.
 >  > > >
 >  > > >Dr. Resonance
 >  > > >
 >  > > >Resonance Research Corporation
 >  > > >E11870 Shadylane Rd.
 >  > > >Baraboo   WI   53913
 >  > > > >
 >  > >
 >  > >
 >  > >
 >
 >
 >