Re: PFC questions

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

Original poster: "Malcolm Watts" <m.j.watts-at-massey.ac.nz> 

On 7 May 2004, at 8:20, Tesla list wrote:

 > Original poster: DRIEBEN-at-midsouth.rr-dot-com
 >
 > Hi Malcolm,
 >
 > Yes, I finally determined this from another member's previous post.
 > Thank you for the advice. BTW, I figured that just for running a
 > Jacob's ladder, I actually like it wired the "wrong" way. The climb-
 > ing arc self starts easier w/out as much input voltage. Also, it's
 > snappier and actually seems bushier as well. BTW, could I run some PFC
 > caps in the "right" place in addition to the current wrongly placed
 > caps w/out smoking something? ;^)))
 >
 > David

Hi Dave,
           Yes, but in order to do the job properly you would have to
size the cap to correct for the new power factor. In fact, it might
not be necessary at all with this resonant condition present and the
present arrangement might in fact be better for correcting PF under a
wide range of loading.

     BTW, that post and several others of mine which arrived that day
should have arrived several days earlier. They appeared to have
escaped the web so I re-sent them. I was not attempting to appear
wise after the fact.

Malcolm

 >
 > ----- Original Message -----
 > From: Tesla list <tesla-at-pupman-dot-com>
 > Date: Thursday, May 6, 2004 8:19 pm
 > Subject: Re: PFC questions
 >
 >  > Original poster: Malcolm Watts <m.j.watts-at-massey.ac.nz>
 >  >
 >  > Hi Dave,
 >  >          The PFC cap is not in the right place to do the job it's >
 >  supposed to be doing. It should be directly across the mains, not >
 >  coming after the welder. If the cap is positioned this way, the >
 >  resonant rise will disappear as the cap is now slugged by the >
 >  impedance of the mains supply. > > Malcolm > > On 3 May 2004, at
 >  8:17, Tesla list wrote: > > > Original poster:
 >  DRIEBEN-at-midsouth.rr-dot-com > > > > Hello coilers, > > > > I have some
 >  questions regarding using PFC caps w/ the primary > of a > > pole
 >  pig. I have a 14,400 volt, 15 kVA distribution transformer > that I >
 >  > am currently just driving a Jacob's ladder with. The ballasting is
 >  > > provided by the guts of a 225 amp Lincoln arc welder that has
 >  been > > submerged in SAE 30 non-detergent motor oil as well as (2)
 >  seriesed > > MOTs w/ their secondaries shorted. The MOTs are also
 >  submerged in > > motor oil. The rotory current selector switch of the
 >  arc welder is > > mounted where it's accessable so as to have some
 >  control over the > > current to the pig. Today, I had a little spare
 >  time so I > decided to > > measure the input to the LV terminals of
 >  the pig as well as the > output > of the HV bushings. Also, I have
 >  200 uFD of PFC cap in > parallel w/ the > > LV input lugs to the pig.
 >  I noticed that when I run the pig w/ PFC > > caps in place, the LV
 >  input and HV output of the pig increases. > Here > is a chart of the
 >  input/output measurements of the pig (the > voltage > regulation is
 >  provided by (2) seriesed 1156 style > 120/140 volt -at- 50 > > amp
 >  powerstats set up for 0 - 280 volts output) > > > > First with 200
 >  uFD PFC                    without PFC > > > > Vin     Vout
 >                     Vin      Vout > > > > 100     6400
 >               100      6570 > > 150     9550
 >     150      9760 > > 200    12,750                             200
 >   12,980 > > 240    15,400                             240     15,650
 >  > > 250    16,000                             250     16,350 > > 270
 >    17,650 (variac dial at 73)         270     17,840 > (variac dial >
 >  > 280    18,450 (variac dial at 76)                is maxed out > at
 >  100) > > 300    20,340 (variac dial at 82) > > > > The arc welder
 >  current selector switch is set at 175 amps, I > believe > (don't have
 >  the marked dial guage anymore) and is > paralleled with the > > two
 >  MOTs. MOTs are pretty beefy but don't know what kind of > microwave >
 >  oven that they come out of. Oh yeah, the HV output was > obviously
 >  mea- > > sured open circuit with no load. The voltage measurements
 >  were made > > with a standard Sperry DVM (low voltage) and the HV >
 >  measurements were > > made with a Radio Shack 10Mohm impedance DVM
 >  that is taken > through an > > ebay special 40 kV (28 kVAC) HV probe.
 >  BTW, the variac's maxed > output > (measured at the ballasted input
 >  to the LV lugs of the > pig) will reach > > nearly 320 volts with the
 >  200 uFD primary PFC. Without the PFC cap, > > this same voltage point
 >  only reaches 270 volts with the variac(s) > > maxed out. > > > > My
 >  question is how much PFC capacitance would I need for this > setup if
 >  > > I were going to use it to power a big Tesla coil? I suppose >
 >  it's no > > surprise that the voltage increases with the PFC caps in
 >  place as > > there is probably resonance rise involved. > > > >
 >  Another problem is that this setup will trip out a 60 amp > breaker
 >  in > > about 30 to 45 seconds if i run the Jacob's ladder. The 200
 >  uFD PFC > > seems to reduce the current draw a little but I figure
 >  that I would > > probably need more capacitance to optimally reduce
 >  the current > draw. > Would a further increase in PFC capacitance
 >  cause a > dangerous resonant > > rise in the voltage? I know the pig
 >  started humming loudly with the > > PFC caps in place when the input
 >  voltage starts to exceed 290 > volts. > > > I'm sorry for such a long
 >  post but I was just a little curious > about > these observations. >
 >  > > > Thanks, > > David Rieben > > > > > > > > >
 >
 >
 >