Re: PFC questions

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

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


----- 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
 > >
 > >
 > >
 >
 >
 >