Pig Ballast measurements
After putting my son to bed (tuesday nights I've got watch), I
measured at the primary ringing and secondary hash that I saw last
First I put a sola constant voltage harmonic regulated xformer between
my mains and scope. This reduced the "grounded input" signal to less
than 1 volt.
Setup: LV side: 220V 60Hz into to seriesed line filters. 23uF of 600V
cap ac cross the mains. Then 9mH and 5-10 ohms ballast in one side of
the line to the pig's 110V "primary. Then from pig center tap back to
the line filter.
HV side: 4' of HV wire from the pig's HV bushing to one side of my
rotary gap, then 2' over to my 0.006uF TC cap. Cap back to rotary to
gnd to case of pig. 6' of wire here. Note: there is no "intentional
inductor here", just 9 or 10 feet of HV wire.
Scope: TEK 465B 100Mhz, 10:1 probe.
HV divider: 20,000:2 or 2,000:2 Time and Frequency Technology PVK-01.
I scoped my primary first.
I saw hash with a period of ~~2us and very high peak voltages.
Well over 200 volts peak with the 2000:2 divider.
I saw a sawtooth wave form on top of the 60hZ mains of 100us
period (10Khz) with a 200-300 Volt peak amplitude. Assuming an
inductance ringing with the 23uF cap. L = 11uH. Assuming a 9mH
inductor: C = 28nF. Neither sound good. Assume a 60uH leakage
inductance for the pig primary: C = 4.2uF. Maybe. Any other thoughts?
I also saw a longer period sine way after the last gap firing
for each half cycle. 2mS - 3mS period (500Hz - 333Hz) bingo, that's my
Ballast L and C! 9mH & 23uF => 350Hz. It had a 600-800 V pp level and
about 3/4 of a cycle before it dampened out.
Back up to the sawtooth, maybe it's just a straight line portion of
the 350Hz sine wave. The overall voltage is enough to trigger the
spark gap before I can see the sine wave visually.
note: All of these effects were superimposed upon the 220V mains sine
Then I scoped my secondary.
Grounded input level: less than 1 volt.
I hooked my scope probe to an 18" test lead hung 9' away from my
system and measured the RF hash. 0.2us period (5MHz) and 175-200++ V
peak! That's right between 3 and 4 divisions at 50V per division.
I connected my scope probe to my HV divider. The RF hash measured
200+V and a 10K divide ratio. Grounding the scope input switch: 30V.
The RF has a period of 0.5uS (2Mhz). I had to move things around to
connect up the divider, this may have caused the period change.
I changed scales to look at the "60Hz" output voltage. about 28kV with
occasional 75kV peaks! Yes I check this 3 times. No wonder I'm
seeing/hearing such a difference between resistive and inductive
Given the pig secondary, cap, and rotary were all in parallel, I was
getting bad quenching on my rotary gap. Most of the time I had 2" - 3"
power arcs, but occasionally I would light up the entire circumference
of my 8" rotary gap! That was quite a sight (and sound).
again note: all of these were superimposed on the 220V mains sine
Input current was under 10A. into the pig primary.
I've answered my basic question about the effect of inductive ballast
in the primary circuit: each time the spark gap quenches, the
inductive ballast does kick the voltage going into the pig primary.
(by 600 to 800 volts!)
I think that the RF hash that I am seeing is the effect of the
negative resistance of the spark gap ringing the 6nF cap and (169nF)
of inductance in my HV circuit. Remember Hertz's first transmitter: HV
source, circular loop terminating in a spark gap?
Thoughts? comments? Would anyone like to scope their pig primary?
------------- old message ---------------
> I started with just the basic pig circuit: Line filter with 25uF cap
> across it (prevents blowing common mode choke) 9mH inductor 13.5 ohm
> series resistor 110V pig winding. 220V in 60Hz (16.7ms).
> I'm saturating the pig. Secondary output: square wave, 3.6ms pulse
> width and an 8ms period - bipolar. 20kV peak voltage. It's actually a
> damn fine square wave with only a little ripple (4 or 5 kV) on each
> peak. Primary mains current was much less than 10A. (minimum mark on
> my current shunt: meter)
> Switched the ballast resistor in parallel with the 9mH choke. Mains
> current went to 20A. Secondary output to 19kV, rounded square wave of
> 4.2ms width, 8ms period.
> I switched to the 220V tap on the pig "reverse primary". 10kV sine
> wave out, with or without ballast. Magnetization current: 1.8A
> Now artifacts started appearing! RF hash to 400kV!!!!????? 40 Volts on
> scope with a 220Meg into 22K RF divider. I want to believe this is
> just an artifact of a bad ground loop. Scope Mains plug grounded to
> house ground. Probe ground to pig case (single ended pig) to my 4'
> ground rod. My house ground (Cu water pipe) and TC ground are about 3'
> away from each other and 0.75V away. (Cu and Al electronegativity) I
> didn't try to measure the real secondary voltage here, I was a just
> barely visible square wave. 10kV?? 12?? 15?? Also 3" power arcs on the
> rotary electrodes.
> I added my 6nF 0.120" polyethylene cap across the spark gap. The power
> arcs stopped. 1/2" arcs so loud I had to put on "shooting phones"
> hearing protectors. Blast! I forgot to look at the primary current!
> What I saw was a 10kV peak sine wave with a 10kV or so sine wave
> superimposed on it. This superimposed wave had a variable period,
> based on the "speed" of my rotary gap. I saw between 3 and 6 or 8
> cycles on top of each 1/4 wave peak of the 60Hz "mains" voltage.