Original poster: "colin heath" <colin.heath4@xxxxxxxxxxxxx>
Hi All,
I realise I am vastly simplifying this discussion but
here it is. I used a simple LCR meter to check my ballast
Inductance on spark gap coils running static, async and sync gaps
and although the meter does not have enough power to magnetize core
correctly and many other probs I don't understand! It has always
yielded close results with regards to what current the coil should
have pulled with that inductance. I also used the meter to read
values when setting up for the correct primary charging circuit frequency.
So why this system worked I don't know, however it did and continues
to. I must state I always used air gapped E-I cores (mot cores and others)
Cheers
Colin
----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Saturday, January 21, 2006 1:23 PM
Subject: Re: Ballasting a Pole Pig (Revisited)
Original poster: "Gerry Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
Hi Steve,
I think Dr R said that he measured the inductance with a LC meter
and that is probably the source of the high inductance. His
physical parameters show an inductance more in the range that one
would expect for the job. My program shows 20 amps with 240 volts
applied across the ballast (PIG and TC removed from the
equation). The slope of the ballast VI curve is very shallow when
excited at the low levels of a meter and I can believe the
erroneously high measurements.
You are right about the RSG affecting the current draw, especially
with a SRSG. The inductive kick of the ballast can allow for
higher voltages on the Cp (LTR) then what is obtainable with
steadystate draw when firing after peak.
I also believe taking taking the XC into account when determining
the ballast XL will get you closer to the real answer. My spice
has shown that one can draw upto maybe 2X+ what the ballast is
suppose to limit at not considering the XC. Taking just the XC and
XL into account should give you the steady state current with no SG.
Gerry R
Original poster: Steve Conner <steve@xxxxxxxxxxxx>
I don't think it's as simple as "Reflected Xc" vs "No reflected
Xc". Anyone who has played with a sync rotary knows that the line
current, power factor, and spark output can be varied over a huge
range by altering the gap phasing, so it's obvious that whatever
method you use to size the ballast must take the spark gap
behaviour into account, not just the primary capacitor.
If you want to accurately predict how much power/current a given
coil will draw through a given ballast, you need to work through
pages of differential equations that include the discontinuities
at spark gap firing times, or just simulate the whole coil system
using PSpice. Richie Burnett shows how to do that on his site.
With an async rotary running at high break rate, it may be
somewhat easier, and you could probably take half the line voltage
divided by the ballast impedance as a reasonable assumption for the current.
FWIW, I don't believe the 120mH figure either :-P I'd guess that
Dr. R's ballast is saturating. As a rule of thumb, if a ballast
has fewer turns than a transformer of the same core area and a
winding voltage equal to the line voltage you are running off, it
is liable to saturate. (but not guaranteed to)
Steve Conner
http://www.scopeboy.com/
Tesla list <tesla@xxxxxxxxxx> wrote:
Original poster: "Jim Mora"
Gerry,
Thanks for figuring out the "reflected XC" issue. Do others concur with this
reasoning? Must this XC on the transformer output always be taken into
account when adding an inductive ballast in the primary of a disruptive
coil? I was baffled by the XL=120mh and 30 amps as well.