[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Pole Pig.
Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>
Tesla list wrote:
Original poster: "Chip Ford" <chipford@xxxxxxxxxxxx>
Now, can we talk about the ballast for a minute. The function of
this and how to wire it in is a little fuzzy. I am thinking it will
be wired in series with the with the primary curcuit. I have spent
most of my "Tesla Time" working with NST. I have never used a
"Ballast" with one. I am trying to understand what is going on with
it. What I am getting so far is that this "Load" somehow keeps from
over-volting things. I don't know how to figure what to use? I know
where to get several different sizes of "Larger transformers"
reasonabley priced, I just don't know what to look for yet nor what
it's function is in a TC. I know that in an old automotive breaker
point system, the ballast was a resistor used to keep from
over-heating/over-volting the coil. I think that the "Ballast" in a
fluoresent light is a Step-up transformer used to make the plasma in
the bulb. I know that "Ballast" can also be wieght added to a ship
or a race car for example. I'm sure someone out there will
straighten me out on this stuff.
The addition of a ballast to our coils is the art of limiting
current. The ballast can be resistive, inductive, capacitive, or a
combination of these. The ballast can be hooked inline with the
transformers LV winding or even be installed on the HV side. As
mentioned, a resistor (big for a pig) can be used, but the voltage
drop across the resistor is a linear function of the current through
the resistor and the heat created by this current is a big loss.
Inductive or capacitive ballasting is preferred and usually inductive
ballasting is the choice because there are devices that work great
for this purpose. The most common inductive ballasting is the use of
a Welder, a large variac, and even homebrew inductors. The Welder is
usually the best choice (as opposed to a variac) because you'll get
smoother operation and better control over the entire range of
current, where a variac is a little erratic (both will work, but the
variac will see more damage over time to the brushes, especially at
As far as why a pig needs a ballast in the first place: Well, pigs
can draw massive currents under short circuit conditions.
Distribution transformers will have a percent impedance value. This
value will determine how much current could be drawn from your mains
during a short circuit event. My pig indicates a value of 1.9%
impedance, so 1/1.9% = capable of drawing 53 times it's rated current
or 2200A during a short circuit. That kind of draw would likely take
out your house electrical panel, cause a fire, or even do the same to
other houses in your area. Yes, a coil could run without the ballast,
but it's a "very" bad idea. Limit the current and protect everything
before the transformer and be sure to install a dedicated breaker for
the line to the pig.