Hi John,
Your right. The inductive ballast on PIGs and PTs do change the LTR/STR
scenario. I however always look at this as based on the transformer
alone.
But your right, the ballast changes that scenario. Even though JAVATC
states
that LTR is intended for internally ballasted transformers such as NST's,
I
still personally look at LTR as a general transformer situation (which I
probably should not). You've done well to point out the issues. This
isn't
the first time! We've been down this road in the past as you know. I
agree
with all you've said in this post and in the other posts that I missed
out
on replying (had to take wife to hospital the last couple days, so TCML
was
just not possible).
Anyway, great postings on this subject. I could not agree more. But I
will
say that all of us (you included) really don't know if PIG's are truly
running LTR, STR, near or at resonance. I've always assumed STR given my
personal situation and how I likely relate to the coiling world. The fact
is, we might be running STR. When you hit that STR value near 1.4, your
basically riding the edge of resonance, but just enough to allow a little
voltage calming. Were all likely hitting that area. I honestly doubt LTR
in
pig (just a hunch). Not just from a massive cap size scenario or even the
ballast inductive affect on what is or is not LTR, but the fact that when
you run a coil in slight resonant charge mode (always near resonance in
either direction), there are always some good sparks to be realized if
there is sufficient "power" regardless.
I run STR on a small coil and get great spark lengths, but I have the
power
in the transformer to make it happen. This would not have been possible
if
the coil was not running near resonance at a 1.4 ratio. Well, maybe I
speak
too soon. I haven't tried a larger ratio and maybe I should. But, it does
incredible for it's situation. Who's to say that Kevin's larger coil
would
not do as well scaled appropriately. That is my rub. Even though PIG's
and
PT's are externally ballasted (not always), doesn't indicate that they
must
be running LTR. They can certainly be running well in STR mode as well.
BPS
is certainly part of their efficiency, but when it comes to power and
sparks, efficiency isn't always the winner. Considering the costs and
size
of components, it's probably economical to do the great spark lengths
inefficiently. I hate to say that (as I'm into alternative energies and
the
like), but the cost of reality probably dictates that situation more than
anything else.
My bottom line is that I'm not sure and I'm pretty sure no one else is
either. If I had the resources and funds, I would strive for efficiency
in
spark length. I know you would also. We all would if we could.
Bart
FutureT@xxxxxxx wrote:
In a message dated 5/27/2008 4:22:54 P.M. US Eastern Standard Time,
FutureT@xxxxxxx writes:
David,
I didn't do the calcs lately but I think it's close to resonant,
maybe slightly LTR. He's running at 120 bps. At 120 bps,
you pretty much have to use resonant or LTR to get good power
throughput.
John
Also (adding to my posting here). Resonant and LTR have a
different meaning for pig and PT coils than for NST coils. For an NST
coil the resonant sized cap or LTR value cap is
a certain value. For a pig or PT coil, the setting of the ballast
determines if the coil operates in STR, resonant, or LTR mode.
At the pig or PT's rated power, there may be a particular value
cap for LTR or resonant. But such a coil can be run at more
or less than it's rated power. For example at 120 bps, a small cap
could
be
installed on a pig coil, a certain amount of ballast can be cranked
in to make it resonant, and it will run, but at less than the
transformer's rated power. For example let's say the resonant
value is 0.3uf. A cap of only 0.03 can be installed, and the correct
amount of ballast can be cranked in to give resonant operation,
and the coil will run. It won't draw much power, and sparks will
be short, but it will be running in resonant mode. Also an "LTR"
value cap can be installed on the pig coil, and the needed ballast
can be cranked in to give resonant operation. Perhaps the
transformer will draw twice it's rated power, but it will still be
able to operate in resonant mode, despite having an "LTR" value
cap. Sparks will be very long in this case. In any case resonant
operation depends a lot on the ballast setting for pig and PT coils,
unlike for NST coils which have a fixed leakage inductance, and
a fixed resonant cap value. If a pig or PT coil is run with a small
cap at high bps, then the ballast L has to be reduced to let in
more power (if long sparks are desired). Then the coil is truly
running in STR mode.
John
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