[Prev][Next][Index][Thread]
Re: Paralleling dissimilar NST's
Hi Gary, all,
My comments interspersed.
> Original Poster: "Lau, Gary" <Gary.Lau-at-compaq-dot-com>
> I'm not sure I agree that paralleling slightly dissimilar Vout
>transformers will result in losses due to "fighting". Consider
>this thought experiment. Take the two 14.5 and 15.5 KV
>30mA NSTs and wire them in parallel, observing correct
>phasing. Apply an AC milliampmeter across the outputs,
>essentially shorting them. Since Vout is now essentially
>zero, their open-circuit Vout difference is no longer
>significant,
Correct, but here is were you are making a (slight) mistake in
my mind. The firing spark gap does NOT present us with a
zero ohm short (as our mA meter does). The current behavior
also depends on the transformer impedance match. The stiffer
of the batch will win out. Of course, I agree that your example
will most likely act the way you describe, but if you were to
parallel a 12kV 120mA unit with a 15kV 30mA unit, it would
definitely NOT result in 13.5kV and 150mA output power. It
will lean more toward 12kV and maybe 130mA output. The
rest is wasted in the form of heat. My true point was to
MEASURE and NOT guess what your psu will deliver in order
to get the best from a given setup (which is what most of the
more experienced coilers are out for).
To most others, this slight mismatch is of no importance, but
if you are designing a LTR coil, you want to know *exactly*
what your psu is able to deliver to match the cap correctly,
esp. if you are a TC "squeezer" (i.e. largest spark length for
a given setup).
>but yet their short circuit currents would combine to yield
>60mA. Open circuit, their voltages should average
>out to 15.0KV,assuming similar winding resistance.
Also correct, I was making a point of paralleling xformers
with dissimilar output voltages and here I made the point
that 3kV is the max difference "I" would use, because
otherwise you will be wasting some effort. Of course, if
you only have, say a 15kV and a 9kV then by all means
parallel them, just donīt expect a huge increase in power
capability. It WILL increase, but not as much if you could
choose optimum conditions.
Coiler greets from Germany,
Reinhard