Re: NST's in parallel

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Drake Schutt" <drake89@xxxxxxxxx>

With all of this talk of primaries and secondaries Im guessing im 
going to have to depot my xformers.  I will need to research circuits 
of NSTs more indepth me thinks.

On 5/7/06, Tesla list <<mailto:tesla@xxxxxxxxxx>tesla@xxxxxxxxxx> wrote:
Original poster: Ed Phillips < <mailto:evp@xxxxxxxxxxx>evp@xxxxxxxxxxx>

Original poster: "Drake Schutt" <<mailto:drake89@xxxxxxxxx>drake89@xxxxxxxxx>

Hello all,

I am a bit curious about wiring neon sign transformers in
parallel.  All i know is that you connect the cases together and
connect the positive and negative leads together (there's probably
more to it than that).
Also it has been said that it is best if the NSTs are the same
voltage, amperage, brand name, etc.  Is it possible to wire up some
NSTs in parallel with different voltage and amperage ratings?  If so
how would you calculate the total wattage?  What about the same
voltage/amperage transformers but different brands?

any response is appreciated as always,
Drake "

    Certainly it works - I've used a 12 kV and 15 kV 60
ma  transformer in parallel and no problems at all.  To figure out
what you're going to get with a resistive load you need to know the
voltage and leakage reactance of each transformer.  You can then draw
the parallel equivalent circuit with various voltages and reactances
and calculate the total current deliverd at any terminal voltage LESS
than that of the lowest transformer.  Any transformers whose
open-circuit voltage is lower than the operating voltage will
actually have current flowing into them, which of course doesn't
help.  An equivalent method is to pick a hypothetical output voltage,
consider each transformer by itself and calculate the current
flowing, then add up the results.

     Things get a bit more complicate if you're feeding a capacitive
load of course.

    I suspect the difference in brands is relatively small but have
no data to back it up as all the transformers I have are Franceformers.

Ed