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Matthew,
If you put the spark gap across the transformer, as seems to be the
current best practice, then the gap essentially shorts out the
transformer during the time that the gap is firing. I once read that,
to a close approximation, the impedance of nearly any electrical arc is
about 600 ohms.
That is not a problem, because NSTs are current limited, and will
happily drive their rated output current into a short circuit all day
without damage.
A ballasted potential transformer, like a pole transformer, can also
drive a short circuit for a reasonable period of time. The spark gap
normally fires for only a small percentage of the entire 60 Hz waveform.
Putting the gap across the transformer is considered a good idea because
it reduces the induction of big voltage spikes in the NST or PT
windings, which would be expected to happen if the gap is NOT across the
transformer inputs.
Good quenching of the spark gap is important, though to prevent the
development of power arcs, which would prevent the transformer from
charging the TC tank circuit.
Dave
On 7/26/2018 6:11 PM, Matthew Sweeney wrote:
That makes sense, I always assume the spark gap In series.
So when the transformer 'shorts' across the gap what happens to current
draw?
That might be a trivial eletrics lesson but I find myself kind of lacking
when it comes to NSTs.
Thanks!