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!
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