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Re: SGTC



Original poster: "Antonio Carlos M. de Queiroz" <acmdq@xxxxxxxxxx>

Tesla list wrote:
Original poster: Frank <fxrays@xxxxxxxxxx>

An interesting question for the group:

Which circuit makes a better SGTC and why?
The main difference is what the power transformer sees at its output.
1) The cap in parallel with the HV transformer and the spark gap in series with the TC primary
The transformer sees high-frequency oscillations when the gap fires. This may damage its insulation.
2) The spark gap in parallel with the HV transformer and the cap in series with the TC primary
The transformer sees almost a short-circuit while the primary circuit is oscillating. Each current reversal produces a fast transient as the gap refires, but the stress on the transformer is much smaller. If there is no arc quickly draining the energy at the secondary, after the primary gap opens the transformer sees a long burst of high-frequency oscillations, but with smaller amplitude than in the first case. Transformers with short-circuit current limited by dispersion inductance, as typical NSTs, can be left short-circuited for long time. The short-circuit current of the transformer is insignificant compared to the RF gap current.
3) The SG in parallel with the HV transformer and caps in series with EACH side of the TC primary
The transformer sees the same waveforms of case 2. Protection against low-frequency shocks is better. It may appear that the capacitors must be two times larger than if they were just one. But with an MMC
construction, the MMC can be just split in two.

In any case, it is advisable to use a filter between the power transformer and the primary circuit.

Antonio Carlos M. de Queiroz