Re: SGTC

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Mddeming@xxxxxxx 


Hi Frank,

All three will work, and some folks have had long term success with 
each. However, it has been demonstrated over many years and many 
coils that option (2) Gap Across Transformer results in greater 
transformer life expectancy. The simple explanation is thus:

    With the capacitor across the transformer, there is 
high-voltage, high frequency across the HV windings each time the gap 
fires and the capacitor discharges. With the gap across the 
transformer, the transformer "sees" a low resistance short across its 
terminals while the gap is conducting, so there is low-voltage high 
frequency across the HV windings which is much less stressful. When 
the gap stops firing, the transformer will see High Voltage, but at 
that time, the RF energy will be at a minimum. This arrangement also 
tends to keep more RF "Hash" out of your power supply.
    NSTs and OBITs are the most vulnerable to these stresses and 
pigs less so, but IMO it's a good general practice.
    Option three, the so-called Equidrive configuration, was 
believed 100+years ago to offer some advantage, but subsequent 
investigations have proved inconclusive.

Matt D.

In a message dated 4/25/07 5:02:03 A.M. Eastern Daylight Time, 
tesla@xxxxxxxxxx writes:
Original poster: Frank <fxrays@xxxxxxxxxx>

An interesting question for the group:

Which circuit makes a better SGTC and why?

1) The cap in parallel with the HV transformer and the spark gap in
series with the TC primary

OR

2) The spark gap in parallel with the HV transformer and the cap in
series with the TC primary

OR

3) The SG in parallel with the HV transformer and caps in series with
EACH side of the TC primary

I have plans dating back 100 yrs to the present and all
configurations are used for small and large coils. There does not
seem to be any preference and I have circuits using 20 KV
transformers with all options above.

The gap in parallel configuration seems to be slightly more present
in designs but not by a large margin.

The SG in parallel adds some over volt  protection to the HV xfmr but
also the risk shorting the transformer is present if the gap is left
closed for any amount of time.

The third option completely isolated the TC primary from the HV
transformer making it by far the safest for shock hazards.

Thanks, Frank






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