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Hi! A properly adjusted safey gap acts as a safety valve in case the voltage gets too high in your Tesla Coil primary circuit. A safety gap for your NST is actually two gaps, where each gap is connected between an NST HV output and its center tap. A safety gap is not essential, and as long as you never open up your main gaps too wide or never get an accidental streamer hit to the primary circuit, you may never need it. But, it's sort of like driving around without wearing a seat belt - it's not essential, but you'll be very unhappy if it's not there when you unexpectedly need it. NST's are fairly fragile - they are simply not designed to take the high voltage stresses that can come with powering a Tesla Coil. Under certain conditions the voltage in the tank circuit may try to build up to levels that are 5-7 times the faceplate voltage rating of the transformer. High voltages can also be transfered to the primary during accidental streamer hits to the primary circuit. A safety gap will safely discharge these excess voltages before they have a chance to reach levels that would otherwise short out your NST or tank capacitor. The maximum total spark gap length for a 15 kV NST should be between 1/4" and 3/8" depending on the geometry and number of individual spark gap electrodes. The key is to set your safety gaps first so that they are just beyond the point of breaking down (with NOTHING else connected to them other than the NST). You then hook up the rest of the system, bringing it into tune and increasing the coupling to get best results. All of this is done using a relatively short main gap setting. Once you've got the system tuned and set up properly, you can then begin opening up the main gaps. If your safety gaps being to fire consistently, reduce the main gap setting so that you only get sporadic firing of the safety gaps, and you're done! Good luck on your coil! -- Bert --
: Hi,
: What does a safety gap do? How does it work & is it essential?
: Could you please tell me the recommended total spark gap length of a TC
: powered by a 15kV, 30mA NST?
: Thank you
:
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