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Registered Member #611
Joined: Wed Mar 28 2007, 11:40PM
Location: Hudsonville, Michigan
Posts: 79
I made a modification to my spark gap to get better quenching. The arc length from break out increased by 4 inches, from 32" to 36". Now my safety gap is firing like mad. It will start firing after about 20 seconds at full power and then continue to fire every few seconds after that. I disconnected the main gap and hooked the transformers directly to it to make sure it isn't too wide and it checked out fine. Then I did the same with the safety gap to make sure it wasn't too narrow and that checked out fine. I've tried moving the tap around to see if maybe the coils were out of tune but that doesn't seem to be the problem either. I don't know what else to check. Does anyone have any suggestions? Here's the project thread with all the coil specs -
Registered Member #530
Joined: Sat Feb 17 2007, 07:56AM
Location: Victoria BC, Canada
Posts: 178
I noticed I got the same thing when I had my spark gap pull out a bit. What causes the safety gap to fire is higher than normal voltages present in your discharge gap...this in turn causes your transformers to see higher than normal voltages too. A 15kV NST can see 20 kV peak during discharge...too far out and your caps could very likely blow. I'd put your spark gap closer together and run a blast of cool air through it... and you'll get MUCH better quenching.
Registered Member #611
Joined: Wed Mar 28 2007, 11:40PM
Location: Hudsonville, Michigan
Posts: 79
I spent all day yesterday messing with the gaps, checking and rechecking the measurements, cleaning the electrodes and testing each of them.They were set just fine. The main gap is set to .24" total spacing (I measured it 5 times) and it fires at about 112 volts on the variac with just the NSTs connected. The safety gap is set to .28" and it just fires at full power on the variac (140 volts).
So I was thinking maybe the fan I was using might be the problem. I replaced it with a vacuum cleaner motor and drilled some holes in the coupler to force the air to flow in between the electrodes. I hooked it up and holy cow, what a difference. The arc length increased by 6 inches. The safety still fires every once in a while but no where near as often as it was.
I took some video of a 38 inch strike from break out point to grounded target.
Registered Member #530
Joined: Sat Feb 17 2007, 07:56AM
Location: Victoria BC, Canada
Posts: 178
Well, you solved that problem. Every system has its bugs to work out and setting a spark gap too wide can be nasty, especially on your caps. When everything is in tune the safety gap barely fires at all! Sounds like it was just an issue with the quencing...
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Safety gap is firing like crazy
