Jim-
Thanks. Yeah I'm running a 12kv 30mA nst. Actually picked up a second 12kv 30mA nst yesterday at work. I do controls for grocery stores so I get a lot of demoed parts. It's already too late for me lol. I'm hooked. My safety gap doesn't fire till I put it all together and run it. Starts off like 1 x every 10 seconds then starts jumping up faster. I unplug it before it really goes crazy. I have a variac but it's only rated at 5 amps? A little specs on my set up:
3"secondary @ 18"-20" long. 26awg wire roughly 850-900 turns. Ran out of wire. Planned on 1k turns. Coated in polyurethane.
Primary 1/4" soft copper at 14 turns tapped at 9 1/4 turns at 1/4" spacing. The primary first turn is roughly 3/4" - 1" away from secondary pipe. The elevation is roughly 2" from where the secondary windings start. Used terry fritz TCT and that seems to match up with secondary tune
17 p15k-f Cornel Dublier caps at 2kv each. Wired only in series. Might do two strings to see how it reacts.
Top load is a two piece. Experimenting.
3" aluminum duct. Inside diameter is about 2 7/8" and out side is around 9"
Second top load on top of the first one is bigger but about 2" on not mesurments.
Nst is on mains ground but my secondary is on RF ground. Hammered 5/8" copper rod into my yard and ran a 14awg wire approx 8-10 ' to secondary. Also have a line filter going to mains plug in reverse.
Only getting arcs to a 1/4" copper rod I have zip tied to the leg post. Nothing to the air. Arcs are about 7-8" so far. Looks good but I want it without the rod lol. My top load is fixed together with electrical tape which im about to change and get some foil tape from hardware store. Any tips or suggestions is very welcome and appreciated. Thinking about hooking the other nst in parallel but not sure caps can hold up. Not really sure if it matters to have caps in one string.
>> On May 8, 2015, at 10:04 AM, Jim Lux <jimlux@xxxxxxxxxxxxx> wrote:
>>
>> On 5/8/15 6:16 AM, Kerry Soileau wrote:
>> Hey guys. I got my parts in yesterday. 5 days early! Spent 6 hours
>> winding a 3"x 22" coil on a microwave turn table motor.....never
>> again lol.
>
> you say that now, but pretty soon, you'll be winding a 4", and then a 8"... step away now while there's still time... (oh, it's too late<grin>)
>
>
> Anyway my question is, how far should my safety gap be for
>> my MMC bank. Thanks in advance.
>
> I'm assuming you're running a neon sign transformer(NST)..
>
> I set my gap so that it just doesn't fire when just the transformer is hooked up. If you've got a variac, you can probably run the primary voltage up a bit when setting the gap. 120V is almost certainly safe, 130 is pushing it. NSTs are a "cost conscious" design and don't have a lot of reserve capacity or designmargin.
>
> To a certain extent, the safety gap is like the "brave screw" on a turbocharger boost controller. If you've got a box full of spare transformers, you can be a bit more brave.
>
> But realistically, if you've got a box full of transformers, the way to get bigger sparks is to parallel transformers and run more current, keeping the voltage conservative.
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