I have a 10 kV 23 mA ignition transformer.
Apparently the way to make a jacob's ladder is to just connect the electrodes to the secondary, plug the primary into the wall, and call it good.
But of course, as a transformer this thing has no current limiting, and I have no way to calculate the effective resistance of the arc. (I'm guessing a theoretically perfect transformer has no current limiting, but a real life one probably might limit current in some manner I am not familiar with, magnetic saturation, etc, but I'm guessing also this is not the "correct" way to limit current when designing a circuit)
What's the best way to limit current here? I can use a power strip that will trip at 1800 W, but this thing will draw 230 W at the max of the spec.
Do I just fuse it at, say, 0.5 A on the primary side and use a slo blow to avoid blowing the fuse on the inrush?
Or do I use a single resistor on one half of the secondary side to limit the current?
Or use a variac on the primary side along with a killawatt meter to measure the current draw as I turn up the voltage?
What's the correct approach here?
Yes, I have worked with HV before and I understand this thing will kill me easily, I have built plenty of woodburners with scrap MOT, etc and I know how to handle HV.
Best Answer
What has worked well for me with such transformers is 100 watt light bulbs in series with the primary voltage. Add more bulbs in parallel for more current.
The reason is that incandescent light bulbs are very non-linear about current consumption. As the current rises the filament in the bulb get much hotter and its resistance goes way up, limiting the maximum current flow.
If the transformer shorted the lights would come ON full brightness. As it is they will flicker with changing loads on the high-voltage side. Do NOT try resistors as they will simply get hot as a linear device. Do NOT try them on the high-voltage side as the voltage will just arc across the resistor and burn it up.
I know farmers who do this for their electrified fences to protect the transformer, and to limit the current when cattle or horses touch the wire.