You might have seen them all. Flyback transformers, microwave oven transformers, ignition coils, oil burner transformers, potential transformers, pole pigs, x-ray transformers, high voltage switched mode supplies, Tesla coils and the list goes on. However, have you ever thought of a possibility of drawing arcs directly from mains current?
Of course, it’s not that easy as shorting your receptacle out, unless you wanted to bypass your circuit breakers and burn your house down. For this you’re going to need a current limiter – for this experiment, inductive loads such as chokes are the best.
In my configuration, instead of chokes I used two microwave oven transformers (MOTs) with their high voltage secondaries shorted out, because their inductive reactance is too high when unloaded. Of course, you’re free to choose any reasonable iron-cored chokes or ballasts designed for big currents (above 15-20A), such as those ones for high-pressure sodium bulbs. They’ll do perfectly the same.
To keep the arc stable, a rectifier is also a must, rated at least 16 amps and more. For prolonged run I’d suggest an adequately-sized heatsink, too. You can also add some filtration electrolytics if you like, but that’s not needed.
To wire it all up, place your first choke (above 50 mH is good) in series with the rectifier. The second choke goes in series with the output electrodes (rectifier output). That’s all – the lower your inductance is, the higher the current you’ll get You can also experiment with more chokes placed in parallel with the first one.
Just be sure to use big-ass chokes rated for high currents (or transformers, with a suitable leakage inductance) as mentioned above, since this circuit works like an arc welder. Because the arc is very intense you shouldn’t really omit some eye protection along the way. Since it runs at mains potential, avoiding contact with live electrodes is also a good thing.
Arcs, arcs and even more arcs