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Resonant MOTs

Resonant MOTs

While a single MOT doesn't give very impressive arcs, two MOTs and a four MOCs will give incredible arcs. (MOT = microwave oven transformer, MOC = microwave oven capacitor) Running MOTs in resonance has to be the easiest way to get massive arcs as only 7 components are required, all of which can be found in microwave ovens. This also makes then exceptionally dangerous because no skill or knowledge is required to construct a resonant stack.

Schematic

How can it give bigger arcs than a two MOT system? Series resonance. MOTs are designed to have a large leakage inductance, which is the inductance a winding will have when a different winding on the same core is shorted. It can be thought of as an external inductor in series with a winding on the core. So when putting a heavy load on the transformer (like an arc) instead of the winding inductance dropping to zero it will drop to the leakage inductance value which is more than zero. This extra inductance can be used to form a resonant circuit, by including some extra capacitance. MOCs are conveniently sized and rated  perfectly for the task. The resonant circuit consisting of the MOT's leakage inductance and capacitors allows much larger currents to be drawn, and thus longer arcs. To keep the arcs stable a ballast is used. I've found that a primary-shorted MOT put on the secondary side works good. It didn't function as well on the primary side, so maybe it contributes some inductance to the resonance circuit making it more in tune with mains. Either way the arcs couldn't be drawn out very long without it. Although 1 MOC could probably be used alone it's best to give them a good margin. (A trained eye will see that the 4 MOCs have the same capacitance as one.) The resonant voltage rise will put much more than the 2kVAC across them that they're rated for. Mind the phasings, if out of phase the arcs can't be drawn out and will just be short puffs. See Jan Martis' page for more info.

 Youtube video of arcs!




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Disclaimer: I do not take responsibility for any injury, death, hurt ego, or other forms of personal damage which may result from recreating these experiments. Projects are merely presented as a source of inspiration, and should only be conducted by responsible individuals, or under the supervision of responsible individuals. It is your own life, so proceed at your own risk! All projects are for noncommercial use only.