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mot powered tesla coil cap question

Discussion in 'High Voltage' started by lokeycmos, Sep 5, 2012.

  1. lokeycmos

    lokeycmos New Member

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    for my second tesla coil i would like to build a MOT powered coil. my first question is, how do i calculate the optimal resonant capacitor if i dont know the exact voltage and current rating of the MOT? when i built my NST coil there was a label with the voltage and current ratings that i could type into TeslaMap(the software i used to calculate my parameters)
     
  2. lokeycmos

    lokeycmos New Member

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    i can find the voltage with a high voltage probe, but i need to find the current rating of the mot as well, so i can accurately calculate the proper tank capacitor. how would i measure this current? could i just use short circuit current? i will be using clamp on ampmeter.
     
  3. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    First of all, you'll need to use a few of them with their inputs in parallel and outputs in series in order to get a voltage high enough for the spark gap to fire. Second, MOTs heat up very quickly, and easily burn out. You'll need to submerge the whole setup in transformer oil to prevent arcs and burning. As for measuring the current, you'll need a large choke to limit current. Unlike NSTs and OBITs, MOTs do not have shunts in them to limit the current (I'm sure you know that already, but I wanted to put it out there in case you didn't). What you can do is take another MOT, short the secondary, and put the primary in series with the rest of the setup. It would be a good idea to put this in oil, as well.

    As I mentioned before, I really don't recommend building MOT powered Tesla coils. They are sloppy, wimpy, have poor insulation (if any), require lots of them, and requires current limiting. Not to mention they're much more dangerous. Normally I'd say don't build one at all, but since you have a little experience under your belt from your last TC, I'll let this one go :p But PLEASE be extremely cautious with this project. Do not work alone! You should always have a spotter when you're working with this sort of power. It will require a lot more work and caution than your other Tesla coil.

    That being said, most MOTs can usually source up to 2 amps, with 0.5A being the most common. It would be very difficult to measure the current, since the voltage is so high. You wouldn't want it to arc over to your ammeter. You'll need a very heavy-duty one that is designed for high voltage applications. You'll need to measure the current while the choke is in the circuit, otherwise you'll blow a fuse (or trip the breaker) in your house.
     

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