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Coil and Resonance Basic Questions...

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  • Coil and Resonance Basic Questions...

    Hoping someone can shed some light, really hard to time finding straight answers to these beginner questions related to coils in resonance...

    1. In a Tesla coil what sets the operating frequency of the primary coil? I know the secondary is determined by the self capacitance and inductance of the wire.

    2. In regards to strictly an air core resonant transformer with primary and secondary now, if the primary is wound to 1/4 wave of the secondary, will it function in resonance regardless of whatever sine wave frequency it is driven at? I understand it will be much more efficient if driven at a rate that is the resonant frequency or harmonic of. But what if driven by any ac frequency? I hope this makes sense.

    3. Is it best to determine 1/4 wave length of primary compared to secondary by weight of each, or length? I always wanted t know this, as I did not understand how just length could be accurate based on different gauge wires between primary and secondary.

    4. Kind of relates to question 2, but does the spark gap in a Tesla coil set the operating frequency of the primary? Or is it simply to create a pulsed dc spike each time it discharges to drive the primary?

    I hope these all make sense, they have been on my mind for months, thank you all. Cheers

  • #2
    I'm no expert, I haven't built a Tesla coil as such, but I have tinkered, so I'll start the ball rolling. Someone can fine tune or correct this later.

    As far as I can tell, the idea of a Tesla coil is that the secondary is 1/4 wavelength resonant and the primary is LC resonant, and you get lots of sparks, when they are both tuned to the same frequency. I just have to pretend that making sparks is the ultimate objective here.

    You'll probably find that the primary is determined by the coil's inductance and capacitance, and the secondary is determined more by the wire length and to some degree, the thickness.

    i'm not sure what you would end up with, if you wound a transformer with a primary 1/4 wavelength of the secondary, or how you would drive it. Maybe with 1 wire? The Don Smith guys might know more about that. There's mot much point to driving anything out of resonance, you just don't see any action.

    In the Don Smith thread there is mention of the primary having a weight relative to the secondary, but I don't think they are making a classic Tesla coil.

    Spark gaps have frequencies too, determined by the distance of the gap and the voltage, and can be tuned by various means.