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Stacking Transformers for Ultra High Voltage

Discussion in 'Power Electronics' started by Experimentor, Jun 28, 2021.

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  1. Experimentor

    Experimentor

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    Jun 19, 2021
    I am wondering if one could stack step-up transformers to achieve ultra high voltage. Asked another way, what problems would one run into running transformer after transformer in series to achieve say, one million volts?
     
  2. Alec_t

    Alec_t

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    Welcome to EP!
    I think that unless you had independent isolated supplies for the primary windings they would all be mains referenced, so the high voltage on the secondaries would break down the primary-to-secondary insulation.
     
  3. DBingaman

    DBingaman

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    Jun 27, 2021
    I take it you mean something like this:
    TransformerFun.PNG
    Given Pin=Pout. So say you have an effective turn winding of 10,000 to 1. At 10Vac in you get 100,000Vac out. But if you have say 10uA current being drawn by RL you will need 1 Amp of current input for the windings! After thinking about this more, I think Alec_t may have a good point. The high voltage on the top side of RL very much wants to get to the bottom side of RL and could arc backward through the transformers to do it. From the high voltage circuit perspective, each transformer looks like a capacitor that naturally is going to have a breakdown voltage. Though you may get away with this for up to 1000V I doubt you will get anywhere close to 1MV.
     
    Last edited: Jun 28, 2021
  4. Bluejets

    Bluejets

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    Agree.
    High voltage arc over is the biggest hurdle when winding a basic ignition system coil and that's only a couple of thousand on model engine coils.
     
    DBingaman likes this.
  5. Experimentor

    Experimentor

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    Jun 19, 2021
    What I had envisioned was power source connected to the first transformer's primary and that transformer's secondary connected to the next transformer's primary and so on. If this won't work to achieve higher and higher voltages, why not and is there a workaround?
     
  6. DBingaman

    DBingaman

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    Jun 27, 2021
    In other words this?
    CONFIG2.PNG


    I have highlighted why this will not work in red text. The first transformer will have 900VAC between the primary and secondary, the next one will have 9000VAC etc. In short order the voltage difference between the primary and secondary will be large enough to cause arcing from the secondary, back to the primary and from the primary back to the secondary as shown by the dotted red line.
    Notice I placed small caps between primary and secondary (internal stray capacitance from secondary to primary), the limit is the breakdown voltage of this capacitance. Which is probably no more than a 1000V or less.

    Your second question about what to do about this. I really don't think there is anything you can do about this. Even if you could achieve 1MV. The next problem is the load on the output must draw very little to no current. Imagine in what I have shown that the current to output stages is 10 milliamps that would make the input current 10 Amps to maintain that.

    What are you trying to accomplish by doing this? Would a high DC voltage be acceptable?

    There are few circuits around that can handle 1MV or more. I would recommend building a Tesla Coil.
     
    Last edited: Jun 29, 2021
  7. DBingaman

    DBingaman

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    Jun 27, 2021
    The other issue I did not bring up:
    1. At each stage the dV/dt is going up by a factor of 10. Because Ic=C(dV/dt). Ic will be going up as well. The stray capacitance is going to load down the higher voltage transformers more because they also have a higher impedance. That impedance will get fed backward thus requiring significantly more current from the AC source. Also each transformer has it's own natural losses, these are going to add up fast.
     
  8. Experimentor

    Experimentor

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    Jun 19, 2021
    Thanks for your reply including the graphics.I was wanting to just do some experiments to try and learn how electricity behaves. But of course I want advice before I begin, and thanks for yours!
     
  9. DBingaman

    DBingaman

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    Jun 27, 2021
    That is fine, and this should work for demo purposes up to say 600-1000V without an issue. But there is no way you will get anything above that due to transformer insulation breakdown. Keep in mind the load of the final output needs to be small. If you are using 120VAC you could run into problems because most of the time these transformers down-convert from a higher voltage to a lower voltage, when you use them the 'other way round' the inductance/resistance may be way to low for the transformer to handle and could burn up the transformer. Be sure to measure the DC resistance of what you want to be the primary. Then calculate power V^2/R if this is to high for the given transformer the thing is going to either blow the house breaker or burn up the transformer. The normal secondary resistance is typically fairly low, this is going to cause a significant power loss in the transformer. Granted if the transformer has the ideal 0 power factor with no load (nothing should happen) BUT realistic power factors for transformers can be 0.3 to 0.5.
    Just realize if you burnup the transformer or blow the circuit breaker don't be surprised.

    If you just want to experiment with how transformers work, then using a function generator put in a pure sine wave of whatever the output is rated for (say 12VAC) the output when ran in reverse like this should be 120VAC. But again the function generator may not have the necessary output current capacity to deal with the transformers greater than zero power factor.
     
  10. DBingaman

    DBingaman

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    Jun 27, 2021
    If you just want to experiment with insanely high voltages, take a look at the different projects on the internet that give you all the gory details of creating a Tesla Coil. If you do decide to create one of the on line projects of a Tesla coil, be extremely careful. Do it in a work shop on a separate breaker from the house. Keep the thing far away from sensitive electronics (computers, etc.) A Tesla Coil can put out enough EMF to literally destroy nearby low voltage electronic equipment. Even the in air volts per meter is insane. In our electronics class back during my Vo-tech years we had a Telsa Coil. The primary capacitor was literally a bath of 10-W30 oil with Aluminum sheathing as the plates over an area of about 2-3 foot square. One person got to close to it and literally burned the skin on his forearm 1/2 inch wide to 5 inches long with 3rd degree burns.

    Take a look at and follow the following instructions for any circuit that generates MegaVolts especially a Tesla Coil:

    http://onetesla.com/oneteslats-manual/safety
     
    Last edited: Jun 30, 2021
  11. DBingaman

    DBingaman

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    If you decide to start messing around with circuits that put out millions of volts, be sure to take all necessary safety precautions! Be sure to be on a wooden floor when working with it. Do NOT bring BOTH hands in contact with any of the parts! You could easily be electrocuted. I don't want to be responsible for getting someone killed. Please pay attention to ALL safety requirements when building ANY circuit that is capable of putting out MVolts!
     
  12. DBingaman

    DBingaman

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    Jun 27, 2021
    If you just want to learn how electricity behaves, I would recommend using a power supply that is adjustable from 0 to 20-30V. This will keep you from destroying your O-scope or your DMM or any other test equipment and still allow you to perform experiments without worrying to much about getting a nasty shock. IMHO
     
  13. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    ... or your personal health...
     
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  14. DBingaman

    DBingaman

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    Jun 27, 2021
    If you are new or even a seasoned expert in Electronics, one of the best investments you can make it into a book titled 'The Art Of Electronics'. Many circuit designs are discussed along with exercises. The book is a little expensive, but it is worth the investment.
     
  15. VenomBallistics

    VenomBallistics

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    Aug 30, 2018
    Of important note is an unintended hazard of high voltage antics.... Production of X ray radiation is a possibility
     
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  16. bertus

    bertus Moderator

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  17. DBingaman

    DBingaman

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    Jun 27, 2021
    Interesting. I was not aware of that. From internet search it appears that the only situation that X-rays get created is within a high voltage vacuum tube where electrons emitted from the cathode get accelerated to extremely high speeds over a fairly long distance then when striking the anode they 'stop' releasing all the energy as X-rays. Is there other situations of High Voltage than can result in X-rays or other dangerous radiation sources?
     
  18. bertus

    bertus Moderator

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    Nov 8, 2019
    Hello,

    I am not aware that high voltage alone can produce X-rays.
    I do know that high voltage can create arcs that will produce ozone.

    Bertus
     
  19. VenomBallistics

    VenomBallistics

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    Aug 30, 2018
    It's been said to occur with some of your more zealous tesla coils as well
     
    DBingaman likes this.
  20. crutschow

    crutschow

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    May 7, 2021
    You might also look at a Van de Graaff generator.
    Requires no electronics.
     
    VenomBallistics likes this.
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