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I have a high frequency high voltage module that puts out about 15kV (not the stun gun modules sold on eBay). Because of the circuit design the transformer is damaged if it does not arc over. I am looking for a method to limit the voltage when I feed it into a capacitance, with no arcover. I want a 15kV HF voltage on that rather tiny capacitance which is formed by a microscope slide with foil on both sides

One obvious thought is a resistor, but not sure how viable. The other is of course the Zener above, but I don't think anyone makes such a device, and certainly not cheaply. OTOH, would the capacitor itself act as a suitable sink?

Before anyone asks, I do not yet know the frequencies involved. However, the device itself that I am considering using is this

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    \$\begingroup\$ Would a spark gap be suitable? 5mm or so would do. \$\endgroup\$
    – Jack B
    May 15, 2019 at 12:19
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    \$\begingroup\$ @JackB Once the arc started it would not stop \$\endgroup\$
    – Dirk Bruere
    May 15, 2019 at 12:19
  • \$\begingroup\$ "the transformer is damaged if it does not arc over" ... "I am looking for a method [...] with no arcover." - Sound's like it's a) impossible or b) more complicated than a passive device can accomplish. Note that once the arc has formed the voltage significantly drops. \$\endgroup\$
    – JimmyB
    May 15, 2019 at 12:46
  • \$\begingroup\$ WHat impedance or power will it take to regulate it? What capacitance , what resonance? \$\endgroup\$
    – Tony Stewart EE75
    May 15, 2019 at 13:30
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    \$\begingroup\$ If you can have or add an extra lower voltage winding then you can clamp that at a proportionate level. A link to a data sheet or a diagram or description of the unit would be useful. | Arcs can be made self extinguishing by having then run up a diverging path. Arcs can be magnetically snubbed. \$\endgroup\$
    – Russell McMahon ♦
    May 15, 2019 at 13:32

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  1. Multiple high voltage MOVs in series with limiting resistor. (Assuming you have DC at this point and not HF AC)

  2. Could current limit a high speed diode (string in series) so when they suffer reverse breakdown it safely cuts the voltage but does not burn out the diodes. A few 1kV diodes would work.

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