3

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

Dirk Bruere
  • 13,425
  • 9
  • 53
  • 111
  • 4
    Would a spark gap be suitable? 5mm or so would do. – Jack B May 15 '19 at 12:19
  • 1
    @JackB Once the arc started it would not stop – Dirk Bruere May 15 '19 at 12:19
  • "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. – JimmyB May 15 '19 at 12:46
  • WHat impedance or power will it take to regulate it? What capacitance , what resonance? – Tony Stewart EE75 May 15 '19 at 13:30
  • 2
    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. – Russell McMahon May 15 '19 at 13:32
  • In the olden days of yore, they used glow discharge tubes for this. Neon lamps and the like. They have a similar current-voltage characteristic to avalanche diodes and function as pretty effective shunt voltage regulators at higher voltages. But I don't think they come in multi-kV ratings. – Hearth May 15 '19 at 14:19
  • Incidentally, why are you looking for a way to do this without arcover if the transformer is damaged if there is no arcover? Are you intentionally damaging the transformer? – Hearth May 15 '19 at 14:21
  • @Hearth I want a HF HV field in an airgap inside some insulation. Silent electric discharge plasma – Dirk Bruere May 15 '19 at 14:58
  • Are you concerned with the plasma channel that the arc provides? They make vacuum spark gaps which should extinguish more quickly. In fact, it almost feels like what you want is a vacuum tube so you can control it a bit. – Drew Macrae May 15 '19 at 17:51
  • @AndrewMacrae No, I want a cold plasma – Dirk Bruere May 16 '19 at 08:29

1 Answers1

1

  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.

MadHatter
  • 3,506
  • 1
  • 19
  • 45