Any electrical engineers out there??

[Super God]

Hello,
I need help in finding a device that can comfortably switch a high voltage (upwards to 30kv) and relatively high current (5 amps) at upwards of 120 Hz, for very short periods of time (enough to make a spark much like a distributor does).  I thought about a relay but the contacts would surely wear out quite fast.  Solid state seems pretty hopeless as well, I don't think it could handle the high voltage.  The only thing I can think of would be to generate it as AC and use a diode to clip it off at the top or something.  I really don't know much about what's out there (as far as switching devices go).  Could anyone give me some advice?

[Groundloop]

@Super God,

I think you will need a rotating spark gap.

http://www.richieburnett.co.uk/rotary.html
http://www.ias.ac.in/sadhana/Pdf2001Oct/pe941.pdf

Groundloop.

[hansvonlieven]

Hello,
I need help in finding a device that can comfortably switch a high voltage (upwards to 30kv) and relatively high current (5 amps) at upwards of 120 Hz, for very short periods of time (enough to make a spark much like a distributor does).  I thought about a relay but the contacts would surely wear out quite fast.  Solid state seems pretty hopeless as well, I don't think it could handle the high voltage.  The only thing I can think of would be to generate it as AC and use a diode to clip it off at the top or something.  I really don't know much about what's out there (as far as switching devices go).  Could anyone give me some advice?

I need to know the frequency of interruption and the duty cycle. i.E. how many times per second do you need to switch on and for how long. This is critical. Perhaps mercury can help here.

Hans von Lieven

[AbbaRue]

I would suggest you use an argon discharge tube. The 2 plates are placed a certain distance apart as 2 capacitor plates.
Then you charge up the plates until the  argons brakedown voltage is achieved.
You just need to adjust the plate distance to get the frequency you need at the voltage you need.
Do some research on discharge tubes to get an idea of the plate distance and such.

[gyulasun]

Hello,
I need help in finding a device that can comfortably switch a high voltage (upwards to 30kv) and relatively high current (5 amps) at upwards of 120 Hz, for very short periods of time (enough to make a spark much like a distributor does).  I thought about a relay but the contacts would surely wear out quite fast.  Solid state seems pretty hopeless as well, I don't think it could handle the high voltage.  The only thing I can think of would be to generate it as AC and use a diode to clip it off at the top or something.  I really don't know much about what's out there (as far as switching devices go).  Could anyone give me some advice?

Hello Super God,

There are two solid state solution possibilities, one that relatively cheap and one that is expensive.

Here is a link to a relatively cheap circuit:  http://bromine.cchem.berkeley.edu/grppub/frbm2.pdf   this shows 10 power MOSFETs connected in series to increase working voltage up to 8kV with fall time of 230 nanosecond.  This circuit also gives a good example of how to drive the MOSFET switches correctly to separate the low voltage side of the switch from the high voltage side. Of course if you need a switch up to 30kV, the total number of components needed to build the series connections may not be the cheapest choice but perhaps still reasonable.

The other solution can use high voltage MOSFETs directly, no need for series connection because they are directly manufactured for really high voltage switching.  A German manufacturer site is here: http://www.behlke.de/

For instance here is a data sheet for a 33,  50 and 65 kV solid state switch family with a min 200ns on-time for max 17-30 Amper peak currents**    and here is a push-pull device for switching  2x16kV and 2x30kV http://www.behlke.de/pdf/301-03-gsm.pdf .  There are many devices with fixed on-time and variable on-time possibilities too.  Be prepared for the prices though...

rgds,  Gyula

**EDIT: I supplied the missing link http://www.behlke.de/pdf/331-03-lc.pdf