Switching high voltage (5KV+)

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Howdy folks - in the near future I may need to build a circuit that switches on/off a high voltage (5-10KV) load. I can switch either the high or the low side. Current will be in the microamps.

All the relays I'm seeing are massive - like multiple inches in one dimension. Is there anything smaller out there? I'd prefer a solid state solution, but a physically small mechanical relay would be OK too.

Thanks!!!

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No doubt you will use a fly-back inverter of some sort!
Switch the supply voltage to the inverter & don't switch the HV output at all.

Charles Darwin, Lord Kelvin & Murphy are always lurking about!
Lee -.-
Riddle me this...How did the serpent move around before the fall?

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If you really need to switch the high voltage, I think you will find that anything that will handle 5 or 10kV is going to be large. Physics. You just need lots of distance between the conductors at this kind of voltage. (Keep that in mind when you are laying out your circuit.)

I would think a relay would be a good choice. If you're switching AC, some kind of Thyristor (triac or scr) circuit might work.

~LMG

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Reed relays are small. You will have to research ones that can handle the high voltage. The contact gap would need to be wide for that and also there is the problem of it drawing an arc as it opens. You may be stuck with a large device.

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http://www.rossengineeringcorp.c...

Its also possible (but not easy) to cascade MOSFETs

Ho fast and how often do you need to switch ?

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Here is a good link to Tyco informational section on high voltage relays..

http://relays.tycoelectronics.com/kilovac/hvintro/

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Here is what you want! 5KV, 12 VDC coil. looks small in form factor.

http://relays.tycoelectronics.com/datasheets/s06fna218.pdf

7kv+
[url]
http://relays.tycoelectronics.co...

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ossi wrote:
http://www.rossengineeringcorp.c...

Its also possible (but not easy) to cascade MOSFETs

Ho fast and how often do you need to switch ?

Those are quite large!

My switching speed is slow - maybe a tenth of 1 hz. How would one go about cascading FETs? Just put them all in series, with maybe some huge resistors in parallel to balance leakage current? Controlling the gates would be hard - and with my slow switching speed most AC type floating gate drivers won't work...

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alwelch wrote:
Here is what you want! 5KV, 12 VDC coil. looks small in form factor.

http://relays.tycoelectronics.com/datasheets/s06fna218.pdf

7kv+
[url]
http://relays.tycoelectronics.co...


Heh, two and a half inches long! That's a wee bit big still...

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alwelch wrote:
Reed relays are small. You will have to research ones that can handle the high voltage. The contact gap would need to be wide for that and also there is the problem of it drawing an arc as it opens. You may be stuck with a large device.

I've heard that some HV switches are hermetically sealed and filled with some gas (or maybe a vacuum) which makes the arcing distance a lot larger for the same voltage, allowing the relays to be smaller. Not sure what these are called, however.

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lgriesbach wrote:
If you really need to switch the high voltage, I think you will find that anything that will handle 5 or 10kV is going to be large. Physics. You just need lots of distance between the conductors at this kind of voltage. (Keep that in mind when you are laying out your circuit.)

I would think a relay would be a good choice. If you're switching AC, some kind of Thyristor (triac or scr) circuit might work.

~LMG


It'll be DC, not AC. I figured I'd pot the whole thing to allow me to jam components closer together.

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Quote:

It'll be DC, not AC.

Automotive ignition parts?

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

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Here are some that are one inch long..

http://www.pickeringrelay.com/highvoltage.htm

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alwelch wrote:
Here are some that are one inch long..

http://www.pickeringrelay.com/highvoltage.htm


Nice find! Those are starting to be close to being usable... Still way bigger than I'd like, but not bad at all! Funny thing is they're not much smaller than some high voltage power supplies I've been looking at: http://www.emcohighvoltage.com/Q...

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theusch wrote:
Quote:

It'll be DC, not AC.

Automotive ignition parts?

I think in auto ignition all the switching is on the low voltage side? I could be totally mistaken though.

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The rotor of the distributor is on the high side (old style ignition systems). The breaker points are on the low side.

The rotor does not break an active arc,. however, and the switch is (almost) closed every time a spark goes.

Jim

 

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