Hey guys,I'm looking for some sort of mosfet/relay/switch that can

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petitericeball
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Hey guys,

I'm looking for some sort of mosfet/relay/switch that can handle up to 1 milliamp and 8kV. I don't understand the technology very well, but from talking to some people, I know I can put 2 4kV mosfets in series to achieve my 8kV goal. On the other hand, while looking for relays, I couldn't seem to pin any down. My friend said that voltage wouldn't matter in a relay, as long as the current isn't too high, but when looking on digikey, the relays had voltage ratings, where all of them were too low for my application.

Here is the 4kV mosfet

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=IXTV03N400S-ND

Thanks,

Danny
 
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Voltage most certainly matters in relays--with very high voltages, you can get arc-over (which will deteriorate your contacts over time, assuming you don't have continuous arcing) or the contacts arc-welding together and not de-latching. To avoid these sorts of issues, I think most of these relays are either inert-gas filled or contain a vacuum.

I don't have a great deal of experience in the high-voltage switching regime (so hopefully someone with more experience weighs in), but I'd avoid trying to put multiple ones in series--at the point and moment of contact, you can have all of the high voltage across a single contact (or junction, if you're using a solid state relay / MOSFET).

When I Googled for high voltage relay, I found some by a unit or two that Tyco had acquired:
http://relays.tycoelectronics.com/high_volt.asp

Meder also seems to sell 10 and 15 kV rated reed switches:
http://www.meder.com/high-voltage-relays6.html

As expected, you're probably looking at a hefty price tag.

EDIT: Actually, when I clicked on the Meder "Check distributor stock" link, there are some 7k5 and 10k relays at Mouser / Digikey for <$100, and even less at TTI!
http://service.stkcheck.com/Default.aspx?mfg=b0629033-c213-4a47-aba9-65a840d82710&parts=H__
 
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petitericeball said:
After looking around, I think I found some for around $30

I'd definitely spec for higher rather than lower voltage (the 10kV ones seem to be in the $40-$50 range, rather than the $30 range that most of the 7k or 7k5 ones sit at). TTI seems to have the cheapest for the Medco high voltage reed relays, but I've never used them before.
 


What is the switching frequency.
You can switch at lower voltage and use a step up transformer.

Have you looked at IGBTs.
Real high power switching is done with ignitrons.