This info may or may not apply to the relays Rich is offering. Hopefully he
can make comment since he can measure the breakdown voltage for his relays.
The contact voltage is what we usually worry about but the breakdown between
the contacts and mounting flange as well as to the coil are also important.
I have been waiting for someone to mention vacuum relay breakdown voltage. I
recently learned that some of these vacuum relays are not designed for hot
switching and some are. The ones designed for hot switching are characterized
as "ground isolated" in a Jennings catalog.
Hot switching in this case means the relay contacts are above ground by
several kv and are used to disconnect a load from a hv power supply while
current
is still flowing.
I learned the hard way that you can get a big flashover from the relay
contacts to the mounting flange and/or to the relay coil if you have the wrong
type relay in this kind of application.
You might ask: why would you want to switch while current is flowing? I am
working with some microwave traveling wave tubes that operate essentially class
A and current flows with or with rf being present. Even at hf class B or AB,
there would be some current flow while switching but fortunately the voltage
is not high enough to cause a problem. In my case, I was trying to switch
about 5kv when the flashover happened. A Jennings RJ1 and a Kilovac HC2 had
this problem in my case.
The Jennings catalog did not indicate the RJ1 to be a ground isolated design
and I have no data on the Kilovac unit.
I hope this saves someone a bit of grief.
73,
Gerald K5GW
In a message dated 4/7/2006 7:46:43 A.M. Central Daylight Time, r@somis.org
writes:
Gentlemen and others: We are out of surplus Kilovac HC-1s and Jennings
RJ-1A high-speed vacuum relays, but this week we received a shipment of
100, new, Kilovac/Gigavac relays. The price of the new relay is $76
each, and the p/n is 44.1. The measured, OC withstanding potential of
the new relays has so far been extraordinary, as in >2x the mfg's
rating.
Rich Measures, 805.386.3734, AG6K, www.somis.org
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