Reading in the Jennings catalog: "RJ1H-26s is similar to RJ1A except
designed specifically for DC hot load switching". In my mind, this implies that
the
RJ1A is NOT designed for hot switching.
The description for the RJ1A omits the words "ground isolated" further
implying that it is NOT designed for hot switching.
The catalog describes hot switching as having the relay contacts located
between the power source and the load, just like we would normally connect
things. Using a vacuum relay in this manner requires a "ground isolated style
construction".
The catalog goes on the show connecting the relay contacts between the cold
end of the load and ground, with the power supply connected permanently to the
hot end of the load. This arrangement does not require ground isolated
contacts and the RJ1A , as well as many other models are apparently designed
to be
connected this way.
The catalog warns of the possibility of flashovers when relays not designed
for ground isolated operation are operated with the contacts connected between
the power source and load. This is exactly what happened to my two RJ1A and
Kilovac HC2 relays when they were wrongly connected between the source
voltage and load.
The relays Rich is offering may well be the ground isolated type and if so,
are a good buy. The 9kv standoff voltage strongly suggests they may well be
ground isolated.
73,
Gerald K5GW
In a message dated 4/7/2006 11:54:04 P.M. Central Daylight Time,
r@somis.org writes:
On Apr 7, 2006, at 8:16 AM, TexasRF@aol.com wrote:
>
> 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.
At 1600w PEP, there is about 400v-pk from the contacts to ground. At
9000VDC, from the flange to the contacts, the new Kilovac/Gigavac
relays measure 0uA of leakage.
>
> 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.
As I recall, hot-switch rated relays have tungsten contacts while
RF-rated ones have copper contacts and are speced: no hot switching.
>
> 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.
Hot switching can occur on a grounded contact as easily as on a
floating contact.
>
> 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.
The Jennings RJ-1A is ground isolated.
>
> 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
>>
>>
>> _______________________________________________
>> Amps mailing list
>> Amps@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>
Rich Measures, 805.386.3734, AG6K, www.somis.org
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