[Amps] New vacuum relays

[TexasRF at aol.com]

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 at somis.org writes:


On  Apr 7, 2006, at 8:16 AM, TexasRF at 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 at 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 at contesting.com
>>  http://lists.contesting.com/mailman/listinfo/amps
>  



Rich Measures, 805.386.3734, AG6K,  www.somis.org

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