[Amps] New vacuum relays

[R at contesting.com]

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
>>   
>>
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>  



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