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
>> ??
>>
>> _______________________________________________
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> ?
Rich Measures, 805.386.3734, AG6K, www.somis.org
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