[TowerTalk] Fwd: Fwd: X99KP 12VDC RELAY FOR AMERITRON REMOTE ANTENNASWITCHES

[hanslg at aol.com]

Obviously, if any of the contacts weld together, that's it. I know that there are problems paralleling diodes but I don't know if, and don't believe, the situation is the same for relays. If you don't switch under power, which you normally don't do with antenna relays, I believe you, at least almost, double the current capacity by doubling the number of connectors. You have to be careful how you parallel the connectors, same length,same inductance etc. You might even be able to control the current sharing with the "right" lay-out. The voltage capacity is not changed though, and I would trust putting several contacts in series.

Hans - N2JFS


 

 

-----Original Message-----
From: jimlux <jimlux at earthlink.net>
To: hanslg at aol.com
Cc: towertalk at contesting.com
Sent: Tue, Sep 28, 2010 4:33 pm
Subject: Re: [TowerTalk] Fwd: X99KP 12VDC RELAY FOR AMERITRON REMOTE ANTENNASWITCHES


hanslg at aol.com wrote: 
>  LM Ericsson, Sweden (the old telephone manufacturer) had a patent many years ago regarding double contacts in relays. They showed that the reliability of a relay was major increased when you had two relay contacts in parallel. I believe you still find a term for this, just can't remember what. 
> > Hans - N2JFS 
> >  
It kind of depends on what you're trying to achieve. 
Paralleling contacts to improve "reliability" is one thing. 
paralleling contacts to improve current carrying is another 
Paralleling contacts to improve current breaking capability is yet another. 
 
There's a fairly common scheme using 4 SPST relays to implement a "any single relay can fail, and you can still make or break the circuit with the remaining 3" using a "all switch together" scheme. 
 
Likewise, there's a scheme using 2 SPDT relays that will tolerate a single failure (think of 3-way light switches at home), but it requires recognizing that the failure has occurred.