Non-breaking electrical contacts

[BobM2]

I'm designing a relay that needs contacts for reversing a motor. The starting and stopping of the current is done via a triac so the relay contacts do not have to start or break current. The current will range from 10 - 70 amps. I'm thinking I can do with simple silver plated copper. Any thoughts?

 

[nbucska]

Designing a relay is a specialized job -- why don't you just buy one ?

What is the voltage you want to switch? AC or DC ?

<nbucska@pcperipherals.com>

 

[BobM2]

We're using a T90 series right now that works o.k. for most of our customers. The problem I have with it is that the NC contact doesn't have quite enough force. Bending the spring to increase the force fixes the problem but of course increases the voltage needed to close the NO contact. I can't find anything else that will fit onto our board. I was hoping to avoid buying large quantities of silver cad oxide over copper contacts because we won't use enough of them.

 

[nbucska]

Can't U use an off-board relay ?

<nbucska@pcperipherals.com>

 

[melone]

Or an H-bridge configuration of FET's?

 

[BobM2]

My enclosure is too small for off-board relays. The H configuration is something I will look at for the next generation. Right now I have to fix a problem using the existing aluminum housing (no surfaces to mount the FETs for heat sinking). I have found a contact manufacturer that has given me a quote on contacts nearly identical to what we are using. I've got the magnetic circuit designed and the springs figured out. I think I have a fix. Thanks for the advice.