I need to use a relay in order to do field sweeps with my electromagnet, which is hooked up to a couple very beefy monopolor power supply. (My magnet's impedance is ~2 Ohm, and I am putting ~40 Amps through it at maximum power).
Initially, I figured the Potter & Brumfield T92 Series Two-pole 30A PCB Relay would work for me.
A cursory glance at the contact data revealed:
- Rated Current: 30A
- Limited Continuous Current: 40A
- Limited Making Current: 40A
- Limited Breaking Current: 40A
I assumed I would be pushing the limits, but this relay is $13 and I had one laying around. However, then I looked at the contact ratings, and I saw, under the 'Load' header:
- 40A, 277VAC, resistive
- 30A, 120/277VAC, resistive
- 10A, 600VAC, general purpose
- 20A, 28VDC, resistive
Where I have italicised the rating that concerns me. Is this to say that I should not use this relay? Does anyone have any idea what kind of relay I should use? When I look at "power relays," they all seem to have just two contacts, rather than the eight that I would expect... Also, how do I tell if the relays are make-before-break or break-before-make? I know that the one I have now will work, only because I know someone else who is using it for the same thing...
Thank you for your help!