I am designing a small Arduino-driven circuit to control a ~3/4 hp AC hoist motor. The hoist motor includes a starter-capacitor. The Arduino drives a transistor which in turn drives a power relay that switches the motor on and off. I am not an electrical engineer, so I'm using a Factor of Safety of 2 or higher throughout the circuit to avoid component damage/burnout.
The particular relay I had in mind is supposed to be capable of handling up to 30A sustained (more than 4 times the max-load current of my motor) at double the nominal operating voltage. My intent is to run two of them in series for safety (to handle one failed-closed relay) and for wear-leveling of the contacts.
Consulting an ampacity chart, it looks to me like I need 10AWG copper wire (about 5.3mm^2 conductor area) to handle 30A. But as you can see from the relay datasheet, the load pins are ridiculously tiny: each is roughly equivalent to 17AWG (1.6mm^2). Unfortunately Digikey does not carry a socket with solder cups or terminal lugs for this particular relay, and I'm having a very hard time soldering 10AWG wire to a 17AWG pin.
- How can the relay pins carry so much current with such a tiny conductor?
- Is 10AWG really the right size of wire to carry 7A AC with an inductive load?
- How should I go about wiring this relay to the rest of my circuit?