[FrankJ]

The idea that the fuse is there to protect the wire is really a building code & utility wiring kind of thing. On the equipment level (robot) your fuses or other current protection should be there to protect the equipment in addition to the wiring.

Current rating of relays have two components. 1) How much current can you have & reliably open the contact. 2) The need to have a very high number cycles until failure.