I think you have to provide a few more clues. Are you working on a particular machine? Usually a ring gear is a gear larger than some other gear, driven by a smaller pinion gear.
You could call the starter gear on an ICE a main ring gear (not usual), or a gear built as part of the outer shell of a gigantic rotary kiln (or something in between).
Under British Standard 7671 it would be a 32A MCCB and a loop of 2.5mm2 twin-and-earth cable that picks up an unlimited number of British Standard 1363 sockets over a floor area not exceeding 100m2.
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