I think you finally just got a motor that was actually strong enough that you couldn't bog it down. So far as I know, nobody's making (or has ever made) a motor (for buffing) that has any sort of auto-slowdown function. Never even heard of such a thing, and I've been tweaking jewelry equipment for....a while.
That said, I definitely second Jo's warning about long hair. We had a 220V 3Ph standing buffer in my undergrad shop. Spinning 18" wheels. Woman with long hair went in there right before a crit, "just to touch something up".....
(Famous last words. Almost literally in this case.) Yeah. Didn't kill her, but did create an unholy mess, that ended up with me on a stepstool trying to get blood off the ceiling. Do NOT take those things for granted. That's when they bite.
Also, don't ever buff loose chain. Wrap it around a baseball bat, or some other large diameter hunk of hardwood. MUCH safer.