If they are a little out of phase or the current dips more on one, the "slow" or "low" generator will do less work and the other will have to pickup the slack. If they are too far out of phase, bad things happen and the magic smoke gets let out.Awesome vid. The segment with the lightbulb next to the O-Scope was great!. Nice industrial gensets, and that dude knows some stuff! However, he did not say what happens if one of the motors has a hiccup, would the phase shift? Or if the motors don't have exactly equal power?
If a 'device' existed to combine the outputs of any 2 'normal' generators that could be a useful item if not so expensive. I suspect it would have to convert to DC, combine and invert back to AC.
Not exactly the same, but same concept using an incandescent bulb to run generators in parallel.