I would run each motor leads in a separate conduit also because
1. Only one can fail. Much easier to fix. Admittedly if one fails then the whole machine goes down.
2. My lack of full understanding of VFD output problems ie spikes, harmonics etc. Seems to me putting more in one conduit will compound problems.
Re question about branch circuit protection
Technically each of 12 motor feeds from VFD is a separate branch (???).
Therefore the branch would need its own overcurrent device which is also able to interrupt a fault current ie short.
With 12 motors on one VFD it seems to be a good question. As suggested insertion of the overloads would be acting to provide overcurrent protection for the individual motors and would be connected to trip the VFD. If there is a major fault ie short circuit the VFD would trip on overcurrent.
BUT the VFD would provide protection at 12 X the "ideal" branch circuit rating.
Is this an adaptation of NEC tapping a feeder rule?
Below NEC articles address grouped motors
NEC 430.87, -53, -24 seem appropriate. Am I missing one. Dont see VFD in index.
Dan Bentler
Dan Bentler