Take a look at the 1-line diagram below. The diagram shows a layout of 3 single phase 120/240volt separate generators feeding one building with simple 2-pole transfer switches.
Would there be trouble with the generator electronics and a common neutral between all 3 units?
Is there any concern if standard 2-pole transfer switches are used and 1 gen-set were to loose a neutral or hot leg?
Should the set-up use transfer switches that break the ungrounded conductor making them separately derived?
I'll try going back to the start.
First question, no, because it isn't a common neutral in the sense that any one section of wire is common to the circuit of one generator and also to the circuit of the other generator under any normal or almost any fault condition.
Second question. No concern beyond freaks of nature. It would take some almost unimaginable fault combination to create a dangerous condition to personnel. You would be more likely to be walking under a power line and have it break and fall in to your hands, electrocuting you.
Third, you can, but then you would have to create a grounding electrode system, including building steel, for each of the three generators, and then think about it, the grounding system would actually have a similar interconnectivity as the neutrals you are concerned with.
Hope this helps given the confusion I have felt reading through our responses to you.
