Here are many aspects which affect the selection of module. Totally single phase units are rarely available beyond 20 kVA, above this size it's usually necessary to use a 3 phase input for the rectifier, even where the inverter output is a single phase. Because 3 phase supply can deliver more electric power than one phase supply. 

When feeding this sort of system via a generator it's important to recollect that the bypass line is going to be single-phase, demanding a better current on one phase only. Larger units with three-phase input/output are more easily distributed across generators and may even be wont to feed single-phase loads, and with good load balancing, needn't be oversized.