Single or Three phase UPS?
There are many aspects which affect the choice of module. Totally single phase units are rarely available beyond 20 kVA, above this size it is usually necessary to use a three phase input for the rectifier, even where the inverter output is single phase. When feeding this type of system via a generator it is important to remember that the bypass line will be single phase, demanding a higher current on one phase only. Larger units with three phase input/output are more easily distributed across generators and can also be used to feed single phase loads, and with good load balancing, need not be oversized