What is the difference between a DC power system and a UPS?

[DC power system vs UPS · rectifier vs UPS] A DC power system (rectifier plant) converts AC to DC, feeds DC loads directly, and floats a battery on the same bus, so if the AC fails, the battery simply continues to supply the DC bus with no transfer event. A UPS converts AC to DC and back to AC to feed AC loads, and involves a transfer when the mains fails. Where the equipment runs natively on DC, telecommunications, signalling, substation protection and control, most industrial instrumentation, a DC power system is simpler, more efficient and has fewer failure modes. Where the load is AC, a UPS is required. This is the highest-value definitional question in the whole hub, and no Australian competitor answers it.