Required UPS kVA rating from critical load, margin, and redundancy configuration, plus an approximate battery energy/Ah figure for the stated backup time. For a full IEEE 485 duty-cycle battery design, see the Battery & DC System Sizing calculator. Fully free — no subscriber gate.
IEEE 485-referenced, N-unit redundancy
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For preliminary engineering use only — always verify results against project-specific standards and a qualified engineer's review before use in a real design.
With N total UPS frames installed, any (N−1) must be able to carry the full critical load alone (the same convention as the Transformer Sizer, commonly called “N+1” in UPS terminology) — N=2 sizes each frame for 100% of the load.