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CRITICAL POWER CONTINUITY

Generator + UPS Transfer & Ride-Through Planner

Turn utility failure → UPS ride-through → generator start/retry → ATS transfer → stable generator supply into a measurable continuity timeline.

Utility failureUPS ride-throughGenerator startATS transfer
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Engineering inputs

Set the engineering assumptions and design parameters.

Inputs & timing assumptions

Engineering boundary

Use measured/vendor UPS runtime at the actual load. Generator transient response, ATS logic, UPS input acceptance and protection coordination still require vendor review and commissioning tests.

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Engineering results

Review calculated capacity, limits and design checks.

Engineering results

Transfer-to-stable window
Required UPS ride-through incl. reserve
UPS ride-through margin
UPS loading
Generator usable capacity after redundancy
Generator design loading
Latest safe transfer time
Overall result

Capacity checks

Transfer timeline

Warnings

How to use this planner

Start with the critical load that the UPS must carry. Enter UPS usable kW and autonomy at that load, then model generator capacity after redundancy and every timing element from utility loss to stable generator supply.

Why timing matters

A system may have enough UPS and generator kW yet still fail continuity if start retries, warm-up or ATS transfer exceed battery ride-through. The planner therefore checks time and power in parallel.

Engineering references

Schneider Electric Critical Power · Cummins Generator Systems

Content reviewed: 2026-09-10

FAQ

Why is UPS runtime entered at the current critical load?

Battery autonomy is nonlinear and depends on battery chemistry, age, temperature, UPS efficiency and discharge rate. Use vendor runtime data or the dedicated UPS calculator rather than assuming nameplate Ah converts linearly.

What does the transfer window include?

The model includes outage detection, start delay, crank attempts, retry intervals, generator warm-up, ATS transfer and a stabilization interval before declaring the load stable on generator.

Why add a ride-through reserve?

A reserve protects against timing variation, relay delays, battery uncertainty and slower-than-expected generator stabilization. It is an engineering margin, not a substitute for commissioning tests.

Does passing generator kW guarantee the transfer will succeed?

No. Generator transient voltage/frequency response, UPS input compatibility, harmonics, inrush and manufacturer step-load limits must also be checked.

Can this replace an ATS/UPS/generator commissioning test?

No. It is a planning and screening tool. Final acceptance requires site testing of actual control logic, start retries, transfer timing, UPS behavior and protection coordination.

ENGINEERING WORKFLOW

Continue the engineering workflow

Current workflowData Center Critical Power & Cooling Workflow

Move from rack load through UPS protection, generator/ATS ride-through, precision cooling, airflow containment and facility PUE as one critical-infrastructure planning sequence.

Step 3 of 6
PreviousUPS Capacity & Battery Backup Runtime CalculatorSize UPS kW/kVA capacity, modular redundancy, battery autonomy, aging/temperature margin, recharge demand and bypass current.NextData Center Cooling Load & Precision AC Capacity CalculatorCalculate data-center sensible heat, N+1 precision cooling capacity, BTU/h, refrigeration tons and airflow from IT and facility loads.

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