⚡ DC Failure Scenario & Equipment Sizing Tool
Power String Failure Analysis — UPS, Generator & Transformer Sizing
🏗️ Topology
Combined: IT and mechanical loads share the same power strings. This is the existing sizing methodology.
📊 System Parameters
STEP 1 Rack Row IT Loads
Define the kW load for each rack row. Default is uniform distribution.
| Row | Load (kW) | Racks | Feed Type |
|---|
STEP 2 Busbar Distribution & String Allocation
Dual: Each row fed by 2 busbars (50/50 split). On failure, surviving busbar takes 100%.
🔧 Other Loads Per String (Non-IT, fixed)
Mechanical and other fixed loads per string. Do NOT redistribute on failure.
| String | Chiller Electrical Load (kW) | Misc (kW) | Total |
|---|
🌀 Fan Wall Units
Fan wall units are structured mech UPS loads. In normal operation, the full unit load sits on the primary string. On primary string failure, the full load transfers to the secondary string.
| Unit | Load (kW) | Primary String | Secondary String |
|---|
🔋 Mech UPS Loads Per String
Other dedicated mechanical UPS output loads per string, separate from fan wall units.
| String | Other Mech UPS Load (kW) |
|---|
🧾 Executive Summary
📘 Assumptions & Methodology
Show calculation assumptions
- UPS sizing can be configured as either IT-only UPS with separate mechanical UPS reporting, or combined IT + mech UPS where the entered Mech UPS load is included in the main UPS sizing basis.
- Mechanical / cooling / miscellaneous loads do not redistribute during failure scenarios.
- UPS input power is calculated from UPS output plus configured charging and UPS losses.
- Generator sizing is based on worst-case surviving string demand with distribution losses first applied to UPS output, then UPS charging and losses applied to that adjusted UPS demand, then fixed non-IT loads added, then a further distribution loss allowance applied to the combined total before conversion by entered power factor.
- In separate UPS mode, the tool also reports mechanical UPS output and input from the entered Mech UPS loads and Fan Wall units for visibility, while generator sizing still uses the combined load basis.
- Transformer sizing is selected from the entered transformer rating list using the calculated generator apparent power.
- Dual mode assumes all racks are dual-connected across A/B, with each string carrying 50% of every rack load in normal operation and the survivor taking 100% on failure.
- Triple mode assumes the first rack half is dual-connected across A/C and the second half across B/C, with each connected pair sharing 50/50 in normal operation.
- Quad mode assumes two independent paired paths (A/B and C/D), each redistributing only within its pair.
- Quint mode assumes rack groups are dual-connected across A/E, B/E, C/E and D/E, with each connected pair sharing 50/50 in normal operation.
- Hex mode uses 6 strings with dual catchers (E and F) and always applies Quad (4S) feed. Left half of racks are quad-connected across A/B/E/F; right half across C/D/E/F. Each connected string carries 25% in normal. On failure of any one string, the surviving 3 feeds in that half take 33.3% each.
- Rack Feed Types: Dual — 2 feeds from assigned strings (default). Quad (2S) — 4 feeds from the same 2 assigned strings (physical redundancy, no calculation change). Quad (4S) — 4 feeds from 4 separate strings; in Quad mode this changes the calculation to 25% per string in normal, with the remaining 3 strings each taking 33.3% on failure. In other modes Quad (4S) behaves like Quad (2S) as racks connect to ≤2 distinct strings.
- Validation warnings are advisory checks only and currently use these thresholds:
- Normal IT load imbalance: moderate warning above 5%; high warning above 10%.
- Governing failure uplift: material warning above 20% over normal IT load on the affected surviving string; severe warning above 40%.
- Generator / UPS / Transformer power factors: warning when any entered PF is below 0.80 or above 1.00.
- UPS charging allowance: warning when above 8%.
- UPS loss allowance: warning when above 8%.
- Distribution loss allowance: advisory warning when above 5%.
- Transformer ratings: warning when no valid transformer ratings can be parsed from the input list.
- Duplicate feed selections: warning when the same string is assigned more than once within a single row definition.
📊 Row-Level Normal Distribution
IT load contribution from each row to each string under normal operation (rack-based physical split).
📊 Normal Operation Summary
| String | IT Load (kW) | Other Load (kW) | IT UPS Output (kW) | IT UPS Input (kW) | Mech UPS Output (kW) | Mech UPS Input (kW) | Gen Load (kW) | Gen (kVA) |
|---|
⚡ Failure Scenario Matrix — UPS Output (kW)
UPS output on each surviving string per failure. "—" = failed string.
🔧 Equipment Sizing
| String | Worst UPS Out (kW) | UPS Input (kW) | UPS (kVA) | Gen (kW) | Gen (kVA) | Transformer Calc (kVA) | Transformer Std (kVA) | Scenario |
|---|
🔄 Multi-Scenario Comparison
Current configuration is Scenario 0 (baseline). Export a template for additional scenarios, fill in different row loads, then import to compare all results side by side.