{
  "schemaVersion": 1,
  "id": "atlas-lesson-ups",
  "title": "Uninterruptible power supply and backup chain",
  "category": "learning",
  "format": "Atlas lesson",
  "description": "Maintains power continuity across disturbances and transitions to other supply sources.",
  "canonicalUrl": "https://semiaifoundry.com/learn/atlas/ups/",
  "publishedDate": null,
  "revisionDate": "2026-10-07",
  "author": null,
  "topic": "Electrical infrastructure",
  "series": null,
  "license": null,
  "rightsUrl": "https://semiaifoundry.com/ai-atlas/licenses.html",
  "version": "1.3.0",
  "status": "Published educational lesson",
  "evidenceScope": "This is a constant-load energy estimate, not battery sizing or a vendor runtime guarantee. Discharge curves, reserve, temperature, aging, transient load and power-delivery limits require configuration-specific data.",
  "contentCoverage": "published-lesson",
  "artifactUrl": "https://semiaifoundry.com/ai-atlas/lesson-data/ups-adaf1cf2e0bd26f2.json",
  "interactiveUrl": "https://semiaifoundry.com/ai-atlas/#ups",
  "related": [],
  "supersedes": [],
  "supersededBy": [],
  "contentHash": "bbd37ff62f0b019392742484aefce04a62f358041593436a67ec5bf7935a0a5c",
  "contentLength": 5196,
  "jsonUrl": "https://semiaifoundry.com/agents/publications/atlas-lesson-ups.json",
  "markdownUrl": "https://semiaifoundry.com/agents/publications/atlas-lesson-ups.md",
  "sections": [
    {
      "id": "section-1",
      "title": "Uninterruptible power supply and backup chain",
      "start": 42,
      "end": 401
    },
    {
      "id": "section-2",
      "title": "The mechanism",
      "start": 401,
      "end": 1424
    },
    {
      "id": "section-3",
      "title": "Science and assumptions",
      "start": 1424,
      "end": 1452
    },
    {
      "id": "section-4",
      "title": "Finite backup duration",
      "start": 1452,
      "end": 2433
    },
    {
      "id": "section-5",
      "title": "Engineering example",
      "start": 2433,
      "end": 2656
    },
    {
      "id": "section-6",
      "title": "Distinctions and tradeoffs",
      "start": 2656,
      "end": 3016
    },
    {
      "id": "section-7",
      "title": "Specifications and interfaces",
      "start": 3016,
      "end": 3302
    },
    {
      "id": "section-8",
      "title": "Interfaces",
      "start": 3302,
      "end": 3451
    },
    {
      "id": "section-9",
      "title": "Check your understanding",
      "start": 3451,
      "end": 3480
    },
    {
      "id": "section-10",
      "title": "What chiefly determines backup duration?",
      "start": 3480,
      "end": 3843
    },
    {
      "id": "section-11",
      "title": "Evidence and scope",
      "start": 3843,
      "end": 4227
    },
    {
      "id": "section-12",
      "title": "Sources",
      "start": 4227,
      "end": 4759
    },
    {
      "id": "section-13",
      "title": "Continue exploring",
      "start": 4759,
      "end": 4782
    },
    {
      "id": "section-14",
      "title": "Foundations",
      "start": 4782,
      "end": 4888
    },
    {
      "id": "section-15",
      "title": "Related lessons",
      "start": 4888,
      "end": 5196
    }
  ],
  "citations": [
    {
      "title": "Explore in Atlas",
      "url": "https://semiaifoundry.com/ai-atlas/#ups"
    },
    {
      "title": "Eaton — UPS and Data-Center Infrastructure",
      "url": "https://www.eaton.com/us/en-us/markets/data-centers/data-center-infrastructure-overview.html"
    },
    {
      "title": "Eaton — UPS Bridging Generator Startup",
      "url": "https://www.eaton.com/us/en-us/catalog/backup-power-ups-surge-it-power-distribution/eaton-9355-ups/data-center-solutions-for-continuous-uptime.html"
    },
    {
      "title": "Published lesson data",
      "url": "https://semiaifoundry.com/ai-atlas/lesson-data/ups-adaf1cf2e0bd26f2.json"
    },
    {
      "title": "Atlas releases and licensing",
      "url": "https://semiaifoundry.com/ai-atlas/licenses.html"
    },
    {
      "title": "Power supply and power shelf",
      "url": "https://semiaifoundry.com/learn/atlas/power-supply/"
    },
    {
      "title": "Rack power shelf and DC busbar",
      "url": "https://semiaifoundry.com/learn/atlas/power-shelf/"
    },
    {
      "title": "Distributed checkpoint and recovery state",
      "url": "https://semiaifoundry.com/learn/atlas/checkpoint/"
    },
    {
      "title": "Integrated accelerator rack: GB200 NVL72 example",
      "url": "https://semiaifoundry.com/learn/atlas/rack/"
    }
  ],
  "recordHash": "4e4f477536e88faf6a05e626a762fdcc53366d8b02dbb21b3429b0049e731c67",
  "contentFormat": "text/markdown",
  "content": "Electrical infrastructure · Atlas v1.3.0\n\n# Uninterruptible power supply and backup chain\n\nMaintains power continuity across disturbances and transitions to other supply sources.\n\n[Explore in Atlas](https://semiaifoundry.com/ai-atlas/#ups)Room-scale power infrastructure; conceptual supply paths\n\nLearning objectiveEstimate an ideal backup runtime from usable energy, conversion efficiency and load.\n\n## The mechanism\n\nAn uninterruptible power supply supports critical loads when incoming electrical supply is disturbed. Stored energy and power electronics can bridge a gap until a generator or other source becomes available, or permit controlled shutdown according to the facility design. Runtime is finite and depends on load, stored energy, and equipment configuration. The atlas traces normal supply and backup paths separately, making the transition understandable without implying that a battery can power a data center indefinitely. Modern power-management arrangements may also help handle changing loads, but capabilities vary. UPS systems belong to a wider chain of distribution, protection, generation, and monitoring that must deliver reliable power to the rack shelves downstream.\n\n1.  Supply critical loads during normal operation.\n2.  Use the supported stored-energy path when supply is disturbed.\n3.  Bridge to another source or a controlled operational response before the available runtime is exhausted.\n\n## Science and assumptions\n\n### Finite backup duration\n\n$$\nt_{\\mathrm{runtime}}\\approx\\frac{E_{\\mathrm{usable}}\\eta}{P_{\\mathrm{load}}}\n$$\n\nBackup runtime is approximately usable stored energy times remaining conversion efficiency divided by load power.\n\nIf usable energy is already measured at the load boundary, do not apply the same conversion loss again; set the remaining efficiency to one.\n\nSymbols and units\n\nt\\_runtime\n\nEstimated backup runtime\n\nh\n\nE\\_usable\n\nUsable stored energy before the separately modeled output conversion loss\n\nWh\n\nη\n\nRemaining conversion efficiency from that energy boundary to load\n\nfraction\n\nP\\_load\n\nConstant supported load power\n\nW\n\nStored usable energy divided by the supported load gives a first duration estimate. Conversion losses and runtime-dependent battery behavior affect the actual result.\n\nAssumptions Constant load and effective usable energy approximation; vendor discharge curves, reserve limits, temperature, and aging are required for engineering sizing.\n\n## Engineering example\n\nSynthetic UPS: 100 kWh usable stored energy, 90% conversion efficiency and constant 300 kW load give 100 × 0.9/300 = 0.3 h = 18 min. A 600 kW load would give 9 min under the same ideal assumptions.\n\n## Distinctions and tradeoffs\n\nA UPS power rating in kW does not specify its energy capacity or runtime in hours.\n\nMore backup duration improves endurance. Stored energy, conversion capacity, and maintenance require resources.\n\nLong AI jobs lose progress when power disappears. Continuity and checkpoints address complementary parts of that recovery problem.\n\n## Specifications and interfaces\n\nPurpose\n\nPower continuity\n\nSupports disturbances and source transitions.\n\nRuntime\n\nLoad- and configuration-dependent\n\nNo universal minutes-of-backup specification.\n\nPower vs energy\n\nkW vs kWh\n\nDelivery rate and stored amount are different quantities.\n\n### Interfaces\n\nUtility or backup source Input\n\nElectrical supply\n\nCritical distribution Output\n\nConditioned or supported power to downstream loads\n\n## Check your understanding\n\n### What chiefly determines backup duration?\n\n1.  The color of battery cabinets\n2.  Stored usable energy and the supported load\n3.  The number of training tokens already processed\n\nAnswer and reasoning\n\nStored usable energy and the supported load\n\nEnergy divided by load gives basic duration intuition, with equipment limits and losses affecting actual runtime.\n\n## Evidence and scope\n\nThis is a constant-load energy estimate, not battery sizing or a vendor runtime guarantee. Discharge curves, reserve, temperature, aging, transient load and power-delivery limits require configuration-specific data.\n\nNo current calculator directly models this lesson’s main mechanism. Use the library for related bounds while retaining their stated omissions.\n\n## Sources\n\n-   [Eaton — UPS and Data-Center Infrastructure](https://www.eaton.com/us/en-us/markets/data-centers/data-center-infrastructure-overview.html)\n-   [Eaton — UPS Bridging Generator Startup](https://www.eaton.com/us/en-us/catalog/backup-power-ups-surge-it-power-distribution/eaton-9355-ups/data-center-solutions-for-continuous-uptime.html)\n\n[Published lesson data](https://semiaifoundry.com/ai-atlas/lesson-data/ups-adaf1cf2e0bd26f2.json) · [Atlas releases and licensing](https://semiaifoundry.com/ai-atlas/licenses.html)\n\n## Continue exploring\n\n### Foundations\n\n-   [Power supply and power shelf](https://semiaifoundry.com/learn/atlas/power-supply/)\n\n### Related lessons\n\n-   [Rack power shelf and DC busbar](https://semiaifoundry.com/learn/atlas/power-shelf/)\n-   [Distributed checkpoint and recovery state](https://semiaifoundry.com/learn/atlas/checkpoint/)\n-   [Integrated accelerator rack: GB200 NVL72 example](https://semiaifoundry.com/learn/atlas/rack/)"
}