{"id":"rack-power-conversion","level":"infrastructure","name":"Rack power conversion and distribution","shortName":"Rack power conversion and distribution","role":"Moves electrical energy from facility supply through conversion stages to low-voltage chip rails.","description":"Facility electricity reaches a rack through distribution equipment and power supplies, then travels through busbars, board connections and local voltage regulators. Each stage has a voltage, current, capacity and conversion efficiency. The DGX GB reference describes power shelves converting AC to nominal rack DC, but other racks use different arrangements. Nameplate capacity includes redundancy and does not equal measured consumption. At the chip, low voltage implies high current for a given power, increasing the importance of short, low-resistance paths. A power value needs a measurement location before it can constrain compute capacity: input conversion losses and downstream IT demand belong to different boundaries.","specs":[{"label":"Power boundary","value":"Facility input, rack input or chip rail","context":"Do not compare values from different locations as equivalent."},{"label":"Capacity versus draw","value":"Installed PSU rating versus measured load","context":"Redundant supplies provide resilience and headroom, not automatic consumption."}],"interfaces":[{"name":"Facility electrical feed","direction":"in","signal":"AC power under distribution and redundancy constraints"},{"name":"Chip voltage rails","direction":"out","signal":"Regulated DC with conversion losses and transient limits"}],"tradeoff":"Higher distribution voltage reduces current for a given power, while conversion close to the chip adds efficiency and thermal requirements.","whyAI":"Accelerator deployment needs suitable distribution and regulation, not only enough annual electricity or enough power-supply labels.","related":["power-supply","power-shelf","voltage-regulator","power-integrity-budget"],"sources":[{"title":"NVIDIA DGX GB Rack Scale Systems: Hardware","url":"https://docs.nvidia.com/dgx/dgxgb200-user-guide/hardware.html"}],"scale":"Chip voltage rails to facility heat rejection","kind":"architecture","branch":"Data-center physical systems","subbranch":"Electricity and heat transport","mechanism":["Mark every conversion stage and its electrical measurement boundary.","Calculate current from power and voltage for the path being evaluated.","Apply stage efficiency once and account for the associated local heat.","Check redundancy and operating headroom separately from normal workload draw.","Verify final rail quality and rack acceptance under representative load changes."],"misconception":"Adding PSU nameplate ratings does not establish typical rack power, especially when supplies provide redundant capacity.","check":{"question":"Why does a low-voltage rail require large current at high power?","options":["Low voltage creates energy","Current and voltage are the same quantity","Power equals voltage times current"],"answer":2,"explanation":"For fixed delivered power, reducing voltage increases the required current and its associated distribution challenges."},"science":[{"title":"Conversion accounting","equation":"Pout = ηPin; I = P/V","explanation":"Power is watts, η dimensionless efficiency, current amperes and voltage volts.","assumptions":"Steady average values at a specified stage; AC power factor and transient behavior need additional treatment."}],"prerequisites":["power-supply","voltage-regulator"],"learningObjective":"Distinguish conversion losses, redundancy and measured consumption.","workstream":"W09","visualFamily":"signal-power","engineeringExample":"Synthetic regulator: supplying 1 kW at 1 V requires 1,000 A on that rail. At 90% efficiency its input is about 1.11 kW, leaving about 111 W of conversion loss to remove.","evidenceNotes":"The numeric example is not a product rail specification. Documented rack DC and approximate rack power are source-scoped in the claims ledger.","labId":"library","scope":"No current calculator directly models this lesson’s main mechanism. Use the library for related bounds while retaining their stated omissions.","investigationId":"manufacturing","labScope":"No current calculator directly models this lesson’s main mechanism. Use the library for related bounds while retaining their stated omissions."}