Quiz: AI Data Center Electrical Infrastructure (Part 4)

10 questions from Part 4 of the guide. Score instantly; every explanation links to the chapter that derives the answer.

How many facility conversion stages does the guide's stated conventional AC chain carry before the rack-power redesign?
91534
A modern AI server PSU (active front end) draws current at what distortion level — and what does that imply?
~15% THD — same as legacy servers<5% THD — the harmonic problem largely disappears, replaced by synchronized load transients~30% THD — evaluate the measured spectrum, thermal capacity/K-factor, and harmonic-current mitigationTHD is no longer measurable at these power levels
Why does the 13th harmonic matter so much more than the 5th for transformer heating?
it carries more currentit trips protective relays firstit resonates with the grid frequencyeddy losses scale with h² — the 13th heats ~169× the fundamental vs ~25× for the 5th
Moving row distribution from 208 V to 415 V three-phase does what to rack power per ampere?
No change — voltage doesn't matterHalves itRoughly doubles itQuadruples it
NVIDIA has quoted both '~85%' and '+157%' more power through the same copper for 800 VDC vs 415 VAC. Why do both figures exist?
They compare different conductor topologies — the +157% counts a three-wire DC feed (POS/RTN/PE) against four-conductor AC; the comparison basis changed, not the physicsThey refer to different rack generationsThe +157% superseded the ~85% after a hardware revisionOne is marketing and one is measured
A rack can still be served by either a conventional AC chain or a rack-scale DC architecture. What decides when the project should cross over?
the rack vendor's preferred labelthe highest voltage the utility offersa route-specific calculation of deliverable current, protection frames, conductor count and loss, conversion efficiency, and service constraintsa universal rack-power threshold
The solid-state transformer (SST) matters because it…
removes the transformer lead-time problemconverts 13.2 kVAC → 800 VDC in one ~98%-efficient step, collapsing the conversion chain (~87% utility-to-VRM)eliminates the need for a substationis cheaper than a conventional transformer today
What ampacity are AI halls now specifying for overhead busway, versus the legacy standard?
400 A — unchanged800–1,000 A, up from a legacy 400 A200 A, down from 400 A5,000 A trunk lines
The UPS role is being redefined in AI halls from 'ride through until the generator starts' to…
absorbing the cluster's own MW-scale load transients at optimizer cadencelong-duration storage for demand response onlypure surge suppressionit is being removed entirely
What does choosing 48 V for an OCP in-rack bus establish — and what does it not establish?
it stays within the stated <60 V DC SELV voltage boundary, but does not waive task-specific arc, short-circuit, stored-energy, or conductive-tool controls48 V minimizes copper masshigher voltages don't exist in DC partsit matches telecom heritage only

Check your understanding: Electrical & Energy Infrastructure