Three-phase power

Three-phase power is AC delivered on three conductors whose voltages are offset by 120 degrees. Common rack feeds are 208 V delta and 400 or 415 V wye. A three-phase rack PDU typically splits that feed into single-phase 200 to 240 V circuits for its outlets. On Schneider's AP8868, bank 1 runs across phases 1 and 2, bank 2 across phases 2 and 3, and bank 3 across phases 1 and 3.

Schneider's APC FAQ computes power at 208 V as three-phase current times voltage times the square root of 3, after the 80 percent continuous-load derating UL requires. The APC AP8866 is rated 17.2 kW at 208 V on a 60 A IEC 60309 3P plus PE input. NVIDIA's DGX SuperPOD guide lists 21.8 kW for a 415 V, 32 A three-phase wye circuit with no breaker derating and names 415 VAC, 32 A, N+1 as its preferred feed. It sizes each circuit for half the rack's peak, 20.4 kW for four DGX H100 systems.

Size the circuit from the derated figure, and read the PDU's kW rating from its datasheet. Banks share phases, so bank loads cannot simply be added to find the current on one phase.

Sources

Last verified October 30, 2026.