Power
Three-Phase Power
Delivers three alternating current waveforms 120° apart on three conductors — more efficient power delivery for high-density equipment, and the standard for data center electrical distribution.
Where single-phase power uses one AC waveform, three-phase uses three waveforms spaced 120° apart. The combined effect is more consistent power delivery (the waveforms overlap, so total power never drops to zero as it does in single-phase) and more efficient use of copper conductors.
For data centers and server rooms, three-phase power offers two primary advantages:
Higher power density — a 30A three-phase circuit at 208V (three-phase 208/120V is the North American data center standard) delivers ~10.8kW, compared to ~2.4kW for a 20A single-phase circuit. This allows far more equipment per circuit and per rack.
Balanced loading — PDUs designed for three-phase input distribute load across all three phases, keeping the electrical system balanced. This matters to the facility and utility.
In a three-phase 208/120V system:
- Line-to-neutral = 120V (standard outlets from branch circuits)
- Line-to-line = 208V (dual-corded servers, three-phase PDUs)
Most enterprise servers and storage equipment support wide-range input from 100–240V, so they'll run on either 120V or 208V feeds. At 208V, a server drawing 1,000W only pulls ~4.8A rather than ~8.3A at 120V — lower current means less heat in wiring and longer-lasting connections.