Show dictionary · Power & Electrical
Three-Phase Power
Also: 3-phase · 120/208
Three-phase power delivers electricity on three hot conductors whose voltages are offset 120 degrees from each other. In the common US event service (120/208 V wye), each leg gives 120 V to neutral while legs pair to 208 V, moving three times the power of a single phase over comparable copper.
In practice
Shows run three-phase because the loads demand it: a 400 A three-phase service carries what would take heroic single-phase copper. Distros split the legs into circuits, and balancing (spreading load evenly across the three) is the working discipline, since capacity is per leg and an unbalanced service wastes it.
The √3 in the power math (P = √3 × V × I × PF for line-to-line calculations) is the geometric consequence of the 120° offsets; the event power calculator handles it. European services deliver 230/400 V in the same wye arrangement, which is why international racks care so much about labeling.
How you’ll hear it
"The service is 200 A three-phase; audio takes leg one, lighting spreads across two and three."
Related resources
Part of the eventools.io Show Dictionary, a free glossary of live event production terminology.