Three-phase power
Three alternating waveforms working in a coordinated rhythm.
Three balanced sinusoidal waveforms, separated by one-third of a cycle.
A balanced three-phase supply has three sinusoidal voltages of the same frequency and magnitude, separated by one-third of a cycle, or 120 degrees. Three-phase systems are widely used for generation, transmission, and large electrical loads.
Three phases, one repeating system
The phase voltages of an ideal balanced three-phase supply have equal magnitudes and frequency, separated in time by 120 electrical degrees. They reach their peaks in sequence. The colors in a diagram distinguish phases; they are not universal wire-color rules.
With balanced sinusoidal voltages and currents, total instantaneous three-phase power is constant even though each phase varies. Three-phase supplies also produce rotating magnetic fields for motors. Real distribution networks serve uneven single-phase loads and need not remain perfectly balanced.
Why it matters
Three-phase connections are a basic building block of utility networks and industrial electricity supplies.