Single Phase vs Three Phase
Single-phase and three-phase describe how many alternating-current waveforms supply a circuit. The difference changes how voltage, current, and power are calculated.
Single-phase power
Single-phase circuits use one AC waveform delivered over two conductors. Most residential and small commercial loads are single-phase.
Three-phase power
Three-phase circuits use three AC waveforms, each offset by 120 degrees, delivered over three (or four, with a neutral) conductors. Three-phase is common in industrial and larger commercial settings because it delivers more power per conductor and runs more efficiently.
Why the √3 factor
Because the three phases are offset rather than aligned, three-phase power calculations include a factor of √3 (approximately 1.732) to correctly account for the relationship between line voltage, line current, and total power.