Which statement best describes the meaning of the 1.73 factor in three-phase power calculations?

Which statement best describes the meaning of the 1.73 factor in three-phase power calculations?

• A. The ratio of line-to-line to line-to-neutral voltage
• B. The square root of 3
• C. A unit of measurement for kilowatts
• D. A fixed efficiency factor for three-phase systems

Answer: (B)

The 1.73 factor is the square root of 3, a geometric result that comes from the way three-phase voltages add as phasors. In a balanced system, the line-to-line voltage is √3 times the line-to-neutral (phase) voltage, so VL = √3 · VPH. That same √3 factor shows up in three-phase power calculations, for example P3φ = √3 · VL · IL · cosφ. It isn’t a unit or an efficiency factor; it’s the conversion between line quantities and phase quantities that arises from the 120° separation of the voltages.

The 1.73 factor is the square root of 3, a geometric result that comes from the way three-phase voltages add as phasors. In a balanced system, the line-to-line voltage is √3 times the line-to-neutral (phase) voltage, so VL = √3 · VPH. That same √3 factor shows up in three-phase power calculations, for example P3φ = √3 · VL · IL · cosφ. It isn’t a unit or an efficiency factor; it’s the conversion between line quantities and phase quantities that arises from the 120° separation of the voltages.