Three-phase power commonly increases power capability relative to increased conductors; what is the stated percentage?

Three-phase power commonly increases power capability relative to increased conductors; what is the stated percentage?

• A. 50%
• B. 100%
• C. 73%
• D. 0%

Answer: (C)

Three-phase power can carry more real power for the same conductor size because the three voltages are offset by 120 degrees and the power contributions add up more effectively. For a balanced load, the total power in a three-phase system is P_total = √3 × V_line × I_line × PF. In a comparable single-phase setup, the power is P_single = V_line × I_line × PF. The ratio of three-phase to single-phase power is √3, which is about 1.732. That means roughly a 73% increase in power capability. For example, with the same line voltage and current, three-phase delivers about 83 kW instead of 48 kW (at PF = 1) when V_line = 480 V and I_line = 100 A. So the stated percentage is about 73%.

Three-phase power can carry more real power for the same conductor size because the three voltages are offset by 120 degrees and the power contributions add up more effectively. For a balanced load, the total power in a three-phase system is P_total = √3 × V_line × I_line × PF. In a comparable single-phase setup, the power is P_single = V_line × I_line × PF. The ratio of three-phase to single-phase power is √3, which is about 1.732. That means roughly a 73% increase in power capability. For example, with the same line voltage and current, three-phase delivers about 83 kW instead of 48 kW (at PF = 1) when V_line = 480 V and I_line = 100 A. So the stated percentage is about 73%.