Enter your motor's Power Rating, Line-to-Line Voltage, Power Factor (cos φ), and Motor Efficiency into the 3-Phase Motor Amperage Calculator to find the Full Load Current (FLA) — plus Power in kW, Apparent Power, and Line Current per Phase so you have everything you need to size wiring, breakers, and overloads correctly.
Full Load Current (FLA)
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Power in kW
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Apparent Power
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Line Current per Phase
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For 3-phase motors, use the formula: I = (P × 1000) / (√3 × V × PF × η), where I is current in amps, P is power in kW, V is line-to-line voltage, PF is power factor, and η is efficiency as a decimal.
FLA (Full Load Amps) is the current drawn when the motor operates at its rated load, typically determined in laboratory tests. RLA (Running Load Amps) is the actual current drawn during normal operation, usually about 80% of FLA.
Most 3-phase AC motors have a power factor between 0.8 and 0.9, with 0.86 being a common value. High-efficiency motors may have power factors as high as 0.95, while older or smaller motors may be lower.
A 5 hp 3-phase motor at 460V typically draws about 7-8 amps at full load, depending on efficiency and power factor. At 230V, the same motor would draw approximately 14-16 amps.
Motor efficiency affects the actual power drawn from the electrical supply. A motor with 90% efficiency will draw more current than one with 95% efficiency for the same mechanical output power.
Use the line-to-line voltage (phase-to-phase voltage) for 3-phase calculations. Common values include 208V, 230V, 460V, 575V in North America, and 380V, 415V in other regions.
To convert horsepower to kilowatts, multiply by 0.746. For example, 5 hp = 5 × 0.746 = 3.73 kW. This conversion is automatically handled in the calculator.