About

In industrial environments, 380V to 415V Three-Phase power is the backbone of heavy machinery. Calculating the power consumption (kW) from amperage readings on these systems requires a specific formula that accounts for the phase geometry. Unlike single-phase calculations, three-phase power uses the square root of 3 (√3) multiplier when using Line-to-Line voltage. This tool is designed for facility managers and electricians to quickly verify motor loads and transformer capacities.

Formulas

The calculator uses the standard active power formula for balanced three-phase systems:

PkW = 1.732 × I × VL-L × PF1000

Note: VL-L is the voltage between two phases (e.g., 380V, 400V, 415V), NOT phase-to-neutral (220V).

Reference Data

Motor Rating (Est)	Voltage (VLL)	Amps (I)	PF	Power Output (kW)
Small Ind. Motor	380	5.5	0.82	2.97 kW
HVAC Pump	380	12.0	0.85	6.71 kW
Conveyor Drive	400	25.0	0.78	13.51 kW
Heavy Compressor	415	60.0	0.88	37.95 kW
Ind. Heater (Res)	380	30.0	1.0	19.74 kW
Machine Tool	380	15.0	0.8	7.90 kW
Large Fan	400	45.0	0.86	26.81 kW
Crusher	380	120.0	0.9	71.08 kW

Frequently Asked Questions

The multiplier 1.732 is the decimal approximation of the square root of 3. In a three-phase system, the voltage peaks of the three wires are offset by 120 degrees. The square root of 3 mathematically relates the Line-to-Line voltage to the Line-to-Neutral components.

Yes. Although the default is 380V, you can manually enter 480V (common in the USA) or 600V (Canada) into the voltage field. The formula remains exactly the same.

Look at the motor's nameplate data. It is often labeled as "P.F.", "Cos φ", or "Power Factor". If the data is missing, 0.8 to 0.85 is a standard estimation for induction motors running at load.

This calculates the Electrical Power (input power) drawn from the grid. To get the Shaft Power (mechanical output), you would also need to multiply by the motor's Efficiency rating (η).