In a three-phase circuit, the same amount of current will produce different powers under different loads.
Taking the line voltage of 380V and the current of 1A as an example, calculate the power of resistive load and inductive load respectively:
1) In resistive (electric heating) load.
P=√3UI
=√3×380×1
≈658W.
2) In inductance (motor) Loading.
P=√3UIcosφη (where, cosφ-power factor, eta-mechanical efficiency)
=√3×380×1×0.9×0.85 (assuming power Factor = 0.9, mechanical efficiency = 0.85)
≈503W
The size of the power factor is related to the load properties of the circuit. For example, the power factor of resistive loads such as incandescent light bulbs and resistance furnaces is 1 , generally the power factor of circuits with inductive loads is less than 1. Power factor is an important technical data of the power system. Power factor is a coefficient that measures the efficiency of electrical equipment. A low power factor indicates that the circuit uses large reactive power for alternating magnetic field conversion, thereby reducing equipment utilization and increasing line power supply losses. Therefore, measures such as parallel capacitors must be taken to compensate for reactive power to improve the power factor.