Power factor calculation formula

Power factor calculation formula

The power factor refers to the cosine of the phase difference between the voltage U at both ends of any two-terminal network (a circuit with two contacts to the outside world) and the current I therein. The power consumed in a two-terminal network refers to the average power, also known as active power, which is equal to It
can be seen from this that the power P consumed in the circuit depends not only on the magnitude of the voltage V and the current I, but also on the power factor. The magnitude of the power factor depends on the nature of the load in the circuit. For a resistive load, the phase difference between the voltage and the current is 0, so the power factor of the circuit is the largest ( ); while for a pure inductive circuit, the phase difference between the voltage and the current is π/2, and the voltage leads the current; in a pure capacitive circuit, the phase difference between the voltage and the current is -(π/2), that is, the current leads the voltage. In the latter two circuits, the power factor is 0. For a circuit with a general load, the power factor is between 0 and 1.

Generally speaking, in a two-terminal network, improving the power factor of electrical appliances has two meanings. One is that it can reduce the power loss on the transmission line; the other is that it can give full play to the potential of power equipment (such as generators, transformers, etc.). Because electrical appliances always work under a certain voltage U and a certain active power P, it can be seen from the formula :

if the power factor is too low, a larger current must be used to ensure the normal operation of the electrical appliances. At the same time, the transmission current on the transmission line increases, which leads to an increase in Joule heat loss on the line. In addition, the voltage drop on the resistance of the transmission line and the internal group of the power supply are proportional to the current in the electrical appliance. Increasing the current will inevitably increase the voltage loss in the transmission line and the power supply. Therefore, improving the power factor of electrical appliances can reduce the transmission current, thereby reducing the power loss on the transmission line.