7.7 : 力率補正

The power transmission to a factory involves the transfer of both active and reactive power. The ratio of active to total power defines the power factor.

A low power factor means the inductive electrical load absorbs more reactive power, causing a low lagging power factor. This results in large voltage drops across the load and thermal losses, increasing electricity costs and reducing system efficiency.

The power factor can be improved by adding a compensating impedance like self-tuning capacitors parallel to the load. This approach brings the power factor as close to unity as possible.

The effect of adding the capacitor can be demonstrated using the power triangle. By examining the power triangle of the original circuit, the real and reactive power can be determined.

Adding a capacitive load decreases the power factor angle without changing the real power. From the new triangle, the value of the corrected reactive power is calculated.

This reduction in reactive power results from the shunt capacitance. By revisiting the expressions of reactive power, the shunt capacitor value is determined.