In AC circuits, the current absorbed by a load can be represented by two components - the active component and the reactive component. Improving the power factor (PF) means increasing it in a defined section of the installation by locally delivering the necessary reactive power. This will result in the current (and power) flowing through the upstream network being reduced, at the same required output power. Therefore, generators and transformers can be economically sized for a lower apparent power, as this ABB Technical paper explains:
PF correction obtained by using capacitor banks to generate locally the reactive energy necessary for the transfer of electrical useful power, allowing a better and more rational technical-economical management of plants.
Moreover, today's increases in DC using devices, such as electronic circuits and electric drives, involve the generation of current harmonics which are injected into the network, with the consequent pollution and distortion of the waveforms on other connected loads. Therefore, the use of harmonic filters, both of passive as well as of active type, contributes to improve the overall power quality of the network, carrying out also PF correction at the network frequency, when such filters are properly sized.
This technical paper analyses such problems. It starts from the definition of PF correction, and from an analysis of the technical-economical advantages, it describes how to achieve PF correction. It also guides users to the best choice of devices for the switching of capacitor banks and filtering of harmonics.
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