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Schneider Electric Egypt×
The PFC system can be divided to incomer to the PFC system, and outgoing(s); where the outgoing(s) of the system can be assumed to be the capacitor stages (PFC stages). The main incomer is used to disconnect the PFC system in case of short circuit, over load and earth fault. The rating of the incomer switchgear will vary depending on rating of the APFC (Automatic Power Factor Correction) equipment and the required fault current handling capacity. SDF (switch-disconnector fuse), MCCB or ACB can be used as incomer switchgear depending on the current rating of the APFC equipment and the required fault level.
Outgoing protection is provided to protect the individual capacitor step in the APFC equipment. The outgoing protection may be fuses, MCB, MCCB & SDF depending on the rating of the individual capacitor steps, required fault level & customer requirement too.
It must be noted that a safety factor of (1.5 x In) is used for selecting all switchgear. The factor of 1.5 has arrived by taking into account the combined effects of harmonics, Over Voltage and capacitance tolerance as per standard IEC 60831.
For a better selection of protection devices, kindly check the examples in the attached file (PFC - Selection of Protective devices.pdf). And for deeper knowledge concerning the design of PFC systems, kindly check the Guide for the Design and Production of LV Power Factor Correction Cubicle (attached). This guide will suit you best as it is dedicated for panel builders.
For proper selection and for a better understanding concerning braking capacities and short circuit calculations, you could either refer to the attached document (Calculation of Short Circuit Currents.pdf) or you could use our electrical calculation software "Ecodial". The software can be downloaded via our website through the following link: