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Schneider Electric Egypt×
The Prospective Short circuit capacity mentioned in drive catalog is indicating the drive's suitability to use in a electrical feeder with out any additional input impedence to the line supply. It means, for example the drive ATV61H075N4 can be used up to 5KA short circuit current rated supply feeder with out any problem. If the supply feeder's SCC rating is higher than the value mentioned in catalog, it is necessary to use a line choke or DC choke to increase the input impedence of the drive, which will help to increase the PSCC rating of the drive above 50KA to 100KA. It will also help to reduce the peak current, RMS current and harmonics. The doccument in below attachment will help to explain the effect of PSCC in drive functioning in detail.
Generally there are two topics concerning the short circuit capability of the mains:
A strong mains supply (= high Isc) has a low impedance. Therefore it allows high peak current, RMS current and harmonic, which can overload and damage the rectifier and DC Bus capacitors of the standard drive.
With a DC choke (which is behind the rectifier) a Isc of 50kA is allowed.
With a line choke (which is in front the rectifier) a Isc of 100kA is allowed.
b) In case of a short circuit:
If there is a short circuit the protective device (fuse or circuit breaker) must be able to interrupt this high current. If this is not the case, it will burn the drive input.