Planning the electrical installation43Thermal overload and short-circuit protectionThe drive protects itself and the input and motor cables against thermal overloadwhen the cables are dimensioned according to the nominal current of the drive. Noadditional thermal protection devices are needed.WARNING! If the drive is connected to multiple motors, a separate thermal overloadswitch or a circuit breaker must be used for protecting each cable and motor. Thesedevices may require a separate fuse to cut off the short-circuit current.The drive protects the motor cable and motor in a short-circuit situation when themotor cable is dimensioned according to the nominal current of the drive.Mains cable (AC line cable) short-circuit protectionAlways protect the input cable with fuses. Size the fuses according to local safetyregulations, appropriate input voltage and the rated current of the drive (seeTechnical Data).ACS800-01/U1, ACS800-11/U11, ACS800-02/U2 without enclosure extension andACS800-04/U4When placed at the distribution board, standard gG fuses (US: CC or T for theACS800-U1 and ACS800-U11; T or L for the ACS800-U2 and ACS800-U4) willprotect the input cable in short-circuit situations, restrict drive damage and preventdamage to adjoining equipment in case of a short-circuit inside the drive.Drive AC fuses (ACS800-07/U7, and ACS800-02/U2 with enclosure extension)ACS800-07/U7 units and ACS800-02/U2 units with enclosure extension areequipped with standard gG (US: T/L) or optional aR fuses listed in Technical Data.The fuses restrict drive damage and prevent damage to adjoining equipment in caseof a short-circuit inside the drive.Operating time of the fusesCheck that the operating time of the fuse is below 0.5 seconds. The operatingtime depends on the fuse type (gG or aR), supply network impedance and the cross-sectional area, material and length of the supply cable. In case the 0.5 secondsoperating time is exceeded with gG fuses (US: CC/T/L), ultrarapid (aR) fuses will inmost cases reduce the operating time to an acceptable level. The US fuses must beof the ìnon-time delayî type.For fuse ratings, see Technical Data.
