58 ACQ800-37 Hardware ManualPlanning the electrical installationThermal 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 the motor in a short-circuit situation when themotor cable is dimensioned according to the nominal current of the drive.Supply (AC line) cable short-circuit protectionAlways protect the input cable with fuses. In networks with a short-circuit withstandof 65 kA or less, standard gG fuses can be used. No fuses need be installed at thedrive input.If the drive is supplied through busbars, fuses must be installed at the drive input. Innetworks with a short-circuit withstand of less than 50 kA, standard gG fuses aresufficient. If the network has a short-circuit withstand of 50 to 65 kA, aR fuses arerequired.Size the fuses according to local safety regulations, appropriate input voltage andthe rated current of the drive. Check that the operating time of the fuses is below0.5 seconds. For fuse ratings, see Technical data.WARNING! Circuit breakers are not capable of providing sufficient protectionbecause they are inherently slower than fuses. Always use fuses with circuitbreakers.Earth fault (Ground fault) protectionBoth the supply unit and the inverter unit are equipped with an internal earth faultprotective function to protect the drive against earth faults in the drive, motor andmotor cable. (This is not a personal safety or a fire protection feature.) Both earthfault protective functions can be disabled by a parameter.See the ACQ800 Ordering Information (code: 64556568 [English], available onrequest) for other available earth fault protection options.
