Planning the electrical installation
43
Thermal overload and short-circuit protection
The drive protects itself and the input and motor cables against thermal overload
when the cables are dimensioned according to the nominal current of the drive. No
additional thermal protection devices are needed.
WARNING! If the drive is connected to multiple motors, a separate thermal overload
switch or a circuit breaker must be used for protecting each cable and motor. These
devices 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 the
motor cable is dimensioned according to the nominal current of the drive.
Mains cable (AC line cable) short-circuit protection
Always protect the input cable with fuses. Size the fuses according to local safety
regulations, appropriate input voltage and the rated current of the drive (see
Technical Data).
ACS800-01/U1, ACS800-11/U11, ACS800-02/U2 without enclosure extension and
ACS800-04/U4
When placed at the distribution board, standard gG fuses (US: CC or T for the
ACS800-U1 and ACS800-U11; T or L for the ACS800-U2 and ACS800-U4) will
protect the input cable in short-circuit situations, restrict drive damage and prevent
damage 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 are
equipped 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 case
of a short-circuit inside the drive.
Operating time of the fuses
Check that the operating time of the fuse is below 0.5 seconds. The operating
time 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 seconds
operating time is exceeded with gG fuses (US: CC/T/L), ultrarapid (aR) fuses will in
most cases reduce the operating time to an acceptable level. The US fuses must be
of the “non-time delay” type.
For fuse ratings, see Technical Data.
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