Thermal Overload And Short-Circuit Protection; Ground Fault Protection - ABB ACS800 Hardware Manual

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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).
Drive AC Fuses (Standard on ACS800-PC)
ACS800-PC units are equipped with Fast Acting Current Limiting Class T (JJS-xxx)
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, 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 Class T fuses, 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.
WARNING! Circuit breakers must not be used without fuses.

Ground Fault Protection

The drive is equipped with an internal ground fault protective function to protect the
unit against ground faults in the motor and motor cable. This is not a personal safety
or a fire protection feature. The ground fault protective function can be disabled with
a parameter, refer to the appropriate ACS800 Firmware Manual.
The EMC filter of the drive includes capacitors connected between the main circuit
and the frame. These capacitors and long motor cables increase the ground leakage
current and may cause fault current circuit breakers to function.
Planning the Electrical Installation