ACS550-02/U2 User’s Manual 19
Planning the electrical installation
Thermal overload and short-circuit protection
Thermal overload protection of the drive and the input and motor cables
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.
Thermal overload protection of the motor
According to regulations, the motor must be protected against thermal overload and
the current must be switched off when overload is detected. The drive includes a
motor thermal protection function that protects the motor and switches off the current
when necessary. Depending on a drive parameter value, the function either monitors
a calculated temperature value (based on a motor thermal model) or an actual
temperature indication given by motor temperature sensors. The user can tune the
thermal model further by feeding in additional motor and load data.
The most common temperature sensors are:
• motor sizes IEC180…225: thermal switch (e.g. Klixon)
• motor sizes IEC200…250 and larger: PTC or Pt100.
See Group 30: FAULT FUNCTIONS on page 170 for more information on the motor
thermal protection by the software and Group 35: MOTOR TEMP MEAS on page
180 for the connection and use of the temperature sensors.
Protection against short-circuit in the motor and motor cable
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. No
additional protection devices are needed.
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