Planning the electrical installation
48
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 the firmware manual for more information on the motor thermal protection, and
the connection and use of the temperature sensors.
Protection against short-circuit in the 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.
Protection against short-circuit inside the drive or in the supply cable
Arrange the protection according to the following guide lines.
1) Size the fuses according to instructions given in chapter Technical data. The fuses 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.
Circuit diagram Short-circuit
protection
Protect the drive and
input cable with fuses
or a circuit breaker.
See footnotes 1) and
2).
~
~
M
3~
Distribution
board
Input cable
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~
M
3~
Drive or drive
module
1)
2)
I >
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