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If the drive is supplied through busbars, fuses must be installed at the drive input. In
networks with a short-circuit withstand of less than 50 kA, standard gG fuses are
sufficient. If the network has a short-circuit withstand of 50...65 kA, aR fuses are
required.
Size the fuses according to local safety regulations, appropriate input voltage and
the rated current of the drive. Check that the operating time of the fuses is below
0.5 seconds. For fuse ratings, see chapter
WARNING! Circuit breakers are not capable of providing sufficient protection
because they are inherently slower than fuses. Always use fuses with circuit
breakers.
Protecting the motor and motor cable in short-circuit situations
The drive protects the motor cable and the 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.
Protecting the drive, motor cable and input power cable against thermal overload
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.
Protecting the motor against thermal overload
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 eg, 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.
Planning the electrical installation
Technical
data.
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