Operating instructions

Functions
5.8 Protection functions
CU240S and CU240E Control Units, FW 3.2
122 Operating Instructions, 03/2009, A5E02440075B AA
5.8.4 Load torque monitoring (system protection)
Applications with load torque monitoring
In many applications, it is advisable to monitor the motor torque:
● Applications in which the mechanical connection between the motor and load may be
interrupted (e.g. if the drive belt in fan or conveyor belt systems tears).
● Applications that are to be protected against overload or locking (e.g. extruders or
mixers).
● Applications in which no-load operation of the motor represents a critical situation (e.g.
pumps).
Load torque monitoring functions
The inverter monitors the torque of the motor in different ways:
1. No-load monitoring:
The inverter generates a message if the motor torque is too low.
2. Lock protection:
The inverter generates a message if the motor speed cannot match the speed setpoint
despite maximum torque.
3. Stall protection:
The inverter generates a message if the inverter control has lost the orientation of the
motor.
4. Frequency-dependent torque monitoring:
The inverter measures the current torque and compares it with a parameterized
frequency/torque characteristic.
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