Monitoring The Driven Load - Siemens SINAMICS G120 Operating Instructions Manual

6.31

Monitoring the driven load

In many applications, the speed and the torque of the motor can be used to determine whether
the driven load is in an impermissible operating state. The use of an appropriate monitoring
function in the inverter prevents failures and damage to the machine or plant.
Examples:
● For fans or conveyor belts, an excessively low torque can mean a broken drive belt.
● For pumps, insufficient torque can indicate a leakage or dry-running.
● For extruders and mixers, an excessive torque together with low speed can indicate
machine blockage.
Functions for monitoring the driven load
The inverter provides the following means to monitor the driven load via the torque of the motor:
Monitoring the driven load with a binary signal:
Converter with the CU230P-2 Control Units
Operating Instructions, 09/2017, FW V4.7 SP9, A5E34257946B AE
The stall protection prevents an induction motor from stalling
The no-load monitoring evaluates the motor current. Insufficient current indicates
that the motor and the load are no longer mechanically connected with each other.
The blocking protection triggers for a motor current that corresponds to the set
current limit coupled with motor standstill.
The torque monitoring assumes that a specific torque is associated with each
speed for pumps and fans. Insufficient torque indicates that the motor and the load
are no longer mechanically connected.
An excessive torque can indicate problems in the mechanical system of the driven
load, e.g. a mechanically blocked load.
Blocking protection, leakage protection and dry-running protection are a monitor‐
ing method for pumps or fans. The monitoring combines a torque monitoring with
a blocking protection.
The speed monitoring evaluates a periodic binary signal. A signal failure indicates
that the motor and the load are no longer mechanically connected with each other.
Advanced commissioning
6.31 Monitoring the driven load
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