ABB RELION 620 Series Technical Manual page 763

1MRS757644 F
4.10.4
620 series
Technical Manual
STTPMSU also protects the motor from an excessive number of start-ups. Upon
exceeding the specified number of start-ups within certain duration, STTPMSU
blocks further starts. The restart of the motor is also inhibited after each start and
continues to be inhibited for a set duration. When the lock of start of motor is enabled,
STTPMSU gives the time remaining until the restart of the motor.
The function contains a blocking functionality. It is possible to block function outputs,
timer or the function itself, if desired.
Operation principle
The function can be enabled and disabled with the Operation setting. The
corresponding parameter values are "On" and "Off".
The operation of STTPMSU can be described with a module diagram. All the modules
in the diagram are explained in the next sections.
GUID-35DD1223-14B2-48BF-ADF4-4A1DF6930314 V1 EN
Figure 387: Functional module diagram
Startup supervisor
This module detects the starting of the motor. The starting and stalling motor
conditions are detected in four different modes of operation. This is done through the
Operation mode setting.
When the Operation mode setting is operated in the "IIt" mode, the function calculates
the value of the thermal stress of the motor during the start-up condition. In this mode,
the start-up condition is detected by monitoring the TRMS currents.
The Operation mode setting in the "IIt, CB" mode enables the function to calculate the
value of the thermal stress when a start-up is monitored in addition to the CB_CLOSED
input.
Section 4
Protection functions
757