ABB Relion 620 Series - Page 759

Figure 397: 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.
In the "IIt & stall" mode, the function calculates the thermal stress of the motor
during the start-up condition. The start-up condition is detected by monitoring the
TRMS currents.
In the "IIt & stall, CB" mode, the function calculates the thermal stress of the motor
during the start-up condition but the start-up condition is detected by monitoring
the TRMS current as well as the circuit breaker status.
In both the "IIt & stall" and "IIt & stall, CB" mode, the function also checks for motor
stalling by monitoring the speed switch.
When the measured current value is used for start-up supervision in the "IIt" and
"IIt & stall" modes, the module initially recognizes the de-energized condition of the
motor when the values of all three phase currents are less than Motor standstill A
for longer than 100 milliseconds. If any of the phase currents of the de-energized
condition rises to a value equal to or greater than Motor standstill A , the MOT_START
output signal is activated indicating that the motor start-up is in progress. The
MOT_START output remains active until the values of all three phase currents drop
1MRS757644 H
Protection functions
620 series
Technical Manual
759