ABB RELION 620 Series Technical Manual page 776

Section 9
Control functions
9.5.5
770
GUID-18128621-4A78-45D0-A788-9116B5213449 V1 EN
Figure 395: Functional module diagram
Standstill detector
The module detects if the motor is in a standstill condition. The standstill condition can be
detected based on the phase current values. If all three phase currents are below the set
value of Motor standstill A, the motor is considered to be in a standstill condition.
Timer
The timer is a fixed 10-minute timer that is activated when the ST_EMERG_RQ input is
activated and motor standstill condition is fulfilled. Thus, the activation of the
ST_EMERG_RQ input activates the ST_EMERG_ENA output, provided that the motor is
in a standstill condition. The ST_EMERG_ENA output remains active for 10 minutes or as
long as the ST_EMERG_RQ input is high, whichever takes longer.
The activation of the BLOCK input blocks and also resets the timer.
The function also provides the ST_EMERG_ENA output change date and time,
T_ST_EMERG. The information is available in the monitored data view.
Application
If the motor needs to be started in an emergency condition at the risk of damaging the
motor, all the external restart inhibits are ignored, allowing the motor to be restarted.
Furthermore, if the calculated thermal level is higher than the restart inhibit level at an
emergency start condition, the calculated thermal level is set slightly below the restart
inhibit level. Also, if the register value of the cumulative startup time counter exceeds the
restart inhibit level, the value is set slightly below the restart disable value to allow at least
one motor startup.
The activation of the ST_EMERG_RQ digital input allows to perform emergency start.
The protection relay is forced to a state which allows the restart of motor, and the operator
can now restart the motor. A new emergency start cannot be made until the 10 minute
time-out has passed or until the emergency start is released, whichever takes longer.
The last change of the emergency start output signal is recorded.
1MAC504801-IB E
620 series ANSI
Technical Manual