1MAC050144-MB C
Section 7
Control functions
615 series ANSI
531
Technical Manual
7.4.4
Operation principle
The function can be enabled and disabled with the
Operation
setting. The corresponding
parameter values are Enable and Disable.
The operation of the emergency start function can be described using a module diagram.
All the modules in the diagram are explained in the next sections.
Figure 292:
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 which 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 through the Monitored data view.
7.4.5
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
IED 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.
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