Application; Signals - ABB RELION REX640 Technical Manual

1MRS759142 C
4.1.7.6
4.1.7.7
REX640
Technical Manual
Timer
Once activated, the timer activates the START output. The time characteristic is
according to DT. When the operation timer has reached the value set by Operate delay
time, the OPERATE output is activated. If the fault disappears before the module
operates, the reset timer is activated. If the reset timer reaches the value set by Reset
delay time, the operate timer resets and the START output is deactivated.
The timer calculates the start duration value START_DUR, which indicates the
percentage ratio of the start situation and the set operating time. The value is available
in the monitored data view.
The BLOCK signal blocks the operation of the function and resets the timer.

Application

When a motor runs with a load connected, it draws a current equal to a value between
the no-load value and the rated current of the motor. The minimum load current can
be determined by studying the characteristics of the connected load. When the current
drawn by the motor is less than the minimum load current drawn, it can be inferred that
the motor is either disconnected from the load or the coupling mechanism is faulty. If
the motor is allowed to run in this condition, it may aggravate the fault in the coupling
mechanism or harm the personnel handling the machine. Therefore, the motor has to
be disconnected from the power supply as soon as the above condition is detected.
LOFLPTUC detects the condition by monitoring the current values and helps
disconnect the motor from the power supply instantaneously or after a delay according
to the requirement.
When the motor is at standstill, the current will be zero and it is not recommended to
activate the trip during this time. The minimum current drawn by the motor when it is
connected to the power supply is the no load current, that is, the higher start value
current. If the current drawn is below the lower start value current, the motor is
disconnected from the power supply. LOFLPTUC detects this condition and
interprets that the motor is de-energized and disables the function to prevent
unnecessary trip events.

Signals

Table 425: LOFLPTUC Input signals
Name Type
I3P SIGNAL
BLOCK BOOLEAN
Table 426: LOFLPTUC Output signals
Name Type
OPERATE BOOLEAN
START BOOLEAN
Protection functions
Default Description
- Three-phase currents
0=False Block all binary outputs by resetting timers
Description
Operate
Start
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