ABB REF615 G - Function Block

4.4.3.2 Function block
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Figure 244: Function block
4.4.3.3 Functionality
The phase reversal protection PREVPTOC is used to detect the reversed
connection of the phases to a three-phase motor by monitoring the negative phase
sequence current I
2
of the motor.
PREVPTOC starts and operates when I
2
exceeds the set limit. PREVPTOC
operates on definite time (DT) characteristics. PREVPTOC is based on the
calculated I
2
, and the function detects too high I
2
values during the motor startup.
The excessive I
2
values are caused by incorrectly connected phases, which in turn
makes the motor rotate in the opposite direction.
The function contains a blocking functionality. It is possible to block function
outputs, timer or the function itself, if desired.
4.4.3.4 Operation principle
The function can be enabled and disabled with the Operation setting. The
corresponding parameter values are "On" and "Off".
The operation of phase reversal protection can be described with a module
diagram. All the modules in the diagram are explained in the next sections.
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Figure 245: Functional module diagram
Level detector
The level detector compares the negative-sequence current to the set Start value. If
the I
2
value exceeds the set Start value, the level detector sends an enabling signal
to the timer module.
Timer
Once activated, the timer activates the START output. When the operation timer
has reached the set Operate delay time value, the OPERATE output is activated. If
1YHT530004D05 D Section 4
Protection functions
615 series 457
Technical Manual