Figure 152: Logic diagram for phase selection module
When the
Number of start phase
setting is set to "1 out of 3" and the fault is in one
or several phases, the phase selection logic sends an enabling signal to the faulty
phase timers. If the fault disappears, the related timer-enabling signal is removed.
When the
Number of start phase
setting is "2 out of 3" or "3 out of 3", single-phase
faults are not detected. The value "3 out of 3" requires the fault to be present in all
three phases.
Timer A, Timer B, Timer C
The function design contains three independent phase-segregated timers which are
controlled by common settings. This design allows a true three-phase overcurrent
protection which is useful in some applications.
The common START and OPERATE outputs are created by "ORing" the phasespecific
starting and operating outputs.
Each phase has its own phase-specific starting and operating outputs: ST_A, ST_B,
ST_C, OPR_A, OPR_B and OPR_C.
Protection functions
1MRS757644 H
304 620 series
Technical Manual
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