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Using Intelligent Output Terminals
Operations
and Monitoring
4–24
Frequency arrival output [FA1] uses the
standard output frequency (parameter
F_01) as the threshold for switching. In
the figure to the right, Frequency Arrival
[FA1] turns ON when the output
frequency gets within 0.5 Hz below or
1.5 Hz above the target constant
frequency. This provides hysteresis that
prevents output chatter near the threshold
value.The hysteresis effect causes the
output to turn ON slightly early as the
speed approaches the threshold. Then the
turn-OFF point is slightly delayed. The
timing is further modified by a small
60 ms delay. Note the active low nature of
the signal, due to the open collector output.
Frequency arrival output [FA2] works the
same way; it just uses two separate
thresholds as shown in the figure to the
right. These provide for separate acceler-
ation and deceleration thresholds to
provide more flexibility than for [FA1].
[FA2] uses C_42 during acceleration for
the ON threshold, and C_43 during decel-
eration for the OFF threshold. This signal
also is active low and has a 60 ms delay
after the frequency thresholds are
crossed. Having different accel and decel
thresholds provides an asymmetrical
output function. However, you can use
equal ON and OFF thresholds, if desired.
FA1
signal
Output
freq.
F01 F01
60 ms 60 ms
ON ON
t
0.5 Hz
0.5 Hz
1.5 Hz
1.5 Hz
0
t
FA2
signal
Output
freq.
C42
C43
t
ON
0.5 Hz
1.5 Hz
60 ms
accel.
decel.
Thresholds
60 ms
0