Hitachi X200-002SFE/NFU Instruction Manuals page 185

4−46
To use the PID Second Stage Output feature, you will need to choose upper and lower
limits for the PV, via C053 and C052 respectively. As the timing diagram below shows,
these are the thresholds Stage #1 inverter uses to turn ON or OFF Stage #2 inverter via
the [FBV] output. The vertical axis units are percent (%) for the PID setpoint, and for
the upper and lower limits. The output frequency, in Hz, is superimposed onto the same
diagram.
When the system control begins, the following events occur (in sequence in the timing
diagram):
1. Stage #1 inverter turns ON via the [FW] Run command.
2. Stage #1 inverter turns ON the [FBV] output, because the PV is below the PV low
3. The PV rises and eventually exceeds the PV high limit C052. Stage #1 inverter then
4. When the PV begins decreasing, only Stage #1 is operating, and it is in the linear
5. The PV continues to decrease until it crosses under the PV low limit (apparent
6. After the PV rises above the PV low limit, the [FW] Run command to Stage #1
7. Stage #1 inverter enters Stop Mode and automatically turns OFF the [FBV] output,
The terminal [FBV] configuration table is on the following page.
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limit C053. So, Stage #2 is assisting in loop error correction from the beginning.
turns OFF the [FBV] output to Stage #2, since the boost is no longer needed.
control range. This region is where a properly configured system will operate most
often.
external process disturbance). Stage #1 inverter turns ON the [FBV] output, and
Stage #2 inverter is assisting again.
inverter turns OFF (as in a system shutdown).
which causes Stage #2 inverter to also stop.
%/Hz
PV high limit C052
PID setpoint (SP)
PV low limit C053
Stage #1 [FW] 1
0
1
[FBV] to Stage #2 [FW]
0
Events:
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PID feedback (PV)
Output frequency
1,2 3 4
t
5 6 7