Hitachi SJ700-055HFF2, Instruction Manual

Page: 92 / 284

Chapter 4 Explanation of Functions
(7) Output of inverted PID deviation
If the inverter is under the normal PID control and the PID operation result is a negative value, the
frequency command to the inverter will be limited to 0 Hz. However, when "02" (enabling the inverted
output) is set for the PID Function Enable (A071), the PID operation result to be output to the inverter is
inverted if the result is a negative value.
Setting "02" for function "A071" disables the PID variation limit (A078) described above.
(8) PID gain adjustment
If the inverter response is unsteady when the PID control function is used, try to adjust gain settings as
follows:
- If the feedback data does not quickly follow the change in the target value
→
Increase the P gain (A072).
- If the feedback data is unstable although it quickly follows the change in the target value
→
Reduce the
P gain (A072).
- If considerable time is required until the feedback data matches the target value
→
Reduce the I gain
(A073).
- If the feedback data fluctuates unsteadily
→
Increase the I gain (A073).
- If the inverter response is slow even after the P gain is increased
→
Increase the D gain (A074).
- If the feedback data becomes fluctuant and unsteady when the P gain is increased
→
Reduce the D gain
(A074).
(9) Maximum PID deviation output (OD)
You can set the PID deviation level (C044) for PID control. When the PID deviation (
ε
) exceeds the level
set as the level "C044", the signal is output to an intelligent output terminal.
A value from 0 to 100 can be set as the level "C044". The range of values corresponds to the range of
target values from 0 to the maximum.
To use this output function, assign function "04" (OD) to one of the terminal functions C021 to C025 or the
alarm relay terminal function C026.
(10) Feedback comparison signal
A feedback comparison signal can be output to an intelligent output terminal when the PID feedback data
exceeds the specified range.
To use this signal output function, assign function "31" (FBV) to one of the terminal functions C021 to C025
or the alarm relay terminal function C026.
FW
FBV
ON
OFF
OFF
ON
PID feedback
C052 (off level)
C053 (on level)
Time
(11) Process variable (PV), PID feedback monitoring (d004)
You can monitor the PID feedback data on the inverter.
When you set a PV scale conversion with function "A075", the value to be displayed as the monitored data
can be the product of the feedback data and the scale.
"Monitored value" = "feedback data (%)" x " PV scale conversion (A075)"
(12) Reset of PID integration (PIDC)
This reset function clears the integral result of PID operation.
To use this function, assign function "24" (PIDC) to one of the terminal functions C001 to C008.
The integral result is cleared each time the PIDC terminal is turned on.
Never turn on the PIDC terminal during the PID operation. Otherwise, the inverter may trip because of
overcurrent. Be sure to disable the PID function before turning on the PIDC terminal.
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