Hitachi WJ Series User Manual page 232

Chapter 9
Other functions related to the PID function
A
◼ PID feed-forward setting
 PID control allows the use of feed-forward control that attempts to pre-stabilize any external
disturbances.
 Set the "PID feed-forward input source selection [A079]" to "[Ai1] terminal input (01)" or "[Ai2]
terminal input (02)" to enable feed-forward input.
 Feed-forward input settings can be duplicated with target value input and feedback input. When
creating duplicate settings, the same analog input value is entered for both.
◼ Invert the sign of PID deviation and output
 Certain sensor characteristics may cause inconsistencies between the polarity of deviation
between the target value and the feedback value and the inverter command. In such a case, set
"PID deviation inversion [A077]" to "Enable (01)" to invert the polarity of deviation.
Example: Controlling a refrigerator compressor
PID target value
Feedback data value
◼
PID output range limit
 This function limits PID output to the PID target value ± "PID output range [A078]", and prevents
sudden fluctuations in the output frequency caused by PID calculations. Set [A078] with the
maximum frequency being 100%.
 This function is disabled when [A078] is 0.0.
PID output (%)
PID target
value
◼ PID disable function
 Turn on the "Disable PID [PID] (23)" input to disable PID operation. While the [PID] input is on,
the inverter outputs according to the frequency command.
 When using the PID disable function, assign " Disable PID [PID] (23)" to one of the input
terminals.
Assuming temperature sensor specifications of -20 to 100°C: 0 to 10 (V), with a
target value of 0°C, if the current temperature is 10°C, normal PID control will
decrease the speed of the inverter as the (FB value) > (PID target value). If [A077] is
set to "Enable (01)", the inverter will increase its speed.
+
-
PID deviation
inversion
[A077]
00
01
x (-1)
PID output
range
PID output range [A078]
PID output range [A078]
9-8-6
Inverter Functions
PID deviation monitor
[d153]
PID calculation
Time (s)