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PID control (Pr. 128 to Pr. 134)
(7) Adjustment example
(A detector of 0V at 0°C and 10V at 50°C is used to adjust the room temperature to 25°C under PID control.
The set point is given to across inverter terminals 2-5 (0 to 10V).)
START
Convert the set
point into %.
Calculate the ratio of the set
point to the detector output.
Make calibration.
Set the set point.
Enter a voltage to across
terminals 2-5 according to the
set point (%).
Operation
Is the process
value steady?
Adjust parameters.
Set the proportional band and integral time to slightly
higher values and set the differential time to a slightly
lower value to stabilize the process value.
Optimize parameters.
While the process value is steady, the proportional band and
integral time may be reduced and the differential time increased
throughout the operation.
END
Yes
No
Set the proportional band and
integral time to slightly higher
values and the differential time
to "9999", and turn on the start
signal.
Determine the set point.
Determine the set point of the
item to be adjusted.
When calibration is required, use Pr. 902, Pr.903, Pr.917, Pr.918 to calibrate the set point setting input and detector output.
Calibration is made in the PU mode during an inverter stop.
For operation, set the proportional band and integral time to slightly higher values
and set the differential time to "9999" (function invalid).
In accordance with the system operation, reduce the proportional band and increase
the integral time. In a slow-response system that has a dead band, gradually increase
it using differential control.
Set the room temperature to 25 C.
Set "30" or "31" in Pr. 128 and turn on the X14 signal to enable PID control.
Set point = 50%
Since the specifications of terminal 2 are such that 0% is equivalent to 0V and 100% to 10V,
enter 5V into terminal 2.
When the parameter unit is used to perform operation, set the set point (0 to 100%) in Pr. 133.
When the set point setting input (0 to 10V) and detector output (0 to 10V) must be calibrated,
make the following calibration*.
Detector specifications
When the detector used has the specifications that 0 C is equivalent to 0V and
50 C to 10V, the set point of 25 C is 50 % because 0V is equivalent to 0%
and 10V to 100%.
*