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Special operation and frequency control
4.21 Special operation and frequency control
Purpose
Perform process control such as
pump and air volume.
Avoid overvoltage alarm due to
regeneration by automatic
adjustment of output frequency
4.21.1 PID control (Pr. 127 to Pr. 134, Pr. 553, Pr. 554, Pr. 575 to Pr. 577, C42 to C45)
The inverter can be used to perform process control, e.g. flow rate, air volume or pressure.
The terminal 2 input signal or parameter setting is used as a set point and the terminal 4 input signal used as a
feedback value to constitute a feedback system for PID control.
Parameter
Name
Number
PID control automatic
127
switchover frequency
128
PID action selection
129
PID proportional band
130
PID integral time
131
PID upper limit
132
PID lower limit
133
PID action set point
134
PID differential time
553
PID deviation limit
PID signal operation
554
selection
Output interruption
575
detection time
Output interruption
576
detection level
Output interruption
577
cancel level
250
Parameter that should be Set
PID control
Regeneration avoidance
function
Initial
Setting
Value
Range
0 to 400Hz Frequency at which the control is automatically changed to PID control.
9999
9999
Without PID automatic switchover function
0
PID action is not performed
0
20
PID reverse action
21
PID forward action
If the proportional band is narrow (parameter setting is small), the
manipulated variable varies greatly with a slight change of the
0.1 to
measured value. Hence, as the proportional band narrows, the
100%
1000%
response sensitivity (gain) improves but the stability deteriorates, for
example, hunting occurs. Gain Kp= 1/proportional band
9999
No proportional control
When deviation step is input, time (Ti) is the time required for integral (I)
0.1 to
action to provide the same manipulated variable as the proportional (P)
1s
action. As the integral time decreases, the set point is reached earlier
3600s
but hunting occurs more easily.
9999
No integral control.
Maximum value
0 to
If the feedback value exceeds the setting, the FUP signal is output. The
9999
maximum input (20mA/5V/10V) of the measured value (terminal 4) is
100%
equivalent to 100%.
9999
No function
Minimum frequency
0 to
If the measured value falls below the setting range, the FDN signal is
9999
output. The maximum input (20mA/5V/10V) of the measured value
100%
(terminal 4) is equivalent to 100%.
9999
No function
0 to
Used to set the set point for PID control.
9999
100%
9999
Terminal 2 input is the set point.
For deviation ramp input, time (Td) is required for providing only the
0.01 to
manipulated variable for the proportional (P) action. As the differential
9999
10s
time increases, greater response is made to a deviation change.
9999
No differential control.
0 to
Y48 signal is output when the absolute value of deviation amount
100.0%
9999
exceeds the deviation limit value.
9999
No function
Select the operation to be performed at the detection of upper, lower,
0 to 3,
0
and deviation limit for the measured value input. The operation for PID
10 to 13
output suspension function can be selected.
0 to
The inverter stops operation if the output frequency after PID operation
1s
3600s
remains at less than the Pr. 576 setting for longer than the time set in Pr. 575.
9999
Without output interruption function
Set the frequency at which the output interruption processing is
0Hz
0 to 400Hz
performed.
900 to
Set the level (Pr. 577 minus 1000%) at which the PID output interruption
1000%
function is canceled.
1100%
Pr. 127 to Pr. 134, Pr. 553, Pr. 554,
Pr. 575 to Pr. 577, C42 to C45
Pr. 882, Pr. 883, Pr. 885, Pr. 886
Description
Measured value (terminal 4)
Set value (terminal 2 or Pr. 133)
Refer to Page
250
262
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