Special Operation And Frequency Control; Pid Control (Pr. 127 To Pr. 134, Pr. 575 To Pr. 577) - Mitsubishi Electric FR-D720-008 Instruction Manual

Special operation and frequency control

4.20 Special operation and frequency control

Purpose
Perform process control such as
pump and air volume.
Dancer control
Avoid overvoltage alarm due to
regeneration by automatic
adjustment of output frequency

4.20.1 PID control (Pr. 127 to Pr. 134, Pr. 575 to Pr. 577)

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 ∗1
PID proportional band
130 ∗1
PID integral time
131 PID upper limit
132 PID lower limit
133 ∗1
PID action set point
134 ∗1
PID differential time
Output interruption
575
detection time
Output interruption
576
detection level
210
Parameter that should be Set
PID control
PID control (dancer control
setting)
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
20 PID reverse action
21 PID forward action
40 PID reverse action
0
41 PID forward action
42 PID reverse action
43 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
For deviation step input, time (Ti) required for only the integral (I) action
0.1 to
to provide the same manipulated variable as that for the proportional (P)
1s
3600s action. As the integral time decreases, the set point is reached earlier
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
100% maximum input (20mA/5V/10V) of the measured value (terminal 4) is
equivalent to 100%.
9999 No function
Minimum frequency
0 to
If the process value falls below the setting range, the FDN signal is
9999
100% output. The maximum input (20mA/5V/10V) of the measured value
(terminal 4) is equivalent to 100%.
9999 No function
0 to 100% Used to set the set point for PID control.
9999
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.
The inverter stops operation if the output frequency after PID operation
0 to
remains at less than the Pr. 576 setting for longer than the time set in Pr.
1s
3600s
575.
9999 Without output interruption function
Set the frequency at which the output interruption processing is
0Hz 0 to 400Hz
performed.
Pr. 127 to Pr. 134, Pr. 575
to Pr. 577
Pr. 44, Pr. 45, Pr. 128 to Pr. 134
Pr. 882, Pr. 883, Pr. 885, Pr. 886
Description
Measured value (terminal 4)
Set value (terminal 2 or Pr. 133)
For dancer control
Addition
set point (Pr. 133),
method: fixed
measured value (terminal 4)
Addition
main speed (frequency command
method: ratio
of the operation mode)
Refer to Page
210
218
224