Special Operation And Frequency Control; Pid Control (Pr. 127 To Pr. 134, Pr. 575 To Pr. 577) - Mitsubishi Electric FR-A720-0.4K Instruction Manual

Special operation and frequency control

4.25 Special operation and frequency control

Purpose
Perform process control such as pump and air
volume.
Switch between the inverter operation and
commercial power-supply operation to operate.
Increase speed when the load is light.
Frequency control appropriate for the load torque
Frequency setting by pulse train input
Make the motor speed constant by encoder
Avoid overvoltage alarm due to regeneration by
automatic adjustment of output frequency

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

The inverter can be used to exercise 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
*1
130 PID integral time
*1
131 PID upper limit
132 PID lower limit
133 PID action set point
*1
344
PID control
Commercial power supply-
inverter switchover function
Load torque high speed
frequency control
Droop control
Pulse train input
Encoder feedback control
Regeneration avoidance
function
Initial Setting
Value Range
Set the frequency at which the control is automatically
0 to 400Hz
9999 changed to PID control.
9999 Without PID automatic switchover function
10 PID reverse action
11 PID forward action
20 PID reverse action
21 PID forward action
10
50 PID reverse action
51 PID forward action
60 PID reverse action
61 PID forward action
If the proportional band is narrow (parameter setting is small),
the manipulated variable varies greatly with a slight change of
the measured value. Hence, as the proportional band narrows,
0.1 to 1000%
the response sensitivity (gain) improves but the stability
100%
deteriorates, e.g. hunting occurs.
Gain Kp = 1/proportional band
9999 No proportional control
For deviation step input, time (Ti) required for only the integral
(I) action to provide the same manipulated variable as that for
0.1 to 3600s
the proportional (P) action. As the integral time decreases, the
1s
set point is reached earlier but hunting occurs more easily.
9999 No integral control
Set the maximum value. If the feedback value exceeds the
setting, the FUP signal is output. The maximum input (20mA/
0 to 100%
5V/10V) of the measured value (terminal 4) is equivalent to
9999
100%.
9999 No function
Set the minimum value. If the measured value falls below the
setting range, the FDN signal is output. The maximum input
0 to 100%
(20mA/5V/10V) of the measured value (terminal 4) is
9999
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.
Parameter that must be Set
Pr. 127 to Pr. 134,
Pr. 575 to Pr. 577
Pr. 135 to Pr. 139, Pr. 159
Pr. 4, Pr. 5, Pr. 270 to Pr. 274
Pr. 286 to Pr. 288
Pr. 291, Pr. 384 to Pr. 386
Pr. 144, Pr. 285, Pr. 359,
Pr. 367 to Pr. 369
Pr. 882 to Pr. 886
Description
Deviation value signal input
Measured value (terminal 4 )
Set point (terminal 2 or Pr. 133)
Deviation value signal input
(L W
ON ORKS
Measured value, set point input
(L W
ON ORKS
Refer
to Page
344
352
357
359
361
364
366
(terminal 1 )
, CC-Link communication)
, CC-Link communication)