Mitsubishi Electric FR-D720-008 Instruction Manual page 216

Special operation and frequency control
3)PID action
The PI action and PD action are combined to utilize the advantages of both
actions for control.
(Note) PID action is the sum of P, I and D actions.
4)Reverse operation
Increases the manipulated variable (output frequency) if deviation X = (set point - measured value) is positive, and
decreases the manipulated variable if deviation is negative.
Set point
5)Forward action
Increases the manipulated variable (output frequency) if deviation X = (set point - measured value) is negative, and
decreases the manipulated variable if deviation is positive.
Set point
Relationships between deviation and manipulated variable (output frequency)
Positive
Reverse action
Forward action
212
[Heating]
+ X>0
X<0
-
Feedback signal
(measured value)
[Cooling]
+ X>0
X<0
-
Feedback signal
(measured value)
Deviation
Negative
PID
Cold
Increase
Hot
Decrease
Decrease
Too cold
Increase
Hot
Deviation
Set point
Deviation
Measured value
P
action
Time
I action
Time
D action
Time
y=at
action
Time
Deviation
Set point
Measured value
Measured value
Set point
2
+bt+c