Mitsubishi Electric FR-A520-0.4K -55K Instruction Manual page 138

2) PD action
A combination of proportional control action (P) and differential control action (D) for providing a
manipulated variable in response to deviation speed to improve the transient characteristic.
[Operation example for proportional changes of process value]
Note: PD action is the sum of P and D actions.
3) PID action
The PI action and PD action are combined to utilize the advantages of both actions for control.
Note: The PID action is the sum of P and I and D actions.
4) Reverse action
Increases the manipulated variable (output frequency) if deviation X (set point - process value) is positive,
and decreases the manipulated variable if deviation is negative.
[Heating]
+
Set point
Process value
5) Forward action
Increases the manipulated variable (output frequency) if deviation X (set point - process value) is negative,
and decreases the manipulated variable if deviation is positive.
[Cooling]
+
Set point
Process value
Relationships between deviation and manipulated variable (output frequency)
Deviation
Positive
Ò
Reverse action
Ô
Forward action
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X>0
Cold → fi up
Hot → fi down
X<0
-
X>0
Too cold → fi down
→ fi up
Hot
X<0
-
Negative
Ô
Ò
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PARAMETERS
Set point
Deviation
Process
value
P action
Time
D action
Time
PD action
Time
Deviation
Set point
Process value
Process value
Set point
Deviation