Mitsubishi Electric FR-F740 EC Instruction Manual page 498

PID control
Take caution when the following condition is satisfied because the inverter recognizes the de-
viation value as a negative (positive) value even though a positive (negative) deviation is given:
To perform a reverse operation, set the forward operation in Pr. 128. To perform a forward op-
eration, set the reverse operation in Pr. 128. In this case, the PID output shutoff release level is
(1000 – Pr. 577 [%]).
Reverse operation
Forward operation
PID output shutoff release
level
Tab. 6-116: Pr. 128 setting depending on Pr. 934 and Pr. 935 settings
Example Set the following:
Pr. 934 = "500" and 20% (4 mA is applied), Pr. 935 = "100" and 100% (20 mA is applied).
When the set point = 400 and the measured value = 360, the deviation is +40 (>0), but the
inverter recognizes the deviation with –10% (<0). Because of this, operation amount does
not increase in the reverse operation setting.
The operation amount increases when the forward operation is set. To perform PID output
shutoff release at deviation of +40 or higher, set Pr. 577 = "960".
Set point
Measured
value
Values in parentheses indicate the deviation
value which the inverter can recognise.
6 - 348
Pr. 934 > Pr. 935
Pr. 934 < Pr. 935 (normal setting)
Reverse operation setting
to Pr. 128
Forward operation setting
to Pr. 128
Pr. 577 – 1000 [%]
500
Deviation
→
400
+40
360
100
0
20%
(0%) (25%)(35%)
Deviation –10%
Reverse operation
Forward operation
PID output shutoff release
level
Fig. 6-187:
Illustration of the deviation value for the
example
100%
(100%)
Parameter
Pr. 934 >= Pr. 935
Forward operation setting
to Pr. 128
Reverse operation setting
to Pr. 128
1000 – Pr. 577 [%]
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