MX2 Quick Start Guide 33
PROGRAMMING MX2
3.20 PID Function
When enabled, the built-in PID loop calculates an ideal inverter output value that cause the loop feedback process variable (PV)
to move closer to the set point value (SP). The frequency command is used as SP and the PID loop algorithm will read the analog
input for the process variable and calculate the proper inverter output to reach it.
In standard operation, inverter uses a reference source selected by A001 for the output frequency which may be a fixed or vari-
able value. To enable PID operation is necessary to set A071 to “01” and this will cause the inverter to calculate the target fre-
quiency or set point. This presents some advantges like potential energy saving and direct control over the process variable
instead of the motor speed.
3.21 Current limitation functions
Overload Restriction reduce the output frequency while motoring or increase
it during regeneration to restrict the overload when the output current exceeds
a certain limit. You can adjust the inverter to apply overload retriction only
during constant speed allowing higher currents for acceleration.
Additionally two separate set of parameters are avaiable and is possible to
choose between them by intelligent input terminal “39: OLR”.
Parameter Parameter name Description
A071 PID enable 00... PID Disable
01... PID Enable
02... PID Enable with reverse output
A072 PID proportional gain Proportional gain has a range of 0.00 to 25.00
A073 PID integral time constant Integral time constant has a range of 0.0 to 3600 seconds
A074 PID derivative time constant Derivative time constant has a range of 0.0 to 100 seconds
A075 PV scale conversion Process Variable (PV), scale factor (multiplier), range of 0.01 to 99.99
A076 PV source Selects source of Process Variable (PV), option codes:
00.. [OI] terminal (current in)
01.. [O] terminal (voltage in)
02 .. ModBus network
03.. Pulse train input 10 Calculate function output
A077 Reverse PID action Two option codes: 00 PID input = SP-PV 01 PID input = -(SP-PV)
A078 PID output limit Sets the limit of PID output as percent of full scale, range is 0.0 to 100.0%
A079 PID feed forward selection 00... Disabled
01... [O] terminal (voltage in)
02... [OI] terminal (current in)
A156 PID sleep function action threshold Sets the threshold for the action, set range 0.0~400.0 Hz
A157 PID sleep function action delay time Sets the delay time for the action, set range 0.0~25.5 sec
A071 PID enable 00... PID Disable
01... PID Enable
02... PID Enable with reverse output
Setpoint
SP
+
Error Freq.
Inverter Motor
Sensor
Process Variable (PV)
PV
External
Process
PID
Calculation
Motor
current
Restriction area
B022
0
t
Output
frequency
0
t
B023
Regenerating
Powering
B023
I129E-EN-02+MX2+QuickStartGuide.book Seite 33 Mittwoch, 7. November 2012 1:54 13
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