Danfoss VLT FC 102 Programming Manual

Also see for VLT HVAC Drive FC 102: Operating instructions Service guide Programming guide Installation guide Installation guide

Contents

20-91 PID Anti WindupOption: Function:NOTICEOption [1] On is activatedautomatically, if 1 of thefollowing options is selected inparameters in parameter group21-** Ext. Closed Loop: [0]Normal, [X] Enabled Ext CLXPID.[0] Off The integrator continues to changevalue also after output has reached1 of the extremes. This canafterwards cause a delay of changeof the output of the controller.[1] * On The integrator is locked if theoutput of the built-in PID controllerhas reached 1 of the extremes(minimum or maximum value) andtherefore is not able to add furtherchanges to the value of the processparameter controlled. This allowsthe controller to respond morequickly when it can control thesystem again.20-93 PID Proportional GainRange: Function:0.50* [0 - 10 ] NOTICEAlways set the desired valuefor parameter 20-14 MaximumReference/Feedb. before settingthe values for the PIDcontroller in parameter group20-9* PID Controller.The proportional gain indicates thenumber of times the error betweenthe setpoint and the feedbacksignal is to be applied.If (Error x Gain) jumps with a value equal to what is set inparameter 20-14 Maximum Reference/Feedb., the PIDcontroller tries to change the output speed equal to whatis set in parameter 4-13 Motor Speed High Limit [RPM]/parameter 4-14 Motor Speed High Limit [Hz]. However, theoutput speed is limited by this setting.Calculate the proportional band (error causing output tochange from 0–100%) can be calculated with the formula:1Proportional Gain × Max Reference20-94 PID Integral TimeRange: Function:20 s* [0.01 - 10000s]The integrator accumulates a contri-bution to the output from the PIDcontroller as long as there is adeviation between the reference/setpoint and feedback signals. Thecontribution is proportional to thesize of the deviation. This ensuresthat the deviation (error)approaches zero.Quick response on any deviation isobtained when the integral time isset to a low value. Setting it toolow, however, may cause thecontrol to become unstable.The value set is the time neededfor the integrator to add the samecontribution as the proportional fora certain deviation.If the value is set to 10000, thecontroller acts as a pure propor-tional controller with a P-bandbased on the value set inparameter 20-93 PID ProportionalGain. When no deviation is present,the output from the proportionalcontroller is 0.20-95 PID Differentiation TimeRange: Function:0 s* [0 - 10 s] The differentiator monitors the rateof change of the feedback. If thefeedback is changing quickly, itadjusts the output of the PIDcontroller to reduce the rate ofchange of the feedback. Quick PIDcontroller response is obtainedwhen this value is large. However, iftoo large of a value is used, thefrequency converter’s outputfrequency may become unstable.Differentiation time is useful insituations where extremely fastfrequency converter response andprecise speed control are required.It can be difficult to adjust this forproper system control. Differen-tiation time is not commonly usedin HVAC applications. Therefore, it isbest to leave this parameter at 0 orOFF.Parameter Descriptions Programming GuideM0010001 Danfoss A/S © 10/2019 All rights reserved. 1873 3