Danfoss VLT AQUA High Power Operation Instructions Manual

Also see for vlt aqua: Instructions Design guide Instruction manual Operating instructions Design guide

Contents

20-81 PID Normal/Inverse ControlOption: Function:[0] * Normal[1] InverseNormal [0] causes the frequency converter’s output frequency to decrease when the feedback isgreater than the setpoint reference. This is common for pressure-controlled supply fan and pumpapplications.Inverse [1] causes the frequency converter’s output frequency to increase when the feedback isgreater than the setpoint reference.20-82 PID Start Speed [RPM]Range: Function:0 RPM* [0 - par. 4-13 RPM] When the frequency converter is first started, it initially ramps up to this output speed in Open LoopMode, following the active Ramp Up Time. When the output speed programmed here is reached,the frequency converter will automatically switch to Closed Loop Mode and the PID Controller willbegin to function. This is useful in applications in which the driven load must first quickly accelerateto a minimum speed when it is started.NB!This parameter will only be visible if par. 0-02Motor Speed Unit is set to [0], RPM.20-93 PID Proportional GainRange: Function:0.50 N/A* [0.00 - 10.00 N/A] The proportional gain indicates the number of times the error between the set point and the feed-back signal is to be applied.If (Error x Gain) jumps with a value equal to what is set in par. 20-14Maximum Reference/Feedb. the PID controller will try to change the output speedequal to what is set in par. 4-13Motor Speed High Limit [RPM]/par. 4-14Motor Speed High Limit [Hz] but in practice of course limited by this setting.The proportional band (error causing output to change from 0-100%) can be calculated by means of the formula:( 1Proportional Gain ) × (Max Reference)NB!Always set the desired for par. 20-14Maximum Reference/Feedb. before setting the values for the PID controller in par. group 20-9*.20-94 PID Integral TimeRange: Function:20.00 s* [0.01 - 10000.00 s] Over time, the integrator accumulates a contribution to the output from the PID controller as longas there is a deviation between the Reference/Setpoint and feedback signals. The contribution isproportional to the size of the deviation. This ensures that the deviation (error) approaches zero.Quick response on any deviation is obtained when the integral time is set to a low value. Setting ittoo low, however, may cause the control to become unstable.The value set, is the time needed for the integrator to add the same contribution as the proportionalpart for a certain deviation.If the value is set to 10,000, the controller will act as a pure proportional controller with a P-bandbased on the value set in par. 20-93,Proportional Gain. When no deviation is present, the outputfrom the proportional controller will be 0.5.2.10 22-** MiscellaneousThis group contains parameters used for monitoring water/ wastewater applications.5 How to programme the frequency converter VLT AQUA High Power Operation Instructions126 MG.20.P3.02 - VLT® is a registered Danfoss trademark5