Danfoss VLT 380-500 V Design Manual

Contents

Danfoss VLT 380-500 V Design Manual Manual pdf 152 page image

Function Parameter SettingSet terminal 53 low voltage:Set terminal 53 high voltage:Set terminal 54 low feedback value:Set terminal 54 high feedback value:Set feedback source:Parameter 6-10 Terminal53 Low VoltageParameter 6-11 Terminal53 High VoltageParameter 6-24 Terminal54 Low Ref./Feedb.ValueParameter 6-25 Terminal54 High Ref./Feedb.ValueParameter 7-20 Process CL Feedback 1Resource0 V10 V-5 °C (23 °F)35 °C (95 °F)[2] analog input 546) Basic PID settings.Process PID normal/inverse. Parameter 7-30 ProcessPID Normal/ InverseControl[0] NormalProcess PID anti wind up. Parameter 7-31 ProcessPID Anti Windup[1] OnProcess PID start speed. Parameter 7-32 ProcessPID Start Speed300 RPMSave parameters to LCP. Parameter 0-50 LCPCopy[1] All to LCPTable 16.6 Example of Process PID Control Set-up16.2.4 Process Controller OptimizationAfter the basic settings have been made, optimize thefollowing:• Proportional gain• Integration time• Differentiation timeIn most processes, the basic settings can be done byfollowing these steps:1. Start the motor.2. Set parameter 7-33 Process PID Proportional Gainto 0.3 and increase it until the feedback signalbegins to vary continuously. Then reduce thevalue until the feedback signal has stabilized.Now lower the proportional gain by 40–60%.3. Set parameter 7-34 Process PID Integral Time to 20s and reduce the value until the feedback signalbegins to vary continuously. Increase theintegration time until the feedback signalstabilizes, followed by an increase of 15–50%.4. Only use parameter 7-35 Process PID DifferentiationTime for very fast-acting systems only (differen-tiation time). The typical value is 4 times the setintegration time. Only use the differentiator whenthe setting of the proportional gain and theintegration time are fully optimized. Make surethat the low-pass filter sufficiently dampens theoscillations on the feedback signal.NOTICEIf necessary, start/stop can be activated several times toprovoke a variation of the feedback signal.16.3 Optimization of PID ControlsSeveral tuning methods can be used to tune the PIDcontrols of the frequency converter. One approach is touse the Ziegler Nichols tuning method.NOTICEDo not use the method described in cases whereoscillations created by marginally stable control settingscan damage applications.The criteria for adjusting the parameters are based onevaluating the system at the limit of stability rather thanon taking a step response. The proportional gain isincreased until continuous oscillations are observed (asmeasured on the feedback), that is, until the systembecomes marginally stable. The corresponding gain (Ku) iscalled the ultimate gain. The period of the oscillation (Pu)(called the ultimate period) is determined as shown inIllustration 16.5.PID Controls VLT® Parallel Drive Modules150 Danfoss A/S © 6/2016 All rights reserved. MG37N1021616