Danfoss FC 300 Design Manual

Also see for FC 300: Operating instructions Instruction manual Design guide Design guide Design guide

Contents

Danfoss FC 300 Design Manual Manual pdf 29 page image

Speed PID ControlThe table shows the control configurations where the Speed Control is active.Par. 1-00 Configura-tion ModePar. 1-01 Motor Control PrincipleU/f VVCplus Flux Sensorless Flux w/ enc. feedb[0] Speed open loop Not Active Not Active ACTIVE N.A.[1] Speed closed loop N.A. ACTIVE N.A. ACTIVE[2] Torque N.A. N.A. N.A. Not Active[3] Process Not Active ACTIVE ACTIVENote: ìN.A.î means that the specific mode is not available at all. ìNot Activeî means that the specificmode is available but the Speed Control is not active in that mode.Note: The Speed Control PID will work under the default parameter setting, but tuning the parametersis highly recommended to optimize the motor control performance. The two Flux motor control principlesare specially dependant on proper tuning to yield their full potential.The following parameters are relevant for the Speed Control:Parameter Description of functionFeedback Par. 7-00 Select from which input the Speed PID should get its feedback.Proportional Gain Par.7-02The higher the value - the quicker the control. However, too high value maylead to oscillations.Integral Time Par. 7-03 Eliminates steady state speed error. Lower value means quick reaction. How-ever, too low value may lead to oscillations.Differentiation Time Par.7-04Provides a gain proportional to the rate of change of the feedback. A settingof zero disables the differentiator.Differentiator Gain LimitPar. 7-05If there are quick changes in reference or feedback in a given application -which means that the error changes swiftly - the differentiator may soonbecome too dominant. This is because it reacts to changes in the error. Thequicker the error changes, the stronger the differentiator gain is. The differ-entiator gain can thus be limited to allow setting of the reasonable differen-tiation time for slow changes and a suitably quick gain for quick changes.Lowpass Filter Time Par.7-06A low-pass filter that dampens oscillations on the feedback signal and im-proves steady state performance. However, too large filter time will deterio-rate the dynamic performance of the Speed PID control.Practical settings of Par 7-06 taken from the number of pulses per revolutionon from encoder (PPR):Encoder PPR Par. 7-06512 10 ms1024 5 ms2048 2 ms4096 1 msBelow is given an example of how to programme the Speed Control:In this case the Speed PID Control is used tomaintain a constant motor speed regardless of thechanging load on the motor.The required motor speed is set via a potentiom-eter connected to terminal 53. The speed range is0 - 1500 RPM corresponding to 0 - 10V over thepotentiometer.Starting and stopping is controlled by a switchconnected to terminal 18.The Speed PID monitors the actual RPM of themotor by using a 24V (HTL) incremental encoderas feedback. The feedback sensor is an encoder(1024 pulses per. revolution) connected to termi-nals 32 and 33.In the parameter list below it is assumed that all other parameters and switches remain at their defaultsetting.FC 300 Design GuideIntroduction to FC 300MG.33.B7.02 - VLT is a registered Danfoss trademark 29