Danfoss VT2800 Series Design Manual

Contents

VLT ® 2800 SeriesNB!:Parameters 417-421 are only used, if inparameter 100 Configuration the selectionmade is Speed regulation, closed loop [1].417 Speed PID proportional gain(SPEED PROP GAIN)Value:0.000 (OFF) - 1.000 ✭ 0.010Function:Proportional gain indicates how many times thefault (deviation between the feedback signal andthe setpoint) is to be amplified.Description of choice:Quick regulation is obtained at high amplification,but if the amplification is too high, the process maybecome unstable in the case of overshooting.418 Speed PID integral time(SPEED INT. TIME)Value:20.00 - 999.99 ms (1000 = OFF) ✭ 100 msFunction:The integral time determines how long the PIDregulator takes to correct the error. The greaterthe error, the quicker the integrator frequencycontribution will increase. The integral time is thetime the integrator needs to achieve the samechange as the proportional amplification.Description of choice:Quick regulation is obtained through a short integraltime. However, if this time is too short, it can makethe process unstable. If the integral time is long,major deviations from the required reference mayoccur, since the process regulator will take longto regulate if an error has occurred.419 Speed PID differential time(SPEED DIFF. TIME)Value:0.00 (OFF) - 200.00 ms ✭ 20.00 msFunction:The differentiator does not react to a constant error.It only makes a contribution when the error changes.The quicker the error changes, the stronger the gainfrom the differentiator will be. The contribution isproportional to the speed at which errors change.Description of choice:Quick control is obtained by a long differentialtime. However, if this time is too long, it can makethe process unstable. When the differential timeis 0 ms, the D-function is not active.420 Speed PID D- gain limit(SPEED D-GAIN LIM)Value:5.0 - 50.0 ✭ 5.0Function:It is possible to set a limit for the gain provided by thedifferentiator. Since the D-gain increases at higherfrequencies, limiting the gain may be useful. Thisenables obtaining a pure D-gain at low frequenciesand a constant D-gain at higher frequencies.Description of choice:Select the required gain limit.421 Speed PID lowpass filter time(SPEED FILT. TIME)Value:20 - 500 ms ✭ 100 msFunction:Noise in the feedback signal is dampened by a firstorder lowpass filter to reduce the noise’s impact on theregulation. This might be an advantage, e.g. if there isa great amount of noise on the signal. See drawing.✭ = factory setting. () = display text [] = value for use in communication via serial communication portMG.28.E9.02 - VLT is a registered Danfoss trademark102