Danfoss VT2800 Series Design Manual

Contents

VLT ® 2800 SeriesProgrammingNB!:If the frequency converter is running a thecurrent limit before the required start frequencyis obtained, the process regulator will not beactivated. For the regulator to be activated anyway, thestart frequency must be lower to the required outputfrequency. This can be done during operation.440 Proces PID proportioanl gain(PROC. PROP. GAIN)Value:0.0 - 10.00 ✭ 0.01Function:The proportional gain indicates the number oftimes the deviation between the setpoint and thefeedback signal is to be applied.Description of choice:Quick regulation is obtained by a high gain, butif the gain is too high, the process may becomeunstable due to overshoot.441 Process PID integration time(PROC. INTEGR. T.)Value:0.01 - 9999.99 (OFF) ✭ OFFFunction:The integrator provides an increasing gain at aconstant error between the reference/setpoint and thefeedback signal. The greater the error, the quickerthe integrator frequency contribution will increase.Theintegral time is the time needed by the integrator tomake the same change as the proportional gain.Description of choice:Quick regulation is obtained at a short integral time.However, this time may become too short, which canmake the process unstable due to overswing. If theintegral time is long, major deviations from the requiredsetpoint may occur, since the process regulator willtake a long time to regulate in relation to a given error.442 Process PID differentiation time(PROC. DIFF. TIME)Value:0.00 (OFF) - 10.00 sec. ✭ 0.00 sec.Function:The differentiator does not react to a constant error.It only makes a gain when an error changes. Thequicker the deviation changes, the stronger the gainfrom the differentiator. The gain is proportional tothe speed at which the deviation changes.Description of choice:Quick regulation is obtained with a long differentiationtime. However, this time may become too long, whichcan make the process unstable due to overswing.443 Process PID diff. gain limit(PROC. DIFF.GAIN)Value:5.0 - 50.0 ✭ 5.0Function:It is possible to set a limit for the differentiator gain.The differentiator gain will increase if there are fastchanges, which is why it can be beneficial to limit thisgain. Thereby a pure differentiator gain is obtainedat slow changes and a constant differentiator gainwhere quick changes to the deviation occur.Description of choice:Select a differentiator gain limit as required.444 Process PID lowpass filter time(PROC FILTER TIME)Value:0.02 - 10.00 ✭ 0.02Function:Noise in the feedback signal is dampened by a firstorder lowpass filter to reduce the noise’s impact onthe process regulation. This can be an advantagee.g. if there is a lot of noise on the signal.Description of choice:Select the required time constant (t). If a time constant(t) of 0.1 s is programmed, the cut-off frequencyfor the lowpass filter will be 1/0.1 = 10 RAD/sec.,corresponding to (10 / 2 x π) = 1.6 Hz. The processregulator will thus only regulate a feedback signalthat varies by a frequency lower than 1.6 Hz. If the✭ = factory setting. () = display text [] = value for use in communication via serial communication portMG.28.E9.02 - VLT is a registered Danfoss trademark 105