VLT ® 2900 Series The integrator provides an increasing gain at a con- stant error between the reference/setpoint and the feedback signal. The greater the error, the quicker the integrator frequency contribution will increase.The in- tegral time is the time needed by the integrator to make the same change as the proportional gain. 0.02 - 10.00 0.02 Noise in the feedback signal is dampened by a first order lowpass filter to reduce the noise's impact on the process regulation. This can be an advantage e.g. if there is a lot of noise on the signal. Quick regulation is obtained at a short integral time.
However, this time may become too short, which can make the process unstable due to overswing. If the in- tegral time is long, major deviations from the required setpoint may occur, since the process regulator will take a long time to regulate in relation to a given error. Select the required time constant (t). If a time constant (t) of 0.1 s is programmed, the cut-off frequency for the lowpass filter will be 1/0.1 = 10 RAD/sec., correspond- ing to (10 / 2 x π ) = 1.6 Hz. The process regulator will thus only regulate a feedback signal that varies by a frequency lower than 1.6 Hz. If the feedback signal varies by a higher frequency than 1.6 Hz, it will be dampened by the lowpass filter.
0.00 (OFF) - 10.00 sec. 0.00 sec. The differentiator does not react to a constant error. It only makes a gain when an error changes. The quicker the deviation changes, the stronger the gain from the differentiator. The gain is proportional to the speed at which the deviation changes. Programming Off (DISABLE) [0] OK - same direction (OK-same direction) [1] Quick regulation is obtained with a long differentiation time. However, this time may become too long, which can make the process unstable due to overswing. OK - both directions (OK-both directions) [2] DC brake and start (DC-BRAKE BEF.
START) [3] This function makes it possible to 'catch' a rotating motor shaft, which is no longer controlled by the fre- quency converter, e.g. because of a mains drop-out. The function is activated each time a start command is enabled. For the frequency converter to be able to 'catch' the rotating motor shaft, the motor speed must be lower than the frequency that corresponds to the frequency in parameter 202 Output frequency, high limit, f MAX . 5.0 - 50.0 5.0 It is possible to set a limit for the differentiator gain. The differentiator gain will increase if there are fast changes, which is why it can be beneficial to limit this gain.
Thereby a pure differentiator gain is obtained at slow changes and a constant differentiator gain where quick changes to the deviation occur. Select Disable [0] if this function is not required. Select a differentiator gain limit as required. Select OK - same direction [1] if the motor shaft is only able to rotate in the same direction when cutting in. OK - same direction [1] should be selected if in parameter = factory setting, () = display text, [] = value for use in communication via serial communication port MG.29.A3.02 - VLT ® is a registered Danfoss trademark 51 Function: 444 Process PID lowpass filter time (proc filter time) Value: Function: Description of choice:
Description of choice: 442 Process PID differentiation time (PROC. DIFF. time) Value: Function: 445 Flying start (flyingstart) Value: Description of choice: 443 Process PID diff. gain limit (PROC. DIFF.GAIN) Value: Function: Function: Description of choice: Description of choice: