Danfoss VT2800 Series Design Manual

Contents

VLT ® 2800 Seriesfeedback signal varies by a higher frequency than 1.6Hz, it will be dampened by the lowpass filter.445 Flying start(FLYINGSTART)Value:✭Off (DISABLE) [0]OK - same direction(OK-SAME DIRECTION) [1]OK - both directions(OK-BOTH DIRECTIONS) [2]DC brake and start(DC-BRAKE BEF. START) [3]Function:This function makes it possible to ’catch’ a rotatingmotor shaft, which is no longer controlled by thefrequency converter, e.g. because of a mainsdrop-out. The function is activated each time a startcommand is enabled. For the frequency converterto be able to ’catch’ the rotating motor shaft, themotor speed must be lower than the frequencythat corresponds to the frequency in parameter202 Output frequency, high limit, f MAX.Description of choice:Select Disable [0] if this function is not required.Select OK - same direction [1] if the motor shaftis only able to rotate in the same direction whencutting in. OK - same direction [1] should beselected if in parameter 200 Output frequency rangea selection has been of Clockwise only .Select OK - both directions [2] if the motor is ableto rotate in both directions when cutting in.Select DC brake and start [3] if the frequency converteris to be able to brake the motor using the DC brakefirst, followed by start. It is assumed that parameters126-127/132 DC brake are enabled. In the caseof higher ’Windmilling’ (rotating motor) effects, thefrequency converter is not able to ’catch’ a rotatingmotor without selecting DC brake and start .Limitations:- Too low inertia will lead to load acceleration, whichcan be dangerous or prevent correct catching of arotating motor. Use the DC brake instead.- If the load is driven, e.g. by ’Windmilling’(rotating motor) effects, the unit may cutout because of overvoltage.- Flying start does not work at lower valuesthan 250 rpm.451 Speed PID feedforward factor(FEEDFORWARD FACT)Value:0 - 500 % ✭ 100 %Function:This parameter is only active if in parameter 100Configuration the selection made is Speed regulation,closed loop. The FF function sends a larger or smallerpart of the reference signal outside the PID controllerin such a way that the PID controller only has aninfluence on part of the control signal. Any changeto the set point will thus have a direct effect on themotor speed. The FF factor provides high dynamismwhen changing the set point and less overswing.Description of choice:The required % value can be selected in the intervalf MIN - f MAX . Values over 100 % are used if theset point variations are only small.452 Controller range(PID CONTR. RANGE)Value:0 - 200 % ✭ 10 %Function:This parameter is only active if in parameter100 Configuration the selection made is Speedregulation, closed loop.The controller range (bandwidth) limits the output fromthe PID controller as a % of motor frequency f M,N .Description of choice:The required % value can be selected for motorfrequency f M,N . If the controller range is reduced thespeed variations will be less during initial tuning.456 Brake Voltage Reduce(BRAKE VOL REDUCE)Value:0 - 25 V if 200V device ✭ 00 - 50 V if 400V device ✭ 0✭ = factory setting. () = display text [] = value for use in communication via serial communication portMG.28.E9.02 - VLT is a registered Danfoss trademark106