Danfoss VLT 2800 Design Manual

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Contents

Danfoss VLT 2800 Design Manual Manual pdf 70 page image

4.2 Load and Motor4.2.1 ConfigurationSelection of configuration and torque characteristics has aneffect on which parameters can be seen in the display. If[0] Open loop is selected, all parameters relating to PIDregulation is filtered out. This means that the user onlysees the parameters that are relevant for a givenapplication.100 ConfigurationValue:Speed control, open loop(SPEED OPEN LOOP) [0]Speed control, closed loop(SPEED CLOSED LOOP) [1]Process control, closed loop(PROCESS CLOSED LOOP) [3]Function:This parameter is used to select the configuration to whichthe frequency converter is to be adapted. This makesadaptation to a given application simple, since theparameters not used in a given configuration are hidden(not active).Description of choice:If [0] Speed control, open loop is selected, normal speedcontrol is obtained (without feedback signal) withautomatic load and slip compensation to ensure aconstant speed at varying loads. Compensations are active,but may be disabled in parameter 134 Load compensationand parameter 136 Slip compensation as required.If [1] Speed control, closed loop is selected, better speedaccuracy is obtained. Add feedback signal, and set the PIDregulator in parameter group 400 Special functions.If [3] Process control, closed loop is selected, the internalprocess regulator is activated to enable precise control of aprocess in relation to a given process signal. The processsignal can be set to the relevant process unit or as apercentage. Add feedback signal from the process and setthe process regulator in parameter group 400 Specialfunctions. Process closed loop is not active if a DeviceNetcard is mounted and Instance 20/70 or 21/71 is selected inparameter 904 Instance types.101 Torque characteristicValue:Constant torque(Constant torque) [1]Variable torque low(torque: low) [2]Variable torque medium(torque: med) [3]Variable torque high(torque: high) [4]Variable torque low with CT start(VT LOW CT START) [5]Variable torque medium with CT start(VT MED CT START) [6]Variable torque high with CT start(VT HIGH CT START) [7]Special motor mode(Special motor mode) [8]CT = Constant torqueFunction:Use this parameter to adapt the U/f ratio of the frequencyconverter to the torque characteristic of the load. Seeparameter 135 U/f ratio.Description of choice:If [1] Constant torque is selected, a load-dependent U/fcharacteristic is obtained, in which output voltage andoutput frequency are increased at increasing loads tomaintain constant magnetisation of the motor.Select [2] Variable torque low , [3] Variable torque medium or[4] Variable torque high, if the load is square (centrifugalpumps, fans).Select [5] Variable torque - low with CT start , [6] Variabletorque - medium with CT start or [7] Variable torque - highwith CT start if a greater breakaway torque is needed thancan be achieved with the 3 first characteristics.Illustration 4.2 Torque CharacteristicsSelect [8] Special motor mode if a special U/f setting isneeded that is to be adapted to the present motor. Thebreak points are set in parameters 423-428 Voltage/frequency.NOTICELoad and slip compensation are not active if variabletorque or special motor mode have been selected.Programming Design Guide68 Danfoss A/S © Rev. May/2014 All rights reserved. MG27E40244