ABB DCS 500B Description

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ABB DCS 500B Description Manual pdf 45 page image

Functional Software descriptionDCS 500 Software Description 37• Torque Reference The function of the torque reference chain is to form a desired ref-erence for the current regulation.TORQ_REF_SELECTION function blockAn external torque reference can be connected via analog inputs.AI2 function block is connected to [TREF A] (2401) in the standardprogram, and this input contains a filter controlled by parameterTREF A FTC (2402) (1000 = 1s), 0 = not in use.[TREF B] (2404) input is another torque reference input, whichcontains the ramp generator function controlled by parameterTREF B SLOPE (2405) (1000 = 1s), 0 = not in use.Torque Refer-ence ScalingThe value 4000 is equal to nominal torque of the DC-motor (TN).Therefore the analog input must be scaled according to this value.For example, an external torque reference -10V...+10 V is con-nected to analog input AI2 and the torque reference should be-100%...+100% of the motor nominal torque. The parameter set-tings are:AI2 CONV MODE (107) = 1AI2 HIGH VALUE (108) = 4000AI2 LOW VALUE (109) = -4000Load sharing inMaster / FollowerApplicationThe load of the follower drive can be adjusted by means of input[LOAD SHARE] (2403) to the desired value by the applicationfunction blocks. The default value is 100 % = 4000.The output OUT (12401) is calculated:[TREF A] x [LOAD SHARE] / 4000 + [TREF B]Output Limitation The final torque reference before limitation is a sum of a [TREF A]multiplied by [LOAD SHARE] and [TREF B].The output OUT (12401) can be limited by internal signals [TREFTORQMAX1] and [TREF TORQMIN1] in the function blockTORQUE / CURRENT LIMITATION.TORQUE/CURRENT_LIMITATION functionblockTorque / Current Limitation function block consist of limitation cir-cuits for torque and current references and gear backlash compen-sation.Current Limita-tionsThe limitation of armature current is based on fixed current limit pa-rameters and on limits which are the function of the actual speed.There is a function block with given points of speed and maximumcurrent on these points. Finally the current limit selection is basedon a maximum/minimum selection of these two limitation sources.