Danfoss VLT AutomationDrive FC 300 Design Manual

Also see for VLT AutomationDrive FC 301: Programming guide Installation guide Operating guide Installation guide Design guide

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Danfoss VLT AutomationDrive FC 300 Design Manual Manual pdf 42 page image

FC 300 Design GuideIntroduction to FC 300Type of Control Proportional Gain Integral Time Differentiation TimePI-control 0.45 * K u 0.833 * P u -PID tight control 0.6 * K u 0.5 * P u 0.125 * P uPID some overshoot 0.33 * K u 0.5 * P u 0.33 * P uTable 1: Ziegler Nichols tuning for regulator, based on a stability boundary.Experience has shown that the control setting according to the Ziegler Nichols rule providesa good closed-loop response for many systems. The process operator can perform finaltuning of the control iteratively to yield satisfactory control.Step-by-step:Step 1: Select only Proportional Control, meaning that the Integral time is selected to themaximum value, while the differentiation time is selected to zero.Step 2: Increase the value of the proportional gain until the point of instability is reached(sustained oscillations) and the critical value of gain, K u, is reached.Step 3: Measure the period of oscillation to obtain the critical time constant, P u.Step 4: Use the table above to calculate the necessary PID control parameters." Internal Current RegulatorThe adjustable frequency drive features an integral current limit regulator which is activated when themotor current, and thus the torque, is higher than the torque limits set in par. 4-16 and 4-17.When the adjustable frequency drive is at the current limit during motor operation or regenerativeoperation, the adjustable frequency drive will try to get below the preset torque limits asquickly as possible without losing control of the motor.While the current regulator is active, the adjustable frequency drive can only be stopped by means ofa digital terminal if set to Coast, inverse [2] or Coast and Reset, inverse [3]. Other signals on terminals18-33 will not be active until the adjustable frequency drive is no longer near the current limit." Programming of Torque Limit and StopIn applications with an external electromechanical brake, such as hoisting applications,it is possible to stop the adjustable frequency drive via a "standard" stop command andsimultaneously activate the external electromechanical brake.The example given below illustrates the programming of adjustable frequency drive connections.The external brake can be connected to relay 1 or 2, see paragraph Control of MechanicalBrake. Program terminal 27 to Coast, inverse [2] or Coast and Reset, inverse [3], andprogram terminal 29 to Torque limit & stop [27].Description:If a stop command is active via terminal 18 and the adjustable frequency drive is notat the torque limit, the motor ramps down to 0 Hz.If the adjustable frequency drive is at the torque limit and a stop command is activated, terminal 42Output (programmed to Torque limit and stop [27]) is activated. The signal to terminal 27 l changesfrom "logic 1" to "logic 0", and the motor starts to coast, thereby ensuring that the hoist stops evenif the drive itself cannot handle the required torque (i.e. due to excessive overload).42 MG.33.B3.22 - VLT is a registered Danfoss trademark