Danfoss VLT FC 360 Design Manual

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Contents

Danfoss VLT FC 360 Design Manual Manual pdf 16 page image

2.3 Control Structures2.3.1 Control PrincipleA frequency converter rectifies AC voltage from mains intoDC voltage, after which this DC voltage is converted into aAC current with a variable amplitude and frequency.The motor is supplied with variable voltage/current andfrequency, which enables infinitely variable speed controlof three-phased, standard AC motors and permanentmagnet synchronous motors.2.3.2 FC 360 ControlsThe frequency converter is capable of controlling eitherthe speed or the torque on the motor shaft. Setting1-00 Configuration Mode determines the type of control.Speed controlThere are two types of speed control:• Speed closed loop PID control requires a speedfeedback to an input. A properly optimised speedclosed loop control will have higher accuracythan a speed open loop control.Selects which input to use as speed PID feedback in7-00 Speed PID Feedback Source.Torque controlThe torque control function is used in applications wherethe torque on motor output shaft is controlling theapplication as tension control. Torque control can beselected in 1-00 Configuration Mode. Torque setting is doneby setting an analog, digital or bus controlled reference.When running torque control it is recommended to makea full AMA procedure as the correct motor data are of highimportance for optimal performance.• Open loop in VVCplus mode. The function is usedin mechanical robust applications, but theaccuracy is limited. Open loop torque functionworks for two directions. The torque is calculatedon basic of current measurement internal in thefrequency converter. See Application ExampleTorque open LoopSpeed/torque referenceThe reference to these controls can either be a singlereference or be the sum of various references includingrelatively scaled references. The handling of references isexplained in detail later in this section.Product Overview VLT® AutomationDrive FC 360 Design Guide14 MG06B202 - VLT® is a registered Danfoss trademark22