Danfoss VLT AQUA Drive FC 202 Design Manual

Also see for VLT AQUA Drive FC 202: Service guide Installation guide Installation guide Operating guide Installation guide

Contents

11 Basic Operating Principles of a DriveThis chapter provides an overview of the primaryassemblies and circuitry of a Danfoss drive. It describes theinternal electrical and signal processing functions. Adescription of the internal control structure is alsoincluded.11.1 Description of OperationA drive is an electronic controller that supplies a regulatedamount of AC power to a 3-phase inductive motor. Bysupplying variable frequency and voltage to the motor, thedrive varies the motor speed or maintains a constantspeed as the load on the motor changes. Also, the drivecan stop and start a motor without the mechanical stressassociated with a line start.In its basic form, the drive can be divided into thefollowing 4 main areas:RectifierThe rectifier consists of SCRs or diodes that convert 3-phase AC voltage to pulsating DC voltage.DC link (DC bus)The DC-link consists of inductors and capacitor banks thatstabilize the pulsating DC voltage.InverterThe inverter uses IGBTs to convert the DC voltage tovariable voltage and variable frequency AC.ControlThe control area consists of software that runs thehardware to produce the variable voltage that controls andregulates the AC motor.L1L2L3T1T2T31 2 3130BF777.101 Rectifier (SCR/diodes)2 DC link (DC bus)3 Inverter (IGBTs)Illustration 11.1 Internal Processing11.2 Drive ControlsThe following processes are used to control and regulatethe motor:• User input/reference.• Feedback handling.• User-defined control structure.- Open loop/closed-loop mode.- Motor control (speed, torque, orprocess).• Control algorithms (VVC+, flux sensorless, fluxwith motor feedback, and internal current controlVVC+).11.2.1 User Inputs/ReferencesThe drive uses an input source (also called reference) tocontrol and regulate the motor. The drive receives thisinput either• Manually via the LCP. This method is referred toas local [Hand On].• Remotely via analog/digital inputs and variousserial interfaces (RS485, USB, or an optionalfieldbus). This method is referred to as remote[Auto On] and is the default input setting.Active referenceThe term active reference refers to the active input source.The active reference is configured inparameter 3-13 Reference Site. See Illustration 11.2 andTable 11.1.For more information, see the programming guide.RemotereferenceLocalreference(Auto On)(Hand On)Linked to hand/autoLocalRemoteReference130BA245.12LCP keys:(Hand On), (Off ),and (Auto On)P 3-13 Reference SiteIllustration 11.2 Selecting Active ReferenceBasic Operating Principles ... Design GuideMG22B102 Danfoss A/S © 05/2017 All rights reserved. 9911 11