DC MOTOR DRIVES (MEP 1422)

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DC MOTOR DRIVES (MEP 1422). Dr. Nik Rumzi Nik Idris Department of Energy Conversion FKE, UTM. Contents. Introduction Trends in DC drives Principles of DC motor drives Modeling of Converters and DC motor Phase-controlled Rectifier DC-DC converter (Switch-mode) Modeling of DC motor - PowerPoint PPT Presentation

Text of DC MOTOR DRIVES (MEP 1422)

  • DC MOTOR DRIVES(MEP 1422)Dr. Nik Rumzi Nik IdrisDepartment of Energy ConversionFKE, UTM

  • ContentsIntroductionTrends in DC drivesPrinciples of DC motor drivesModeling of Converters and DC motorPhase-controlled RectifierDC-DC converter (Switch-mode)Modeling of DC motorClosed-loop speed controlCascade Control StructureClosed-loop speed control - an exampleTorque loopSpeed loopSummary

  • INTRODUCTIONDC DRIVES: Electric drives that use DC motors as the prime moversDominates variable speed applications before PE converters were introducedDC motor: industry workhorse for decadesWill AC drive replaces DC drive ?Predicted 30 years agoAC will eventually replace DC at a slow rateDC strong presence easy control huge numbers

  • IntroductionDC MotorsSeveral limitations:Advantage: Precise torque and speed control without sophisticated electronicsRegular MaintenanceExpensiveHeavySpeed limitationsSparking

  • IntroductionDC Motors - 2 pole

  • IntroductionDC Motors - 2 poleMechanical commutator to maintain armature current directionArmature mmf produces flux which distorts main flux produce by fieldArmature reaction

  • IntroductionFlux at one side of the pole may saturate Zero flux region shifted Flux saturation, effective flux per pole decreases Armature reaction

  • Introduction

  • Introduction

  • IntroductionRequires variable DC supply

  • IntroductionTeRequires variable DC supply

  • IntroductionTeRequires variable DC supplyConstant TL

  • IntroductionConstant TL

  • IntroductionTeTLSimple controlLosses in external resistor

  • IntroductionTeTLNot possible for PM motorMaximum torque capability reduces

  • IntroductionFor wide range of speed control 0 to base armature voltage, above base field flux reduction Armature voltage control : retain maximum torque capabilityField flux control (i.e. flux reduced) : reduce maximum torque capability

  • Introduction

  • IntroductionTe0 to base armature voltage, above base field flux reduction P = EaIa,max = kaIa,maxPmax = EaIa,max = kabaseIa,max 1/ P

  • MODELING OF CONVERTERS AND DC MOTORUsed to obtain variable armature voltagePOWER ELECTRONICS CONVERTERS Efficient Ideal : lossless Phase-controlled rectifiers (AC DC)

    DC-DC switch-mode converters(DC DC)

  • Modeling of Converters and DC motorPhase-controlled rectifier (ACDC)

  • Modeling of Converters and DC motorPhase-controlled rectifier

  • Modeling of Converters and DC motorPhase-controlled rectifier

  • Modeling of Converters and DC motorPhase-controlled rectifier (continuous current)

  • Phase-controlled rectifier (continuous current) Firing angle control Modeling of Converters and DC motor

  • Modeling of Converters and DC motorPhase-controlled rectifier (continuous current)

  • Modeling of Converters and DC motorPhase-controlled rectifier (continuous current)TdTd Delay in average output voltage generation 0 10 ms for 50 Hz single phase systemOutputvoltageCosine-wave crossingControl signal

  • Modeling of Converters and DC motorPhase-controlled rectifier (continuous current)Model simplified to linear gain if bandwidth (e.g. current loop) much lower than sampling frequency Low bandwidth limited applicationsLow frequency voltage ripple high current ripple undesirable

  • Modeling of Converters and DC motorSwitchmode converters

  • Modeling of Converters and DC motorSwitchmode converters

  • Modeling of Converters and DC motorSwitchmode converters

  • Modeling of Converters and DC motorSwitchmode convertersSwitching at high frequencyReduces current rippleIncreases control bandwidthSuitable for high performance applications

  • Modeling of Converters and DC motorSwitchmode converters - modeling

  • Modeling of Converters and DC motorSwitchmode converters averaged model

  • Modeling of Converters and DC motorSwitchmode converters averaged model

  • Modeling of Converters and DC motorSwitchmode converters small signal model2-quadrant converter4-quadrant converter

  • Modeling of Converters and DC motorDC motor separately excited or permanent magnetExtract the dc and ac components by introducing small perturbations in Vt, ia, ea, Te, TL and m

  • Modeling of Converters and DC motorDC motor small signal modelPerform Laplace Transformation on ac components

  • Modeling of Converters and DC motorDC motor small signal model

  • CLOSED-LOOP SPEED CONTROL

    Cascade control structure

  • CLOSED-LOOP SPEED CONTROLDesign procedure in cascade control structure Inner loop (current or torque loop) the fastest largest bandwidth The outer most loop (position loop) the slowest smallest bandwidthDesign starts from torque loop proceed towards outer loops

  • CLOSED-LOOP SPEED CONTROLClosed-loop speed control an example

  • CLOSED-LOOP SPEED CONTROLClosed-loop speed control an example PI controllersSwitching signals from comparison of vc and triangular waveform

  • CLOSED-LOOP SPEED CONTROLTorque controller design

  • CLOSED-LOOP SPEED CONTROLTorque controller design Open-loop gain compensatedcompensated

  • CLOSED-LOOP SPEED CONTROLSpeed controller design Assume torque loop unity gain for speed bandwidth
  • CLOSED-LOOP SPEED CONTROLSpeed controllerOpen-loop gain compensatedcompensated

  • CLOSED-LOOP SPEED CONTROLLarge Signal Simulation resultsSpeedTorque

  • CLOSED-LOOP SPEED CONTROL DESIGN EXAMPLESUMMARYPower electronics converters to obtain variable armature voltage Phase controlled rectifier small bandwidth large rippleSwitch-mode DC-DC converter large bandwidth small rippleController design based on linear small signal model Power converters - averaged model DC motor separately excited or permanent magnetClosed-loop speed control design based on Bode plots Verify with large signal simulation Speed control by: armature voltage (0 b) and field flux (b)