VECTOR DRIVES

EASA June 2005“REACHING NEW HEIGHTS”Dave Ruehle and Bill Colton

Outline

• Define a Drive• What is an Inverter Drive• Why the Vector was Invented• How Does a Vector Work• What Types of Vectors Exist• Typical Applications for Vector Drives

What is a Drive

• Parts and Pieces Prime Mover Mechanical Reduction(s)

Control Circuits Ancillary devices

Couplings Feedback

What is an Inverter Drive

• Terminology

Scalar DriveVFDASDVVVFVFI

What is an Inverter Drive

• Speed Control DeviceControls STATOR frequencyRotor changes speed with load

• Speed Changes dependant on motor slip

• NOT a current controllerOnly a current limiter

Why the Vector was Invented

• Increase Application Efficiency

Better Speed ControlBetter Torque and/or Force ControlMore Efficient Use of Power

Why the Vector was Invented

• Performance Benefits

Rotor Speed RegulationLower Rotor Inertia RequirementsMuch Wider Speed RangesTorque (or Force) ControlZero Speed Full Torque

How Inverter Control Is Achieved

• Convert AC Input to DC• Filter the DC Power• Create a digital output pulse train varying the

frequency and voltage to Stator

How Vector Control is Achieved

• Establish the motor/system Model

Stator ResistanceStator InductanceRotor ResistanceRotor InductanceAir gap LossesMachine Losses and Inertia

How Vector Control is Achieved

• This is achieved in several fashions

Manual – Programming Each ItemAuto Tuning

• Program Basics• Run Tests for Additional Items

Adaptive Tuning• Continuously Adjusting for Changing

Conditions

• Now The System Model is Established

How Vector Control is Achieved• Hardware

Comparison

Components Inverter Vector

Converter X X

Filter X X

Output X X

Feedback X

How Vector Control is Achieved

• Monitoring the feedbackSpeedCurrentBack EMF

• Comparing to Established Model

• Adjust accordinglyAmount of DeviationMotor/System Model

How Vector Control is Achieved Speed Changes

What Types of Vectors Exist

• Open Loop (Encoderless) VectorEstablishes the Shaft Position from the current (amp) measurement

Advantages• Lower Initial Cost• Reduced Wiring

Disadvantages• Not as responsive• Limited Speed Range• Difficulty with Impact Loads• Temperature Changes can be Problematic

What Types of Vectors Exist

• Closed Loop VectorMonitors Shaft Position via Feedback

• Encoder• Resolver

Advantages• Excellent Speed Regulation• Full Torque at Zero Speed• Systems Capabilities• Very Responsive• Higher Safety• Easier to Tune

What Types of Vectors Exist

• Closed Loop Vectors (Cont.)

Disadvantages

• Additional Initial Cost• More Wiring• Motor Length• Requires Better Wiring Practice

What Types of Vectors Exist

• Space VectorA method of firing transistor to control a specific element• Current Feedback• Voltage Feedback• Hysteresis

• Sine Triggered (Coded) VectorA method of firing transistors to control the sine wave

Applications for Vector Drives

• ExtrudersClosed Loop for Clamped DiesOpen Loop for Continuous Feed

• LiftsClosed Loop for SafetyHas been done with Open Loop and Mechanical Load Brakes – consult manufacturers

Applications for Vector Drives

• Bridge Drives – Typically Scalar

• Trolley Drives – Typically Scalar

• Conveyors – Typically Scalar

• Centrifugal Loads – Typically ScalarPotential Energy Savings with Encoderless

• Spindle Drives – Typically Closed LoopRapid Response TimesAccurate Speed for TappingControlled Grind Speed

Applications for Vector Drives

• WindersTypically Closed Loop for Tension Control

• Mooring Winch – Encoderless• Mixers – Typically Scalar• Line Shaft Replacements – Closed

Loop with “electronic line shaft” capability

• Cut to Length – Closed Loop with Motion Control

Applications for Vector Drives

• Flying Shear – Closed Loop with Motion Controller

• Stacker CranesHorizontal (X) – Scaler or Closed LoopElevation (Y) – Closed Loop for SafetyBins or Forks (Z) – Scaler or Closed Loop

• CrushersOversized Scaler

Applications for Vector Drives

• Types of Braking

D.C. InjectionShunt Braking – Most CommonBus SharingLine Regenerative

Line Regenerative Applications• Elevators• Hoists• Presses• Centrifuges• Unwind Stands• Windmills• Pumping Jack Drives• Application where Heated Resistors are a

problem• Test Stands (dynamometers)