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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 Drive VFD ASD VVVF VFI What is an Inverter Drive • Speed Control Device Controls STATOR frequency Rotor changes speed with load • Speed Changes dependant on motor slip • NOT a current controller Only a current limiter Why the Vector was Invented • Increase Application Efficiency Better Speed Control Better Torque and/or Force Control More Efficient Use of Power Why the Vector was Invented • Performance Benefits Rotor Speed Regulation Lower Rotor Inertia Requirements Much Wider Speed Ranges Torque (or Force) Control Zero 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 Resistance Stator Inductance Rotor Resistance Rotor Inductance Air gap Losses Machine Losses and Inertia How Vector Control is Achieved • This is achieved in several fashions Manual – Programming Each Item Auto 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 feedback Speed Current Back EMF • Comparing to Established Model • Adjust accordingly Amount of Deviation Motor/System Model How Vector Control is Achieved Speed Changes What Types of Vectors Exist • Open Loop (Encoderless) Vector Establishes 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 Vector Monitors 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 Vector A method of firing transistor to control a specific element • Current Feedback • Voltage Feedback • Hysteresis • Sine Triggered (Coded) Vector A method of firing transistors to control the sine wave Applications for Vector Drives • Extruders Closed Loop for Clamped Dies Open Loop for Continuous Feed • Lifts Closed Loop for Safety Has 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 Scalar Potential Energy Savings with Encoderless • Spindle Drives – Typically Closed Loop Rapid Response Times Accurate Speed for Tapping Controlled Grind Speed Applications for Vector Drives • Winders Typically 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 Cranes Horizontal (X) – Scaler or Closed Loop Elevation (Y) – Closed Loop for Safety Bins or Forks (Z) – Scaler or Closed Loop • Crushers Oversized Scaler Applications for Vector Drives • Types of Braking D.C. Injection Shunt Braking – Most Common Bus Sharing Line Regenerative Line Regenerative Applications • • • • • • • • Elevators Hoists Presses Centrifuges Unwind Stands Windmills Pumping Jack Drives Application where Heated Resistors are a problem • Test Stands (dynamometers)