ASD cover 2 12 01 10 40 AM Page 2 15 95 CDN Adjustable Speed Drive REFERENCE GUIDE 4th Edition ASD cover 2 12 01 10 40 AM Page 3 First Edition November 1987 Second Edition March 1991 Third Edition February 1995 Fourth Edition August 1997 Revised by Richard Okrasa P Eng Ontario Hydro Neither Ontario Hydro nor any person acting on its behalf assumes any liabilities with respect to the use of or for damages resulting from the use of any information equipment product method or process disclosed in this guide In House Energy Efficiency Energy Savings are Good Business Printed in Canada Copyright 1997 Ontario Hydro ASD body 0 82 2 12 01 9 52 AM Page c ADJUSTABLE SPEED DRIVE Reference Guide 4th Edition ASD body 0 82 2 12 01 9 52 AM TA B L E Page i OF CONTENTS INTRODUCTION 1 Latest Improvements 2 CHAPTER 1 CLASSIFICATIONS 3 Classification of Motors 3 Classification of Drives 3 CHAPTER 2 PHYSICAL APPEARANCE 5 CHAPTER 3 PRINCIPLES OF OPERATION 7 Conventional Fixed speed AC Systems 7 DC Drives 8 AC Drives 8 Eddy Current Clutches 8 Switched Reluctance Drives 9 Vector Drive 10 Wound rotor Motor Controllers 10 Variable Voltage Controllers 11 Variable Frequency Drives 11 Components 12 Types of Inverters 13 Waveforms 14 Switching Devices Power Electronics 14 Medium Voltage Drives 14 Recommended Specifications 15 CHAPTER 4 COMPARISON OF ASDS 17 AC Drives 17 i ASD body 0 82 2 12 01 9 52 AM TA B L E OF Page ii CONTENTS Variable Voltage Inverter VVI 17 Current Source Inverter CSI 18 Pulse Width Modulator PWM 20 Power Factor Comparison 22 DC Drives 23 Eddy Current Coupling 25 Cycloconverter 26 CHAPTER 5 STANDARD AND OPTIONAL FEATURES 33 CHAPTER 6 ADVANTAGES 35 Speed Control 35 Position Control 36 Torque Control 36 High Energy Savings Potential 36 Soft Start Regenerative Braking 36 Equipment Life Improvement 37 Multiple Motor Capability 37 Bypass Capability 37 Safe Operation in Harsh Environments 37 Temporary or Back up Operation 37 Reduction in Vibration and Noise Level 38 Re acceleration Capability 38 Tips and Cautions 38 CHAPTER 7 APPLICATION CONSIDERATIONS 39 How to Select an ASD 39 Software 42 ii ASD body 0 82 2 12 01 9 52 AM TA B L E Page iii OF CONTENTS Financial Evaluation 42 Load Characteristics 42 Application Types by Load 43 Tips and Cautions 46 Motor Drive System 49 Thermal Considerations 54 Other Considerations 56 Efficiency 57 Reliability of ASDs 58 Applications 59 Performance Required 60 Starting and Stopping Characteristics 62 Torque 62 Environment 63 Weight and Space 63 Accessories 64 Safety 65 Service and Maintenance 65 Tips and Cautions 67 CHAPTER 8 ECONOMICS 69 Economic Factors 72 Capital Costs 72 Capital Savings 73 Operating Costs and Savings 73 Tips and Cautions 75 iii ASD body 0 82 2 12 01 9 52 AM TA B L E OF Page iv CONTENTS CHAPTER 9 HARMONIC DISTORTION 77 Harmonics 77 What Harmonic Distortion Can Do 78 Production and Transmission 79 Isolation Transformers 80 Other Guidelines IEEE 519 1992 81 APPENDIX A FORMULAS FOR CALCULATING APPLICATIONS 83 APPENDIX B CONVERSION FACTORS 93 ABBREVIATIONS 95 BIBLIOGRAPHY 97 INDEX 99 ASD SUPPLIERS IN ONTARIO 101 iv ASD body 0 82 2 12 01 9 52 AM LIST Page v FIGURES OF 1 Comparison of Range Process Speed Control 1 2 Physical Appearance of Variable Frequency Drive Motor System 5 3 8 6 Pole Switched Reluctance Motor 9 4 Vector Drive 10 5 Closed Loop Feedback Adjustable Frequency Inverter System 12 6 VVI Variable Voltage Inverter 17 7 VVI Waveforms 18 8 CSI Current Source Inverter 19 9 CSI Waveforms 19 10 Block Diagram for a Typical CSI Drive 19 11 PWM Pulse Width Modulated Inverter 21 12 PWM Waveforms 21 13 Block Diagram for a Typical PWM Drive 21 14 Power Factor Comparison 22 15 DC Drive 23 16 ECC Eddy Current Coupling 26 17 Cycloconverter Circuit 27 18 Duty Cycles 43 19 Variable Torque Load 45 20 Constant Torque Load 45 21 Constant Horsepower Load 45 22 Power Required is Proportional to RPM3 Centrifugal Fan Blower Pump 46 23 Power Savings in Fans and Pumps Using ASDs 48 v ASD body 0 82 2 12 01 9 52 AM LIST OF Page vi FIGURES 24 Motor Derating Curves vs Speed Range When Applied to Adjustable Frequency AC Drives 6 Step Waveform or PWM 53 25 Watts Loss Efficiency Comparison 57 26 Typical AC Drive Efficiency 57 27 Motor Performance Typical 60 Hz 63 28 Ideal Torque Speed Curves 64 29 NEMA Design B Motor Torque Speed Curve 64 30 Capital Cost Comparison of Motor Drive Systems Medium HP Voltages 76 31 Harmonic Distortion 78 A 1 Calculating Hollow Shafts 88 A 2 Calculating the Inertia of Complex Concentric Rotating Parts 89 vi ASD body 0 82 2 12 01 9 52 AM LIST 1 2 3 4 5 Page vii OF TA B L E S Comparison of Adjustable Speed Drives 29 ASD and Electronic Motor Features 34 Suitability of Inverters for NEMA Motor Designs 55 ASD Checklist of Costs Savings 70 ASD Investment Decision Technique 71 vii ASD body 0 82 2 12 01 9 52 AM Page 1 INTRODUCTION An adjustable speed drive ASD is a device used to provide continuous range process speed control as compared to discrete speed control as in gearboxes or multi speed motors An ASD is capable of adjusting both speed and torque from an induction or synchronous motor An electric ASD is an electrical system used to control motor speed ASDs may be referred to by a variety of names such as variable speed drives adjustable frequency drives or variable frequency inverters The latter two terms will only be used to refer to certain AC systems as is often the practice although some DC drives are also based on the principle of adjustable frequency Continuous Speed Discrete Operation FIGURE 1 Comparison of Range Process Speed Control Introduction 1 ASD body 0 82 2 12 01 9 52 AM Page 2 In this guide drive refers to the electric ASD Application concerns in connecting electric or mechanical ASDs have similar effects on the driven load and these are covered in this guide L ATEST I MPROVEMENTS Microprocessor based controllers eliminate analogue potentiometer based adjustments Digital control capability Built in Power Factor correction Radio Frequency Interference RFI filters Short Circuit Protection automatic shutdown Advanced circuitry to detect motor rotor position by sampling power at terminals ASD and motor circuitry combined to keep power waveforms sinusoidal minimizing power losses Motor Control Centers MCC coupled with the ASD using real time monitors to trace motor drive system performance Higher starting torques at low speeds up to 150 running torque up to 500 MP in voltage source drives Load commutated Inverters coupled
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