Energy-saving Principles and Technologies for Induction Motors

Wenzhong Ma, China University of Petroleum, China Lianping Bai, Beijing Information Science and Technology University, China

• About the Authors xiiiPreface xvAbout the Book xvii1 Introduction 11.1 The Energy‐saving Status of an Electric Motor System 11.1.1 Basic Situation of an Electric Motor System in China 11.1.2 The Main Contents of Energy Saving for Electric Motors in China 21.1.3 Status of Energy Saving for Electric Motors in China and Abroad 21.2 Main Development Ways of Energy Saving for Electric Motor System 41.2.1 Efficiency Improvement of Y Series Asynchronous Motor 41.2.2 Promoting Frequency Speed Regulation Technology 51.2.3 Promoting High‐Efficiency Motors and Permanent Magnet Motors 51.2.3.1 High‐Efficiency Electric Motor: An Important Way of Energy Saving 51.2.3.2 Permanent Magnetic Electric Motor: A New Kind of High‐Efficiency Motor 61.3 Energy Saving: The Basic National Policy of China 61.4 Main Contents of This Book 82 Overview of Three‐Phase Asynchronous Motors 112.1 Basic Structure and Characteristics of Three‐Phase Asynchronous Motors 112.1.1 Basic Characteristics of Three‐Phase Asynchronous Motors 112.1.2 Basic Types of Three‐Phase Asynchronous Motors 122.1.3 Basic Structure of Three‐Phase Asynchronous Motors 122.1.3.1 Stator 132.1.3.2 Rotor 142.1.3.3 Air Gap 152.1.4 Basic Parameters of Three‐Phase Asynchronous Motors 162.2 The Principle of a Three‐Phase Asynchronous Motor 172.3 Working Characteristic of Three‐Phase Asynchronous Motors 212.3.1 Equivalent Circuit of Asynchronous Motors 222.3.1.1 T Type Equivalent Circuit of Asynchronous Motor 222.3.1.2 Simplified Equivalent Circuit of Asynchronous Motors 232.3.2 Power Balance of Asynchronous Motors 232.3.3 Working Characteristics of Three‐Phase Asynchronous Motors 252.3.3.1 Speed Characteristic 262.3.3.2 Stator Current Characteristic 262.3.3.3 Electromagnetic Torque Characteristic T = f (P2) 262.3.3.4 Stator Power Factor Characteristic 272.3.3.5 Efficiency Characteristic η = f(P2) 272.4 Mechanical Characteristics of Three‐Phase Asynchronous Motors 272.4.1 Three Types of Formulas of Mechanical Characteristics 272.4.1.1 Physical Formula of Mechanical Characteristics 272.4.1.2 Parameter Formula of Mechanical Characteristic 282.4.1.3 Practical Expression of Mechanical Characteristic 302.4.2 Inherent Mechanical Characteristic of Asynchronous Motors 312.4.3 Man‐Made Mechanical Characteristic of Asynchronous Motors 322.4.3.1 Man‐Made Characteristic of Reducing Stator Voltage 322.4.3.2 Man‐Made Characteristic of Connecting Symmetrical Three‐Phase Resistances in the Rotor’s Loop 332.4.3.3 Man‐Made Characteristic of Changing the Frequency of Stator Voltage 342.5 Start‐up of Three‐Phase Asynchronous Motors 352.5.1 Starting Requirements of Three‐Phase Asynchronous Motors 352.5.1.1 In Order to Minimize the Impact on the Grid, the Starting Current Should be Small 352.5.1.2 The Starting Torque Must Be Large Enough to Speed Up the Starting Process and Shorten the Starting Time 362.5.2 Conditions for Squirrel Cage Asynchronous Motors Starting Directly 362.6 Energy Efficiency Standards of Three‐Phase Asynchronous Motors 372.6.1 Energy Efficiency Standards of IEC Three‐Phase Asynchronous Motors 382.6.1.1 Standard Applicable Scope 382.6.1.2 Class Standards 382.6.1.3 Interpolation Calculation 392.6.2 Energy Efficiency Standards of Three‐Phase Asynchronous Motors in the United States and EU 402.6.3 Energy Efficiency Standards of Three‐Phase Asynchronous Motors in China 402.7 Mainstream Products of Three‐Phase Asynchronous Motors 452.7.1 Brief Introduction of Existing Products of Three‐Phase Asynchronous Motors 452.7.2 Characteristics of Main Series of Three Phase Asynchronous Motors 462.7.3 Main Technical Data of Y2 Series Three‐Phase Asynchronous Motors 462.8 Main Subseries Three‐Phase Asynchronous Motors in China 472.9 Discussion Topics in the Chapter 553 Economic Operation of the Three‐Phase Induction Motor 573.1 Loss Analysis of the Three‐Phase Induction Motor 573.1.1 The Analysis of Iron Loss 573.1.1.1 Iron Loss 573.1.1.2 The Methods to Reduce Iron Loss 583.1.2 The Analysis of Mechanical Loss 583.1.2.1 Mechanical Loss 583.1.2.2 The Methods to Reduce Mechanical Loss 593.1.3 Stator and Rotor Copper Loss Analysis 593.1.3.1 Stator and Rotor Copper Loss 593.1.3.2 The Measures to Reduce Stator and Rotor Copper Loss 593.1.4 The Analysis of Stray Loss 593.1.4.1 Stray Loss 593.1.4.2 The Measures to Reduce Stray Loss 603.1.5 The Power Grid Quality’s Impact on the Loss 603.1.5.1 The Influence of Voltage Fluctuation on Various Losses 603.1.5.2 The Unbalance of the Three‐Phase Voltage’s Effect on Loss 613.1.5.3 The Impact of Higher Harmonic Current on the Induction Motor Loss 623.2 Efficiency and Power Factor of the Three‐Phase Asynchronous Motor 623.2.1 The Definition of Induction Motor’s Efficiency and Power Factor 623.2.1.1 The Definition of the Induction Motor’s Efficiency 623.2.1.2 The Definition of the Induction Motor’s Power Factor 633.2.2 The Calculation of Efficiency and Power Factor of Induction Motors 633.2.2.1 The Calculation of Operation Efficiency of the Induction Motor 633.2.2.2 The Calculation of Operational Power Factor of the Induction Motor 643.2.3 The Efficiency and Power Factor Curve of the Induct Motor 653.2.3.1 The Power Factor Curve of the Motor and Its Drawing 653.2.3.2 The Analysis of Efficiency Curve and Power Factor Curve 663.3 Economic Operation of the Three‐Phase Induction Motor 673.3.1 The Terms and Definitions of Economic Operation for the Three‐Phase Induction Motor 683.3.2 Basic Requirements for Economical Operation of the Three‐Phase Induction Motor 693.3.3 Calculation of Three‐Phase Induction Motor Comprehensive Efficiency 693.3.3.1 The Comprehensive Power Loss of the Motor 693.3.3.2 The Comprehensive Efficiency of the Induction Motor 703.3.3.3 The Weighted Average Comprehensive Efficiency of the Induction Motor Operation 703.3.3.4 The Rated Comprehensive Efficiency of Motor 703.3.3.5 Economic Load Rate of Active Power 713.3.3.6 Comprehensive Economic Load Rate 713.3.4 Judgment of Economic Operation 713.3.5 The Examples of Economic Operational Analysis 723.4 Calculation Methods for Energy Saving of the Three‐Phase Induction Motor 753.4.1 Using Power to Calculate Energy‐saving Amount 753.4.1.1 Active Power Saving 763.4.1.2 Reactive Power Saving 763.4.1.3 Comprehensive Power Saving 763.4.1.4 Calculation of Comprehensive Energy‐saving Quantity 763.4.1.5 Calculation of Comprehensive Power‐Saving Rate 763.4.2 Comprehensive Efficiency is Used to Calculate Power‐Saving Rate 783.4.3 Using Accumulated Power to Calculate Power‐Saving Rate 783.5 Comparison and Evaluation Method of Motor Energy‐saving Effect 793.5.1 Unqualified Old Motor as Reference 793.5.2 Qualified Old Motor as Reference 793.5.3 In Accordance with the National Standard of Motor as Reference 793.6 Discussion Topics of the Chapter 804 The Energy‐saving Principle and Method of the Motor Power and Load Match 814.1 Discussion on the “Lighter Load” 814.1.1 Boundary of the “Lighter Load” 814.1.2 Analysis of the Lighter Load Loss 834.2 Energy‐saving Principle of Power Matching 844.2.1 The Power Matching Principle of Energy Conservation 844.2.2 Motor Selection Steps 874.2.3 The Selection of the Motor Rated Power 884.2.3.1 Requirements of Power Selection 884.2.3.2 Steps of Power Selection 884.3 Double Power Induction Motors and Energy‐saving Principle 924.3.1 Double‐Power Induction Motors 924.3.2 Energy‐saving Principle of the Double‐Power Motors 934.3.3 Analysis of the Energy‐saving Effect of Winding in Series 944.3.3.1 The Calculation of the Energy‐saving Rate of the Average Active 964.3.3.2 The Calculation of the Rate of Energy Saving of the Average Reactive 974.3.3.3 The Calculation of the Average Comprehensive Rate of Energy Saving 984.3.4 The Control Method of the Dual‐Power Series Winding Motor 984.4 The Energy‐saving Method of the Y‐Δ Conversion 994.4.1 The Power Relations of Y‐Δ 994.4.2 The Energy‐saving Effect of Y‐Δ Conversion 1004.4.2.1 Loss Analysis 1004.4.2.2 Testing and Analyzing Energy‐saving Effect 1014.4.3 The Y‐Δ Conversion Control Circuit 1024.5 The Energy‐saving Method of Extended Δ Winding Switching 1044.5.1 The Design Principle of the Extended Δ Winding 1044.5.2 The Switching Control Circuit for the Extended Δ 1054.5.3 The Comparison of Dual‐Power Motor 1064.5.3.1 Power Range 1064.5.3.2 Winding Design and Manufacturing Cost 1064.5.3.3 The Cost of Control System 1064.6 Discussion Topics in the Chapter 1065 Energy‐saving Principle and Methods of Speed Matching 1095.1 Energy‐saving Principle of Speed Matching 1095.1.1 Basic Parameters of the Pump 1095.1.2 Energy Analysis of Water Supply System 1115.1.2.1 Energy Consumption of Motor in Constant Speed Operation 1135.1.2.2 Energy Consumption of Motor in the Variable Frequency Speed Control Operation 1135.1.2.3 Power‐Saving Rate of Using Variable Frequency Speed Control 1145.1.3 Efficiency Analysis of Speed Control Water Supply System 1155.1.4 Comparison of Various Motor Speed Control Methods 1165.1.4.1 Variable Frequency Speed Control 1165.1.4.2 Pole Changing Speed Control 1175.1.4.3 Cascade Speed Control 1175.1.4.4 Variable Voltage Speed Control 1185.2 Energy‐saving Theoretical Analysis of Pump Speed Control 1185.2.1 Characteristic Curve of Pipe Network 1185.2.2 Pump Characteristic Curve 1195.2.2.1 Head–Flow Curve of Pump 1205.2.2.2 Power–Flow Curve of Pump 1205.2.2.3 Efficiency–Flow Curve of Pump 1215.2.2.4 Working Point of Pump 1215.2.3 Theoretical Analysis of Pump Speed Control Energy Saving 1215.2.4 Energy‐saving Calculation of Variable Frequency Speed Controlling Water Supply System 1235.3 Control Principle of Constant Pressure Water Supply System 1245.3.1 Control Principle of Constant Pressure Water Supply 1245.3.2 Constant Pressure Water Supply Control System 1255.4 Application of Variable Frequency Speed Control Energy‐saving Technology 1275.4.1 Basic Principle of Motor Variable Frequency Speed Control 1275.4.2 Selection of Frequency Converter 1295.4.2.1 Type Selection of Converter 1295.4.2.2 Power Supply Selection of Converter 1305.4.2.3 Frequency Characteristic Selection of Converter 1305.4.2.4 Function Selection of Converter 1305.4.2.5 Capacity Selection of Converter 1305.4.2.6 Selection of Other Accessories 1315.4.3 Instances of Converter Selection 1315.4.4 Points Requiring Attention in the Operation of Converter 1335.4.4.1 Harmonic Problems 1335.4.4.2 Torque Ripple Problems 1345.4.4.3 Interference Problems 1345.4.5 Application of VVVF Energy‐saving Technology 1345.4.5.1 Application of Fan VVVF 1355.4.5.2 Applications of Air Compressor VVVF 1365.5 Principles of Motor’s Pole Changing Speed Control 1375.5.1 Pole Changing Working Principle of Motor 1375.5.2 Common Pole Changing Methods of Motor 1395.5.2.1 Pole Changing Principle of Reverse Method 1405.5.2.2 Commutation Method 1415.5.2.3 Varying Pitch Method 1415.5.3 Common Connection Methods of Wiring Ends 1425.6 Energy‐saving Principles and Applications of Combined Pole Changing Speed Control 1435.6.1 Examples of Multipump System 1435.6.2 Energy‐saving Principles of Combined Pole Changing Speed Control 1455.6.3 Energy‐saving Examples of Combined Pole Changing Speed Control 1475.6.4 Comparison of Combined Pole Changing Speed Control and Variable Frequency Speed Control 1485.7 Discussion Topics in the Chapter 1496 Energy‐saving Principle and Method of the Mechanical Properties Fit 1516.1 Load Characteristics of a Beam‐Pumping Unit 1516.1.1 Working Principle of the Beam‐Pumping Unit 1526.1.2 Requirements of Beam Pumping Unit to Drive a Motor 1546.2 Energy‐saving Principle of Mechanical Properties Fit 1546.2.1 Characteristics of an Ultra‐High Slip Motor 1546.2.1.1 Analysis of Power Factor 1556.2.1.2 Efficiency Analysis 1566.2.1.3 Loss Analysis 1566.2.1.4 Analysis of Starting Performance 1566.2.2 Energy‐saving Principle of the Adaptation of Mechanical Properties 1576.2.2.1 With High Starting Torque, Lowering Power Level, Improving the Load Factor 1576.2.2.2 Soft Features of Ultra‐High Slip Motor Can Improve Coordination and Efficiency of the System 1576.2.3 Applications and Standards of Ultra‐High Slip Motor 1586.2.4 Applications of a Winding Motor 1596.3 Energy‐saving Instances of Mechanical Properties Fit 1596.3.1 Power Factor and Comprehensive Efficiency of Motor Before Transformation 1606.3.2 The Power Factor and Comprehensive Efficiency of Switching 22 kW Ultra‐High Slip Motor 1606.3.3 Energy‐saving Effect of Motor 1616.3.4 Overall Energy‐saving Effect of the Pumping Unit System 1616.4 Discussion Topics in the Chapter 1627 The Energy‐saving Principle of Induction Motor Reactive Power Compensation 1637.1 Energy‐saving Principle of Induction Motor Reactive Power Compensation 1637.1.1 Reactive Power of Induction Motor 1637.1.2 Energy‐saving Principle of Induction Motor Reactive Power Compensation 1647.1.3 Role of Induction Motor Reactive Power Compensation 1677.1.4 Methods for Induction Motor Reactive Power Compensation 1677.2 Capacity Selection for the Compensating Capacitor 1687.2.1 The Calculation of Induction Motor’s Reactive Power 1687.2.2 The Reactive Power Curve of Induction Motor 1697.2.3 The Capacity Selection of the Induction Motor Compensation Capacitor 1707.2.4 Low‐Voltage Shunt Capacitor 1727.2.4.1 Self‐Healing Low‐Voltage Shunt Capacitor 1727.2.4.2 Main Technical Indicators 1737.2.4.3 Environmental Conditions for the Operation 1747.2.4.4 Main Parameters of the National Standards 1747.2.5 Research of Reactive Power Compensation for Induction Motor 1747.2.6 Experiential Formula for Compensation Capacitor of Induction Motor 1767.3 Static Reactive Power Compensation of Induction Motor 1777.3.1 Mode of Static Compensation 1777.3.2 Caution for Static Compensation 1807.3.2.1 Prevent the Emerge of Self‐Excitation 1807.3.2.2 Overvoltage Protection 1807.3.2.3 Prevent Overtime of Maintenance Voltage 1817.3.2.4 Avoid the Resonance 1817.3.2.5 Prevent System Harmonic Influence 1817.3.2.6 Suppression of Capacitor Dash Current 1827.3.3 Verification of the Static Compensation Capacitor 1827.3.4 The Main Device Selection of the Compensation Device 1847.3.4.1 Selection of Discharge Resistance 1847.3.4.2 Selection of the Current Limiting Reactor 1847.3.4.3 Contactor Selection 1857.3.4.4 Fuse Selection 1857.4 Reactive Power Dynamic Compensation of the Induction Motor 1857.4.1 Dynamic Compensation Based on TCR Phase Control 1867.4.1.1 The Circuit Theory of Transistor Phased‐Control Dynamic Compensation 1867.4.1.2 The Principle of the Thyristor Phase‐Controlled Reactive Power Regulation 1887.4.2 Dynamic Compensation‐Based IGBT Control 1897.4.2.1 Circuit Schematic Based on IGBT Dynamic Compensation 1897.4.2.2 Theory of Reactive Power Regulation Based on IGBT 1907.5 Hybrid Compensation 1927.5.1 Fluctuation Part of the Dynamic Compensation 1927.5.2 Over Make Up Part of the Dynamic Compensation 1957.6 The Discussion Topic of the Chapter 196Further Reading 199Index 201