Elements of Electrical Machines

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Front Cover Half Title Page Title Page Copyright Preface Acknowledgements Contents 1. DC Machines 1.1 Introduction 1.2 Concept of Electro-Mechanical Energy Conversion 1.3 Types of DC Machines 1.4 Construction of DC Machine 1.5 General Features of DC Armature Windings 1.6 Commutator Pitch (Yc) 1.7 Pole Pitch 1.8 Coil Span or Coil Pitch (Ys) 1.9 Full Pitched Coil and Fractional Pitched Coil 1.10 Types of DC Armature Windings 1.11 Armature Winding Terminology 1.12 General Rules for DC Armature Windings 1.13 Relationship between Pitches for Simplex Lap Winding 1.14 Simplex Wave Winding 1.15 Design of Simplex Wave Winding 1.16 Dummy Coils 1.17 Applications of Lap- and Wave-Windings 1.18 Multiplex Windings 1.19 Working of DC Generator 1.20 EMF Equation of DC Generator 1.21 Important Relations for Various Types of DC Generators 1.22 Armature Reaction 1.23 Geometrical and Magnetic Neutral Axes 1.24 Explanation of Armature Reaction 1.25 Demagnetising and Cross-Magnetising Conductors 1.26 Calculation of Demagnetising Ampere-Turns Per Pole 1.27 Cross-Magnetising Ampere–Turns Per Pole 1.28 Compensating Windings 1.29 ATC /Pole for Compensating Winding 1.30 Commutation 1.31 Calculation of Reactance Voltage 1.32 Methods of Improving Commutation 1.33 Interpoles or Compoles 1.34 Equalising Connections 1.35 Important Facts About DC Generators 1.36 DC Generator Characteristics 1.37 Open Circuit Characteristic of ADC Generator 1.38 Characteristics of A Separately Excited DC Generator 1.39 Voltage Build-up in a Self-Excited Generator 1.40 Critical Field Resistance for a Shunt Generator 1.41 Critical Resistance for a Series Generator 1.42 Characteristics of Series Generator 1.43 Characteristic of a Shunt Generator 1.44 Critical External Resistance for Shunt Generator 1.45 How to Draw OCC at Different Speeds? 1.46 Critical Speed (Nc) 1.47 Conditions for Voltage Build-upof a Shunt Generator 1.48 Compound Generator Characteristic 1.49 Voltage Regulation 1.50 Need for Parallel Operation of DC Generators 1.51 Conditions for Parallel Operation of Shunt Generators 1.52 Connecting Shunt Generators in Parallel 1.53 Load Sharing by Shunt Generators in Parallel 1.54 Parallel Operation of Compound Generators 1.55 Parallel Operation of Series Generators 1.56 DC Generator Specification 1.57 Working Principle ofDC Motor 1.58 Back or Counter EMF 1.59 Significance of Counter EMF 1.60 Equivalent Circuit of a DC Motor 1.61 Power Developed in a DC Motor 1.62 Torque Developed in DC Motor 1.63 Characteristics of DC Motors 1.64 Speed Equations 1.65 Speed Regulation 1.66 Speed Control of DC Motor 1.67 Starting of DC Motor 1.68 Losses in DC Machines 1.69 Power Flow in DC Machines 1.70 Efficiency of DC Machines 1.71 Testing of DC Machines Solved University Problems forPractice 2. Single Phase Transformer 2.1 Introduction 2.2 Transformer 2.3 Classification of Transformer 2.4 Principle of Operation ofTransformer 2.5 EMF Equation of Transformer 2.6 Transformation Ratio (K) 2.7 Impedance Transformation 2.8 Ideal Transformer 2.9 Practical Transformer 2.10 Practical Transformer on No-Load 2.11 Transformer on Load 2.12 Equivalent Circuit Diagram 2.13 Losses in Transformer 2.14 Transformer Efficiency 2.15 Voltage Regulation of a Transformer 2.16 Calculation of Efficiency from Transformer Tests 2.17 Why Transformer Rating in KVA? 2.18 Sumpner or Back-to-Back Test 2.19 Introduction to Auto Transformer 2.20 Conversion of Two-Winding Transformer into Auto Transformer 2.21 Parallel Operation of Single Phase Transformers 2.22 Single Phase Equal Voltage Ratio Transformers in Parallel 2.23 Single Phase Unequal Voltage Ratio Transformers in Parallel Solved University Problems for Practice 3. Three Phase Transformer 3.1 Introduction 3.2 Construction of Three Phase Transformer 3.3 Types of Three Phase Transformer 3.4 Three Phase Transformer Connections and Phasor Groups 3.5 Three Phase Transformation with Two Transformers 3.6 Harmonics in Transformers 3.7 Tertiary Windings 3.8 Transformer Noise 3.9 Initial Rush of Current 3.10 Parallel Operation of 3-Phase Transformers 4. Three Phase InductionMotors 4.1 Three Phase Induction Motor 4.2 Construction of Induction Machines 4.3 Principle of Operation 4.4 Rotating Magnetic Field due to 3-Phase Currents 4.5 Alternate Analysis for Rotating Magnetic Field 4.6 Synchronous Speed 4.7 Slip(s) 4.8 Effect of Slip on Motor Parameters 4.9 Losses in Induction Motor 4.10 Power Flow Diagram for an Induction Motor 4.11 Efficiency of an Inductor Motor 4.12 Rotor Torque 4.13 Starting Torque (Ts) 4.14 Condition for Maximum Starting Torque 4.15 Effect of Change of Supply Voltage 4.16 Starting Torque of 3-Phase Induction Motors 4.17 Motor under Load 4.18 Torque under Running Conditions 4.19 Maximum Torque under Running Conditions 4.20 Equivalent Circuit of Induction Motor 4.21 Torque–Slip Characteristics of 3φ Induction Motor 4.22 Speed Control of Induction Motor 4.23 Speed Control by Variation of Rotor Resistance 4.24 Speed Control by Slip Energy Recovery Method 4.25 Starting of Three Phase Induction Motors 4.26 A Comparision between Induction Motor and Transformer 4.27 Crawling of Induction Motors 4.28 Cogging 4.29 Linear Induction Motor (Lim) 4.30 Properties of Linear Induction Motor 5. Single Phase Induction Motors 5.1 Introduction 5.2 Single Phase Induction Motor—Principle 5.3 Double Revolving Field Theory of Single Phase Induction Motor 5.4 Cross Field Theory 5.5 Rotating Magnetic Field from 2-Phase Supply 5.6 Equivalent Circuit of Single Phase Induction Motor 5.7 Determination of Equivalent Circuit Parameters 5.8 Starting Methods and Types of Single Phase Induction Motor 5.9 Split-Phase Induction Motor 5.10 Capacitor Motors 5.11 Capacitor-Start Motor 5.12 Two-Value Capacitor Motor/Capacitor-Start Capacitor-Run Motor 5.13 Permanent-Split Capacitor (PSC) Motor/Single Value Capacitor Motor 5.14 Shaded Pole Motors 5.15 Comparison between 1φ and 3φ Induction Motors 5.16 AC Series Motor or Universal Motor 5.17 Single Phase Repulsion Motor 5.18 Repulsion-Start Induction-Run Motor 5.19 Repulsion–Induction Motor 5.20 Single-phase Synchronous Motors 5.21 Reluctance Motor 5.22 Hysteresis Motor 6. Alternator 6.1 Introduction 6.2 Basic Principle 6.3 Advantages of Rotating Field Alternator 6.4 Speed and Frequency 6.5 Construction of Alternators 6.6 Armature Windings 6.7 Pitch Factor/Coil Span Factor (KC) 6.8 Advantages of Pitching or Chording 6.9 Distribution Factor or Breadth factor (Kd) 6.10 Excitation Systems for Synchronous Machines 6.11 Armature Reaction in Synchronous Machine 6.12 Alternator on Load 6.13 Equivalent Circuit 6.14 Synchronous Reactance (XS) 6.15 Equivalent Circuit and Phasor Diagrams of a Synchronous Generator 6.16 Voltage Regulation 6.17 Determination of Voltage Regulation 6.18 Synchronous Impedance Method or EMF Method 6.19 MMF Method 6.20 Zero-Power Factor Characteristic(ZPFC) 6.21 Power Operating in Cylinderical Rotor 6.22 Power Angle/Power Angle Characteristic 6.23 Effect of Salient Poles 6.24 Two-Reactance Concept for Salient Pole Synchronous Machine 6.25 Parallel Operation of Alternators 6.26 Method of Synchronizing 6.27 Alternator on Infinite Busbar Solved University Problems for Practice 7. Synchronous Motors 7.1 Synchronous Motors 7.2 Construction of Three Phase Synchronous Motor 7.3 Rotating Magnetic Field (RMF) 7.4 Types of Synchronous Motors 7.5 Operating Principle of Synchronous Motors 7.6 Motor on Load 7.7 Pull-Out Torque 7.8 Phasor Diagram of Motor 7.9 Effect of Changing Field Excitation at Constant Load 7.10 Phasor Diagrams with Different Excitations 7.11 Curves for Synchronous Motor 7.12 Power Flow within a Synchronous Motor 7.13 Synchronous Condenser 7.14 Hunting in Synchronous Motor 7.15 Applications, Advantages and Disadvantages of Synchronous Motor 8. General Introduction of Special Machines 8.1 Introduction 8.2 Stepper Motor 8.3 Definitions Associated with Stepper Motor 8.4 Permanent Magnet (PM) Stepper Motor 8.5 Variable-Reluctance (VR) Stepper Motor 8.6 Hybrid Stepper Motor 8.7 Servo Mechanism 8.8 DC Servo Motors 8.9 AC Servomotor 8.10 Switched Reluctance Motor (SRM) 8.11 Permanent Magnet DC Motor 8.12 Brushless DC Motors Index Back Cover