A Course Material on EE6352- ELECTRICAL ENGINEERING AND INSTRUMENTATION By Dr. K.Pandiarajan PROFESSOR & HOD DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING & S.Vijay ASSISTANT PROFESSOR DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING SASURIE COLLEGE OF ENGINEERING, VIJAYAMANGALAM – 638 056. QUALITY CERTIFICATE This is to certify that the course material Subject Code : EE6352 Subject : Electrical Engineering and Instrumentation Class : II Year ECE Being prepared by us and it meets the knowledge requirement of the university curriculum. Signature of the Author (s) Name : Dr.K.Pandiarajan Designation : Professor & HOD Name : S.Vijay Designation : Assistant Professor This is to certify that the course material being prepared by Dr.K.Pandiarajan & S.Vijay is of adequate quality. They have referred more than five books among them minimum one is from abroad author. Signature of HD Name : Dr. K Pandiarajan SEAL UNIT I DC MACHINES 1-29 1.1 Three Phase Circuits, A Review 01 1.2 Construction of DC Machines 08 1.3 Theory of Operation Of DC Generators 09 1.3.1 EMF Equation of Generator 11 1.4 Characteristics of DC Generators 12 1.5 Operating Principle of DC Motors 18 1.5.1 Torque Equation 19 1.6 Types of DC Motors and their Characteristics 19 1.6.1 Types of DC Motors 19 1.6.2 D.C Motor Characteristics 22 1.7 Speed Control of DC Motors 24 1.8 Applications 28 1.9 Problems 28 UNIT II TRANSFORMER 29-43 2.1. Introduction 29 2.1.1 Transformer Classification 30 2.1.2 Primary and Secondary Windings 30 2.1.3 Functions of Transformer Parts 31 2.1.4 Principle of Operation 31 2.1.5 Ideal Transformer 31 2.2 Single Phase Transformer Construction and Principle of Operation 31 2.3. EMF Equation of Transformer 33 2.4. Transformer on No–Load 39 2.5 Transformer on Load 34 2.6 Equivalent Circuit of Transformer 35 2.6.1 Equivalent Circuit of Transformer Referred to Primary 35 2.6.2 Approximate Equivalent Circuit of Transformer 38 2.6.3 Equivalent Circuit of Transformer Referred to Secondary 38 2.7 Regulation of Transformer 39 2.8 Transformer Losses and Efficiency 39 2.9 All Day Efficiency 39 2.10 Auto Transformer 40 2.11 Problems 42 UNIT III INDUCTION MACHINES AND SYNCHRONOUS MACHINES 43-61 3.1 Types, Construction and Working of 3 Phase Induction Motor 43 3.2 Equivalent Circuit 45 3.3 Construction of Single-Phase Induction Motors 47 3.3.1 Stator of Single Phase Induction Motor 47 3.3.2 Rotor of Single Phase Induction Motor 48 3.3.3 Working Principle of Single Phase Induction Motor 49 3.4 Types of Single Phase Induction Motors 49 3.5 Double Revolving Field Theory 49 3.6 Starting Methods 49 3.6.1 Resistance Split-Phase Motor 50 3.6.2 Capacitor-Start Motor 51 3.6.3 Capacitor-start and Capacitor-run Motor 51 3.6.4 Shaded-pole Motor 52 3.7 Types, Construction and Working Principle of Alternator 53 3.7.1 Types of Alternator 53 3.7.2 Construction and working principle of Alternator 54 3.8 Equation of Induced EMF 55 3.9 Voltage Regulation 56 3.10 Working Principle and Methods of Starting Of Synchronous Motors 58 3.11 V-Curves 60 UNIT IV BASICS OF MEASUREMENT AND INSTRUMENTATION 61-81 4.1 Static and Dynamic Characteristics of Measurement 61 4.2 Errors in Measurement 65 4.3 Transducers 67 4.4. Resistance Transducers 71 4.5 Strain gauge 73 4.6 Thermistors 74 4.7 Capacitive Transducers 76 4.8 Piezo electric transducer 77 4.9 Variable Inductive Transducers 79 4.9.1 LVDT 79 4.9.2 RVDT 80 UNIT V ANALOG AND DIGITAL INSTRUMENTS 81-122 5.1 Digital Voltmeter (DVM) 81 5.2 Digital Multi Meter (DMM) 84 5.3 Storage oscilloscope 85 5.4 Comparison of analog and digital instruments 87 5.5 Wheat stone bridge 88 5.6 Kelvin’s double bridge 90 5.7 Maxwell bridge 90 5.8 Schering Bridge 92 5.9 Wien Bridge 93 5.10 Q-Meter 94 Glossary 96 Two Marks Question & Answers 98 Important Question Bank 112 University Question Bank 119 EE6352 ELECTRICAL ENGINEERING AND INSTRUMENTATION UNIT I DC MACHINES 9 Three phase circuits, a review. Construction of DC machines – Theory of operation of DC generators – Characteristics of DC generators- Operating principle of DC motors – Types of DC motors and their characteristics – Speed control of DC motors- Applications. UNIT II TRANSFORMER 9 Introduction – Single phase transformer construction and principle of operation – EMF equation of transformer-Transformer no–load phasor diagram - Transformer on–load phasor diagram - Equivalent circuit of transformer – Regulation of transformer –Transformer losses and efficiency- All day efficiency –auto transformers. UNIT III INDUCTION MACHINES AND SYNCHRONOUS MACHINES 9 Principle of operation of three-phase induction motors – Construction –Types – Equivalent circuit –Construction of single-phase induction motors – Types of single phase induction motors – Double revolving field theory – starting methods - Principles of alternator – Construction details – Types –Equation of induced EMF – Voltage regulation. Methods of starting of synchronous motors – Torque equation – V curves – Synchronous motors. UNIT IV BASICS OF MEASUREMENT AND INSTRUMENTATION 9 Static and Dynamic Characteristics of Measurement – Errors in Measurement - Classification of Transducers – Variable resistive – Strainguage, thermistor RTD – transducer - Variable Capacitive Transducer – Capacitor Microphone - Piezo Electric Transducer – Variable Inductive transducer – LVDT, RVDT UNIT V ANALOG AND DIGITAL INSTRUMENTS 9 DVM, DMM – Storage Oscilloscope. Comparison of Analog and Digital Modes of operation, Application of measurement system, Errors. Measurement of R, L and C, Wheatstone, Kelvin, Maxwell, Anderson, Schering and Wien bridges Measurement of Inductance, Capacitance, Effective resistance at high frequency, Q-Meter. TOTAL (L:45+T:15): 60 PERIODS TEXT BOOKS: 1. I.J Nagarath and Kothari DP, “Electrical Machines”, McGraw-Hill Education (India) Pvt Ltd 4 th Edition ,2010 2. A.K.Sawhney, “A Course in Electrical & Electronic Measurements and Instrumentation”, Dhanpat Rai and Co, 2004. REFERENCES: 1. Del Toro, “Electrical Engineering Fundamentals” Pearson Education, New Delhi, 2007. 2. W.D.Cooper & A.D.Helfrick, “Modern Electronic Instrumentation and Measurement Techniques”, 5 th Edition, PHI, 2002. 3. John Bird, “Electrical Circuit Theory and Technology”, Elsevier, First Indian Edition, 2006. 4. Thereja .B.L, “Fundamentals of Electrical Engineering and Electronics”, S Chand & Co Ltd, 2008. 5. H.S.Kalsi, “Electronic Instrumentation”, Tata Mc Graw-Hill Education, 2004. 6. J.B.Gupta, “Measurements and Instrumentation”, S K Kataria & Sons, Delhi, 2003. EE6352 ELECTRICAL ENGINEERING AND INSTRUMENTATION UNIT I DC MACHINES 1.1 Three Phase Circuits, A Review Polyphase System Circuit or system in which AC sources operate at the same frequency but different phases are known as polyphase. Two Phase System A generator consists of two coils placed perpendicular to each other. The voltage generated by one lags the other by 90. Three Phase System A generator consists of three coils placed 120 apart. The voltage generated are equal in magnitude but, out of phase by 120. Three phase is the most economical polyphase system. Importance of Three Phase System Uniform power transmission and less vibration of three phase machines. The instantaneous power in a 3 system can be constant (not pulsating). High power motors prefer a steady torque especially one created by a rotating magnetic field. Three phase system is more economical than the single phase. The amount of wire required for a three phase system is less than required for an equivalent single phase system. Three Phase Generation Fig. 1.1 Three phase generator Working The generator consists of a rotating magnet (rotor) surrounded by a stationary winding (stator). SCE 1 ECE EE6352 ELECTRICAL ENGINEERING AND INSTRUMENTATION Three separate windings or coils with terminals a-a’, b-b’, and c-c’ are physically placed 120 apart around the stator. As the rotor rotates, its magnetic field cuts the flux from the three coils and induces voltages in the coils. The induced voltage have equal magnitude but out of phase by 120. Three-Phase Waveform Fig. 1.2 Three phase waveform Three Phase Quantities Balanced 3 Voltages Balanced three phase voltages: Same magnitude (VM ) 120 phase shift Balanced 3 Currents Balanced three phase currents: Same magnitude (IM ) 120 phase shift SCE 2 ECE EE6352 ELECTRICAL ENGINEERING AND INSTRUMENTATION Phase Sequence Positive Sequence Van VM 0 Vbn VM 120 Vcn VM 120 Fig. 1.3 Positive Sequence Negative Sequence Van VM 0 Vbn VM 120 Vcn VM 120 Fig. 1.4 Negative Sequence SCE 3 ECE EE6352 ELECTRICAL ENGINEERING AND INSTRUMENTATION POWER The instantaneous power is constant. p(t) pa (t) pb (t) pc (t) V I 3 M M cos 2 3Vrms Irms cos( ) Three Phase Connection Source-Load Connection WYE Connection Fig. 1.5 WYE Connection SCE 4 ECE EE6352 ELECTRICAL ENGINEERING AND INSTRUMENTATION WYE Connected Load Fig. 1.6 WYE Connected Load Balanced Y-Y Connection Fig. 1.7 Balanced Y-Y Connection Phase Currents and Line Currents In Y-Y system, line current is equal to phase current, IL = IP Delta Connection Delta Connected Sources Fig. 1.8 Delta Connected Sources SCE 5 ECE EE6352 ELECTRICAL ENGINEERING AND INSTRUMENTATION DELTA Connected Load Fig. 1.9 Delta Connected Load Balanced - Connection Fig. 1.10 Balanced - Connection PHASE VOLTAGE AND LINE VOLTAGE In - system, line voltages are equal to phase voltages: VL = VP SCE 6 ECE EE6352 ELECTRICAL ENGINEERING AND INSTRUMENTATION Power Measurement in a Three Phase Circuit Using Two-Wattmeter Method Fig. 1.11 Circuit Diagram Phasor Diagram Fig. 1.12 Phasor Diagram The reading of the first wattmeter is, The reading of the second wattmeter is, The sum of the two wattmeter readings is, SCE 7 ECE EE6352 ELECTRICAL ENGINEERING AND INSTRUMENTATION The difference of the two wattmeter readings is, Power factor (cosф) can be determined using the above expression.