The document discusses alternating current circuits and provides learning objectives and specific objectives about alternating current waveforms. It defines key terms like frequency, amplitude, average value, maximum value, and root mean square value. It explains how an alternator generates a sine wave alternating current through a rotating coil in a magnetic field. The current periodically changes direction with each half rotation of the coil.
This document provides an overview of basic electrical engineering concepts including charge, current, voltage, circuits, network elements, sources, superposition theorem, Thevenin's theorem, Norton's theorem, and maximum power transfer theorem. Key points include:
- Current is the rate of charge flow measured in amperes. Voltage is the potential difference measured in volts.
- Circuits contain both active elements that supply energy (sources) and passive elements that consume energy.
- Superposition and source transformation theorems allow analysis of circuits containing multiple sources.
- Thevenin's and Norton's theorems convert circuits to equivalent circuits with a single voltage or current source.
- Maximum power is delivered to a load when
- Alternating current changes direction periodically in a sine wave pattern. The frequency is measured in Hertz (Hz), typically 50 or 60 Hz.
- AC can transmit power over longer distances with less power loss than direct current. AC voltages can be increased or decreased using transformers.
- Important AC terms include root mean square (RMS) value, phase angle, impedance, and resonance. Resonance occurs when the capacitive and inductive reactances cancel out, resulting in maximum current. Circuits can resonate in series or parallel configurations.
DC-DC converters are circuits that convert a DC voltage to another DC voltage level. They use switching elements like transistors and power switches to efficiently step up or step down voltage. The buck converter is a common DC-DC converter topology that can step down voltage. It uses a switch, inductor, diode, and capacitor. By periodically opening and closing the switch, the inductor filters the output to produce a lower average voltage. The output voltage of an ideal buck converter is equal to the input voltage multiplied by the duty cycle of the switch. Real converters have non-ideal components that cause additional voltage ripple. Proper component selection and design considerations are needed to minimize ripple.
This document discusses fundamentals of electric circuits including basic concepts such as units of measurement, electric charge, current, voltage, power and energy. It describes circuit elements including passive elements like resistors, capacitors and inductors as well as active elements such as independent voltage and current sources and dependent sources. Independent sources provide a specified voltage or current regardless of the circuit, while dependent sources have an output that depends on another voltage or current in the circuit. The document also provides examples of calculating voltage using different source types.
This document discusses fundamentals of alternating current (AC), including:
- AC voltage is generated as sinusoidal waves by power plants and used worldwide.
- Key definitions for AC waves include waveform, instantaneous value, peak amplitude, peak-to-peak value, cycle, period, and frequency.
- The basic mathematical form for a sinusoidal AC waveform is y = A sin(ωt), where A is the amplitude and ωt represents angular displacement over time.
- Root mean square (RMS) value represents the effective or heating value of AC and is calculated as the square root of the mean of the squares of the instantaneous values over one cycle.
- Average value of a symmetrical AC waveform is
This Slide is made of many important information which are very easily discussed in this slide briefly. I hope, after watching this slide , you will get some analytical information on Alternative Current(AC).Actually, this slide was made for my University Presentation.
This document discusses parallel resonance in an electrical circuit. It defines parallel resonance as occurring when circuit elements are connected in parallel with their inductance and capacitance, causing impedance to rise to a maximum at the resonant frequency. The resonant frequency is where the inductive and capacitive reactances are equal. At resonance, the parallel circuit acts resistive and the impedance is at its peak while the current is at its minimum. Key characteristics of a parallel resonant circuit including impedance, current, susceptance, and bandwidth are explained.
This chapter discusses impedance in alternating current circuits. It explains the characteristics and calculations for resistive-inductive and resistive-capacitive series circuits, including the phase relationships between voltage and current. Several example calculations of voltage, current, impedance and reactance in AC circuits are shown. The chapter concludes with a summary of key points and a preview of the next lesson.
This document provides an overview of basic electrical engineering concepts including charge, current, voltage, circuits, network elements, sources, superposition theorem, Thevenin's theorem, Norton's theorem, and maximum power transfer theorem. Key points include:
- Current is the rate of charge flow measured in amperes. Voltage is the potential difference measured in volts.
- Circuits contain both active elements that supply energy (sources) and passive elements that consume energy.
- Superposition and source transformation theorems allow analysis of circuits containing multiple sources.
- Thevenin's and Norton's theorems convert circuits to equivalent circuits with a single voltage or current source.
- Maximum power is delivered to a load when
- Alternating current changes direction periodically in a sine wave pattern. The frequency is measured in Hertz (Hz), typically 50 or 60 Hz.
- AC can transmit power over longer distances with less power loss than direct current. AC voltages can be increased or decreased using transformers.
- Important AC terms include root mean square (RMS) value, phase angle, impedance, and resonance. Resonance occurs when the capacitive and inductive reactances cancel out, resulting in maximum current. Circuits can resonate in series or parallel configurations.
DC-DC converters are circuits that convert a DC voltage to another DC voltage level. They use switching elements like transistors and power switches to efficiently step up or step down voltage. The buck converter is a common DC-DC converter topology that can step down voltage. It uses a switch, inductor, diode, and capacitor. By periodically opening and closing the switch, the inductor filters the output to produce a lower average voltage. The output voltage of an ideal buck converter is equal to the input voltage multiplied by the duty cycle of the switch. Real converters have non-ideal components that cause additional voltage ripple. Proper component selection and design considerations are needed to minimize ripple.
This document discusses fundamentals of electric circuits including basic concepts such as units of measurement, electric charge, current, voltage, power and energy. It describes circuit elements including passive elements like resistors, capacitors and inductors as well as active elements such as independent voltage and current sources and dependent sources. Independent sources provide a specified voltage or current regardless of the circuit, while dependent sources have an output that depends on another voltage or current in the circuit. The document also provides examples of calculating voltage using different source types.
This document discusses fundamentals of alternating current (AC), including:
- AC voltage is generated as sinusoidal waves by power plants and used worldwide.
- Key definitions for AC waves include waveform, instantaneous value, peak amplitude, peak-to-peak value, cycle, period, and frequency.
- The basic mathematical form for a sinusoidal AC waveform is y = A sin(ωt), where A is the amplitude and ωt represents angular displacement over time.
- Root mean square (RMS) value represents the effective or heating value of AC and is calculated as the square root of the mean of the squares of the instantaneous values over one cycle.
- Average value of a symmetrical AC waveform is
This Slide is made of many important information which are very easily discussed in this slide briefly. I hope, after watching this slide , you will get some analytical information on Alternative Current(AC).Actually, this slide was made for my University Presentation.
This document discusses parallel resonance in an electrical circuit. It defines parallel resonance as occurring when circuit elements are connected in parallel with their inductance and capacitance, causing impedance to rise to a maximum at the resonant frequency. The resonant frequency is where the inductive and capacitive reactances are equal. At resonance, the parallel circuit acts resistive and the impedance is at its peak while the current is at its minimum. Key characteristics of a parallel resonant circuit including impedance, current, susceptance, and bandwidth are explained.
This chapter discusses impedance in alternating current circuits. It explains the characteristics and calculations for resistive-inductive and resistive-capacitive series circuits, including the phase relationships between voltage and current. Several example calculations of voltage, current, impedance and reactance in AC circuits are shown. The chapter concludes with a summary of key points and a preview of the next lesson.
The document discusses three-phase circuits and provides information on:
- The advantages of three-phase supply systems such as higher efficiency of power transfer and smoother load characteristics.
- Key concepts like phase sequence, balanced/unbalanced supply and load, and the relationships between line and phase voltages and currents.
- How to calculate power in a balanced three-phase system and use two wattmeters to measure total power and power factor.
Voltage Divider and Current Divider Rule.pptxnivi55
The document discusses voltage divider and current divider rules for series and parallel circuits. For a series circuit, the voltage across each resistor is equal to the total supply voltage multiplied by the ratio of that resistor's value to the total resistance. For a parallel circuit, the current through each branch is equal to the total circuit current multiplied by the ratio of the opposite branch's resistance to the total resistance. Examples are given to demonstrate calculating voltages and currents using these rules.
The document discusses dot convention in coupled circuits. It explains that dot convention specifies the voltage polarity at the dotted terminal of a coil. If current enters the dotted terminal, it induces a positive voltage in another coupled coil's dotted terminal; if it exits the dotted terminal, it induces a negative voltage. Coupling can be electrical, through a physical connection, or magnetic, without connection. Electrical coupling is classified as aiding if currents enter dotted terminals, or opposing if one exits and one enters. Magnetic coupling also has aiding and opposing types based on dotted terminal current direction.
This document summarizes control of active and reactive power in a power system. It discusses that active power control is related to frequency control, while reactive power control is related to voltage control. It then discusses how active power and frequency are controlled through load-frequency control (LFC) to maintain a constant frequency for satisfactory power system operation. The document also discusses generator response to load changes and how speed governing works to reduce speed variations through a transfer function relationship between electrical and mechanical torques. It describes how system load responds to frequency deviations and provides an overall system block diagram.
1. Semiconductors like silicon and germanium can be classified as conductors, insulators, or semiconductors based on their atomic structure and energy bands. Their conductivity can be increased through doping with impurities.
2. A diode is a basic semiconductor device made of doped silicon with a pn junction. It allows current to flow easily in one direction but blocks it in the other. Diodes are used as rectifiers to convert alternating current into direct current.
3. Rectifiers use diodes in various circuit configurations like half-wave, full-wave, and bridge circuits to extract the positive portions of the input waveform and produce a pulsing direct current output. Three-
The document discusses operational amplifiers (op amps) and their applications in different circuit configurations:
1) An op amp is an electronic device that can perform mathematical operations like addition, subtraction, etc. It has high gain, very high input impedance, and very low output impedance.
2) Common op amp circuit configurations include the inverting amplifier, non-inverting amplifier, summing amplifier, difference amplifier, and instrumentation amplifier.
3) The summing amplifier produces an output voltage that is the weighted sum of its input voltages. The difference amplifier amplifies the difference between its two input voltages and rejects any components that are common to both inputs.
1) Effective current in an AC circuit is 0.707 times the maximum current. Effective voltage is 0.707 times the maximum voltage.
2) Inductive reactance is directly proportional to frequency and inductance. Capacitive reactance is inversely proportional to frequency and capacitance.
3) Impedance is the total opposition to current flow in an AC circuit consisting of resistance and reactance. Power is consumed only by the resistive component of impedance and is proportional to the cosine of the phase angle.
This presentation introduces rectifiers and was presented by Md. Tanvir Hossain Tushar, a first year Applied Chemistry and Chemical Engineering student. It defines a rectifier as an electrical device that converts alternating current to direct current using diodes. The presentation discusses half-wave and full-wave rectifiers, the types of full-wave rectifiers, and common uses of rectifiers such as in DC power supplies, radio signal detection, and high voltage DC power transmission.
This document provides information about two-port network parameters including Z, Y, H, and ABCD parameters. It defines a two-port network as having two ports for input and output with two terminals pairs. The document explains that the parameters relate the terminal voltages and currents and can be determined by setting the input or output port to open or short circuit conditions. Examples are given to show how to calculate the parameters for simple circuits. Key points are summarized in less than 3 sentences.
This chapter provides complete solution of of first, Second order differential equations of series & parallel R-L, R-C, R-L-C circuits, bu using different methods.
A circuit consists of electrical elements connected in a closed loop to allow current flow. Key concepts include:
- Current is the flow of electric charge. Voltage is electrical potential difference and power is the rate of work done.
- Circuits have active elements like voltage and current sources that supply energy and passive elements like resistors, inductors and capacitors that receive energy.
- Kirchhoff's laws state that the algebraic sum of voltages around any loop is zero and the algebraic sum of currents at any node is zero.
- Resistors in series add, resistors in parallel calculate using reciprocal formula. Source transformations allow representing one source type as another while maintaining terminal characteristics.
Semiconductors like silicon and germanium can be used to create diodes and transistors. A diode allows current to pass in only one direction, acting like a one-way valve. By adding impurities to an intrinsic semiconductor, n-type and p-type materials can be created. A PN junction diode consists of an n-type and p-type material joined together. Diodes can be used in rectifier circuits to convert AC to DC and in voltage regulators. Zener diodes operate in the reverse breakdown region to provide a stable reference voltage.
1) DC circuits can be linear or non-linear depending on whether their parameters such as resistance, inductance, and capacitance remain constant or change with voltage and current.
2) Kirchhoff's laws, including Kirchhoff's current law and Kirchhoff's voltage law, are important laws for analyzing electrical circuits and networks.
3) Circuit analysis methods such as mesh analysis, nodal analysis, and Thevenin's theorem allow circuits to be simplified to aid in calculation of voltage and current.
This comprehensive text on Network Analysis and Synthesis is designed for undergraduate students of Electronics and Communication Engineering, Electrical and Electronics Engineering, Electronics and Instrumentation Engineering, Electronics and Computer Engineering and Biomedical Engineering. The book will also be useful to AMIE and IETE students. Buy Now: https://bit.ly/2WmA7is
The complete list of thyristor family members include diac (bidirectional diode thyristor), triac (bidirectional triode thyristor), SCR (silicon controlled rectifier), Shockley diode, SCS (silicon controlled switch), SBS (silicon bilateral switch), SUS (silicon unilateral switch) also known as complementary SCR or CSCR, LASCR (light activated SCR), LAS (light activated switch) and LASCS (light activated SCS).
This document provides an introduction to basic electrical concepts including charge, current, voltage, power, energy, and circuit elements. It defines the international system of units used in electrical engineering. Key concepts covered include defining the ampere as the unit of current representing the flow of electric charge, defining voltage as the work required to move a unit of charge from one point to another, and defining power as the rate at which energy is transferred. Circuit analysis techniques are introduced for studying the behavior of electric circuits.
A diode is a two-terminal electronic component that allows current to flow in only one direction. It is used to convert alternating current to direct current through a process called rectification. Diodes come in various types including laser diodes, light emitting diodes, Zener diodes, and silicon diodes. Rectification uses diodes to convert AC to DC through either half-wave or full-wave rectification circuits. Zener diodes are used in the reverse bias mode as voltage regulators. Photodiodes generate current or voltage when illuminated by light and are used in applications like machine vision, range finding, and medical diagnostics.
This document discusses resonance circuits and their applications. Resonance occurs when the capacitive and inductive reactances are equal, resulting in a purely resistive impedance. Key parameters of resonance circuits include the resonance frequency, half-power frequencies, bandwidth, and quality factor. Resonance circuits are useful for constructing filters and are used in applications like bandpass and bandstop filters, which allow only certain frequency ranges to pass.
Here are the steps to solve for the transfer function G(s) = X2(s)/F(s) for the given system:
1. Draw the free body diagrams for both masses M1 and M2 showing all the forces acting on each mass.
2. Write the Newton's second law equation for M1:
(M1s2 + f1vs + k1)X1(s) - k2(X1(s) - X2(s)) = 0
3. Write the Newton's second law equation for M2:
-k2(X1(s) - X2(s)) + (M2s2 + f2vs + k
This document discusses voltage measurements and conversions between different voltage measurements. It shows that the root mean square (Vrms) voltage is 0.707 times the peak (Vmax) voltage and 0.354 times the peak-to-peak (Vp-p) voltage. As an example, it calculates that for a 240Vrms power system, the peak voltage would be 339V and the peak-to-peak voltage would be 678V.
This document provides reading material on synchronous machines for electrical engineering students. It includes an overview of salient pole synchronous machines, the two-reaction circuit theory model, and determination of synchronous reactances. Key points covered include:
- The two-reaction theory model which resolves the armature MMF into direct and quadrature axis components
- The equivalent circuit model and phasor diagrams of salient pole synchronous machines
- Methods for determining the direct-axis and quadrature-axis synchronous reactances using a slip test
- The significance of the short-circuit ratio for synchronous machines
The document discusses three-phase circuits and provides information on:
- The advantages of three-phase supply systems such as higher efficiency of power transfer and smoother load characteristics.
- Key concepts like phase sequence, balanced/unbalanced supply and load, and the relationships between line and phase voltages and currents.
- How to calculate power in a balanced three-phase system and use two wattmeters to measure total power and power factor.
Voltage Divider and Current Divider Rule.pptxnivi55
The document discusses voltage divider and current divider rules for series and parallel circuits. For a series circuit, the voltage across each resistor is equal to the total supply voltage multiplied by the ratio of that resistor's value to the total resistance. For a parallel circuit, the current through each branch is equal to the total circuit current multiplied by the ratio of the opposite branch's resistance to the total resistance. Examples are given to demonstrate calculating voltages and currents using these rules.
The document discusses dot convention in coupled circuits. It explains that dot convention specifies the voltage polarity at the dotted terminal of a coil. If current enters the dotted terminal, it induces a positive voltage in another coupled coil's dotted terminal; if it exits the dotted terminal, it induces a negative voltage. Coupling can be electrical, through a physical connection, or magnetic, without connection. Electrical coupling is classified as aiding if currents enter dotted terminals, or opposing if one exits and one enters. Magnetic coupling also has aiding and opposing types based on dotted terminal current direction.
This document summarizes control of active and reactive power in a power system. It discusses that active power control is related to frequency control, while reactive power control is related to voltage control. It then discusses how active power and frequency are controlled through load-frequency control (LFC) to maintain a constant frequency for satisfactory power system operation. The document also discusses generator response to load changes and how speed governing works to reduce speed variations through a transfer function relationship between electrical and mechanical torques. It describes how system load responds to frequency deviations and provides an overall system block diagram.
1. Semiconductors like silicon and germanium can be classified as conductors, insulators, or semiconductors based on their atomic structure and energy bands. Their conductivity can be increased through doping with impurities.
2. A diode is a basic semiconductor device made of doped silicon with a pn junction. It allows current to flow easily in one direction but blocks it in the other. Diodes are used as rectifiers to convert alternating current into direct current.
3. Rectifiers use diodes in various circuit configurations like half-wave, full-wave, and bridge circuits to extract the positive portions of the input waveform and produce a pulsing direct current output. Three-
The document discusses operational amplifiers (op amps) and their applications in different circuit configurations:
1) An op amp is an electronic device that can perform mathematical operations like addition, subtraction, etc. It has high gain, very high input impedance, and very low output impedance.
2) Common op amp circuit configurations include the inverting amplifier, non-inverting amplifier, summing amplifier, difference amplifier, and instrumentation amplifier.
3) The summing amplifier produces an output voltage that is the weighted sum of its input voltages. The difference amplifier amplifies the difference between its two input voltages and rejects any components that are common to both inputs.
1) Effective current in an AC circuit is 0.707 times the maximum current. Effective voltage is 0.707 times the maximum voltage.
2) Inductive reactance is directly proportional to frequency and inductance. Capacitive reactance is inversely proportional to frequency and capacitance.
3) Impedance is the total opposition to current flow in an AC circuit consisting of resistance and reactance. Power is consumed only by the resistive component of impedance and is proportional to the cosine of the phase angle.
This presentation introduces rectifiers and was presented by Md. Tanvir Hossain Tushar, a first year Applied Chemistry and Chemical Engineering student. It defines a rectifier as an electrical device that converts alternating current to direct current using diodes. The presentation discusses half-wave and full-wave rectifiers, the types of full-wave rectifiers, and common uses of rectifiers such as in DC power supplies, radio signal detection, and high voltage DC power transmission.
This document provides information about two-port network parameters including Z, Y, H, and ABCD parameters. It defines a two-port network as having two ports for input and output with two terminals pairs. The document explains that the parameters relate the terminal voltages and currents and can be determined by setting the input or output port to open or short circuit conditions. Examples are given to show how to calculate the parameters for simple circuits. Key points are summarized in less than 3 sentences.
This chapter provides complete solution of of first, Second order differential equations of series & parallel R-L, R-C, R-L-C circuits, bu using different methods.
A circuit consists of electrical elements connected in a closed loop to allow current flow. Key concepts include:
- Current is the flow of electric charge. Voltage is electrical potential difference and power is the rate of work done.
- Circuits have active elements like voltage and current sources that supply energy and passive elements like resistors, inductors and capacitors that receive energy.
- Kirchhoff's laws state that the algebraic sum of voltages around any loop is zero and the algebraic sum of currents at any node is zero.
- Resistors in series add, resistors in parallel calculate using reciprocal formula. Source transformations allow representing one source type as another while maintaining terminal characteristics.
Semiconductors like silicon and germanium can be used to create diodes and transistors. A diode allows current to pass in only one direction, acting like a one-way valve. By adding impurities to an intrinsic semiconductor, n-type and p-type materials can be created. A PN junction diode consists of an n-type and p-type material joined together. Diodes can be used in rectifier circuits to convert AC to DC and in voltage regulators. Zener diodes operate in the reverse breakdown region to provide a stable reference voltage.
1) DC circuits can be linear or non-linear depending on whether their parameters such as resistance, inductance, and capacitance remain constant or change with voltage and current.
2) Kirchhoff's laws, including Kirchhoff's current law and Kirchhoff's voltage law, are important laws for analyzing electrical circuits and networks.
3) Circuit analysis methods such as mesh analysis, nodal analysis, and Thevenin's theorem allow circuits to be simplified to aid in calculation of voltage and current.
This comprehensive text on Network Analysis and Synthesis is designed for undergraduate students of Electronics and Communication Engineering, Electrical and Electronics Engineering, Electronics and Instrumentation Engineering, Electronics and Computer Engineering and Biomedical Engineering. The book will also be useful to AMIE and IETE students. Buy Now: https://bit.ly/2WmA7is
The complete list of thyristor family members include diac (bidirectional diode thyristor), triac (bidirectional triode thyristor), SCR (silicon controlled rectifier), Shockley diode, SCS (silicon controlled switch), SBS (silicon bilateral switch), SUS (silicon unilateral switch) also known as complementary SCR or CSCR, LASCR (light activated SCR), LAS (light activated switch) and LASCS (light activated SCS).
This document provides an introduction to basic electrical concepts including charge, current, voltage, power, energy, and circuit elements. It defines the international system of units used in electrical engineering. Key concepts covered include defining the ampere as the unit of current representing the flow of electric charge, defining voltage as the work required to move a unit of charge from one point to another, and defining power as the rate at which energy is transferred. Circuit analysis techniques are introduced for studying the behavior of electric circuits.
A diode is a two-terminal electronic component that allows current to flow in only one direction. It is used to convert alternating current to direct current through a process called rectification. Diodes come in various types including laser diodes, light emitting diodes, Zener diodes, and silicon diodes. Rectification uses diodes to convert AC to DC through either half-wave or full-wave rectification circuits. Zener diodes are used in the reverse bias mode as voltage regulators. Photodiodes generate current or voltage when illuminated by light and are used in applications like machine vision, range finding, and medical diagnostics.
This document discusses resonance circuits and their applications. Resonance occurs when the capacitive and inductive reactances are equal, resulting in a purely resistive impedance. Key parameters of resonance circuits include the resonance frequency, half-power frequencies, bandwidth, and quality factor. Resonance circuits are useful for constructing filters and are used in applications like bandpass and bandstop filters, which allow only certain frequency ranges to pass.
Here are the steps to solve for the transfer function G(s) = X2(s)/F(s) for the given system:
1. Draw the free body diagrams for both masses M1 and M2 showing all the forces acting on each mass.
2. Write the Newton's second law equation for M1:
(M1s2 + f1vs + k1)X1(s) - k2(X1(s) - X2(s)) = 0
3. Write the Newton's second law equation for M2:
-k2(X1(s) - X2(s)) + (M2s2 + f2vs + k
This document discusses voltage measurements and conversions between different voltage measurements. It shows that the root mean square (Vrms) voltage is 0.707 times the peak (Vmax) voltage and 0.354 times the peak-to-peak (Vp-p) voltage. As an example, it calculates that for a 240Vrms power system, the peak voltage would be 339V and the peak-to-peak voltage would be 678V.
This document provides reading material on synchronous machines for electrical engineering students. It includes an overview of salient pole synchronous machines, the two-reaction circuit theory model, and determination of synchronous reactances. Key points covered include:
- The two-reaction theory model which resolves the armature MMF into direct and quadrature axis components
- The equivalent circuit model and phasor diagrams of salient pole synchronous machines
- Methods for determining the direct-axis and quadrature-axis synchronous reactances using a slip test
- The significance of the short-circuit ratio for synchronous machines
armature reaction effect and minimization methodsNayan Solanki
This document discusses armature reaction in DC machines and methods to minimize it. It describes how armature reaction demagnetizes and distorts the main magnetic flux, weakening it in some areas and strengthening it in others. Compensating windings and interpoles are introduced to counteract the cross-magnetizing effect. Commutation, the process of reversing current in armature coils, is also covered. Resistance commutation using carbon brushes and emf commutation using interpoles are two methods discussed to improve commutation and reduce sparking. Interpoles produce a reversing emf that neutralizes reactance voltage during commutation for smooth current reversal.
Armature reaction in a DC machine is the effect of armature flux on the main field flux. It has two undesirable effects - it demagnetizes the main flux and distorts the main flux. This reduces generated voltage and torque and influences commutation limits. Methods to reduce armature reaction include compensating windings and interpoles, which produce fields opposing the armature flux effects.
This document discusses various protection schemes for alternators, including differential protection, differential protection for alternators with high resistance grounding, negative phase sequence protection, balanced earth fault protection, and overcurrent protection. It describes how each protection scheme detects faults or unbalanced loading conditions in the alternator. Differential protection compares currents on each side of the alternator winding and trips if they are unequal due to an internal fault. Other schemes like negative phase sequence and earth fault protection are used to detect unbalanced or ground faults that may not be caught by differential protection.
Methods of cooling of electrical machinesAAAbinash
This document discusses various methods of cooling electrical machines. Cooling is needed to dissipate heat from losses during energy conversion and prevent temperatures from exceeding safe levels. Common coolants include water, ethylene glycol and specialized liquids. Heat exchangers transfer heat between primary and secondary coolants. Ventilation methods depend on machine size and include radial, axial and combined ducts. Larger machines often use water or hydrogen as direct coolants. Proper cooling increases efficiency, power output and lifespan of electrical machines.
1. The document discusses the syllabus and basics of synchronous generators or alternators.
2. Synchronous generators convert mechanical power into electrical power through electromagnetic induction. They are used as the primary source of electrical energy in large power grids.
3. The basic parts are the rotor with field windings, and the stator with 3-phase armature windings. The frequency of the induced EMF depends on the rotor speed and number of poles.
This document discusses various protections provided for alternators, including mechanical protections from prime mover failure, field failure, overcurrent, overspeed, and overvoltage, as well as electrical protections from unbalanced loading and stator winding faults. It describes different protection mechanisms like differential protection, balanced earth fault protection, and inter-turn fault protection that are used to protect against faults in the alternator windings or unbalanced loading. The document emphasizes the importance of alternator protection given their high individual cost and importance in power generation.
The document is a presentation on single phase induction motors by Susmit Sarkar. It discusses different starting methods for single phase induction motors including split phase starting, shaded pole starting, and reluctance starting. It explains split phase and capacitor start and run starting methods used in fans, air conditioners, and compressors. The presentation also covers shaded pole starting used in tape recorders and projectors. It discusses torque speed characteristics and provides the equivalent circuit diagram of a single phase induction motor using double revolving field theory.
- A synchronous machine is an important electric machine that uses electromechanical energy conversion. Synchronous generators are used in power plants and synchronous motors are used widely in industries.
- The main components are a stator, rotor, field windings on the rotor, and armature windings on the stator. The rotor rotates inside the stator with an air gap.
- Synchronous machines use distributed multi-phase armature windings on the stator that are connected in a star or delta configuration. The windings are distributed around the stator slots to produce a more sinusoidal induced electromotive force.
In the presentation all about, the operation of Parallel System of two alternators and in the sense how in power plants, they utilize it in their sensitivity to produce more electricity at one operation and after all how they reduce the per cost of electricity unit. I hope, this presentation helpfull to all the Engineering Students.
This document provides information on various types of single-phase induction motors. It discusses the construction and working of split-phase induction motors, capacitor start induction motors, permanent capacitor motors, shaded-pole motors, universal motors, and repulsion motors. The key points covered are:
- Single-phase induction motors require special mechanisms to produce a rotating magnetic field and make them self-starting.
- Common self-starting methods include using an auxiliary starting winding, a capacitor, or shading coils.
- Split-phase motors use a starting winding to produce a phase difference between currents. Capacitor motors add a capacitor to further improve starting torque.
- Shaded-pole motors produce a rotating
Synchronous machines have two sets of windings - a three-phase armature winding on the stationary stator and a DC field winding on the rotating rotor. The rotor can have either a salient pole or cylindrical structure. Large generators use brushless excitation systems to avoid maintenance issues associated with slip rings and brushes. Excitation is provided by a small AC generator (brushless exciter) mounted on the stator whose output is rectified to supply DC current to the main field winding. Proper cooling is required to dissipate heat generated in the windings.
This document discusses the synchronous motor, including its introduction, construction, and operating principle. A synchronous motor runs at a constant synchronous speed determined by the supply frequency. It consists of a stator winding and a rotor with salient poles. The rotor is excited by direct current to synchronize with the rotating stator field. A synchronous motor is not self-starting and requires an auxiliary method like an induction motor principle or separate starting motor.
This document discusses different types of starters for 3-phase induction motors, including their operation and advantages/disadvantages. It describes stator resistance, auto-transformer, star-delta, rotor resistance, and direct online starters. The star-delta starter connects the motor in a star configuration at start to reduce voltage and current by 1/3, then switches to delta for run. The direct online starter connects the motor directly to full voltage, providing maximum torque but also maximum starting current of 6-8 times full load current. Variable frequency drives control motor speed by varying supply frequency and voltage.
An alternator is an electrical generator that converts mechanical energy to electrical energy. It uses a rotating magnetic field with a stationary armature. The working principle relies on Faraday's law of electromagnetic induction. As the armature rotates within the magnetic field, an alternating current is produced. The main components are the stator with stationary armature windings and the rotor with a rotating magnetic field supplied by a DC current. Armature reaction causes the magnetic field to be distorted by the armature current. Alternators have various applications including in automobiles, power plants, and for providing regenerative braking in induction motors. Induction generators can also be used to convert the rotational energy of windmills into electrical energy.
Armature reaction is the distortion of the magnetic field in a DC generator caused by the magnetic field produced by current in the armature. This reaction shifts the neutral plane and affects commutation. It can reduce the induced EMF and torque. Methods to reduce armature reaction include using poles with high reluctance at the tips, laminated pole shoes, reducing armature flux through field pole laminations, having a strong main magnetic field, using interpoles, and adding compensating windings.
This document discusses phasor diagrams and their use in analyzing AC circuits. It begins by defining phasors and explaining that phasor diagrams represent the magnitude and phase of sinusoidal voltages and currents. The document then examines phasor diagrams for pure resistive, inductive, and capacitive circuits. In a pure resistive circuit, the current and voltage are in phase. In a pure inductive circuit, the current lags the voltage by 90 degrees. In a pure capacitive circuit, the current leads the voltage by 90 degrees. Characteristics of each type of circuit are provided along with examples of phasor diagrams.
The document discusses transformer construction, principles of operation, and testing methods to determine equivalent circuit parameters. It provides an introduction to different types of transformers and their applications. Key points covered include:
- Transformers transfer power from one circuit to another through electromagnetic induction without a direct electrical connection between the circuits.
- Practical transformers have equivalent circuits that account for winding resistances, core losses, and leakage fluxes/inductances not present in an ideal transformer.
- Open circuit and short circuit tests are used to determine the equivalent circuit parameters like magnetizing inductance, core loss resistance, leakage reactances, and winding resistances.
1. A transformer is a device that converts alternating current (AC) of one voltage to another voltage without changing the frequency. It consists of coils wrapped around a common core and uses electromagnetic induction.
2. Nikola Tesla proposed using transformers to increase voltage for efficient power transmission over long distances, then step it back down for safe distribution and use. This system replaced the inefficient direct current system developed by Edison.
3. Transformers allow efficient transmission of power by reducing current and thus transmission losses, while maintaining the same power level. They are essential components for modern power distribution systems.
The LVDT is an inductive transducer that converts linear motion to electrical signals. It consists of a primary winding and two secondary windings placed on either side of the primary. A movable soft iron core is placed between the windings. As the core moves linearly, it induces changing voltages in the secondary windings. The difference between these voltages is proportional to the core's displacement, allowing the LVDT to accurately measure linear motion over a wide range. LVDTs have advantages like high sensitivity and ruggedness, but disadvantages such as sensitivity to stray magnetic fields. They are commonly used as secondary transducers to measure quantities that involve linear displacement.
Electromagnetic induction occurs when a changing magnetic field induces a current in a conductor. Magnetic flux is the measure of the magnetic field passing through an area. Faraday's law states that an electromotive force (EMF) is induced in a conductor when there is a change in magnetic flux over time. Transformers use this principle to change voltage levels using a primary and secondary coil wound around an iron core. Lenz's law describes how the induced current will flow in a direction that creates an opposing magnetic field to the changing field that created it.
lec 8 and 9 single phase transformer.pptxssuser76a9bc
The document discusses single phase transformers, including their construction, operation principle, ideal and non-ideal models, and methods to determine component values. A transformer transfers energy between circuits through electromagnetic induction. It has a core made of laminated silicon steel and windings wrapped around the core. Varying the primary current induces a voltage in the secondary according to Faraday's law of induction and the turns ratio. Real transformers have losses accounted for in their equivalent circuit model, which is used to analyze power flow and regulation. Component values are found through short-circuit, open-circuit, and DC tests.
This document provides an overview of transformers and their operation. It discusses:
- The history and development of transformers from the 1880s to present day
- The basic components and construction of transformers
- How an ideal transformer works based on Faraday's law of induction
- How voltages and currents are related in an ideal transformer based on turn ratios
- How real transformers approximate ideal transformer behavior
- Examples of analyzing circuits containing transformers by referring their sides
- The theory of operation for real single-phase transformers based on mutual and leakage fluxes
A transformer is a device that changes alternating current (ac) electric power at one voltage level to ac electric power at another voltage level through the action of a magnetic field. An ideal transformer is a lossless device that transfers power efficiently between its two windings. A real transformer is modeled using an equivalent circuit that accounts for power losses, including copper losses, eddy current losses, hysteresis losses, and leakage fluxes. The parameters of the equivalent circuit can be determined experimentally using open-circuit and short-circuit tests.
This document discusses magnetically coupled circuits and transformers. It defines mutual inductance and describes how it allows induction of voltage between coupled coils. It examines energy storage in coupled circuits and the coupling coefficient. Ideal and linear transformers are analyzed, including voltage transformation ratios, impedance matching applications, and using transformers for isolation. Examples are provided for calculating currents, impedances, energy, turns ratios, and matching circuits.
This document provides an overview of a lecture on DC motors. It begins with preliminary notes stating that DC motors have applications in automobiles, aircraft and portable electronics due to their ability to easily control speed. It then discusses the simplest DC machine, which consists of a single rotating loop of wire. The document explains how a voltage is induced in the rotating loop and how a commutator can be added to convert the alternating voltage to a direct voltage. It further discusses how this simplest machine demonstrates the basic principles of induced voltage, torque, and commutation that apply to real DC machines.
This document provides an overview of DC motors and discusses the simplest DC machine. It begins by explaining that DC power systems are less common today but DC motors still have applications in automobiles, aircraft, and portable electronics due to their controllability. The document then discusses the basic components and operating principles of the simplest DC machine, which consists of a single rotating loop of wire. It explains how a voltage is induced in the loop based on its motion in the magnetic field and how a commutator can be used to convert this alternating voltage to a DC voltage. The document also discusses how torque is produced in the rotating loop. Overall, the document provides a conceptual introduction to the basic components and operating principles of the simplest DC machine as
The document discusses transformers and their role in electrical distribution systems. It explains that transformers operate on the principle of mutual inductance to increase or decrease voltage. Step-up transformers are used to transmit electricity at high voltages over power lines, while step-down transformers lower the voltage for safe distribution and use. The development of efficient transformers enabled the modern electrical grid that transmits power over long distances at high voltages and distributes it locally at lower voltages.
The document discusses various analog sensors and transducers used for motion measurement in control systems. It describes potentiometers, variable inductance transducers including linear variable differential transformers (LVDTs), permanent magnet transducers, eddy current transducers, and piezoelectric transducers. It explains the operating principles and design considerations for these analog motion sensors.
A transformer is a device that changes alternating current (ac) electric power at one voltage level to ac power at another voltage level through magnetic induction. It consists of two or more coils wound around a core and linked by a magnetic field. An ideal transformer has no losses and the power input equals the power output. Real transformers have losses due to winding resistance, core losses, and leakage fluxes. The performance of real transformers can be modeled using an equivalent circuit with parameters determined from open-circuit and short-circuit tests. Transformer voltage regulation and efficiency are important performance metrics.
This document is a question paper for an Electrical and Machines Engineering examination. It contains 15 multiple choice and numerical problems covering topics like basic rotating electric machines, electromagnetic induction, transformer equivalent circuits, magnetic circuits, electric motor principles and characteristics. Students are required to answer all questions in the paper which is divided into two parts - Part A contains 10 short 2-mark questions, and Part B contains 5 long 16-mark numerical problems.
A transformer transfers electrical energy between two or more circuits through electromagnetic induction. It works on the principle of mutual induction between two or more windings due to a changing magnetic field. Transformers are used to increase or decrease alternating voltages in power applications. The primary winding is supplied with alternating current which produces a changing magnetic flux in the transformer core. This changing flux induces a changing voltage in the secondary winding due to electromagnetic induction based on Faraday's law of induction. Real transformers have losses such as core losses from hysteresis and eddy currents, as well as winding resistance losses. Transformers can be modeled using an equivalent circuit to represent these losses and other factors.
Here are the solutions to the transformer problems:
1. A transformer has 100 turns on coil 1 and 200 turns on coil 2.
i. If the voltage on coil 1 is 10 volts, the voltage on coil 2 will be 20 volts (Voltage on coil 2 = Voltage on coil 1 x Turns on coil 2/Turns on coil 1 = 10V x 200/100 = 20V)
ii. If the voltage on coil 1 is 200 volts, the voltage on coil 2 will be 400 volts (Voltage on coil 2 = Voltage on coil 1 x Turns on coil 2/Turns on coil 1 = 200V x 200/100 = 400V)
iii.
Basic concepts of electricity last two week convertedASHISH DHAMANDA
This document discusses alternating current (AC) and how it differs from direct current (DC). It explains that AC is generated from rotating magnets in generators, which produces a reversing voltage polarity over time. AC generators and motors have simpler designs than DC versions because they do not require brushes. Transformers are also discussed, which use mutual induction between coils to step voltages up or down, enabling efficient long-distance power transmission. The key advantages of AC that the document outlines are simpler generator/motor construction and enabling power distribution via step-up and step-down transformers, which is not possible with DC.
This document outlines the topics to be covered in a web authoring class test, including HTML web elements and components, HTML validation tools, cascading style sheets, web forms, and browser compatibility. The test will cover topics 1 through 12 on HTML elements, topic 14 on validation tools, topics 14 through 18 on cascading style sheets, topics 19 through 22 on web forms, and topics 23 through 26 on browser compatibility.
To publish a website, you must:
1. Create the website content locally either through manual coding or a content management system.
2. Purchase a hosting plan from a provider that includes storage, bandwidth, and a domain name.
3. Upload the website files to the hosting server using FTP client to publish the site publicly on the internet.
This document discusses how to set up and synchronize a remote website using Dreamweaver. It defines a local site as being stored on a computer's hard drive and a remote site as being stored on a web server connected to the internet. It describes using FTP, SFTP, WebDav or RDS to connect Dreamweaver to a remote site. It also explains how to synchronize files between the local and remote sites by uploading newer local files, downloading newer remote files, or ensuring both sites have the newest versions of all files.
The document discusses the importance of validating web page contents for several reasons:
1. Validation helps ensure consistent rendering across different platforms by conforming to standards.
2. Validation makes pages easier to maintain and evolve over time.
3. Validation provides greater assurance that pages will continue to work as intended with future browsers and technologies.
4. Validation helps teach good coding practices and catches mistakes, especially for beginners.
The document discusses ensuring that website content meets technical protocols by confirming content complies with standards, technology supports multimedia content, and testing content functions properly across browsers and with user interactions as intended. It also lists required skills and knowledge for website publishing such as file transfer, site testing, server operating systems, and protocols.
This document discusses web page validation and the benefits of standards-based design. It explains that the W3C provides guidelines and specifications for HTML and XHTML and offers a free online validation service. Validating checks that a web page follows the correct markup rules. Standards-based design using HTML and CSS requires less code, makes pages easier to maintain and access, improves search engine optimization, and increases compatibility with different devices.
This document discusses web page validation and the benefits of standards-based design. It explains that the W3C provides guidelines and specifications for HTML and XHTML and offers a free online validation service. Validating checks that a web page follows the correct markup rules. Standards-based design using HTML and CSS requires less code, makes pages easier to maintain and access, improves search engine optimization, and increases compatibility with different devices.
Web topic 28. w3 c standards and guidelinesCK Yang
W3C develops protocols and guidelines to ensure the long-term growth of the World Wide Web. Its standards define key parts of how the Web works. W3C's mission is to lead the Web to its full potential through developing standards and guidelines. The organization aims to promote participation and sharing of knowledge on a global scale through an open Web.
Web topic 26 browser compatibilty and securityCK Yang
The document discusses browser compatibility and the importance of testing websites across different browsers. It notes that browsers can interpret HTML and CSS differently, so pages may look different in various browsers like Internet Explorer, Firefox, Safari, and Chrome. It recommends testing websites in multiple browsers to ensure compatibility. Various tools for browser testing are also described, such as browser emulation applications, Dreamweaver, Adobe BrowserLab, and Microsoft SuperPreview. The document emphasizes the importance of browser compatibility testing to avoid layout issues and bugs.
The document discusses the need for mobile-optimized websites. It explains that mobile browsing is growing rapidly but most websites are designed for desktop use. Key differences between mobile and desktop experiences include smaller screen sizes and vertical versus horizontal orientation on phones. Limitations of mobile browsing include touch-only navigation, slower speeds, and less support for multimedia. The document recommends using responsive design techniques like media queries and separate style sheets to optimize websites for different devices.
This document discusses web browsers. It defines a web browser as software that allows users to view web pages and other online content. It lists some common web browsers like Internet Explorer, Mozilla Firefox, and Safari. It outlines features of web browsers such as spell checkers, bookmarks, and pop-up blocking. The document also notes technologies supported by browsers like Java, RSS, and XHTML and languages supported like English, German, and Spanish. It concludes by mentioning browser plugins and trends in internet statistics and users.
Web accessibility means that people with disabilities can perceive, understand, navigate, and interact with the web. It is important to ensure equal access and opportunity for all users, including those with visual, auditory, physical, speech, cognitive or neurological disabilities. Key principles of accessible design include providing alternative text for images, using headings for tables, ensuring all forms can be completed and submitted, making links meaningful without surrounding context, captioning media, and allowing users to skip repetitive content. Accessibility should be considered from the beginning of web development and evaluated throughout using tools as well as human review.
1. The document discusses form validation using JavaScript. It describes form validation as checking that a form has been filled in correctly before submission.
2. There are two main methods of form validation: client-side (using JavaScript) and server-side (using CGI scripts or ASP). Client-side validation is easier to implement but less secure, while server-side is more secure but more complex.
3. An example is given demonstrating client-side form validation using JavaScript. The validate_form() function checks if the contact name field is empty, and alerts the user if so before allowing submission.
This document discusses using JavaScript to pass information via web forms and dynamically change web pages. It covers JavaScript basics like variables, functions, alerts and prompts, and provides examples of how to use JavaScript for calculations, displaying text, working with dates, and swapping images. The document provides code snippets to demonstrate common JavaScript commands and syntax.
This document discusses HTML forms and the various form elements used to gather user input. It identifies the <form> tag which defines a form section and includes attributes like action and method. The <input> tag is used to create form controls like text boxes, checkboxes, radio buttons, etc. Other tags covered are <textarea> for multi-line text, <select> and <option> for drop-down menus, and <submit> for submitting the form. The document provides examples of how to use these tags to build interactive forms.
This document discusses HTML forms, which allow users to enter and submit information through a web page. It describes the <form>, <input>, <textarea>, and <select> tags used to build forms. <form> defines a form section and includes attributes like action and method. <input> creates different form controls like text boxes, checkboxes, and buttons. <textarea> makes multi-line text fields. <select> produces drop-down menus, with <option> creating the menu items. The document explains how to use these tags to build basic forms that gather and submit user input.
This document discusses conflict resolution in CSS. It explains that embedded styles will override conflicting external styles due to the cascade hierarchy. Only directly conflicting styles are overridden - the browser tries to use both. Specificity, inheritance, and the order of linked styles also determine which styles take precedence. Ids have the highest specificity.
The document discusses various topics in CSS including font families, the box model, text formatting and positioning, and table formatting. It defines five font families - serif, sans-serif, script, monospace, and fantasy - and describes their common uses. It also explains the box model of margins, padding, borders, and background, and properties for text alignment, positioning, and table styling.
This document provides guidance on using a standardized workflow to create CSS web pages. It recommends starting with content and basic HTML before working on CSS styles from the top of the page down. The CSS should be kept simple with a master style sheet that resets defaults, formats text elements consistently, and defines common reusable classes. Following this workflow helps create CSS pages in half the time by establishing a clean base and reusable styles.
This document discusses four theories of Cascading Style Sheets (CSS):
1. Cascade theory describes how the order and placement of CSS rules affects styling.
2. Inheritance theory describes how rules can affect previously declared rules.
3. Descendant theory describes how rules can target elements based on their relationship to other elements.
4. Specificity theory describes how browsers determine which rules to apply when rules conflict based on an element's specificity weight.
Best Competitive Marble Pricing in Dubai - ☎ 9928909666Stone Art Hub
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Anny Serafina Love - Letter of Recommendation by Kellen Harkins, MS.AnnySerafinaLove
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HOW TO START UP A COMPANY A STEP-BY-STEP GUIDE.pdf46adnanshahzad
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2. Chapter 11 – Alternating Current Circuits
Lesson Objectives
Upon completion of this topic, you should be able to:
Explain and calculate the fundamentals of alternating
current waveform.
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3. Chapter 11 – Alternating Current Circuits
Specific Objectives
Students should be able to :
Describe the basic construction of a simple alternator.
Describe the characteristics of an alternating quantity as
fluctuating over a given period of time.
Define the following terms with reference to an alternating
quantity :
Frequency
Average value
Instantaneous value
Maximum value
IT2001PA Engineering Essentials (1/2)
4. Chapter 11 – Alternating Current Circuits
Specific Objectives
Students should be able to :
State that the frequency of the generated emf is
proportional to the speed and number of poles of the
alternator.
Explain the term Root Mean Square (RMS) value with
reference to an alternating current.
State the following equations for a sinusoidal waveform :
RMS value = 0.707 x Maximum value
Average value = 0.637 x Maximum value
IT2001PA Engineering Essentials (1/2)
5. Chapter 11 – Alternating Current Circuits
Alternating Waveform
Alternating Current (ac)
current that is continuously reversing
direction, alternately flowing in one
direction and then in the other.
Alternating Voltage
can be similarly described.
The designation ac is normally applied to
both current and voltage.
5
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6. Chapter 11 – Alternating Current Circuits
Alternating Waveform
Vertical axis : current (I) or voltage (V)
Horizontal axis : time (t)
+V +I
t t
-V -I
6
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7. Chapter 11 – Alternating Current Circuits
Why not Direct Current (DC)?
Problems of using DC as +V
power distribution system:
suffers from rapid power loss
in the wires due to their t
resistance, which dissipates
energy as heat
DC power stations had -V
useful ranges of about two
kilometers
Once generated, DC power
cannot be modified
7
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8. Chapter 11 – Alternating Current Circuits
Power Distribution System
V=RI
1) 2) 3)
To prevent risk of To avoid serious For the safety of the
sparks and short heating effects, user, the voltage
circuits in the present at high needs to be low in the
generator itself, current, it needs to be home.
power needs to be transmitted at the
generated with low lowest current V low I is high
voltages. practical.
I low V is high DC is not suitable
V low I is high
8
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9. Chapter 11 – Alternating Current Circuits
Advantages of A.C.
--- readily available from generators
and power supply sockets in homes
and workshops.
--- can be stepped up or down by the
use of a transformer.
--- for transmission purpose.
9
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10. Chapter 11 – Alternating Current Circuits
Alternator
An alternator is a machine that converts
mechanical energy to electrical energy.
A simple alternator basically consists of
two parts:
a) coils or windings
b) magnetic poles
10
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11. Chapter 11 – Alternating Current Circuits
Generation of Alternating Current
An alternating quantity may be generated by
a) rotating a coil in a magnetic field
b) rotating a magnetic field within a stationary coil
Carbon Brushes
1, 2
Slip Rings
a, b
11
IT2001PA Engineering Essentials (1/2)
12. Chapter 11 – Alternating Current Circuits
Generation of Alternating Current
How does AC generate a sine waveform?
.
.
.
.
.
x x
x
x
x
12
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13. Chapter 11 – Alternating Current Circuits
Generation of Alternating Current
How does AC generate a sine waveform?
13
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14. Chapter 11 – Alternating Current Circuits
Generation of Alternating Current
How does AC generate a sine waveform?
x x
.
.
14
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15. Chapter 11 – Alternating Current Circuits
Generation of Alternating Current
AC generator consists of a magnet and a loop
of wire which rotates in the magnetic field of
the magnet.
As the wire rotates in the magnetic field, the
changing strength of the magnetic field
through the wire produces a force which drives
the electric charges around the wire.
The force initially generates an electric current
in one direction along the wire. Then as the
loop rotates through 180 degrees the force
reverses to give an electric current in the
opposite direction along the wire. Every time
the loop rotates through 180 degrees the
direction of the force and therefore the current
changes.
The changing direction of the force after every
180 degrees of rotation gives the alternating
current.
AC generator also has slip rings which make
sure that the ends of the wire are always
connected to the same side of the electric
circuit. This makes sure that the direction of the
current changes every half revolution of the
wire.
15
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16. Chapter 11 – Alternating Current Circuits
Generation of Alternating emf
The magnitude of the emf is given by,
e = Em sin θ
16
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17. Chapter 11 – Alternating Current Circuits
Sine Wave
A common type of ac.
Also referred as
sinusoidal waveform
sinusoid
Symbol for a sine wave voltage source :
OR
17
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18. Chapter 11 – Alternating Current Circuits
What is an Alternating Quantity?
An alternating quantity is one which acts in
alternate directions and whose magnitude
undergoes a definite cycle of changes in
definite interval of time.
18
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19. Chapter 11 – Alternating Current Circuits
Polarity
When the voltage changes polarity at its zero
crossing,the current correspondingly changes
direction.
+V Positive Alternation -
VS R
t +
-V I
+V
Negative Alternation +
I
VS R
t -
-V
19
IT2001PA Engineering Essentials (1/2)
20. Chapter 11 – Alternating Current Circuits
Amplitude
The maximum value of the sine wave.
+V
Positive Maximum (peak)
t
Negative Maximum (peak)
-V
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21. Chapter 11 – Alternating Current Circuits
What is Cycle of a Waveform?
One complete waveform is known as one cycle.
Each cycle consists of two half-cycles.
During 1st half-cycle, the quantity acts in one direction
and
during the second half-cycle, in the opposite direction.
Each cycle :
consists of 2 alternations.
consists of 2 peaks.
reaches maximum amplitude 2 times.
21
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22. Chapter 11 – Alternating Current Circuits
Cycle
A sine wave repeats itself in identical cycles.
+V
t
-V 1st cycle 2nd cycle 3rd cycle
22
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23. Chapter 11 – Alternating Current Circuits
Period
The time required for a given sine wave to
complete one full cycle.
symbol - T
unit - second (s)
Time taken is the same for each cycle;
thus fixed value for a given sine wave.
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24. Chapter 11 – Alternating Current Circuits
Period Measurement
From one zero crossing to the corresponding zero
crossing in the next cycle
positive zero crossing to positive zero crossing.
+V
t
-V period period period
24
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25. Chapter 11 – Alternating Current Circuits
Period Measurement
From one peak to the corresponding peak in the
next cycle
positive peak to positive peak.
+V
t
-V period period
25
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26. Chapter 11 – Alternating Current Circuits
Period Measurement
From any point to the corresponding point in the
next cycle.
+V
period
t
-V period
26
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27. Chapter 11 – Alternating Current Circuits
Example 11-1
What is the period of the sine wave?
V
0
t(s)
2 4 6
1 cycle takes 2s to complete.
Therefore the period is 2s.
27
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28. Chapter 11 – Alternating Current Circuits
Example 11-2
What is the period of the sine wave?
V
0
t(s)
12
5 cycles takes 12s to complete
1 cycle takes (12/5)s to complete time taken
1 cycle takes 2.4s to complete T =
no. of cycles
Therefore the period is 2.4s.
28
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29. Chapter 11 – Alternating Current Circuits
Frequency
The number of cycles a sine wave can
complete in 1 second.
symbol : f
unit - Hertz (Hz)
Examples :
160Hz - 160 complete cycles in 1s.
50Hz - 50 complete cycles in 1s.
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30. Chapter 11 – Alternating Current Circuits
Frequency vs Period
Reciprocal relationship :
1 1
f = T =
T f
More cycles in 1s Lesser cycles in 1s
- higher frequency. - lower frequency.
- shorter period. - longer period.
V T V T
0
t t
0
1s 1s
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31. Chapter 11 – Alternating Current Circuits
Example 11-3
Which sine wave has the higher frequency?
Determine the period and the frequency of
both waveforms.
V V
0
t 0
t
1s 1s
Waveform A Waveform B
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32. Chapter 11 – Alternating Current Circuits
Example 11-3
continue …
V V
0
t 0
t
1s 1s
Waveform A Waveform B
Waveform B complete more cycles in 1s.
Therefore Waveform B has the higher frequency.
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33. Chapter 11 – Alternating Current Circuits
Example 11-3
continue … 3 cycles in 1s
-- frequency is 3Hz
V
period (T) = 1/f = 1/3Hz
t = 0.333s
0 1s
Waveform A 3 cycles take 1s
OR
-- 1 cycles takes (1s/3) = 0.333s
-- period is 0.333s
frequency (f) = 1/T = 1/0.333s
= 3Hz
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34. Chapter 11 – Alternating Current Circuits
Example 11-3
continue … 5 cycles in 1s
-- frequency is 5Hz
V period (T) = 1/f = 1/5Hz
= 0.2s
t
0 1s OR
Waveform B 5 cycles take 1s
-- 1 cycles takes (1s/5) = 0.2s
-- period is 0.2s
frequency (f) = 1/T = 1/0.2s
= 5Hz
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35. Chapter 11 – Alternating Current Circuits
Example 11-4
The period of a sine wave is 10ms. What is
the frequency?
period (T) = 10ms
frequency (f) = 1/T
= 1/10ms
= 100Hz
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36. Chapter 11 – Alternating Current Circuits
Example 11-5
The frequency of a sine wave is 60Hz. What
is the period?
frequency (f) = 60Hz
period (T) = 1/f
= 1/60Hz
= 16.7ms
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37. Chapter 11 – Alternating Current Circuits
Voltage Sources
If an ac voltage is applied to a
circuit, an ac current flows.
The voltage and current will have
the same frequency.
+V +I
I
t t
-V -I
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38. Chapter 11 – Alternating Current Circuits
Sine Wave Angles
The horizontal axis can be replaced by
angular measurement (degrees).
+ V ½ cycle
one cycle
angle
0o
90 o 180 o 270 o 360 o
-V peak zero peak zero
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39. Chapter 11 – Alternating Current Circuits
Sine Wave Values
Ways to express and measure the value of a
sine wave :
1) instantaneous value.
2) peak value.
3) peak-to-peak value.
4) root-mean-square value.
5) average value.
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40. Chapter 11 – Alternating Current Circuits
Instantaneous Value
The voltage or current value of a
waveform at a given instant in time.
Symbol :
voltage - v
current - i
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41. Chapter 11 – Alternating Current Circuits
Instantaneous Value
Different at different points of time.
+V +I
8.5
5.5
5
t3 3 t3
t t
t1 t2 t1 t2
-6 -4.5
-V -I
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42. Chapter 11 – Alternating Current Circuits
Instantaneous Value
Different at different points of angle.
+V +I
Vp Ip
v i
degree degree
θ θ
-V v = Vmax sin θ -I i = Imax sin θ
v = Vmax sin 2πft i = Imax sin 2πft
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43. Chapter 11 – Alternating Current Circuits
Example 11-6
A current sine wave has a maximum value of
200A. How much is the current at the instant
of 30 degrees of the cycle?
i = Imax sin θ
i = 200 sin 30 o
= 200 x 0.5
= 100A
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44. Chapter 11 – Alternating Current Circuits
Peak Value
The voltage or current value of a waveform at
its maximum positive or negative points.
Symbol :
voltage - Vp or Vmax
current - Ip or Imax
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45. Chapter 11 – Alternating Current Circuits
Peak Value
The peaks are equal for a sine wave and is
characterized by a single peak value.
+V
Positive Maximum (peak)
t
Negative Maximum (peak)
-V
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46. Chapter 11 – Alternating Current Circuits
Peak-to-Peak Value
The voltage or current value of a waveform
measured from its minimum to its maximum
points.
Symbol :
voltage - Vpp
current - Ipp
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48. Chapter 11 – Alternating Current Circuits
Root Mean Square Value
Equal to the dc voltage that produces the same
amount of heat in a resistance as does the AC (sine
wave) voltage.
+ +
VS R Vdc R
- I radiated - I same
heat amount of
Vmax = 10 V radiated heat.
Vrms = 7.07V = Vdc
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49. Chapter 11 – Alternating Current Circuits
Root Mean Square Value
Also known as the effective value.
Symbol :
voltage - Vrms
current - Irms
The voltage and current values
given are usually as rms unless
otherwise stated.
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51. Chapter 11 – Alternating Current Circuits
Average Value
The average of a sine wave over half-
cycle.
The average value taken over a
complete cycle is always zero.
Symbol :
voltage - Vavg
current - Iavg
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52. Chapter 11 – Alternating Current Circuits
Average Value
+V
Vavg = 0.637 Vmax
Vavg 1
Vp
t 0.637 V = V
avg max
1
Vmax = 0.637 Vavg
-V
Vmax = 1.57 Vavg
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53. Chapter 11 – Alternating Current Circuits
Form & Peak Factor for Sine Wave
Form factor = Rms value
Avg value
0.707 X Max value
= 0.637 X Max value
= 1.11
Max value
Peak factor =
Rms value
Max value
= 0.707 X Max value
= 1.414
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