Synchronous machines include synchronous generators and motors. Synchronous generators are the primary source of electrical power and rely on synchronous motors for industrial drives. There are two main types - salient-pole and cylindrical rotor machines. Synchronous generator operation is based on synchronizing the electrical frequency to the mechanical speed of rotation. The parameters of synchronous machines can be determined from open-circuit, short-circuit, and DC tests. Synchronous generators must be synchronized before connecting in parallel by matching their voltages, phase sequences, and frequencies.
An induction motor is described with the following specifications:
- 480-V, 60 Hz, 50-hp, 3-phase
- Drawing 60A at 0.85 PF lagging
- Stator copper losses of 2 kW
- Rotor copper losses of 700 W
To determine the rotor frequency at full load, the slip is calculated using the given power rating, current, and power factor. The slip is then used to calculate the rotor frequency.
The document discusses the construction and operation of synchronous generators. It describes how a synchronous generator works by applying a DC current to the rotor to create a rotating magnetic field, which induces a 3-phase voltage in the stator windings. It also discusses the rotor, field windings, armature windings, brushless excitation systems, equivalent circuits, phasor diagrams, and the effects of load changes on generators operating alone or connected in parallel.
DC motors
Torque & Speed Equations
Torque -Armature current Characteristics
Speed - Armature current Characteristics
Torque-speed characteristics
Applications
Speed Control
The document describes different testing methods for DC machines. It discusses the simple/direct test method, Swinburne's indirect test method, and Hopkinson's regenerative test method. The simple/direct test method calculates efficiency by directly loading the DC machine, but it is only suitable for small machines. Swinburne's method measures no-load losses to determine efficiency indirectly. Hopkinson's method couples two identical DC machines together to test them simultaneously, with one acting as a motor and the other as a generator.
Line to Line & Double Line to Ground Fault On Power SystemSmit Shah
This document discusses line-to-line faults and double line-to-ground faults on power systems. For a line-to-line fault, the positive and negative sequence networks are connected in parallel through a fault impedance. This satisfies the fault conditions. For a double line-to-ground fault, the positive sequence network is in series with the parallel combination of the negative and zero sequence networks, connected through a fault impedance. Equations are derived relating the sequence currents and voltages for determining the fault current values. Sequence networks are used to model and calculate faults on power systems.
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.
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.
A synchronous motor is electrically identical with an alternator or AC generator.
A given alternator ( or synchronous machine) can be used as a motor, when driven electrically.
Some characteristic features of a synchronous motor are as follows:
1. It runs either at synchronous speed or not at all i.e. while running it maintains a constant speed. The only way to change its speed is to vary the supply frequency (because NS=120f/P).
2. It is not inherently self-starting. It has to be run up to synchronous (or near synchronous) speed by some means, before it can be synchronized to the supply.
3. It is capable of being operated under a wide range of power factors, both lagging and leading. Hence, it can be used for power correction purposes, in addition to supplying torque to drive loads.
An induction motor is described with the following specifications:
- 480-V, 60 Hz, 50-hp, 3-phase
- Drawing 60A at 0.85 PF lagging
- Stator copper losses of 2 kW
- Rotor copper losses of 700 W
To determine the rotor frequency at full load, the slip is calculated using the given power rating, current, and power factor. The slip is then used to calculate the rotor frequency.
The document discusses the construction and operation of synchronous generators. It describes how a synchronous generator works by applying a DC current to the rotor to create a rotating magnetic field, which induces a 3-phase voltage in the stator windings. It also discusses the rotor, field windings, armature windings, brushless excitation systems, equivalent circuits, phasor diagrams, and the effects of load changes on generators operating alone or connected in parallel.
DC motors
Torque & Speed Equations
Torque -Armature current Characteristics
Speed - Armature current Characteristics
Torque-speed characteristics
Applications
Speed Control
The document describes different testing methods for DC machines. It discusses the simple/direct test method, Swinburne's indirect test method, and Hopkinson's regenerative test method. The simple/direct test method calculates efficiency by directly loading the DC machine, but it is only suitable for small machines. Swinburne's method measures no-load losses to determine efficiency indirectly. Hopkinson's method couples two identical DC machines together to test them simultaneously, with one acting as a motor and the other as a generator.
Line to Line & Double Line to Ground Fault On Power SystemSmit Shah
This document discusses line-to-line faults and double line-to-ground faults on power systems. For a line-to-line fault, the positive and negative sequence networks are connected in parallel through a fault impedance. This satisfies the fault conditions. For a double line-to-ground fault, the positive sequence network is in series with the parallel combination of the negative and zero sequence networks, connected through a fault impedance. Equations are derived relating the sequence currents and voltages for determining the fault current values. Sequence networks are used to model and calculate faults on power systems.
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.
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.
A synchronous motor is electrically identical with an alternator or AC generator.
A given alternator ( or synchronous machine) can be used as a motor, when driven electrically.
Some characteristic features of a synchronous motor are as follows:
1. It runs either at synchronous speed or not at all i.e. while running it maintains a constant speed. The only way to change its speed is to vary the supply frequency (because NS=120f/P).
2. It is not inherently self-starting. It has to be run up to synchronous (or near synchronous) speed by some means, before it can be synchronized to the supply.
3. It is capable of being operated under a wide range of power factors, both lagging and leading. Hence, it can be used for power correction purposes, in addition to supplying torque to drive loads.
The document discusses a single phase semiconverter circuit used in power electronics. It contains a half bridge configuration with two SCRs and two diodes connected in a bridge. During the positive half cycle, SCR T1 and diode D2 conduct to deliver power to the load. During the negative half cycle, diode D3 and SCR T4 conduct. Waveforms and examples with resistive, inductive, and resistive-inductive-emissive loads are provided.
Per unit analysis is used to normalize variables in power systems to avoid difficulties in referring impedances across transformers. It involves choosing base values for voltage, power, impedance and current, then expressing all quantities as ratios of their actual to base values. This allows transformer impedances to be treated as single values regardless of which side they are referred to. It also keeps per unit quantities within a narrow range and clearly shows their relative values. The procedure is demonstrated through an example circuit solved first using single phase and then three phase per unit analysis with the same result.
The document discusses power system stability, including classifications of stability (steady state, transient, and dynamic) and factors that affect transient stability. It also covers topics like the swing equation, equal area criterion, critical clearing angle, and multi-machine stability studies. Some key points:
1) Power system stability refers to a system's ability to return to normal operating conditions after disturbances like faults or load changes.
2) Transient stability depends on factors like fault duration and location, generator inertia, and pre-fault loading conditions.
3) The equal area criterion states that a system will remain stable if the accelerating and decelerating area segments on the power-angle curve are equal.
4)
This document discusses speed control methods for DC motors. It begins by explaining that DC motors can achieve fine speed control through simple methods, which is their main advantage over AC motors. It then describes the three main speed control methods for DC motors as varying the flux, armature resistance, or applied voltage. Subsequent sections provide more details on speed control for shunt motors and series motors, including flux control, armature control, voltage control, and numerical examples. The document is intended to teach speed control of DC motors through lecture notes.
This document provides an overview of synchronous machines and synchronous condensers. It discusses key topics such as:
- The basic components and operating principles of synchronous machines and how they can function as motors or generators.
- Concepts like torque, power, energy and their relationships in synchronous machines.
- How synchronous machines synchronize to the frequency of the power system and their operating speed relationship.
- Power flow, internal and terminal voltages, and torque angle in synchronous machines.
- Losses that occur in synchronous machines and how efficiency is affected.
- The use of synchronous condensers to provide reactive power support through field excitation control while transferring little to no real power.
- Models for analyzing
VTU Notes for Testing and commissioning of Electrical Equipment Department of Electrical and Electronics Faculty Name: Mrs Veena Bhat Designation: Assistant Professor Subject: Testing and Commissioning of Electrical equipment Semester: VII
Introduction to reactive power control in electrical powerDr.Raja R
Introduction to reactive power control in electrical power
Reactive power in transmission line :
Reactive power control
Reactive power and its importance
Apparent Power
Reactive Power
Apparent Power
Reactive Power Formula
Static relays use electronic components like semiconductors instead of mechanical parts to detect faults and operate. They have components like rectifiers to convert AC to DC, level detectors to compare values to thresholds, and amplifiers and output devices to trigger trips. The document discusses the components, types, and applications of various static relays like overcurrent, directional, differential, distance and instantaneous relays used in power system protection.
Three phase inverter - 180 and 120 Degree Mode of ConductionMalarselvamV
The document describes the operation of a 3-phase inverter that generates 3-phase AC voltage from a DC source using switches in both 180 degree and 120 degree conduction modes. In the 180 degree mode, each switch is closed for 180 degrees before the next switch closes. In the 120 degree mode, each switch is closed for 120 degrees. Tables show the switch states and resulting phase and line voltages for each 60 degree period. While the output waveforms are not pure sine waves, they approximate the desired 3-phase voltages. The inverter circuit provides a simple example for understanding 3-phase inverter operation.
1. The document discusses power system stability, including classifications of power system states as steady state, dynamic state, and transient state.
2. It describes synchronous machine swing equation and power angle equation, which relate the mechanical power input to the electrical power output of a generator through the power/torque angle.
3. An example calculation is shown to find the steady state power limit of a power system with a generator connected to an infinite bus through a transmission line.
This document discusses DC-DC converters known as choppers. It describes two types - step-down choppers and step-up choppers. A step-down chopper uses a thyristor switch to reduce input voltage to a lower output voltage for a load. Waveforms of the output voltage and current are shown. Different classes of choppers - Classes A through E - are defined based on the triggering schemes of the thyristors used. An example calculation is given to determine thyristor conduction period based on input voltage, output voltage, and operating frequency.
The document discusses the Sumpner's test, which is used to test large power transformers without actual loading. It has the following key points:
1. The Sumpner's test connects two identical transformers back to back, with their primaries in parallel and secondaries in series opposition, allowing them to be tested at full load conditions while only supplying power for losses.
2. This configuration causes the induced voltages in the secondaries to oppose each other, resulting in no net current flow between them. An auxiliary transformer is used to induce current and measure copper losses.
3. The test accurately determines total losses as they would occur in actual use, allowing efficiency and regulation to be found without full loading.
This document describes cascaded transformers which can be used to generate high AC voltages for testing purposes. It discusses introducing multiple transformer stages connected in series to step up the voltage. Each additional stage doubles the output voltage. For example, a three stage cascade could provide an output of 3V if the individual stages produced voltages of V, 2V, and 3V. Cascaded transformers provide a compact and cost-effective way to achieve high test voltages compared to a single large transformer. They are used to test equipment up to 1600kV and for experiments with transmission lines.
The armature winding is the main current-carrying winding in which the electromotive force or counter-emf of rotation is induced.
The current in the armature winding is known as the armature current.
The location of the winding depends upon the type of machine.
The armature windings of dc motors are located on the rotor, since they must operate in union with the commutator.
In DC rotating machines other than brushless DC machines, it is usually rotating.
The document presents information on a PWM rectifier. It discusses that a PWM rectifier is an AC to DC power converter using controlled semiconductor switches. It has features like bi-directional power flow, nearly sinusoidal input current, unity power factor regulation, and low harmonic distortion. The document includes a circuit diagram of a PWM rectifier and mentions it can be a current or voltage type. Advantages are listed as reduced harmonics and controlled output voltage. Future applications are in traction and as an active filter. The future scope is reduced input harmonics and improved power factor for PWM rectifiers.
Power System Analysis was a core subject for Electrical & Electronics Engineering, Based On Anna University Syllabus. The Whole Subject was there in this document.
Share with it ur friends & Follow me for more updates.!
This 3-page document describes an experiment to separate the different losses in a DC shunt motor, including friction, windage, hysteresis, and eddy current losses. It provides an introduction to the theoretical background, outlines the experimental procedure and apparatus used, includes sample data collection in a table, shows calculations to determine the individual loss coefficients, and lists the conclusions. The goal is to measure the losses at different motor speeds and excitations in order to calculate the separate contributions of each loss type based on their speed and field current dependencies.
The load on a power station varies over time rather than being constant. This variability in load presents challenges for power stations, as they must produce power whenever demanded by consumers. Variable loads can necessitate additional equipment to vary the fuel supply and increase production costs, as generator efficiency decreases during light loads. Load curves are used to analyze and understand load patterns, showing how demand changes over various time periods from daily to annually. This information is important for power station operation and planning.
This document provides information about synchronous machines. It discusses:
- Synchronous generators are used to generate electrical power from steam, gas, or hydraulic turbines. They are the primary source of power generation.
- Synchronous machines can operate as generators or motors. Large synchronous motors are commonly used for constant speed industrial drives.
- The document describes the construction, types, operation, and testing of synchronous machines. It provides equations to calculate parameters like voltage, frequency, reactance, and regulation from test data.
- Parallel operation and synchronization of generators is discussed. Concepts like the infinite bus and power-angle characteristics are introduced.
The document discusses the principles of operation of synchronous machines, which can operate as either motors or generators. It describes their construction, including salient pole and cylindrical rotors. It also covers single phase and three phase alternators, explaining how their windings produce phase-displaced voltages. Additional topics covered include open and short circuit characteristics, load conditions, equivalent circuits, and power flow calculations.
The document discusses a single phase semiconverter circuit used in power electronics. It contains a half bridge configuration with two SCRs and two diodes connected in a bridge. During the positive half cycle, SCR T1 and diode D2 conduct to deliver power to the load. During the negative half cycle, diode D3 and SCR T4 conduct. Waveforms and examples with resistive, inductive, and resistive-inductive-emissive loads are provided.
Per unit analysis is used to normalize variables in power systems to avoid difficulties in referring impedances across transformers. It involves choosing base values for voltage, power, impedance and current, then expressing all quantities as ratios of their actual to base values. This allows transformer impedances to be treated as single values regardless of which side they are referred to. It also keeps per unit quantities within a narrow range and clearly shows their relative values. The procedure is demonstrated through an example circuit solved first using single phase and then three phase per unit analysis with the same result.
The document discusses power system stability, including classifications of stability (steady state, transient, and dynamic) and factors that affect transient stability. It also covers topics like the swing equation, equal area criterion, critical clearing angle, and multi-machine stability studies. Some key points:
1) Power system stability refers to a system's ability to return to normal operating conditions after disturbances like faults or load changes.
2) Transient stability depends on factors like fault duration and location, generator inertia, and pre-fault loading conditions.
3) The equal area criterion states that a system will remain stable if the accelerating and decelerating area segments on the power-angle curve are equal.
4)
This document discusses speed control methods for DC motors. It begins by explaining that DC motors can achieve fine speed control through simple methods, which is their main advantage over AC motors. It then describes the three main speed control methods for DC motors as varying the flux, armature resistance, or applied voltage. Subsequent sections provide more details on speed control for shunt motors and series motors, including flux control, armature control, voltage control, and numerical examples. The document is intended to teach speed control of DC motors through lecture notes.
This document provides an overview of synchronous machines and synchronous condensers. It discusses key topics such as:
- The basic components and operating principles of synchronous machines and how they can function as motors or generators.
- Concepts like torque, power, energy and their relationships in synchronous machines.
- How synchronous machines synchronize to the frequency of the power system and their operating speed relationship.
- Power flow, internal and terminal voltages, and torque angle in synchronous machines.
- Losses that occur in synchronous machines and how efficiency is affected.
- The use of synchronous condensers to provide reactive power support through field excitation control while transferring little to no real power.
- Models for analyzing
VTU Notes for Testing and commissioning of Electrical Equipment Department of Electrical and Electronics Faculty Name: Mrs Veena Bhat Designation: Assistant Professor Subject: Testing and Commissioning of Electrical equipment Semester: VII
Introduction to reactive power control in electrical powerDr.Raja R
Introduction to reactive power control in electrical power
Reactive power in transmission line :
Reactive power control
Reactive power and its importance
Apparent Power
Reactive Power
Apparent Power
Reactive Power Formula
Static relays use electronic components like semiconductors instead of mechanical parts to detect faults and operate. They have components like rectifiers to convert AC to DC, level detectors to compare values to thresholds, and amplifiers and output devices to trigger trips. The document discusses the components, types, and applications of various static relays like overcurrent, directional, differential, distance and instantaneous relays used in power system protection.
Three phase inverter - 180 and 120 Degree Mode of ConductionMalarselvamV
The document describes the operation of a 3-phase inverter that generates 3-phase AC voltage from a DC source using switches in both 180 degree and 120 degree conduction modes. In the 180 degree mode, each switch is closed for 180 degrees before the next switch closes. In the 120 degree mode, each switch is closed for 120 degrees. Tables show the switch states and resulting phase and line voltages for each 60 degree period. While the output waveforms are not pure sine waves, they approximate the desired 3-phase voltages. The inverter circuit provides a simple example for understanding 3-phase inverter operation.
1. The document discusses power system stability, including classifications of power system states as steady state, dynamic state, and transient state.
2. It describes synchronous machine swing equation and power angle equation, which relate the mechanical power input to the electrical power output of a generator through the power/torque angle.
3. An example calculation is shown to find the steady state power limit of a power system with a generator connected to an infinite bus through a transmission line.
This document discusses DC-DC converters known as choppers. It describes two types - step-down choppers and step-up choppers. A step-down chopper uses a thyristor switch to reduce input voltage to a lower output voltage for a load. Waveforms of the output voltage and current are shown. Different classes of choppers - Classes A through E - are defined based on the triggering schemes of the thyristors used. An example calculation is given to determine thyristor conduction period based on input voltage, output voltage, and operating frequency.
The document discusses the Sumpner's test, which is used to test large power transformers without actual loading. It has the following key points:
1. The Sumpner's test connects two identical transformers back to back, with their primaries in parallel and secondaries in series opposition, allowing them to be tested at full load conditions while only supplying power for losses.
2. This configuration causes the induced voltages in the secondaries to oppose each other, resulting in no net current flow between them. An auxiliary transformer is used to induce current and measure copper losses.
3. The test accurately determines total losses as they would occur in actual use, allowing efficiency and regulation to be found without full loading.
This document describes cascaded transformers which can be used to generate high AC voltages for testing purposes. It discusses introducing multiple transformer stages connected in series to step up the voltage. Each additional stage doubles the output voltage. For example, a three stage cascade could provide an output of 3V if the individual stages produced voltages of V, 2V, and 3V. Cascaded transformers provide a compact and cost-effective way to achieve high test voltages compared to a single large transformer. They are used to test equipment up to 1600kV and for experiments with transmission lines.
The armature winding is the main current-carrying winding in which the electromotive force or counter-emf of rotation is induced.
The current in the armature winding is known as the armature current.
The location of the winding depends upon the type of machine.
The armature windings of dc motors are located on the rotor, since they must operate in union with the commutator.
In DC rotating machines other than brushless DC machines, it is usually rotating.
The document presents information on a PWM rectifier. It discusses that a PWM rectifier is an AC to DC power converter using controlled semiconductor switches. It has features like bi-directional power flow, nearly sinusoidal input current, unity power factor regulation, and low harmonic distortion. The document includes a circuit diagram of a PWM rectifier and mentions it can be a current or voltage type. Advantages are listed as reduced harmonics and controlled output voltage. Future applications are in traction and as an active filter. The future scope is reduced input harmonics and improved power factor for PWM rectifiers.
Power System Analysis was a core subject for Electrical & Electronics Engineering, Based On Anna University Syllabus. The Whole Subject was there in this document.
Share with it ur friends & Follow me for more updates.!
This 3-page document describes an experiment to separate the different losses in a DC shunt motor, including friction, windage, hysteresis, and eddy current losses. It provides an introduction to the theoretical background, outlines the experimental procedure and apparatus used, includes sample data collection in a table, shows calculations to determine the individual loss coefficients, and lists the conclusions. The goal is to measure the losses at different motor speeds and excitations in order to calculate the separate contributions of each loss type based on their speed and field current dependencies.
The load on a power station varies over time rather than being constant. This variability in load presents challenges for power stations, as they must produce power whenever demanded by consumers. Variable loads can necessitate additional equipment to vary the fuel supply and increase production costs, as generator efficiency decreases during light loads. Load curves are used to analyze and understand load patterns, showing how demand changes over various time periods from daily to annually. This information is important for power station operation and planning.
This document provides information about synchronous machines. It discusses:
- Synchronous generators are used to generate electrical power from steam, gas, or hydraulic turbines. They are the primary source of power generation.
- Synchronous machines can operate as generators or motors. Large synchronous motors are commonly used for constant speed industrial drives.
- The document describes the construction, types, operation, and testing of synchronous machines. It provides equations to calculate parameters like voltage, frequency, reactance, and regulation from test data.
- Parallel operation and synchronization of generators is discussed. Concepts like the infinite bus and power-angle characteristics are introduced.
The document discusses the principles of operation of synchronous machines, which can operate as either motors or generators. It describes their construction, including salient pole and cylindrical rotors. It also covers single phase and three phase alternators, explaining how their windings produce phase-displaced voltages. Additional topics covered include open and short circuit characteristics, load conditions, equivalent circuits, and power flow calculations.
DC machines operate on the principles of electromagnetic induction and force. They have commutators, field windings, and armature windings. DC machines can operate as motors or generators depending on the direction of power flow. Speed in DC motors can be controlled through methods like armature voltage control, field control, and armature resistance control. DC generators have open-circuit, load, and external characteristics that define their performance based on variables like terminal voltage, field current, and load current. Efficiency is impacted by losses such as copper losses and mechanical losses.
1) A synchronous generator produces AC voltage through induction in its stator windings caused by a rotating magnetic field generated by its rotor. The rotor contains field windings energized by DC current to produce the magnetic field.
2) The internal generated voltage of the generator depends on its rotational speed and magnetic flux. However, armature reaction and impedance effects cause the terminal voltage to differ from the internal voltage under load conditions.
3) Equivalent circuits are used to model synchronous generators, representing the internal generated voltage and impedance effects. Phasor diagrams illustrate the relationship between voltages and currents under different load power factors.
1. A synchronous generator produces power by inducing a 3-phase voltage in its stator windings via a rotating magnetic field created by its rotor.
2. The rotor contains field windings that are supplied with DC current to produce the magnetic field.
3. When load is applied, armature reaction causes the induced voltage to differ from the output voltage based on the load power factor.
Chapter 7 Application of Electronic Converters.pdfLiewChiaPing
This document discusses power electronics applications in DC and AC drives. It describes the basic characteristics and equivalent circuits of DC motors and how their speed can be controlled through various single-phase and three-phase converter configurations. It also summarizes the operation of induction motors, including cage and slip-ring types, and how their speed can be controlled through variable frequency inverters or by adjusting the slip-ring voltage. The document concludes by outlining the main components of HVDC converter stations used for long distance and asynchronous power transmission.
Electrical Power Systems Synchronous GeneratorMubarek Kurt
Here are the steps to solve this problem:
a) Given: Generator is 6 pole, 50 Hz
Using the synchronous speed formula: nm = 120f/P
nm = 120*50/6 = 1000 RPM
b) Terminal voltage at different power factors:
1) Given load: Ia = 60 A, PF = 0.8 lagging
Using phasor diagram: Vt = Ea - IaXs
Ea = Vt + IaXs = 480 + 60*1 = 540 V
Vt = 540*cos(cos-1(0.8)) = 480 V
2) PF = 1.0
Vt = Ea = 540 V
3) PF
This document provides information about direct current (DC) motors, including:
- The three main types of DC motors: shunt wound, series wound, and separately excited.
- How to calculate torque-speed characteristics for each type.
- The construction, principle of operation, induced electromotive force (emf), torque, and terminal voltage of DC motors.
- How shunt wound, series wound, and separately excited motors differ in their field and armature windings connections.
- Formulas for calculating speed, torque, induced emf, and armature current as a function of motor parameters like resistance, flux, and supply voltage.
This document describes the principles of operation of a 3-phase alternator. It discusses how a synchronous generator works using Faraday's law of electromagnetic induction. It also describes the different components of a 3-phase alternator including the stator, rotor, and different winding configurations. The document also discusses how varying the field current can control the output voltage of the alternator and how the number of poles and rotor speed determine the output frequency. Open and short circuit testing characteristics are also summarized.
This document provides information about direct current (DC) motors, including:
- The three main types of DC motors: shunt wound, series wound, and separately excited.
- How to calculate torque-speed characteristics for each type.
- The construction, principle of operation, induced electromotive force (emf), torque, terminal voltage, and methods of connection for DC motors.
- How to analyze performance and calculate characteristics like torque, speed, current, and voltage for DC motors.
This document provides information about direct current (DC) motors, including:
- The three main types of DC motors: shunt wound, series wound, and separately excited and their characteristics.
- The principles of operation, construction, and torque-speed characteristics of DC motors.
- How to calculate torque, speed, induced emf, and other parameters for DC motors.
- Applications of the different DC motor types.
- Circuit diagrams and equations for analyzing DC motor performance.
This document provides information about direct current (DC) motors, including:
- The three main types of DC motors: shunt wound, series wound, and separately excited and their characteristics.
- The principles of operation, construction, and torque-speed characteristics of DC motors.
- How to calculate torque, speed, induced emf, and other parameters for DC motors.
- Applications of the different DC motor types.
- Circuit diagrams and equations for analyzing DC motor performance.
This document provides information about direct current (DC) motors, including:
- The three main types of DC motors: shunt wound, series wound, and separately excited and their characteristics.
- The principles of operation, construction, and torque-speed characteristics of DC motors.
- How to calculate torque, speed, induced emf, and other parameters for DC motors.
- Applications of the different DC motor types.
- Circuit diagrams and equations for analyzing DC motor performance.
This document provides information about direct current (DC) motors, including:
- The three main types of DC motors: shunt wound, series wound, and separately excited.
- How to calculate torque-speed characteristics for each type.
- The construction, principle of operation, induced electromotive force (emf), torque, terminal voltage, and methods of connection for DC motors.
- How to analyze performance and calculate characteristics like torque, speed, current, and voltage for DC motors.
This document provides information about direct current (DC) motors, including:
- The three main types of DC motors: shunt wound, series wound, and separately excited and their characteristics.
- The principles of operation, construction, and torque-speed characteristics of DC motors.
- How to calculate torque, speed, induced emf, and other parameters for DC motors.
- Applications of the different DC motor types.
- Circuit diagrams and equations for analyzing DC motor performance.
This document provides an instructional module on AC Machinery that covers alternators, synchronous motors, induction motors, and single-phase motors. It begins with an introduction and preface, then provides a table of contents outlining the key topics covered in each of the 4 chapters. The chapters cover the theory, principles of operation, engineering aspects, and applications of each type of AC motor. The objective is to impart the theories and principles of alternating current and electrical machines to students.
Online train ticket booking system project.pdfKamal Acharya
Rail transport is one of the important modes of transport in India. Now a days we
see that there are railways that are present for the long as well as short distance
travelling which makes the life of the people easier. When compared to other
means of transport, a railway is the cheapest means of transport. The maintenance
of the railway database also plays a major role in the smooth running of this
system. The Online Train Ticket Management System will help in reserving the
tickets of the railways to travel from a particular source to the destination.
Sri Guru Hargobind Ji - Bandi Chor Guru.pdfBalvir Singh
Sri Guru Hargobind Ji (19 June 1595 - 3 March 1644) is revered as the Sixth Nanak.
• On 25 May 1606 Guru Arjan nominated his son Sri Hargobind Ji as his successor. Shortly
afterwards, Guru Arjan was arrested, tortured and killed by order of the Mogul Emperor
Jahangir.
• Guru Hargobind's succession ceremony took place on 24 June 1606. He was barely
eleven years old when he became 6th Guru.
• As ordered by Guru Arjan Dev Ji, he put on two swords, one indicated his spiritual
authority (PIRI) and the other, his temporal authority (MIRI). He thus for the first time
initiated military tradition in the Sikh faith to resist religious persecution, protect
people’s freedom and independence to practice religion by choice. He transformed
Sikhs to be Saints and Soldier.
• He had a long tenure as Guru, lasting 37 years, 9 months and 3 days
This is an overview of my current metallic design and engineering knowledge base built up over my professional career and two MSc degrees : - MSc in Advanced Manufacturing Technology University of Portsmouth graduated 1st May 1998, and MSc in Aircraft Engineering Cranfield University graduated 8th June 2007.
2. Synchronous Machines
• Synchronous generators or alternators are used to convert
mechanical power derived from steam, gas, or hydraulic-turbine
to ac electric power
• Synchronous generators are the primary source of electrical
energy we consume today
• Large ac power networks rely almost exclusively on synchronous
generators
• Synchronous motors are built in large units compare to induction
motors (Induction motors are cheaper for smaller ratings) and
used for constant speed industrial drives
3. Construction
Basic parts of a synchronous generator:
• Rotor - dc excited winding
• Stator - 3-phase winding in which the ac emf is generated
The manner in which the active parts of a synchronous
machine are cooled determines its overall physical size and
structure
5. 1. Most hydraulic turbines have to turn at low speeds
(between 50 and 300 r/min)
2. A large number of poles are required on the rotor
Hydrogenerator
Turbine
Hydro (water)
D 10 m
Non-uniform
air-gap
N
S S
N
d-axis
q-axis
Salient-Pole Synchronous Generator
7. L 10 m
D 1 mTurbine
Steam
Stator
Uniform air-gap
Stator winding
Rotor
Rotor winding
N
S
High speed
3600 r/min 2-pole
1800 r/min 4-pole
Direct-conductor cooling (using
hydrogen or water as coolant)
Rating up to 2000 MVA
Turbogenerator
d-axis
q-axis
Cylindrical-Rotor Synchronous Generator
9. Operation Principle
The rotor of the generator is driven by a prime-mover
A dc current is flowing in the rotor winding which
produces a rotating magnetic field within the machine
The rotating magnetic field induces a three-phase
voltage in the stator winding of the generator
10. Electrical Frequency
Electrical frequency produced is locked or synchronized to
the mechanical speed of rotation of a synchronous
generator:
where fe = electrical frequency in Hz
P = number of poles
nm= mechanical speed of the rotor, in r/min
120
m
e
nP
f
11. Generated Voltage
The generated voltage of a synchronous generator is given by
where f = flux in the machine (function of If)
fe = electrical frequency
Kc= synchronous machine constant
Saturation characteristic of a synchronous generator.
ec fKE f
If
E
12. Voltage Regulation
A convenient way to compare the voltage behaviour of two
generators is by their voltage regulation (VR). The VR of a
synchronous generator at a given load, power factor, and at rated
speed is defined as
%
V
VE
VR
fl
flnl
100
Where Vfl is the full-load terminal voltage, and Enl (equal to Ef)
is the no-load terminal voltage (internal voltage) at rated speed
when the load is removed without changing the field current.
For lagging power factor (PF), VR is fairly positive, for unity
PF, VR is small positive and for leading PF, VR is negative.
13. Equivalent Circuit_1
o The internal voltage Ef produced in a machine is not usually the
voltage that appears at the terminals of the generator.
o The only time Ef is same as the output voltage of a phase is
when there is no armature current flowing in the machine.
o There are a number of factors that cause the difference between
Ef and Vt:
– The distortion of the air-gap magnetic field by the current flowing
in the stator, called the armature reaction
– The self-inductance of the armature coils.
– The resistance of the armature coils.
– The effect of salient-pole rotor shapes.
15. Phasor Diagram
Phasor diagram of a cylindrical-rotor synchronous generator,
for the case of lagging power factor
Lagging PF: |Vt|<|Ef| for overexcited condition
Leading PF: |Vt|>|Ef| for underexcited condition
16. Three-phase equivalent circuit of a cylindrical-rotor
synchronous machine
The voltages and currents of the three phases are 120o apart in angle,
but otherwise the three phases are identical.
+
Ia1
Ef1 jXs Ra+
VL-L
VL-L =3Vt
Vt
17. Determination of the parameters of the equivalent
circuit from test data
• The equivalent circuit of a synchronous generator that has been
derived contains three quantities that must be determined in order
to completely describe the behaviour of a real synchronous
generator:
– The saturation characteristic: relationship between If and f (and
therefore between If and Ef)
– The synchronous reactance, Xs
– The armature resistance, Ra
•
• The above three quantities could be determined by performing the
following three tests:
– Open-circuit test
– Short-circuit test
– DC test
18. Open-circuit test
• The generator is turned at the rated speed
• The terminals are disconnected from all loads, and the field current
is set to zero.
• Then the field current is gradually increased in steps, and the
terminal voltage is measured at each step along the way.
• It is thus possible to obtain an open-circuit characteristic of a
generator (Ef or Vt versus If) from this information
+
Vdc
If
Vt
19. Short-circuit test
• Adjust the field current to zero and short-circuit the terminals of
the generator through a set of ammeters.
• Record the armature current Isc as the field current is increased.
• Such a plot is called short-circuit characteristic.
A
A+
Vdc
If
Isc
20. – then
– If the stator is Y-connected, the per phase stator resistance is
– If the stator is delta-connected, the per phase stator resistance is
DC Test
– The purpose of the DC test is to determine Ra. A variable DC voltage
source is connected between two stator terminals.
– The DC source is adjusted to provide approximately rated stator current,
and the resistance between the two stator leads is determined from the
voltmeter and ammeter readings
DC
DC
DC
V
R
I
2
DC
a
R
R
DCa RR
2
3
21. Determination of Xs
• For a particular field current IfA, the internal voltage Ef (=VA) could
be found from the occ and the short-circuit current flow Isc,A could
be found from the scc.
• Then the synchronous reactance Xs could be obtained using
IfA
Ef or Vt (V) Air-gap line
OCC Isc (A)
SCC
If (A)
Vrated
VA
Isc,B
Isc, A
IfB
scA
fA
unsat,saunsat,s
I
EV
XRZ
22
22
aunsat,sunsat,s RZX
scA
oc,t
scA
f
unsat,s
I
V
I
E
X
: Ra is known from the DC test.
Since Xs,unsat>>Ra,
22. Xs under saturated condition
Ia
Ef Vt=0
jXs Ra
+
+
EfVt=0
jIaXs
IaRa
Ia
scB
frated
sat,sasat,s
I
EV
XRZ
22
At V = Vrated,
22
asat,ssat,s RZX : Ra is known from the DC test.
Equivalent circuit and phasor diagram under condition
IfA
Ef or Vt (V) Air-gap line
OCC Isc (A)
SCC
If (A)
Vrated
VA
Isc,B
Isc, A
IfB
23. Short-circuit Ratio
Another parameter used to describe synchronous generators is the
short-circuit ratio (SCR). The SCR of a generator defined as the
ratio of the field current required for the rated voltage at open
circuit to the field current required for the rated armature current
at short circuit. SCR is just the reciprocal of the per unit value of
the saturated synchronous reactance calculated by
.u.pinX
I
I
SCR
sat_s
Iscrated_f
Vrated_f
1
Ef or Vt (V) Air-gap line
OCC
Isc (A)
SCC
If (A)
Vrated
Isc,rated
If_V rated If_Isc rated
24. Example 1
A 200 kVA, 480-V, 60-Hz, 4-pole, Y-Connected synchronous
generator with a rated field current of 5 A was tested and the
following data was taken.
a) from OC test – terminal voltage = 540 V at rated field
current
b) from SC test – line current = 300A at rated field current
c) from Dc test – DC voltage of 10 V applied to two terminals,
a current of 25 A was measured.
1. Calculate the speed of rotation in r/min
2. Calculate the generated emf and saturated equivalent circuit
parameters (armature resistance and synchronous reactance)
25. Solution to Example 1
1.
fe = electrical frequency = Pnm/120
fe = 60Hz
P = number of poles = 4
nm = mechanical speed of rotation in r/min.
So, speed of rotation nm = 120 fe / P
= (120 x 60)/4 = 1800 r/min
2. In open-circuit test, Ia = 0 and Ef =Vt
Ef = 540/1.732
= 311.8 V (as the machine is Y-connected)
In short-circuit test, terminals are shorted, Vt = 0
Ef = IaZs or Zs = Ef /Ia =311.8/300=1.04 ohm
From the DC test, Ra=VDC/(2IDC)
= 10/(2X25) = 0.2 ohm
Synchronous reactance 2
,
2
, satsasats XRZ
02.12.004.1 2222
,, asatssats RZX
Ia
Ef
Vt
j1.02 0.2
+
+
26. Problem 1
A 480-V, 60-Hz, Y-Connected synchronous generator, having the
synchronous reactance of 1.04 ohm and negligible armature
resistance, is operating alone. The terminal voltage at rated field
current at open circuit condition is 480V.
1. Calculate the voltage regulation
1. If load current is 100A at 0.8 PF lagging
2. If load current is 100A at 0.8 PF leading
3. If load current is 100A at unity PF
2. Calculate the real and reactive power delivered in each case.
3. State and explain whether the voltage regulation will
improve or not if the load current is decreased to 50 A from
100 A at 0.8 PF lagging.
27. Parallel operation of synchronous generators
There are several major advantages to operate generators in
parallel:
• Several generators can supply a bigger load than one machine
by itself.
• Having many generators increases the reliability of the power
system.
• It allows one or more generators to be removed for shutdown
or preventive maintenance.
28. Before connecting a generator in parallel with another
generator, it must be synchronized. A generator is said to be
synchronized when it meets all the following conditions:
• The rms line voltages of the two generators must be
equal.
• The two generators must have the same phase sequence.
• The phase angles of the two a phases must be equal.
• The oncoming generator frequency is equal to the
running system frequency.
Synchronization
Load
Generator 2
Generator 1
Switch
a
b
c
a/
b/
c/
30. Concept of the infinite bus
When a synchronous generator is connected to a power system,
the power system is often so large that nothing the operator of the
generator does will have much of an effect on the power system.
An example of this situation is the connection of a single
generator to the Canadian power grid. Our Canadian power grid
is so large that no reasonable action on the part of one generator
can cause an observable change in overall grid frequency. This
idea is idealized in the concept of an infinite bus. An infinite bus
is a power system so large that its voltage and frequency do not
vary regardless of how much real or reactive power is drawn
from or supplied to it.
31. Active and reactive power-angle characteristics
• P>0: generator operation
• P<0: motor operation
• Positive Q: delivering inductive vars for a generator action or
receiving inductive vars for a motor action
• Negaive Q: delivering capacitive vars for a generator action or
receiving capacitive vars for a motor action
Pm
Pe, Qe
Vt
Fig. Synchronous generator connected to an infinite bus.
32. Active and reactive power-angle characteristics
• The real and reactive power delivered by a synchronous
generator or consumed by a synchronous motor can be
expressed in terms of the terminal voltage Vt, generated voltage
Ef, synchronous impedance Zs, and the power angle or torque
angle d.
• Referring to Fig. 8, it is convenient to adopt a convention that
makes positive real power P and positive reactive power Q
delivered by an overexcited generator.
• The generator action corresponds to positive value of d, while
the motor action corresponds to negative value of d.
Pm
Pe, Qe
Vt
33. The complex power output of the generator in volt-
amperes per phase is given by
*
at
_
IVjQPS
where:
Vt = terminal voltage per phase
Ia
* = complex conjugate of the armature current per phase
Taking the terminal voltage as reference
0jVV tt
_
the excitation or the generated voltage,
dd sinjcosEE ff
_
Active and reactive power-angle characteristics
Pm
Pe, Qe
Vt
34. Active and reactive power-angle characteristics
Pm
Pe, Qe
Vt
and the armature current,
s
ftf
s
t
_
f
_
a
_
jX
sinjEVcosE
jX
VE
I
dd
where Xs is the synchronous reactance per phase.
s
tft
s
ft
s
tft
s
ft
s
ftf
t
*
a
_
t
_
X
VcosEV
Q
&
X
sinEV
P
X
VcosEV
j
X
sinEV
jX
sinjEVcosE
VIVjQPS
2
2
d
d
d
d
dd
35. Active and reactive power-angle characteristics
Pm
Pe, Qe
Vt
s
tft
s
ft
X
VcosEV
Q&
X
sinEV
P
2
d
d
• The above two equations for active and reactive powers hold
good for cylindrical-rotor synchronous machines for negligible
resistance
• To obtain the total power for a three-phase generator, the above
equations should be multiplied by 3 when the voltages are line-to-
neutral
• If the line-to-line magnitudes are used for the voltages, however,
these equations give the total three-phase power
36. Steady-state power-angle or torque-angle characteristic of a
cylindrical-rotor synchronous machine (with negligible
armature resistance).
d
Real power or torque
generator
motor
pp/2
p/2
0
p
Pull-out torque
as a generator
Pull-out torque
as a motor
d
37. Steady-state stability limit
Total three-phase power: d sin
X
EV
P
s
ft3
The above equation shows that the power produced by a synchronous
generator depends on the angle d between the Vt and Ef. The maximum
power that the generator can supply occurs when d=90o.
s
ft
X
EV
P
3
The maximum power indicated by this equation is called steady-state stability
limit of the generator. If we try to exceed this limit (such as by admitting
more steam to the turbine), the rotor will accelerate and lose synchronism
with the infinite bus. In practice, this condition is never reached because the
circuit breakers trip as soon as synchronism is lost. We have to resynchronize
the generator before it can again pick up the load. Normally, real generators
never even come close to the limit. Full-load torque angle of 15o to 20o are
more typical of real machines.
38. Pull-out torque
The maximum torque or pull-out torque per phase that a two-pole
round-rotor synchronous motor can develop is
p
60
2 s
max
m
max
max
n
PP
T
where ns is the synchronous speed of the motor in rpm
P
d
P or Q
Q
Fig. Active and reactive power as a function of the internal angle
39. Problem 2
A 208-V, 45-kVA, 0.8-PF leading, -connected, 60-Hz
synchronous machine having 1.04 ohm synchronous
reactance and negligible armature resistance is supplying a
load of 12 kW at 0.8 power factor leading. Find the armature
current and generated voltage and power factor if the load is
increased to 20 KW. Neglect all other losses.
40. Example 5-2 (pp291)
A 480 V, 60 Hz, -connected, four pole synchronous generator has the OCC
shown below. This generator has a synchronous reactance of 0.1 ohm and
armature resistance of 0.015 ohm. At full load, the machine supplies 1200 A
and 0.8 pf lagging. Under full-load conditions, the friction and windage
losses are 40 kW, and the core losses are 30 kW. Ignore field circuit losses.
a) What is the speed of rotation of the generator?
b) How much field current must be supplied to the generator to make the
terminal voltage 480 V at no load?
c) If the generator is now connected to a load and the load draws 1200 A at 0.8
pf lagging, how much field current will be required to keep the terminal
voltage equal to 480 V?
d) How much power is the generator now supplying? How much power is
supplied to the generator by the prime-mover?
What is the machine’s overall efficiency?
e) If the generator’s load were suddenly disconnected
from the line, what would happen to its terminal voltage?
0
100
200
300
400
500
600
0 2 4 6 8 10
41. Synchronous Motors
• A synchronous motor is the same physical machine as a
generator, except that the direction of real power flow is
reversed
• Synchronous motors are used to convert electric power to
mechanical power
• Most synchronous motors are rated between 150 kW (200
hp) and 15 MW (20,000 hp) and turn at speed ranging from
150 to 1800 r/min. Consequently, these machines are used in
heavy industry
• At the other end of the power spectrum, we find tiny single-
phase synchronous motors used in control devices and
electric clocks
P, Q
Vt
Motor
42. Operation Principle
• The field current of a synchronous motor produces a steady-
state magnetic field BR
• A three-phase set of voltages is applied to the stator windings of
the motor, which produces a three-phase current flow in the
windings. This three-phase set of currents in the armature
winding produces a uniform rotating magnetic field of Bs
• Therefore, there are two magnetic fields present in the machine,
and the rotor field will tend to line up with the stator field, just
as two bar magnets will tend to line up if placed near each other.
• Since the stator magnetic field is rotating, the rotor magnetic
field (and the rotor itself) will try to catch up
• The larger the angle between the two magnetic fields (up to
certain maximum), the greater the torque on the rotor of the
machine
43. Vector Diagram
• The equivalent circuit of a synchronous motor is exactly same as
the equivalent circuit of a synchronous generator, except that the
reference direction of Ia is reversed.
• The basic difference between motor and generator operation in
synchronous machines can be seen either in the magnetic field
diagram or in the phasor diagram.
• In a generator, Ef lies ahead of Vt, and BR lies ahead of Bnet. In a
motor, Ef lies behind Vt, and BR lies behind Bnet.
• In a motor the induced torque is in the direction of motion, and in a
generator the induced torque is a countertorque opposing the
direction of motion
44. Vector Diagram
d
Ia
Vt
Ef
jIa Xs
d
Ia
Vt
Ef
jIa Xs
d
Bs
Bnet
BR
sync
Fig. The phasor diagram (leading PF: overexcited and |Vt|<|Ef|) and
the corresponding magnetic field diagram of a synchronous motor.
Fig. The phasor diagram of an underexcited synchronous
motor (lagging PF and |Vt|>|Ef|).
45. Application of Synchronous Motors
Synchronous motors are usually used in large sizes because in small sizes
they are costlier as compared with induction machines. The principal
advantages of using synchronous machine are as follows:
– Power factor of synchronous machine can be controlled very easily
by controlling the field current.
– It has very high operating efficiency and constant speed.
– For operating speed less than about 500 rpm and for high-power
requirements (above 600KW) synchronous motor is cheaper than
induction motor.
In view of these advantages, synchronous motors are preferred for driving
the loads requiring high power at low speed; e.g; reciprocating pumps and
compressor, crushers, rolling mills, pulp grinders etc.
46. Problem 5-22 (pp.343)
A 100-MVA, 12.5-kV, 0.85 power lagging, 50 Hz, two-
pole, Y-connected, synchronous generator has a pu
synchronous reactance of 1.1 and pu armature resistance
of 0.012.
a) What are its synchronous reactance and armature
resistance in ohms?
b) What is the magnitude of the internal voltage Ef at the
rated conditions? What is its load angle d at these
conditions?
c) Ignoring losses in the generator, what torque must be
applied to its shaft by the prime-mover at full load?
47. Problem 5-23 (pp.343)
A three-phase, Y-connected synchronous generator is
rated 120 MVA, 13.2 kV, 0.8 power lagging, and 60 Hz.
Its synchronous reactance is 0.9 ohm and its armature
resistance may be ignored.
a) What is its voltage regulation at rated load?
b) What would the voltage and apparent power rating of this
generator be if it were operated at 50 Hz with the same
armature and field losses as it had at 60 Hz?
c) What would the voltage regulation of the generator be at
50 Hz?