The document discusses synchronous generators and provides details about:
1. The types of synchronous generators based on the arrangement of field and armature windings.
2. The construction and components of a synchronous generator including the stationary armature and rotating field.
3. The different tests conducted on synchronous generators like open circuit, short circuit, and zero power factor tests to determine parameters like synchronous reactance.
4. Methods to calculate the voltage regulation of a synchronous generator like the EMF method, MMF method, and zero power factor method.
Starting method for 3 phase induction motorAhmed A.Hassan
The document discusses four common methods for starting 3-phase induction motors: rotor resistance starting for slip-ring motors, and direct-on-line starting, star-delta starting, and autotransformer starting for squirrel-cage motors. Rotor resistance starting allows adjusting the starting torque and current by adding external resistance to the rotor circuit. Direct-on-line starting applies full supply voltage but results in high starting current and moderate starting torque. Star-delta starting and autotransformer starting both initially apply reduced voltage to lower starting current and torque before switching to full voltage.
The document discusses the double cage induction motor. It has two rotor windings or cages that provide high starting torque at low starting current. The rotor has an outer winding made of manganese bars with small cross-section and high resistance. It also has an inner winding made of copper bars with larger cross-section and lower resistance. This arrangement allows the motor to produce high starting torque while limiting starting current draw. The double cage induction motor provides benefits like high efficiency, good speed regulation, lower costs, and increased robustness over traditional squirrel cage motors.
The document discusses three phase transformers. It explains that three phase transformers have three sets of primary and secondary windings wound around the legs of an iron core assembly. There are two main constructions - using three single phase transformers or a common core for the three phases. Today, a single three phase transformer is preferred as it is lighter, smaller, cheaper and slightly more efficient. The windings can be connected in various configurations including wye-wye, wye-delta, delta-wye, and delta-delta. Each configuration has different characteristics regarding voltage ratios, phase shifts, and suitability for different applications.
Three phase induction motor By Mitesh KumarMitesh Kumar
This document presents on three phase induction motors. It discusses the basic construction of an induction motor including the stationary stator and revolving rotor. It describes the two main rotor designs - squirrel cage and wound rotor. It explains the principle of operation where the rotating magnetic field produced in the stator induces currents in the rotor windings, generating torque. It provides the formula to calculate synchronous speed based on supply frequency and number of poles. Finally, it discusses applications of squirrel cage and wound rotor induction motors.
Synchronous motors operate at a constant synchronous speed determined by the supply frequency. They require an external DC excitation source to start and synchronize the rotor speed with the rotating stator magnetic field. Synchronous motors can develop torque through a wide range of speeds and loads, and are well-suited for applications requiring constant speed operation or power factor correction.
Three phase induction motors are the most common electric motors used in industry. They have a simple and rugged design, are low cost, and easy to maintain. An induction motor consists of a stationary stator and a revolving rotor. The stator contains three-phase windings that produce a rotating magnetic field when powered. This rotating field induces currents in the rotor windings which produce a torque causing the rotor to turn, though slightly slower than the rotating field. Three phase induction motors can operate across a wide range of speeds and are well suited for constant speed industrial applications.
This document summarizes the principles and operation of an induction generator. It explains that an induction generator operates when the rotor spins faster than synchronous speed, inducing a current in the stator. Reactive power is required from an external capacitor bank to generate a rotating magnetic field. Induction generators are simpler and cheaper than other generators but have lower efficiency and cannot independently regulate voltage levels. Their applications include use in variable-speed wind turbines and dynamic braking systems.
Brushless DC motors are synchronous motors powered by a DC electric source via an integrated inverter, which produces an AC electric signal to drive the motor. They were developed from Michael Faraday's early experiments with electromagnetic induction in the 1800s. Brushless DC motors have no brushes or commutators, requiring no maintenance with a much longer operating life compared to regular DC motors. They find applications in instrumentation, medical devices, appliances, automotive systems, factory automation, aerospace and military due to their high efficiency, rapid response and lack of sparking or emissions.
Starting method for 3 phase induction motorAhmed A.Hassan
The document discusses four common methods for starting 3-phase induction motors: rotor resistance starting for slip-ring motors, and direct-on-line starting, star-delta starting, and autotransformer starting for squirrel-cage motors. Rotor resistance starting allows adjusting the starting torque and current by adding external resistance to the rotor circuit. Direct-on-line starting applies full supply voltage but results in high starting current and moderate starting torque. Star-delta starting and autotransformer starting both initially apply reduced voltage to lower starting current and torque before switching to full voltage.
The document discusses the double cage induction motor. It has two rotor windings or cages that provide high starting torque at low starting current. The rotor has an outer winding made of manganese bars with small cross-section and high resistance. It also has an inner winding made of copper bars with larger cross-section and lower resistance. This arrangement allows the motor to produce high starting torque while limiting starting current draw. The double cage induction motor provides benefits like high efficiency, good speed regulation, lower costs, and increased robustness over traditional squirrel cage motors.
The document discusses three phase transformers. It explains that three phase transformers have three sets of primary and secondary windings wound around the legs of an iron core assembly. There are two main constructions - using three single phase transformers or a common core for the three phases. Today, a single three phase transformer is preferred as it is lighter, smaller, cheaper and slightly more efficient. The windings can be connected in various configurations including wye-wye, wye-delta, delta-wye, and delta-delta. Each configuration has different characteristics regarding voltage ratios, phase shifts, and suitability for different applications.
Three phase induction motor By Mitesh KumarMitesh Kumar
This document presents on three phase induction motors. It discusses the basic construction of an induction motor including the stationary stator and revolving rotor. It describes the two main rotor designs - squirrel cage and wound rotor. It explains the principle of operation where the rotating magnetic field produced in the stator induces currents in the rotor windings, generating torque. It provides the formula to calculate synchronous speed based on supply frequency and number of poles. Finally, it discusses applications of squirrel cage and wound rotor induction motors.
Synchronous motors operate at a constant synchronous speed determined by the supply frequency. They require an external DC excitation source to start and synchronize the rotor speed with the rotating stator magnetic field. Synchronous motors can develop torque through a wide range of speeds and loads, and are well-suited for applications requiring constant speed operation or power factor correction.
Three phase induction motors are the most common electric motors used in industry. They have a simple and rugged design, are low cost, and easy to maintain. An induction motor consists of a stationary stator and a revolving rotor. The stator contains three-phase windings that produce a rotating magnetic field when powered. This rotating field induces currents in the rotor windings which produce a torque causing the rotor to turn, though slightly slower than the rotating field. Three phase induction motors can operate across a wide range of speeds and are well suited for constant speed industrial applications.
This document summarizes the principles and operation of an induction generator. It explains that an induction generator operates when the rotor spins faster than synchronous speed, inducing a current in the stator. Reactive power is required from an external capacitor bank to generate a rotating magnetic field. Induction generators are simpler and cheaper than other generators but have lower efficiency and cannot independently regulate voltage levels. Their applications include use in variable-speed wind turbines and dynamic braking systems.
Brushless DC motors are synchronous motors powered by a DC electric source via an integrated inverter, which produces an AC electric signal to drive the motor. They were developed from Michael Faraday's early experiments with electromagnetic induction in the 1800s. Brushless DC motors have no brushes or commutators, requiring no maintenance with a much longer operating life compared to regular DC motors. They find applications in instrumentation, medical devices, appliances, automotive systems, factory automation, aerospace and military due to their high efficiency, rapid response and lack of sparking or emissions.
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 generator protection systems. It introduces the basic electrical quantities used for protection like current, voltage, phase angle and frequency. Protective relays use one or more of these quantities to detect faults. The document then discusses different types of relays and circuit breakers used for protection. It describes various protection zones like generator, transformer, bus, line and utilization equipment zones. The rest of the document elaborates on different protection schemes for generators including stator protection, rotor protection, loss of excitation protection and reverse power protection.
This document summarizes different types of excitation systems for alternators. It discusses the function of excitation systems to supply direct current to the field winding and control the voltage and reactive power of alternators. The three main types covered are DC excitation systems, AC excitation systems, and static excitation systems. DC excitation systems use two small DC generators as exciters but are not commonly used for large alternators now. AC excitation systems include brushless and rotating thyristor types and have advantages like eliminating brushes. Static excitation systems have no rotating parts, are suitable for medium and high capacity alternators, and have benefits like smaller size and no windage losses. The document concludes that the selection of an excitation system depends on factors like the altern
This document discusses different types of starters for DC motors and induction motors. For DC motors, it describes 3-point, 4-point, and 2-point starters. The 3-point and 4-point starters connect the armature, field, and supply. The 4-point adds a no-voltage coil terminal. The 2-point starter uses series resistance to reduce starting current. For induction motors, it discusses DOL, primary resistance, star-delta, autotransformer, and rotor resistance starters. The star-delta and autotransformer starters apply reduced voltage on start up to limit current. The rotor resistance starter connects external resistors to the rotor on start up. Assignment questions are provided to draw and explain examples of
This document discusses power system faults and protection. It defines faults as defects in electrical circuits that divert current from its intended path. The most common faults are short circuits caused by insulation or conducting path failures. Switchgear such as circuit breakers, fuses and relays are used to isolate faulty elements and ensure continuity of power supply. Protective relays detect faults using changes in current, voltage, phase angle or frequency and must clear faults within fractions of a second to prevent equipment damage. Common faults include short circuits, over/under voltage/frequency, and overheating.
This document provides reading material on DC machines for electrical engineering students. It covers the basic principles of operation and torque equations for DC motors. It describes the operating characteristics such as speed-current, torque-current and speed-torque curves for shunt and series motors. It discusses starting methods such as 2-point, 3-point and 4-point starters. Methods of speed control including armature resistance, field flux and armature voltage control are explained. The document also covers losses, efficiency testing and applications of DC machines.
A reluctance motor is a type of electric motor that induces non-permanent magnetic poles on the ferromagnetic rotor. The rotor does not have any windings. It generates torque through magnetic reluctance.
Reluctance motor sub types include synchronous, variable, switched and variable stepping.
Reluctance motors can deliver high power density at low cost, making them attractive for many applications. Disadvantages include high torque ripple (the difference between maximum and minimum torque during one revolution) when operated at low speed, and noise due to torque ripple.
Unit 04 Protection of generators and transformers PremanandDesai
The document discusses faults and protection methods for alternators and transformers. For alternators, common faults include failure of the prime mover, field failure, overcurrent, overspeed, overvoltage, and unbalanced or stator winding faults. Differential and inter-turn protection are described. For transformers, faults include open circuits, overheating, and winding short-circuits. Buchholz devices, earth fault relays, overcurrent relays, and differential systems provide protection. Earth fault protection for transformers uses a core-balance leakage scheme.
Construction of three phase induction motorDr.Raja R
This document discusses the construction of three phase induction motors. It describes that induction motors have a stationary stator and a rotating rotor. The stator contains windings that produce a rotating magnetic field when powered by a three phase supply. There are two main types of rotors - squirrel cage and wound/slip ring. Squirrel cage rotors have aluminum or copper bars shorted by end rings, making their construction simple and robust. Wound rotors have windings and slip rings to allow adding external resistance for starting. The document provides details on the construction of stators, rotors, and operating principles of both types of three phase induction motors.
Part of Lecture series on EEE-413, Electrical Drives (DC Drives) delivered by me to students of VIII Semester B.E. (Electrical), Session 2018-19.
Z. H. College of Engg. & Technology, Aligarh Muslim University, Aligarh.
Missing materials will be uploaded shortly.
Please comment and feel free to ask anything related. Thanks!
The document presents information on deep bar and double cage rotors for induction motors. Deep bar rotors have bars made of multiple parallel layers to provide high starting torque through unequal current distribution across layers while maintaining efficiency at normal speeds. Double cage rotors contain an outer cage of high resistance material and an inner cage of low resistance material to generate high starting torque from the outer cage and torque at normal speeds from the inner cage. Such rotors allow induction motors to meet the needs of high starting torque applications.
The document discusses star-delta starting of motors. It explains that a motor is initially connected in star configuration during starting to reduce the starting current by 57.7%. Once the motor reaches 75% of rated speed, it is switched to delta configuration. The advantages of this method are reduced starting current, cable size, and cost. Disadvantages include reduced starting torque and increased run-up time. It also describes the components used in a star-delta starter like contactors, overload relays, and timers.
This presentation describes the per-phase equivalent circuit of induction motor - Power flow diagram - Ratio of air gap power, rotor copper loss and mechanical power developed.
This document discusses the design of a wound rotor induction motor. It defines key terms like slip, slip rings, and brushes. It describes the basic requirements of variable speed and high starting torque. The rotor contains three-phase windings connected in a star configuration with open ends connected to slip rings. Rotor resistance can be adjusted to control torque and speed characteristics. The wound rotor design provides benefits like low starting current and high starting torque compared to a squirrel cage motor.
This document discusses different types of distance relays used for transmission line protection. It describes impedance, reactance, and admittance relays. An impedance relay operates based on the ratio of voltage to current, with a torque proportional to current and restraining torque proportional to voltage. During a fault, the impedance ratio decreases and trips the circuit breaker if it falls below a predetermined value.
1) Synchronous generators have rotor windings that produce a rotating magnetic field and stator windings where 3-phase voltage is induced. They are driven by diesel engines, water turbines, or steam turbines.
2) The rotor magnetic poles can be either salient (sticking out) or cylindrical construction and are made of laminated steel to reduce eddy currents. Stator windings are used because connections are easier than on the rotating rotor.
3) Excitation systems use slip rings and brushes or brushless exciters to supply DC current to the rotor windings. This produced the rotating magnetic field needed to induce voltage in the stator windings.
This document discusses permanent magnet brushless DC (PMBLDC) motors. It provides details on their construction, operation, advantages over conventional DC motors, and applications. Key points include:
- PMBLDC motors have a permanent magnet rotor and electronic commutation instead of brushes and commutator, making them more efficient and reliable than conventional DC motors.
- The rotor position is detected by sensors like Hall sensors or optical sensors and fed to an electronic circuit that controls the timing of voltage applied to the motor windings.
- Advantages over conventional DC motors include lower maintenance, higher speed control, and regenerative braking capability. PMBLDC motors find use in automotive, industrial, consumer
The document discusses various methods to determine the voltage regulation of a synchronous generator or alternator. It describes the synchronous impedance method, MMF (ampere-turns) method, and zero power factor (Potier) method. The synchronous impedance method calculates regulation using synchronous reactance Xs obtained from open-circuit and short-circuit tests. The MMF method considers the field mmf required for open-circuit voltage and to cancel armature reaction mmf. The zero power factor method separates armature leakage reactance from armature reaction effects using open-circuit and zero power factor tests.
The document summarizes key aspects of alternator construction and operation. It describes:
1) The main components of an alternator including the stationary stator with 3-phase winding and rotating rotor with DC field winding. Two common rotor types are salient pole and smooth cylindrical.
2) Armature and field windings, including single vs. double layer windings and full vs. short pitch windings.
3) Synchronizing and parallel operation which allows multiple alternators to run in unison by matching voltage, frequency, and phase sequence.
4) Synchronizing current, power, and torque which occur during the matching process prior to paralleling alternators.
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 generator protection systems. It introduces the basic electrical quantities used for protection like current, voltage, phase angle and frequency. Protective relays use one or more of these quantities to detect faults. The document then discusses different types of relays and circuit breakers used for protection. It describes various protection zones like generator, transformer, bus, line and utilization equipment zones. The rest of the document elaborates on different protection schemes for generators including stator protection, rotor protection, loss of excitation protection and reverse power protection.
This document summarizes different types of excitation systems for alternators. It discusses the function of excitation systems to supply direct current to the field winding and control the voltage and reactive power of alternators. The three main types covered are DC excitation systems, AC excitation systems, and static excitation systems. DC excitation systems use two small DC generators as exciters but are not commonly used for large alternators now. AC excitation systems include brushless and rotating thyristor types and have advantages like eliminating brushes. Static excitation systems have no rotating parts, are suitable for medium and high capacity alternators, and have benefits like smaller size and no windage losses. The document concludes that the selection of an excitation system depends on factors like the altern
This document discusses different types of starters for DC motors and induction motors. For DC motors, it describes 3-point, 4-point, and 2-point starters. The 3-point and 4-point starters connect the armature, field, and supply. The 4-point adds a no-voltage coil terminal. The 2-point starter uses series resistance to reduce starting current. For induction motors, it discusses DOL, primary resistance, star-delta, autotransformer, and rotor resistance starters. The star-delta and autotransformer starters apply reduced voltage on start up to limit current. The rotor resistance starter connects external resistors to the rotor on start up. Assignment questions are provided to draw and explain examples of
This document discusses power system faults and protection. It defines faults as defects in electrical circuits that divert current from its intended path. The most common faults are short circuits caused by insulation or conducting path failures. Switchgear such as circuit breakers, fuses and relays are used to isolate faulty elements and ensure continuity of power supply. Protective relays detect faults using changes in current, voltage, phase angle or frequency and must clear faults within fractions of a second to prevent equipment damage. Common faults include short circuits, over/under voltage/frequency, and overheating.
This document provides reading material on DC machines for electrical engineering students. It covers the basic principles of operation and torque equations for DC motors. It describes the operating characteristics such as speed-current, torque-current and speed-torque curves for shunt and series motors. It discusses starting methods such as 2-point, 3-point and 4-point starters. Methods of speed control including armature resistance, field flux and armature voltage control are explained. The document also covers losses, efficiency testing and applications of DC machines.
A reluctance motor is a type of electric motor that induces non-permanent magnetic poles on the ferromagnetic rotor. The rotor does not have any windings. It generates torque through magnetic reluctance.
Reluctance motor sub types include synchronous, variable, switched and variable stepping.
Reluctance motors can deliver high power density at low cost, making them attractive for many applications. Disadvantages include high torque ripple (the difference between maximum and minimum torque during one revolution) when operated at low speed, and noise due to torque ripple.
Unit 04 Protection of generators and transformers PremanandDesai
The document discusses faults and protection methods for alternators and transformers. For alternators, common faults include failure of the prime mover, field failure, overcurrent, overspeed, overvoltage, and unbalanced or stator winding faults. Differential and inter-turn protection are described. For transformers, faults include open circuits, overheating, and winding short-circuits. Buchholz devices, earth fault relays, overcurrent relays, and differential systems provide protection. Earth fault protection for transformers uses a core-balance leakage scheme.
Construction of three phase induction motorDr.Raja R
This document discusses the construction of three phase induction motors. It describes that induction motors have a stationary stator and a rotating rotor. The stator contains windings that produce a rotating magnetic field when powered by a three phase supply. There are two main types of rotors - squirrel cage and wound/slip ring. Squirrel cage rotors have aluminum or copper bars shorted by end rings, making their construction simple and robust. Wound rotors have windings and slip rings to allow adding external resistance for starting. The document provides details on the construction of stators, rotors, and operating principles of both types of three phase induction motors.
Part of Lecture series on EEE-413, Electrical Drives (DC Drives) delivered by me to students of VIII Semester B.E. (Electrical), Session 2018-19.
Z. H. College of Engg. & Technology, Aligarh Muslim University, Aligarh.
Missing materials will be uploaded shortly.
Please comment and feel free to ask anything related. Thanks!
The document presents information on deep bar and double cage rotors for induction motors. Deep bar rotors have bars made of multiple parallel layers to provide high starting torque through unequal current distribution across layers while maintaining efficiency at normal speeds. Double cage rotors contain an outer cage of high resistance material and an inner cage of low resistance material to generate high starting torque from the outer cage and torque at normal speeds from the inner cage. Such rotors allow induction motors to meet the needs of high starting torque applications.
The document discusses star-delta starting of motors. It explains that a motor is initially connected in star configuration during starting to reduce the starting current by 57.7%. Once the motor reaches 75% of rated speed, it is switched to delta configuration. The advantages of this method are reduced starting current, cable size, and cost. Disadvantages include reduced starting torque and increased run-up time. It also describes the components used in a star-delta starter like contactors, overload relays, and timers.
This presentation describes the per-phase equivalent circuit of induction motor - Power flow diagram - Ratio of air gap power, rotor copper loss and mechanical power developed.
This document discusses the design of a wound rotor induction motor. It defines key terms like slip, slip rings, and brushes. It describes the basic requirements of variable speed and high starting torque. The rotor contains three-phase windings connected in a star configuration with open ends connected to slip rings. Rotor resistance can be adjusted to control torque and speed characteristics. The wound rotor design provides benefits like low starting current and high starting torque compared to a squirrel cage motor.
This document discusses different types of distance relays used for transmission line protection. It describes impedance, reactance, and admittance relays. An impedance relay operates based on the ratio of voltage to current, with a torque proportional to current and restraining torque proportional to voltage. During a fault, the impedance ratio decreases and trips the circuit breaker if it falls below a predetermined value.
1) Synchronous generators have rotor windings that produce a rotating magnetic field and stator windings where 3-phase voltage is induced. They are driven by diesel engines, water turbines, or steam turbines.
2) The rotor magnetic poles can be either salient (sticking out) or cylindrical construction and are made of laminated steel to reduce eddy currents. Stator windings are used because connections are easier than on the rotating rotor.
3) Excitation systems use slip rings and brushes or brushless exciters to supply DC current to the rotor windings. This produced the rotating magnetic field needed to induce voltage in the stator windings.
This document discusses permanent magnet brushless DC (PMBLDC) motors. It provides details on their construction, operation, advantages over conventional DC motors, and applications. Key points include:
- PMBLDC motors have a permanent magnet rotor and electronic commutation instead of brushes and commutator, making them more efficient and reliable than conventional DC motors.
- The rotor position is detected by sensors like Hall sensors or optical sensors and fed to an electronic circuit that controls the timing of voltage applied to the motor windings.
- Advantages over conventional DC motors include lower maintenance, higher speed control, and regenerative braking capability. PMBLDC motors find use in automotive, industrial, consumer
The document discusses various methods to determine the voltage regulation of a synchronous generator or alternator. It describes the synchronous impedance method, MMF (ampere-turns) method, and zero power factor (Potier) method. The synchronous impedance method calculates regulation using synchronous reactance Xs obtained from open-circuit and short-circuit tests. The MMF method considers the field mmf required for open-circuit voltage and to cancel armature reaction mmf. The zero power factor method separates armature leakage reactance from armature reaction effects using open-circuit and zero power factor tests.
The document summarizes key aspects of alternator construction and operation. It describes:
1) The main components of an alternator including the stationary stator with 3-phase winding and rotating rotor with DC field winding. Two common rotor types are salient pole and smooth cylindrical.
2) Armature and field windings, including single vs. double layer windings and full vs. short pitch windings.
3) Synchronizing and parallel operation which allows multiple alternators to run in unison by matching voltage, frequency, and phase sequence.
4) Synchronizing current, power, and torque which occur during the matching process prior to paralleling alternators.
The document discusses direct current (DC) machines and their operation. It provides details on:
1) The basic components and construction of a DC machine including its armature winding, commutator, and field poles.
2) How an alternating current induced in the armature coils is converted to direct current via the commutator and brush assembly.
3) Different types of armature windings including lap and wave windings.
4) Factors that affect the performance of DC machines such as armature reaction and how it can be mitigated through techniques like using interpoles.
5) Equations for calculating the generated electromotive force (EMF) in a DC generator.
This document provides reading material for electrical and electronics engineering students studying electrical machines II at RGPV affiliated colleges. It covers the syllabus for the unit on DC machines, including the basic construction of DC machines, types of excitation, armature and field windings, EMF equations, armature reaction and methods to limit it, commutation processes, performance of DC generators, and different types of DC motors like metadyne, amplidyne, permanent magnet, and brushless motors. The topics are explained over several pages with diagrams and examples. Key concepts covered are the magnetic circuits, armature and commutator construction, separately excited and self-excited machines, wave and lap windings, EMF equations, ar
This document provides an overview of synchronous generators/alternators. It discusses the different types of rotor constructions including salient pole and cylindrical rotor types. It covers the basic working principle of an alternator including EMF generation and factors that affect output voltage such as armature reaction under different load power factors. Key concepts like winding configurations, pitch factor, distribution factor and EMF equation are explained. Causes of voltage regulation under load conditions due to armature resistance, reactance and armature reaction are summarized.
Synchronous generators operate on the principle of electromagnetic induction. They have a stationary armature winding and a rotating field winding supplied by a direct current source. It is advantageous to have the field winding on the rotor and armature winding on the stator because it allows for easier insulation of the high voltage winding and direct connection to the load. The frequency of the induced voltage depends on the number of rotor poles and its rotational speed. Armature reaction is the effect of the armature magnetic field on the main rotor field, distorting or strengthening it depending on the load power factor.
Incomplete PPT on first topic.pptx [Autosaved] [Autosaved].pptShubhobrataRudr
The document provides information on rotating electrical machines. It discusses the basic concepts of electromechanical energy conversion that occurs due to changes in flux linkages resulting from mechanical motion. It describes different types of machine windings including armature, field, AC, and distributed windings. The document also covers the generation of a rotating magnetic field in a three-phase system using three coils with currents that are equal in magnitude and phase-displaced by 120 degrees, resulting in a constant magnitude rotating magnetic field. It derives expressions for the induced voltages in coils and discusses factors that affect the induced voltages.
This document discusses DC machines, generators, motors, and transistors. It provides information on:
1) The brush assembly in DC machines which provides a path for current flow to and from the armature.
2) How a DC generator uses electromagnetic induction to generate voltage in its armature conductors as they move through a magnetic field.
3) Armature reaction which causes distortions in the magnetic field that reduce voltage and cause saturation. Ways to overcome this include shifting brushes or using interpoles.
4) Transistor amplifiers like the common emitter, common base, and common collector configurations and their characteristics like gain, input/output impedance.
The document discusses direct current (DC) generators, including:
1. DC generators operate by converting mechanical energy to electrical energy as conductors move through a magnetic field, inducing an electromotive force (EMF) based on Faraday's law of induction.
2. The construction of DC generators includes a yoke, rotor, stator, field electromagnets, pole cores, brushes, shaft, armature coils, commutator, and bearings. The commutator is needed to produce steady DC output from the pulsating current induced in the armature coils.
3. There are different types of DC generators including separately excited, self-excited (shunt-wound,
1. The document discusses the operation and maintenance of electrical systems in thermal power stations, including generators, transformers, motors, and distribution systems.
2. It covers topics such as AC and DC systems, single and three-phase systems, delta and star connections, grounded and ungrounded systems, and losses in electrical machines like hysteresis and eddy current losses.
3. The document also discusses components like transmission lines, substations, and the arrangement of electrical systems in thermal power stations.
The document provides information on the construction, working principle, and types of transformers. It begins by explaining the necessity of transformers in electrical power systems for stepping up and down voltages. The key points are:
- Transformers transfer power between circuits through electromagnetic induction without changing frequency. They have a primary and secondary winding wound around an iron core.
- Transformers can be used to step up or step down voltages depending on the ratio of turns in the primary and secondary windings. The voltage transformation ratio is equal to the ratio of turns.
- An ideal transformer has zero resistance windings, infinite core permeability, and is lossless. The voltage induced in each winding is directly proportional to its turns and the rate
1) The document discusses synchronous generators and their components and operation. It describes the working principles, construction details including stator, rotor, and field windings, methods of supplying field current, and armature windings.
2) Equations for induced EMF, equivalent circuits, and losses are presented. The relationships between speed, frequency, and poles are defined.
3) Efficiency is discussed as well as the main types of losses in electrical machines including copper, core, mechanical, and stray losses. Torque and power equations are also outlined.
This document provides an overview of electrical machines-II for 6th semester electrical engineering students. It outlines the key learning outcomes which include understanding synchronous machines, types of alternators, power generation processes, and the basic concepts of emf generation. The document then discusses the classifications of alternators based on their construction, the advantages of stationary armature over rotating armature construction, and determining the generated emf in an alternator. Key aspects of alternator components like the stator and rotor are also summarized.
This document discusses DC machines and provides details on various concepts related to DC generators and DC motors. It describes Maxwell's corkscrew rule and Fleming's left-hand and right-hand rules for determining magnetic fields and forces. It also explains Lenz's law, the construction and working principles of DC generators and motors, including their windings, commutation, and speed control methods. Various types of DC generators and motors are defined along with their characteristics and applications. Testing methods for determining efficiency of DC machines are also summarized.
This document discusses DC machines including Maxwell's corkscrew rule, Fleming's left and right hand rules, Lenz's law, the construction and working principles of DC generators and motors. It describes how DC generators convert mechanical energy to electrical energy using electromagnetic induction. It also explains how DC motors convert electrical energy to mechanical energy by producing torque on the armature windings when placed in a magnetic field. Various types of DC motors and methods for controlling motor speed are also summarized.
This document discusses DC machines and provides details on Maxwell's corkscrew rule, Fleming's left-hand and right-hand rules, Lenz's law, the construction and working principles of DC generators and motors. It describes how mechanical energy is converted to electrical energy in a DC generator through electromagnetic induction. DC motors are also summarized, explaining how they convert electrical energy to mechanical energy when a current-carrying conductor is placed in a magnetic field. Common applications of shunt, series, and compound DC motors are listed.
DC Machine Ppt. Presentation all rules and applicationSahilSk33
This document discusses DC machines and provides details on Maxwell's corkscrew rule, Fleming's left-hand and right-hand rules, Lenz's law, the construction and working principles of DC generators and motors. It describes commutation, armature reaction, speed control methods for DC motors using flux and armature voltage control, and testing of DC machines. Various types of DC generators and motors are discussed along with their applications.
An alternator is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current. For reasons of cost and simplicity, most alternators use a rotating magnetic field with a stationary armature.
Covid Management System Project Report.pdfKamal Acharya
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Unit 1
1. Constructional details – Types of rotors – EMF equation –
Synchronous reactance – Armature reaction – Voltage
regulation: EMF, MMF, ZPF and ASA methods –
Synchronizing and parallel operation – Synchronizing
torque – Change of excitation and mechanical input –
Two reaction theory – Determination of direct and
quadrature axis synchronous reactance using slip test –
Operating characteristics – Capability curves.
UNIT I
SYNCHRONOUS GENERATOR
2. AC Machines
UNIT – I
SYNCHRONOUS GENERATOR
Synchronous Machines Asynchronous Machines
(Induction Machine)
Synchronous
Generator
Synchronous
Motor
Induction
Generator
Induction
Motor
A primary
source of
electrical
energy
Used as motors as
well as power factor
compensators
(synchronous
condensers)
Most widely
used electrical
motors in both
domestic and
industrial
applications
Due to lack of a
separate field
excitation, these
machines are
rarely used as
generators.
3. SYNCHRONOUS GENERATOR
(a) Stationary Armature - Rotating Field (Above 5 kVA)
(b) Stationary Field – Rotating Armature (Below 5 kVA)
Types of Synchronous Machine
According to the arrangement of the field and armature
windings, synchronous machines may be classified as
4. Advantages of stationary armature - rotating field:
i) The High Voltage ac winding and its insulation not
subjected to centrifugal forces.(11kV - 33 kV) (BETTER
INSULATION)
ii) Easier to collect large currents from a stationary
member.
iii)Rotating field makes overall construction simple.
iv)Problem of sparking at the slip ring can be avoided.
v) Ventilation arrangement for HV can be Improved.
vi)The LV(110 V – 220V) dc excitation easily supplied
through slip rings and brushes to the rotor field
winding.
vii) Noiseless running is possible.
viii)Air gap length is uniform
ix) Better mechanical balancing of rotor
5. CONSTRUCTION OF ALTERNATOR
Stationary Armature - Rotating Field
An alternator has 3 phase winding on the stator and
DC field winding on the rotor.
STATOR
Stationary part of the machine.
It is built up of Sheet-Steel Lamination Core (Stampings) with slots
to hold the armature Conductor
Armature winding is connected in STAR
6.
7.
8.
9. ROTOR:
There are two types of rotor
i) Salient Pole type {Projected Poles}
ii) Non - Salient Pole type {Non – Projected Poles}
Smooth Cylindrical Type
10. Salient Pole type {Projected Poles}
It is also called Projected Poles.
Poles are mounted on the larger
circular frame.
Made up of Thick Steel Laminations.
Field Winding are connected in series.
Ends of the field winding are connected
to the DC Supply through Slip Rings
Features
Large Diameter and short Axial Length.
Poles are Laminated to reduced
Eddy Current Losses
Employed for Low and Medium Speed
120 RMP to 500 RPM
(Diesel & Hydraulic Turbines)
This cannot be used for Large speed
11. DAMPER WINDING
Pole faces are provided with damper winding
Damper winding is useful in preventing Hunting
EMF generated will be sinusoidal
Copper Bar
12.
13.
14. II) NON SALIENT POLE TYPE
Smooth cylindrical rotor or TURBO ALTERNATOR
field winding used in high speed alternators driven by steam turbines .
Features
Smaller diameter and larger axial length compared to salient pole type machines, of
the same rating.
Less Windage loss.
Speed 1200 RPM to 3000 RPM.. Better Balancing..
Noiseless Operation
Flux distribution nearly sine wave
Frequency 50 Hz
Ns = 120 F / P
Poles 2 4 6
Speed 3000 1500 1000
15.
16.
17.
18.
19. EMF Equation of an Alternator
Let
Φ = Flux per pole, Wb
P = Number of Poles
Ns = Synchronous Speed in RMP
Z = Total Number of Conductors or coil sides in series
/ Phase
Z = 2T
T = Number of coils or Turns per phase
Tph = Turns in series per phase
= ( No. of slots * No. of cond. per slot) / (2 x 3)
Zph = Conductor per phase
Zph = Z / 3. No. of phase 3
Kc or Kp = Pitch factor or coil span factor
Kd = Distribution factor
Kp = Cos (α / 2 )
Kd = Sin (mβ / 2)
m Sin(β / 2)
20.
21.
22.
23.
24. ARMATURE WINDING
3 Phase alternator carry 3 sets of winding arranged in slots
Open circuited
6 terminals
Can be connected in Star or Delta
Armature Winding Classification
1. Single Layer and Double Layer Winding
2. Full Pitch and Short Pitch Winding
3. Concentrated and Distributed Winding
25. Single Layer and Double Layer Winding
Single- layer winding
• One coil-side occupies the total slot area
• Used only in small ac machines
Double- layer winding
• Coil-sides in two layers
• Double-layer winding is more common used
above about 5kW machines
The advantages of double-layer winding over single layer winding:
a. Easier to manufacture and lower cost of the coils
b. Fractional-slot winding can be used
c. Chorded-winding is possible
d. Lower-leakage reactance and therefore , better performance of the machine
e. Better emf waveform in case of generators
26. POLE – PITCH
It is the distance between the centres of pole
faces of two adjacent poles is called pole pitch.
Pole pitch = 180 Phase angle
COIL :
A coil consists of two coil sides.
Placed in two separate slots
SLOT PITCH:
It is the phase angle between two adjustment slots
COIL SPAN OR COIL PITCH
It is the distance between two coil sides of a coil
27. Full Pitch and Short Pitch Winding
Full Pitch Winding
If the coil span is equal to pole pitch then the winding is called Full Pitch Winding
Coil Span = Pole Pitch
Short Pitch Winding
If the coil span is less than Pole
Pitch is called Short pitch
winding
e1 V e2 V
e1 V
e2 V
e2 V
28. CONCENTRATED AND DISTRIBUTED WINDING
Advantages of Short Chorded winding or Chorded Pitch Winding
1. Copper is saved
2. Mechanical strength of the coil is increased
3. Induced EMF in improved
Slot Angle : The angular displacement between any two
adjacent poles in electrical degree
Slot angle (β) = 180
(Number of slots / Pole)
29. PITCH FACTOR OR COIL SPAN FACTOR OR SHORT CHORDED FACTOR
Kp OR Kc
Pitch factor is defined as the ratio EMF induced in the Short pitch
winding to the EMF induced in the full pitch winding
E V E V
E V
α
α/2
A
B
D
C
2E
Vector Sum EMF = AB
= AC + CB
AD = BD
Kp = Cos (α / 2)
α/2
Kp = AC + CB
AD + DB
34. Arithmetic Sum of EMF = AB + BC + CD
From Vector diagram AB = Ax + xB
= r Sin (β/2) + r Sin (β/2)
AB = 2 r Sin (β/2) AB = BC = CD = 2 r Sin (β/2)
Arithmetic Sum of EMF = 3 x (2 r Sin (β/2) )
If there are ‘m’ slots for distribution, then
Arithmetic Sum /phase of the EMF = m x (2 r Sin (β/2) )
Vector Sum of EMF AD = AE + ED
Vector Sum of EMF AE = ED = r Sin (mβ/2)
Vector Sum of EMF = 2r x (Sin (mβ/2))
35. Causes of Voltage drop in Alternator
Armature Effective Resistance (Reff )
Armature Leakage Reactance (XL )
Armature Reactance
36. Armature Leakage Reactance(XL)
Three major components -Slot leakage reactance, end winding leakage reactance
and tooth tip leakage reactance.
Synchronous reactance / phase
Xs = XL + Xa
, where
Xa is the fictitious armature reaction reactance.
Synchronous impedance/phase
Zs = (Ra + jXs).
37. Armature Reaction
Effect of the armature flux on the main field flux.
Armature Reaction effect depends upon the PF of the Load
UPF - cross magnetizing.
Lag PF - demagnetizing.
Lead PF - magnetizing
38. UPF (Pure Resistive Load)
cross magnetizing
N S
Main Flux Φf Armature Flux Φa
Main Flux
Φf
Eph
Induced EMF due to Main Flux Φf
Iaph
Φa
39. Lagging PF (Purely Inductive Load)
Demagnetizing
N S
Main Flux Φf Armature Flux Φa
Main Flux
Φf
Eph
Induced EMF due to Main Flux Φf
Ia
Armature Flux
Φa
Load current
Lag the Voltage by
90
Main Flux
Decreases
DC excitation
40. Lead PF (Purely Capacitive Load)
Magnetizing
N S
Main Flux
Φf
Eph
Induced EMF due to Main Flux Φf
Ia
Armature Flux
Φa
Main Flux Φf
Armature Flux Φa
Load current
Lead the Voltage by
90
Main Flux
Increases
DC excitation
41. 1.Direct loading method
2. Synchronous impedance method or E.M.F. method
3. Ampere-turns method or M.M.F. method
4. Zero power factor method or Potier triangle method
5. ASA modified from of M.M.F. method
6. Two reaction theory
VOLTAGE REGULATION
Voltage Regulation of an alternator is defined as the change in
terminal voltage from NO load to full load divided by full-load
voltage.
% Voltage Regulation = E0 – V x 100
V
There are different methods available to determine the voltage
regulation of an alternator,
43. The prime mover drives the alternator at its synchronous speed.
The star connected armature is to be connected to a three phase load
The field winding is excited by separate d.c. supply.
To control the flux i.e. the current through field winding, a rheostat is inserted in
series with the field winding.
Eph α Φ ..... (From e.m.f. equation)
For high capacity alternators, that much full
load can not be simulated or directly
connected to the alternator. Hence method is
restricted only for small capacity alternators.
45. The method is also called E.M.F. method
The method requires following data to calculate the regulation.
1. The armature resistance per phase (Ra).
2. Open circuit characteristics which is the graph of open circuit voltage against the
field current. This is possible by conducting open circuit test on the alternator.
3. Short circuit characteristics which is the graph of short circuit current against field
current. This is possible by conducting short circuit test on the alternator.
Zs is calculated.
Ra measured and Xs obtained.
For a given armature current and power factor, Eph determined -
regulation is calculated.
46. field current. If in Amps
OCC
(Voc)ph
SCC
O A
(Ia)SC
C
B
D
E
Full
Load
Iasc
48. Phasor Diagram of a loaded Alternator
Unity PF Load
Ia IaRa
IaXs
Eph
Vph
IaZS
O A B
C
Reference as Voltage (V)
OA – Vph
AB – IaRa
BC – IaXs
AC – IaZs
OC – Eph
Consider Δ OBC
(OC)2 = (OB)2 + (BC)2
(Eph)2 = (OA + AB)2 + (BC) 2
(Eph)2 = (Vph + IaRa)2 + (IaXs) 2
Eph = √ (Vph+ IaRa)2 + (IaXs)2
49. Phasor Diagram of a loaded Alternator
Lagging PF Load
Vph
IaRa
IaXs
Eph
Ia
IaZS
O A B
C
Φ
Eph = √ (Vph Cos Φ + Ia Ra)2 + (Vph Sin Φ + Ia Xs)2
Vph Cos Φ
Vph Sin Φ
IaRa
50. Phasor Diagram of a loaded Alternator
Leading PF Load
Vph
IaRa
IaXs
Eph
Ia
IaZS
O A B
C
Φ
Eph = √ (Vph Cos Φ + Ia Ra)2 + (Vph Sin Φ - Ia Xs)2
51. Advantages of Synchronous Impedance Method
The main advantages of this method is the value of synchronous impedance Zs for
any load condition can be calculated.
Regulation of the alternator at any load condition and load power factor can
be determined.
Actual load need not be connected to the alternator
This method can be used for very high capacity alternators
Limitations of Synchronous Impedance Method
The main limitation of this method is that this method gives large values of
synchronous reactance.
This leads to high values of percentage regulation than the actual results.
Hence this method is called pessimistic method.
52. MMF method (Ampere turns method)
This method of determining the regulation of an alternator is also called
Ampere-turn method or Rothert's M.M.F. method.
The method is based on the results of open circuit test and short circuit test on an
alternator.
For any synchronous generator i.e. alternator, it requires M.M.F. which is product
of field current and turns of field winding for two separate purposes.
1. It must have an M.M.F. necessary to induce the rated terminal voltage on
open circuit.
2. It must have an M.M.F. equal and opposite to that of armature reaction m.m.f.
53. OC & SC tests conducted.
field currents
If1 (field current required to produce a voltage of (Vph + Iaph Ra cosΦ) on OC)
If2 (field current required to produce the given armature current on SC) are
added at an angle of (90±Φ).
For this total field current, Eph found from OCC and regulation calculated.
54. field current. If in Amps
OCC
SCC
FO
Short Circuit Current
Open Circuit Voltage
Full Load
Short circuit
Current
Rated
Voltage
FAR
55. Zero Power Factor Method (ZPF Method) or Potier method
The ZPF method is based on the Separation of
Armature leakage reactance (XL) and
Armature reaction effect
In the operation of any alternator, Voltage drop occurs in
Armature resistance drop(IRa)
Armature leakage reactance drop IXL
Armature reaction.
This method is also called Potier method.
Mainly due
EMF quantity
is basically M.M.F. quantity
In the synchronous impedance method all the quantities are treated as E.M.F.
quantities
In the MMF Method all the quantities are treated as M.M.F. quantities
The armature leakage reactance XL is called Potier reactance
56. To determine armature leakage reactance (EMF) and
armature reaction (MMF) separately, two tests are
performed on the alternator
1. Open circuit test
2. Zero power factor test
Open circuit test
Open circuit test
Switch Open
P.M. to drive Ns
Potential Divider from 0 to Rated Value
Zero power factor test
Switch Closed
Purely Inductive Load
Purely Inductive Load has PF Cos 90
57. field current. If in Amps
OCC
Open Circuit Voltage
(Voc)
Zero Terminal Voltage at SC Full load Zero p
A
Rated Terminal Voltage at Full load Current at
Zero pf lagging
P
Full Load ZPF
O
Tangent to OCC
Airline
B
Q
OA = QP
Horr Parallel
R
Δ PQR
Potier Triangle
S
Rated
Vph
P’
Q’
R’
S’
RS Voltage Drop Armature Leakage Reactance (IXL)
PS Gives If necessary to overcome Demagnetizing Armature Reaction
SQ rep If required to induce an EMF balancing of leakage reactance (RS)
C
58. American Standards Association Method (ASA Method)
ASA Modification of M.M.F. Method
The two methods, M.M.F. method and E.M.F. method is capable of giving the
reliable values of the voltage regulation
the magnetic circuit is assumed to be unsaturated.
This assumption is unrealistic as in practice.
It is not possible to have completely unsaturated magnetic circuit.
In salient pole alternators, it is not correct to
combine field ampere turns and armature
ampere turns.
field winding is always concentrated
Armature winding is always distributed.
Similarly the field
field and armature m.m.f. is not fully justified.
59. American Standards Association
Method (ASA Method)
Load induced EMF calculated as was done in the ZPF
method - Corresponding to this EMF, the additional field
current (If3) due to saturation obtained from OCC and air
gap line - If3 added to the resultant of If1 and If2 -For this
total field current, Eph found from
OCC and regulation calculated.
60. field current. If in Amps
OCC
O
Airline
Φ
Vph
E1ph
IaRa
IaXL
E1
Eph
Open circuit Voltage Voc
B
B’
61. American Standards Association Method (ASA Method)
The field currents If1 (field current required to produce the rated voltage of Vph from
the air gap line).
If2 (field current required to produce the given armature current on short circuit)added
at an angle of (90±Φ).
62. Synchronizing and Parallel operation
Necessary Condition for Synchronization
The process of switching of an alternator to another alternator or
with a common Bus bar without any interruption is called
Synchronization
CONDITIONS FOR PARALLEL OPERATION
1. The terminal voltage of the incoming machine must be same
as that of bus bar Voltage.
2. The frequency of the generated voltage of the incoming
machine must be same as that of bus bar frequency.
3. The phase Sequence voltage of the incoming machine must be
same as that of bus bar.(R Y B).
63. Advantages of Parallel operation
Continuity of supply is possible when Breakdown or Shut down
for maintenance of alternator in generating station
Repair and Maintenance of individual machine can be carried out
one after the other without effecting the normal routine work
Depending upon the load requirement any number of alternator
can be operated and the remaining can be put off
It is economical and improves the efficiency of the generating
station
New alternator can be connected in parallel, when the demand
increases. This reduces the capital cost of the system.
64. Methods of Synchronization of alternator
Three Methods
1. Dark lamp method.
2. Bright Lamp Method
3. Synchroscope Method
Conditions Should Satisfy
1. Voltage
2. Frequency
3. Phase Sequence
66. Alternator 1 is already (Exciting) connected with the Bus Bar and Supplying power to load
Alternator 2 is Incoming Alternator
Voltage of Incoming Alternator SHOULD be same to that of Exciting Alternator
V1 = V2 Voltage SAME
Phase Sequence
3 Lamps Glowing Uniformly together and becoming dark together Phase Sequence
is correct
LAMP Flickering together in uniform
Frequency
Difference in frequency Lamp will be glow DARK and BRIGHT alternatively
Speed of alternator 2 should be adjusted
Demerits
It is not possible to judge whether the incoming alternator is fast or slow.
The lamp can be dark even through a small value of voltage may present across the
Terminals.
69. Lamps are cross connected
Lamps will GLOW the BRIGHTEST when two voltage are in PHASE (V2)
V1 = V2 Voltage SAME
Phase sequence same LAMPS will start Flickering in uniform
Switch is closed at the middle of the Brightest period of the lamp
71. LAMP Flickering together in uniform
Synchroscope consists of STATOR and ROTOR
The ROTOR is connected to the INCOMING alternator
The STATOR is connected to the EXISTING alternator
The pointer is attached to the rotor. The pointer will indicate the correct time of
closing the switch. (12’O Position)
Frequency Different the pointer will rotate
Anti clock wise ---- Frequency of INCOMING alternator is LOW
Clock wise ---- Frequency of INCOMING alternator is Higher
72. Synchronizing Current, Power and Torque
E1 E2
Z1
=
Ra
+
Xs
Z2
=
Ra
+
Xs
E2
E1
E2
α
Er
E1
Isy
Synchronizing Current Isy = Er / (Z1 + Z2)
Synchronizing Power Psy = E1 x Isy Cos Φ1
Φ1
Synchronizing Torque Tsy = Psy / ( 2πNs / 60)
73. E1
NO LOAD
E1 = E2 NO local Current
Excitation of Alternator 1
Increasing
E1 also increases > E2
Resultant Er.= E1-E2
Er =E1 – E2
Isy
90
E1 E2
Z1
=
Ra
+
Xs
Z2
=
Ra
+
Xs
I1 I2
2I
Effect of Change in Excitation of Alternator in parallel
Circulating current Isy
Isy lags Er 90 Demagnetizing Effect REDUCES Eg Voltage
Isy leads Er 90 Magnetizing Effect increases Eg Voltage
74. Load kVAR
kW/2
kW/2
M/C 1
M/C 2
Φ
kVAR 2
kW/2
kW/2
M/C 1
M/C 2
Φ
kVAR 1
Φ1
kVA1
kVA2
Effect of Change in Excitation of Alternator in parallel
Active Power P = √3VLIL CosΦ kW
Reactive Power Q= √3VLIL SinΦ kVAR
Apparent Power S = √3VLIL kVA
Active
Power
P
Reactive Power Q
Active
Power
P
Reactive Power Q
Φ2
75. Effect of Change in Excitation of Alternator in parallel
E1 E2
Z1
=
Ra
+
Xs
Z2
=
Ra
+
Xs
I1 I2
I1 = I2 = I = 2I
V
I1
2I
Is = (E1 - E2) / 2Z
Is
I1’
Is
I2’
2I
Alternator 1 field excitation
Increasing the IF Induced voltage Increases
There is a circulating current
90 Lagging V
I2
I1’ = Is + I1
I2’ = I2 - Is
76. V
ISY
E1 = E2
E2’
E1’
δ
δ2
δ1
E Sin δ
I2’XS
I1’XS
I1XS = I2XS
I1’
I1’
+ ISY
- ISY
I1=I2
2I1=2I2 = I
E1 E2
Z1
=
Ra
+
Xs
Z2
=
Ra
+
Xs
I1 I2
2I
77. TWO REACTION THEORY
Uniform air gap Field flux and Armature flux vary sinusoidally
Air gap length is constant and reactance is also constant
Field MMF and Armature MMF act upon the
same magnetic circuit can be added vectorially
Air gap length is NOT constant and
Reactance is also NOT constant
Salient pole alternator Air gap is NOT uniform
Field flux and Armature flux cannot vary sinusoidally
Non Salient pole alternator Air gap is uniform
MMF act are different
78. According to this theory Armature MMF can be divided into two components
1. Components acting along the pole axis is called Direct axis Id
2. Components acting at right angle to the pole axis is called Quadrature axis Iq
Components acting along Direct axis Id can be magnetizing or demagnetizing
Components acting along Quadrature axis Iq is Cross Magnetization
TWO REACTION THEORY
Direct Axis Id Direct Axis Id
Quadrature Axis Iq
Quadrature Axis Iq
79. Direct Axis Id
Direct Axis Id
Direct Axis Id
Direct Axis Id
Quadrature Axis Iq
Quadrature Axis Iq
Quadrature Axis Iq
Quadrature Axis Iq
80. The reluctance offered to the mmf is lowest when
it is aligned with the field pole flux. Direct axis d-axis
The reluctance offered to the mmf is highest when
it is 90 to the field pole flux. Quadrature axis q-axis
Ff mmf wave produced by field winding along Direct axis