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.
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 summarizes the key aspects of synchronous motors. It describes how synchronous motors synchronize the rotation of their shaft to the frequency of the AC power supply. There are two main types: non-excited motors which use the stator magnetic field to induce poles on the steel rotor, and DC-excited motors which require a separate DC source to excite the rotor. Synchronous motors have advantages over other motors like constant speed operation and unity power factor, and they are commonly used where precise constant speed is required, like in power generation and precision machinery.
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.
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 induction motors, which are asynchronous AC motors that operate below synchronous speed. It describes the two main types - single phase and three phase induction motors. Three phase induction motors are commonly used in industry due to their ability to provide bulk power conversion from electrical to mechanical power. The document then discusses the construction and working principles of three phase induction motors in detail, including their stator, rotor, and how rotational motion is induced in the rotor via electromagnetic induction from the rotating stator magnetic field.
DC motors
Torque & Speed Equations
Torque -Armature current Characteristics
Speed - Armature current Characteristics
Torque-speed characteristics
Applications
Speed Control
1) Single phase induction motors use a split phase winding or capacitor start method to generate a rotating magnetic field for starting.
2) Synchronous motors operate at a constant synchronous speed and use a damper winding, pony motor, or DC motor method to reach synchronous speed before loading.
3) V curves show the relationship between armature current, field current, and excitation voltage in synchronous motors.
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.
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 summarizes the key aspects of synchronous motors. It describes how synchronous motors synchronize the rotation of their shaft to the frequency of the AC power supply. There are two main types: non-excited motors which use the stator magnetic field to induce poles on the steel rotor, and DC-excited motors which require a separate DC source to excite the rotor. Synchronous motors have advantages over other motors like constant speed operation and unity power factor, and they are commonly used where precise constant speed is required, like in power generation and precision machinery.
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.
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 induction motors, which are asynchronous AC motors that operate below synchronous speed. It describes the two main types - single phase and three phase induction motors. Three phase induction motors are commonly used in industry due to their ability to provide bulk power conversion from electrical to mechanical power. The document then discusses the construction and working principles of three phase induction motors in detail, including their stator, rotor, and how rotational motion is induced in the rotor via electromagnetic induction from the rotating stator magnetic field.
DC motors
Torque & Speed Equations
Torque -Armature current Characteristics
Speed - Armature current Characteristics
Torque-speed characteristics
Applications
Speed Control
1) Single phase induction motors use a split phase winding or capacitor start method to generate a rotating magnetic field for starting.
2) Synchronous motors operate at a constant synchronous speed and use a damper winding, pony motor, or DC motor method to reach synchronous speed before loading.
3) V curves show the relationship between armature current, field current, and excitation voltage in synchronous motors.
Synchronous machines have two sets of windings - a three-phase armature winding on the stationary stator and a DC field winding on the rotating rotor. The rotor can have either a salient pole or cylindrical structure. Large generators use brushless excitation systems to avoid maintenance issues associated with slip rings and brushes. Excitation is provided by a small AC generator (brushless exciter) mounted on the stator whose output is rectified to supply DC current to the main field winding. Proper cooling is required to dissipate heat generated in the windings.
This document discusses different types of AC motors. It describes induction motors, including single-phase and three-phase induction motors. Three-phase induction motors can have either a squirrel cage or wound rotor. Synchronous motors are also discussed, which rotate at a constant synchronous speed. While synchronous motors have high efficiency, they require auxiliary equipment to allow for self-starting. The document compares different AC motor types and provides examples of their common applications.
This document provides information about induction motors. It describes the basic construction of an induction motor, including its stator and squirrel cage or wound rotor. It explains how a rotating magnetic field is produced from the three-phase stator windings and how this induces a voltage and current in the rotor. It defines key terms like synchronous speed and slip. It also presents the equivalent circuit model of an induction motor and discusses speed control methods and power losses in induction machines.
The document discusses synchronous generators and their operation. It covers:
- The two reaction theory which separates the armature mmf into direct and quadrature axis components.
- How phasor diagrams can be used to represent the direct and quadrature axis reactances (Xd and Xq).
- The slip test method to measure Xd and Xq by taking voltage-to-current ratios with the armature mmf aligned to each axis.
- Important cautions for the slip test including keeping slip extremely low to avoid errors from damper windings or open circuit voltages reaching dangerous levels.
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.
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.
The document provides an overview of induction motors, including:
1. It describes the basic operating principle of induction motors, which induce a current in the rotor via electromagnetic induction from a rotating magnetic field in the stator.
2. It discusses different types of induction motors including single phase, three phase, squirrel cage, and slip ring rotors.
3. It provides some key formulas for induction motors relating supply frequency, pole pairs, synchronous speed, rotor speed, and slip.
SWICTH GEAR AND PROTECTION (2170906)
DISTANCE RELAY
• There are mainly Three types of distance relay
1) Impedance Relay
2) Reactance Relay
3) Mho Relay
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.
The document discusses induction motors. It explains that an induction motor works by electromagnetic induction, where the alternating current in the stator produces a rotating magnetic field that induces current in the rotor and causes it to turn. It describes the basic components of induction motors including the stator, rotor, and housing. It also discusses how varying the frequency of the alternating current supply can be used to control the motor's speed.
This document contains 5 numerical problems related to analyzing the operation of three-phase induction machines. Problem 1 involves calculating various speeds, frequencies, and voltages given machine specifications operating at rated slip. Problem 2 involves calculating power values given a 3-phase induction motor's rated power and windage/friction losses. Problem 3 involves calculating starting and full-load operating values like current, slip, and efficiency given motor parameters. Problem 4 involves determining the resistance value needed in the rotor circuit to reduce the motor speed from operating at a given speed and load to a lower speed. Problem 5 involves calculating torque values from the ratio of starting to full-load rotor current.
The document discusses permanent magnet brushless DC motors, including their construction with a permanent magnet rotor, electronic commutation instead of a mechanical commutator, and applications in automotive, industrial, computer and small appliance uses. It provides details on the operation, classifications based on pole arc and waveform, and common controller circuits used for permanent magnet brushless DC motors.
Three phase Induction Motor (Construction and working Principle)Sharmitha Dhanabalan
The three phase induction motor consists of a stationary stator and a rotating rotor. The stator contains three-phase windings that generate a rotating magnetic field. This rotating field induces currents in the rotor windings, causing the rotor to turn. There are two common types of rotors - squirrel cage and wound rotor. A squirrel cage rotor has embedded conductors inside its core that are permanently short-circuited. A wound rotor has three insulated windings connected to slip rings to allow external resistance control. Due to slight differences in speed, the rotor always rotates at a slightly slower synchronous speed than the stator's magnetic field.
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.
An alternator is an electrical generator that converts mechanical energy to electrical energy. It uses a rotating magnetic field with a stationary armature. The working principle relies on Faraday's law of electromagnetic induction. As the armature rotates within the magnetic field, an alternating current is produced. The main components are the stator with stationary armature windings and the rotor with a rotating magnetic field supplied by a DC current. Armature reaction causes the magnetic field to be distorted by the armature current. Alternators have various applications including in automobiles, power plants, and for providing regenerative braking in induction motors. Induction generators can also be used to convert the rotational energy of windmills into electrical energy.
This document discusses voltage source inverter (VSI) and current source inverter (CSI) fed induction motor drives. It explains that the torque produced by an induction motor is proportional to the slip at stable operation, and inversely proportional to the slip at unstable operation. It also notes that induction motors should always be operated at or near zero slip for normal operation. The document describes how VSI and CSI topologies work, including using PWM inverters to vary frequency and voltage. It discusses reasons why MOSFET or IGBT devices are preferred over SCRs. In addition, it explains that CSI drives control torque by varying the DC link current to change output voltage.
This document discusses different types of directional over current relays. It explains that directional over current relays operate when fault current flows in a particular direction and will not operate if power flows in the opposite direction. It provides details on 30 and 90 degree connections for directional relays and describes the construction and operation of non-directional over current relays and shaded pole type directional over current relays.
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 discusses single-phase induction motors. It describes how they use two perpendicular windings and a capacitor to generate a rotating magnetic field for starting torque. The operating principle is explained using double revolving field theory, where the pulsating magnetic field is divided into two fields rotating in opposite directions. Starting torque is generated through the interaction of these fields with current induced in the squirrel cage rotor. Shaded pole motors, a less effective but cheaper alternative, use a shorted winding in parts of the poles to generate an unbalanced rotating field for starting.
The document discusses protection schemes for transformers. It describes faults that can occur in transformers such as open circuits, overheating, and winding short circuits. It then discusses different protection systems for transformers including Buchholz relays, earth fault relays, overcurrent relays, and differential protection systems. Differential protection systems operate by comparing currents from current transformers on both sides of the transformer and tripping the circuit breaker if a difference is detected, indicating an internal fault. The combination of protection schemes provides comprehensive protection for transformers.
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 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.
This document discusses different types of AC motors. It describes induction motors, including single-phase and three-phase induction motors. Three-phase induction motors can have either a squirrel cage or wound rotor. Synchronous motors are also discussed, which rotate at a constant synchronous speed. While synchronous motors have high efficiency, they require auxiliary equipment to allow for self-starting. The document compares different AC motor types and provides examples of their common applications.
This document provides information about induction motors. It describes the basic construction of an induction motor, including its stator and squirrel cage or wound rotor. It explains how a rotating magnetic field is produced from the three-phase stator windings and how this induces a voltage and current in the rotor. It defines key terms like synchronous speed and slip. It also presents the equivalent circuit model of an induction motor and discusses speed control methods and power losses in induction machines.
The document discusses synchronous generators and their operation. It covers:
- The two reaction theory which separates the armature mmf into direct and quadrature axis components.
- How phasor diagrams can be used to represent the direct and quadrature axis reactances (Xd and Xq).
- The slip test method to measure Xd and Xq by taking voltage-to-current ratios with the armature mmf aligned to each axis.
- Important cautions for the slip test including keeping slip extremely low to avoid errors from damper windings or open circuit voltages reaching dangerous levels.
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.
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.
The document provides an overview of induction motors, including:
1. It describes the basic operating principle of induction motors, which induce a current in the rotor via electromagnetic induction from a rotating magnetic field in the stator.
2. It discusses different types of induction motors including single phase, three phase, squirrel cage, and slip ring rotors.
3. It provides some key formulas for induction motors relating supply frequency, pole pairs, synchronous speed, rotor speed, and slip.
SWICTH GEAR AND PROTECTION (2170906)
DISTANCE RELAY
• There are mainly Three types of distance relay
1) Impedance Relay
2) Reactance Relay
3) Mho Relay
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.
The document discusses induction motors. It explains that an induction motor works by electromagnetic induction, where the alternating current in the stator produces a rotating magnetic field that induces current in the rotor and causes it to turn. It describes the basic components of induction motors including the stator, rotor, and housing. It also discusses how varying the frequency of the alternating current supply can be used to control the motor's speed.
This document contains 5 numerical problems related to analyzing the operation of three-phase induction machines. Problem 1 involves calculating various speeds, frequencies, and voltages given machine specifications operating at rated slip. Problem 2 involves calculating power values given a 3-phase induction motor's rated power and windage/friction losses. Problem 3 involves calculating starting and full-load operating values like current, slip, and efficiency given motor parameters. Problem 4 involves determining the resistance value needed in the rotor circuit to reduce the motor speed from operating at a given speed and load to a lower speed. Problem 5 involves calculating torque values from the ratio of starting to full-load rotor current.
The document discusses permanent magnet brushless DC motors, including their construction with a permanent magnet rotor, electronic commutation instead of a mechanical commutator, and applications in automotive, industrial, computer and small appliance uses. It provides details on the operation, classifications based on pole arc and waveform, and common controller circuits used for permanent magnet brushless DC motors.
Three phase Induction Motor (Construction and working Principle)Sharmitha Dhanabalan
The three phase induction motor consists of a stationary stator and a rotating rotor. The stator contains three-phase windings that generate a rotating magnetic field. This rotating field induces currents in the rotor windings, causing the rotor to turn. There are two common types of rotors - squirrel cage and wound rotor. A squirrel cage rotor has embedded conductors inside its core that are permanently short-circuited. A wound rotor has three insulated windings connected to slip rings to allow external resistance control. Due to slight differences in speed, the rotor always rotates at a slightly slower synchronous speed than the stator's magnetic field.
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.
An alternator is an electrical generator that converts mechanical energy to electrical energy. It uses a rotating magnetic field with a stationary armature. The working principle relies on Faraday's law of electromagnetic induction. As the armature rotates within the magnetic field, an alternating current is produced. The main components are the stator with stationary armature windings and the rotor with a rotating magnetic field supplied by a DC current. Armature reaction causes the magnetic field to be distorted by the armature current. Alternators have various applications including in automobiles, power plants, and for providing regenerative braking in induction motors. Induction generators can also be used to convert the rotational energy of windmills into electrical energy.
This document discusses voltage source inverter (VSI) and current source inverter (CSI) fed induction motor drives. It explains that the torque produced by an induction motor is proportional to the slip at stable operation, and inversely proportional to the slip at unstable operation. It also notes that induction motors should always be operated at or near zero slip for normal operation. The document describes how VSI and CSI topologies work, including using PWM inverters to vary frequency and voltage. It discusses reasons why MOSFET or IGBT devices are preferred over SCRs. In addition, it explains that CSI drives control torque by varying the DC link current to change output voltage.
This document discusses different types of directional over current relays. It explains that directional over current relays operate when fault current flows in a particular direction and will not operate if power flows in the opposite direction. It provides details on 30 and 90 degree connections for directional relays and describes the construction and operation of non-directional over current relays and shaded pole type directional over current relays.
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 discusses single-phase induction motors. It describes how they use two perpendicular windings and a capacitor to generate a rotating magnetic field for starting torque. The operating principle is explained using double revolving field theory, where the pulsating magnetic field is divided into two fields rotating in opposite directions. Starting torque is generated through the interaction of these fields with current induced in the squirrel cage rotor. Shaded pole motors, a less effective but cheaper alternative, use a shorted winding in parts of the poles to generate an unbalanced rotating field for starting.
The document discusses protection schemes for transformers. It describes faults that can occur in transformers such as open circuits, overheating, and winding short circuits. It then discusses different protection systems for transformers including Buchholz relays, earth fault relays, overcurrent relays, and differential protection systems. Differential protection systems operate by comparing currents from current transformers on both sides of the transformer and tripping the circuit breaker if a difference is detected, indicating an internal fault. The combination of protection schemes provides comprehensive protection for transformers.
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 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.
DC generators convert mechanical energy to electrical energy using electromagnetic induction. They have a stationary part that produces a magnetic field and a rotating part called the armature. As the armature rotates in the magnetic field, a current is induced based on Faraday's law of induction. The commutator ensures the current flows in one direction to the load. The main parts are the magnetic frame, field coils, armature core and windings, commutator and brushes. The types of DC generators are separately excited, shunt, series and compound wound which differ in how the field and armature windings are connected. They have various applications including battery charging, motor operation, and power distribution.
- The document discusses electric generators, specifically DC generators. It describes the key components of a DC generator including the yoke, pole cores, pole shoes, pole coils, armature core, armature winding, commutator, bearings, and brushes.
- It explains the working principle of a DC generator, including how rotation of the armature in a magnetic field generates an induced electromotive force (emf) via Faraday's law of induction. The commutator is described as collecting the current from the armature coils and delivering DC power to an external load.
- Equations for calculating the generated emf are provided, and different types of DC generator circuits are summarized including separately excited,
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
1. Three phase induction motors have a rotating magnetic field produced by a three phase stator winding that causes the rotor to turn.
2. The rotor can be either a squirrel cage (copper or aluminum bars short circuited by end rings) or wound construction.
3. Starters are used to reduce the starting current by lowering the supply voltage and improve starting torque by increasing rotor resistance during start up. Common starting methods include direct-on-line, star-delta, and auto transformer starters.
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.
This document provides information about three-phase induction motors. It discusses the construction of induction motors including their stators and rotors. Squirrel cage and wound rotors are described. The document explains how a rotating magnetic field is produced in the stator to induce currents in the rotor. It discusses the principle of operation, slip speed, rotor current frequency, starting torque, and the relationship between torque and rotor power factor. Advantages and disadvantages of induction motors are also summarized.
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.
The document discusses synchronous generators. It begins by listing various topics related to synchronous generators including constructional details, types of rotors, the EMF equation, synchronous reactance, armature reaction, voltage regulation methods, synchronization, and operating characteristics. It then provides more details on synchronous generators, describing their construction, types including salient pole and cylindrical rotors, EMF equation derivation, armature windings, and causes of voltage drops. Finally, it discusses various methods for determining voltage regulation including the direct loading method, synchronous impedance method, MMF method, zero power factor method, and two reaction theory.
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 the key concepts of induction motors. It explains that an induction motor operates by using a rotating magnetic field in the stator to induce currents in the rotor that generate torque. It describes the different components of an induction motor including the squirrel cage and wound rotors. It also discusses important concepts like slip speed, synchronous speed, rotor frequency, equivalent circuits, power flow, and how torque is developed based on the interaction between stator and rotor magnetic fields.
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.
The document discusses the principle of operation of a 3-phase alternator. It begins by explaining how synchronous generators work using Faraday's law of electromagnetic induction to generate AC voltages through relative motion of conductors and magnetic flux. It then describes the different types of synchronous machines, including those with salient poles and cylindrical rotors. The document goes on to explain the components and working of single-phase and three-phase alternators, how frequency depends on rotor speed and pole number, voltage regulation, and open/short-circuit characteristics. Power flow is described using equivalent circuit diagrams and the relationship between load angle and maximum power transfer is shown.
The document discusses the principle of operation of a 3-phase alternator. It begins by explaining how synchronous generators work using Faraday's law of electromagnetic induction to generate AC voltages through relative motion of conductors and magnetic flux. It then describes the different types of synchronous machines, including those with salient poles and cylindrical rotors. The document goes on to explain the components and working of single-phase and three-phase alternators, how voltage regulation is achieved, and it discusses open circuit, short circuit and load characteristics.
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.
Electro-mechanical relays operate using electromagnetic attraction or induction. Common relay types include attracted armature, balanced beam, and induction disc/cup relays. Relays can be instantaneous, have a definite time lag, or be inverse-time depending on how their operating time relates to current. Relays are used in applications like overcurrent protection. Modern relays also include static and numerical relays.
Visualization of magnetic field produced by the field winding excitation with...BhangaleSonal
There are a few ways to detect magnetic fields, one of the most reliable is with magnetic viewer film. This unique film suspends tiny nickel particles over a thin layer of viscous material allowing the particles to align with magnetic fields. It shows the location, as well as how many poles, a magnet has. Magnetic field lines can be drawn by moving a small compass from point to point around a magnet. At each point, draw a short line in the direction of the compass needle. Joining the points together reveals the path of the magnetic field lines.
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The aim of this project is to provide the complete information of the National and
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entering the data of eachmatch, we can get all type of reports instantly, which will be
useful to call back history of each player. Also the team performance in each match can
be obtained. We can get a report on number of matches, wins and lost.
This is an overview of my career in Aircraft Design and Structures, which I am still trying to post on LinkedIn. Includes my BAE Systems Structural Test roles/ my BAE Systems key design roles and my current work on academic projects.
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Jahangir.
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2. 2
SYNCHRONOUS GENERATOR
• Synchronous generator operates on the
principle that when the magnetic flux
linking a conductor changes, an e.m.f. is
induced in the conductor.
• It has an armature winding and a field
winding,
• It is more convenient and advantageous
to place the field winding on the rotor
and armature winding on the stator.
Introduction
Lecture Notes by Dr.R.M.Larik
3. 3
SYNCHRONOUS GENERATOR
• It is easier to insulate stationary winding for higher voltages
because they are not subjected to centrifugal forces and also extra
space is available due to the stationary arrangement of the
armature.
• The stationary 3-phase armature can be directly connected to load
without going through large, unreliable slip rings and brush-gear.
• Since the excitation current is much smaller as compared to load
current, the slip rings and brush gear required are of light
construction.
• Due to simple and robust construction of the rotor, higher speed of
rotating d.c. field is possible.
Advantages of Stationary Armature
Lecture Notes by Dr.R.M.Larik
4. 4
CONSTRUCTION OF SYNCHRONOUS GENERATOR
• It is the stationary part of the machine and is built up of sheet-steel
laminations having slots on its inner periphery.
• A 3-phase winding is placed in these slots and serves as the
armature winding of the alternator.
• The armature winding is connected in star with neutral grounded.
Stator
Rotor
• The rotor carries a field winding supplied with direct current
through the slip rings by a separate d.c. source.
• This d.c. source (exciter) is generally a small d.c. generator
mounted on the shaft of the alternator.
• Rotor construction is of salient (projected) pole type and non-
salient (cylindrical) pole typeLecture Notes by Dr.R.M.Larik
5. 5
CONSTRUCTION OF SYNCHRONOUS GENERATOR (Contd.)
Rotor (Contd.)
• In this type, salient or projected
poles are mounted on a large
circular steel frame which is
fixed to the shaft of the
alternator.
• The individual field pole
windings are connected in series
such that when the field winding
is energized by the exciter,
adjacent poles have opposite
polarities.
Salient Pole Type
Lecture Notes by Dr.R.M.Larik
6. 6
CONSTRUCTION OF SYNCHRONOUS GENERATOR (Contd.)
Rotor (Contd.)
• Low and medium-speed alternators (120-400 r.p.m.), those driven
by diesel engines or water turbines, have salient pole type rotors
due to the following reasons:
− The salient field poles would cause an excessive windage
loss if driven at high speed and would tend to produce noise.
− Salient-pole construction cannot be made strong enough to
withstand the mechanical stresses to which they may be
subjected at higher speeds.
Salient Pole Type (Contd.)
• For a frequency of 50 Hz, we must use a large number of poles
on the rotor of slow-speed alternators.
• Low-speed rotors possess a large diameter to provide necessary
space for the poles.Lecture Notes by Dr.R.M.Larik
7. 7
CONSTRUCTION OF SYNCHRONOUS GENERATOR (Contd.)
Rotor (Contd.)
• Non-salient pole type rotor is made
of smooth solid forged-steel
cylinder having a number of slots
along the outer surface.
• Field windings are embedded in
the slots and are connected in
series to the slip rings through
which they are energized by the
d.c. exciter.
• The regions forming the poles are
left unslotted.
Non-Salient Pole Type
Lecture Notes by Dr.R.M.Larik
8. 8
CONSTRUCTION OF SYNCHRONOUS GENERATOR (Contd.)
Rotor (Contd.)
• High-speed generators (1500 or 3000 r.p.m.), driven by steam
turbines, use non-salient type rotors due to the reasons:
− It gives noiseless operation at high speeds.
− The flux distribution around the periphery is nearly a sine wave
and hence a better e.m.f. waveform is obtained than in the case
of salient-pole type.
• Since steam turbines run at high speed and a frequency of 50 Hz is
required, we need a small number of poles on the rotor.
• We can not use less than 2 poles, hence, the highest possible
speed will be 3000 r.p.m.
Non-Salient Pole Type (Contd.)
Lecture Notes by Dr.R.M.Larik
9. 9
OPERATION
• The rotor winding is energized from the d.c. exciter and alternate N
and S poles are developed on the rotor.
• When the rotor is rotated in anti-clockwise direction by a prime
mover, the stator or armature conductors are cut by the magnetic
flux of rotor poles.
• Consequently, e.m.f. is induced in the armature conductors due to
electromagnetic induction.
• The induced e.m.f. is alternating since N and S poles of rotor
alternately pass the armature conductors.
• Direction of the induced e.m.f. can be determined by Fleming’s right
hand rule and the frequency is given by;
f = NP/120
where N = speed of rotor in r.p.m.
P = number of rotor polesLecture Notes by Dr.R.M.Larik
10. 10
OPERATION (Contd.)
• Magnitude of the voltage induced in each phase depends upon the
rotor magnetic flux, the number and position of the conductors in the
phase and the speed of the rotor.
• Magnitude of induced e.m.f. depends upon the speed of rotation
and the d.c. exciting current.
• Magnitude of e.m.f. in each phase of stator winding is same,
however, they differ in phase by 120° electrical.
Lecture Notes by Dr.R.M.Larik
11. 11
FREQUENCY
• Frequency of induced e.m.f. in the stator depends on speed and the
number of poles.
Let N = rotor speed in r.p.m.
P = number of rotor poles
f = frequency of e.m.f. in Hz
• Consider a stator conductor that is successively swept by the N and
S poles of the rotor.
• If a positive voltage is induced when a N-pole sweeps across the
conductor, a similar negative voltage is induced when a S-pole
sweeps.
Lecture Notes by Dr.R.M.Larik
12. 12
FREQUENCY (Contd.)
• Thus one complete cycle of e.m.f. is generated in the conductor as
a pair of poles passes it.
No. of cycles/revolution = No. of pairs of poles = P/2
No. of revolutions/second = N/60
No. of cycles/second = (P/2)(N/60) = N P/120
But number of cycles of e.m.f. per second is its frequency.
f = NP/120
N is the synchronous speed generally represented by Ns
• For a given alternator, the number of rotor poles is fixed, hence, the
alternator must run at synchronous speed to give the desired
frequency.
• For this reason, an alternator is also called synchronous generator.
Lecture Notes by Dr.R.M.Larik
13. 13
A.C. ARMATURE WINDINGS
• A.C. armature windings are generally open-circuit type i.e., both ends
are brought out.
• An open-circuit winding is one that does not close on itself i.e., a
closed circuit will not be formed until some external connection is
made to a source or load.
• The following are the general features of a.c. armature windings:
− A.C. armature windings are symmetrically distributed in slots
around the complete circumference of the armature.
− Distributed winding has two principal advantages:
a) Distributed winding generates a voltage in the form of sin wave.
b) Copper is evenly distributed on the armature surface resulting in
uniform heating of winding which can be easily cooled.
Lecture Notes by Dr.R.M.Larik
14. 14
A.C. ARMATURE WINDINGS (Contd.)
− A.C. armature windings may use full-pitch coils or fractional-pitch
coils
− A coil with a span of 180° electrical is called a full-pitch coil with
two sides of the coil occupyng identical positions under adjacent
opposite poles and the e.m.f. generated in the coil is maximum.
− A coil with a span of less than 180° electrical is called a fractional-
pitch coil (For example, a coil with a span of 150° electrical would
be called a 5/6 pitch coil) and the e.m.f. induced in the coil will be
less than that of a full-pitch coil.
− Most of a.c. machines use double layer armature windings i.e. one
coil side lies in the upper half of one slot while the other coil side
lies in the lower half of another slot spaced about one-pole pitch
from the first one.
Lecture Notes by Dr.R.M.Larik
15. 15
E.M.F. EQUATION
Let Z = No. of conductors or coil sides in series per phase
= Flux per pole in webers
P = Number of rotor poles
N = Rotor speed in r.p.m.
In one revolution (60/N second), each stator conductor is cut by P
webers i.e.,
d = P; and dt = 60/N
Average e.m.f. induced in one stator conductor
=
dϕ
dt
=
Pϕ
Τ60 N
=
PϕN
60
volts
Since there are Z conductors in series per phase,
Average e.m.f. /phase =
PϕN
60
x Z
=
PϕZ
60
x
120 f
P
N =
120 f
P
= 2 f Z VoltsLecture Notes by Dr.R.M.Larik
16. 16
E.M.F. EQUATION
R.M.S. value of e.m.f./phase = Average value of e.m.f. per phase x
form factor
= 2 f Z x 1.11 = 2.22 f Z Volts
E r.m.s. per phase = 2.22 f Z volts (i)
If Kp and Kd are the pitch factor and distribution factor of the armature
winding, then,
E r.m.s. per phase = 2.22 Kp Kd f Z Volts (ii)
Sometimes the turns (T) per phase rather than conductors per phase
are specified, in that case, eq. (ii) becomes:
E r.m.s. per phase = 4.44 Kp Kd f T Volts (iii)
The line voltage will depend upon whether the winding is star or delta
connected.
Lecture Notes by Dr.R.M.Larik
17. 17
ARMATURE REACTION
• When an alternator is running at no-load, there will be no current
flowing through the armature winding and magnetic flux produced in
the air-gap will be only due to rotor field.
• When the alternator is loaded, the three-phase currents will produce
an additional magnetic field in the air-gap.
• The effect of armature flux on the flux produced by field ampere-turns
is called armature reaction.
• The armature flux and the flux produced by rotor ampere-turns rotate
at a synchronous speed in the same direction, hence, the two fluxes
are fixed in space relative to each other.
• Modification of flux in the air-gap due to armature flux depends on the
magnitude of stator current and on the power factor of the load.
• Load power factor determines whether the armature flux distorts,
opposes or helps the main flux.
Lecture Notes by Dr.R.M.Larik
18. 18
ARMATURE REACTION
• When armature is on open-circuit,
there is no stator current and the flux
due to rotor current is distributed
symmetrically in the air-gap
• Since the direction of the rotor is
assumed clockwise, the generated
e.m.f. in phase R1R2 is at its
maximum and is towards the paper
in the conductor R1 and outwards in
conductor R2.
Load at Unity Power Factor
• No armature flux is produced since no current flows in the
armature winding.
Lecture Notes by Dr.R.M.Larik
19. 19
ARMATURE REACTION (Contd.)
• In case a resistive load (unity p.f.) is
connected across the terminals of
the alternator, according to right-
hand rule, the current is “in” in the
conductors under N-pole and “out” in
the conductors under S-pole.
• Therefore, the armature flux is
clockwise due to currents in the top
conductors and anti-clockwise due to
currents in the bottom conductors.
Load at Unity Power Factor (Contd.)
• The armature flux is at 90° to the main flux (due to rotor
current) and is behind the main flux.
Lecture Notes by Dr.R.M.Larik
20. 20
ARMATURE REACTION (Contd.)
• In this case, the flux in the air-gap is distorted but not weakened.
• Therefore, at unity p.f., the effect of armature reaction is merely
to distort the main field; there is no weakening of the main field
and the average flux practically remains the same.
• Since the magnetic flux due to stator currents (i.e., armature
flux) rotate; synchronously with the rotor, the flux distortion
remains the same for all positions of the rotor.
Load at Unity Power Factor (Contd.)
Lecture Notes by Dr.R.M.Larik
21. 21
ARMATURE REACTION (Contd.)
• When a pure inductive load
(zero p.f. lagging) is connected
across the terminals of the
alternator, current lags behind
the voltage by 90°.
• This means that current will be
maximum at zero e.m.f. and
vice-versa.
Load at Zero Power Factor Lagging
• Figure shows the condition when the alternator is supplying
resistive load.
• Note that e.m.f. as well as current in phase R1R2 is maximum in this
position.
Lecture Notes by Dr.R.M.Larik
22. 22
ARMATURE REACTION (Contd.)
• When the generator is supplying a
pure inductive load, the current in
phase R1R2 will not reach its
maximum value until N-pole
advanced 90° electrical
• Now the armature flux is from right to
left and field flux is from left to right.
Load at Zero Power Factor Lagging (Contd.)
• All the flux produced by armature current (i.e., armature flux)
opposes the field flux and, therefore, weakens it.
• In other words, armature reaction is demagnetizing.
Lecture Notes by Dr.R.M.Larik
23. 23
ARMATURE REACTION (Contd.)
• When pure capacitive load (zero p.f.
leading) is connected to the alternator,
the current in armature windings will
lead the induced e.m.f. by 90°.
• Effect of armature reaction will be the
reverse that for pure inductive load.
Load at Zero Power Factor Leading
• Armature flux aids the main flux and generated e.m.f. is increased.
• Figure shows the condition when alternator is supplying resistive load
• The e.m.f. as well as current in phase R1R2 is max in this position
• When alternator is supplying pure capacitive load, the max current in
R1R2 will occur 90° before occurrence of max induced e.m.f.
Lecture Notes by Dr.R.M.Larik
24. 24
ARMATURE REACTION (Contd.)
• When the generator is supplying a
pure capacitive load, the maximum
current in R1R2 will occur 90° electrical
before the occurrence of maximum
induced e.m.f.
• Therefore, maximum current in phase
R1R2 will occur if the position of the
rotor remains 90° behind as compared
to its position under resistive load
Load at Zero Power Factor Leading (Contd.)
• It is clear that armature flux is now in the same direction as the field
flux and, therefore, strengthens it.
Lecture Notes by Dr.R.M.Larik
25. 25
ARMATURE REACTION (Contd.)
• This causes an increase in the generated voltage.
• Hence at zero p.f. leading, the armature reaction strengthens the
main flux.
• For intermediate values of p.f, the effect of armature reaction is
partly distorting and partly weakening for inductive loads.
• For capacitive loads, the effect of armature reaction is partly
distorting and partly strengthening.
Load at Zero Power Factor Leading (Contd.)
Lecture Notes by Dr.R.M.Larik
26. 26
ALTERNATOR EQUIVALENT CIRCUIT
• All the quantities are per phase.
E0 = No-load e.m.f.
E = Load induced e.m.f.
• E is induced e.m.f. after
allowing for armature reaction.
• It is equal to phasor difference
of E0 and Ia XAR.
• Terminal voltage V is less than E by the voltage drops in XL and Ra.
E = V + Ia (Ra + j XL )
and E0 = E + Ia ( j XAR )
Lecture Notes by Dr.R.M.Larik
27. 27
SYNCHRONOUS REACTANCE (XS)
• Sum of armature leakage
reactance (XL) and reactance of
armature reaction (XAR) is called
synchronous reactance Xs .
Xs = XL + XAR
• It is a fictitious reactance employed to
account for the voltage effects in the
armature circuit produced by the:
− actual armature leakage reactance
− change in the air-gap flux caused by armature reaction.
• The circuit is simplified as shown.
• Synchronous impedance, Zs = Ra + j Xs
Lecture Notes by Dr.R.M.Larik
28. 28
SYNCHRONOUS REACTANCE (XS) (Contd.)
• Synchronous impedance is the
fictitious impedance employed
to account for the voltage
effects in the armature circuit
produced by the:
− actual armature resistance
− actual armature leakage
reactance
− change in the air-gap flux produced by armature reaction.
• Relationship between generator output voltage and load terminal
voltage is given by:
E0 = V + IaZs
= V + Ia (R + j Xs)
Lecture Notes by Dr.R.M.Larik
29. 29
PHASOR DIAGRAM OF A LOADED ALTERNATOR
• Consider a Y-connected alternator supplying inductive load, the
load p.f. angle being ϕ.
• In the last slide the figure shows the equivalent circuit of the
alternator per phase i.e. all quantities are per phase.
• Considering the vector diagram:
AC2 = AB2 + BC2
Eo
2 = (AD + BD)2 + (BE + CE)2
Since AD = V cos ϕ, BE = DF = V sin ϕ
BD = I Ra, CE = I Xs
Eo
2 = (V cos ϕ + I Ra)2 + (V sin ϕ + I Xs )2
Eo = V cos ϕ + I Ra
2 V sin ϕ + I Xs
2
Lecture Notes by Dr.R.M.Larik
30. 30
PHASOR DIAGRAM OF A LOADED ALTERNATOR
Problem 1(a): A 3-phase, star-connected alternator supplies a load
of 10 MW at p.f. 0.85 lagging and at 11 kV (terminal voltage). Its
resistance is 0.1 ohm per phase and synchronous reactance 0.66
ohm per phase. Calculate the e.m.f. generated per phase.
Solution:
F.L. output current =
10 x 106
3 x 11000 x 0.85
= 618 A
I Ra drop = 618 x 0.1 = 61.8 V
I XS drop = 618 x 0.66 = 408 V
Terminal voltage/phase = 11,000 / 3
= 6350 V
ϕ = cos -1 (0.85) = 31.8°; sin ϕ = sin 31.8° = 0.527
Lecture Notes by Dr.R.M.Larik
31. 31
PHASOR DIAGRAM OF A LOADED ALTERNATOR
Problem 1(a):
Solution (Contd.):
As seen from the vector diagram I instead
of V has been taken along reference
vector,
E0 = V cos ϕ + I Ro
2 + V sin ϕ + I Xs
2
= 6350 x 0.85 + 61.8 2 + 6350 x 0.527 + 408 2
= 6625 V
Problem 1(b): A 3-phase, synchronous generator is supplying a load of
100 kW at 11 kV (terminal voltage). The p.f. of load is 0.8 lagging. The
armature resistance is 0.3 ohm per phase and synchronous reactance
Xs is 0.5 ohm per phase. Calculate the e.m.f. generated in alternator.
Eo and V are per phase values.
Lecture Notes by Dr.R.M.Larik
32. 32
VOLTAGE REGULATION
• The voltage regulation of an alternator is defined as the change in
terminal voltage from no-load to full-load (the speed and field
excitation being constant) divided by full-load voltage.
% Voltage regulation =
No load voltage − Full load voltage
Full load voltage
x 100
=
Eo − V
V
x 100
where Eo = Terminal voltage of generator at no load
V = Terminal voltage of generator at full load
• E0 - V is the arithmetic difference and not the phasor difference.
• The factors affecting the voltage regulation of an alternator are:
− i) Ia Ra drop in armature winding
− ii) Ia XL drop in armature winding
− iii) Voltage change due to armature reaction
Lecture Notes by Dr.R.M.Larik