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.
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. A DC machine can operate as either a generator or motor. It converts mechanical power to electrical power as a generator and converts electrical power to mechanical power as a motor.
2. The main components of a DC machine are the stator, rotor, field windings, armature windings, commutator, and brushes. The field windings produce flux and the armature windings, which rotate, cut this flux to generate voltage or consume current depending on if it is operating as a generator or motor.
3. Armature reaction causes the magnetic neutral axis to shift from its ideal position, requiring careful brush placement. Commutation is the process that converts the alternating currents induced in the armature to
DC Machines can be either generators or motors. A DC generator converts mechanical power into electrical power, while a DC motor converts electrical power into mechanical power. Both have similar constructions with a stator and rotor separated by an air gap. The rotor contains field windings to produce a magnetic field, while the stator contains armature windings. A commutator and brushes allow current to flow in one direction from the armature to an external circuit. The direction of current induced in the armature windings changes as it rotates, but the commutator switches the connections to maintain unidirectional current output.
This document discusses electrical machines and DC machines. It begins by defining different types of electrical machines including stationary transformers and rotating machines like DC motors, generators, induction motors, and synchronous motors/generators. It then discusses Faraday's law of electromagnetic induction and features that are common to all rotating machines like field and armature windings. DC generators and motors are defined as converting mechanical to electrical energy and vice versa. The construction, working principles, characteristics and commutation process of DC machines are then explained in detail through diagrams and equations.
1. The document discusses synchronous machines, including their construction, types of prime movers, and excitation systems. It describes salient pole and cylindrical rotors, as well as different winding configurations like distributed, integral slot, and fractional windings.
2. Hydro turbines and diesel engines typically drive synchronous machines with salient pole rotors, while steam turbines drive higher speed machines with cylindrical rotors. Excitation systems can be DC, static using thyristors, or brushless.
3. The document provides an overview of synchronous machines and their components.
1) DC machines operate based on the principles that voltage is induced in a conductor moving through a magnetic field (generator action) and a force is induced on a conductor with current in a magnetic field (motor action).
2) The simplest DC machine is a single loop of wire rotating through magnetic poles, which induces a voltage that can be extracted using a commutator and brushes.
3) Real DC machines have more complex windings and commutation systems to produce a DC output and overcome issues like armature reaction.
4) The main types of DC generators - separately excited, shunt, and series - have different characteristics based on how their fields are connected that determine how voltage and current vary with load
- DC generators and motors operate using the principle of electromagnetic induction. When a conductor moves through a magnetic field, an electromotive force (emf) is induced in the conductor.
- The basic components of a DC generator are a magnetic field (produced by poles and field windings) and a conductor (armature) that rotates within the magnetic field. This motion induces an emf in the armature.
- A commutator is used to convert the alternating current from the armature into direct current that can be supplied to a load. Brushes make contact with the commutator segments to carry the output current.
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. A DC machine can operate as either a generator or motor. It converts mechanical power to electrical power as a generator and converts electrical power to mechanical power as a motor.
2. The main components of a DC machine are the stator, rotor, field windings, armature windings, commutator, and brushes. The field windings produce flux and the armature windings, which rotate, cut this flux to generate voltage or consume current depending on if it is operating as a generator or motor.
3. Armature reaction causes the magnetic neutral axis to shift from its ideal position, requiring careful brush placement. Commutation is the process that converts the alternating currents induced in the armature to
DC Machines can be either generators or motors. A DC generator converts mechanical power into electrical power, while a DC motor converts electrical power into mechanical power. Both have similar constructions with a stator and rotor separated by an air gap. The rotor contains field windings to produce a magnetic field, while the stator contains armature windings. A commutator and brushes allow current to flow in one direction from the armature to an external circuit. The direction of current induced in the armature windings changes as it rotates, but the commutator switches the connections to maintain unidirectional current output.
This document discusses electrical machines and DC machines. It begins by defining different types of electrical machines including stationary transformers and rotating machines like DC motors, generators, induction motors, and synchronous motors/generators. It then discusses Faraday's law of electromagnetic induction and features that are common to all rotating machines like field and armature windings. DC generators and motors are defined as converting mechanical to electrical energy and vice versa. The construction, working principles, characteristics and commutation process of DC machines are then explained in detail through diagrams and equations.
1. The document discusses synchronous machines, including their construction, types of prime movers, and excitation systems. It describes salient pole and cylindrical rotors, as well as different winding configurations like distributed, integral slot, and fractional windings.
2. Hydro turbines and diesel engines typically drive synchronous machines with salient pole rotors, while steam turbines drive higher speed machines with cylindrical rotors. Excitation systems can be DC, static using thyristors, or brushless.
3. The document provides an overview of synchronous machines and their components.
1) DC machines operate based on the principles that voltage is induced in a conductor moving through a magnetic field (generator action) and a force is induced on a conductor with current in a magnetic field (motor action).
2) The simplest DC machine is a single loop of wire rotating through magnetic poles, which induces a voltage that can be extracted using a commutator and brushes.
3) Real DC machines have more complex windings and commutation systems to produce a DC output and overcome issues like armature reaction.
4) The main types of DC generators - separately excited, shunt, and series - have different characteristics based on how their fields are connected that determine how voltage and current vary with load
- DC generators and motors operate using the principle of electromagnetic induction. When a conductor moves through a magnetic field, an electromotive force (emf) is induced in the conductor.
- The basic components of a DC generator are a magnetic field (produced by poles and field windings) and a conductor (armature) that rotates within the magnetic field. This motion induces an emf in the armature.
- A commutator is used to convert the alternating current from the armature into direct current that can be supplied to a load. Brushes make contact with the commutator segments to carry the output current.
The document describes the key components and operation of an AC generator. It includes:
- The main components are the field, armature, prime mover, rotor, stator, and slip rings. The rotor and stator can each be the field or armature depending on the generator type.
- In operation, the prime mover rotates the rotor through the stationary field, inducing voltage in the armature windings. Slip rings allow a continuous connection to the rotating armature.
- Losses occur from internal resistance, hysteresis in the iron cores, and mechanical factors like bearing friction. Efficiency is the ratio of output to input power. Generators are rated by voltage, current, power
- DC machines can operate as either generators or motors. A generator produces voltage when its coil rotates through a magnetic field, while a motor produces torque on its coil when current passes through it in a magnetic field.
- The simplest DC machine is a single loop of wire rotating through magnetic poles. Induced voltage and torque depend on flux, speed/current, and construction constants.
- Real DC machines use commutators and brushes to produce DC output from the AC voltage induced in the rotor coils. Problems during commutation like sparking are reduced by techniques like interpoles.
- The internal voltage and torque equations account for flux, speed/current, and construction constants. Power losses include copper, brush,
Alternators operate using the same principles of electromagnetic induction as DC generators but produce an AC output. They have a stationary armature winding (stator) and rotating field windings (rotor). As the rotor spins, the magnetic field cuts the stator conductors, inducing an alternating voltage. This voltage alternates in magnitude and direction as the north and south poles of the rotor pass by. Alternators can have either a rotating field and stationary armature or vice versa. Rotating field designs are commonly used as they allow for simpler construction, higher speeds of operation, and easier insulation of the high voltage stator windings.
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.
The document provides an outline and introduction to DC machines. It discusses the construction and basic parts of DC machines including the stator and rotor. It explains the principle of operation for both DC generators and DC motors. It discusses armature reaction, commutation, and characteristics of DC motors. It also covers the equivalent circuits of DC generators and motors and provides examples of calculating speed and induced emf in DC machines operating as generators and motors.
This document provides an overview of DC machines, including their construction, principles of operation, and characteristics. It discusses DC machines functioning as generators and motors. Key points include:
- DC machines can operate as generators, converting mechanical energy to electrical energy, or motors, converting electrical energy to mechanical energy.
- The main components are the stator (stationary part) and rotor (rotating part).
- In generator operation, relative motion between the magnetic field and armature windings induces an electromotive force (emf) based on Faraday's law of induction.
- In motor operation, current passing through the armature windings in a magnetic field experiences an electromagnetic force based on the left-hand
This document discusses the components and operation of an AC generator. It describes the key parts including the field, armature, prime mover, rotor, stator and slip rings. The field and magnetic flux produce voltage in the armature. The rotor is driven by the prime mover and its rotation through the magnetic field induces current in the armature coils. Slip rings allow current to flow in and out of the rotating component. AC generators have advantages over DC generators for applications such as power generation.
The document discusses the key components of AC generators, including the field, armature, prime mover, rotor, and stator. It explains that the field produces a magnetic flux, the armature produces voltage as this flux cuts through it, and the prime mover provides rotational power. There are two main types of AC generators - those with a stationary field and rotating armature, and those with a rotating field and stationary armature. The rotating field, stationary armature type is commonly used for large power generation.
The document discusses the different types of rotor constructions used in synchronous generators. It describes salient pole and non-salient pole rotors. Salient pole rotors have protruding poles and are used for slower speed applications from 100-1500 RPM. Non-salient pole rotors have flush poles and are used for higher speed turbo generators running at 3600 RPM. The document also discusses different excitation methods for synchronous generators including using slip rings and brushes or a brushless exciter to supply DC current to the rotor field windings. A brushless exciter uses a small AC generator to produce DC for the main generator's field.
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 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 information about AC generators. It begins by defining a generator as a device that converts mechanical energy to electrical energy. It then discusses Faraday's law of electromagnetic induction, which explains how a generator works. The key components of an AC generator are described as the field, armature, and prime mover. The construction and operation of a three-phase synchronous generator is explained, including its stator, rotor, and how speed and frequency relate. Advantages of AC generators include ease of voltage transformation while disadvantages include potential hazards from heat generation.
The document discusses direct current (DC) generators, including their construction, operation, and applications. It describes how a DC generator works by converting mechanical energy to electrical energy using electromagnetic induction. The key components of a DC generator are identified as the yoke, rotor, stator, field electromagnets, armature, commutator, and brushes. Equations for calculating the generated electromotive force (EMF) are also provided. Finally, common applications of DC generators are listed, such as using separately excited generators for speed control and self-excited shunt generators for battery charging.
The document discusses synchronous motors, including their definition, construction, working principle, types, advantages, and applications. Synchronous motors run at a constant synchronous speed determined by the supply frequency, and consist of a stationary stator and rotating rotor. The stator contains three-phase windings powered by AC, while the rotor is excited by DC. The rotor synchronizes with the rotating stator magnetic field. Synchronous motors provide constant speed operation and are used for applications requiring precise speed control or power factor correction.
It the ppt on Dc machines. Dc machines is. A very good ppt. You can learn more about dc machines. Dc machines are important for science dc are machines are also important for science The DC machine can be classified into two types namely DC motors as well as DC generators. Most of the DC machines are equivalent to AC machines because they include AC currents as well as AC voltages in them. The output of the DC machine is DC output because they convert AC voltage to DC voltage. The conversion of this mechanism is known as the commutator, thus these machines are also named as commutating machines. DC machine is most frequently used for a motor. The main benefits of this machine include torque regulation as well as easy speed. The applications of the DC machine is limited to trains, mills, and mines. For example, underground subway cars, as well as trolleys, may utilize DC motors. In the past, automobiles were designed with DC dynamos for charging their batteries.
What is a DC Machine?
A DC machine is an electromechanical energy alteration device. The working principle of a DC machine is when electric current flows through a coil within a magnetic field, and then the magnetic force generates a torque that rotates the dc motor. The DC machines are classified into two types such as DC generator as well as DC motor.
DC Machine
DC Machine
The main function of the DC generator is to convert mechanical power to DC electrical power, whereas a DC motor converts DC power to mechanical power. The AC motor is frequently used in industrial applications for altering electrical energy to mechanical energy. However, a DC motor is applicable where good speed regulation & an ample range of speeds are necessary like in electric-transaction systems.
Construction of DC Machine
The construction of the DC machine can be done using some of the essential parts like Yoke, Pole core & pole shoes, Pole coil & field coil, Armature core, Armature winding otherwise conductor, commutator, brushes & bearings. Some of the parts of the DC machine is discussed below.
Construction of DC Machine
Construction of DC Machine
Yoke
Another name of a yoke is the frame. The main function of the yoke in the machine is to offer mechanical support intended for poles and protects the entire machine from moisture, dust, etc. The materials used in the yoke are designed with cast iron, cast steel otherwise rolled steel.
Pole and Pole Core
The pole of the DC machine is an electromagnet and the field winding is winding among pole. Whenever field winding is energized then the pole gives magnetic flux. The materials used for this are cast steel, cast iron otherwise pole core. It can be built with the annealed steel laminations for reducing the power drop because of the eddy currents.
PCBWay
Pole Shoe
Pole shoe in the DC machine is an extensive part as well as to enlarge the region of the pole. Because of this region, flux can be spread out within the air-gap as well as extra flux can be passed
A synchronous generator or alternator converts mechanical power into alternating current electrical power. It operates at a constant synchronous speed determined by the supply frequency to generate power. The document discusses the basic principles of electromagnetic induction and interaction that enable synchronous machines to convert energy. It describes the constructional features of synchronous machines such as the stator, rotor, and windings. Rotating field systems are preferred over stationary field systems for advantages like easier balancing and cooling of the rotor. Three-phase emfs with 120 degree phase difference can be produced using a three-phase winding displaced by 120 degrees.
This document provides information about an electrical engineering course on basic electrical and instrumentation engineering taught in the even semester of 2017-2018 at Mount Zion College of Engineering and Technology in Puddukkottai, India. It includes an overview and introduction to three-phase induction motors, discussing their construction, principle of operation, rotating magnetic field, and equivalent circuit. Diagrams illustrate motor components like the stator, squirrel cage and wound rotors. The document also covers topics like motor speed, efficiency, torque equation, and provides an introduction to single phase induction motors.
The document describes the key components and operation of an AC generator. It includes:
- The main components are the field, armature, prime mover, rotor, stator, and slip rings. The rotor and stator can each be the field or armature depending on the generator type.
- In operation, the prime mover rotates the rotor through the stationary field, inducing voltage in the armature windings. Slip rings allow a continuous connection to the rotating armature.
- Losses occur from internal resistance, hysteresis in the iron cores, and mechanical factors like bearing friction. Efficiency is the ratio of output to input power. Generators are rated by voltage, current, power
- DC machines can operate as either generators or motors. A generator produces voltage when its coil rotates through a magnetic field, while a motor produces torque on its coil when current passes through it in a magnetic field.
- The simplest DC machine is a single loop of wire rotating through magnetic poles. Induced voltage and torque depend on flux, speed/current, and construction constants.
- Real DC machines use commutators and brushes to produce DC output from the AC voltage induced in the rotor coils. Problems during commutation like sparking are reduced by techniques like interpoles.
- The internal voltage and torque equations account for flux, speed/current, and construction constants. Power losses include copper, brush,
Alternators operate using the same principles of electromagnetic induction as DC generators but produce an AC output. They have a stationary armature winding (stator) and rotating field windings (rotor). As the rotor spins, the magnetic field cuts the stator conductors, inducing an alternating voltage. This voltage alternates in magnitude and direction as the north and south poles of the rotor pass by. Alternators can have either a rotating field and stationary armature or vice versa. Rotating field designs are commonly used as they allow for simpler construction, higher speeds of operation, and easier insulation of the high voltage stator windings.
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.
The document provides an outline and introduction to DC machines. It discusses the construction and basic parts of DC machines including the stator and rotor. It explains the principle of operation for both DC generators and DC motors. It discusses armature reaction, commutation, and characteristics of DC motors. It also covers the equivalent circuits of DC generators and motors and provides examples of calculating speed and induced emf in DC machines operating as generators and motors.
This document provides an overview of DC machines, including their construction, principles of operation, and characteristics. It discusses DC machines functioning as generators and motors. Key points include:
- DC machines can operate as generators, converting mechanical energy to electrical energy, or motors, converting electrical energy to mechanical energy.
- The main components are the stator (stationary part) and rotor (rotating part).
- In generator operation, relative motion between the magnetic field and armature windings induces an electromotive force (emf) based on Faraday's law of induction.
- In motor operation, current passing through the armature windings in a magnetic field experiences an electromagnetic force based on the left-hand
This document discusses the components and operation of an AC generator. It describes the key parts including the field, armature, prime mover, rotor, stator and slip rings. The field and magnetic flux produce voltage in the armature. The rotor is driven by the prime mover and its rotation through the magnetic field induces current in the armature coils. Slip rings allow current to flow in and out of the rotating component. AC generators have advantages over DC generators for applications such as power generation.
The document discusses the key components of AC generators, including the field, armature, prime mover, rotor, and stator. It explains that the field produces a magnetic flux, the armature produces voltage as this flux cuts through it, and the prime mover provides rotational power. There are two main types of AC generators - those with a stationary field and rotating armature, and those with a rotating field and stationary armature. The rotating field, stationary armature type is commonly used for large power generation.
The document discusses the different types of rotor constructions used in synchronous generators. It describes salient pole and non-salient pole rotors. Salient pole rotors have protruding poles and are used for slower speed applications from 100-1500 RPM. Non-salient pole rotors have flush poles and are used for higher speed turbo generators running at 3600 RPM. The document also discusses different excitation methods for synchronous generators including using slip rings and brushes or a brushless exciter to supply DC current to the rotor field windings. A brushless exciter uses a small AC generator to produce DC for the main generator's field.
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 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 information about AC generators. It begins by defining a generator as a device that converts mechanical energy to electrical energy. It then discusses Faraday's law of electromagnetic induction, which explains how a generator works. The key components of an AC generator are described as the field, armature, and prime mover. The construction and operation of a three-phase synchronous generator is explained, including its stator, rotor, and how speed and frequency relate. Advantages of AC generators include ease of voltage transformation while disadvantages include potential hazards from heat generation.
The document discusses direct current (DC) generators, including their construction, operation, and applications. It describes how a DC generator works by converting mechanical energy to electrical energy using electromagnetic induction. The key components of a DC generator are identified as the yoke, rotor, stator, field electromagnets, armature, commutator, and brushes. Equations for calculating the generated electromotive force (EMF) are also provided. Finally, common applications of DC generators are listed, such as using separately excited generators for speed control and self-excited shunt generators for battery charging.
The document discusses synchronous motors, including their definition, construction, working principle, types, advantages, and applications. Synchronous motors run at a constant synchronous speed determined by the supply frequency, and consist of a stationary stator and rotating rotor. The stator contains three-phase windings powered by AC, while the rotor is excited by DC. The rotor synchronizes with the rotating stator magnetic field. Synchronous motors provide constant speed operation and are used for applications requiring precise speed control or power factor correction.
It the ppt on Dc machines. Dc machines is. A very good ppt. You can learn more about dc machines. Dc machines are important for science dc are machines are also important for science The DC machine can be classified into two types namely DC motors as well as DC generators. Most of the DC machines are equivalent to AC machines because they include AC currents as well as AC voltages in them. The output of the DC machine is DC output because they convert AC voltage to DC voltage. The conversion of this mechanism is known as the commutator, thus these machines are also named as commutating machines. DC machine is most frequently used for a motor. The main benefits of this machine include torque regulation as well as easy speed. The applications of the DC machine is limited to trains, mills, and mines. For example, underground subway cars, as well as trolleys, may utilize DC motors. In the past, automobiles were designed with DC dynamos for charging their batteries.
What is a DC Machine?
A DC machine is an electromechanical energy alteration device. The working principle of a DC machine is when electric current flows through a coil within a magnetic field, and then the magnetic force generates a torque that rotates the dc motor. The DC machines are classified into two types such as DC generator as well as DC motor.
DC Machine
DC Machine
The main function of the DC generator is to convert mechanical power to DC electrical power, whereas a DC motor converts DC power to mechanical power. The AC motor is frequently used in industrial applications for altering electrical energy to mechanical energy. However, a DC motor is applicable where good speed regulation & an ample range of speeds are necessary like in electric-transaction systems.
Construction of DC Machine
The construction of the DC machine can be done using some of the essential parts like Yoke, Pole core & pole shoes, Pole coil & field coil, Armature core, Armature winding otherwise conductor, commutator, brushes & bearings. Some of the parts of the DC machine is discussed below.
Construction of DC Machine
Construction of DC Machine
Yoke
Another name of a yoke is the frame. The main function of the yoke in the machine is to offer mechanical support intended for poles and protects the entire machine from moisture, dust, etc. The materials used in the yoke are designed with cast iron, cast steel otherwise rolled steel.
Pole and Pole Core
The pole of the DC machine is an electromagnet and the field winding is winding among pole. Whenever field winding is energized then the pole gives magnetic flux. The materials used for this are cast steel, cast iron otherwise pole core. It can be built with the annealed steel laminations for reducing the power drop because of the eddy currents.
PCBWay
Pole Shoe
Pole shoe in the DC machine is an extensive part as well as to enlarge the region of the pole. Because of this region, flux can be spread out within the air-gap as well as extra flux can be passed
A synchronous generator or alternator converts mechanical power into alternating current electrical power. It operates at a constant synchronous speed determined by the supply frequency to generate power. The document discusses the basic principles of electromagnetic induction and interaction that enable synchronous machines to convert energy. It describes the constructional features of synchronous machines such as the stator, rotor, and windings. Rotating field systems are preferred over stationary field systems for advantages like easier balancing and cooling of the rotor. Three-phase emfs with 120 degree phase difference can be produced using a three-phase winding displaced by 120 degrees.
This document provides information about an electrical engineering course on basic electrical and instrumentation engineering taught in the even semester of 2017-2018 at Mount Zion College of Engineering and Technology in Puddukkottai, India. It includes an overview and introduction to three-phase induction motors, discussing their construction, principle of operation, rotating magnetic field, and equivalent circuit. Diagrams illustrate motor components like the stator, squirrel cage and wound rotors. The document also covers topics like motor speed, efficiency, torque equation, and provides an introduction to single phase induction motors.
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The aim of this project is to provide the complete information of the National and
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2. Synchronous Generators
Outlines of lecture # 1
v Working principles
v Construction details
v How to supply field current?
v Armature winding: Single layer and double layers winding,
full pitched and short-pitched winding,
v Different factors
v Problems solution
3. Working Principles
The working principle of an alternator or
AC generator is similar to the basic working
principle of DC generator. According to the
Faraday's law of electromagnetic induction,
whenever a conductor moves in a magnetic
field EMF gets induced across the
conductor. If close path is provided to the
conductor, induced emf causes current to
flow in the circuit.
Direction of induced current can be given by
Fleming's right hand rule.
4. Construction
Main parts of the alternator, obviously,
consists of stator and rotor. But, the unlike other
machines, in most of the alternators, field
exciters are rotating and the armature coil is
stationary.
Stator: The stator consist of cast-iron frame,
which supports the armature core, having slots
on its inner periphery for housing the armature
conductors. The stator core is made up of
lamination of steel alloys or magnetic iron, to
minimize the eddy current losses.
Rotor: The rotor is like a flywheel having
alternate N and S poles fixed to its outer
rim.
5. Construction
Advantages of Stationary armature:
โข The high voltage output can be directly taken out from
the stationary armature. Whereas, for a rotary armature,
there will be large brush contact drop at higher voltages,
also the sparking at the brush surface will occur.
โข At high voltages, it easier to insulate stationary armature
winding for high ac voltages, which may be as high as 30
kV or more.
โข The sliding contacts i. e. slip-rings are transferred to the
low-voltage, low-power dc field circuit which can,
therefore, be easily insulated.
โข The armature winding can be braced well, so as to
prevent deformation caused by the high centrifugal force.
6. Construction
Rotor: There are two types of rotor used in
an AC generator / alternator:
(i) Salient and (ii) Cylindrical type
(i) Salient pole type: A salient pole is a
magnetic pole that sticks out radially from
the shaft of the rotor. This type of rotor
consists of large number of projected poles
(called salient poles), bolted on a magnetic
wheel. These poles are also laminated to
minimize the eddy current losses.
Alternators featuring this type of rotor are
large in diameters and short in axial length.
Salient pole type rotor is used in low and
medium speed (1200 RPM or less)
alternators.
7. Construction
Rotor: There are two types of rotor used in an AC generator / alternator:
(i) Salient and (ii) Cylindrical type
Cylindrical type: a non-salient pole or cylindrical pole is a magnetic pole with
windings embedded flush with the surface o f the rotor. This type of rotor
consists of a smooth and solid steel cylinder having slots along its outer
periphery. Field windings are placed in these slots. Cylindrical type rotors are
used in high speed alternators, especially in turbo alternators.
windings and armature windings. In general, the term field windings applies to the
windings that produce the main magnetic field in a machine, and the term arma-
ture windings applies to the windings where the main voltage is induced. For syn-
chronous machines, the field windings are on the rotor, so the terms rotor wind- (
ings and field windings are used interchangeably. Sintilarly, the terms stator
windings and armature windings are used interchangeably.
The rotor of a synchronous generator is essentially a large electromagnet. The
magnetic poles on the rotor can be of either salient or nonsalient construction. The
term salient means "protruding" or "sticking out," and a salient pole is a magnetic
pole that sticks out radially from the shaft of the rotor. On the other hand. a nOll-
salientpole is a magnetic pole with windings embedded flush with the surface of the
rotor. A nonsalient-pole rotor is shown in Figure 4-1. Note that the windings of the
electromagnet are embedded in notches on the surface of the rotor. A salient-pole
rotor is shown in Figure 4-2. Note that here the windings of the electromagnet are
wrapped around the pole itself, instead of being embedded in notches on the surface
of the rotor. Nonsalient-pole rotors are normally used for two- and four-pole rotors,
while salient-pole rotors are normally used for rotors with four or more poles.
Because the rotor is subjected to changing magnetic fields, it is constructed
of thin laminations to reduce eddy current losses.
A dc CUlTent must be supplied to the field circuit on the rotor if it is an elec-
tromagnet. Since the rotor is rotating, a special arrangement is required to get the
End View Side View
FIGURE 4-1
A nonsalient two-pole rotor for a synchronous machine.
8. Construction
Rotor: There are two types of rotor used in an AC generator / alternator:
(i) Salient and (ii) Cylindrical type
10. Construction
โข Dumper winding are useful in preventing the hunting in generators.
โข The dumper winding also tends to maintain balanced 3-phase
voltage under unbalanced load conditions.
11. How to supply field current?
There are two common approaches to supplying this dc power:
1. Supply the dc power from an external dc source to the rotor by means
of slip rings and brushes.
2. Supply the dc power from a special dc power source mounted directly
on the shaft of the synchronous generator.
.
Slip rings and brushes
Need regular maintenance: brush
wearied
Significant power loss due to voltage
drop in brush
12. How to supply field current?
Exciter
A brushless exciter is a small ac
generator with its field circuit
mounted on the stator and its
armature circuit mounted on the
rotor shaft. The three-phase output
of the exciter generator is rectified
to direct current by a three-phase
rectifier circuit also mounted on the
shaft of the ( generator, and is then
fed into the main dc field circuit.
13. How to supply field current?
Self-Exciter
To make the excitation of a
generator completely independent of
any external power sources, a small
pilot exciter is often included in the
system. A pilot exciter is a small ac
generator with permanent magnets
mounted on the rotor shaft and a
three-phase winding on the stator. It
produces the power for the field
circuit of the exciter, which in turn
controls the field circuit of the main
machine.
s
o
"
196 ELECTRIC MACHINERY FUNDAMENTALS
1
1
1
Pilot exciter
Pilot exciter
field
Permanent
magnets
Exciter
Exciter armature
:
!
Three-
T phase
rectifier
:
1
+
1 1 1
Synchronous
generator
Main field
I I
I : output
I
I
I
1
1
1
I
1
1
1
1
1
1
Three-
phase
rectifier
Lrvv-v-,.
Pilot exciter
armature
FIGURE 4-5
RF
1
1
Exciter
field
1
1
I
1
1
1
Mum armature
A brushless excitation scheme that includes a pilot exciter. The permanent magnets of the pilot exciter
produce the field current of the exciter, which in turn produces the field current of the main machine.
18. Armature Windings
COIL PITCH : The distance between the two sides of a coil is called the coil span
or coil pitch.
POLE PITCH: The angular distance between the central line of one pole to the
central line of the next pole is called Pole Pitch. A pole pitch always 180 electrical
degrees regardless of the number of poles on the machine.
19. Armature Windings
Full Pitch Coil: A coil having a span equal to 180 electrical degree is called a full
pitch coil as show in fig.
Short Pitch Coil: A coil having a span less than 180 electrical degree is called
Short pitch coil or frictional pitch coil. It is also called chorded coil.
21. Armature Windings
For full pitch coil, ฮฑ = 0 cos( ฮฑ/2 ) = 1 and Kc =1 . for a short pitch
coil Kc < 1.
Coil Span Factor or Pitch factor: Kc is the defined as the
ratio of the voltage generated in short pitch coil to the voltage
generated in full pitch coil. the coil span factor is also called chording
Factor.
28. Synchronous Generators
Outlines of lecture # 2
v Relation between Speed, Frequency, and Pole
v Equation of induced EMF
v Equivalent circuits and phasor diagram of synchronous
machine
v Efficiency and losses
v Power and torque equations
29. Let
P= total number of magnetic poles
N= rotative speed of the rotor in rpm
f= frequency of generated emf in Hz
Since one cycle of emf is produced when a pair of
poles passes past a conductor, the number of cycles
of emf produced in one revolution of the rotor is
equal to the number of pair of poles.
No of cycles/revolution = P/2
No of revolutions/second =N/60
Thus, frequency, f = P/2 X N/60= PN/120 Hz
Relation between Speed, Frequency, and Pole
30. Equation of induced EMF
Let
Z= No. of conductors or coil sides in series/phase
= 2T where T is the no of coils or turns per phase
P= No of poles
f= frequency of induced emf in Hz
ฮฆ= Flux/pole in webers
๐! = ๐๐๐ ๐ก๐๐๐๐ข๐ก๐๐๐ ๐๐๐๐ก๐๐ =
"#$ %&/(
% "#$ &/(
๐)๐๐ ๐* = ๐๐๐ก๐โ ๐๐ ๐๐๐๐ ๐ ๐๐๐ ๐๐๐๐ก๐๐ = ๐๐๐ ๐ผ/2
๐+ = ๐๐๐๐ ๐๐๐๐ก๐๐ = 1.11
N= rotor rpm
39. Equivalent Circuit of a Synchronous Machines
ame equation as the one describing the armature reaction volt-
armature reaction voltage can be modeled as an inductor in
nal generated voltage.
the effects of armature reaction, the stator coils have a self-
sistance. If the stator self-inductance is called LA(and its cor-
e is called XA) while the stator resistance is called RA , then the
ween EAand V. is given by
(4-9)
ion effects and the self-inductance in the machine are both
tances, and it is customary to combine them into a single reac-
nchronous reactance of the machine:
Xs = X + XA (4-10)
equation describing Vยข is
IVยข = EA - jXsIA - RAIA I (4-11)
ible to sketch the equivalent circuit of a three-phase synchro-
e full equivalent circuit of such a generator is shown in
gure shows a de power source supplying the rotor field circuit,
y the coil's inductance and resistance in series. In series with
204 ELECTRIC MACHINERY FUNDAMENTALS
+
V,
FIGURE 4-12
The per-phase equivalent circuit of a synchronous generator. The internal field circuit resistance and
the external variable resistance have been combined into a single resistor RF.
(
Power conversion reversed in motor
Synchronous Generator Synchronous Motor
or
This is exactly the same as the equation for a generator, except that t
current term has been reversed.
40. Equivalent Circuit of a Synchronous Machines
SYNCHRONOUS MOTORS 273
202 ELECTRIC MACHINERY FUNDAMENTALS
lAI
+
jXs RA
EAJ V'I
IF
+
Radj
lA2
RF
jXs
VF
+
EII2 rv V,2
(de)
LF
lA3
+
jXs RA
+
EA3 rv V,3
FIGURE 4-10
The full equivalent circuit of a three-phase synchronous genemtor.
The fact that the three phases of a synchronous generator are identical in
all respects except for phase angle normally leads to the use of a per-phase equiv-
(
Power conversion reversed in motor
Synchronous Generator Synchronous Motor
41.
42. Efficiency and losses
Efficiency
Efficiency of a machine can be defined by
๐ผ =
๐ท๐๐๐
๐ท๐๐
ร๐๐๐%
๐ผ =
๐ท๐๐ โ ๐ท๐๐๐๐
๐ท๐๐
ร๐๐๐%
๐ผ =
๐ท๐๐๐
๐ท๐๐๐ + ๐ท๐๐๐๐
ร๐๐๐%
Losses in AC machines
43. Efficiency and losses
Losses in AC machines
The losses that occur in ac machines can be divided into four basic
categories:
โข Electrical or copper losses (l2R losses)
โข Core losses
โข Mechanical losses
โข Stray losses
44. Efficiency and losses
Losses in AC machines
ELECTRICAL OR COPPER LOSSES: Copper losses are the
resistive heating losses that occur in the stator (armature) and rotor
(field) windings of the machine. The stator copper losses (SCL) in a
three-phase ac machine are given by the equation
๐,-. = 3๐ผ/
(
๐ /
where IA is the current flowing in each armature phase and RA is the
resistance of each armature phase.
The rotor copper losses (RCL) of a synchronous ac machine are
given by
๐0-. = ๐ผ1
(
๐ 1
where IF is the current flowing in the field winding on the rotor and
RF is the resistance of the field winding. The resistance used in these
calculations is usually the winding resistance at normal operating
temperature.
45. Efficiency and losses
Losses in AC machines
CORE LOSSES: The core losses are the hysteresis losses and eddy
current losses occurring in the metal of the motor.
MECHANICAL LOSSES: The mechanical losses in an ac
machine are the losses associated with mechanical effects. There are
two basic types of mechanical losses: friction and windage. Friction
losses are losses caused by the friction of the bearings in the
machine, while windage losses are caused by the friction between
the moving parts of the machine and the air inside the motor's
casing. These losses vary as the cube of the speed of rotation of the
machine.
The mechanical and core losses of a machine are often lumped
together and called the no-load rotational loss of the machine.
46. Efficiency and losses
Losses in AC machines
STRAY LOSSES (OR MISCELLANEOUS LOSSES): Stray
losses are losses that cannot be placed in one of the previous
categories. No matter how carefully losses are accounted for, some
always escape inclusion in one of the above categories. All such
losses are lumped into stray losses. For most machines, stray losses
are taken by convention to be 1 percent of full load.
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