This document describes the components and working principle of a DC generator. It contains the following key points:
1. A DC generator converts mechanical energy to electrical energy through electromagnetic induction. It consists of a magnetic field and a conductor that can move to cut the magnetic flux.
2. The basic components are a magnetic frame, field coils, armature shaft, armature core and windings, commutator, and brushes. The rotating armature windings cut the magnetic flux from the stationary field coils to induce an alternating current.
3. The commutator rectifies the alternating current from the armature to produce a unidirectional current that is collected by the brushes and supplied to the external
A DC motor converts electrical energy into mechanical energy by using the principle of electromagnetic induction. When a current carrying conductor is placed in a magnetic field, it experiences a force that causes it to rotate. In a DC motor, current is passed through stationary conductors located between poles of a magnetic field. This sets up opposing magnetic fields that produce a torque causing the rotor to rotate within the stator. The direction of current flow determines the direction of rotation. By reversing the current direction, the direction of torque and rotation is also reversed, allowing DC motors to run in both forward and reverse directions.
A DC generator converts mechanical energy into electrical energy using the principles of electromagnetic induction. It has two main parts - a stationary stator that produces a magnetic field and a rotating armature.
The stator contains pole cores, pole shoes, and field coils that create the magnetic field when current is passed through the coils. The armature is made of laminated steel and contains conductors that rotate through the magnetic field. This cutting of magnetic flux by the conductors induces an electromotive force (emf) based on Faraday's law of induction.
The induced emf alternates as the conductors pass through different parts of the magnetic field. A commutator is used to rectify the alternating emf
The document provides information about DC generators, including:
1) It describes the basic principles and components of a DC generator, including the field magnet, armature, commutator, and brushes.
2) It discusses armature winding types, the EMF equation, armature reaction, and methods to improve commutation like interpoles and compensating windings.
3) It outlines the characteristics of DC generators like open-circuit characteristics, load characteristics, and efficiency considerations including various loss components.
A DC generator converts mechanical energy to DC electrical energy using electromagnetic induction. It has two main parts - a rotor that rotates within a stator. As the rotor cuts the magnetic field in the stator, an alternating voltage is induced in the rotor windings. A commutator is used to convert the alternating voltage to direct voltage that can be used to power loads. The characteristics of a DC generator include its open circuit characteristic showing the relationship between generated voltage and field current, and its external characteristic showing the relationship between terminal voltage and load current.
- 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,
The document discusses transformers, including their structure, working principle, construction, losses, ideal vs practical characteristics, and applications. A transformer transfers electrical energy between two circuits through electromagnetic induction. It consists of two coils wound around an iron core, with the primary coil connected to an input voltage source and the secondary coil delivering an output voltage. Transformers are used widely in power transmission and distribution to change voltage levels for efficient transmission or usage.
The document summarizes the key components and working principle of an AC generator. The AC generator converts mechanical energy to electrical energy through electromagnetic induction. It has a field magnet that produces a magnetic field, an armature coil that rotates in this field, slip rings to carry the alternating current produced, and brushes to transfer the current to an external circuit. As the coil rotates, the changing magnetic flux induces an alternating current whose frequency depends on the rotation speed.
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
A DC motor converts electrical energy into mechanical energy by using the principle of electromagnetic induction. When a current carrying conductor is placed in a magnetic field, it experiences a force that causes it to rotate. In a DC motor, current is passed through stationary conductors located between poles of a magnetic field. This sets up opposing magnetic fields that produce a torque causing the rotor to rotate within the stator. The direction of current flow determines the direction of rotation. By reversing the current direction, the direction of torque and rotation is also reversed, allowing DC motors to run in both forward and reverse directions.
A DC generator converts mechanical energy into electrical energy using the principles of electromagnetic induction. It has two main parts - a stationary stator that produces a magnetic field and a rotating armature.
The stator contains pole cores, pole shoes, and field coils that create the magnetic field when current is passed through the coils. The armature is made of laminated steel and contains conductors that rotate through the magnetic field. This cutting of magnetic flux by the conductors induces an electromotive force (emf) based on Faraday's law of induction.
The induced emf alternates as the conductors pass through different parts of the magnetic field. A commutator is used to rectify the alternating emf
The document provides information about DC generators, including:
1) It describes the basic principles and components of a DC generator, including the field magnet, armature, commutator, and brushes.
2) It discusses armature winding types, the EMF equation, armature reaction, and methods to improve commutation like interpoles and compensating windings.
3) It outlines the characteristics of DC generators like open-circuit characteristics, load characteristics, and efficiency considerations including various loss components.
A DC generator converts mechanical energy to DC electrical energy using electromagnetic induction. It has two main parts - a rotor that rotates within a stator. As the rotor cuts the magnetic field in the stator, an alternating voltage is induced in the rotor windings. A commutator is used to convert the alternating voltage to direct voltage that can be used to power loads. The characteristics of a DC generator include its open circuit characteristic showing the relationship between generated voltage and field current, and its external characteristic showing the relationship between terminal voltage and load current.
- 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,
The document discusses transformers, including their structure, working principle, construction, losses, ideal vs practical characteristics, and applications. A transformer transfers electrical energy between two circuits through electromagnetic induction. It consists of two coils wound around an iron core, with the primary coil connected to an input voltage source and the secondary coil delivering an output voltage. Transformers are used widely in power transmission and distribution to change voltage levels for efficient transmission or usage.
The document summarizes the key components and working principle of an AC generator. The AC generator converts mechanical energy to electrical energy through electromagnetic induction. It has a field magnet that produces a magnetic field, an armature coil that rotates in this field, slip rings to carry the alternating current produced, and brushes to transfer the current to an external circuit. As the coil rotates, the changing magnetic flux induces an alternating current whose frequency depends on the rotation speed.
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 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 discusses the construction and working of transformers. It describes transformers as devices that change AC electric power from one voltage level to another through magnetic induction between two coils. The key components of a transformer are the magnetic core and windings. Transformers have either a core type or shell type construction. Core type transformers have cylindrical coils wound around a single core, while shell type transformers have multilayer coils wound around a central limb with the core encircling the coils. Shell type construction is typically used for high voltage transformers.
This document provides an overview of different types of electrical machines including DC machines, synchronous machines, induction machines, and transformers. It begins with the basic construction and operating principles of electrical machines, explaining how they can convert between mechanical and electrical energy. It then discusses DC machines in more detail, covering the construction and working principles of DC generators and DC motors. The document also discusses various types of DC generators including separately excited, self-excited, shunt, series and compound wound generators. Speed control methods for DC motors are also summarized.
- 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.
This document discusses DC generators and their components and operation. It describes:
1) The basic components of a DC generator including the armature, electromagnet, slip rings, and brushes.
2) How a DC generator works by inducing an electromotive force (emf) in the armature coils as they cut through the magnetic field.
3) Issues that can occur with commutation in DC generators and different methods to improve commutation such as using resistance or interpole commutation.
1. The document discusses the objectives, working principles, and types of DC motors. It describes brushed and brushless DC motors.
2. Key components of DC motors are described in detail, including the field structure, armature, commutator, brushes, yoke, poles, field and armature windings.
3. The document explains how electrical energy is converted to mechanical energy in a DC motor through electromagnetic interactions between the magnetic fields set up in the stationary and rotating components by currents.
direct current machine theory detial for undergraduate levelssuser4c4e76
This document discusses the principles and construction of DC generators. It begins by explaining the basic principle of electromagnetic induction and how a voltage is generated by relative motion between a conductor and magnetic flux. It then describes the components of a basic DC generator, including the armature winding, field winding, commutator, and brushes. Different types of armature windings like lap and wave windings are explained. Key terms related to armature windings like pole pitch, coil span, and various pitches are defined. The document concludes by providing details on the construction of a DC machine and labeling its main parts.
This document discusses the construction and working of transformers. It begins with an introduction that defines a transformer as a device that changes AC electric power at one voltage level to another through magnetic coupling of two coils. It then covers the main topics of the structure and working principle of transformers, the different types of constructions including core and shell types, losses in transformers including copper, hysteresis and eddy current losses, the differences between ideal and practical transformers, and applications such as in transmission and distribution of power.
This document provides an overview of transformers, including their structure, working principle, construction, losses, and applications. Transformers are devices that change AC electric power at one voltage level to another through magnetic coupling of two coils. They allow interchange of electric energy between circuits without a direct connection. The transformer consists of a primary coil, secondary coil, and magnetic core. When an alternating current flows through the primary, it induces a changing magnetic flux that is transferred to the secondary coil to induce voltage. Transformers experience losses from copper, hysteresis, and eddy currents. They are used widely in power transmission and applications like televisions and cameras.
The document discusses armature reaction and commutation in DC machines. It describes how armature reaction demagnetizes and distorts the main magnetic field, requiring brush shift. Commutation involves the reversal of current in armature coils as they pass between poles. Sparking can occur due to reactance voltage impeding quick current reversal. Methods to improve commutation include resistance commutation using carbon brushes and EMF commutation using interpoles to neutralize reactance voltage.
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.
1. An electrical machine that converts mechanical energy to electrical energy is called a generator, while one that converts electrical to mechanical is called a motor.
2. Generators operate based on Faraday's law of induction - a changing magnetic flux induces an electromotive force (emf) in any conductor within it. In a DC generator, the armature coils rotate within a stationary magnetic field, inducing an AC emf that is rectified into DC via the commutator.
3. The document then discusses the components, construction, winding types, EMF equation and excitation methods of DC generators. Key components include the yoke, poles, field winding, armature and commutator. Generators can be separately or self
1. An electrical machine that converts mechanical energy to electrical energy is called a generator, while one that converts electrical to mechanical is called a motor.
2. Generators operate based on Faraday's law of induction - a changing magnetic flux induces an electromotive force (emf) in any conductor within it. In a DC generator, the armature coils cut the magnetic flux from stationary field poles to generate an alternating emf that is rectified into direct current using a commutator.
3. The speed of the armature rotation determines the frequency of the induced alternating emf, while the number of field poles and magnetic flux strength set the output voltage level according to the generator equation. Proper excitation of the field
The document summarizes key aspects of DC machines, including:
1) DC machines convert mechanical energy to DC electric energy (generators) or convert DC electric energy to mechanical energy (motors).
2) They contain a commutator that converts internally generated AC to DC at the terminals.
3) Construction includes a yoke, poles, field windings, armature, commutator, and brushes.
4) Armature reaction distorts the magnetic field and weakens it as load increases. Commutation reverses current in coils as they pass the magnetic neutral axis.
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.
Transformers transfer electrical energy between two circuits through electromagnetic induction. A varying current in the primary winding produces a varying magnetic field that induces a voltage in the secondary winding. Transformers are used to increase or decrease alternating voltages for power transmission and utilization. They work on Faraday's law of induction and have no moving parts. A transformer consists of primary and secondary coils wound around a laminated iron core to maximize flux linkage between the coils.
Armature reaction is the distortion of the magnetic field in a DC generator caused by the magnetic field produced by current in the armature. This reaction shifts the neutral plane and affects commutation. It can reduce the induced EMF and torque. Methods to reduce armature reaction include using poles with high reluctance at the tips, laminated pole shoes, reducing armature flux through field pole laminations, having a strong main magnetic field, using interpoles, and adding compensating windings.
The document describes different types of circuit breakers including air blast circuit breakers, oil circuit breakers, SF6 circuit breakers, and vacuum circuit breakers. It provides details on their construction, working principles, advantages, and disadvantages. Air blast circuit breakers use compressed air to extinguish arcs, while oil circuit breakers absorb arc energy through oil decomposition. SF6 circuit breakers have very short arcing times due to SF6's arc quenching properties. Vacuum circuit breakers interrupt current at the first current zero using a vacuum as the arc quenching medium.
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 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 discusses the construction and working of transformers. It describes transformers as devices that change AC electric power from one voltage level to another through magnetic induction between two coils. The key components of a transformer are the magnetic core and windings. Transformers have either a core type or shell type construction. Core type transformers have cylindrical coils wound around a single core, while shell type transformers have multilayer coils wound around a central limb with the core encircling the coils. Shell type construction is typically used for high voltage transformers.
This document provides an overview of different types of electrical machines including DC machines, synchronous machines, induction machines, and transformers. It begins with the basic construction and operating principles of electrical machines, explaining how they can convert between mechanical and electrical energy. It then discusses DC machines in more detail, covering the construction and working principles of DC generators and DC motors. The document also discusses various types of DC generators including separately excited, self-excited, shunt, series and compound wound generators. Speed control methods for DC motors are also summarized.
- 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.
This document discusses DC generators and their components and operation. It describes:
1) The basic components of a DC generator including the armature, electromagnet, slip rings, and brushes.
2) How a DC generator works by inducing an electromotive force (emf) in the armature coils as they cut through the magnetic field.
3) Issues that can occur with commutation in DC generators and different methods to improve commutation such as using resistance or interpole commutation.
1. The document discusses the objectives, working principles, and types of DC motors. It describes brushed and brushless DC motors.
2. Key components of DC motors are described in detail, including the field structure, armature, commutator, brushes, yoke, poles, field and armature windings.
3. The document explains how electrical energy is converted to mechanical energy in a DC motor through electromagnetic interactions between the magnetic fields set up in the stationary and rotating components by currents.
direct current machine theory detial for undergraduate levelssuser4c4e76
This document discusses the principles and construction of DC generators. It begins by explaining the basic principle of electromagnetic induction and how a voltage is generated by relative motion between a conductor and magnetic flux. It then describes the components of a basic DC generator, including the armature winding, field winding, commutator, and brushes. Different types of armature windings like lap and wave windings are explained. Key terms related to armature windings like pole pitch, coil span, and various pitches are defined. The document concludes by providing details on the construction of a DC machine and labeling its main parts.
This document discusses the construction and working of transformers. It begins with an introduction that defines a transformer as a device that changes AC electric power at one voltage level to another through magnetic coupling of two coils. It then covers the main topics of the structure and working principle of transformers, the different types of constructions including core and shell types, losses in transformers including copper, hysteresis and eddy current losses, the differences between ideal and practical transformers, and applications such as in transmission and distribution of power.
This document provides an overview of transformers, including their structure, working principle, construction, losses, and applications. Transformers are devices that change AC electric power at one voltage level to another through magnetic coupling of two coils. They allow interchange of electric energy between circuits without a direct connection. The transformer consists of a primary coil, secondary coil, and magnetic core. When an alternating current flows through the primary, it induces a changing magnetic flux that is transferred to the secondary coil to induce voltage. Transformers experience losses from copper, hysteresis, and eddy currents. They are used widely in power transmission and applications like televisions and cameras.
The document discusses armature reaction and commutation in DC machines. It describes how armature reaction demagnetizes and distorts the main magnetic field, requiring brush shift. Commutation involves the reversal of current in armature coils as they pass between poles. Sparking can occur due to reactance voltage impeding quick current reversal. Methods to improve commutation include resistance commutation using carbon brushes and EMF commutation using interpoles to neutralize reactance voltage.
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.
1. An electrical machine that converts mechanical energy to electrical energy is called a generator, while one that converts electrical to mechanical is called a motor.
2. Generators operate based on Faraday's law of induction - a changing magnetic flux induces an electromotive force (emf) in any conductor within it. In a DC generator, the armature coils rotate within a stationary magnetic field, inducing an AC emf that is rectified into DC via the commutator.
3. The document then discusses the components, construction, winding types, EMF equation and excitation methods of DC generators. Key components include the yoke, poles, field winding, armature and commutator. Generators can be separately or self
1. An electrical machine that converts mechanical energy to electrical energy is called a generator, while one that converts electrical to mechanical is called a motor.
2. Generators operate based on Faraday's law of induction - a changing magnetic flux induces an electromotive force (emf) in any conductor within it. In a DC generator, the armature coils cut the magnetic flux from stationary field poles to generate an alternating emf that is rectified into direct current using a commutator.
3. The speed of the armature rotation determines the frequency of the induced alternating emf, while the number of field poles and magnetic flux strength set the output voltage level according to the generator equation. Proper excitation of the field
The document summarizes key aspects of DC machines, including:
1) DC machines convert mechanical energy to DC electric energy (generators) or convert DC electric energy to mechanical energy (motors).
2) They contain a commutator that converts internally generated AC to DC at the terminals.
3) Construction includes a yoke, poles, field windings, armature, commutator, and brushes.
4) Armature reaction distorts the magnetic field and weakens it as load increases. Commutation reverses current in coils as they pass the magnetic neutral axis.
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.
Transformers transfer electrical energy between two circuits through electromagnetic induction. A varying current in the primary winding produces a varying magnetic field that induces a voltage in the secondary winding. Transformers are used to increase or decrease alternating voltages for power transmission and utilization. They work on Faraday's law of induction and have no moving parts. A transformer consists of primary and secondary coils wound around a laminated iron core to maximize flux linkage between the coils.
Armature reaction is the distortion of the magnetic field in a DC generator caused by the magnetic field produced by current in the armature. This reaction shifts the neutral plane and affects commutation. It can reduce the induced EMF and torque. Methods to reduce armature reaction include using poles with high reluctance at the tips, laminated pole shoes, reducing armature flux through field pole laminations, having a strong main magnetic field, using interpoles, and adding compensating windings.
The document describes different types of circuit breakers including air blast circuit breakers, oil circuit breakers, SF6 circuit breakers, and vacuum circuit breakers. It provides details on their construction, working principles, advantages, and disadvantages. Air blast circuit breakers use compressed air to extinguish arcs, while oil circuit breakers absorb arc energy through oil decomposition. SF6 circuit breakers have very short arcing times due to SF6's arc quenching properties. Vacuum circuit breakers interrupt current at the first current zero using a vacuum as the arc quenching medium.
This document outlines a technical seminar presentation on the effect of new Internet of Things (IoT) features on security and privacy. It discusses various IoT features like interdependence, constrained resources, unattended operation, mobility, ubiquity, intimacy with devices, and the myriad of devices and data. It analyzes research on security threats in different IoT application scenarios and years. The document also covers advantages and disadvantages of IoT, examples applications, and concludes by summarizing threats, challenges and opportunities of each discussed IoT feature.
1) Synchronous machines are AC rotating machines whose speed is proportional to the frequency of the current in the armature. They are commonly used as generators in power grids.
2) A synchronous generator has a rotor that is excited by DC current to produce a rotating magnetic field. The rotation of this field induces AC voltage in the stationary stator windings.
3) Synchronous machines have high operating efficiency, reliability, and allow control of power factor, making them well-suited for large power generation applications like power plants.
This document provides an overview of occupational health and safety topics including hazards, safe working practices, emergencies, first aid procedures, and documentation. It covers various types of hazards like physical, chemical, mechanical, electrical hazards. It describes safe working practices, use of personal protective equipment, safe material handling, classification of fires and use of fire extinguishers. The document demonstrates how to deal with emergency situations, provide first aid for bleeding, wounds, burns, choking, and perform CPR. It also shows how to move injured people correctly during an emergency.
This document provides information about different types of electric motors, including:
- AC induction motors, which are the most common type used in industry. They have a simple design and are inexpensive to maintain.
- AC synchronous motors, which run at a constant speed determined by the frequency of the power supply. They are used where power factor improvement is needed.
- Single phase AC motors like shaded-pole, split-phase, and capacitor-start motors, which are used in household appliances. These motors require additional components to generate a rotating magnetic field for starting.
- DC motors that have different winding configurations determining their speed and torque characteristics, like series-wound, shunt-wound,
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 an overview of DC machines, including DC motors and DC generators. It discusses:
- The basic components and construction of DC machines, including the stator, rotor, field winding, armature winding, commutator, and brushes.
- The fundamentals of how DC machines operate based on electromagnetic induction principles of generator and motor action.
- The equivalent circuits used to model DC machines, representing the armature and field circuits.
- Different types of DC motors like separately excited, shunt, series, and compound motors.
- Factors that determine the speed of DC motors like armature voltage, current, and magnetic flux.
- Examples calculating voltages,
The document discusses various topics related to DC machines including Maxwell's corkscrew rule, Fleming's left-hand and right-hand rules, Lenz's law, the construction and working principles of DC generators and motors. It describes the field system, armature, commutator, brushes, and winding types. It also covers EMF equations, characteristics, speed control methods, losses, testing, and applications of DC generators and motors.
The document summarizes new challenges facing electricity distribution and regulation in India. Key challenges include high costs from past capacity additions, financial losses for distribution companies, high transmission and distribution losses, poor supply quality, grid integration of renewables, and safety issues. Suggested solutions discussed include avoiding long-term coal contracts, encouraging large consumer migration to open access, promoting efficiency, deploying agricultural solar feeders, rationalizing tariffs, and increasing professional participation in policy processes.
1. DC Generator
Generator Principle
An electrical generator is a machine, which converts mechanical
energy (or power) into electrical energy (or power).
The energy conversion in a generator from mechanical energy to
electrical energy is based on the principle of the production of
dynamically induced electromotive force (e.m.f).
Whenever a conductor cuts magnetic flux, dynamically induced e.m.f
is produced in it according to Faraday’s Laws of Electromagnetic
Induction.
This e.m.f causes a current to flow if the conductor circuit is closed.
Hence, two basic essential parts of an electrical generator are:
(a) A magnetic field, and
(b) A conductor or conductors, which can so move as to cut
the flux.
2. Simple Loop generator
Construction:
A single-turn rectangular copper coil
ABCD, as shown in Fig. 24.1a,
rotating about its own axis in a
magnetic field provided by either
permanent magnets or
electromagnets.
Two collecting brushes (of carbon or copper) press against the slip-
rings.
Their function to collect current induced in the coil and to convey it to
the external load resistance R.
The rotating coil may be called “armature” and the magnets as “field
magnets”.
The two end of the coil are joined to
slip-rings ‘a’ and ‘b’ which are
insulated from each other and from
the central shaft.
3. Working Principle
The coil sides AB and CD now represent by A and B
as shown in Fig.2.9. Imagine the coil to be rotating
in clock-wise direction.
When the coil sides A and B are at position 1, the
plane of the coil is at right angles to line of flux,
the flux linked with the coil is maximum but rate of
change of flux linkages is minimum.
As the coil continues rotating further, the rate of change of flux
linkages (and hence induced e.m.f in it) increases, till the angle
equals 90o.
It is so because in this position, the coil sides A
and B do not cut or share the flux, rather the slide
along them i.e. they move parallel to the lines of
flux. Hence there is no induced e.m.f in the coil.
4. At position 2, the voltage induced
in the coil is at a maximum
because the conductors are moving
at right angles to the lines of flux.
In this position, the coil plane is horizontal i.e.
parallel to the lines of flux. As seen, the flux
linked with the coil is minimum but rate of change
of flux linkages is maximum. Hence maximum
e.m.f is induced in the coil when in this position 2.
The direction of current in the coil can be obtained in accordance with
Feming’s right-hand rule.
In the next quarter revolution i.e. from 90o to 180o, the flux linked with
the coil gradually increases but the rate of change of flux linkages
decreases.
Hence, the induced e.m.f decreases gradually, the angles equals 180o (it
is reduced to zero value).
5. The voltage is again zero at position 3, just as it was
at position 1.
Coil side A is now at the bottom instead of at the top.
We find the first half revolution of the coil, no
e.m.f is induced in it when in position 1,
maximum when in position 2 and no e.m.f when
in position 3 in this half revolution the coil sides
A and B are moved in downward.
In the next half revolution i.e. from 180o to 360o,
the variations in the magnitude of e.m.f. are
similar to those in the first half revolution.
6. The e.m.f value is maximum when coil is in position 4 and
minimum when in position 5 (or 1).
The direction of current is opposite of the current which is found
for the first revolution.
Due to the direction of motion (upward direction) the current
direction is changed in the next half revolution.
7. Unidirectional Current Generation
We find that the current which is obtained from a simple generator
reverses its direction after every half revolution.
Such a current undergoing periodic reversals is known as alternating
current.
For making the flow of current
unidirectional in the external circuit, the
slip-rings are replaced by split-rings (or
commutator) as shown in (a).
The ends of the coil are connected through the split-ring to the
brushes which lead to the external circuit.
The split-rings are made out of a
conducting cylinder which is cut into
two halves or segments insulated from
each other by a thin sheet of mica or
some other insulating material.
8. Previous Fig. (a) can simply be drawn as Fig. 2.10.
While the coil moves from position 1 to position 2, the brushes
remain in contact with the split-ring segments and the current
direction remains as indicated although the magnitude decreases.
At position 2 the voltage
induced in the coil is zero,
and the current in the
external circuit is also zero.
At this instant segment A leaves brush 1 and makes connect with brush
2. Segment B leaves brush 2 and makes contact with brush 1.
As the coil moves from position 2 to position 3, segment A makes
contact with brush 2 only, while the current increases from zero and
leaves brush 2.
Of course, during this same period current returns to the coil through
brush 1 and segment B.
9. Again, when the current in the coil becomes zero, the segment in
contact with the brush changes, thereby maintaining a unidirectional
current in the external circuit.
This follows from the fact that wire 1 is always connected to the coil
side under the North Pole, while coil 2 is always connected to the coil
side under the South Pole.
1
2
Even now the current induced in the coil sides is alternating as before.
It is only due to the rectifying action of the split-rings (also called
commutator) that is becomes unidirectional in the external circuit.
Hence, it should be clearly understood that even the armature of DC
generator, the induced voltage is alternating.
10. Fig. 5 shows a cross-section of a
typical commercial DC
generator, simplified for
emphasis of the major portions.
The basic principle underlying
construction and working of an
actual generator which consists
of the following essential parts:
1. Magnetic Frame or Yoke,
2. Pole Coils or Field Coils,
3. Pole-Cores and Pole-Shoes,
4. Interpole (Commutating Pole)
5. Compensating Winding
6. Armature or Rotor Shaft
7. Armature Core,
8. Armature Windings or Conductors,
9. Commutator,
10. Brushes and Brush Rigging, and
11. Bearing
Practical Generator
11. Magnetic Frame or Yoke
Yokes are made of cast iron or cast steel or rolled steel.
The outer frame or yoke serves double purpose:
1. It provides mechanical support for the poles and acts as a
protecting cover for the whole machine, and
2. It carries the magnetic flux produced by the poles.
Pole Coils or Field Coils
To produce the flux line by means of an electromagnetic, a voltage
have to be supplied through a coil.
A coil consisting of many turns of fine wire is generally wound
around the core.
This coil is called shunt field.
Also around the core may be found a few turns of heavy wire.
This is called the series field.
These coils produce the magnotomotive force required to yield the
necessary flux cut by the rotating conductors.
12. Pole-Cores and Pole-Shoes
The field magnets consist of pole cores and pole shoes.
The core of the pole is built up of laminated steel and the shoe of pole
is curved to produce a more uniform magnetic field.
The pole shoes serve the following
purposes:
1. They spread out the flux in the air gap
and also, being of larger cross-section,
reduce the reluctance of the magnetic path,
and
2. They support the exciting coils (or field
coils)
13. Interpole
The interpole and its winding are mounted on the yoke of
the dynamo.
These are located in the interpolar region between the main
poles and are generally smaller in size.
The interpole winding is composed of a few turns of heavy
wire.
Since it is connected in series with the armature circuit so
that its magnotomotive force (mmf) is proportional to the
armature current.
Compensating Winding
Compensating windings are optional.
They are connected in the same manner at the interpole
windings but are located in axial slots of the field shoes.
14. Armature Shaft
The moving part of the DC generator is called the armature.
The armature consists of a shaft upon which all parts are mounted.
The armature shaft, which imparts rotation to the armature core,
winding, and commutator.
Armature Windings or Conductors
The armature winding are usually former-wound.
These are first wound in the form of flat rectangular coils and are
then pulled into their proper shape in a coil puller.
The conductors are placed in the armature slots which are lined with
tough insulating material.
15. Armature Core
The material surrounding the shaft is laminated sheet steel and is
called the armature core.
This magnetic material is necessary to provide a path of low
reluctance to the line of flux from the poles.
The laminations are required to reduce the eddy current due to the
change of flux in the core.
Each junction point between coils is connected to a commutator.
The commutator segments are insulated from each other and the
shaft.
The segments form a ring around the shaft of the armature.
The armature serves the following functions:
1. It provides a low-reluctance path for the flux,
2. It holds the coils, and
3. It produces motion so that the coils can cut the flux.
16. Commutator
The function of commutator is to facilitate collection of
current from the armature conductors.
It rectifies i.e. converts the alternating current induced in
the armature conductors into unidirectional current in the
external load circuit.
The segments of commutator are insulated from each other
by thin layers of mica.
The number of segments is equal to the number of armature
coils.
Each commutator segments is connected to the armature
conductor by means of a copper lug or strip (or riser).
17. Brushes and Brush Rigging
The brushes are made to bear down on the commutator by a spring
whose tension can be adjusted by changing the position of lever in the
notches.
A flexible copper pigtail (the current is taken from the brush by
means of a flexible copper wire embedded in the brush, called the
pigtail) mounted at the top of the brush conveys current from the
brushes to the holder.
The brushes, whose function is to
collect current from commutator, are
usually made of carbon or graphite
and are in the shape of a rectangular
block and supported from the stator
structure by a rigging.
These brushes are housed in brush-
holders usually of the box-type
variety.
18. Bearings
The armature is supported at each end by a metal
framework called end bells.
The end bells contain the bearings in which the armature
rotate.
One end bell is left open or made with a cover that can be
removed to inspect the brushes.
The open end bell also aids in the natural cooling of the
generator.
Because of their reliability, ball-bearings are frequently
employed though for heavy duties, roller bearings are
preferable.
19. Cutaway view
of a dc
machine.
Rotor of a dc
machine
DC machine stator with poles visible.
20. Armature Windings
Coil: One or more turns of wire grouped together
and mounted on the drum wound armature in
order to cut lines of flux as shown in Fig. 4.1.
Coil side: Any side of coil that cuts lines of flux.
Winding Element: The side of coil is called a winding element.
Obviously, the number of winding elements is twice the number of
coils.
Conductor (or inductor): The length of a wire lying in the magnetic
field and in which an e.m.f. is induced, is called conductor (or
inductor).
Winding: The complete connection and location of all the coils on the
armature.
Pitch: A method of measurement. The pitch is measured as the unit of
coil sides, slots and commutator segments.
21. Front End Connection: A wire that
connects the end of a coil to a commutator
segment. This wire is located at that part
of the coil that is nearest the commutator.
Back End Connection: A wire or conductor that connects an inductor
on one side of the coil to an inductor on the other side of the coil. It is
on the end opposite to the commutator.
Pole Pitch: It may be variously defined as:
(a) The distance between identical points on adjacent poles i.e.
the periphery of the armature divided by the number of poles of the
generator.
(b) It is equal to the number of armature conductors (or
armature slots) per pole.
Coil Span or Coil Pitch (Ys): It is the distance, measured in terms of
armature slots (or armature conductors) between two sides of a coil.
It is, in fact, the periphery of the armature spanned by the two sides of
the coil.
22. Full-Pitched: If the coil pitch is equal to pole pitch, then winding is
called full-pitched.
It means that coil span is 180o electrical degrees.
In this case, the coil sides lie under opposite poles, hence the induced
e.m.f.s in them are additive.
Therefore, maximum e.m.f. is induced in the two coil sides.
Fractional Pitched: If the coil span is less than the pole pitch, then
the winding is called fractional-pitched.
In this case, there is a phase difference between the e.m.f.s in the two
sides of the coil.
Hence, the total e.m.f. round the coil, which is the vector sum of
e.m.f.s in the two sides, is less in this case as compared to that in the
full-pitched case.
Fractional-pitched windings are purposely used to effect substantial
saving in the copper of the end connections and for improving
commutation.
An armature wound with a fractional pitch is called a chorded
winding.
23. Back Pitch (YB): The number of
coil sides or slots spanned by the
back end connections.
Front Pitch (YF): The number
of coil sides or slots spanned by
the front end connections.
Both front and back pitches for
lab and wave winding are shown
in Fig. 24.25 and Fig. 24.26.
Pitch of Winding (Y) or Resultant Pitch (YR): It is the distance
between the beginning of one coil and the beginning of the next coil to
which it is connected.
Commutator Pitch (YC): The number of commutator segments spanned
from one end of a coil to the other end of the same coil.
From Fig.24.25 and 24.26 it is clear that for lap winding, YC is the
difference of YB and YF whereas for wave winding it is sum of YB and YF.
24. Single-Layer Winding: It is that
winding which one conductor or coil
side is placed in each armature slot.
Such a winding is not much used.
Two-Layer Winding: In this type of
winding, there are two conductors or
coil sides per slot arranges in two layers.
Usually, one side of every coil lies in the
upper half of one slot and other side lies in
the lower of half of some other slot at a
distance of approximately one pitch away.
The transfer of the coil from one slot to
another is usually made in a radial plane by
means of a particular bend or twist at the
back end.
The coil sides lying at the upper half of the
slots are numbered odd i.e. 1, 3, 5, 7, etc.
while those at lower half are numbered
even i.e. 2, 4, 6, 8, etc.
25. Degree of Reentrancy of an Armature Winding
A winding said to be singly re-entrant if on tracing through it once, all
armature conductors are included on returning to the staring point.
It is doubly reentrant if only half the conductors are included in tracing
through the winding once and so on.
Multiplex Winding
If there is only one set of closed winding, it is called simplex
winding.
If there are two such windings on the same armature, it is called
duplex winding and so on.
The multiplicity affects a number of parallel paths in the armature.
For a give armature slots and coils, as the multiplicity increases, the
number of parallel paths in the armature increases thereby increasing
the current rating but decreasing the voltage rating.
26. Two types of end connections of windings
are employed, namely, the lap-wound
and wave-wound connections as shown
in Fig. 24.25 and 24.26.
Each winding can be arranged
progressively or retrogressively and
connected in simplex, duplex and
triplex.
The following rules, however, applying to
both types of the winding:
Lap and Wave Windings
(a) The front pitch and back pitch are each approximately equal to the pole-pitch i.e.
windings should be full pitched.
This results in increased e.m.f. round the coils. For special purposes fractional
pitched windings are deliberately used.
(b) Both pitches should be odd; otherwise it would be difficult to place the coils
properly on the armature.
(c) The number of commutator segments is equal to the number of slots or coils (or
half the number of conductors) because the front ends of the conductors are
joined to the segments in pairs.
(d) The winding must close upon itself.
27. The number of parallel path of wave winding does not depend on the number of
pole but the number of parallel path of lap winding depends on number of pole.
Each of the two parallel paths of wave winding contains conductor lying under
all the poles whereas in lap winding, each of the parallel paths contains
conductors which lies under one pair of poles.
So, for a given number of poles and armature conductors, the wave winding
gives more e.m.f. than the lap winding. Conversely, for the same e.m.f. lap
winding would require large number of conductors which will result in higher
winding cost and less efficient utilization of space in the armature slots.
Hence, means wave winding is suitable for comparatively low-current but high
voltage generators because it gives smaller parallel paths.
And, lap winding is suitable for comparatively low-voltage but high current
generators because it gives more parallel paths.
In wave winding, equalizing connections are not necessary whereas in a lap
winding they definitely are.
Any inequality of pole fluxes affects two paths equally; hence their induced
e.m.f.s are equal.
In lap-wound armatures, unequal voltages are produced which set up a
circulating current that produces sparking at brushes.
Uses of Lap and Wave Winding