The document discusses DC motors and why they are still used despite being invented in the 19th century before AC induction motors. DC motors can operate at variable speeds by adjusting voltage, allowing control of speed and torque. They can produce full torque from zero to base speed, making them suitable for applications like conveyors and cranes that require starting under load. While AC inverters now allow variable speed control of AC motors, DC motors are still used for their inherent speed control characteristics and suitability for constant torque loads.
Electric motors are used in a wide variety of applications, from tiny motors in watches to large motors powering ships. There are many different types of electric motors that each have unique characteristics making some better suited for certain applications than others. Some common applications of electric motors include power tools like electric screwdrivers, appliances like water pumps and air compressors, automatic door systems, ventilation systems, air cooling systems, electric vehicles like bicycles, ATVs, and cars, as well as industrial uses such as conveyor systems and electric trains.
SYNCHRONOUS MOTOR STARTING METHODS, START करने के METHODS|DAMPER WINDING, AUX...Prasant Kumar
This document discusses different starting methods for synchronous motors. It describes using an auxiliary induction motor or DC motor to bring the synchronous motor rotor up to synchronous speed before excitation. It also covers on-load starting methods like using damper windings to start the motor as an induction motor initially or using a variable frequency drive to gradually increase frequency and avoid high starting torque.
A DC motor converts electrical energy to mechanical energy using a current-carrying conductor placed in an external magnetic field, which produces a force on the conductor and torque to rotate the motor's rotor shaft. DC motors consist of field and armature windings, where the field windings produce a magnetic field and the armature windings are rotated by the Lorentz force from the magnetic field and current in the windings. There are different types of DC motors including series, shunt, compound, and permanent magnet motors.
The document discusses the construction and working of DC motors. It describes the key components of a DC motor including the stator, rotor, yoke, poles, field windings, armature windings, commutator, and brushes. It also explains the different types of DC motors such as permanent magnet, separately excited, self-excited, shunt wound, series wound, and compound wound motors. Applications of different DC motor types are also summarized.
This document discusses permanent magnet motors and magnetic generators that can produce energy without using fuel. It describes ShenHe Wang's 5-kilowatt permanent magnet generator that was suppressed from public display by the Chinese government. It also summarizes John Ecklin's magnetic shielding generator patent and the Ecklin-Brown generator, which use rotating magnetic shields to fluctuate magnetic fields and drive generators. The document argues that governments suppress free-energy devices to maintain control over power supplies and citizens.
CONSTRUCTION OF DC MACHINE, INDUCTION MACHINE & SYNCHRONOUS MACHINE|DAY 11|BA...Prasant Kumar
#CONSTRUCTION OF DC MACHINE
#DC MACHINE CONSTRUCTION IN HINDI
#INDUCTION MACHINE CONSTRUCTION IN HINDI
#SYNCHRONOUS MACHINE CONSTRUCTION IN HINDI
#CONSTRUCTION OF INDUCTION MACHINE
#CONSTRUCTION OF SYNCHRONOUS MACHINE
#CONSTRUCTION OF DC MOTOR
#CONSTRUCTION OF DC GENERATOR
#CONSTRUCTION OF INDUCTION MOTOR
#BASIC ELECTRICAL ENGINEERING
Electrical machine Day 11, Construction of DC, Induction motor, Synchronous generator, Synchronous motor, alternator, Basic Electrical Engineering
Syllabus
Introduction of Machine
Classification of Machine
Construction of DC, Induction & Synchronous machine
Working Principle
EMF Equation of all machine
A transformer works on alternating current, while a DC machine works on Direct Current
It has two main parts :
Stator – It is the stationary part. It does not move or rotate.
Rotor – It is the rotating part of the machine.
Electrical machine Day 11,Construction of DC, Induction motor, Synchronous generator, Synchronous motor,alternator,Basic Electrical Engineering
Syllabus
Introduction of Machine
Classification of Machine
Construction of DC, Induction & Synchronous machine
Working Principle
EMF Equation of all machine
A transformer works on alternating current, while a DC machine works on Direct Current
It has two main parts :
Stator – It is the stationary part. It does not move or rotate.
Rotor – It is the rotating part of the machine.
YOKE
It is the outermost part of a DC motor. It is made of cast iron or cast steel.
It provides mechanical protection to the inner parts of the machine.
Provide low reluctance path for the magnetic flux.
Pole core
These are made of cast steel laminations.
The main purpose is to hold the field windings .
The end portion of the pole is called pole shoe.
FIELD WINDING
They are enameled copper wires wound around the poles
When current passes through series connected windings then adjacent poles attain opposite polarity
Armature core
This is the rotating part of the machine
It is a cylindrical structure with slots around its outer periphery.
It houses conductors in the slots.
It provides easy path for magnetic flux
This document discusses different types of electric motors:
1. Permanent magnet synchronous motors have constant torque output but are expensive and available only in small sizes. They are used in precision equipment.
2. Stepped motors move in discrete steps and have multiple coil phases. Variable-reluctance stepped motors work by aligning the rotor with the stator's magnetic field. Permanent magnet stepped motors produce more torque but require reversing current to change direction.
3. Brushless DC motors have electronically controlled commutation without brushes, making them more efficient than brushed DC motors. They are used in computer hard drives and other applications.
Electric motors are used in a wide variety of applications, from tiny motors in watches to large motors powering ships. There are many different types of electric motors that each have unique characteristics making some better suited for certain applications than others. Some common applications of electric motors include power tools like electric screwdrivers, appliances like water pumps and air compressors, automatic door systems, ventilation systems, air cooling systems, electric vehicles like bicycles, ATVs, and cars, as well as industrial uses such as conveyor systems and electric trains.
SYNCHRONOUS MOTOR STARTING METHODS, START करने के METHODS|DAMPER WINDING, AUX...Prasant Kumar
This document discusses different starting methods for synchronous motors. It describes using an auxiliary induction motor or DC motor to bring the synchronous motor rotor up to synchronous speed before excitation. It also covers on-load starting methods like using damper windings to start the motor as an induction motor initially or using a variable frequency drive to gradually increase frequency and avoid high starting torque.
A DC motor converts electrical energy to mechanical energy using a current-carrying conductor placed in an external magnetic field, which produces a force on the conductor and torque to rotate the motor's rotor shaft. DC motors consist of field and armature windings, where the field windings produce a magnetic field and the armature windings are rotated by the Lorentz force from the magnetic field and current in the windings. There are different types of DC motors including series, shunt, compound, and permanent magnet motors.
The document discusses the construction and working of DC motors. It describes the key components of a DC motor including the stator, rotor, yoke, poles, field windings, armature windings, commutator, and brushes. It also explains the different types of DC motors such as permanent magnet, separately excited, self-excited, shunt wound, series wound, and compound wound motors. Applications of different DC motor types are also summarized.
This document discusses permanent magnet motors and magnetic generators that can produce energy without using fuel. It describes ShenHe Wang's 5-kilowatt permanent magnet generator that was suppressed from public display by the Chinese government. It also summarizes John Ecklin's magnetic shielding generator patent and the Ecklin-Brown generator, which use rotating magnetic shields to fluctuate magnetic fields and drive generators. The document argues that governments suppress free-energy devices to maintain control over power supplies and citizens.
CONSTRUCTION OF DC MACHINE, INDUCTION MACHINE & SYNCHRONOUS MACHINE|DAY 11|BA...Prasant Kumar
#CONSTRUCTION OF DC MACHINE
#DC MACHINE CONSTRUCTION IN HINDI
#INDUCTION MACHINE CONSTRUCTION IN HINDI
#SYNCHRONOUS MACHINE CONSTRUCTION IN HINDI
#CONSTRUCTION OF INDUCTION MACHINE
#CONSTRUCTION OF SYNCHRONOUS MACHINE
#CONSTRUCTION OF DC MOTOR
#CONSTRUCTION OF DC GENERATOR
#CONSTRUCTION OF INDUCTION MOTOR
#BASIC ELECTRICAL ENGINEERING
Electrical machine Day 11, Construction of DC, Induction motor, Synchronous generator, Synchronous motor, alternator, Basic Electrical Engineering
Syllabus
Introduction of Machine
Classification of Machine
Construction of DC, Induction & Synchronous machine
Working Principle
EMF Equation of all machine
A transformer works on alternating current, while a DC machine works on Direct Current
It has two main parts :
Stator – It is the stationary part. It does not move or rotate.
Rotor – It is the rotating part of the machine.
Electrical machine Day 11,Construction of DC, Induction motor, Synchronous generator, Synchronous motor,alternator,Basic Electrical Engineering
Syllabus
Introduction of Machine
Classification of Machine
Construction of DC, Induction & Synchronous machine
Working Principle
EMF Equation of all machine
A transformer works on alternating current, while a DC machine works on Direct Current
It has two main parts :
Stator – It is the stationary part. It does not move or rotate.
Rotor – It is the rotating part of the machine.
YOKE
It is the outermost part of a DC motor. It is made of cast iron or cast steel.
It provides mechanical protection to the inner parts of the machine.
Provide low reluctance path for the magnetic flux.
Pole core
These are made of cast steel laminations.
The main purpose is to hold the field windings .
The end portion of the pole is called pole shoe.
FIELD WINDING
They are enameled copper wires wound around the poles
When current passes through series connected windings then adjacent poles attain opposite polarity
Armature core
This is the rotating part of the machine
It is a cylindrical structure with slots around its outer periphery.
It houses conductors in the slots.
It provides easy path for magnetic flux
This document discusses different types of electric motors:
1. Permanent magnet synchronous motors have constant torque output but are expensive and available only in small sizes. They are used in precision equipment.
2. Stepped motors move in discrete steps and have multiple coil phases. Variable-reluctance stepped motors work by aligning the rotor with the stator's magnetic field. Permanent magnet stepped motors produce more torque but require reversing current to change direction.
3. Brushless DC motors have electronically controlled commutation without brushes, making them more efficient than brushed DC motors. They are used in computer hard drives and other applications.
The document summarizes the key components and operating principles of an induction motor. It has two main parts: the stator and the rotor. The stator, the stationary part, contains windings that generate a rotating magnetic field. The rotor, the rotating part, is induced to turn by electromagnetic induction from the stator field. There are two main types of rotors: squirrel cage and wound slip ring. The induction motor works by the rotor conductors generating currents from the rotating stator field, causing the rotor to turn at a slightly lower synchronous speed due to slippage.
Iaetsd a new multilevel inverter topology for fourIaetsd Iaetsd
This document proposes a new multilevel inverter topology for driving a four-pole induction motor. The topology uses four two-level inverters connected to the separated windings of the motor's stator to generate five voltage levels. This is done using a single DC link shared between the inverters. Sine triangular pulse width modulation is used to generate switching signals while avoiding common mode currents. Simulation results show the output voltage waveform for different modulation indices as well as the speed-torque characteristics of the induction motor driven by the proposed inverter topology. The topology reduces harmonics and improves efficiency compared to traditional multilevel inverter configurations.
1. The document defines various components of DC motors such as armature, commutator, and interpoles. It also defines DC motor types like shunt, series, and compound motors.
2. It provides explanations for various characteristics of DC motors like speed regulation, starting torque, methods of speed control, and effects of changing motor parameters.
3. The document contains over 70 definitions and explanations related to DC motor components, types, characteristics, and performance.
Types of electric motors include DC motors, AC motors, and other specialty motors. DC motors include shunt, series, and permanent magnet motors. AC motors include induction and synchronous motors. Other motors include reluctance, hysteresis, stepper, and brushless DC motors. The document provides details on the operating principles and applications of these various electric motor types.
DESIGN AND FABRICATION OF SINGLE CYLINDER SOLENOID ENGINEvivatechijri
Combustion takes place & produces alittle explosion inside the piston cylinder, which converts into
energy. We all knowIC-Engines are utilized in Automobiles, Aero plane etc. But incomplete combustion generates
some harmful gasses, which is main reason for pollution. Science & Technology has been taken many steps for
controlling pollution. Like, using CNGs & LPGs rather than Fossil fuels.. Now technology brings Electrical bikes,
scooters & cars. Battery of electrical vehicle can be charged easily like mobile. They have less running cost &
100% emission free. But they need very less load carrying capacity & they are also not suitable for long run. So
basically, we must prefer Engines for more power & more running capacity. Here we have introduced a
mechanism which has more load carrying and running capacity then electric vehicles but make zero emission or
pollution. And Introducing Solenoid engines to the world is important as by seeing the current growing electrical
automobile market obviously their will a huge demand for the Induction motors as well which in turn will make
the traditional IC engine deplict. So, to see the engines in future we have to make some changes in the Tradition
Engines. Solenoid engines is a step in the same direction.
WEG Manual de especificaciones de MotoresDaniel García
This document provides specifications and information about electric motors produced by WEG, a leading global supplier of electric motors and other industrial equipment. It covers key topics such as motor types, power supply characteristics, operating characteristics, environmental specifications, and mounting arrangements. The document is intended to help customers, sellers, and workers better understand and work with WEG electric motor products. It contains 10 sections that describe technical details and specifications.
This presentation provides an overview of induction motors, including:
1. It discusses the history and invention of induction motors by Tesla and Dobrovolsky.
2. It explains the principle of operation of induction motors, how they generate torque via electromagnetic induction without direct electrical connection to the rotor.
3. It covers the construction of common induction motors, including squirrel cage and slip ring rotors, and describes speed control techniques like PWM.
The document discusses permanent magnet motors and free energy devices. It describes ShenHe Wang's 5 kilowatt permanent magnet generator that uses magnetic particles in a liquid. It summarizes that most governments suppress free energy technologies to maintain control over power supplies and revenues. It then provides details on the construction and operation of John Ecklin's magnetic shielding generator, which uses a rotating magnetic shield to produce a fluctuating magnetic field and generate electricity with less input power than the motor requires.
1. The document discusses synchronous machines which are used as AC generators and motors. It describes the construction of synchronous machines including salient pole and round rotor types.
2. An equation for the induced EMF in a synchronous generator is derived. Key factors affecting the EMF like pitch factor and distribution factor are explained.
3. The operation of synchronous generators is discussed when connected to loads. The effect of load power factor on the phase relationship between induced EMF and current is summarized.
The document provides lecture notes on electrical machines part 2, covering modules 3 and 4. Module 3 discusses three-phase induction motors, including their types, construction, principle of operation, equivalent circuit, performance characteristics, and starting methods. Module 4 covers single-phase induction motors, including their theory of operation, starting methods, and types such as split-phase and shaded-pole motors. It also discusses series motors and universal motors.
The document describes the design and construction of an electromagnetic actuator that converts electrical energy into linear reciprocating motion. It consists of two magnets - an electromagnet and a permanent magnet. The electromagnet is powered by a battery and its polarity is switched to alternately repel and attract the permanent magnet piston, causing it to move back and forth. This linear motion is then converted into rotational motion using connecting rods and a crankshaft.
COMPARISON BETWEEN SALIENT POLE AND CYLINDRICAL POLE ROTOR|DAY 17|SIMPLE TRIC...Prasant Kumar
This document compares salient pole and cylindrical pole synchronous machine rotors. Salient pole rotors have projecting poles, larger diameters, and shorter axial lengths. They are used for lower speeds from 100-1500 RPM and require more poles. Cylindrical rotors are drum-shaped with parallel slots for windings, have smaller diameters but longer axial lengths. They are used for higher speeds from 1500-3000 RPM and typically have 2-4 poles. Cylindrical rotors have better flux distribution and output waveform but salient pole rotors may require damper windings to prevent oscillations.
This document presents information on a magnetic repulsion permanent engine (MRPE). It consists of 3 sentences:
The MRPE works by using repulsion and attraction forces between permanent magnets and a ferromagnetic plate to push and pull magnetic pistons inside cylinders, replacing the combustion process of a traditional engine. It describes the basic components, including the magnetic pistons, cylinder, flywheel rod, repulsion-attraction plate, and control electronics to synchronize piston movement. The document outlines the working principle, operation cycle, speed control, and advantages over fossil fuel engines, such as being fuel-less, low maintenance, and environmentally friendly.
This article relates to energy engineering and more particularly to the alternative energy technology of getting power from the repulsive/attractive force of permanent magnets with no other input.
This document discusses radial and axial flux permanent magnet machines. It describes how permanent magnets replaced electromagnets in synchronous machines, eliminating slip rings and brush assemblies. This contributed to the development of PMBLDC and PM synchronous machines. It categorizes PM machines as radial flux, axial flux, or transversal flux depending on the direction of flux through the air gap. Axial flux machines have magnetic force along the shaft plane, similar to disc brakes, while radial flux is perpendicular to the shaft. Various rotor and stator configurations are discussed for both radial and axial flux machines.
This document is a certificate from the Diploma Mechanical Engineering Department of Lukhdhirji Engineering College in Morbi, India for the year 2014-2015. It certifies that 5 students, including RANK KRUNAL M., YADAV PARAS J., SOLANKI VISHAL V., PATEL PIYUSH K., and PATEL SACHIN M., have satisfactorily completed their term work in the subject of Project-I within the prescribed time limit and guidelines. The students thank the head of the department and their guide for the opportunity to work on a mechanical engineering project and for their guidance.
This document discusses different types of repulsion motors. It begins by explaining the basic operating principle of a repulsion motor, which produces torque when the brushes are shifted from being aligned with the magnetic axis. It then categorizes repulsion motors into four types: standard repulsion motors, compensated repulsion motors, repulsion start induction motors, and repulsion induction motors. For each type, it provides a brief description of the construction and operating characteristics. The document focuses on explaining how each motor variation improves upon the standard repulsion motor design to provide benefits like constant speed operation and higher starting torque.
This two-day workshop helps couples reconnect through seven conversations that build intimacy and handle conflict better. Based on the book "Hold Me Tight", the workshop uses videos, exercises and group participation to help couples break negative cycles, understand each other's emotions, restore trust, and gain encouragement from others also working to strengthen their relationships. The early registration price for participating couples is $575.
Slideshare es una plataforma para compartir presentaciones de forma pública o privada de manera similar a YouTube pero para presentaciones como PowerPoint. Los usuarios pueden comentar, compartir y puntuar las presentaciones de otros, y es común encontrar enlaces útiles en Slideshare cuando se busca información en Google. Slideshare ofrece varias funciones como subir presentaciones directamente desde Dropbox y añadir audio para crear podcasts de diapositivas.
The document summarizes the key components and operating principles of an induction motor. It has two main parts: the stator and the rotor. The stator, the stationary part, contains windings that generate a rotating magnetic field. The rotor, the rotating part, is induced to turn by electromagnetic induction from the stator field. There are two main types of rotors: squirrel cage and wound slip ring. The induction motor works by the rotor conductors generating currents from the rotating stator field, causing the rotor to turn at a slightly lower synchronous speed due to slippage.
Iaetsd a new multilevel inverter topology for fourIaetsd Iaetsd
This document proposes a new multilevel inverter topology for driving a four-pole induction motor. The topology uses four two-level inverters connected to the separated windings of the motor's stator to generate five voltage levels. This is done using a single DC link shared between the inverters. Sine triangular pulse width modulation is used to generate switching signals while avoiding common mode currents. Simulation results show the output voltage waveform for different modulation indices as well as the speed-torque characteristics of the induction motor driven by the proposed inverter topology. The topology reduces harmonics and improves efficiency compared to traditional multilevel inverter configurations.
1. The document defines various components of DC motors such as armature, commutator, and interpoles. It also defines DC motor types like shunt, series, and compound motors.
2. It provides explanations for various characteristics of DC motors like speed regulation, starting torque, methods of speed control, and effects of changing motor parameters.
3. The document contains over 70 definitions and explanations related to DC motor components, types, characteristics, and performance.
Types of electric motors include DC motors, AC motors, and other specialty motors. DC motors include shunt, series, and permanent magnet motors. AC motors include induction and synchronous motors. Other motors include reluctance, hysteresis, stepper, and brushless DC motors. The document provides details on the operating principles and applications of these various electric motor types.
DESIGN AND FABRICATION OF SINGLE CYLINDER SOLENOID ENGINEvivatechijri
Combustion takes place & produces alittle explosion inside the piston cylinder, which converts into
energy. We all knowIC-Engines are utilized in Automobiles, Aero plane etc. But incomplete combustion generates
some harmful gasses, which is main reason for pollution. Science & Technology has been taken many steps for
controlling pollution. Like, using CNGs & LPGs rather than Fossil fuels.. Now technology brings Electrical bikes,
scooters & cars. Battery of electrical vehicle can be charged easily like mobile. They have less running cost &
100% emission free. But they need very less load carrying capacity & they are also not suitable for long run. So
basically, we must prefer Engines for more power & more running capacity. Here we have introduced a
mechanism which has more load carrying and running capacity then electric vehicles but make zero emission or
pollution. And Introducing Solenoid engines to the world is important as by seeing the current growing electrical
automobile market obviously their will a huge demand for the Induction motors as well which in turn will make
the traditional IC engine deplict. So, to see the engines in future we have to make some changes in the Tradition
Engines. Solenoid engines is a step in the same direction.
WEG Manual de especificaciones de MotoresDaniel García
This document provides specifications and information about electric motors produced by WEG, a leading global supplier of electric motors and other industrial equipment. It covers key topics such as motor types, power supply characteristics, operating characteristics, environmental specifications, and mounting arrangements. The document is intended to help customers, sellers, and workers better understand and work with WEG electric motor products. It contains 10 sections that describe technical details and specifications.
This presentation provides an overview of induction motors, including:
1. It discusses the history and invention of induction motors by Tesla and Dobrovolsky.
2. It explains the principle of operation of induction motors, how they generate torque via electromagnetic induction without direct electrical connection to the rotor.
3. It covers the construction of common induction motors, including squirrel cage and slip ring rotors, and describes speed control techniques like PWM.
The document discusses permanent magnet motors and free energy devices. It describes ShenHe Wang's 5 kilowatt permanent magnet generator that uses magnetic particles in a liquid. It summarizes that most governments suppress free energy technologies to maintain control over power supplies and revenues. It then provides details on the construction and operation of John Ecklin's magnetic shielding generator, which uses a rotating magnetic shield to produce a fluctuating magnetic field and generate electricity with less input power than the motor requires.
1. The document discusses synchronous machines which are used as AC generators and motors. It describes the construction of synchronous machines including salient pole and round rotor types.
2. An equation for the induced EMF in a synchronous generator is derived. Key factors affecting the EMF like pitch factor and distribution factor are explained.
3. The operation of synchronous generators is discussed when connected to loads. The effect of load power factor on the phase relationship between induced EMF and current is summarized.
The document provides lecture notes on electrical machines part 2, covering modules 3 and 4. Module 3 discusses three-phase induction motors, including their types, construction, principle of operation, equivalent circuit, performance characteristics, and starting methods. Module 4 covers single-phase induction motors, including their theory of operation, starting methods, and types such as split-phase and shaded-pole motors. It also discusses series motors and universal motors.
The document describes the design and construction of an electromagnetic actuator that converts electrical energy into linear reciprocating motion. It consists of two magnets - an electromagnet and a permanent magnet. The electromagnet is powered by a battery and its polarity is switched to alternately repel and attract the permanent magnet piston, causing it to move back and forth. This linear motion is then converted into rotational motion using connecting rods and a crankshaft.
COMPARISON BETWEEN SALIENT POLE AND CYLINDRICAL POLE ROTOR|DAY 17|SIMPLE TRIC...Prasant Kumar
This document compares salient pole and cylindrical pole synchronous machine rotors. Salient pole rotors have projecting poles, larger diameters, and shorter axial lengths. They are used for lower speeds from 100-1500 RPM and require more poles. Cylindrical rotors are drum-shaped with parallel slots for windings, have smaller diameters but longer axial lengths. They are used for higher speeds from 1500-3000 RPM and typically have 2-4 poles. Cylindrical rotors have better flux distribution and output waveform but salient pole rotors may require damper windings to prevent oscillations.
This document presents information on a magnetic repulsion permanent engine (MRPE). It consists of 3 sentences:
The MRPE works by using repulsion and attraction forces between permanent magnets and a ferromagnetic plate to push and pull magnetic pistons inside cylinders, replacing the combustion process of a traditional engine. It describes the basic components, including the magnetic pistons, cylinder, flywheel rod, repulsion-attraction plate, and control electronics to synchronize piston movement. The document outlines the working principle, operation cycle, speed control, and advantages over fossil fuel engines, such as being fuel-less, low maintenance, and environmentally friendly.
This article relates to energy engineering and more particularly to the alternative energy technology of getting power from the repulsive/attractive force of permanent magnets with no other input.
This document discusses radial and axial flux permanent magnet machines. It describes how permanent magnets replaced electromagnets in synchronous machines, eliminating slip rings and brush assemblies. This contributed to the development of PMBLDC and PM synchronous machines. It categorizes PM machines as radial flux, axial flux, or transversal flux depending on the direction of flux through the air gap. Axial flux machines have magnetic force along the shaft plane, similar to disc brakes, while radial flux is perpendicular to the shaft. Various rotor and stator configurations are discussed for both radial and axial flux machines.
This document is a certificate from the Diploma Mechanical Engineering Department of Lukhdhirji Engineering College in Morbi, India for the year 2014-2015. It certifies that 5 students, including RANK KRUNAL M., YADAV PARAS J., SOLANKI VISHAL V., PATEL PIYUSH K., and PATEL SACHIN M., have satisfactorily completed their term work in the subject of Project-I within the prescribed time limit and guidelines. The students thank the head of the department and their guide for the opportunity to work on a mechanical engineering project and for their guidance.
This document discusses different types of repulsion motors. It begins by explaining the basic operating principle of a repulsion motor, which produces torque when the brushes are shifted from being aligned with the magnetic axis. It then categorizes repulsion motors into four types: standard repulsion motors, compensated repulsion motors, repulsion start induction motors, and repulsion induction motors. For each type, it provides a brief description of the construction and operating characteristics. The document focuses on explaining how each motor variation improves upon the standard repulsion motor design to provide benefits like constant speed operation and higher starting torque.
This two-day workshop helps couples reconnect through seven conversations that build intimacy and handle conflict better. Based on the book "Hold Me Tight", the workshop uses videos, exercises and group participation to help couples break negative cycles, understand each other's emotions, restore trust, and gain encouragement from others also working to strengthen their relationships. The early registration price for participating couples is $575.
Slideshare es una plataforma para compartir presentaciones de forma pública o privada de manera similar a YouTube pero para presentaciones como PowerPoint. Los usuarios pueden comentar, compartir y puntuar las presentaciones de otros, y es común encontrar enlaces útiles en Slideshare cuando se busca información en Google. Slideshare ofrece varias funciones como subir presentaciones directamente desde Dropbox y añadir audio para crear podcasts de diapositivas.
Linda Simpkins has over 25 years of experience in various clerical and administrative roles. She has strong computer, communication, and organizational skills and is proficient in Microsoft Office programs. She is seeking an administrative position that allows her to utilize her skills and experience.
The document characterizes the properties of 3D printed plastic scintillators. It measures the transmission spectrum and light output of 3D printed scintillators compared to a commercial scintillator. For the transmission spectrum, it uses a monochromator to define transmissivity over wavelength ranges. It finds the 3D printed scintillator has much lower transmission. For light output, it uses a Charge to Digital Converter and Photomultiplier Tube excited by a Co-60 radioactive source. By comparing peak positions in the charge distributions, it finds the 3D printed scintillator's light output is around 10% of the commercial scintillator's output, likely due to its poor transmissivity below 500nm where the PMT has peak
Este documento describe las cinco unidades básicas de la ecología - nicho ecológico, hábitat, ecosistema, biodiversidad y biosfera - y explica sus relaciones. También incluye un cuadro clasificando las relaciones ecológicas intraespecíficas e interespecíficas y por qué los ciclos de los elementos químicos son fundamentales para comprender problemas ambientales. Finalmente, describe diferentes biomas terrestres y acuáticos como zonas de vida.
Este informe presenta los resultados del estudio definitivo del mantenimiento periódico del tramo Checca - Mazocruz de la carretera Ilave (R3S) - Mazocruz. Se identificaron zonas vulnerables geológicas y geotécnicas que requieren muros de soporte, así como alcantarillas antiguas colmatadas y erosión en estructuras de drenaje que necesitan reparación. El informe también describe la topografía plana de la zona, y recomienda mejoras en alcantarillas, puentes y obras de
This is my 75 minutes "highlights" presentation on what's new in WS2012 R2. It's not all encompassing - intended just to get across the key points of the core OS. It followed a "Cloud OS" keynote and preceded a "System Center hybrid cloud" presentation.
This document describes a group project to design a robotic vehicle that can follow a black line and perform a 180 degree turn when detecting an obstacle. The robot uses a PIC18F4520 microcontroller board along with stepper motors, optical sensors, and a proximity sensor. The objectives were to get the stepper motors moving in the correct directions based on sensor input and turn 180 degrees upon obstacle detection from 15 cm away. The hardware and software designs are outlined, including assigning stepping sequences to the motors. Implementation and testing were completed with some challenges along the way.
La trayectoria es la línea que sigue un cuerpo en movimiento, la cual puede ser recta, curva o cerrada. La distancia recorrida mide la longitud de la trayectoria, mientras que el desplazamiento es la distancia más corta entre el punto inicial y final. Existen diferentes tipos de movimiento como el movimiento uniforme rectilíneo, el movimiento uniforme rectilíneo acelerado y el movimiento uniforme rectilíneo retardado.
robotics and autonomus robots which follows a line.
For those who are intrested in robotics for that it is the best presentation om line follower,
for any query or comments plesase write mail
yashpatel.14,ce@iite.indusuni.ac.in
code is also embeded in the presentation.
it also include the video of the file follower robots run by this given code \
and in robocon
La eugenesia busca mejorar la raza humana eliminando individuos con genes defectuosos. Francis Galton fue el padre de la eugenesia y aplicó la cría de caballos a los humanos para mejorar la raza. La eugenesia se basa en la teoría de la evolución, las ideas de Malthus sobre recursos limitados y la degeneración de la raza. Se ha aplicado históricamente a través del aborto, la esterilización forzada y la eutanasia, y actualmente también se usa con fines de control de la p
Este documento presenta diferentes definiciones de epistemología. La epistemología se define como la disciplina que estudia el conocimiento científico y los criterios de cientificidad, y también como el análisis de los supuestos filosóficos, valores y métodos de la ciencia. La epistemología estudia tanto el proceso de investigación científica como el conocimiento resultante. Existen tres niveles de abordaje epistemológico: la realidad estudiada por los científicos, la ciencia misma, y la epistemología.
La epistemología es la reflexión crítica sobre la ciencia y el conocimiento científico. Es una disciplina metacientífica que estudia los fundamentos, métodos y límites de la ciencia. La epistemología aborda diversos aspectos de la ciencia como la lógica, la semántica, la ontología, la axiología y los intereses que mueven a la comunidad científica. También existe la epistemología regional que se enfoca en el estudio del conocimiento de disciplinas específicas como la física, la psic
This document discusses the development of a multi-purpose machine using a Scotch yoke mechanism. It begins with an introduction to multi-operation machines and the Scotch yoke mechanism. It then discusses the construction and working principle of the Scotch yoke, including how rotational motion is converted to reciprocating motion. The document continues with sections on the apparatus used, including DC motors, principles of DC motor operation, brushed DC motors, brushless DC motors, and DC servo motors. It concludes with a discussion of DC motor behavior and factors such as high speed output, back EMF, and noise on power lines.
- The single phase series motor has excessive commutator sparking, making it only practical for the smallest sizes.
- Adding a compensating winding yields the compensated series motor, which overcomes sparking issues. Most AC commutator motors have this design.
- Universal motors can operate on either AC or DC and are used in small appliances requiring high speeds.
- A repulsion motor uses offset brushes to induce opposing magnetic fields for starting torque.
- A repulsion start induction motor uses shorted brushes to start the motor like a repulsion motor before engaging the induction rotor.
DIFFERENT ELECTRIC MOTOR OPPERATIONAL DIFFICULTIES AND REMIDES.pptxCardielMarkJayven
An electric motor converts electrical energy into mechanical energy. It consists of a stator and a rotor, with magnetic fields interacting to produce torque and rotate a shaft. Common types include AC induction motors, DC motors, servo motors, and stepper motors. Electric motors are widely used in industry, appliances, vehicles, and other applications due to their efficiency, reliability and controllability. Proper maintenance and care is required to prevent issues with electric motors.
This document provides an overview of the basics of electric motors. It discusses how electric motors work by using electromagnetic induction to convert electrical energy to mechanical motion. It then summarizes the main types of electric motors: brushed DC motors, brushless DC motors, synchronous AC motors, and induction motors. It provides details on how each type of motor functions, including descriptions of components like commutators, stators, and rotors. It also discusses important motor specifications and comparisons between motor types in terms of efficiency, reliability, speed control, and torque characteristics.
This document provides information on pulsed energy devices described by Patrick J. Kelly, specifically focusing on the motor/generator designed by Robert Adams. The summary is:
1) Robert Adams designed an electric motor that uses permanent magnets on the rotor and pulsed electromagnets on the stator. When configured correctly, the output power exceeds the input power by a large margin, such as 800%.
2) The device operates by using power collection coils positioned and timed to contribute back EMF to drive the rotor. Additional electromagnets are pulsed on and off to further boost efficiency beyond 100%.
3) Practical details are provided on components like magnet shape and size, coil dimensions, switching methods and
The document discusses brushless DC (BLDC) motors and their operation compared to conventional brushed DC motors. It explains that BLDC motors use electronics to control the motor instead of brushes, eliminating friction losses and increasing efficiency. The electronics precisely switch the motor windings to rotate the permanent magnet rotor. BLDC motors provide benefits like increased reliability, reduced noise, and longer lifetime compared to brushed motors. The document also describes some challenges with BLDC motors like increased cost and limited power due to heat compared to brushed motors.
The document provides information about permanent magnet DC motors and brushless DC motors. It discusses the construction, working principle, and applications of permanent magnet DC motors. It then describes the construction of brushless DC motors including the stator, rotor, position sensors. It explains the working of trapezoidal and sinusoidal brushless DC motors. Trapezoidal BLDC motors have trapezoidal back-EMF and current waveforms for smooth torque production, while sinusoidal BLDC motors have sinusoidal waveforms.
This document provides information about DC machines and DC motors. It discusses the working principle of DC motors, including Fleming's left hand rule. It describes the different types of DC motors such as separately excited, permanent magnet, and self-excited motors. It also outlines the parts of a DC motor like the yoke, stator, rotor, field and armature windings, poles, brushes and commutator. Additionally, it covers DC motor speed control methods like flux control, voltage control and armature resistance control. Finally, it briefly discusses DC generators and their working principle.
An AC motor operates using a rotating magnetic field produced by an alternating current to generate torque and turn the rotor shaft. There are two main types - synchronous motors where the rotor rotates at the exact supply frequency, and induction motors where the rotor rotates slightly slower. Induction motors are the most common and operate using electromagnetic induction to induce currents in the rotor and generate torque. Squirrel cage rotors are the most widely used type and consist of conductive bars in the rotor that induce currents to generate a magnetic field and turn the shaft.
The document discusses DC machines which can operate as either motors or generators depending on the direction of power flow. A DC machine consists of a static electromagnetic or permanent magnetic field and a rotating armature. The field produces a magnetic medium and the armature produces voltage and torque under the action of the magnetic field. An advantage of DC motors is their speed is easy to control over a wide range, while DC generators are now quite rare. Most DC machines have AC voltages and currents internally but produce DC outputs via a commutator mechanism.
1) The document discusses the differences between DC and AC motors, explaining that DC motors have either a shunt or series configuration depending on whether the field winding is parallel or series with the armature.
2) AC motors include induction motors which have a rotating magnetic field generated by the stator that induces a signal in the rotor, causing it to rotate.
3) Key terms for both motor types are discussed such as commutator, brushes, counter EMF, torque, speed regulation, synchronous speed, and slip.
The universal motor can operate on either AC or DC power sources. It is modified slightly from a DC series motor to allow proper operation on AC, such as adding a compensating winding and using laminated pole pieces. Universal motors are commonly used in appliances and power tools where high speed and torque are needed. They have advantages of simple construction and cost effectiveness.
This document provides an overview of different types of electric motors for electrical engineering students. It discusses the basics of DC motors, which use direct current and can adjust speed through current intensity. It also covers AC motors, which use alternating current and magnetic forces to propel the rotor. Specific types of DC motors described include brushed and brushless, while AC motor types include induction motors, which rely on induced current, and synchronous motors, which require both AC and DC power sources.
DC motors generate torque directly from DC power using internal commutation and stationary magnets. Brushless DC motors use rotating magnets and stationary coils. AC motors have a stationary stator with coils powered by AC current to generate a rotating magnetic field, and a rotor given torque.
DC motors offer excellent speed control but require more maintenance due to brushes. AC motors are cheaper, more reliable with no brushes, allow for speed variation, and have high power factors, making them suitable for most industrial applications powered by AC sources. Both motor types have advantages dependent on the application.
This document discusses DC motors, including their basic parts and working principles. A DC motor converts electrical energy to mechanical energy using electromagnetic principles. It consists of a rotor and stator, with the rotor containing windings that spin when current is passed through in the presence of a magnetic field. The document compares DC motors to generators and lists different types of motors, explaining the basic operation of a simple DC motor.
A practical guide to free energy devices pages 23 32 - patrick j. kellyMrinal Pal
This document discusses permanent magnet motors and generators. It begins by explaining how permanent magnets work and debunking the idea that they cannot do work. It then summarizes several designs for permanent magnet motors and generators, including ones that use rotating magnetic shields to produce power without resistance. Key designs discussed include those by John Bedini, Wang Shum Ho, John Ecklin, and Howard Johnson. The document emphasizes that permanent magnets can power generators indefinitely without external fuel.
Advantages and Disadvatages of AC/DC MotorFika Khamis
Simple explanation on advantages and disadvantages of AC and DC motor. Focusing on main point only since the slides is for presentation. Originally design by me.
Different types of electrical motors can be categorized into three main segments: AC motors, DC motors, and special purpose motors. DC motors include shunt wound, series, compound, and permanent magnet DC motors which differ based on how the field and armature windings are connected. AC motors include synchronous and induction motors which operate based on AC frequency. Special purpose motors include stepper motors, brushless DC motors, servo motors, and reluctance motors which have specialized applications.
The document discusses DC motors, DC generators, AC motors, and AC generators.
1. A DC motor converts direct current into mechanical energy using the Lorentz force principle. It has an armature and stator. A DC generator converts mechanical energy into direct current using electromagnetic induction.
2. The key differences between AC and DC machines are that AC motors have rotating magnetic fields and multiple phases while DC motors have a rotating armature. AC generators have fixed coils and rotating magnets, making construction simpler, while DC generators have commutators.
3. The document provides definitions, construction details, working principles, and comparison of the different motor and generator types.
A DC motor converts direct current into mechanical energy. It works on the principle that a current-carrying conductor in a magnetic field experiences a force. There are three main types of DC motors: shunt wound motors which run at a constant speed, series wound motors which decrease in speed under load, and compound wound motors which have characteristics of both. The main parts of a DC motor are the yoke, poles, armature, field and armature windings, commutator, brushes, and shaft. Routine maintenance includes cleaning, inspecting brushes and commutator, checking bearings and connections, and testing annually.
How to Make a Field Mandatory in Odoo 17Celine George
In Odoo, making a field required can be done through both Python code and XML views. When you set the required attribute to True in Python code, it makes the field required across all views where it's used. Conversely, when you set the required attribute in XML views, it makes the field required only in the context of that particular view.
How to Add Chatter in the odoo 17 ERP ModuleCeline George
In Odoo, the chatter is like a chat tool that helps you work together on records. You can leave notes and track things, making it easier to talk with your team and partners. Inside chatter, all communication history, activity, and changes will be displayed.
Main Java[All of the Base Concepts}.docxadhitya5119
This is part 1 of my Java Learning Journey. This Contains Custom methods, classes, constructors, packages, multithreading , try- catch block, finally block and more.
Exploiting Artificial Intelligence for Empowering Researchers and Faculty, In...Dr. Vinod Kumar Kanvaria
Exploiting Artificial Intelligence for Empowering Researchers and Faculty,
International FDP on Fundamentals of Research in Social Sciences
at Integral University, Lucknow, 06.06.2024
By Dr. Vinod Kumar Kanvaria
LAND USE LAND COVER AND NDVI OF MIRZAPUR DISTRICT, UPRAHUL
This Dissertation explores the particular circumstances of Mirzapur, a region located in the
core of India. Mirzapur, with its varied terrains and abundant biodiversity, offers an optimal
environment for investigating the changes in vegetation cover dynamics. Our study utilizes
advanced technologies such as GIS (Geographic Information Systems) and Remote sensing to
analyze the transformations that have taken place over the course of a decade.
The complex relationship between human activities and the environment has been the focus
of extensive research and worry. As the global community grapples with swift urbanization,
population expansion, and economic progress, the effects on natural ecosystems are becoming
more evident. A crucial element of this impact is the alteration of vegetation cover, which plays a
significant role in maintaining the ecological equilibrium of our planet.Land serves as the foundation for all human activities and provides the necessary materials for
these activities. As the most crucial natural resource, its utilization by humans results in different
'Land uses,' which are determined by both human activities and the physical characteristics of the
land.
The utilization of land is impacted by human needs and environmental factors. In countries
like India, rapid population growth and the emphasis on extensive resource exploitation can lead
to significant land degradation, adversely affecting the region's land cover.
Therefore, human intervention has significantly influenced land use patterns over many
centuries, evolving its structure over time and space. In the present era, these changes have
accelerated due to factors such as agriculture and urbanization. Information regarding land use and
cover is essential for various planning and management tasks related to the Earth's surface,
providing crucial environmental data for scientific, resource management, policy purposes, and
diverse human activities.
Accurate understanding of land use and cover is imperative for the development planning
of any area. Consequently, a wide range of professionals, including earth system scientists, land
and water managers, and urban planners, are interested in obtaining data on land use and cover
changes, conversion trends, and other related patterns. The spatial dimensions of land use and
cover support policymakers and scientists in making well-informed decisions, as alterations in
these patterns indicate shifts in economic and social conditions. Monitoring such changes with the
help of Advanced technologies like Remote Sensing and Geographic Information Systems is
crucial for coordinated efforts across different administrative levels. Advanced technologies like
Remote Sensing and Geographic Information Systems
9
Changes in vegetation cover refer to variations in the distribution, composition, and overall
structure of plant communities across different temporal and spatial scales. These changes can
occur natural.
This presentation was provided by Steph Pollock of The American Psychological Association’s Journals Program, and Damita Snow, of The American Society of Civil Engineers (ASCE), for the initial session of NISO's 2024 Training Series "DEIA in the Scholarly Landscape." Session One: 'Setting Expectations: a DEIA Primer,' was held June 6, 2024.
Strategies for Effective Upskilling is a presentation by Chinwendu Peace in a Your Skill Boost Masterclass organisation by the Excellence Foundation for South Sudan on 08th and 09th June 2024 from 1 PM to 3 PM on each day.
A review of the growth of the Israel Genealogy Research Association Database Collection for the last 12 months. Our collection is now passed the 3 million mark and still growing. See which archives have contributed the most. See the different types of records we have, and which years have had records added. You can also see what we have for the future.
This slide is special for master students (MIBS & MIFB) in UUM. Also useful for readers who are interested in the topic of contemporary Islamic banking.
हिंदी वर्णमाला पीपीटी, hindi alphabet PPT presentation, hindi varnamala PPT, Hindi Varnamala pdf, हिंदी स्वर, हिंदी व्यंजन, sikhiye hindi varnmala, dr. mulla adam ali, hindi language and literature, hindi alphabet with drawing, hindi alphabet pdf, hindi varnamala for childrens, hindi language, hindi varnamala practice for kids, https://www.drmullaadamali.com
Liberal Approach to the Study of Indian Politics.pdf
1
1. 1. http://www.solarbotics.net/starting/200111_dcmotor/200111_dcmotor2.html
In any electric motor, operation is based on simple electromagnetism. A current-
carrying conductor generates a magnetic field; when this is then placed in an
external magnetic field, it will experience a force proportional to the current in the
conductor, and to the strength of the external magnetic field. As you are well aware
of from playing with magnets as a kid, opposite (North and South) polarities
attract, while like polarities (North and North, South and South) repel. The internal
configuration of a DC motor is designed to harness the magnetic interaction
between a current-carrying conductor and an external magnetic field to generate
rotational motion.
Let's start by looking at a simple 2-pole DC electric motor (here red represents a
magnet or winding with a "North" polarization, while green represents a magnet or
winding with a "South" polarization).
Every DC motor has six basic parts -- axle, rotor (a.k.a., armature), stator,
commutator, field magnet(s), and brushes. In most common DC motors (and all
that BEAMers will see), the external magnetic field is produced by high-strength
permanent magnets1. The stator is the stationary part of the motor -- this includes
the motor casing, as well as two or more permanent magnet pole pieces. The rotor
(together with the axle and attached commutator) rotate with respect to the stator.
The rotor consists of windings (generally on a core), the windings being
electrically connected to the commutator. The above diagram shows a common
motor layout -- with the rotor inside the stator (field) magnets.
The geometry of the brushes, commutator contacts, and
rotor windings are such that when power is applied, the
polarities of the energized winding and the stator magnet(s)
are misaligned, and the rotor will rotate until it is almost
aligned with the stator's field magnets. As the rotor reaches
alignment, the brushes move to the next commutator
contacts, and energize the next winding. Given our example
two-pole motor, the rotation reverses the direction
2. of current through the rotor winding, leading to a "flip" of
the rotor's magnetic field, driving it to continue rotating.
In real life, though, DC motors will always have more than
two poles (three is a very common number). In particular,
this avoids "dead spots" in the commutator. You can
imagine how with our example two-pole motor, if the rotor
is exactly at the middle of its rotation (perfectly aligned with
the field magnets), it will get "stuck" there. Meanwhile, with
a two-pole motor, there is a moment where the commutator
shorts out the power supply (i.e., both brushes touch both
commutator contacts simultaneously). This would be bad for
the power supply, waste energy, and damage motor
components as well. Yet another disadvantage of such a
simple motor is that it would exhibit a high amount
of torque "ripple" (the amount of torque it could produce is
cyclic with the position of the rotor).
So since most small DC motors are of a three-pole design, let's tinker with the
workings of one via an interactive animation (JavaScript required):
You'll notice a few things from this -- namely, one pole is fully energized at a time
(but two others are "partially" energized). As each brush transitions from one
commutator contact to the next, one coil's field will rapidly collapse, as the next
coil's field will rapidly charge up (this occurs within a few microsecond). We'll see
more about the effects of this later, but in the meantime you can see that this is a
direct result of the coil windings' series wiring:
3. There's probably no better way to see how an
average DC motor is put together, than by just opening one
up. Unfortunately this is tedious work, as well as requiring the
destruction of a perfectly good motor.
Luckily for you, I've gone ahead and done this in your stead.
The guts of a disassembled Mabuchi FF-030-PN motor
(the same model that Solarbotics sells) are available for you to
see here (on 10 lines / cm graph paper). This is a basic 3-
pole DC motor, with 2 brushes and three commutator
contacts.
The use of an iron core armature (as in the Mabuchi, above) is quite common, and
has a number of advantages2. First off, the iron core provides a strong, rigid
support for the windings -- a particularly important consideration for high-
torque motors. The core also conducts heat away from the rotor windings, allowing
the motor to be driven harder than might otherwise be the case. Iron core
construction is also relatively inexpensive compared with other construction types.
But iron core construction also has several disadvantages. The iron armature has a
relatively high inertia which limits motor acceleration. This construction also
results in high winding inductances which limit brush and commutator life.
In small motors, an alternative design is often used which features a 'coreless'
armature winding. This design depends upon the coil wire itself for structural
integrity. As a result, the armature is hollow, and the permanent magnet can be
mounted inside the rotor coil. Coreless DC motors have much lower
armature inductance than iron-core motors of comparable size, extending brush
and commutator life.
4. Diagram courtesy of MicroMo
The coreless design also allows manufacturers to build smaller motors; meanwhile,
due to the lack of iron in their rotors, coreless motors are somewhat prone to
overheating. As a result, this design is generally used just in small, low-power
motors. BEAMers will most often see coreless DC motors in the form of pager
motors.
Again, disassembling a coreless motor can be instructive --
in this case, my hapless victim was a cheap pager vibrator
motor. The guts of this disassembled motor are available
for you to see here (on 10 lines / cm graph paper). This is
(or more accurately, was) a 3-pole coreless DC motor.
I disembowel 'em so you don't have to...
……………………………………………………………
http://www.plantservices.com/articles/2010/02dcmotors/
Home / Articles / 2010 / DC motors: Why are they still used?
DC motors: Why are they still used?
The reasons come from the user base, R&D and
the application.
By Bob Simon M.Sc., P.E.
Feb 04, 2010
Print Email
i nShar e
- A A A A +
1 of 3 < 1 | 2 | 3 > View on one page
5. DC motors were first developed in the early 19th century and continue to be used
today. Ányos Jedlik is credited as being the first to experiment with DC motors in
1827. William Sturgeon (1832) and Thomas Davenport (1837) are credited with
taking Jedlik’s laboratory instrument and trying to commercialize it. It wasn’t until
1871 when Zénobe Gramme’s design of a dynamo was accidentally connected to a
second dynamo that was producing a voltage that the DC motor we think of today
start to turn and do work.
The DC motor reigned alone in the factory for only 11 years. In 1888, Nicola Tesla
stepped into the factory with today’s well known three-phase electric system and the
AC induction motor has been taking work away from the DC motor ever since.
So, the question remains — why has the DC motor continued to be used from 1888
until today? A primary reason is the motor’s variable speed characteristic. When the
voltage to a DC motor is increased from zero to some base voltage, the motor’s
speed increases from zero to a corresponding base speed. An induction motor, on
the other hand, always runs at full speed. If a speed other then this is desired, it must
be achieved via belts and pulleys, hydraulic pumps and motors, or gear boxes and
clutches. These devices provide for rotation at a speed something less (or greater)
then the design speed, but adds mechanical complexity.
A DC motor can develop full torque within the operational speed range from zero to
base speed (Figure 1). This allows the DC motor to be used on constant-torque
loads such as conveyor belts, elevators, cranes, ski lifts, extruders and mixers.
These applications can be stopped when fully loaded and will require full torque to
get them moving again.
Getting a variable DC voltage to a DC motor was done in several ways. The easiest
was with a large carbon rheostat that either increased or decreased the voltage
Figure 1. Torque comparison of DC and AC motors. Motor speed in per unit
values is located on the horizontal and torque developed by the motor in per
unit values on the vertical axis (1 = 100%). The green line is the nominal
developed DC motor torque and shows that a DC motor can develop 100%
torque from 0-100% speed. Neither the AC self-ventilated nor the forced
ventilated motors can match the torque development at very low rotational
speeds.
6. supplied to the motor. It also was done with motor-generator (MG) sets, which used
a constant-speed AC motor directly coupled to a DC generator. The generator’s field
was then increased or decreased. This resulted in an increase or decrease in the
generator’s terminal voltage. As terminal voltage increases or decreases, the speed
of the connected DC motor also increases or decreases.
Static inverters were developed later and the rectification of AC to DC was done
using vacuum tubes. Semiconductors were developed and the analog converter
replaced the rectifiers. Finally, the microprocessor was developed and the converter
went digital. That’s where the technology stands today with respect to providing an
AC-to-DC conversion.
As the development of semiconductors continued, the development of the digital DC
converter also continued. More importantly, this lead to the development of the AC
inverter. The AC inverter is the bit of engineering technology that was going to push
the DC motor down the same path as the Pickett slide rule and the Post draftsman’s
compass. The AC inverter allows a standard induction motor to be operated at any
speed, just like the DC motor. And, it does this without brushes. Brushes are the
primary maintenance headache when using a DC motor.
Performance characteristics
DC motors have three operating regions (Figure 1). The first is from zero to the base
speed and is called the called the constant-torque range. As motor voltage is
increased from zero to base voltage, the ability to develop full torque remains
constant. Motor power increases from zero to rated power as the voltage changes.
Often, this region is labeled VP/CT for variable power/constant torque. This
characteristic of a DC motor lent itself well to applications that had to operate at
various speeds while fully loaded.
http://www.plantservices.com/assets/Media/1002/Article_DCMotor2HR.jpg
7. The second region is called the field-weakening (FW) operational range or constant-
power range (Figure 2). This operating range normally ranges from the base speed
to a speed that is about two or three times the base speed. When at base speed (full
voltage) and the field current is reduced, the motor increases in speed. In this region,
the power remains constant as speed increases. The increase in speed comes at the
expense of a reduction in the torque available to turn the load. Often this region is
labeled CP/VT for constant power/variable torque.
The take up rolls at the end of a paper machine operate using this field-weakening
range. Paper comes off the machine at a fixed speed. When a new roll is started, the
load on the spindle is the lightest (no paper), but must rotate fastest because it is at
its smallest diameter. At this point, the DC motor is in its full field-weakened mode —
torque is at a minimum but speed is at its greatest. As the roll fills with paper, it
requires more torque to turn the spindle — the load is increasing. The paper comes
Figure 2. Power developed by a DC motor. In the B region the DC motor develops constant
torque and the power varies with speed. In the F1 region power remains constant and
torque varies. In the F2 region both power and torque varies.
8. off the machine at a fixed speed — as the paper roll builds, the roll diameter
increases, and the spindle needs to turn slower to keep the roll’s linear surface
speed the same as the paper machine. When operating in the field-weakening
range, the field is strengthened as the roll builds, which increases torque and
decreases spindle speed. In the paper industry, DC motors were used on more or
less all of the machines that did some type of work with paper rolls. It was the field-
weakening characteristic that allowed this to be the case.
The third operating range is an extension of the field-weakening range. This
extended field-weakening range ranges from about four to five times the base speed.
As the field is further weakened for even greater speed, it gets more difficult for the
current to move between the brush and the commutator. If too much current is
flowing, there’s an excess of sparking at the bush-commutator junction, which
damages both components. Damage can be prevented at these higher speeds by
limiting the current flowing to the brushes. This region is defined as a third area
because now both power and torque are dependent on speed. Often, this region is
labeled VP/VT for variable power/variable torque.
The application to which this third operating range is applied is a harbor crane that
unloads containers from a ship. As anyone that was in the Navy knows, ships are
built to be at sea. A cargo vessel tied to a pier isn’t making money. As the harbor
crane is picking up the container and lifting it out of the hold, the DC motor is
operating in the first region, which allows full torque from zero to base speed. Once
the container is placed on the pier and off the hook, the torque needed to lift and get
the hook back into the hold for the next lift is a fraction of the lifting torque. During
this time, the DC motor operates in the third region, cutting the cycle time between
lifts to a minimum. The quicker the hook returns to the hold, the more containers that
can be unloaded (or loaded) in a given time period and the quicker the ship gets
back to making money.
“For almost 100 years, the industry was using one electrical technology
to get a variable-speed shaft.”
– Bob Simon M.Sc., P.E.
Traditionally, DC motors have had a smaller power density then the conventional
induction motor. That is to say, for a given power, the physical size of the DC motor
is smaller then the physical size of an equivalent AC induction motor. Smaller is
better, and when thinking about footprint, traditionally DC has a smaller one. This
also is true for the DC converter as compared to an AC inverter. An AC inverter
normally needs two bridges — one to perform a rectification and another to do the
inversion to the needed frequency. The DC converter needs only a rectification
bridge and is, therefore, smaller in size, has less heat losses and is less complex.
A smaller motor will have a smaller rotor. A smaller rotor means less inertia. DC
motors are used in applications with an operating cycle that includes acceleration
and deceleration. With less rotor inertia, it takes less time and power to accelerate or
decelerate. This allows for quicker reversals, shorter cycle times and faster
production.
9. Because of the potential to have a high power density, DC motors can push well into
the 2,000 hp, 3,000 hp, 4,000 hp and greater ranges. Standard low-voltage induction
motor power ranges end around 800 hp, 1,000 hp or 1,200 hp. If an application
requires both more power and an AC induction motor, the voltage jumps into the
medium-voltage ranges of 2,300 V or 4,160 V and even in the high-voltage range of
11 kV. Having a facility with these voltages requires a different level of equipment
capabilities and a knowledge and skill level not found in the average trade
electrician.
Current state of the technology
Getting back to the original question: DC motors, why are they still used? There are
two reasons. The first can be summed up in two words: installed base. Let's
remember that the DC motor was the primary variable-speed shaft-turning device
since 1888. When AC inverters and AC motors started to replace DC in machines
can be debated, so let’s put a stake in the ground and call it 1987. For almost 100
years, the industry was using one electrical technology to get a variable-speed shaft.
It takes a good number of acres of ocean to get an aircraft carrier running at a full
bell turned around and headed in the other direction.
Engineers, machine builders and maintenance staffs had and have knowledge of
DC. DC converters are simpler in design than AC inverters, lower in cost and easier
to repair. DC motors can be repaired repeatedly. If a piece of machinery is powered
by a DC converter and motor, and if either one should fail, it’s easier (and cheaper)
to replace the failed item then to convert the machine to AC. If a plant has 10
machines using DC and wants to order an 11th, there’ll be a strong bias to purchase
what has worked before.
During past several years, DC motor manufacturers’ ongoing R&D has concentrated
on redesigning the most maintenance-intensive section of the DC motor, which is the
commutator and brushes.
As design engineers continue to increase the power density for a given frame size,
the motor’s commutator gets smaller. As the circumference of the commutator
shrinks, there’s less brush wear with every turn of the rotor. Reduced brush wear
results in extended intervals between brush changes. Engineers also have
redesigned brush blocks, pressure fingers and springs to allow for longer brushes.
With longer brushes, the interval between brush changes extends further, providing
for longer periods of operation without a maintenance shutdown. DC motors can be
purchased with brush wear sensors, which warn that a brush is worn down to its
lowest level and requires changing. Brush wear sensors often prevent commutator
damage from a worn brush being left in too long and resulting in costly repairs.
Active research and development
With the DC motor being one of the oldest technologies, you’d think R&D has ended.
Many motor companies continue to offer their older designs and there are some that
have dropped the product completely. But, there are motor companies that continue
to invest in developing the technology. Using software modeling tools, engineers can
get a better understanding of both the magnetic flux and thermal flows in the motor
10. laminations. Companies with active R&D programs are incorporating developments
in insulating materials into their designs. Slight changes in lamination geometries,
metallurgy, and insulating materials allow for increased power density and smaller
motors.
Companies with active R&D also are helping to reduce maintenance costs by
extending brush life. This can be done by designing smaller commutators,
lengthening the brushes, adding brush wear sensors and making it easier to replace
brushes. Studying the brush/commutator junction is a never ending activity. There
are groups using the latest sensor and control technology to determine what is the
best environment (temperature, humidity, pressures) that leads to optimum junction
performance. They’re also asking what can be done to ensure the junction
environment is optimum at the locations and ambient environments in which the
motor operates.
Everyone has heard the story that in 1899, the head of the U.S. Patent Office sent
his resignation to President McKinley because, he said, “Everything that could be
invented has been invented.” This turned out to be untrue and so is the tale that DC
motors are no longer being used and no one is investing in research and
development. The applications available for the DC motor are fewer than in the past.
However, the operational characteristics of higher power density, low inertia and
higher speed ranges continue to make the DC motor the preferred choice for many
machine builders. Also, the magnitudes of the installed and knowledge bases cause
users to request DC motors as prime movers even on new equipment
…………………………………………………………………