# DIRECT CURRENT GENERATORS

Save this PDF as:

Size: px
Start display at page:

## Transcription

1 DIRECT CURRENT GENERATORS Revision 12:50 14 Nov 05 INTRODUCTION A generator is a machine that converts mechanical energy into electrical energy by using the principle of magnetic induction. This principle is explained as follows: Whenever a conductor is moved within a magnetic field in such a way that the conductor cuts across magnetic lines of flux, voltage is generated in the conductor. The AMOUNT of voltage generated depends on (1) the strength of the magnetic field, (2) the angle at which the conductor cuts the magnetic field, (3) the speed at which the conductor is moved, and (4) the length of the conductor within the magnetic field. The POLARITY of the voltage depends on the direction of the magnetic lines of flux and the direction of movement of the conductor. To determine the direction of current in a given situation, the RIGHT-HAND RULE FOR GENERATORS is used. This rule is explained in the following manner. Extend the thumb, forefinger, and middle finger of your right hand at right angles to one another. Point your thumb in the direction the conductor is being moved. Point your forefinger in the direction of magnetic flux (from north to south). Your middle finger will then point in the direction of current flow in an external circuit to which the voltage is applied.

2 THE ELEMENTARY GENERATOR The simplest elementary generator that can be built is an ac generator. Basic generating principles are most easily explained through the use of the elementary ac generator. For this reason, the ac generator will be discussed first. The dc generator will be discussed later. An elementary generator (fig. 1-2) consists of a wire loop placed so that it can be rotated in a stationary magnetic field. This will produce an induced emf in the loop. Sliding contacts (brushes) connect the loop to an external circuit load in order to pick up or use the induced emf.

3 The pole pieces (marked N and S) provide the magnetic field. The pole pieces are shaped and positioned as shown to concentrate the magnetic field as close as possible to the wire loop. The loop of wire that rotates through the field is called the ARMATURE. The ends of the armature loop are connected to rings called SLIP RINGS. They rotate with the armature. The brushes, usually made of carbon, with wires attached to them, ride against the rings. The generated voltage appears across these brushes. The elementary generator produces a voltage in the following manner (fig. 1-3). The armature loop is rotated in a clockwise direction. The initial or starting point is shown at position A. (This will be considered the zero-degree position.) At 0 the armature loop is perpendicular to the magnetic field. The black and white conductors of the loop are moving parallel to the field. The instant the conductors are moving parallel to the magnetic field, they do not cut any lines of flux. Therefore, no emf is induced in the conductors, and the meter at position A indicates zero. This position is called the NEUTRAL PLANE. As the armature loop rotates from position A (0 ) to position B (90 ), the conductors cut through more and more lines of flux, at a continually increasing angle. At 90 they are cutting through a maximum number of lines of flux and at maximum angle. The result is that between 0 and 90, the induced emf in the conductors builds up from zero to a maximum value. Observe that from 0 to 90, the black conductor cuts DOWN through the field. At the same time the white conductor cuts UP through the field. The induced emfs in the conductors are series-adding. This means the resultant voltage across the brushes (the terminal voltage) is the sum of the two induced voltages. The meter at position B reads maximum value. As the armature loop continues rotating from 90 (position B) to 180 (position C), the conductors which were cutting through a maximum number of lines of flux at position B now cut through fewer lines. They are again moving parallel to the magnetic field at position C. They no longer cut through any lines of flux. As the armature rotates from 90 to 180, the induced voltage will decrease to zero in the same manner that it increased during the rotation from 0 to 90. The meter again reads zero. From 0 to 180 the conductors of the armature loop have been moving in the same direction through the magnetic field. Therefore, the polarity of the induced voltage has remained the same. This is shown by points A through C on the graph. As the loop rotates beyond 180 (position C), through 270 (position D), and back to the initial or starting point (position A), the direction of the cutting action of the conductors through the magnetic field reverses. Now the black conductor cuts UP through the field while the white conductor cuts DOWN through the field. As a result, the polarity of the induced voltage reverses. Following the sequence shown by graph points C, D, and back to A, the voltage will be in the direction opposite to that shown from points A, B, and C. The terminal voltage will be the same as it was from A to C except that the polarity is reversed (as shown by the meter deflection at position D). The voltage output waveform for the complete revolution of the loop is shown on the graph in figure 1-3.

4 Figure 1-3. Output voltage of an elementary generator during one revolution. THE ELEMENTARY DC GENERATOR A single-loop generator with each terminal connected to a segment of a two-segment metal ring is shown in figure 1-4. The two segments of the split metal ring are insulated from each other. This forms a simple COMMUTATOR. The commutator in a dc generator replaces the slip rings of the ac generator. This is the main difference in their construction. The commutator mechanically reverses the armature loop connections to the external circuit. This occurs at the same instant that the polarity of the voltage in the armature loop reverses. Through this process the commutator changes the generated ac voltage to a pulsating dc voltage as shown in the graph of figure 1-4. This action is known as commutation. Commutation is described in detail later in this chapter.

5 Figure 1-4. Effects of commutation. For the remainder of this discussion, refer to figure 1-4, parts A through D. This will help you in following the step-by-step description of the operation of a dc generator. When the armature loop rotates clockwise from position A to position B, a voltage is induced in the armature loop which causes a current in a direction that deflects the meter to the right. Current flows through loop, out of the positive brush, through the meter and the load, and back through the negative brush to the loop. Voltage reaches its maximum value at point B on the graph for reasons explained earlier. The generated voltage and the current fall to zero at position C. At this instant each brush makes contact with both segments of the commutator. As the armature loop rotates to position D, a voltage is again induced in the loop. In this case, however, the voltage is of opposite polarity. The voltages induced in the two sides of the coil at position D are in the reverse direction to that of the voltages shown at position B. Note that the current is flowing from the black side to the white side in position B and from the white side to the black side in position D. However, because the segments of the commutator have rotated with the loop and are contacted by opposite brushes, the direction of current flow through the brushes and the meter remains the same as at position B. The voltage developed across the brushes is pulsating and unidirectional (in one direction only). It varies twice during each revolution between zero and maximum. This variation is called RIPPLE. A pulsating voltage, such as that produced in the preceding description, is unsuitable for most applications. Therefore, in practical generators more armature loops (coils) and more commutator segments are used to produce an output voltage waveform with less ripple.

7 ELECTROMAGNETIC POLES Nearly all practical generators use electromagnetic poles instead of the permanent magnets used in our elementary generator. The electromagnetic field poles consist of coils of insulated copper wire wound on soft iron cores, as shown in figure 1-6. The main advantages of using electromagnetic poles are (1) increased field strength and (2) a means of controlling the strength of the fields. By varying the input voltage, the field strength is varied. By varying the field strength, the output voltage of the generator can be controlled. Figure 1-6. Four-pole generator (without armature). Q9. How can field strength be varied in a practical dc generator? COMMUTATION Commutation is the process by which a dc voltage output is taken from an armature that has an ac voltage induced in it. You should remember from our discussion of the elementary dc generator that the commutator mechanically reverses the armature loop connections to the external circuit. This occurs at the same instant that the voltage polarity in the armature loop reverses. A dc voltage is applied to the load because the output connections are reversed as each commutator segment passes under a brush. The segments are insulated from each other. In figure 1-7, commutation occurs simultaneously in the two coils that are briefly short-circuited by the brushes. Coil B is short-circuited by the negative brush. Coil Y, the opposite coil, is short-circuited by the positive brush. The brushes are positioned on the commutator so that each coil is short-circuited as it moves through its own electrical neutral plane. As you have seen previously, there is no voltage generated in the coil at that time. Therefore, no sparking can occur between the commutator and the brush. Sparking between the brushes and the commutator is an indication of improper commutation. Improper brush placement is the main cause of improper commutation.

8 Figure 1-7. Commutation of a dc generator. ARMATURE LOSSES In dc generators, as in most electrical devices, certain forces act to decrease the efficiency. These forces, as they affect the armature, are considered as losses and may be defined as follows: 1. I 2 R, or copper loss in the winding 2. Eddy current loss in the core 3. Hysteresis loss (a sort of magnetic friction)

9 Copper Losses The power lost in the form of heat in the armature winding of a generator is known as COPPER LOSS. Heat is generated any time current flows in a conductor. Copper loss is an I 2 R loss, which increases as current increases. The amount of heat generated is also proportional to the resistance of the conductor. The resistance of the conductor varies directly with its length and inversely with its crosssectional area. Copper loss is minimized in armature windings by using large diameter wire. Eddy Current Losses The core of a generator armature is made from soft iron, which is a conducting material with desirable magnetic characteristics. Any conductor will have currents induced in it when it is rotated in a magnetic field. These currents that are induced in the generator armature core are called EDDY CURRENTS. The power dissipated in the form of heat, as a result of the eddy currents, is considered a loss. Eddy currents, just like any other electrical currents, are affected by the resistance of the material in which the currents flow. The resistance of any material is inversely proportional to its cross-sectional area. Figure 1-11, view A, shows the eddy currents induced in an armature core that is a solid piece of soft iron. Figure 1-11, view B, shows a soft iron core of the same size, but made up of several small pieces insulated from each other. This process is called lamination. The currents in each piece of the laminated core are considerably less than in the solid core because the resistance of the pieces is much higher. (Resistance is inversely proportional to cross-sectional area.) The currents in the individual pieces of the laminated core are so small that the sum of the individual currents is much less than the total of eddy currents in the solid iron core. Figure Eddy currents in dc generator armature cores.

10 As you can see, eddy current losses are kept low when the core material is made up of many thin sheets of metal. Laminations in a small generator armature may be as thin as 1/64 inch. The laminations are insulated from each other by a thin coat of lacquer or, in some instances, simply by the oxidation of the surfaces. Oxidation is caused by contact with the air while the laminations are being annealed. The insulation value need not be high because the voltages induced are very small. Most generators use armatures with laminated cores to reduce eddy current losses. Hysteresis Losses Hysteresis loss is a heat loss caused by the magnetic properties of the armature. When an armature core is in a magnetic field, the magnetic particles of the core tend to line up with the magnetic field. When the armature core is rotating, its magnetic field keeps changing direction. The continuous movement of the magnetic particles, as they try to align themselves with the magnetic field, produces molecular friction. This, in turn, produces heat. This heat is transmitted to the armature windings. The heat causes armature resistances to increase. To compensate for hysteresis losses, heat-treated silicon steel laminations are used in most dc generator armatures. After the steel has been formed to the proper shape, the laminations are heated and allowed to cool. This annealing process reduces the hysteresis loss to a low value. FIELD EXCITATION When a dc voltage is applied to the field windings of a dc generator, current flows through the windings and sets up a steady magnetic field. This is called FIELD EXCITATION. This excitation voltage can be produced by the generator itself or it can be supplied by an outside source, such as a battery. A generator that supplies its own field excitation is called a SELF-EXCITED GENERATOR. Self-excitation is possible only if the field pole pieces have retained a slight amount of permanent magnetism, called RESIDUAL MAGNETISM. When the generator starts rotating, the weak residual magnetism causes a small voltage to be generated in the armature. This small voltage applied to the field coils causes a small field current. Although small, this field current strengthens the magnetic field and allows the armature to generate a higher voltage. The higher voltage increases the field strength, and so on. This process continues until the output voltage reaches the rated output of the generator. CLASSIFICATION OF GENERATORS Self-excited generators are classed according to the type of field connection they use. There are three general types of field connections SERIES-WOUND, SHUNT-WOUND (parallel), and COMPOUND-WOUND. Compound-wound generators are further classified as cumulativecompound and differential-compound. These last two classifications are not discussed in this chapter. Series-Wound Generator In the series-wound generator, shown in figure 1-15, the field windings are connected in series with the armature. Current that flows in the armature flows through the external circuit and through the field windings. The external circuit connected to the generator is called the load circuit.

12 Generated Voltage Voltage generated in a DC machine is given by EA = kφ N Where E A is the generated voltage, φ is a measure of magnetic flux, N is the shaft s speed in RPM and k is a constant related to the physical construction of the motor (i.e. number of poles, conductors and windings). The generated voltage (E A ) can be increased by increasing magnetic flux or the machine s speed of rotation. The terminal voltage produced by a DC generator is always less the generated voltage due to losses in the armature windings. This can be seen in the example below. The current through the field and armature are I F = V/R = 120 V / 100 Ω = 1.2 A and I A = 5 A A = 6.2 A respectively. The voltage lost in the armature winding is V = IR = (6.2A)(5 Ω) = 31 V. This leads to a generated voltage of E A = 151 V required to produce a terminal voltage of 120 V across the load. Voltage Regulation In order to control generator output voltage, a rheostat (variable resistor) can be added in series with the field winding. This variable resistance can be used to control the current flow through the field windings and thus the strength of the generated voltage. A second method for controlling output voltage is to change the rate at which the armature is spinning. As the armature spins faster through the shunt coil s magnetic field, output voltage increases. The regulation of a generator refers to the VOLTAGE CHANGE that takes place when the load changes. It is usually expressed as the change in voltage from a no-load condition to a full-load condition, and is expressed as a percentage of full-load. It is expressed in the following formula: where E nl is the no-load terminal voltage and E fl is the full-load terminal voltage of the generator. For example, to calculate the percent of regulation of a generator with a no-load voltage of 462

13 volts and a full-load voltage of 440 volts: Given: No-load voltage 462 V Full-load voltage 440 V NOTE: The lower the percent of regulation, the better the generator. In the above example, the 5% regulation represented a 22-volt change from no load to full load. A 1% change would represent a change of 4.4 volts, which, of course, would be better. VOLTAGE CONTROL Voltage control is either (1) manual or (2) automatic. In most cases the process involves changing the resistance of the field circuit. By changing the field circuit resistance, the field current is controlled. Controlling the field current permits control of the output voltage. The major difference between the various voltage control systems is merely the method by which the field circuit resistance and the current are controlled. VOLTAGE REGULATION should not be confused with VOLTAGE CONTROL. As described previously, voltage regulation is an internal action occurring within the generator whenever the load changes. Voltage control is an imposed action, usually through an external adjustment, for the purpose of increasing or decreasing terminal voltage. Efficiency and Power Some losses occur during the conversion from mechanical energy to electrical energy in a DC shunt generator. These losses are due to both mechanical effects (friction, drag) and electrical effects (resistance). The power lost can be computed given using following equation. Pout = Pin Plost The percent efficiency of a motor is given by the following equation.

14 Pout % η = x 100 Pin Mechanical power is frequently stated in horsepower. To convert from horsepower to watts, use 1 horsepower = 746 watt Example Problem A 5 hp gasoline motor is used to turn a DC shunt generator that delivers 120 V and 25 A to a load. Find the total power lost in the generator. Determine the generator s efficiency. Power Generated = V * I = 120 V * 25 A = 3000 W Power Supplied = 5 hp = 5 * 746 W / 1 hp = 3730 W Power Lost = Power Supplied Power Generated = 3730 W 3000 W = 730 W Power Efficiency = 100 * 3000 / 3730 = 80.4% GENERATOR CONSTRUCTION Figure 1-19, views A through E, shows the component parts of dc generators. Figure 1-20 shows the entire generator with the component parts installed. The cutaway drawing helps you to see the physical relationship of the components to each other.

15 Figure Components of a dc generator. Figure Construction of a dc generator (cutaway drawing).

16 Definitions Stator outer, stationary portion of the machine. Rotor rotating portion of the machine which revolves inside the stator. Field Winding wire coil with the sole purpose of providing a magnetic field. Armature portion of the machine where energy conversion occurs (rotor for DC machines). Commutator conducting segments mounted on the machine s shaft and insulated from one another. Brushes devices used to maintain sliding contact with the commutator.

### DC Generators and Motors

DC Generators and Motors Course No: E04-008 Credit: 4 PDH A. Bhatia Continuing Education and Development, Inc. 9 Greyridge Farm Court Stony Point, NY 10980 P: (877) 322-5800 F: (877) 322-4774 info@cedengineering.com

### DC GENERATOR THEORY. LIST the three conditions necessary to induce a voltage into a conductor.

DC Generators DC generators are widely used to produce a DC voltage. The amount of voltage produced depends on a variety of factors. EO 1.5 LIST the three conditions necessary to induce a voltage into

### Principles and Working of DC and AC machines

BITS Pilani Dubai Campus Principles and Working of DC and AC machines Dr Jagadish Nayak Constructional features BITS Pilani Dubai Campus DC Generator A generator consists of a stationary portion called

### Chapter 4: DC Generators

Chapter 4: DC Generators Creating an AC Voltage The voltage produced in a DC generator is inherently AC and only becomes DC after rectification Consider an AC generator, consisting of a coil on the rotor

### 2. A conductor of length 2m moves at 4m/s at 30 to a uniform magnetic field of 0.1T. Which one of the following gives the e.m.f. generated?

Extra Questions - 2 1. A straight length of wire moves through a uniform magnetic field. The e.m.f. produced across the ends of the wire will be maximum if it moves: a) along the lines of magnetic flux

### Lab 8: DC generators: shunt, series, and compounded.

Lab 8: DC generators: shunt, series, and compounded. Objective: to study the properties of DC generators under no-load and full-load conditions; to learn how to connect these generators; to obtain their

### Experiment 1 The DC Machine

Experiment 1 The DC Machine ECEN 4517 R. W. Erickson and D. Maksimovic The purpose of this experiment is to become familiar with operating principles, equivalent circuit models, and basic characteristics

### Question Bank. 1. Electromagnetism 2. Magnetic Effects of an Electric Current 3. Electromagnetic Induction

1. Electromagnetism 2. Magnetic Effects of an Electric Current 3. Electromagnetic Induction 1. Diagram below shows a freely suspended magnetic needle. A copper wire is held parallel to the axis of magnetic

### Motor Fundamentals. DC Motor

Motor Fundamentals Before we can examine the function of a drive, we must understand the basic operation of the motor. It is used to convert the electrical energy, supplied by the controller, to mechanical

### Equipment: Power Supply, DAI, Wound rotor induction motor (8231), Electrodynamometer (8960), timing belt.

Lab 13: Wound rotor induction motor. Objective: to examine the construction of a 3-phase wound rotor induction motor; to understand exciting current, synchronous speed and slip in this motor; to determine

### Chapter 22: Electric motors and electromagnetic induction

Chapter 22: Electric motors and electromagnetic induction The motor effect movement from electricity When a current is passed through a wire placed in a magnetic field a force is produced which acts on

### Equipment: Power Supply, DAI, Universal motor (8254), Electrodynamometer (8960), timing belt.

Lab 12: The universal motor. Objective: to examine the construction of the universal motor; to determine its no-load and full-load characteristics while operating on AC; to determine its no-load and full-load

### Chapter 4: DC Generators. 9/8/2003 Electromechanical Dynamics 1

Chapter 4: DC Generators 9/8/2003 Electromechanical Dynamics 1 Armature Reaction Current flowing in the armature coils creates a powerful magnetomotive force that distorts and weakens the flux coming from

### Motors and Generators

Motors and Generators Electro-mechanical devices: convert electrical energy to mechanical motion/work and vice versa Operate on the coupling between currentcarrying conductors and magnetic fields Governed

### Lab 14: 3-phase alternator.

Lab 14: 3-phase alternator. Objective: to obtain the no-load saturation curve of the alternator; to determine the voltage regulation characteristic of the alternator with resistive, capacitive, and inductive

### 1. The diagram below represents magnetic lines of force within a region of space.

1. The diagram below represents magnetic lines of force within a region of space. 4. In which diagram below is the magnetic flux density at point P greatest? (1) (3) (2) (4) The magnetic field is strongest

### Characteristics and Benefits

Defining Quality. Building Comfort. Characteristics and Benefits Characteristics and Benefits The two most common electronic devices to vary fan speed in HVAC equipment are the variable frequency drive

### GENERATORS AND MOTORS

GENERATORS AND MOTORS A device that converts mechanical energy (energy of motion windmills, turbines, nuclear power, falling water, or tides) into electrical energy is called an electric generator. The

### Brushless Motors: HOW DO THEY WORK?

Brushless Motors: HOW DO THEY WORK? Brushless DC motors are simple enough: magnets attached to a shaft are pushed and pulled by electromagnetic fields that are managed by an electronic speed control. This

### A Practical Guide to Free Energy Devices

A Practical Guide to Free Energy Devices Part 60: Last updated: 3rd February 2006 Author: Patrick J. Kelly Electrical power is frequently generated by spinning the shaft of a generator which has some arrangement

### MAGNETISM MAGNETISM. Principles of Imaging Science II (120)

Principles of Imaging Science II (120) Magnetism & Electromagnetism MAGNETISM Magnetism is a property in nature that is present when charged particles are in motion. Any charged particle in motion creates

### Name: Date: Regents Physics Mr. Morgante UNIT 4B Magnetism

Name: Regents Physics Date: Mr. Morgante UNIT 4B Magnetism Magnetism -Magnetic Force exists b/w charges in motion. -Similar to electric fields, an X stands for a magnetic field line going into the page,

### AC generator theory. Resources and methods for learning about these subjects (list a few here, in preparation for your research):

AC generator theory This worksheet and all related files are licensed under the Creative Commons Attribution License, version 1.0. To view a copy of this license, visit http://creativecommons.org/licenses/by/1.0/,

### Direct Current Motors

Direct Current Motors DC MOTORS The DC machine can operate as a generator and as a motor. Chap 5. Electrical Machines by Wildi, 6 e Lecturer: R. Alba-Flores Alfred State College Spring 2008 When a DC machine

### Understanding the Alternator

http://www.autoshop101.com THIS AUTOMOTIVE SERIES ON ALTERNATORS HAS BEEN DEVELOPED BY KEVIN R. SULLIVAN PROFESSOR OF AUTOMOTIVE TECHNOLOGY AT SKYLINE COLLEGE SAN BRUNO, CALIFORNIA ALL RIGHTS RESERVED

### DIRECT CURRENT GENERATORS

CHAPTER 18 DIRECT CURRENT GENERATORS INTRODUCTION Chapters 18 and 19 provide a comprehensive compilation of nearly 40 years of DC machines and procedures. The DC principles presented here are still valid

### Chapter 14 Magnets and

Chapter 14 Magnets and Electromagnetism How do magnets work? What is the Earth s magnetic field? Is the magnetic force similar to the electrostatic force? Magnets and the Magnetic Force! We are generally

### Inductance. Motors. Generators

Inductance Motors Generators Self-inductance Self-inductance occurs when the changing flux through a circuit arises from the circuit itself. As the current increases, the magnetic flux through a loop due

### The purposes of this experiment are to test Faraday's Law qualitatively and to test Lenz's Law.

260 17-1 I. THEORY EXPERIMENT 17 QUALITATIVE STUDY OF INDUCED EMF Along the extended central axis of a bar magnet, the magnetic field vector B r, on the side nearer the North pole, points away from this

### Induction Motor Theory

PDHonline Course E176 (3 PDH) Induction Motor Theory Instructor: Jerry R. Bednarczyk, P.E. 2012 PDH Online PDH Center 5272 Meadow Estates Drive Fairfax, VA 22030-6658 Phone & Fax: 703-988-0088 www.pdhonline.org

### Extra Questions - 1. 1. What current will flow in a 20Ω resistor when it is connected to a 50V supply? a) 0.4A b) 1.6A c) 2.5A

Extra Questions - 1 1. What current will flow in a 20Ω resistor when it is connected to a 50V supply? a) 0.4A b) 1.6A c) 2.5A 2. A current of 500mA flows in a resistance of 12Ω. What power is dissipated

### 8 Speed control of Induction Machines

8 Speed control of Induction Machines We have seen the speed torque characteristic of the machine. In the stable region of operation in the motoring mode, the curve is rather steep and goes from zero torque

### Copper and Electricity: Generation

PHYSICS Copper and Electricity: Generation (Electromagnetic Induction) 16-18 YEARS Below are different sections of this e-source, for quick navigation. Electricity from Movement What is Induction? Flux

### Preview of Period 16: Motors and Generators

Preview of Period 16: Motors and Generators 16.1 DC Electric Motors What causes the rotor of a motor to spin? 16.2 Simple DC Motors What causes a changing magnetic field in the simple coil motor? 16.3

### BASANT S SCIENCE ACADEMY STUDY MATERIAL MAGNETIC EFFECT OF CURRENT

BASANT S SCIENCE ACADEMY Why does a compass needle get deflected when brought near a bar magnet? A compass needle is a small bar magnet. When it is brought near a bar magnet, its magnetic field lines interact

### Basics of Electricity

Basics of Electricity Generator Theory PJM State & Member Training Dept. PJM 2014 8/6/2013 Objectives The student will be able to: Describe the process of electromagnetic induction Identify the major components

### AC Motors. Siemens STEP 2000 Course. STEP 2000 Courses distributed by

Siemens STEP 2000 Course AC Motors It's easy to get in STEP! Download any course. Hint: Make sure you download all parts for each course and the test answer form. Complete each chapter and its review section

### Electromagnetic Induction - A

Electromagnetic Induction - A APPARATUS 1. Two 225-turn coils 2. Table Galvanometer 3. Rheostat 4. Iron and aluminum rods 5. Large circular loop mounted on board 6. AC ammeter 7. Variac 8. Search coil

### In order to get the G.C.S.E. grade you are capable of, you must make your own revision notes using your Physics notebook.

In order to get the G.C.S.E. grade you are capable of, you must make your own revision notes using your Physics notebook. When summarising notes, use different colours and draw diagrams/pictures. If you

### AC Generators and Motors

AC Generators and Motors Course No: E03-008 Credit: 3 PDH A. Bhatia Continuing Education and Development, Inc. 9 Greyridge Farm Court Stony Point, NY 10980 P: (877) 322-5800 F: (877) 322-4774 info@cedengineering.com

### SECTION 4 ELECTRIC MOTORS UNIT 17: TYPES OF ELECTRIC MOTORS

SECTION 4 ELECTRIC MOTORS UNIT 17: TYPES OF ELECTRIC MOTORS UNIT OBJECTIVES After studying this unit, the reader should be able to Describe the different types of open single-phase motors used to drive

### CPO Electric Motor Equipment Module

CPO Electric Motor Equipment Module Equipment Includes: 5 switch plates 1 electric motor body with permanent turn-crank 1 ew high-output electromagnet motor modules (Black) 1 electromagnet generator modules

### DHANALAKSHMI COLLEGE OF ENGINEERING DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING EE2302 - ELECTRICAL MACHINES II UNIT-I SYNCHRONOUS GENERATOR

1 DHANALAKSHMI COLLEGE OF ENGINEERING DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING Constructional details Types of rotors EE2302 - ELECTRICAL MACHINES II UNIT-I SYNCHRONOUS GENERATOR PART A 1.

### Simple Analysis for Brushless DC Motors Case Study: Razor Scooter Wheel Motor

Simple Analysis for Brushless DC Motors Case Study: Razor Scooter Wheel Motor At first glance, a brushless direct-current (BLDC) motor might seem more complicated than a permanent magnet brushed DC motor,

### THE LUCAS C40 DYNAMO & ITS ARMATURE.

THE LUCAS C40 DYNAMO & ITS ARMATURE. H. Holden, March 2011. The Dynamo as a DC generating machine was used extensively in the pre- Alternator era, from the early 1900 s up to the late 1960 s and early

### The DC Motor/Generator Commutation Mystery. Commutation and Brushes. DC Machine Basics

The DC Motor/Generator Commutation Mystery One small, yet vital piece of the DC electric motor puzzle is the carbon brush. Using the correct carbon brush is a key component for outstanding motor life,

### ELECTRODYNAMICS 05 AUGUST 2014

ELECTRODYNAMICS 05 AUGUST 2014 In this lesson we: Lesson Description Discuss the motor effect Discuss how generators and motors work. Summary The Motor Effect In order to realise the motor effect, the

### Chapter 4. Magnetic Materials and Circuits

Chapter 4 Magnetic Materials and Circuits Objectives List six characteristics of magnetic field. Understand the right-hand rule for current and magnetic fluxes. Define magnetic flux, flux density, magnetomotive

### Equipment: Power Supply, DAI, Split-phase/Capacitor start motor (8251), Electrodynamometer (8960), timing belt.

Lab 10: Split-phase induction motor. Objective: to examine the construction of the split-phase motor; to learn its wiring connections; to observe its starting and running operations; to measure its starting

### UNIT 3 AUTOMOBILE ELECTRICAL SYSTEMS

UNIT 3 AUTOMOBILE ELECTRICAL SYSTEMS Automobile Electrical Structure 3.1 Introduction Objectives 3.2 Ignition System 3.3 Requirement of an Ignition System 3.4 Types of Ignition 3.4.1 Battery or Coil Ignition

### Level 2 Physics: Demonstrate understanding of electricity and electromagnetism

Level 2 Physics: Demonstrate understanding of electricity and electromagnetism Static Electricity: Uniform electric field, electric field strength, force on a charge in an electric field, electric potential

### How do you measure voltage and current in electric circuits? Materials

20A Electricity How do you measure voltage and current in electric circuits? Electricity Investigation 20A We use electricity every day, nearly every minute! In this Investigation you will build circuits

### 1. Title Electrical fundamentals II (Mechanics Repair and Maintenance)

1. Title Electrical fundamentals II (Mechanics Repair and Maintenance) 2. Code EMAMBG429A 3. Range The knowledge is needed for a wide range of aircraft repair and maintenance works,e.g. applicable to aircrafts,

### Parallel Path Magnetic Technology for High Efficiency Power Generators and Motor Drives

Parallel Path Magnetic Technology for High Efficiency Power Generators and Motor Drives Patents & Copyright - Flynn Research, Greenwood MO, 64034 PARALLEL PATH MAGNETIC TECHNOLOGY (PPMT) BACKGROUND Parallel

### Equipment: Power Supply, DAI, Synchronous motor (8241), Electrodynamometer (8960), Tachometer, Timing belt.

Lab 9: Synchronous motor. Objective: to examine the design of a 3-phase synchronous motor; to learn how to connect it; to obtain its starting characteristic; to determine the full-load characteristic of

### Introduction. Upon completion of Basics of AC Motors you should be able to:

Table of Contents Introduction...2 AC Motors...4 Force and Motion...6 AC Motor Construction... 12 Magnetism... 17 Electromagnetism... 19 Developing a Rotating Magnetic Field...24 Rotor Rotation...29 Motor

### The Polyphase Induction Motor

Experiment No. 4 The Polyphase Induction Motor The polyphase induction motor is the most commonly used industrial motor, finding application in many situations where speed regulation is not essential.

### NZQA registered unit standard version 4 Page 1 of 5

Page 1 of 5 Title Apply electromagnetic theory to a range of problems Level 2 Credits 5 Purpose This unit standard covers knowledge of electromagnetism theory and is intended for people working in or intending

### Introduction to Electricity & Magnetism. Dr Lisa Jardine-Wright Cavendish Laboratory

Introduction to Electricity & Magnetism Dr Lisa Jardine-Wright Cavendish Laboratory Examples of uses of electricity Christmas lights Cars Electronic devices Human body Electricity? Electricity is the presence

### EDEXCEL NATIONAL CERTIFICATE/DIPLOMA UNIT 5 - ELECTRICAL AND ELECTRONIC PRINCIPLES NQF LEVEL 3. OUTCOME 3 - MAGNETISM and INDUCTION

EDEXCEL NATIONAL CERTIFICATE/DIPLOMA UNIT 5 - ELECTRICAL AND ELECTRONIC PRINCIPLES NQF LEVEL 3 OUTCOME 3 - MAGNETISM and INDUCTION 3 Understand the principles and properties of magnetism Magnetic field:

### Single-Phase AC Induction Squirrel Cage Motors. Permanent Magnet Series Wound Shunt Wound Compound Wound Squirrel Cage. Induction.

FAN ENGINEERING Information and Recommendations for the Engineer FE-1100 Single-Phase AC Induction Squirrel Cage Motors Introduction It is with the electric motor where a method of converting electrical

### Energy Systems Engineering Technology

College of Technology Motors and Controls Module # 2 Solenoids, DC Generators and DC Motors Document Intent: The intent of this document is to provide an example of how a subject matter expert might teach

### COMPUTER AIDED ELECTRICAL DRAWING (CAED) 10EE65

COMPUTER AIDED ELECTRICAL DRAWING (CAED) EE Winding Diagrams: (i) DC Winding diagrams (ii) AC Winding Diagrams Terminologies used in winding diagrams: Conductor: An individual piece of wire placed in the

### 10.2 Electromagnets. What is an electromagnet? Chapter 10

In the last section you learned about permanent magnets and magnetism. There is another type of magnet, one that is created by electric current. This type of magnet is called an. What is an? Why do magnets

### What is a transformer and how does it work?

Why is a transformer needed? A control transformer is required to supply voltage to a load which requires significantly more current when initially energized than under normal steady state operating conditions.

### TRANSFORMERS INTRODUCTION

Tyco Electronics Corporation Crompton Instruments 1610 Cobb International Parkway, Unit #4 Kennesaw, GA 30152 Tel. 770-425-8903 Fax. 770-423-7194 TRANSFORMERS INTRODUCTION A transformer is a device that

### Introduction. Three-phase induction motors are the most common and frequently encountered machines in industry

Induction Motors Introduction Three-phase induction motors are the most common and frequently encountered machines in industry - simple design, rugged, low-price, easy maintenance - wide range of power

### Linear DC Motors. 15.1 Magnetic Flux. 15.1.1 Permanent Bar Magnets

Linear DC Motors The purpose of this supplement is to present the basic material needed to understand the operation of simple DC motors. This is intended to be used as the reference material for the linear

### MAGNETIC EFFECTS OF ELECTRIC CURRENT

CHAPTER 13 MAGNETIC EFFECT OF ELECTRIC CURRENT In this chapter, we will study the effects of electric current : 1. Hans Christian Oersted (1777-1851) Oersted showed that electricity and magnetism are related

### The Effects of Airgap Flux Density on Permanent Magnet Brushless Servo Motor Design

The Effects of Airgap Flux Density on Permanent Magnet Brushless Servo Motor Design Lowell Christensen VP Engineering TruTech Specialty Motors Magnetics 2013 Orlando Florida Feb 8 & 9, 2013 This presentation

### ELECTRICITY & ELECTROMAGNETISM TRANSFORMERS + ETC

Circuitry, Formulas & Electricity Ch5 Bushong RT 244 12 Lect # 3 1 RT 244 WEEK 10 rev 2012 2 LECTURE # 3 ELECTRICITY & ELECTROMAGNETISM TRANSFORMERS + ETC BUSHONG CH. 4 & 5 REF: CARLTONS CH 3, 4 & 5 &

### Chapter 5 TRANSFORMERS

Chapter 5 TRANSFORMERS Objective Understand the transformer nameplate Describe the basic construction features of a transformer. Explain the relationship between voltage, current, impedance, and power

### Prof. Krishna Vasudevan, Prof. G. Sridhara Rao, Prof. P. Sasidhara Rao. x x. x x. Figure 10: Cross sectional view

4 Armature Windings Main field Commutator & Brush Compole field haft v Compensating winding Armature winding Yoke Figure 10: Cross sectional view Fig. 10 gives the cross sectional view of a modern d.c.

### DC generator theory. Resources and methods for learning about these subjects (list a few here, in preparation for your research):

DC generator theory This worksheet and all related files are licensed under the Creative Commons Attribution License, version 1.0. To view a copy of this license, visit http://creativecommons.org/licenses/by/1.0/,

### Chen. Vibration Motor. Application note

Vibration Motor Application note Yangyi Chen April 4 th, 2013 1 Table of Contents Pages Executive Summary ---------------------------------------------------------------------------------------- 1 1. Table

### SYNCHRONOUS MACHINES

SYNCHRONOUS MACHINES The geometry of a synchronous machine is quite similar to that of the induction machine. The stator core and windings of a three-phase synchronous machine are practically identical

### 13 ELECTRIC MOTORS. 13.1 Basic Relations

13 ELECTRIC MOTORS Modern underwater vehicles and surface vessels are making increased use of electrical actuators, for all range of tasks including weaponry, control surfaces, and main propulsion. This

### Lesson 11 Faraday s Law of Induction

Lesson 11 Faraday s Law of Induction Lawrence B. Rees 006. You may make a single copy of this document for personal use without written permission. 11.0 Introduction In the last lesson, we introduced Faraday

### Chapter 21 Electromagnetic Induction and Faraday s Law

Lecture PowerPoint Chapter 21 Physics: Principles with Applications, 6 th edition Giancoli Chapter 21 Electromagnetic Induction and Faraday s Law 2005 Pearson Prentice Hall This work is protected by United

### USER MANUAL DC TORQUE MOTOR

USER MANUAL DC ORQUE MOOR he present manual shows an opportunity for the servomechanisms builders of choosing the DC torque motors, with high performances, low price and immediate delivery. ICE SA Department

### maxon EC motor An introduction to brushless DC motors

This presentation introduces the design and operation principle of the brushless maxon EC motors. EC motors are also called brushless DC (BLDC) motors. In a first part we show the basic designs of brushless

### Figure Notional Portion of a Shipboard Electric Power Generation System

AC SYCHROOUS GEERATORS Why do we study AC synchronous generators? The short answer is that 3-phase AC generators are the workhorse of the power generation arena. Why? They are not as power limited as DC

### STUDY GUIDE: ELECTRICITY AND MAGNETISM

319 S. Naperville Road Wheaton, IL 60187 www.questionsgalore.net Phone: (630) 580-5735 E-Mail: info@questionsgalore.net Fax: (630) 580-5765 STUDY GUIDE: ELECTRICITY AND MAGNETISM An atom is made of three

### How Does a Generator Work?

How Does a Generator Work? Clifford Power Systems is one of the largest full service generator providers in the United States. Our generator experts specialize in equipment, service, parts and rental of

### MOTIONLESS ELECTRIC GENERATOR DESIGN BASED ON PERMANENT MAGNETS AND MAGNETIC AMPLIFIER

12/28/2009 MOTIONLESS ELECTRIC GENERATOR DESIGN BASED ON PERMANENT MAGNETS AND MAGNETIC AMPLIFIER FEDERALLY SPONSOR RESEARCH Not Applicable BACKGROUND - Field [0001] This application relates to motionless

### SERVICE SHOP NOTES. Use ohmmeter to check the resistance between the leads.

SERVICE SHOP NOTES LIMA 7 MAC SELF VOLTAGE REGULATED GENERATORS Troubleshooting Tips Engine bogs down or stalls even at no load. Problem: Main stator has one or more taps wound or connected incorrectly.

### Lecture Note. ForJune. Principal of electrical machinery and optimization of electrical power

Lecture Note ForJune Principal of electrical machinery and optimization of electrical power SuthipongThanasansakorn Southeast Asia Fishery Development Center, Training Department Thailand June 2010 Part

### DC generator theory. Resources and methods for learning about these subjects (list a few here, in preparation for your research):

DC generator theory This worksheet and all related files are licensed under the Creative Commons Attribution License, version 1.0. To view a copy of this license, visit http://creativecommons.org/licenses/by/1.0/,

### Chapter 3: AC and DC Motors DC Motors: General Principles of Operation 83. Most DC motors also carry one of three duty ratings:

Chapter 3: AC and DC Motors DC Motors: General Principles of Operation 83 Amps/field amps: designations for armature and field winding amps, respectively. These ratings are needed when programming the

### Unit 33 Three-Phase Motors

Unit 33 Three-Phase Motors Objectives: Discuss the operation of wound rotor motors. Discuss the operation of selsyn motors. Discuss the operation of synchronous motors. Determine the direction of rotation

### Induced voltages and Inductance Faraday s Law

Induced voltages and Inductance Faraday s Law concept #1, 4, 5, 8, 13 Problem # 1, 3, 4, 5, 6, 9, 10, 13, 15, 24, 23, 25, 31, 32a, 34, 37, 41, 43, 51, 61 Last chapter we saw that a current produces a magnetic

### Electrical Machines II. Week 1: Construction and theory of operation of single phase transformer

Electrical Machines II Week 1: Construction and theory of operation of single phase transformer Transformers Overview A transformer changes ac electric power at one frequency and voltage level to ac electric

### With Zero Emission and Human Powered Vehicles

Powering the Future With Zero Emission and Human Powered Vehicles Antoni Garcia Espinosa UPC CONTROL OF BRUSHLESS PERMANENT MAGNET MACHINES (BLDC) Powering the Future With Zero Emission and Human Powered

### Chapter 25 Practice Problems, Review, and Assessment

Chapter 25 Practice Problems, Review, and Assessment Section 1 Inducing Currents: Practice Problems 1. You move a straight wire that is 0.5 m long at a speed of 20 m/s vertically through a 0.4-T magnetic

### Revision Calcs. 1. The flux produced by a magnet is 10mWb. Determine the flux density if the area of the pole is 250 mm 2

EMA Revision Calcs Miller College Revision Calcs Revision Calcs 1. The flux produced by a magnet is 10mWb. Determine the flux density if the area of the pole is 250 mm 2 2. For the magnet in the previous

### The Synchronous Machine

Experiment No. 5 The Synchronous Machine Synchronous ac machines find application as motors in constant speed applications and, when interfaced to the power source with a variable-frequency converter system,

### Teacher Content Brief

Teacher Content Brief Electric Motors Introduction Motors convert electric energy into mechanical energy. This mechanical energy turns the propellers on your Sea Perch. But what makes a motor spin? To

### 2. TRANSFORMERS. The main learning objectives for this chapter are listed below. Use equivalent circuits to determine voltages and currents.

. TRANSFORMERS Transformers are commonly used in applications which require the conversion of AC voltage from one voltage level to another. There are two broad categories of transformers: electronic transformers,