Working Principle of Electric Generator

When a conductor moves in a magnetic field, an emf is induced across the conductor. This is the only basis on which each and every rotating electric generator works. Let us discuss the matter in a little bit details so that we can easily understand how does an electrical generator actually work. According to Faraday's law of electromagnetic induction, when a conductor links with a changing flux, it will have an induced emf across it. The value of induced emf across the conductor depends on the rate of change of flux linkage with the conductor. 

The direction of the induced emf in the conductor can be determined by Fleming's Right Hand Rule. This rule says that on your right hand if you stretch your thumb, first finger and second finger perpendicular to each other, and if you align your right hand thumb along the direction of motion of the conductor in the magnetic field, and first finger along the direction of magnetic field, then you second finger indicates the direction of emf in the conductor. 

Now we will show you how does electricity get produced when we rotate single loop of a conductor in a magnetic field.

During rotation, when one side of the loop comes in front of the magnetic north pole, the instantaneous motion of the conductor will be upward hence according to Fleming's Right Hand Rule the induced emf will have inward direction.

At the same time, another side of the loop comes in front of the magnetic south pole, the instantaneous motion of the conductor will be downward hence according to Fleming's Right Hand Rule the induced emf will have outward direction.

During rotation, each side of the loop comes under magnetic north pole and south pole alternately. Again in the pictures, when any of the coil sides (conductors) comes under north pole the motion of the conductor would be upward and when it comes under south pole the motion of the conductor would be downward. Hence, the emf induced in the loop alters its direction continuously. This is the most basic conceptual model of an electric generator. We also call it as single loop electric generator. We can collect the induced emf in the loop in two different ways

Let us connect slip ring with both ends of the loop. We can connect a load with the loop through the brushes rest on the slip rings as shown. In this case, the alternating electricity produced in the loop comes the load. This is an AC electric generator.

We can also collect the electricity produced in the rotating loop through commutator and brush arrangement as shown in the animated picture below. In this case, the electricity produced in the loop (here the rotating loop of the single loop generator can also be referred as the armature) gets rectified through the commutator and the load gets a DC power. This is the most basic conceptual model of a DC generator.

Construction of Alternator

Construction wise, an alternator consists of field poles placed on the rotating fixture of the machine i.e. rotor as shown in the figure above. The rotor rotates in the stator. The field poles get projected on the rotor body. The armature conductors are housed on the stator. An alternating three-phase voltage represented by aa’, bb’, cc’ is induced in the armature conductors thus resulting in the generation of three-phase electrical power. All modern electrical power generating stations use this technology for generation of three-phase power, and as a result, the alternator or synchronous generator has become a subject of great importance and interest for power engineers.

An alternator is basically a type of AC generator which also known as synchronous generator. The field poles are made to rotate at synchronous speed Ns = 120 f/P for effective power generation. Where, f signifies the alternating current frequency and the P represents the number of poles.alternator

In most practical construction of alternator, it is installed with a stationary armature winding and a rotating field unlike in the case of DC generator where the arrangement is exactly opposite. This modification is made to cope with the very high power of the order of few 100 Megawatts produced in an AC generator contrary to that of a DC generator. To accommodate such high power the conductor weighs and dimensions naturally have to be increased for optimum performance. For this reason is it beneficial to replace these high power armature windings by low power field windings, which is also consequently of much lighter weight, thus reducing the centrifugal force required to turn the rotor and permitting higher speed limits.

There are mainly two types of rotor used in construction of alternator,

1. Salient pole type.
2. Cylindrical rotor type.

Salient Pole Type

The term salient means protruding or projecting. The salient pole type of rotor is generally used for slow speed machines having large diameters and relatively small axial lengths. The poles, in this case, are made of thick laminated steel sections riveted together and attached to a rotor with the help of joint.

An alternator as mentioned earlier is mostly responsible for generation of very high electrical power. To enable that, the mechanical input given to the machine in terms of rotating torque must also be very high. This high torque value results in oscillation or hunting effect of the alternator or synchronous generator. To prevent these oscillations from going beyond bounds the damper winding is provided in the pole faces as shown in the figure. The damper windings are basically copper bars short-circuited at both ends are placed in the holes made in the pole axis. When the alternator is driven at a steady speed, the relative velocity of the damping winding with respect to the main field will be zero. But as soon as it departs from the synchronous speed there will be relative motion between the damper winding and the main field which is always rotating at synchronous speed. This relative difference will induce the current in them which will exert a torque on the field poles in such a way as to bring the alternator back to synchronous speed operation.

The salient feature of pole field structure has the following special feature-

1. They have a large horizontal diameter compared to a shorter axial length.
2. The pole shoes covers only about ²/₃rd of pole pitch.
3. Poles are laminated to reduce eddy current loss.
4. The salient pole type motor is generally used for low-speed operations of around 100 to 400 rpm, and they are used in power stations with hydraulic turbines or diesel engines.

Salient pole alternators driven by water turbines are called hydro-alternators or hydro generators.

Cylindrical Rotor Type

The cylindrical rotor is generally used for very high speed operation and employed in steam turbine driven alternators like turbogenerators. The machines are built in a number of ratings from 10 MVA to over 1500 MVA. The cylindrical rotor type machine has a uniform length in all directions, giving a cylindrical shape to the rotor thus providing uniform flux cutting in all directions. The rotor, in this case, consists of a smooth solid steel cylinder, having a number of slots along its outer periphery for hosting the field coils.

The cylindrical rotor alternators are generally designed for 2-pole type giving very high speed of

Or 4-pole type running at a speed of 

Where, f is the frequency of 50 Hz. The cylindrical rotor synchronous generator does not have any projections coming out from the surface of the rotor, rather central polar area is provided with slots for housing the field windings as we can see from the diagram above. The field coils are so arranged around these poles that flux density is maximum on the polar central line and gradually falls away as we move out towards the periphery. The cylindrical rotor type machine gives better balance and quieter-operation along with lesser windage losses.

Principle of DC Generator

There are two types of generators, one is ac generator and other is DC generator. Whatever may be the types of generators, it always converts mechanical power to electrical power. An AC generator produces alternating power. A DC generator produces direct power. Both of these generators produce electrical power, based on same fundamental principle of Faraday's law of electromagnetic induction. According to this law, when a conductor moves in a magnetic field it cuts magnetic lines of force, due to which an emf is induced in the conductor. The magnitude of this induced emf depends upon the rate of change of flux (magnetic line force) linkage with the conductor. This emf will cause a current to flow if the conductor circuit is closed.

Hence the most basic tow essential parts of a generator are

1.     a magnetic field
2.     conductors which move inside that magnetic field.

Now we will go through working principle of DC generator. As, the working principle of AC generator is not in scope of our discussion in this section.

Single Loop DC Generator

In the figure above, a single loop of conductor of rectangular shape is placed between two opposite poles of magnet.

Let's us consider, the rectangular loop of conductor is ABCD which rotates inside the magnetic field about its own axis ab. When the loop rotates from its vertical position to its horizontal position, it cuts the flux lines of the field. As during this movement two sides, i.e. AB and CD of the loop cut the flux lines there will be an emf induced in these both of the sides (AB and BC) of the loop.

As the loop is closed there will be a current circulating through the loop. The direction of the current can be determined by Flemming's right hand Rule. This rule says that if you stretch thumb, index finger and middle finger of your right hand perpendicular to each other, then thumbs indicates the direction of motion of the conductor, index finger indicates the direction of magnetic field i.e. N - pole to S - pole, and middle finger indicates the direction of flow of current through the conductor.

Now if we apply this right hand rule, we will see at this horizontal position of the loop, current will flow from point A to B and on the other side of the loop current will flow from point C to D.

Now if we allow the loop to move further, it will come again to its vertical position, but now upper side of the loop will be CD and lower side will be AB (just opposite of the previous vertical position). At this position the tangential motion of the sides of the loop is parallel to the flux lines of the field. Hence there will be no question of flux cutting and consequently there will be no current in the

loop. If the loop rotates further, it comes to again in horizontal position. But now, said AB side of the loop comes in front of N pole and CD comes in front of S pole, i.e. just opposite to the previous horizontal position as shown in the figure beside.

Here the tangential motion of the side of the loop is perpendicular to the flux lines, hence rate of flux cutting is maximum here and according to Flemming's right hand Rule, at this position current flows from B to A and on other side from D to C.

Now if the loop is continued to rotate about its axis, every time the side AB comes in front of S pole, the current flows from A to B and when it comes in front of N pole, the current flows from B to A. Similarly, every time the side CD comes in front of S pole the current flows from C to D and when it comes in front of N pole the current flows from D to C.

If we observe this phenomena in different way, it can be concluded, that each side of the loop comes in front of N pole, the current will flow through that side in same direction i.e. downward to the reference plane and similarly each side of the loop comes in front of S pole, current through it flows in same direction i.e. upwards from reference plane. From this, we will come to the topic of principle of DC generator.

Now the loop is opened and connected it with a split ring as shown in the figure below. Split ring are made out of a conducting cylinder which cuts into two halves or segments insulated from each other. The external load terminals are connected with two carbon brushes which are rest on these split slip ring segments.

Working Principle of DC Generator

It is seen that in the first half of the revolution current flows always along ABLMCD i.e. brush no 1 in contact with segment a. In the next half revolution, in the figure the direction of the induced current in the coil is reversed. But at the same time the position of the segments a and b are also reversed which results that brush no 1 comes in touch with the segment b. Hence, the current in the load resistance again flows from L to M. The wave from of the current through the load circuit is as shown in the figure. This current is unidirectional.

This is basic working principle of DC generator, explained by single loop generator model. The position of the brushes of DC generator is so arranged that the change over of the segments a and b from one brush to other takes place when the plane of rotating coil is at right angle to the plane of the lines of force. It is so become in that position, the induced emf in the coil is zero.

Electrical Engineer Needs to Know

This article aims to help beginner engineers ensure that they have the skills most often looked for and tested during the hiring process but can also serve as a starting point for experienced engineers looking to shore up weakness in these areas.

Between the availability of almost turnkey design platforms and rising interest in the Internet of Things, opportunities for electronic product development have never been greater. To be a successful designer able to tackle a wide range of challenges, though, a developer should have a number of skills to draw upon. Here are ten of the most common and, in our opinion, valuable skills that electronic product designers will want to have:

1. Performing circuit analysis

From designing simple resistor circuits to analyzing the frequency response of complex networks, designers will need to know how to write and solve the equations of node and loop analysis to figure out how component clusters are operating. Simulation programs can help with the heavy math when needed, but knowing how to set up the analysis will still be necessary.

2. Working with op-amps

The workhorse in nearly every application that requires signals beyond ones and zeroes, the operational amplifier is a versatile device. Used properly, it is an amplifier, integrator, signal conditioner, level shifter, and many more useful analog elements. The trick is in understanding the characteristics and limits of real devices rather than the idealized behavior described in textbooks.

3. Understanding analog filters

While the design of active analog filters may not be needed in all product development, understanding the effect that components have on analog signals is still an important skill to have. The capacitance, inductance, and impedance of both components and circuit traces can alter even digital signals in ways that, if not understood and compensated for, may cause systems to fail.

4. Designing digital filters

These days, most audio, video, and wireless signaling go digital at some point in their travels, with many kinds of signal manipulation carried out in the digital domain. Knowing how digital filters work to manipulate the analog signal that underlies the data stream will prove essential to avoiding surprises, even if a developer only invokes canned functions instead of designing the filter.

5. Designing feedback control

Robots, air conditioning, autonomous vehicles, and many other systems depend on feedback control loops for their proper operation. (And such loops include filters, so see above.) Designers should know how control loops function, how to determine their effectiveness, and how to ensure that they are stable in their behavior. No one wants a system that goes “oops.”

6. Managing hot components

The power dissipation of processors is rising, as is the density of components in small spaces, so component overheating is a common concern. Designers will need to know their options for keeping things cool as well as how to analyze thermal transfer to make sure they have provided enough relief.

7. Working with RF

Not all that long ago, design in the radio frequency (RF) spectrum was a specialty discipline that most developers never had to be concerned about. But with the IoT demanding wireless connectivity and rising clock speeds turning PCB circuit traces into RF waveguides, a basic understanding of how RF signals propagate and transfer energy is proving essential.

8. Appreciating firmware

Like it or not, more than half of the design effort in the electronics industry today involves software, and most electronic systems utilize a microprocessor or microcontroller to provide some or all of their functionality. However, hardware design decisions can have a substantial impact on the ease and effectiveness of code development. So even if not directly involved in the programming effort, a developer should have some understanding of what firmware is, how it’s created, and its role in making things work.

9. Using statistics for manufacturability

Getting a prototype to work in the lab is only the first step in creating a product for market. The design must be robust enough to accommodate all of the variations in component value that will occur during mass production and the wide range of operating environments that the product will face. Statistical analysis is the tool that developers will need to ensure that their design will work in the face of this uncertainty.

10. Managing the career

Along with all their technical knowledge, developers should have some basic business and career management skills. Landing and keeping a job, growing their access to opportunities and compensation, rising in the hierarchy or launching an entrepreneurial endeavor, and maintaining long-term satisfaction in the work effort all require conscious effort as well as interpersonal and team interactions. Working toward a destination, even one that changes from time to time, provides far more reward than simply reacting to whatever comes up.

What do electrical engineers do?

Electrical engineering provides you with endless opportunities

An electrical engineer is someone who designs and develops new electrical systems, solves problems and tests equipment. They study and apply the physics and mathematics of electricity, electromagnetism and electronics to both large and small scale systems to process information and transmit energy. They work with all kinds of electronic devices, from the smallest pocket devices to large supercomputers.

Industries electrical engineers work in

Electrical engineers are usually concerned with large-scale electrical systems such as motor control and power transmission, as well as utilizing electricity to transmit energy. Electrical engineers may work on a diverse range of technologies, from the design of household appliances, lighting and wiring of buildings, telecommunication systems, electrical power stations and satellite communications. Another emerging field for electrical engineers is microelectronics - the design and development of electrical systems and circuits in computers and mobile devices.

Electrical engineering design

A few examples of the applications and reach of electrical engineering are:

• The computer, tablet or smartphone you purchased recently is a masterpiece of electrical engineering design.
• Robots are comprised of sensors, actuators, microprocessors and sophisticated feedback control systems, designed by electrical engineers!
• Space projects - deep space communications, robust control systems, extra terrestrial GPS for navigation and positioning, power generation and storage networks, imaging systems - made possible by electrical engineers.
• Sophisticated medical technology that you encounter in a modern hospital including CT, MRI and PET imaging machines, ECG and blood pressure monitors, all based off electrical engineering principles.

Electrical engineering and electronics - Germany Overview

The electrical engineering and electronics industry is multi-faceted. It produces not only electrical appliances, consumer electronics and lighting technology, but is also home to cutting-edge technology industries such as nano technology and chip production. The electrical engineering industry mostly consists of small and medium-sized companies. The industry’s product portfolio is both very broad and extremely dynamic, generating a third of its revenues with new products and innovations. More than 180.000 engineers work for the German electrical industry.

Export as a growth driver

In terms of employment, the electrical engineering industry is Germany’s second largest industrial branch, generating revenues of €178 billion in 2015. The production in 2015 increased by 1.4 percent compared to the previous year. In this context, foreign trade is extremely important. In 2015, export volumes accounted for €174 billion, of which two thirds were shipped to industrial nations. However, newly industrialised countries have also discovered the value of German electrical products, and the share of export to these countries has experienced considerable growth in the last few years, most recently increasing by 6 percent compared to the year before.

Research: looking towards the future

Particular in the emerging markets of Asia and South America, energy efficiency is an important aspect of technology which is relevant for both business and environmental reasons. German companies have considerable research competence in this area. Every year, the German electrical industry invests a total of €15 billion in research and development and offers employment for 846,000 experts in this field. Furthermore, the innovation spirit of the sector shows in the high number of patent applications, which add up to some 13,000 each year.

Electrical Projects

Major Projects

1.     Induction Motor Speed & Direction Controller
2.     Hybrid Inverter With Solar Battery Charging
3.     Digitally Controlled Home Automation Project
4.     3 Phase Induction Motor With Soft Start
5.     Wireless Mobile Charging Project
6.     Solar UPS Project
7.     Power Supply With Auto Switching
8.     Flexible AC Transmission Using TSC
9.     Switching Load By Touch
10.     Emergency Auto Led Light
11.     3 Way Failure Analyzer Reset On Temporary Fault else Permanent trip
12.     Over Voltage Under Voltage Load Protection
13.     Protecting Induction Motor From Phase & Temperature
14.     Generating DC High Voltage Using Marx Generator
15.     Advanced Wireless Power Transfer System
16.     Mini Windmill Power Generation Project
17.     Dual Power Generation Solar Plus Windmill Generator
18.     Single Phase Induction Motor With Smooth Start
19.     Checking Phase Sequence of 3 Phase Supply
20.     6 Volt DC to 10 Volt DC Converter
21.     Ac to High Voltage DC Using Voltage Multiplier Circuit
22.     Microcontroller less Four Quadrant DC Motor Control
23.     Smart Wireless Battery Charging With Charge Monitor Project
24.     Accurate Room Temperature Controller Project
25.     Industry Process Automation Using Programmable Switching
26.     Testing Life Cycle Of Electrical Loads Using Down Counter
27.     AC Power Strength Controller System
28.     System To Measure Solar Power
29.     Controlling Solar Energy Charge
30.     Single Phase Induction Motor With Smooth Start
31.     Configurable Password Security System
32.     Supervisory Controlling Plus Data Acquisition For Remote Industry
33.     Load Control System Using DTMF
34.     RPM Display For BLDC Motor With Speed Controller
35.     Multi-Power Supply Using 4 Different Sources For No Break Power Supply
36.     Cycle Switching Without Harmonics For Industrial Power Control
37.     AC Power Controller With Programmable Interface
38.     Load Shedding Time Management With Programmable Interface
39.     Lamp Illumination Control With Precision
40.     Flexible Ac Transmitter System Using TSR
41.     Device Load Monitor With Programmable Meter For Energy Audit
42.     Power Meter billing Plus Load Control Using GSM
43.     Monthly Electricity Billing Display With Bill SMS Feature
44.     Industry Power Consumption Penalty Minimization Using AFPC Unit Project
45.     Commercial Power Saver Project

Mini Projects

1.     Solar Powered Battery Charging With Reverse Current Protection
2.     Automated Night Lighting System
3.     Clap Based Fan Switching System
4.     Wireless Doorbell Calling System
5.     Synchronously Blinking Emergency Light
6.     Sound Operated Timer Project
7.     Smart Burglar Alarm
8.     Plant Moisture Monitoring System
9.     Wireless Cell Phone Detection System
10.     Wireless FM Transmitter Mic
11.     Electronic Watch Dog Project
12.     Mini FM Transmission System
13.     Auto Electronic School Bell
14.     Advanced Wireless Power Transfer System
15.     Overvoltage And Undervoltage Protection System
16.     Fast Voting Game Project
17.     Electronic Water Level Controller Device
18.     E Bicycle Locking System
19.     Automatic Smoke Detector Alarm
20.     Synchronously Blinking Emergency Light
21.     Sound Operated Timer Project
22.     Smart Burglar Alarm
23.     Plant Moisture Monitoring System