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Induction motors use an iron core and require flux in the iron to
operate. In order to achieve the commercial goals of smallest size and
lowest price at best efficiency, induction motors are designed to
operate at a high level of flux in the iron. The flux is determined by
the turns, voltage and frequency. In a modern motor, if the flux is
increased by a small amount, the iron losses increase and the iron
tends towards saturation. At saturation, the inductance begins to fall
and the current increases further. To reduce the flux at a given
voltage and frequency, the turns on the stator are increased. This
reduces the Iron loss, but a longer length of thinner wire is used and
the copper loss increases. Design becomes a balancing act between
copper loss and iron loss and so the design is optimised for a given
voltage and frequency.

If the voltage applied to the motor is held constant
and the frequency is increased, the inductive reactance increases and
so the flux reduces. This effectively reduces the maximum torque
capacity of the motor and so the motor power rating at the higher
frequency remains the same.

If the voltage
applied to the motor is held constant and the frequency is reduced, the
current will increase and in theory, the torque will also increase. The
motor should be able to deliver the same power also, BUT the flux in
the iron is now too high resulting in excessive iron loss, and the
motor will fail prematurely. Above a very low frequency, (5 – 10Hz) the
impedance of the magentising circuit of the motor is primarily
inductive and so in order to keep the flux within limits, it is
important to keep a linear V/F ratio (Voltage to Frequency ratio). If
the frequency is reduced by 10%, the voltage must also be reduced by
10%. Because the flux in the iron remains the same, the torque capacity
remains the same and so the power rating of the motor also drops by 10%.

60Hz rated motor on 50Hz

Provided the voltage is dropped by the same proportion as the frequency, it is OK to run a 60Hz motor on 50Hz. The speed will be reduced by the reduction in frequency and the power capacity will also reduce by the ratio of the reduction in frequency.

60 Hz 50 Hz
Line Voltage Line Voltage
480 400
460 383
440 367
230 191

 

50Hz rated motor on 60Hz

Provided the voltage is increased by the same proportion as the frequency, it is OK to run a 50Hz motor on 60Hz. The speed will be increased by the increase in frequency and the power capacity will also increase by the ratio of the increase in frequency.

50 Hz 60 Hz
Line Voltage Line Voltage
415 498
400 480
380 456
230

276

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Calculation of short-circuit currents

Summary

In view of sizing an electrical installation and the required equipment, as well as determining the means required for the protection of life and property, short-circuit currents must be calculated for every point in the network.
This “Cahier Technique” reviews the calculation methods for short-circuit currents as laid down by standards such as IEC 60909. It is intended for radial and meshed low-voltage (LV) and high-voltage (HV) circuits.
The aim is to provide a further understanding of the calculation methods, essential when determining short-circuit currents, even when computerised methods are employed.

Reference

  • – Author :B. de Metz-Noblat, F. Dumas, C. Poulain
  • – Publication date:01/09/2005
  • – Page number:32
  • – ECT no:158

Power Quality

Summary

One of the properties of electricity is that some of its characteristics depend not only on the electricity producer/distributor but also on the equipment manufacturers and the customer. The large number of players combined with the use of terminology and definitions which may sometimes be
imprecise partly explain why this subject area is so complex.
This “Cahier Technique” aims to facilitate exchanges on this topic between specialists and non-specialists, as well as customers, manufacturers, installers, designers and distributors. The clear terminology used should help avoid confusion. It describes the main phenomena causing degradation in Power Quality (PQ), their origins, the consequences for equipment and the main solutions. It offers a methodology for measuring the PQ in accordance with differing aims. Illustrated with practical examples for the implementation of solutions, it shows that only by observing best practice and by applying strict methodology (diagnostics, research,solutions,implementation and preventive maintenance) can users obtain the right quality of power supply for their requirements.

Reference

  • – Author :Philippe FERRACCI
  • – Publication date:01/10/2001
  • – Page number:36
  • – ECT no:199

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John G. Webster, “The Measurement, Instrumentation and Sensors Handbook (Electrical Engineering Handbook) ”
Springer | 1999 | ISBN: 3540648305 | 1500 pages | PDF | 27,8 MB

The Measurement Instrumentation and Sensors Handbook describes the use of instruments and techniques for practical measurements required in engineering, physics, chemistry, and the life sciences. The book examines: Sensors, Hardware, Software, Techniques, Information processing systems, Automatic data acquisition. Reduction and analysis as well as their incorporation for control purposes. Organized according to the measurement problem, each section addresses the different ways of making a measurement for a given variable. Chapters present three levels: Basic information without equations and a description of the subject that can be understood by the newcomer. Detailed text and mathematical treatment essential for discovering applications and solving problems outside ones field of specialty Advanced applications of the subject, evaluative opinions, and areas for future study.

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Practical Electronics Handbook

Ian Sinclair, “Practical Electronics Handbook”
Newnes; 5 ed | 2000 | ISBN: 0750645857 | 576 pages | PDF | 3,8 MB

Review
‘This must be one of the best, if not the best, value-for-money handbooks that you can buy. It has been designed to include within a reasonable space most of the information that is useful in day-to-day electronics… A practical and comprehensive collection of circuits, rules of thumb and design for professional engineers, students and enthusiasts, and enough background to allow the understanding and development of a range of basic circuits.’ Elektor Electronics.

‘The handbook provides a clear, cohesive approach to complement and clarify the mass of information often provided in databooks.’ New Electronics.

‘An excellent handbook for the constructor ranging from resistor colour codes to simple transistor building blocks. An invaluable reference book for everyone from beginners to professional engineers. Covers passive and active discrete components circuits, linear and digital ICs and TTL and CMOS pinouts.’ Electronics and Beyond.

http://www.megaupload.com/?d=BODDVLQ4
or
http://rapidshare.com/files/215113037/PraElecHb.rar

———

J & P Transformer Book, Thirteenth Edition

J & P Transformer Book, Thirteenth Edition
Publisher: Newnes | Pages: 992 | 2007-10-22 | ISBN 0750681640 | PDF | 23 MB

The J&P Transformer Book has been in print for 80 years, and is renowned internationally as the definitive reference work covering the design, construction, installation, monitoring and maintenance of power transformers in electricity generation and distribution, electricity substations, and industrial applications. The broad scope of the Transformer Book and its practical focus makes it ideal reading for graduate engineers embarking on a design career, students of electrical engineering, and a broader audience in the power engineering and transformer manufacturing sectors. However, it is not a text to read once and consign to the shelf, but rather a hard-working working reference for the seasoned professional as well as the novice.

The thirteenth edition includes new sections and updates throughout, referencing the latest International (IEC) and European standards. New material includes coverage of recent developments in amorphous steels, and expanded coverage of the competitive area of small distribution transformers.

Thanks to original uploader

http://rapidshare.com/files/215205936/0750681640.zip
or
http://www.easy-share.com/1904257340/0750681640.zip

———–

Process/Industrial Instruments and Controls Handbook

Gregory McMillan, Douglas Considine, “Process/Industrial Instruments and Controls Handbook”
McGraw-Hill Professional; 5 ed | 1999 | ISBN: 0070125821 | 1200 pages | PDF | 16,1 MB

Award-winning editor Greg McMillan has loaded Process/Industrial Instruments and Controls Handbook, Fifth Edition, with advice from top technical experts to help you tackle process instrument and control assignments confidently and solve problems efficiently. This major revision of the bestselling on-the-job toolkit includes time-saving tables,selection ratings, key points, rules of thumb and hundreds of topic-defining illustrations. Updated to mirror the most common industry practices, it brings you up to speed on smart instrumentation and the latest advances sparked by increased power and miniaturization of the microprocessor. Thorough coverage of the Windows NT platform and Fieldbus… distributed control systems and field-based systems…knowledge-based operator training…instrument maintenance cost reduction and an overview of the ISA/IEC Fieldbus Standard help you get the most out of these major shifts in technology.

Mirror:
http://rapidshare.com/files/215176802/ProIndInstCon.rar

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The Electric Power Engineering Handbook, by Leonard L. Grigsby
CRC; 2 edition | English | May 30, 2007 | ISBN: 0849392934 | 950 Pages, Illustrated | PDF | 25,4 Mb
Description : A reference at once so elemental and so comprehensive, The Electric Power Engineering Handbook not only describes the field’s body of knowledge, but defines it. Written by expert contributors under the leadership of one of the world’s most respected and accomplished authorities in power engineering, the second edition remains the undisputed guide to power generation, transmission, and distribution, as well as for modeling, analyzing, planning, designing, monitoring, and controlling power systems. This fully updated edition is now available as a set of five books, each focused on a particular area of expertise. The handbook’s first edition spawned two bestselling specialist works, Electric Power Transformer Engineering and Electric Power Substations Engineering, each of which included new material not found in the handbook. For this edition, these highly popular progeny rejoin the handbook, supplying ten additional chapters. Along with updates to nearly every chapter, several rewritten articles, and new material added to existing sections, this edition features nine entirely new chapters on such areas as environmental effects of transmission systems, substation asset management, substation commissioning, distribution system characteristics and protection, real-time control of distributed generation, and flexible AC transmission system (FACTS) controllers. Retaining its unique tutorial style, The Electric Power Engineering Handbook, Second Edition prevails as a monument to the decades of ingenuity and tireless efforts of power engineers around the world.
Download links :

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Basic Electrical Technology
EE IIT, Kharagpur, India | 2008 | ISBN: N/A | 750 pages | PDF | 13,5 MB

Contents
Module 1 Introduction
Lesson 1 – Introducing the Course on Basic Electrical
Lesson 2 – Generation, Transmission and Distributio of Electic Power an Overwiew
Module 2 DC Circuit
Lesson 3 Introducing of Electric Circuit
Lesson 4 Loop Analysis of resistive circuit in the context of dc voltages and currents
Lesson 5 Node-voltage analysis of resistive Circuit in the context of dc voltages and currents
Lesson 6 Wye – Delta or Deta – Wye Transformations
Lesson 7 Superposition Theorem in the context of dc voltages and current sources acting in a resistive network
Lesson 8 Thevenin’s and Norton’ theorems in the context of dc voltage and current sources in acting in a resistive network
Lesson 9 Analysis of dc resistive network in presence of one non-linear element
Module 3 R-L & R-C Transients
Lesson 10 Study of DC transients in R-L and R-C circuits
Lesson 11 Study of DC transients in R-L-C Circuits
Module 4 Single-phase AC Circuits
Lesson 12 Generation of Sinusoidal Voltage Waveform (AC) and some fundamental Concepts
Lesson 13 Representation of Sinusoidal Signal by a Phasor and Solution of Current in R-L-C Series Circuits
Lesson 14 Solution of Current in R-L-C Series Circuits
Lesson 15 Solution of Current in AC Series and Parallel Circuits
Lesson 16 Solution of Current AC Parallael and Series-parallel Circuits
Lesson 17 Resonance in Series and Parallel Circuits
Lesson 18 Three-phase Balanced Supply
Module 5 Three-phase AC Circuits
Lesson 19 Three-phase Delta-Connected Balanced Load
Lesson 20 Measurement of Power in a Three-phase Circuit
Module 6 Magnetic Circuits and Core Losses
Lesson 21 Magnetic Circuits
Lesson 22 Eddy Current & Hysteresis Loss
Module 7 Transformer
Lesson 23 Ideal Transformer
Lesson 24 Practical Transformer
Lesson 25 Testing, Efficiency & Regulation
Lesson 26 Three Phase Transformer
Lesson 27 Autotransformer
Lesson 28 Problem solving on Transformers
Module 8 Three-phase Induction Motor
Lesson 29 Rotating Magnetic Field in three-phase Induction Motor
Lesson 30 Construction and Principle of Operation of IM
Lesson 31 Equivalent Circuit and Power Flow Diagram of IM
Lesson 32 Torque Slip (speed) Characteristics of Induction Motor (IM)
Lesson 33 Different Types of Startes for Induction Motor (IM)
Module 9 DC Machines
Lesson 35 Constructional Features of D.C Machines
Lesson 36 Principles of Operation of D.C Machines
Lesson 37 AMF & Torque Equation
Lesson 38 D.C Generators
Lesson 39 D.C Motors
Lesson 40 Losses, Efficiency and Testing of D.C Machines
Lesson 41 Problem Solving on D.C Machines
Module 10 Measuring Instruments
Lesson 42 Study of DC-AC Measuring Instruments
Lesson 43 Study of Electro-Dynamic Type Instruments
Lesson 44 Study of Single Phase Induction Type Energy Meter or Watt-hour Meter

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Lighting Engineering: Applied Calculations
Publisher: Architectural Press | Pages: 518 2000-12-18 ISBN 0750650516 | PDF | 17 MB

Lighting Engineering: Applied Calculations’ describes the mathematical background to the calculation techniques used in lighting engineering and links them to the applications with which they are used. The fundamentals of flux and illuminance, colour, measurement and optical design are covered in detail. There are detailed discussions of specific applications, including interior lighting, road lighting, tunnel lighting, floodlighting and emergency lighting. The authors have used their years of experience to provide guidance for common mistakes and useful techniques including worked examples and case studies.

The last decade has seen the universal application of personal computers to lighting engineering on a day-to-day basis. Many calculations that were previously impracticable are therefore now easily accessible to any engineer or designer who has access to an appropriate computer program. However, a grasp of the underlying calculation principles is still necessary in order to utilise these technologies to the full.

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