braunovic - electrical contacts - fundamentals, applications and technology

q 2006 by Taylor & Francis Group, LLC q 2006 by Taylor & Francis Group, LLC Preface The multidisciplinary study of the electrical contact in modern engineering is significant, but often neglected. The scientist and engineers who have spent their professional lives studying and applying electrical contacts know that these components are critical to the successful operation of all products that use electricity. In our civilization, all electricity transmission and distribution, most control, and most information exchange depends upon the passage of electricity through an electrical contact at least once. The failure of an electrical contact has resulted in severe consequences, e.g., an energy collapse of a megapolis, a failure of the telephone system, and even the crash of an airplane. Ragnar Holm, the prominent researcher, renowned engineer, and inventor, developed the validity of “electrical contacts” as its own technical discipline with his book Electric Contacts (1958). The 50 years following its publication have given a firm confirmation of the accuracy of his predictions and conclusions. Since that time, however, there has been a huge increase in the application of electrical contacts. For example, the era of the information highway and the development of the integrated circuit have created new challenges in the use of electrical contacts. The use of electrical contacts on the microscopic scale presents numerous problems never considered by previous generations of researchers and engineers. The future MEMS/NEMS technology is another area where the theory and practice of the electrical contact is of critical importance. The purpose of the authors has been to combine the progress in research and development in the areas of mechanical engineering and tribology, which Holm postulated to be key segments in electrical contacts, with the new data on electrical current transfer, especially at the micro/nanoscale. This book complements the recent volume Electrical Contacts: Principles and Applications (published by Marcel Dekker, 1999). It takes a practical applications approach to the subject and presents valuable design information for practicing mechanical and electrical engineers. In fact, the information contained here will serve as an excellent source of information not only for anyone developing equipment that uses electricity, but for postgraduate students who are concerned about the passage of current from one conductor to another. The authors of this book have many years of research and practical experience. One unusual and interesting aspect of the book’s development is that it comes through the cooperation of the different approaches to the subject from the West and the East. They have succeeded in making the bulk of research and engineering data equally clear for all the segments of the international audience. Paul G. Slade Ithaca, New York q 2006 by Taylor & Francis Group, LLC The Authors Dr. Milenko Braunovic ´ received his Dipl. Ing degree in technical physics from the University of Belgrade, Yugoslavia, in 1962 and the M.Met. and Ph.D. degrees in physical metallurgy from the University of Sheffield, England in 1967 and 1969, respectively. From 1971 until 1997, he was working at Hydro-Que ´ bec Research Institute (IREQ) as a senior member of the scientific staff. He retired from IREQ in 1997 and established his own scientific consulting company, MB Interface. From 1997 until 2000 he was consulting for the Canadian Electricity Association as a technology advisor. He is presently R&D manager with A.G.S. Taron Technologies in Boucherville, QC, Canada. During the last 30 years, Dr. Braunovic ´ has been responsible for the development and management of a broad range of research projects for Hydro-Que ´ bec and the Canadian Electrical Association in the areas of electrical power contacts, connector design and evaluation, accelerated test methodologies, and tribology of power connections. He has also initiated and supervised the R&D activities in the field of shape-memory alloy applications in power systems. Dr. Braunovic ´ is the author of more than 100 papers and technical reports, including contributions to encyclopaedias and books, in his particular areas of scientific interests. In addition, he frequently lectures at seminars world wide and has presented a large number of papers at various international conferences. For his contributions to the science and practice of electrical contacts, Dr. Braunovic ´ received the Ragnar Holm Scientific Achievement Award in 1994, and for his long-term leadership and service to the Holm Conference on Electrical Contacts he received, in 1999, the Ralph Armington Recognition Award. He is also a recipient of the 1994 IEEE CPMT Best Paper Award. He successfully chaired the Fifteenth International Conference on Electrical Contacts held in Montreal in 1990, and was a technical program chairman of the Eighteenth International Conference on Electrical Contacts held in Chicago in 1996. He is a senior member of the Institute of Electronics and Electrical Engineers (IEEE), the American Society for Metals (ASM), the Materials Research Society (MRS), the Planetary Society, the American Society for Testing of Materials (ASTM), and The Minerals, Metals & Materials Society (TMS). Dr. Valery Konchits was born on January 3, 1949 in the city of Gomel, Belarus. He graduated from Gomel State University in 1972. He received his Ph.D. degree in tribology from the Kalinin Polytechnic Institute, Russia in 1981. In 1972, he joined the Metal-Polymer Research Institute of the National Academy of Sciences of Belarus in Gomel. In 1993, he became the head of the laboratory in the Tribology Department. Since 2001, Dr. Konchits has been Deputy Director of the Metal-Polymer Research Institute. The scientific interests of Dr. Konchits lie mainly in electrical contacts’ friction and wear, contact phenomena at their interfaces, and electrophysical diagnostic methods of friction. He is the author of more than 80 papers and holds 10 patents. He is also the co-author of a monograph in Russian, “Tribology of electrical contacts” (authors: Konchits V.V., Meshkov V.V., Myshkin N.K., 1986, Minsk). q 2006 by Taylor & Francis Group, LLC Prof. Nikolai Myshkin was born on May 12, 1948 in the city of Ivanovo, Russia. He graduated from the Power Engineering Institute in 1971 with a degree in electromechanics. Has received his Ph.D. from the Institute for Problems in Mechanics of the Russian Academy of Sciences in 1977. The same year, he joined the Metal-Polymer Research Institute in Gomel where since 1990 he has been Head of the Tribology Department. He has also been the director of MPRI since 2002. He earned his Dr.Sc. degree in tribology in 1985 and became a full professor of materials science in 1991. He was elected as a correspondent member of the Belarus National Academy of Sciences in 2004. He received the USSR National Award for Young Scientists in 1983, the Award for Best Research given by the Belarus National Academy of Sciences in 1993, and the Award of the Russian Government in Science and Technology in 2004. The scientific interests of Prof. Myshkin lie mainly in the characterization at micro and nanoscale surfaces, the contact mechanics of solids, wear monitoring, electric phenomena in friction, tribotesting equipment, and aerospace engineering. He has authored or co-authored more than 180 papers and 60 patents. He is a co-author of the Tribology Handbook (Russian edition 1979, English translation 1982), monographs Physics, Chemistry and Mechanics of Boundary Lubrication (1979), Tribology of Electric Contacts (1986), Acoustic and Electric Methods in Tribology (Russian edition 1987, English translation 1990), Structure and Wear Resistance of Surface Layers (1991), Textbook in Materials Science (1989), Magnetic Fluids in Machinery (1993), the English textbook Introduction to Tribology (1997), and Tribology: Principles and Applications (2002). Prof. Myshkin is chairman of the Belarus Tribology Society and vice-president of the International Tribology Council. He is also assistant editor-in-chief of the Journal of Friction and Wear, and a member of editorial boards of Tribology International, Tribology Letters, Industrial Lubrication and Tribology, and the International Journal of Applied Mechanics and Engineering. q 2006 by Taylor & Francis Group, LLC Acknowledgments In the preparation of the book, the authors have used a large number of published materials, either in the form of papers in referenced journals, or from the websites of different companies and organizations. In both cases, proper permissions for using these materials have been obtained. In many instances, the authors obtained the required information directly from the authors of the papers or from the company authorities. The authors are indebted to Dr. Paul Slade for writing the preface of the book. Special thanks go to Dr. Daniel Gagnon of Hydro-Que ´ bec Research Institute (IREQ) in Varennes, QC, Canada for providing essential reference material and fruitful discussions concerning certain topics of power connections. The authors are grateful to Dr. Mark. I. Petrokovets for fruitful discussion and his help in preparation of Chapters 2, 3 and 5. We also thank Dr. Denis Tkachuk for his valuable assistance in preparation of the manuscript. Acknowledgement is made to the many individuals and company authorities for permission to use the original material and, in particular, to modify the original figures to maintain the uniformity of graphic presentation throughout the book. The following is a list of these individuals and company authorities. Prof. George M. Pharr, Department of Materials Science and Engineering, University of Tennessee, Knoxville, USA for providing the papers on nanoindenation testing methods and instrumentation and allowing modification of some of the figures appearing in these papers. Prof. Doris Kuhlmann-Wilsdorf, Department of Materials Science and Engineering, University of Virginia, Charlottesville, USA for permission to use the information on fiber-brushes and dislocation nature of the processes occurring during friction. Dr. Roland Timsit of Timron Scientific Consulting, Inc., Toronto, Canada for permission to use the relevant material from his papers and publications. Dr. Robert Malucci of Molex, Inc., Lisle, IL, USA, for permission to use the relevant material from his papers and publications and modify some of the figures from his original publications cited in this book. Dr. Bill Abbott of Batelle, USA for helpful suggestions and discussions regarding the problems of corrosion in electrical and electronic connections. Dr. Sophie Noel, Laboratoire de Ge ´ nie Electrique, Supe ´ lec, Gif sur Yvette, France for helpful discussions concerning the lubrication of electrical contacts and permission to use some of data from the publications cited in this book Dr. Magne Runde of the Norwegian University of Science and Technology, Norway, for helpful discussions concerning the problem of electromigration in electrical contacts. Prof. Zoran Djuric and Milos Frantlovic of the Center for Microelectronics Technologies and Single Crystals, MTM, University of Belgrade, Serbia and Montenegro for providing the information on the wireless temperature monitoring system. Dr. Bella Chudnovsky of Square D, USA, for helpful discussions concerning the whisker formation in electrical contacts and for permission to use the information on the On-Line Wireless Temperature Monitoring System for LV, MV electrical equipment fond on the company web site (http://www.squared.com). Prof. L.K.J. Vandamme of the Department of Electrical Engineering, Eindhoven University of Technology, The Netherlands for providing and allowing the use of reference materials concerning the noise in electrical connections. Mr. Larry Smith of USi, Armonk, NY, USA, for permitting the use of the images and descriptions of the Power-donut unit found on the company web site (http://www.usi-power.com). q 2006 by Taylor & Francis Group, LLC Dr. Young-kook (Ryan) Yoo, Director of Global Sales and Marketing of PSIA Corp. Sungnam 462-120, Korea, for permission to use descriptions of different surface analytical equipment as posted on the company web site (http://www.psiainc.com.). Dr. G. Palumbo of Integran Technologies, Inc., Toronto, Canada for providing the information on the grain size effects in nanocrystalline materials (http://www.integran.com). Mr. J. Renowden of Transpower New Zealand, for providing the information concerning the field applications of the microohmeter Ohmstik on power lines (http://www.transpower.co.nz). Mr. J. Lebold of Boldstarinfrared, Canada for permission to use the infrared images from the company web site (http://www.boldstarinfrared.com). R.N. Wurzbach of Maintenance Reliability Group (MRG), York, PA, USA for permission to use description of the web-based cost benefit analysis method for predictive maintenance (http://www.mrgcorp.com). ndb Technologie, Inc., Que ´ bec, Canada for permission to use the information about the microohmeters found on their web site (http://www.ndb.qc.ca). In addition, the authors would like to acknowledge the courtesy of the following companies for allowing the use of the information found on their respective websites: Omega Madge Tech., Inc., (http://www.omega.com), FLIR Systems (http://www.flirthermography.com), Mikron Infrared, Inc. (http://www.irimaging.com), Electrophysics Corp. (http://www.electrophysics.com), Infrared Solution, Inc. (http://www.infraredsolutions.com), Elwood Corp. (http://www.elwoodcorp.com), Sensolink Corp., (http://www.sensorlink.com). Lastly, it is a pleasure to acknowledge and express our gratitude to Mrs. K. Braunovic ´ for her generous hospitality shown to the authors during the preparation of the book manuscript. q 2006 by Taylor & Francis Group, LLC Introduction This book provides detailed analytical models, state-of-the-art techniques, methodologies and tools used to assess and maintain the reliability of a broad class of moving and permanent electrical contacts in many technological devices, such as automotive and aerospace components, high- and low-power contact joints, sliding and breaking contacts, electronic and control apparatus, and electromechanical systems. It provides a comprehensive outline of the tribological behavior of electrical contacts that is rarely discussed in the existing literature; these are problems of considerable interest for researchers and engineers. Focusing on the main mechanical and electrical problems in connections with the field applications and the relationship between structure and properties, this volume provides a well- balanced treatment of the mechanics and the materials science of electrical contacts, while not neglecting the importance of their design, development, and manufacturing. The book provides a complete introduction to electric conduction across a contacting interface as a function of surface topography, load, and physical-mechanical properties of materials, and the interrelation of electrical performance with friction and wear; it takes into account material properties and lubricant effects. Consideration is given to the deleterious effects of different degradation mechanisms, such as stress relaxation/creep, fretting, differential thermal expansion, and the formation of intermetallics, as well as their impacts on operating costs, safety, network reliability, power quality. Various palliative measures to improve the reliability and serviceability of electrical contact at macro-, micro-, and nano-levels are also discussed. This book diminishes a large gap between engineering practice widely utilizing empirically found methods for designing and optimizing the contact characteristics and theory relating to tribological and electromechanical characteristics of the contacts. The main trends in the practical solutions of the tribological problems in electrical contacts are discussed in terms of contact design, research and development of contact materials, coatings and lubricants and the examples of practical applications in various fields are given throughout the book. Covering a wide range of references, tables of contact materials, coatings and lubrication properties, as well as various testing procedures used to evaluate these properties, the book will be an indispensable practical tool for professional, research, design and development engineers. The book (or parts of it) can be used not only as a reference, but also as a textbook for advanced graduate students and undergraduates, as it develops the subject from its foundations and contains problems and solutions for each chapter. q 2006 by Taylor & Francis Group, LLC [...]... 4.1.1.9 Nickel 80 4.1.2 Metals and Alloys for Heavy- and Medium-Duty Contacts 80 4.1.3 Metals and Alloys for Light-Duty Contacts 83 4.1.4 Materials for Liquid-Metal Contacts 85 4.1.5 Spring Contact Materials 87 4.1.6 Shape-Memory Alloys and Their Applications in Electrical Contacts 88 4.2 Coatings for Electrical Contacts 89 4.2.1 Basic Requirements... include contacts of electrical machines, current pick-offs of transport and lifting machines, and of radio-electronic devices, and control and automatic systems As a rule, sliding contacts for electrical and transportation machines are intended to commutate currents of a moderate and high intensity while those for radio-electronic devices and control and automatic systems are usually low-current level contacts. .. periodical closing and opening of an electrical circuit, such as in different switches, contactors, relays, and similar devices Because of differences in breaking power, current, and voltage, there is a great variety of breaking contacts The breaking contacts can be classified as light-, medium- and heavy-duty: † Light-duty contacts carry very low currents, operate at voltages up to 250 V, and display no... Area (Ar/Aa) (%) a Alloy /Applied Load 10 N 100 N 1000 N Al (H-19) Al (H-0) AlC0.75% MgC0.15% Fe (H-19) AlC0.75% MgC0.15% Fe (H-0) Cu (H-0) 0.01 0.05 0.01 0.02 0.008 0.1 0.5 0.1 0.2 0.08 1.0 5.0 1.0 2.0 0.8 a (H-0), fully annealed; (H-19), fully hardened q 2006 by Taylor & Francis Group, LLC 8 Electrical Contacts: Fundamentals, Applications and Technology of the film (Rf) R c Z Rs C R f Rf Z s=pa2 ; (1.5)... transfer, and erosion (pitting) Applications of medium-duty contacts are control devices for industrial, domestic, and distribution network applications q 2006 by Taylor & Francis Group, LLC Introduction to Electrical Contacts 5 † Heavy-duty contacts carry very high currents (tens of kA) and operate at very high voltages (hundreds of kV) The most common types of these connectors are contactors, starters, and. .. spacing and height; S, Rmax, roughness spacing and height q 2006 by Taylor & Francis Group, LLC 12 Electrical Contacts: Fundamentals, Applications and Technology (bigger parts may have a larger upper limit, up to 200–300 mm); the height is 0.01–500 mm Some countries (Germany, Switzerland, and the United States, for example) have standards for waviness There is no strict distinction between waviness and. .. Fragment of sketch by (a) Coulomb and (b) Johnson q 2006 by Taylor & Francis Group, LLC (2.2) 14 Electrical Contacts: Fundamentals, Applications and Technology Usually, Ra is averaged over several consecutive sampling lengths from 2 to 20 in accordance with the national standard The parameter is identical to arithmetic average (AA) and center-line average (CLA) The root-mean-square (RMS) roughness, Rq,... Electromechanical Electrical Thermal Electroplastic effect Sparking and arcing Softening/melting of surface layers Electrodynamic repulsion Fritting Electrotransport Effect of electrical field on oxidation FIGURE 1.2 Possible effects on the passage of electrical current through the interface q 2006 by Taylor & Francis Group, LLC 6 Electrical Contacts: Fundamentals, Applications and Technology For electrical. .. Francis Group, LLC 4 Electrical Contacts: Fundamentals, Applications and Technology Electric contacts Stationary Moving Sliding Soldered welded bonded Binding Currentcarrying busses Brush Slider Current Rheostats, pickoffs of potentioelectrical meters and welding code machines senders Commutating Trolley Separable Current pickoffs of cranes and transport Relay Breaking Plug connectors and circuit breakers... Sliding Contacts 369 9.1 Tribology of Electrical Contacts 369 9.1.1 Interrelation of Friction and Electrical Processes 370 9.1.2 Role of Boundary Films 371 9.1.3 Main Means of Improving Reliability of Sliding Contacts 371 9.1.4 Tribophysical Aspects in the Development of Sliding Contacts 373 9.2 Dry Metal Contacts 376 9.2.1 Low-Current Contacts . 79 4.1.1.9 Nickel 80 4.1.2 Metals and Alloys for Heavy- and Medium-Duty Contacts 80 4.1.3 Metals and Alloys for Light-Duty Contacts 83 4.1.4 Materials for Liquid-Metal Contacts 85 4.1.5 Spring Contact. breaking power, current, and voltage, there is a great variety of breaking contacts. The breaking contacts can be classified as light-, medium- and heavy-duty: † Light-duty contacts carry very low. circuit breakers Operate under conditions of friction and wear FIGURE 1.1 Classification of electrical contacts. Electrical Contacts: Fundamentals, Applications and Technology4 q 2006 by Taylor & Francis