Electric Contacts: Theory and ApplicationThis book is a completely revised and rewritten edition of "Electric Contacts Handbook" published in 1958. A large number of new in vestigations are considered, and many of the basic theories are revised in detail and even in general. The body of information had to be limited as it was not advisable to increase the volume of the book. In particular, no attempt was made to cover all of the practical applications. They appear as examples following concentrated explanations of basic phenomena. As in several branches of technology, the solutions of problems ari sing in the field of electric contacts involve insight into various disci plines of physics. It is feit that reviews of some of those topics, especi ally adapted to electric contact phenomena, are welcome to many readers. For example, chapters have been devoted to the structure of carbon, the band theory of electric conduction in solids, certain pro blems in statistics, and the theory of the electric arc. As regards arc problems, new ideas have been introduced. In order to make the main text less cumbersome, such reviews are presented as appendices. Throughout this edition, the mksa-unit system is used in accord with the latest recommendation for standardization of units in scientific and technical writings. The chapter "History of Early Investigations on Contacts" forming Part IV in the preceding edition of 1958 has not been repeated in this book. |
Contents
| 7 | |
Constriction resistances when conditions deviate from those in 4 | 19 |
Introduction to thin films on contacts Contact cleaning | 27 |
The relation between contact load and resistance particularly at moderate | 40 |
Contact resistance on freshly cleaned rods in air at very small contact loads | 48 |
The inductance of a current constriction Skin effect 22 | 52 |
The relationship between electric potential and temperature in a current | 60 |
Influence of a thin film in the contact on the yrelation KOHLER effect | 69 |
Theory of commutation with special regard to voltage flashes and arcs | 260 |
Current collectors for trolley cars | 268 |
Part IV | 274 |
51 Vacuum arc particularly its extinction | 286 |
Breaking direct current | 297 |
Material transfer in switching contacts A survey | 304 |
57 Discharge transients | 313 |
Arc duration on breaking contact without quenching Circumstances | 323 |
Distribution of the temperature in a symmetric constriction with circular | 78 |
Temperature distribution in the constriction of a contact between mem | 85 |
Development of the temperature in a metallic current constriction | 93 |
Growth of films on metals used for contacts near room temperature | 102 |
Water film local cells and rusting | 114 |
Fritting of tarnish films | 135 |
Adherence in dry contacts which are not heated to any influential extent | 153 |
Adherence in contacts that are heated by the current passing through | 160 |
Dimensioning a contact with respect to its heating | 176 |
Contact with semiconductors Rectification Static electrification | 185 |
Part II | 193 |
Part III | 199 |
Sliding contacts in air | 205 |
Stickslip motion The temperature in currentless sliding contacts | 228 |
The temperature in the sliding contact between a carbon brush and | 249 |
62 Capacitive quenching when an arc with a very small duration or no arc | 329 |
Bridge transfer and short are transfer at contact separation | 338 |
Theory of the bridge transfer | 347 |
Mercury switches | 356 |
70 The choice of contact material contact shape for practical applications | 362 |
Electronic conduction in solids | 380 |
Heat conduction WIEDEMANNFRANZ law WFlaw | 393 |
Structure electrical and thermal conductivity of carbons | 405 |
Hydrodynamic or thick film lubrication | 412 |
Some fundamental formulas concerning electric discharges | 419 |
Tables | 436 |
| 443 | |
| 477 | |
Errata | 483 |
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Common terms and phrases
A-fritting a-spots A₁ according to Eq alien films anode assume atoms average brush calculated carbon cathode circuit clean coefficient cold welding collector film computed conducting constant constriction resistance contact area contact films contact members contact resistance contact spots contact surface contact voltage copper covalent bonds current density curve deformation effect elastic Electric Contacts electric resistance electrons emission energy equipotential surfaces example FERMI level film flow friction fritting graphite hardness heat heat conductivity HOLM 37 ignition increase indentation inductance ions layer load bearing area lubricant material transfer means measurements metallic contact N/m² nominally flat observed obtained oxide PELTIER effect plasma plastic pressure produced radius refer ring room temperature semiconductor silver sliding contacts smaller supertemperature switch T₁ Table thermal thermionic emission thickness THOMSON effect tion tunnel vacuum values vapor wear