Electric Contacts: Theory and Application

Front Matter....Pages N1-XV
Introduction. A simplified summary of the theory of stationary electric contacts....Pages 1-7
The contact surface....Pages 7-9
The contact resistance. General theory....Pages 9-11
Calculation of constriction resistances with constant resistivity ϱ in an isotropic material....Pages 11-19
Constriction resistances when conditions deviate from those in § 4, but with ϱ still a constant....Pages 19-26
Introduction to thin films on contacts. Contact cleaning....Pages 27-29
The load bearing contact area as a function of load and elastic and plastic properties of the members....Pages 29-39
The relation between contact load and resistance, particularly at moderate and high load....Pages 40-48
Contact resistance on freshly cleaned rods in air at very small contact loads....Pages 48-52
The inductance of a current constriction. Skin effect....Pages 52-55
Electrodynamic repulsion in a symmetric contact of non-magnetic material....Pages 55-57
The capacitance of a contact. Electrostatic attraction in a contact....Pages 57-60
The relationship between electric potential and temperature in a current constriction which is symmetric with respect to the contact surface; that is, the φϑ -relation....Pages 60-64
The φϑ -relation in cases of dissymmetry....Pages 64-68
Influence of a thin film in the contact on the φϑ -relation. Kohler effect....Pages 69-71
The influence of the Joule heat on constriction resistances in symmetric contacts....Pages 71-78
Distribution of the temperature in a symmetric constriction with circular contact surface at given current....Pages 78-80
The (equilibrium) temperature distribution in the constriction of a contact between two metals with different conductivities, both obeying Wiedemann-Franz law. Thermoelectric effects....Pages 80-85
Temperature distribution in the constriction of a contact between members of very different conductivities....Pages 85-86
Resistance-voltage characteristics of clean symmetric contacts. Softening and melting voltages....Pages 87-92
Development of the temperature in a metallic current constriction....Pages 92-102
Growth of films on metals used for contacts, near room temperature....Pages 102-111
Growth of visible oxide films on metals at moderate to high temperature. Decomposition at still higher temperature....Pages 111-114
Water film, local cells and rusting....Pages 114-116
Alien solidified films on contacts....Pages 116-118
Tunnel effect....Pages 118-134
Fritting of tarnish films....Pages 135-152
Adherence in dry contacts which are not heated to any influential extent by the current....Pages 153-159
Adherence in contacts that are heated by the current passing through them. Resistance welding....Pages 160-164
About stationary contacts in practice....Pages 164-176
Dimensioning a contact with respect to its heating....Pages 176-180
Contact effects in carbon granular microphones....Pages 180-184
Contact with semiconductors. Rectification. Static electrification....Pages 185-190
Carbon-pile rheostats. Electric resistance of pressed metal powders....Pages 190-192
Thermal metallic contacts....Pages 193-198
Survey of fundamentals....Pages 199-205
Sliding contacts in air....Pages 205-209
Boundary lubrication....Pages 209-221
Theory of friction and wear of carbon contacts. Lubrication by means of solid lubricants as graphite and molybdenum disulfide....Pages 221-228
Stick-slip motion. The temperature in currentless sliding contacts....Pages 228-232
Frictional wear in metallic contacts without current....Pages 232-242
Electrical performance of carbon brushes on rings and commutators when arcing is excluded....Pages 242-248
The temperature in the sliding contact between a carbon brush and a copper ring or commutator....Pages 249-251
Friction and wear with a carbon-brush collector contact....Pages 251-259
Theory of commutation with special regard to voltage flashes and arcs....Pages 260-268
Current collectors for trolley cars....Pages 268-269
Electric noise in contacts....Pages 269-273
Introduction....Pages 274-274
Ignition of arcs in switches....Pages 275-279
 VI -characteristics of the stationary arc in air; their use for calculation of the duration of drawn short arcs....Pages 279-286
Vacuum arc; particularly its extinction....Pages 286-289
Interrupting an alternating current....Pages 290-297
Breaking direct current....Pages 297-298
Electric oscillations generated by d . c . arcs....Pages 298-300
Bouncing....Pages 300-304
Material transfer in switching contacts. A survey....Pages 304-313
Discharge transients....Pages 313-315
Arc duration during contact closure with voltages below 200 to 300 V....Pages 316-320
Floating....Pages 320-322
Arc duration on breaking contact without quenching. Circumstances common to Communication Engineering....Pages 323-325
Quenching a drawn arc by means of a capacitor, parallel to the contact....Pages 325-328
Capacitive quenching when an arc with a very small duration or no are is drawn....Pages 329-332
Quenching of arcs by a resistance parallel to the operating contact or to the inductive coil....Pages 332-334
Details about the types of arc in relay contacts and the material transfer produced by them....Pages 334-337
Bridge transfer and short arc transfer at contact separation....Pages 338-347
Theory of the bridge transfer....Pages 347-354
Bridge material transfer in the shape of pips and spires....Pages 354-356
Mercury switches....Pages 356-359
Application of statistics to contact operations....Pages 359-362
The choice of contact material; contact shape for practical applications....Pages 362-366
Erratum to: The capacitance of a contact. Electrostatic attraction in a contact....Pages 483-483
Erratum to: The relationship between electric potential and temperature in a current constriction which is symmetric with respect to the contact surface; that is, the φϑ -relation....Pages 483-483
Erratum to: The influence of the Joule heat on constriction resistances in symmetric contacts....Pages 483-483
Erratum to: The (equilibrium) temperature distribution in the constriction of a contact between two metals with different conductivities, both obeying Wiedemann-Franz law. Thermoelectric effects....Pages 483-483
Erratum to: Resistance-voltage characteristics of clean symmetric contacts. Softening and melting voltages....Pages 483-483
Erratum to: Tunnel effect....Pages 483-483
Erratum to: Fritting of tarnish films....Pages 483-483
Erratum to: Dimensioning a contact with respect to its heating....Pages 483-483
Erratum to: Thermal metallic contacts....Pages 483-483
Erratum to: Survey of fundamentals....Pages 483-483
Erratum to: Boundary lubrication....Pages 483-483
Erratum to: Frictional wear in metallic contacts without current....Pages 483-483
Erratum to: The temperature in the sliding contact between a carbon brush and a copper ring or commutator....Pages 483-483
Erratum to: Friction and wear with a carbon-brush collector contact....Pages 483-483
Erratum to: Quenching of arcs by a resistance parallel to the operating contact or to the inductive coil....Pages 483-483
Erratum to: Details about the types of arc in relay contacts and the material transfer produced by them....Pages 483-483
Erratum to: Bridge transfer and short arc transfer at contact separation....Pages 484-484
Erratum to: Theory of the bridge transfer....Pages 484-484
Erratum to: Mercury switches....Pages 484-484
Back Matter....Pages 367-482