Werner Rieder

The influence of composition and Cr particle size of Cu/Cr contacts on chopping current, contact resistance, and breakdown voltage in vacuum interrupters

A range of commercially produced Cu/Cr materials with different compositions (25% to 75% Cu) and Cr particle sizes (up to 160 mu m) has been investigated for their differences in chopping currents, contact resistance, breakdown voltage, contact erosion, and contact appearance. Test parameters have been chosen to reflect actual switching conditions. The properties of the Cu/Cr contact materials have been investigated after prestressing the electrodes with defined numbers of break arcs of 1 and 5 kA with alternating and unchanged polarity. It was found that the differences in properties of Cu75/Cr25 and Cu50/Cr50 contacts are minor as long as the same Cr particle size is used. Fine Cr particles increased the breakdown voltage and the rise in breakdown voltage after prestressing and the total erosion of contacts. While the mean chopping current values remained almost unaffected by fine Cr particles, the maximum values of chopping currents were deceased by using fine Cr particle sizes. Contact resistance and cathode surface structure after prestressing remained unaffected by a change in Cr particle size. >

N-aryl sulfimides☆

Abstract N-Aryl sulfimides with various substituents at the aromatic ring and various alkyl or aryl groups at the S atom have been synthesised in high yields by applying three different procedures: reactions of anilines with sulfides and (A) N-chloro-succinimide, (B) t-butyl hypochlorite or (C) sulfuryl chloride. These reactions offer remarkable advantages compared to the known sulfoxide-P4O10 method for preparation of N-aryl-sulfimides. Mechanistic considerations are discussed. N-Aryl-sulfoximides have been obtained by oxidation of N-aryl-sulfimides and by reaction of anilines with DMSO and t-butyl hypochlorite or sulfuryl chloride. Mass spectra of N-aryl-sulfimides are also discussed.

Influence of electrical and mechanical parameters on contact welding in low power switches

A model switch has been developed to investigate the influence of kinetic parameters, as contact velocity and contact force, on contact welding under conditions prevailing in relays, micro switches etc. Both frequency and intensity of the statistically scattering weld forces increased with increasing arc duration and current. Pre-strike and bounce arcs show identical results under corresponding conditions. Both frequency and intensity of the statistically scattering weld forces initially increased and then decreased with increasing impact velocity. Increasing the static contact force hardly influenced the strength of the primary weld after impact but reduced or prevented weakening of the weld by a following bounce process. The results agree with the predictions of a mathematical model proposed. The configuration of the load circuit determining the actual arc current curve essentially influences the weld force values.

Make erosion mechanism of Ag/CdO and Ag/SnO/sub 2/ contacts

The reason for the different make-erosion behavior of contactor contacts made from Ag/CdO and Ag/SnO/sub 2/, respectively, has been investigated at 400 A, separating the combined effects of the thermal stress due to the bounce arc and of the mechanical stress due to contact closure. It appeared that neither arcing without mechanical stress nor no-load switching without arcing are able to produce serious mass losses. Only the combined action of bounce arcs followed by mechanical impacts cause severe erosion phenomena, which is more pronounced in Ag/SnO/sub 2/ contacts, losing more obviously weakly adhering matter due to mechanical effects. >

Electrical characteristics of various contact contaminations

Contact reliability may be endangered by various types of contact contaminations as particles, corrosion products, polymers or carbon deposits. Often information about the type of contamination may be gained by easily applicable measurements of current and contact voltage only: i.e., contact resistance measurements after each operation of a routine life test (employing increasing voltage and current), and voltage oscillograms across opening contacts. >

The influence of bounce parameters on the make erosion of silver/metal-oxide contact materials

Make erosion of contacts made from powder metallurgically produced Ag/CdO and three differently produced Ag/SnO/sub 2/ materials was investigated employing both a commercial contactor and a new bounce model switch. Additional tests were executed in a fixed gap arrangement in order to study separately the influence of the thermal stress due to the bounce arc only. The bounce model switch was developed to simulate contact bounces at well-defined and reproducible but independently variable values of bounce duration, bounce height, and contact force. The influence of the bounce parameters (bounce arc duration, bounce height and static contact force, current and magnetic induction) on the make only erosion was investigated by systematic variation of each single parameter value in the bounce model switch. The Ag/SnO/sub 2/ materials suffered either three times higher or about 50% lower erosion losses than powder metallurgically produced Ag/CdO, depending on the manufacturing process (internally oxidized, powder metallurgically produced) and/or the additives of the materials, and therefore on the structure of the materials rather than on the kind of the main metal oxide component (CdO or SnO/sub 2/. The different make erosion rates of the materials investigated have been correlated with the micro structure of their stressed surfaces. >

Relay life tests with contact resistance measurement after each operation

Modern reliability requirements for relays cannot be satisfied unless the contact resistance is measured after each operation of the life test. A test device was developed to execute these measurements and a special method was applied to reduce the resulting amount of data effectively without losing information. Commercial relays were investigated at intermediate and low power levels. Characteristic contact resistance patterns during the total life of a relay were recorded depending on both the contact material and the electrical stress. Typical statistical patterns characterizing the behavior of homogeneous materials (Au, Ag/Ni 0.15) and heterogeneous materials (Ag/CdO, Ag/SnO/sub 2/), erosion of contact platings, contact contamination, and the behavior of bifurcated contacts were recognized. >

Die Dissoziation von Permanganation durch lokale Energiezufuhr

Die Moglichkeit der lokalen Energiezufuhr zu bestimmten Atomen durch Atomkernreaktionen wird aufgezeigt. Die Anregung von Permanganation mit Energien der Grosenordnung 1000 kcal durch Beschiesung mit langsamen Neutronen und Einfang der Neutronen durch Mn (Szilard-Chalmers-Effekt) wird experimentell durchgefuhrt. Das entstehende Radio-Mn (Mn*) liegt nach Ende der Bestrahlung teils als Mn*Oa, teils als Mn*O4− vor. Die Untersuchung der Abhangigkeit des Verteilungsverhaltnisses (“Retention”) von den Versuchsbedingungen (Neutronenenergie, pH-Wert, Aggregatzustand, Konzentration, Temperatur, Anwesenheit von Fremdionen in Losung oder in einem Mischkristall) fuhrt im Einklang mit einer HypotheseLibbys zu dem Ergebnis, das bei der Zerstorung des Anions Mn*O4− (Primarprozes) keine Reduktion des Mn* mit Abdissoziation von Sauerstoffatomen, sondern eine Abdissoziation von Sauerstoffionen unter Hinterlassung eines Kations stattfindet. Das instabile Kation des Typus Mn*O3+ verliert bald die im Primarprozes erworbene kinetische Energie und setzt sich in einem “thermischen” Sekundarprozes mit Molekulen des Mediums zu Mn*O2 oder Mn*C4− um. Diese chemische Stabilisierung der Primarprodukte verlauft innerhalb unmesbar kurzer Zeit, wenn Losungen bestrahlt werden, jedoch mit mesbarer temperaturabhangiger Geschwindigkeit, wenn die Primarprodukte in einem Kristallgitter eingeklemmt sind. Die Stabilisierungsreaktionen werden diskutiert.

Configurationally and conformationally homogeneous cyclicN-aryl sulfimides. I. Synthesis and mechanism of formation

Reactions of thianes andcis-andtrans-1-thiadecalins with 4-chloroaniline andN-chlorsuccinimide ortert-butylhypochlorite gave configurationally homogeneous cyclicN-4-chlorophenyl sulfimides. With appropriately substituted sulfides conformationally homogeneous thiane-and cis-1-thiadecalin-1-imides were obtained. Formation of sulfimides with axially oriented S−N bond is strongly disfavoured. Reactions with conformationally rigid ring systems yielded only sulfimides with equatorial S−N bond; two isomeric sulfimides, both with equatorial S−N bond, were obtained with the mobilecis-1-thiadecalin. Sulfimides with axial S−N bond were prepared from conformationally rigid sulfoxides with equatorial S−O bond. It is assumed that formation of sulfimides with rigid ring systems proceeds viaN-chloroanilines, while reactions of conformationally mobile systems withN-chlorosuccinimide may also occur via intermediate succinimidyl sulfonium ions.ZusammenfassungDurch Umsetzung von Thianen und voncis- undtrans-1-Thiadekalinen mit 4-Chloranilin undN-Chlorsuccinimid odertert-Butylhypochlorit wurden konfigurativ einheitliche cyclischeN-4-Chlorphenylsulfimide dargestellt. Bei geeigneter Substitution am Heteroring wurden konformativ einheitliche Thianundcis-1-Thiadekalin-1-imide erhalten. Die Bildung von Sulfimiden mit axial orientieter S−N-Bindung ist stark benachteiligt. Konformativ starre Ringsysteme führen praktisch ausschließlich zu den Sulfimiden mit äquatorialer S−N-Bindung; aus dem konformativ beweglichencis-1-Thiadekalin werden bei der Umsetzung mittert-Butylhypochlorit zwei isomere Sulfimide, beide mit äquatorialer S−N-Bindung, erhalten. Sulfimide mit axialer S−N-Bindung wurden aus konformativ starren Sulfoxiden mit äquatorialer S−O-Bindung erhalten. Es wird angenommen, daß die Sulfimidbildung bei konformativ starren Ringsystemen weitgehend überN-Chloraniline, bei Umsetzung von beweglichen Ringsystemen mitN-Chlorsuccinimid auch über Succinimidylsulfoniumionen verläuft.

Carbon contamination of contacts due to organic vapors

The formation of carbon on the contact surface of commercial relays by thermal decomposition of organic vapors emanating from various organic materials may cause an undesirable increase of the contact resistance of the order of several ohms. A model switch was developed to investigate the influence of outgassing vapors of any organic material on contact reliability. Carbon deposits on contact surfaces cause certain phenomena confirming that the observed characteristic contact resistance increase to a value of the order of several ohms is caused by elementary carbon. Investigations of various organic materials showed that their contact compatibility cannot be derived just from the qualitative knowledge of their emanating vapors, but that the problem is more complex and requires a quantitative approach. >