Metallurgical aspects of contact materials for vacuum switching devices

Frey, Philipp; Klink, N.; Michal, R.; Saeger, K.E.

doi:10.1109/27.41194

Cited by 53 publications

(8 citation statements)

References 1 publication

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“…They found that the number of droplets in the gap at current zero increased by a factor of 10 when the sinusoidal current peak was increased from 2 to 4 kA. Furthermore, an arc-time threshold was observed by Frey et al [18] for Ag-WC 40/60 with AC4 electric life tests at a breaking current of 1500 A and a full contact gap of 2 mm. When they increased the arc time, they found that the mass erosion rate increased in conjunction with an increase in the flux of droplets.…”

Section: B Production Of Droplets From Pure Versus P-m Materialsmentioning

confidence: 82%

Influence of contact geometry and current on effective erosion of Cu-Cr, Ag-WC, and Ag-Cr vacuum contact materials

Schulman

Slade

Loud

et al. 1999

IEEE Trans. Comp. Packag. Technol.

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Effective ac erosion rates were measured for Cu-Cr, Ag-WC, and Ag-Cr butt-type contacts in vacuum contactors, using half-cycle current pulses of 450-600 A rms. The polarity was changed for each operation to ensure uniform effects for both contacts. The contacts parted during the rising current, with the full gap set to 10-30% of the contact diameter. The effective linear volume erosion rate [cm 3 /C] was determined by measuring the axial erosion of the contacts versus the number of operations. This was converted to an effective mass erosion rate [ g/C], which was significantly smaller than the reported absolute cathode erosion rate based on measured loss of cathode mass with long square current pulses at large fixed gap. The effective erosion rate increased when spiral-slotted contacts were used. The dependence of the effective erosion rate on the gap was studied, and also the distribution of metal droplets on the arc shield. Most of the droplet flux from the gap was close to the plane of the cathode, while a large fraction of the ionized vapor from the cathode spots was deposited onto the anode. The droplets were a significant fraction of the cathode material loss and the overall effective erosion.

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Section: B Production Of Droplets From Pure Versus P-m Materialsmentioning

confidence: 82%

Influence of contact geometry and current on effective erosion of Cu-Cr, Ag-WC, and Ag-Cr vacuum contact materials

Schulman

Slade

Loud

et al. 1999

IEEE Trans. Comp. Packag. Technol.

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“…During the switching operation, a vacuum arc is generated in the vacuum interrupter and the Cu-Cr contact alloy is heated by plasma; then a surface melt layer is formed and the original microstructure of the surface layer is evolved [3,4,[10][11][12][13][14]. As a result, the dielectric strength of the contact is enhanced after a certain period of the breakdown.…”

Section: Introductionmentioning

confidence: 99%

Liquid phase separation of Cu–Cr alloys during the vacuum breakdown

Wei

Wang

Yang

et al. 2011

Journal of Alloys and Compounds

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“…They found that the melt depth on the surface of the Cu-Cr contacts was about 150 µm under a high-vacuum current arc. Frey et al [11] discussed selection criteria for the type of contact material on the basis of experimental results and also showed the microstructural details of the contact materials after arcing. Wei et al [12] revealed that liquid phase separation was involved in the microstructure evolution of Cu-Cr alloys during a series of vacuum breakdowns and that a Cr phase, comprising spheres and sheets, forms in the melt layer.…”

Section: Introductionmentioning

confidence: 99%

Anode Erosion Pattern Caused by Blowing Effect in Constricted Vacuum Arcs Subjected to Axial Magnetic Field

Tian

Geng

et al. 2015

IEEE Trans. Plasma Sci.

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The objective of this paper is to investigate the anode erosion pattern caused by the blowing effect in constricted vacuum arcs under an axial magnetic field (AMF). The blowing effect was reflected from the microstructure of the melt layer on the anode. A pair of 42-mm-diameter AMF contacts were installed inside a detachable vacuum chamber. The contact material was CuCr25 (25% Cr). The arc modes were observed with a high-speed charge-coupled device video camera. The anode surface temperature after current zero was measured with a two-color pyrometer. The microstructure of the cross section of the anode surface melt layer was observed by scanning electron microscopy. The experimental arc currents increased from 10.5 to 17.8 kA (rms) with an interval of 2 kA. The results show that the anode erosion pattern in constricted arcs is caused by an interactive process of thermal and mechanical effects. The constricted arc columns melted the anode surface material and blew the molten material from the center to the peripheral region. The redistribution of the anode molten layer caused by this blowing effect formed two erosion regions on the anode surface. The depth of the melt layer in the central region was less than 100 µm, but in the peripheral region it was in the range of 100-400 µm. In these different erosion regions of the anode melt layer, there was considerable variation in both size and shape of the Cr sphere. Moreover, the thermal and mechanical effects of the constricted arc redistributed the Cr content of the molten layer on the anode surface. The Cr content in the central region (Erosion Region I) increased to 31% and in the periphery region (Erosion Region II) it decreased to 18%, respectively, from 25% before the experiments.

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Metallurgical aspects of contact materials for vacuum switching devices

Cited by 53 publications

References 1 publication

Influence of contact geometry and current on effective erosion of Cu-Cr, Ag-WC, and Ag-Cr vacuum contact materials

Influence of contact geometry and current on effective erosion of Cu-Cr, Ag-WC, and Ag-Cr vacuum contact materials

Liquid phase separation of Cu–Cr alloys during the vacuum breakdown

Anode Erosion Pattern Caused by Blowing Effect in Constricted Vacuum Arcs Subjected to Axial Magnetic Field

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