Abb Research Ltd.

Abb Schweiz Ag

Abb Technology Ag

Reto Kessler

Felix Greuter

Walter Schmidt

Lise Donzel

Thomas Christen

Michael Hagemeister

Jacim Jacimovic

Lorenz Herrmann

Petra Kluge-Weiss

Yvo Dirix

Markus Hoidis

Hansjoerg Gramespacher

Oliver Beck

Eric Denervaud

Lavinia Scherf

The present invention relates to a varistor material for a surge arrester with target switching field strength ranging from 250 to 400 V/mm comprising ZnO forming a ZnO phase and Bi expressed as BiOforming an intergranular bismuth oxide phase, said varistor material further comprising a spinel phase, characterized in that the amount of a pyrochlore phase comprised in the varistor material is such, that the ratio of the pyrochlore phase to the spinel phase is less than 0.15:1.

High field strength varistor material

The disclosure relates to an overvoltage protection means containing ZnO microvaristor particles for protecting electrical elements and a method to produce the means. Single microvaristor particles are placed in an arrangement having a monolayer thickness and are electrically coupled to the electrical element to protect it against overvoltages. Embodiments, among other things, relate to: 1-dimensional or 2-dimensional arrangements of microvaristor particles; placement of single microvaristors on a carrier; the carrier being planar or string-like, being structured, being a sticky tape, having fixation means for fixing the microvaristors, or having electrical coupling means. The monolayered overvoltage protection means allows very tight integration and high flexibility in shaping and adapting it to the electric or electronic element. Furthermore, reduced capacitance and hence reaction times of overvoltage protection are achieved.

Microvaristor-based overvoltage protection

The invention relates to a nonlinear electrical material with improved microvaristor filler (), to devices and electrical apparatuses comprising such nonlinear electrical material and to a production method thereof. According to invention, the filler () comprises larger spherical particles () and smaller irregular particles () that are arranged interstitially and provide non-point-like and/or multiple contact areas () owing to their irregular outer shape comprising edges and faces. Embodiments, among other things, relate to: spherical particles () being calcinated and broken-up to retain their original shape; irregular, spikly shaped, particles () obtained by calcinating or sintering and crushing or fracturing granules or blocks; and addition of a third filler fraction. Advantages, among others, are: higher filler contents, more and more durable inter-particle contacts (), enlarged effective micro-contact area, and improved electrical performance of the nonlinear electrical material.

Nonlinear electrical material for high and medium voltage applications

The polymer compound contains a polymer matrix and a filler embedded in the matrix. The filler comprises two filler components with nonlinear current-voltage characteristics deviating from one another. By selection of suitable amounts of these filler components, a polymer compound with a predetermined nonlinear current-voltage characteristic deviating from these two characteristics can be formed in this way.

Polymer compound with nonlinear current-voltage characteristic and process for producing a polymer compound

The manufacturing method for an electroceramic component (), for example a varistor (), comprises a laser irradiation of a part () of the surface of an electroceramic body () before a metallization () is applied to the part () of the surface. By means of the laser irradiation it is possible to produce a micro-roughness and/or a chemical modification of the surface which permits good adhesion of the metallization, and it is possible to reduce or eliminate areas of unevenness or waviness of that part () of the surface of the electroceramic body () which is to be metallized. In addition, improved transverse conductivity can be produced, by virtue of which a low contact resistance and a very homogeneous current distribution is achieved, in particular near to the metallization (). In addition it is possible to remove residues which originate in particular from a sinter support or from the application of a passivation layer. After the laser irradiation, the electroceramic body advantageously has a border () which adjoins the part () of the surface and which is not laser-irradiated. The laser beam can advantageously be pulsed and focused.

Laser-irradiated metallized electroceramic

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Zurich, Switzerland

Reto Kessler