Abb Research Ltd.

Asea Brown Boveri Inc.

Forschungszentrum Julich Gmbh

Ralf Strumpler

Felix Greuter

Joachim Glatz-Reichenbach

Claus Schuler

Jorgen Skindhoj

Hans Luth

Tudor Baiatu

Henning Fuhrmann

Martin Thiele

Harald D Muller

Anton Demarmels

Jan H Kuhlefelt

Friedrich Konig

Zdenek Pelanek

Gerhard Mauthe

A compressor includes a compressor wheel, a diffuser and a device for the wet cleaning of the diffuser of a compressor, the diffuser being arranged downstream of the compressor wheel in the flow direction of the medium to be compressed. The device includes an arrangement for injecting a liquid, which is arranged in such a way that the liquid can be introduced, downstream of the compressor wheel, to the diffuser. The diffuser has at least partially a non-stick coating. A device of this type is suitable for removing deep-seated deposits from the surface of the diffuser.

Compressor cleaning system

The resistor body of a nonlinear resistor element having PTC characteristics includes a pulverulent first filler, whose material, e.g. TiB.sub.2, TiC, VC, WC, ZrBr.sub.2, MoSi.sub.2, has a specific conductivity of at most 10.sup.-3 .OMEGA.cm and in which the particle sizes are between 10 and 40.mu., and also, in order to improve the voltage sustaining capability by extending the switching zone and to achieve uniform energy absorption, includes a likewise pulverulent second filler having varistor characteristics and particle sizes between 50 and 200.mu., whose specific resistance at field strengths .gtoreq.2000 V/cm such as occur in the switching region of the resistor element and above, is at most 50 .OMEGA.cm, preferably at most 15 .OMEGA.cm, the fillers being embedded in a matrix made of a thermoplastic, in particular HD polyethylene or a thermoset. The average particle size of the second filler should exceed that of the first filler by a factor of from 2 to 5. A potentially particularly suitable material for the second filler is SiC doped with Al, B, Ga, In, N, P, As, as is similarly doped ZnO.

Resistor element

The current-limiting resistor has two connection electrodes (1, 2) which are arranged parallel to one another, a resistance body (3) which has PTC behavior and with which large-area contact is made by the connection electrodes (1, 2) and at least one varistor (4) which is in electrically conductive contact with the resistance body (3). The varistor (4) is of pillar-shaped design and has at least two first portions (4a) routed predominantly perpendicularly to the varistor axis and, arranged between said portions, a second portion (4b) having a reduced cross section compared with each of the first portions (4a). The material of the resistance body (3) fills an interspace (6), which is formed by the at least two first portions (4a) and the second portion (4b), and encloses the outwardly pointing edges (4c) of the at least two portions. This resistor can be operated at high voltages, for example 5 or 10 kV, and advantageously has a single resistance body 3 and a single varistor. This obviates metal electrodes serving to make electrical contact with subelements.

Current-limiting resistor having PTC behavior

The electrically and thermally conductive plastic contains a polymer and a filler embedded in the polymer, based on a semiconducting material having by doping a predetermined intrinsic electrical conductivity. The filler content is chosen such that the electrical conductivity of the plastic remains largely unchanged in the case of an increase in the filler fraction. This plastic is distinguished by high thermal and electrical--but nonmetallic--conductivity and can be used advantageously for embedding the carrier material of a laminate serving in electrical machine construction for supporting the stator windings of large rotating machines.

Electrically and thermally conductive plastic and use of this plastic

The current-limiting resistor has two connection electrodes (1, 2) which are arranged parallel to one another as well as a resistance body (3) which has PTC behavior and with which large-area contact is made by the connection electrodes (1, 2). A varistor (40) is in electrically conductive contact with the resistance body (3). The resistance body (3) contains two contact areas (50, 51) as well as a response point (60) which is connected in parallel with the varistor (40) via the two contact areas (50, 51) and implements a PTC transition above a threshold value of a current flowing through the resistor. Since the resistance body effects the electrical contact with the varistor (40) in the case of this resistor, no metal connection electrodes are required for the varistor. At the same time, due to the outward displacement of the response point (60) away from the varistor (40), the operational reliability of the resistor is considerably improved. Effective current limiting in load circuits which are operated at high voltage can be achieved by a series circuit formed by a plurality of varistors (40, 41, . . . ) provided in a resistance body (3) which is designed in the form of a meander or is of some other continuous design.

A varistor and a PTC resistor formed from a composite material containing a polymer matrix and a filler. The varistor experiences two nonlinear changes caused by the current due to applied voltage, the varistor comprising a composite material comprising a filler and a polymer matrix, the filler consisting of particles of grained microstructure. The PTC resistor experiences a first nonlinear dependency of resistivity at a first PTC temperature resulting from an interaction of the filler and the polymer matrix and a second nonlinear dependency of resistivity at a second, lower PTC temperature resulting from the filler.

Composite material

The electrical resistance element (10) includes a resistance body (3), which is arranged between two plane-parallel, pressurized electrodes (1, 2), has PTC behavior and comprises a polymer matrix and two filler components of electrically conducting particles embedded into the polymer matrix (4). When a short-circuit current occurs, the resistivity of the resistance body (3) changes abruptly above a temperature limit value in a surface layer resting on the electrodes and containing at least a first of the two filler components. A second of the two filler components is selected such that a composite material containing at least the polymer matrix and the second filler component has PTC behavior, with an abruptly changing behavior greater by at least one order of magnitude in comparison with the surface layer. At the same time, this composite material has a resistivity which is lower by at least one order of magnitude than a composite material formed by the polymer matrix and the first filler component. The resistance element has a high nominal current carrying capacity and can limit large short-circuit currents permanently.

Electrical resistance element and use of this resistance element in a

An electrical resistance element having a resistance body between two contact terminals. The resistance body has PTC behavior and is composed of a polymer matrix and a filler component embedded in the polymer matrix. The filler component is composed of electrically conducting particles. Although the element is of simple and inexpensive construction, the resistance element is notable for good electrical conductivity in the low-resistance state and for a low response time for the PTC transition from the low-resistance to the high-resistance state. This is achieved as a result of the fact that at least some of the electrically conducting particles are formed as composite bodies having electrically conducting surfaces and/or as hollow or porous bodies composed of electrically conducting material. These particles have a lower specific density and/or lower specific heat capacity than solidly formed particles composed of conductive material.

Electrical resistance element

A current-limiting component having an electrical resistance body arranged between two contact terminals. The resistance body contains a first resistance material having PTC behavior. Below a limit temperature, the first resistance material has a low cold resistivity and at least one current-carrying path extending between the two contact terminals. Above the limit temperature, the first resistance material has a high hot resistivity compared with its cold resistivity. The current-limiting component has uniform switching capability and high rated current-carrying capacity despite simple and inexpensive construction. The resistance body additionally contains second resistance material having a resistivity which is between the cold resistivity and the hot resistivity of the first resistance material. The second resistance material is in intimate electrical contact with the first resistance material and forms at least one resistance path connected in parallel with the current-carrying path.

Current-limiting component

An electric resistor has a resistor body arranged between two contract terminals. This resistor core includes an element with PTC behavior which, below a material-specific temperature, forms an electrically conducting path running between the two contact terminals. The resistor can be simple and inexpensive, but still have a high rate current-carrying capacity protected against local and overall overvoltages. This is achieved by the resistor core additionally containing a material having varistor behavior. The varistor material is connected in parallel with at least one subsection of the electrically conducting path, forming at least one varistor, and is brought into intimate electrical contact with the part of the PTC material forming the at least one subsection. The parallel connection of the element with PTC behavior and the varistor can be realized both by a microscopic construction and by a macroscopic arrangement.

Resistor with PTC behavior

An optoelectronic device, e.g. for integrated circuits, has an Si, II-VI or III/V semiconductor layer and an LaF.sub.3 or La.sub.1-x X.sub.x F.sub.3 insulating layer which is doped with Nd or Er to generate an optical signal whose wavelength is determined by the 4f ions used. The insulating layer can be grown epitaxially on the semiconductor layer and the lanthanide element ion substituting for a metal ion of the material forming the insulating layer has the same valence as the metal for which it is substituted.

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Baden, Switzerland

Ralf Strumpler