The invention includes a stator disposed inside a yoke, an armature supported inside the stator, a commutator connected to the armature and having a sliding surface in an outer peripheral portion, and a brush disposed opposing the commutator and having a sliding contact surface that comes into sliding contact with the sliding surface of the commutator, wherein the brush has a first member, and a second member with an electrical resistance value higher than that of the first member, the first member is disposed on an entrance side and the second member on an exit side with respect to a direction of rotation of the commutator, and the sliding contact surface of the brush is such that an inclined portion that inclines toward the entrance side with respect to the direction of rotation of the commutator is formed in the first member.

A DC motor is provided for use in a starter that starts an ermine. The DC motor includes a commutator and a brush. The commutator is formed of copper or a copper alloy whose copper percentage content is higher than or equal to 99 mass %. The brush is arranged in sliding contact with a surface of the commutator. Moreover, the brush is formed of a sintered compact that contains graphite, copper and at least one metal sulfide solid lubricant. The percentage content of copper in the sintered compact is 30-70 mass %. The at least one metal sulfide solid lubricant includes tungsten disulfide. The percentage content of tungsten disulfide in the sintered compact is higher than or equal to 6.5 mass %.

A DC motor is provided for use in a starter that starts an ermine. The DC motor includes a commutator and a brush. The commutator is formed of copper or a copper alloy whose copper percentage content is higher than or equal to 99 mass %. The brush is arranged in sliding contact with a surface of the commutator. Moreover, the brush is formed of a sintered compact that contains graphite, copper and at least one metal sulfide solid lubricant. The percentage content of copper in the sintered compact is 30-70 mass %. The at least one metal sulfide solid lubricant includes tungsten disulfide. The percentage content of tungsten disulfide in the sintered compact is higher than or equal to 6.5 mass %.

A computed tomography device includes a slipring for rotational transmission and a feed line. The slipring is arranged to be rotatable relative to the feed line. Two sliding contact elements are further included, forming sliding contacts between a slideway of the slipring and the feed line, the two sliding contacts being connected in parallel with one another and electrically conductively connected together via at least one portion of the slideway and via at least one portion of the feed line. Finally, the computed tomography device includes a measuring apparatus, configured to acquire a measured value dependent on a resultant inductance between the two sliding contact elements; and at least one processor, configured to determine an operating state of the two sliding contacts based upon the measured value.

A discharge device for discharging electric currents from a rotor part of a machine, said rotor part having a shaft, the discharge device comprising an axially displaceable contact element, which is at least partly accommodated in a guide, for forming an electroconductive sliding contact between a sliding contact surface of the contact element and a shaft contact surface of the shaft, the sliding contact surface being provided for forming the sliding contact, the contact element being electroconductively connected to the guide and/or a retaining element of the machine, and the contact element being prestressed towards the shaft contact surface by means of a spring element, the contact element being at least partly wetted with an oily fluid, in particular at least in the area of its sliding contact surface.

A discharge device for discharging electric currents from a rotor part of a machine, said rotor part having a shaft, the discharge device comprising an axially displaceable contact element, which is at least partly accommodated in a guide, for forming an electroconductive sliding contact between a sliding contact surface of the contact element and a shaft contact surface of the shaft, the sliding contact surface being provided for forming the sliding contact, the contact element being electroconductively connected to the guide and/or a retaining element of the machine, and the contact element being prestressed towards the shaft contact surface by means of a spring element, the contact element being at least partly wetted with an oily fluid, in particular at least in the area of its sliding contact surface.

A contacting device for transmitting electric currents of a rotor part of a machine, said rotor part being formed by a shaft and/or slip ring, to a machine, and to the use of a discharge device, wherein the discharge device comprises a contact element for forming an electrically conductive sliding contact between a sliding contact surface of the contact element, said sliding contact surface being provided in order to form the sliding contact, and a rotor contact surface of the shaft or the slip ring, and a recess is formed in the sliding contact surface. The contact element is at least partly coated with an oily fluid, in particular at least in the region of the sliding contact surface.

A method for making contact wires for sliprings comprising the steps of: coating and/or plating a wire with a first metal of the group of nickel, chrome or a combination thereof; coating and/or plating the wire with a second metal of the group of gold, silver, or a combination thereof; delivering laser radiation and generating an interference pattern of the laser radiation to the surface of the wire; heating the surface selectively as defined by the interference pattern, modifying of the crystal structure and/or providing protrusions and/or recesses due to melting and/or evaporation of the surface material.

A method for making contact wires for sliprings comprising the steps of: coating and/or plating a wire with a first metal of the group of nickel, chrome or a combination thereof; coating and/or plating the wire with a second metal of the group of gold, silver, or a combination thereof; delivering laser radiation and generating an interference pattern of the laser radiation to the surface of the wire; heating the surface selectively as defined by the interference pattern, modifying of the crystal structure and/or providing protrusions and/or recesses due to melting and/or evaporation of the surface material.

Provided is a brush arrangement of a wind turbine lightning protection system, realized to provide a current path from a hub to a canopy of the wind turbine, which brush arrangement includes a brush holder arranged to hold a brush in electrical contact with a contact surface at the exterior of the canopy, which contact surface is electrically connected to the hub; a bracket arranged to electrically connect the brush with a mounting plate; characterized by an access opening in the front wall of the canopy, which access opening is dimensioned to accommodate the bracket and brush holder; and a mounting arrangement for securing the mounting plate to the canopy front wall over the access opening, from within the canopy interior. A wind turbine including a lightning protection system with at least one such brush arrangement is also provided.