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 laminated carbon brush for a liquid pump motor slides in a liquid fuel on a disk-like commutator. The laminated carbon brush includes two layers of a lower resistivity layer and a higher resistivity layer. In both the lower resistivity layer and the higher resistivity layer, circular directional resistivities of the brush along a circular direction in the rotation of the commutator are higher than non-circular directional resistivities of the brush along a radial direction of the commutator and a perpendicular direction to the sliding surface of the commutator. A non-circular directional resistivity of the higher resistivity layer are higher than or equal to 90,000.Math.cm. No spark discharges occur if the fuel pump motor is operated to output a high power.

Systems and methods to mitigate electrical voltage on a rotating shaft in an oil rich environment exposed to a viscous fluid or immersed in oil are disclosed. An example grounding brush assembly includes a plurality of conductive filaments configured to extend through the viscous medium surrounding the rotating shaft to be in electrical contact with the rotating shaft when the brush assembly is disposed proximate the shaft.

Methods and apparatus for electrical measurement are disclosed. An example electrical measurement device includes a conductive cable comprising a plurality of conductive filaments on a first end and an electrical connector on a second end, a cable mount that includes a base and an adjustable support attached to the base and the conductive cable to hold the plurality of conductive filaments in contact with a rotating element of a device under test during a measurement operation, with the conductive cable forming a portion of a circuit when the plurality of conductive filaments are in contact with the rotating element of the device under test and the electrical connector is in contact with an output.

A slip ring arrangement comprises a brush with a first contact material on the surface, which rests on a slideway with a second contact material on the surface. The slideway further comprises a layer with a third contact material beneath the second contact material. In this case, the abrasion of the brush is lower than that of the second contact material in the case of a sliding contact between the brush and the second contact material. In the case of a sliding contact between the brush and third contact material, the abrasion of the brush is higher than that of third contact material. As a result, the second contact material of the slideway is degraded first, which corresponds to the normal service life of a slideway. Subsequently, the brush is worn off relative to the third contact material, by means of which a further considerable extension in the service life is achieved.

A slip ring arrangement comprises a brush with a first contact material on the surface, which rests on a slideway with a second contact material on the surface. The slideway further comprises a layer with a third contact material beneath the second contact material. In this case, the abrasion of the brush is lower than that of the second contact material in the case of a sliding contact between the brush and the second contact material. In the case of a sliding contact between the brush and third contact material, the abrasion of the brush is higher than that of third contact material. As a result, the second contact material of the slideway is degraded first, which corresponds to the normal service life of a slideway. Subsequently, the brush is worn off relative to the third contact material, by means of which a further considerable extension in the service life is achieved.

The current invention, by using a plurality of conductive fiber brush bundles and a coaxial line to transfer RF signal(s) between relatively rotatable objects, creates easy-maintenance, long duration a RF rotary joint with soft contacting rotational interfaces. It consists of a stationary shield conductor assembly, a stationary core conductor assembly, a rotational shield conductor assembly with a tapered round head, a rotational core conductor assembly with a tapered round head, and rotational and stationary insulating assemblies with a central bore. Both stationary and rotational shield conductor assemblies having a conductive fiber brush bundle, which further containing a plurality of hair-thin conductive filaments to form a symmetrical flexible tube. The interfaces of the core soft contacting rotational and the shield soft contacting rotational are formed between the free end portions of the conductive fiber brush bundles and the tapered round head of the rotational cone conductor and rotational shield conductor respectively.

The current invention, by using a plurality of conductive fiber brush bundles and a coaxial line to transfer RF signal(s) between relatively rotatable objects, creates easy-maintenance, long duration a RF rotary joint with soft contacting rotational interfaces. It consists of a stationary shield conductor assembly, a stationary core conductor assembly, a rotational shield conductor assembly with a tapered round head, a rotational core conductor assembly with a tapered round head, and rotational and stationary insulating assemblies with a central bore. Both stationary and rotational shield conductor assemblies having a conductive fiber brush bundle, which further containing a plurality of hair-thin conductive filaments to form a symmetrical flexible tube. The interfaces of the core soft contacting rotational and the shield soft contacting rotational are formed between the free end portions of the conductive fiber brush bundles and the tapered round head of the rotational cone conductor and rotational shield conductor respectively.

A grounding rope assembly for electrically grounding a rotatable conductive shaft of a dynamo-electric machine. The assembly includes a grounding rope member including a plurality of conductive wires extending along the length of the grounding rope member and one or more discrete fixation points intermediate the first and second ends of the grounding rope member. Two or more of the plurality of conductive wires are affixed together at each of the discrete fixation points.

A grounding rope assembly for electrically grounding a rotatable conductive shaft of a dynamo-electric machine. The assembly includes a grounding rope member including a plurality of conductive wires extending along the length of the grounding rope member and one or more discrete fixation points intermediate the first and second ends of the grounding rope member. Two or more of the plurality of conductive wires are affixed together at each of the discrete fixation points.