EP1133028A2 - Slip-ring arrangement for electrical motors and generators - Google Patents

Abstract

Slip ring arrangement for electric motors and generators, in which brushes made of carbon materials and slip rings (10, 10 ', 10' ') of the slip ring body (11) are connected to one another in an electrically conductive manner, the slip rings (10, 10', 10 ' ') include metallic slip rings (2, 2' and 2 '') of conventional design as a slip ring base and an electrically conductive sliding layer (3, 3 'and 3' ') made of a graphite material, the thickness of which is a maximum of 11% of the radius of the slip ring ( 10, 10 ', 10' ') and the electrically conductive is attached to the circumference of the metallic slip ring base (2, 2' and 2 '') by gluing. Process for retrofitting slip ring bodies with metallic slip rings by removing the metallic slip rings and sticking on a sliding layer. <IMAGE>

Description

The invention relates to slip ring arrangements for electrical machines with brushes made of carbon materials and slip ring bodies, the brushes with the slip rings of the slip ring body are electrically conductive are interconnected.

Electric motors and generators with which electric Energy in rotational energy or vice versa rotational energy is converted into electrical energy Power supply for the rotatably arranged coil, the ver non-positively or positively with the axis of rotation is bound. This is usually done with the axis of rotation connected and concentric slip rings, which are conductively connected with fixed brushes, or about the pairing of brushes with so-called commutators or collectors in addition to manufacturing the electrical Connection between the fixed and the rotating part of the electrical machine also the electricity turn (with DC machines).

The slip rings and commutators usually exist made of metals such as copper, copper alloys such as Bronze, Tin bronze, nickel bronze, silver or steel. The slip rings become slip ring bodies by insulating Fasteners connected to the hub (axis of rotation), being are isolated from each other and from each other. Along the circumference of the slip rings are electrically conductive Brushes arranged in a fixed position, which are connected to the Surface of the slip rings are kept in contact. For AC motors and generators become slip rings required individually or several times per phase.

The sliding contacts (brushes) mostly consist of carbon materials, optionally in combination with metals (e.g. metal graphite, for the production of which mixtures of Metal powders, especially copper, tin or lead, with Graphite, especially natural graphite, pressed and subsequently solidified by annealing or sintering).

With all of these material pairings it comes through the mutual movement and also due to the sometimes high transferred currents to wear, resulting from the Abrasion dusts can form, leading to shortening of the creepage distance due to pollution and thus lead to rollovers can; on the other hand, there is a deduction touching layers. This results from the need replacement of brushes and surface treatment the slip rings (turning off the missing parts such as scoring or the like) additional maintenance intervals, which are shorter than the maintenance intervals of the (rolling) Bearings, which significantly increased maintenance costs above all caused by additional downtime.

It is therefore desirable to keep the abrasion as low as possible hold and so the frequency of the resulting Maintenance work less or at most equal to that Frequency of maintenance work for the bearings and / or to make other wear parts.

From the patent DD 258 687 A1 and from the VEM magazine 1975, p. 15 ff. It is known that in a pairing of Graphite brushes with slip rings made of graphite the wear is very low. However, this system has the disadvantage that because of the graphite body of the slip rings compared to metals of relatively high specific resistance only small currents can be passed through. At high conducted currents becomes the ohmic heat impermissibly high. This can damage the system to lead. The electricity is introduced or discharged at a slip ring over a metallic conductor that parallel to the axis of rotation laterally offset to this and electrically conductive with the body of the slip ring connected is. Because the resistance inside a graphite slip ring of similar size to the contact resistance between the slip ring and the brush, this leads to constant induced current in the coil to periodic Voltage fluctuations in a generator or in a Uneven torque motor depending on the path length of the current and thus the effective resistance in the Slip ring.

Another construction is from the patent DD 248 909 known. Here is a slip ring with a metallic slip ring base and a soldered Carbon guide ring described, the slip ring base Has voids to the heat loss from all sides To be able to remove ventilation. The metallic slip ring base facing side of the coal guide ring must be metallized to have a low contact resistance to ensure and enable a soldered connection. Due to the strong heating of the construction by the Ohmic power loss as well as during soldering thermal stresses occur. Therefore, the outer part of the metallic slip ring base preferably with recesses provided to compensate for thermal stresses.

There is therefore the task of designing for Find slip rings that are as low as possible Wear leads, and on the other hand a sufficiently high Allows current load, so that such systems in High current range can be used without the strong heating known in the prior art occur. Another task is existing machines to be able to retrofit with metallic slip rings so that the wear becomes smaller, with as few parts as possible should be replaced.

This object is achieved by a slip ring construction, which consists of a metallic slip ring of a conventional type as a slip ring base and a sliding layer glued onto this slip ring base, which preferably consists of a carbon material. If a carbon material is used, it is advantageous to use a graphite material, and particularly preferably an isostatically pressed graphite material. Furthermore, the bending strength of the graphite material should preferably be at least 30 MPa (= 30 N / mm ² ) so that the layer thickness of the carbon material can be kept sufficiently low. This construction on the one hand ensures that the contact surface pairing has minimal wear, since the material of the friction partner of the brushes can be selected so that the abrasion between these mutually moving materials is considerably lower than that between a pairing of metals or a pairing with metal and carbon material for the brushes. On the other hand, due to this construction, the contact resistance between the metallic base of the slip ring and the sliding layer is centrosymmetric.

The invention therefore relates to a slip ring arrangement for electric motors and generators in which brushes are made Carbon materials and the slip rings of the slip ring body are electrically connected to each other, characterized in that the slip rings are metallic Slip rings of the usual type (slip ring base) and one electrically conductive sliding layer made of a graphite material include, whose thickness is a maximum of 11% of the outer radius of the slip ring and the electrically conductive on the Scope of the metallic slip ring base by gluing is attached. It is also possible that not all Slip rings of the slip ring body with the sliding layer are provided.

As is usual for the person skilled in the art, the slip ring body is here designates the arrangement that consists of the hub, the Insulator (preferably the insulating sleeve in the form of a Cylinder jacket) and the slip rings, which at the Invention from the metallic slip ring base and Sliding layer are composed.

The thickness of the sliding layer is limited by their conductivity (the thicker that compared to metals poorer conductive sliding layer, the higher it becomes the resistance between that with the metallic slip ring base Conductively connected discharge line and the connecting line on the brush). It has proven to be beneficial proven the thickness of the sliding layer not greater than 11% to make the radius of the outer cladding of the sliding layer.

The metallic slip ring base is usually a flat cylindrical support ring, the massive, with (mostly circular) recesses or designed as a spoked wheel can be. It is also possible and preferred the width the slip ring base near the outer shell in the Region to choose larger than the rest of the ring. The This gives the slip ring base the appearance of a flat one Ring (which may also have recesses), on its circumference in a preferred manner (towards parallel to the axis) wider cylinder jacket like a hoop is executed. On the (outer) surface of this The slip ring base becomes a sliding layer with constant Thickness attached electrically conductive. This attachment will preferably produced by conductive gluing. The advantage of a bond is that the electrical Connection has the largest possible contact area, this lowers the contact resistance and distributes the force between the two materials on the largest possible area. In the case of gluing, this is otherwise not the case with Preparation of a solder joint required heating Temperatures at which the solder melts. When soldering namely, special precautions required to avoid Avoid damage to the slip ring base, such as disassembly or attaching a heat shield.

The sliding layer consists of an electrically conductive Graphite material. Is preferred as material for the Sliding layer a graphite material with a bending strength of at least 30 MPa. Will continue preferably isostatically pressed graphite material used. The thickness of the sliding layer should be in the Compared to the metallic slip ring base higher specific resistance can be kept as low as possible. However, it should be borne in mind that on the one hand the mechanical stability of the sliding layer with less Thickness becomes smaller, and on the other hand the abrasion in Connection with the (usually and preferably from Carbon materials) brushing through the appropriate selection of material and its thickness should be designed that by renewing the sliding layer required maintenance intervals the same or longer than the average bearing life. The thickness of the sliding layer should therefore not more than 11% of the outer radius of the slip ring (i.e. the outer radius of the sliding layer); is preferred the thickness of the sliding layer is 10% or less of this radius, especially 8% or less, with shares of 6% and below or 4% and below are particularly preferred.

For gluing the sliding layer and the metallic slip ring base conductive adhesives are used. This Adhesives should preferably be selected so that their Temperature resistance is so great that even a firm one Gluing the sliding layer on the metallic The slip ring base is secured during operation the slip ring arrangement occurring temperatures at Slip ring. However, adhesives are also preferably used, that do not have a suitable conductivity of their own however, a metal powder, preferably copper powder, is added becomes. After application, the Adhesive layer the coated surfaces with the metal powder sprinkled to an electrically conductive adhesive connection to obtain. The metal powder used have preferably has a grain size of 0.01 mm to 0.2 mm. To the Adhesives used include, in particular, epoxy resin adhesives, Phenolic resin adhesive, cyanate ester resin adhesive and adhesive the basis of polyurethane resins, polyester resins and Amine resins. Are particularly preferred for the invention Slip rings used phenolic resin adhesive. The Layer thickness of the adhesive on the metal surface of the Slip ring base or on the inner surface of the sliding layer is preferably between 0.02 mm and 0.2 mm, particularly preferably between 0.05 mm and 0.1 mm. When gluing the sliding layer segments are on the load-bearing The slip ring base is fitted precisely and under uniform pressure. The Joint width between the individual segments of the Sliding layer should be kept as low as possible.

As a sliding partner to the sliding layer of the slip rings preferably uses graphite brushes, that is, brushes made of Carbon materials with a graphitic character. These include in particular electrographite and burned Carbon materials that contain natural graphite.

Another advantage of this construction is that the sliding layer, which is preferably made of said flex-resistant Carbon material exists, if necessary without problems can be renewed; all that has to be done is the remaining one Sliding layer and the adhesive layer down to the metal be turned off, followed by a new sliding layer can be applied. Changes in brush position at this overhaul is not required here. At a the slip ring must be made of pure metal if worn be revised, with a minimum diameter not may fall short, or the entire slip ring must be replaced, the brushes also renewed Need to become.

The partial or complete retrofitting of existing ones Machines with purely metallic slip rings easy to make such that the metallic Contact layer on the outer surface of the existing Slip rings in the slip ring body is prepared is preferably removed, particularly preferably by Turn off the sliding layer to the required thickness applied and with the remaining metallic slip ring base can be connected by gluing. The sliding layer can, if necessary, to eliminate surface irregularities required, then e.g. by Turning or grinding can be revised. In particular this retrofit shows the advantage of Execution according to the invention, since usually the thickness (in the radial direction) of the running layer of metallic Slip rings are large enough to with no loss of stability to be turned to the required diameter. This applies in particular to metallic slip rings that have two layers in the radial direction, one metallic carrier layer and a separate outer running layer.

It is particularly advantageous to use the metallic slip rings an existing machine in this way (e.g. by Grinding, turning or milling) to prepare that at least one of the edges of the outer surface of the remaining metallic slip ring base each Stand overhang (in the direction of the increasing radius) remains, which is preferably 0.5 mm to 5 mm, in particular 1 mm up to 3 mm wide and 0.5 mm to 3 mm, preferably 1 to 2 mm is high. The sliding layer is in the cylindrical groove, which is created in this way, glued in such a way that the Completes the sliding layer with the supernatants or these preferably by up to 5 mm, in particular up to 3 mm towered over.

In the arrangement according to the invention, the entire Slip ring body for overhauling or renewing the sliding layer be clamped, the slip rings are up to the metallic base is turned off and the sliding layer can (with one or more slip rings at the same time) be replaced.

The sliding layer can consist of a closed ring consist; however, it is preferred to make the sliding layer to put together several segments that consist of one or several graphite rings are cut, whereby they are in at least two, particularly preferably at least three Segments is applied to the carrier. It is favorable, the joint between two adjacent Sliding layer segments not parallel to the axis of rotation (i.e. perpendicular to the tangent), but in one Angle to the tangent of maximum 75 °, preferably maximum 60 °, and particularly preferably up to 45 °. The term "Tangent" is defined as follows and continues like this uses: "A tangent is any straight line that is the outer Touched surface of the slip ring and perpendicular to Rotation axis of the rotating part of the electrical Machine runs. "So it turned out to be particularly advantageous proven if the sliding layer in one piece in the form of a Ring is applied to slit this all around an angle β with respect to the tangent, which preferably so too is dimensioned that the slot at least once over the full extent of the sliding layer runs. Will the Sliding layer applied in more than one segment, that is it is advantageous not to use these segments with the same (Arc) length, but the (arc) length of the longest segment should be at least 110% of the length of the other (or the second longest) segment. The The thickness of the sliding layer is up to 11% of the outer radius of the slip ring, preferably at most 5 mm, in particular 4 mm and less.

Fig. 1

einen schematischen Längsschnitt durch einen Schleifringkörper

Fig. 2

eine Detailvergrößerung gemäß dem Ausschnitt II in Fig. 1

Fig. 3

eine Detailvergrößerung entsprechend dem Ausschnitt von Fig. 2 von einer alternativen Ausführung zu Fig. 1

Fig. 4

einen Querschnitt gemäß der Linie IV - IV in Fig. 1

Fig. 5

eine seitliche Draufsicht auf einen Schleifring-Körper gemäß Fig. 4

Fig. 6

eine Draufsicht auf einen Schleifring-Körper gemäß einer alternativen Ausführungsform zu Fig. 4

Show it :

Fig. 1

a schematic longitudinal section through a slip ring body

Fig. 2

a detailed enlargement according to section II in Fig. 1st

Fig. 3

a detail enlargement according to the section of FIG. 2 of an alternative embodiment to FIG. 1st

Fig. 4

a cross section along the line IV - IV in Fig. 1st

Fig. 5

3 shows a side plan view of a slip ring body according to FIG. 4

Fig. 6

3 shows a plan view of a slip ring body according to an alternative embodiment to FIG. 4

A slip ring body 11 according to the invention with a total three slip rings 10, 10 ', 10' 'in FIG. 1 shown a section through the slip ring body 11 in a plane parallel to the axis of rotation. On a Insulating layer 12, which is applied to a hub 1, are metallic rings 2, 2 ', 2' 'as the slip ring base attached. On the outer surface of these metallic rings 2, 2 ', 2' 'is a sliding layer 3, 3' and 3 '' in Shape of a cylindrical ring glued on with the help of a electrically conductive adhesive. This construction is over 2, which is an enlarged detail 1 is. Here is a metallic part of the slip ring base 2, on which the annular sliding layer 3 through the electrically conductive adhesive 6 is attached.

The above-mentioned preferred embodiment in which the Slip ring base 2 is designed so that on the edges a protrusion 4, 4 'of their outer lateral surface remains standing, can be seen in Fig. 3. This is one modified embodiment compared to that in Fig. 2 or Fig. 1 illustrated embodiment. In contrast to in 1 is here on both Edges of the outer shell of the slip ring base 2 each a protrusion 4 and 4 'remained, which in the Middle of the outer boundary surface of the slip ring base 2 a groove 5 is formed, in which the sliding layer is flush can be introduced. At the bottom of the groove 5 is the electrically conductive adhesive 6 spread, the sliding layer 3 is put on and with the slip ring base 2 glued.

FIG. 4 shows a section along the line IV-IV of FIG. 1. The annular slip ring base 2 ″, to which the sliding layer 3 ″ is glued, is fastened on the insulating layer 12 above the hub 1. The multi-part embodiment of the sliding layer 3 ″ can be seen in this FIG. 4, a three-part embodiment being shown here, with the sliding layer segments 3 ″ ₁ , 3 ″ ₂ and 3 ″ ₃ and the joints 7, 7 'and 7 ".

5 is a top view of such Slip ring shown, with the viewing direction vertical to the axis and perpendicular to the diameter of the slip ring is. The sliding layer 3 is on the slip ring base 2 in glued several segments, here a joint 8 can be seen between two segments of the sliding layer. The Angle α of the joint 8 against the tangent is 60 °.

Finally, FIG. 6 shows a top view like FIG. 5 another preferred embodiment in which the Sliding layer forming ring 3 is slotted. The angle β the slot 9 with respect to the tangent is preferably so chosen that the slot along a spiral line on the The outer surface of the cylindrical sliding layer runs and the Length of the slot is greater than the circumference of the lateral surface is. The advantage of this embodiment is that the ring for application on the slip ring base attached to the hub 1 2 can be expanded, he even if necessary via a device as shown in FIG. 3 existing raised protrusion 4 or 4 'of Slip ring base inserted into groove 5 without risk of breakage can be. The slotted sliding layer 3 is then glued to the slip ring base 2 so that it lies flush and the width of the slot 9 as possible is low. The acute angle β (small angle) of the Slit 9 further minimized with respect to the tangent possible bumps or bumps and thereby reduces the Abrasion.

The invention is illustrated by the following examples explains:

Comparative example

In a standard 6 kV electric motor (type "1LS1 456-4HA60-Z" from Siemens AG, No. 904 068) with slip rings according to State of the art steel X10Cr13 and related optimized brushes, namely metal graphite brushes "RC53" SGL CARBON GmbH was involved in the operation with Nominal load the temperature of the supply air, at the winding, in Slip ring space, on the brushes and on the slip rings certainly. The abrasion on brushes and slip rings was certainly.

example

The slip ring body from the comparative example (with a diameter of 280 mm) was clamped centrally on a lathe and the slip rings made of steel were turned to an outer diameter of 270 mm. On the bare surface resulting from the twisting off, three ring segments were made of an isostatically pressed graphite of the brand 300 from SGL CARBON GmbH with the dimensions: inside diameter 270 mm, outside diameter 282 mm, width 30 mm with the help of a phenolic resin as an adhesive, which was coated with copper powder Type FFL from the company Norddeutsche Affinerie was filled (composition: 50% by weight resin, 50% by weight copper powder), glued on. The joints between the segments were designed with a slope of 60 °. The slip ring body was again clamped centrally and turned to an outer diameter of 280 mm. The slip ring body was reinstalled in the engine. In addition, the brushes were exchanged for graphite brushes of the RE65 brand from SGL CARBON GmbH. The same measurements as in the comparative example were carried out. The results are summarized in the table. comparison example brush RC53 RE65 Sliding layer Steel X10Cr13 Isographite 300 Wear brush 0.3 mm / 100 h <0.05 mm / 100 h Wear ring not measurable not measurable

Extensive comparisons between the two configurations with different operating times and different Last revealed that the temperature of the brushes in the Execution according to the invention on average 13 to 23 ° C. lower than that of the comparison, the temperature of the Slip rings were on average 12 to 18 ° C lower than when comparing. Due to the lower temperature stress in the slip ring arrangement according to the invention can extend the life of the components of the electrical machines such as the camp, increased become.

With a longer runtime (a few hundred hours) was in Comparison a clear removal of the brushes of the determine conventional arrangement (comparison), while the arrangement according to the invention is not measurable Brush wear of the brushes used showed. The wear on the slip rings was this short Runtime not measurable.

Furthermore, tests were carried out with the comparison slip ring arrangement and the slip ring arrangement according to the invention according to the example on test benches in order to test the systems under extreme loads. Here, the slip ring arrangements were mounted on a 710 KW motor and start-up attempts were carried out in the form of ramp-ups with different rotor currents, ie a very large output was demanded from them at short notice. With the comparison slip ring arrangement according to the prior art, these tests could be carried out up to 3.2 times the nominal current, which corresponds to a current density per brush of approx. 32 A / cm ² . In the standard version, however, both the slip rings and the brush running surfaces showed severe damage due to melting (firing of the brushes was observed). The slip ring arrangement according to the example according to the example could even be carried out up to approximately 3.5 times the rated current, which corresponds to a current density of 40 A / cm ² over the slip ring arrangement according to the invention. Even at this even higher load, no damage to the slip rings and brushes (firing the brushes) of the arrangement according to the invention could be observed.

A major advantage of the slip ring arrangement according to the invention is that the slip rings almost without Exchange can be used. Only the sliding layer can be renewed if necessary without however, the metallic slip ring base is noteworthy to attack. In contrast, the previously used metallic slip rings to be renewed over time because every time you maintain the electrical Machines to replace the bearings had to be turned off around the scoring on the slip ring surface compensate.

Reference list

1

hub

2, 2 ', 2' '

metallic slip ring base (ring shape)

3, 3 ', 3' ',

Sliding layer

3 '' ₁ , 3 '' ₂ , 3 '' ₃

Sliding layer

4, 4 '

Got over

5

Groove

6

Glue

7, 7 ', 7' '

Joint

8th

Shock

9

slot

10th

Slip ring

11

Slip ring body

12th

Hub insulation

α

Angle of 8

β

Angle of 9

Claims (17)

Slip ring arrangement for electric motors and generators, in which brushes made of carbon materials and slip rings (10, 10 ', 10'') of the slip ring body (11) are connected to one another in an electrically conductive manner,
characterized in that
the slip rings (10, 10 ', 10 ") comprise metallic slip rings (2, 2' and 2") of a conventional type as a slip ring base and an electrically conductive sliding layer (3, 3 'and 3 ") made of a graphite material, the Thickness is a maximum of 11% of the radius of the slip ring (10, 10 ', 10 ") and the electrically conductive is attached to the circumference of the metallic slip ring base (2, 2' and 2") by gluing. Slip ring arrangement according to claim 1,
characterized in that
the material of the sliding layer (3, 3 'and 3 ") has a bending strength of at least 30 MPa. Slip ring arrangement according to one of claims 1 or 2,
characterized in that
the sliding layer (3, 3 'and 3 ") consists of an isostatically pressed graphite material. Slip ring arrangement according to one of claims 1 to 3,
characterized in that
the sliding layer (3, 3 'and 3'') consists of annular segments. Slip ring arrangement according to claim 4,
characterized in that
Butt joints (7, 7 'and 7'') between the segments of the sliding layer have an angle α of at most 75 ° to the tangent. Slip ring arrangement according to one or more of claims 4 to 5,
characterized in that
the segments have different arc lengths, the length of the longest segment being at least 110% of the length of the second longest segment. Slip ring arrangement according to one or more of claims 1 to 6,
characterized in that
the slip ring base (2, 2 ', 2 ") is designed such that it has a projection (4, 4') on at least one of the edges of its outer lateral surface. Slip ring arrangement according to claim 7,
characterized in that
the at least one projection (4, 4 ') has a width between 0.5 mm and 5 mm and a height between 0.5 mm and 3 mm. Slip ring arrangement according to one or more of claims 1 to 3,
characterized in that
the sliding layer consists of a ring which is slotted all around with an angle β to the tangent. Slip ring arrangement according to claim 9,
characterized in that
the angle β is such that the slot runs at least once over the full circumference of the sliding layer. Slip ring arrangement according to one or more of claims 1 to 10,
characterized in that
the gluing of the sliding layer (3, 3 'and 3'') and the metallic slip ring base (2, 2' and 2 ") is carried out with a temperature-resistant adhesive which firmly bonds the sliding layer (3, 3 'and 3'') to the Slip ring base (2, 2 'and 2'') also possible when the slip ring arrangement is in operation. Slip ring arrangement according to one or more of claims 1 to 11,
characterized in that
the gluing layer (3, 3 'and 3 ") and the metallic slip ring base (2, 2' and 2") are bonded with an adhesive to which a metal powder has been added. Slip ring arrangement according to one or more of claims 1 to 12,
characterized in that
graphite brushes can be used as brushes. Slip ring arrangement according to one or more of claims 1 to 13,
characterized in that
not all slip rings (10, 10 ', 10'') of the slip ring body (11) have a sliding layer made of a graphite material. Slip ring body (11) according to the slip ring arrangement of claims 1 to 14. Process for converting slip ring bodies in electrical machines with metallic slip rings,
characterized in that
the metallic contact layer on the outer lateral surface of at least one of the existing metallic slip rings is removed in accordance with the thickness of the sliding layer to be applied and that a sliding layer (3, 3 ', 3'') is then applied in accordance with one or more of claims 1 to 12. Method for converting slip ring bodies in electrical machines with metallic slip rings according to claim 16,
characterized in that
the metallic contact layer is removed from at least one of the metallic slip rings in such a way that a protrusion (4, 4 '), preferably according to patent claim 8, is retained at least on one edge of the outer circumferential surface of the remaining metallic slip ring base (2, 2' and 2 ") and that a sliding layer (3, 3 ', 3'') according to one or more of claims 1 to 12 is applied.

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