Cable bushing

Abstract

The invention relates to a pump assembly comprising a pump (1) which is driven by a wet-rotor motor (2). The wet-rotor motor (2) is surrounded by a motor casing (3), the motor casing (3) comprising a bushing arrangement (4) for supplying power to the wet-rotor motor (2). The bushing arrangement (4) has openings (6) in a portion (5) of the motor casing (3), a cable bushing (7) being arranged in each of the openings in a manner secured with the aid of a retaining element (8). The cable bushing (7) has a guide body (9) and an insulating body (10). The insulating body (10) has at least partially conical surfaces which cooperate with the guide body (9).

Description

[0001] Cable feedthrough

[0002] The invention relates to a pump unit with a pump which is driven by a wet-running motor, wherein the wet-running motor is surrounded by a motor housing, wherein the motor housing comprises a feedthrough arrangement for supplying power to the wet-running motor and the feedthrough arrangement has openings on a part of the motor housing, in each of which a cable feedthrough is arranged in a fixing manner by means of a holding element, wherein the cable feedthrough has a guide body and an insulating body.

[0003] Such a pump unit can be used, for example, in power plant construction. The housing components form the pressure shell, which separates an interior space from the surrounding atmosphere. The pressure shell is usually designed for very high system pressure.

[0004] EP 1 910 685 B1 describes an exemplary device. The device comprises a pump driven by a fluid-filled motor. The motor has a housing that is part of the pressure envelope.

[0005] Circulation pumps without a shaft seal are also known as glandless circulation pumps and are often vertical pumps driven by wet-running motors with or without a can. A wet-running motor is usually an asynchronous squirrel-cage motor whose rotor and bearings are immersed in the fluid. Wet-running motors require special attention during design, installation, and commissioning to ensure that their interior motor chambers are reliably filled and vented, and that solids in the fluid are kept away from the fluid-lubricated plain bearings.

[0006] The pump and electric motor are housed in a shared, pressure-resistant housing with a thermal barrier between the pump and motor sections. The thermal barrier can be designed as an active or passive component and allows fluid temperatures of up to 420 °C. The bearings are lubricated by the fluid, and no dynamic seal is required.

[0007] The wet-rotor motor is completely immersed in fluid. Along with the rotor and its bearings, the stator and the winding, including the supply connections, are immersed in fluid. This requires waterproof and pressure-tight insulation of all live parts. The wet-rotor motor is used as a drive motor for glandless circulation pumps in conventional power plants.

[0008] In conventional bushing arrangements for the power supply of wet-rotor motors, the insulation can be constructed in two parts. It consists of an inner insulating body and an outer insulating body.

[0009] From US 3,043,903 A a feedthrough arrangement is known which has a single insulating body enclosing a current conductor.

[0010] JP S55 15968 U describes an insulating element attached to a cable, which is guided through a cable feedthrough opening of an electrical device main body. A flange-like projection is formed in a portion of the insulating element, which bears against a shoulder formed in the device main body and is secured by means of a fastening sleeve. In known feedthrough arrangements, the inner insulating body forms the pressure-bearing part. An outer insulating body is arranged over the inner insulating body. In conjunction, both insulating bodies require a very long overlap to achieve the necessary creepage distances. This increases the installation space. For high loads, metal rings are used for protection. These require additional sealing points and can heat up due to eddy currents.

[0011] DE 10 2014 209 517 A1 discloses a device with a pump driven by a wet-running motor. The device has a housing that includes a feedthrough arrangement for supplying power to the wet-running motor. The feedthrough arrangement has a conducting element and an insulating body. The feedthrough arrangement includes a power transmission element.

[0012] The weak points of a cable bushing for a wet rotor motor, which is particularly subject to high fluid pressure, are the sealing against the ambient pressure and the protection against breakthrough in the event of an accident.

[0013] The object of the invention is to provide a pump unit with a pump and a cable entry with a very compact design. Furthermore, the cable entry should ensure a high degree of safety and take up as little space as possible. At the same time, as few sealing points as possible should be required.

[0014] This object is achieved according to the invention by a pump unit with a pump according to the features of claim 1. Preferred variants can be found in the independent main claims, the subclaims, the description and the drawings.

[0015] According to the invention, the insulating body has at least partially conical surfaces that interact with the conductive body. A cone is a geometric body created by connecting all points of a bounded, continuous surface lying in a plane with a point outside the plane in a straight line. In the special case of a circular surface, the body is also called a circular cone. If the axis is perpendicular to the base plane, the cone is right.

[0016] Ideally, the conical surfaces of the insulating body are formed as partial surfaces of a right circular cone.

[0017] Preferably, the guide body has at least partially conical surfaces. In a particularly advantageous variant of the invention, the conical surfaces of the guide body are formed as partial surfaces of a right circular cone.

[0018] Advantageously, the conical surfaces of the conductive body interact with the conical surfaces of the insulating body. In a particularly advantageous variant of the invention, the conical surfaces of the conductive body and the conical surfaces of the insulating body are formed as a corresponding pair of active surfaces.

[0019] The conducting body preferably comprises a rod-shaped part and a part in the shape of a double cone. The conducting body is preferably designed as an elongated, largely cylindrical rod, at the end of which the connection to the connecting wire of the stator winding is arranged. Advantageously, a thickened portion in the shape of a double cone is formed at the end of the conducting body and in front of the connection to the connecting wire, forming the conical surfaces of the conducting body.

[0020] Ideally, the insulating body is shrunk onto the conductive body. The shrink fit extends largely over the length of the rod-shaped part of the conductive body and ends at the transition to the double cone. The conical surfaces of the insulating body and the conical surfaces of the conductive body form a particularly stable end piece of the shrink fit. Ideally, the insulating body is subjected to significantly less mechanical stress by shrinking onto the double cone, thus extending its service life.

[0021] In addition, shrinking the insulating body onto the conductive body offers advantageous protection against twisting, especially compared to previously glued connections.

[0022] Ideally, the conical surfaces of the insulating body interact with the conical surfaces of the conducting body. This interaction is initiated by shrinking the insulating body onto the conducting body. Additionally, a sealing O-ring is embedded in the conducting body at the junction of the conical surfaces, providing redundant protection against fluid leakage should the conical surfaces of the insulating body and the conical surfaces of the conducting body become damaged.

[0023] Advantageously, a thickened portion in the shape of a double cone is formed at the end of the conductor body and in front of the connection to the connecting wire, forming the conical surfaces of the conductor body. This double cone provides advantageous protection against penetration or breakdown of the cable bushing.

[0024] In a particularly advantageous variant of the invention, the insulating body is made of a high-performance plastic. High-performance plastics are a subgroup of thermoplastics that differ advantageously from engineering plastics and standard plastics, particularly in their temperature resistance, but also in terms of chemical resistance and mechanical properties.

[0025] In a particularly advantageous variant of the invention, the insulating body is made of polyetheretherketone (PEEK).

[0026] Polyetheretherketone is a high-temperature-resistant thermoplastic and belongs to the polyaryletherketone group of materials. Its melting temperature is 335 °C. PEEK is resistant to almost all organic and inorganic chemicals, high-energy electromagnetic waves such as gamma rays and X-rays, and even hydrolysis up to approximately 280 °C. PEEK is primarily used as an insulation material in high-voltage technology due to its good electrical insulation resistance and low dielectric loss factor.

[0027] The insulating body preferably has an elongated shape with an internal cylindrical cavity. The conductive body is inserted into the cavity, and the insulating body is shrunk onto the conductive body. A thickened portion is preferably arranged in the central part of the insulating body, which serves as the seat for the cable feedthrough for the housing opening. For this purpose, the thickened portion has a first recess toward the housing opening for the insertion of an O-ring, which performs the task of sealing the cable feedthrough in the housing opening.

[0028] In addition, the thickened portion of the insulating body has a further recess in the center of the thickened portion, into which another O-ring can be inserted for sealing. This second O-ring is advantageously provided as a redundant seal for the cable feedthrough in the housing opening. In the event of an accident, where very high pressure is combined with elevated temperature, a second O-ring can maintain the sealing effect after the first O-ring loses its sealing effect. For this purpose, the second O-ring is positioned in such a way that there is initially no direct contact with a hot liquid and, in the event of damage to the first O-ring, no massive contact with it.

[0029] Furthermore, the thickened portion on the side facing away from the O-ring has a seat for a ring that acts as a breakthrough protection device. This ring can ideally be designed as a metal ring, whereby the metallic material, for example brass or iron, is non-magnetic. High-temperature-resistant plastics are also suitable. In the event of a breakthrough, i.e. the insulating body breaks and the guide body is forced out of the cable duct, the breakthrough protection ring in combination with the double-conical part of the guide body prevents an actual breakthrough or puncture and advantageously seals off the fluid pressure in the wet rotor motor. This design secures the guide body against projectile-like escape from the housing and prevents massive leakage along the guide body.

[0030] In a favorable variant of the invention, the insulating body has a metallization.

[0031] For this purpose, the metallization is preferably implemented in the form of a substituted nickel layer, which achieves reproducible conductivity through a defined layer thickness. The nickel layer is preferably applied to the inner hollow cylinder of the insulating body. This represents a significant improvement in terms of reproducible conductivity, especially compared to conventional, manually applied conductive inks.

[0032] The combination of shrink-fitting the insulating body and metallizing the inside of the insulating body achieves a play- and air-free contact between the conductive body and the insulating body. This effectively prevents or significantly reduces partial discharge due to the design of the cable feedthrough.

[0033] In comparison to known cable bushings, the cable bushing according to the invention requires neither a sealing tape nor a conductive varnish, nor any adhesive, whereby an extremely robust connection between the conductive body and the insulating body can be achieved, which also has improved field control characteristics.

[0034] Ideally, the cable bushing features a field control lacquer or a field control element. In a favorable variant of the invention, the cable bushing features a field control element, which significantly reduces the maximum field strengths while simultaneously increasing the partial discharge inception voltage. Field control encompasses all measures designed to reduce local electric field strengths to such an extent that the electrical strengths of the insulating materials and interfaces are never exceeded.

[0035] For example, the field control varnish or the field control element has a significantly increased dielectric constant compared to the insulating body, which allows a targeted reduction of the original field strength to be achieved.

[0036] In a favorable variant of the invention, the cable bushing has an additional, outer insulating body. Preferably, the additional, outer insulating body is positioned over the shrink-fitted insulating body and within the non-magnetic threaded bushing that secures the cable bushing in the housing opening. Additionally, the outer insulating body can be adjusted at the upper end with a fixing element. The threaded bushing is preferably designed as an M64 external thread.

[0037] Preferably, the conductive body has a connection to a connecting wire of the stator winding of the wet-rotor motor. In a favorable variant of the invention, the connection is designed as a press connection.

[0038] A press fit is a connection between two parts that utilizes the friction between them. Press fit joints are a type of force-locking joining technique and are standardized by DIN 8593.

[0039] Preferably, the conductive body has a connection to a plastic-insulated connecting wire of the stator winding of the wet-rotor motor. In a favorable variant of the invention, the connection is designed as a press connection.

[0040] In an advantageous variant of the invention, the conductive body has an extension formed as a hollow cylinder. Ideally, the stator winding has at least one wire end inserted into the hollow cylinder. The wire end of the plastic-insulated connecting wire is insulated with PE insulation up to the section inserted into the hollow cylinder.

[0041] Advantageously, the hollow cylinder of the conductive body and the wire end of the connecting wire of the stator winding have a force-locking connection.

[0042] In a particularly advantageous variant, the connection, especially the press connection, is designed as a crimp connection.

[0043] Crimping is a joining process in which two components are joined by plastic deformation, for example, by flanging, squeezing, crimping, or folding. A crimped connection is only partially removable and can only be repaired with suitable tools.

[0044] When crimped correctly, a gas-tight connection is created. By deforming the crimp sleeve into the shape of the hollow cylindrical extension of the conductor and the connecting wire, a structure is created that is largely sealed off from oxygen and thus largely protected from corrosion on the inside.

[0045] Ideally, the connecting wire and the extension of the conductive body are made of the same material, preferably copper. Copper is a virtually ideal conductor, especially for use in wet-running motors. The copper-based crimp connection achieves excellent and virtually lossless conductivity.

[0046] Advantageously, the hollow cylindrical extension of the conductive body is a perfectly integrated connecting bolt, formed in one piece with the conductive body. This eliminates the need for an additional component, saving additional assembly effort and avoiding line losses due to the use of an additional component. The crimp connection between the connecting wire and the conductive body is advantageously implemented directly. Preferably, the cylindrical connecting or winding wire in the form of the connecting wire is inserted directly into the cylindrical cavity of the extension below the double cone of the conductive body and is connected in a friction-locking, ideally conductive manner.

[0047] Unlike conventional cable bushings for wet-running motors, no hard soldering is required. This prevents excessive heat input into the connection, preventing stress on the conductive connection and aging of the insulation. Furthermore, solder, which is not always ideally conductive, is no longer required.

[0048] In an advantageous variant of the invention, the connection at least partially comprises at least four, preferably at least six, outer surfaces, with two outer surfaces arranged opposite each other. The crimp connection preferably deforms the cylindrical extension of the conductive body into a hexagonal body, whereby the inserted cylindrical connecting wire is fixed in the extension of the conductive body with a force fit.

[0049] In a favorable variant of the invention, the feedthrough arrangement comprises three cable feedthroughs. In an alternative variant, six cable feedthroughs can also be implemented in one feedthrough arrangement.

[0050] According to the invention, a pump unit with a pump driven by a wet-running motor, wherein a feedthrough arrangement for supplying power to the wet-running motor comprises at least one cable feedthrough having a conducting body and an insulating body, is produced in a method in which the insulating body is shrunk onto the conducting body.

[0051] According to the invention, a pump unit with a pump is used in a power plant circuit with high system pressure to seal the power supply of the wet-running motor against high system pressure using line bushings. Further features and advantages of the invention will become apparent from the description of exemplary embodiments with reference to the drawings and from the drawings themselves.

[0052] It shows:

[0053] Fig. 1 a sectional view of a motor-pump unit,

[0054] Fig. 2 is a perspective view of a feedthrough arrangement,

[0055] Fig. 3 a sectional view of the feedthrough arrangement,

[0056] Fig. 4 a sectional view of the cable feedthrough.

[0057] Fig. 1 shows a motor-pump unit with a wet-running motor 2. A motor housing 3 forms part of the pressure shell. The interior of the wet-running motor 2 is filled with fluid and has a thermal barrier 25. A cooling system 17 is provided to dissipate the electrical power loss. The wet-running motor 2 comprises two radial bearings 13, 14 and one axial bearing 40.

[0058] The drive force of the wet-rotor motor 2 acts on a shaft train 18 and thus transmits torque to a pump 1. The pump 1 comprises a pump housing 19 in which an impeller 20 and a guide device 21 are arranged. The pump housing 19 is connected to the motor housing 3 via at least four tie rods 22.

[0059] The motor housing 3 and the pump housing 19 together form the pressure shell. This is designed for high system pressure.

[0060] The wet-running motor 2 shown in the exemplary embodiment is completely filled with liquid. Along with the rotor 23 and its bearings, the stator winding 24 and the stator winding overhang 16, including the supply cable connections, are also immersed in the liquid. A bushing arrangement 4 is provided in the motor housing 3 to supply power to the wet-running motor 2. For this purpose, the plastic-insulated copper wires 27, which in this embodiment have PE insulation, are connected from the multilayer coils of the stator winding 24 to the cable bushings 7 using a connection 15.

[0061] The feedthrough arrangement 4 comprises a part 5, which is formed by a collar-shaped elevation. The part 5 is formed integrally with the motor housing 3, which allows it to withstand even high fluid pressures. The part 5 of the motor housing 3 has openings 6, in each of which a line feedthrough 7 is arranged. The number of openings 6 corresponds to the number of line feedthroughs 7 required to operate the wet-rotor motor 2. Each of the openings 6, as can be seen from Fig. 4, has a section 43 with a reduced inner diameter and a section 42 with an enlarged inner diameter.

[0062] A terminal box 28 is arranged on the bushing assembly 4, into which the cable bushings 7 lead. A support 29 is positioned in each terminal box 28 for the mechanical decoupling of the so-called conductive expansion band 30. In this embodiment, the supports 29 are designed as epoxy resin insulators.

[0063] Fig. 2 shows a perspective view of a bushing arrangement 4 with three cable bushings 7. In conjunction with Fig. 3, it can be seen that the cable bushings 7 are arranged in the openings 6 of part 5 of the motor housing 3, each fixedly arranged by means of a retaining element 8. An outer insulating body 26 covers the retaining element 8. For this purpose, the outer insulating body 26 is placed on an inner insulating body 10 and is fixed at the top with a washer 32 and a nut 31.

[0064] The holding element 8 is designed as a non-magnetic threaded bushing, for example with an M64 external thread. In the illustrated embodiment, the terminal box 28 sits directly on the collar-shaped elevation of part 5 of the motor housing 3. The three cable bushings 7 open into the terminal box 28 and each have a connection to the conductive expansion band 30, which in turn is each connected to a support 29 for mechanical decoupling. Fig. 4 shows a detailed sectional view of the cable bushing 7. The cable bushing 7 comprises a guide body 9, which has a rod-shaped part 11 and a double cone 12. The double cone 12 realizes the conical surfaces of the guide body 9, which are designed as partial surfaces of a right circular cone.The conducting body 9 is largely designed as an elongated, cylindrical rod, at the end of which, at reference numeral 44, a connection (not shown) to the plastic-insulated copper wire 27 of the stator winding 24 is arranged. The conical surfaces of the conducting body 9 interact with the conical surfaces of the insulating body 10 and form a mutually corresponding pair of active surfaces 41.

[0065] The insulating body 10 is made of polyetheretherketone (PEEK) and is shrunk onto the conductive body 9. The shrink-fit connection extends at least half the length of the rod-shaped part 11 of the conductive body 9 and terminates at the transition to the double cone 12. By shrinking onto the double cone 12, the composite of insulating body 10 and conductive body 9 is subjected to significantly less mechanical stress and thus also has a longer service life in operation.

[0066] The insulating body 10 has a metallization in the form of a substituted nickel layer, which is applied to the inner hollow cylinder of the insulating body 10. This achieves reproducible conductivity through a defined layer thickness.

[0067] The cable bushing 7 has a further, outer insulating body 26 and is positioned over the shrunk-on insulating body 10 and within the non-magnetic threaded bushing 8, which fixes the cable bushing 7 in the opening 6 of the housing 3. The outer insulating body 26 is adjusted at the upper end with a washer 32 and a nut 31. The threaded bushing 8 is designed with an external thread. The spacer sleeve 46 is made of PEEK and positions the field control element 45.

[0068] In the central part of the insulating body 10, a thickened portion 33 is arranged, which serves as the seat for the cable feedthrough 7 within the opening 6 of the housing 3. For this purpose, the thickened portion 33 has a first recess or chamfer 34 in the region of the section 42 of the opening 6 of the housing 3 for the implementation of a first O-ring 35, which performs the task of sealing the cable feedthrough 7 in the opening 6 of the housing 3.

[0069] In addition, the thickened portion 33 of the insulating body 10 has a second recess 36 in the form of a radially circumferential groove in the center of the thickened portion 33, into which a second O-ring 37 can be implemented for sealing. This second O-ring 37 is advantageously provided as a redundant seal for the cable feedthrough 7 in the opening 6 of the housing 3. In an unfavorable accident scenario, in which very high pressure is accompanied by an elevated temperature, the second O-ring 37 can maintain the sealing effect after the loss of the sealing effect of the first O-ring 35.

[0070] The thickened portion 33 has a seat on the side facing away from the first O-ring 35 for a ring 38 designed as a break-through protection. This ring 38 is designed as a metal ring. The metal ring is preferably made of brass or non-magnetic iron. In the event of a so-called break-through, i.e., the insulating body 10 breaks and the conductive body 9 is pushed out of the cable bushing 7, the break-through protection ring 38, in combination with the double cone 12 of the conductive body 9, prevents any escape from the insulating body 10.

[0071] In addition, a sealing third O-ring 39 is embedded in the guide body 9 at the transition between the conical surfaces of the insulating body 10 and the guide body 9, so that there is a redundant protection against fluid leakage should the conical surfaces of the insulating body 10 on the conical surfaces of the guide body 9 suffer damage to the connection.

Claims

Patent claims 1. Pump unit with a pump (1) which is driven by a wet-running motor (2), the wet-running motor (2) being surrounded by a motor housing (3), the motor housing (3) comprising a feedthrough arrangement (4) for supplying power to the wet-running motor (2), and the feedthrough arrangement (4) having openings (6) on a part (5) of the motor housing (3), in each of which a line feedthrough (7) is arranged in a fixing manner by means of a holding element (8), the line feedthrough (7) each having a guide body (9) and an insulating body (10), characterized in that the insulating body (10) has at least partially conical surfaces which interact with the guide body (9).

2. Pump unit according to claim 1, characterized in that the guide body (9) has at least partially conical surfaces.

3. Pump unit according to claim 1 or 2, characterized in that the guide body (9) comprises a rod-shaped part (11) and a part in the form of a double cone (12).

4. Pump unit according to one of claims 1 to 3, characterized in that the insulating body (10) is shrunk onto the guide body (9).

5. Pump unit according to one of claims 1 to 4, characterized in that the conical surfaces of the insulating body (10) interact with the conical surfaces of the guide body (9).

6. Pump unit according to one of claims 1 to 5, characterized in that the insulating body (10) is made of a high-performance plastic.

7. Pump unit according to one of claims 1 to 6, characterized in that the insulating body (10) has a metallization.

8. Pump unit according to one of claims 1 to 7, characterized in that the line feedthrough (7) has a field control element (45).

9. Pump unit according to one of claims 1 to 8, characterized in that at least one first seal (35) and one second seal (37) are arranged on the line leadthrough (7).

10. Pump unit according to one of claims 1 to 9, characterized in that the guide body (9) has a connection (15) to a connecting wire (27) of the stator winding (24) of the wet-rotor motor (2), wherein the connection (15) is designed as a press connection.

11. Method for producing a pump unit with a pump (1) which is driven by a wet-running motor (2), wherein a lead-through arrangement (4) for supplying power to the wet-running motor (2) comprises a cable lead-through (7) which has a guide body (9) and an insulating body (10), characterized in that the insulating body (10) is shrunk onto the guide body (9).

12. Use of a pump unit with a pump (1) in a power plant circuit with high system pressure to seal the power supply of the wet rotor motor (2) against high system pressure by means of a line bushing (7).

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