Cable bushing

Abstract

The present invention relates to a pump unit comprising a pump 1 driven by a wet rotor motor 2. The wet rotor motor 2 is enclosed by a motor housing 3, the motor housing 3 comprising a bushing device 4 for supplying power to the wet rotor motor 2. The bushing device 4 has a plurality of openings 6 in a portion 5 of the motor housing 3, and a cable bushing 7 is fixedly positioned within each opening using a retaining element 8. The cable bushing 7 has a conductive portion 9 and an insulating portion 10. The insulating portion 10 has at least a partially conical surface that cooperates with the guide portion 9.

Description

Technical Field

[0001] The present invention relates to a pump unit provided with a pump driven by a wet rotor motor, wherein the wet rotor motor is surrounded by a motor housing, the motor housing is provided with a bushing device for supplying power to the wet rotor motor, the bushing device has a plurality of openings in a part of the motor housing, and a cable bushing is fixedly arranged in each opening by a holding element, and each cable bushing has one conductor part and one insulator part respectively.

Background Art

[0002] Such a pump unit can be used, for example, in the construction of power plants. The housing part forms a pressure cover that separates the internal space from the ambient atmosphere. The pressure cover is usually designed for very high system pressures.

[0003] An exemplary device is described in Patent Document 1. This device includes a pump driven by a motor filled with a fluid. The motor has a housing that is part of the pressure cover.

[0004] A circulation pump without a shaft seal, also known as a circulation pump without a stuffing box, is often a vertical pump driven by a wet-rotor motor with or without a split cage.

[0005] A wet rotor motor is usually an asynchronous cage motor in which its rotor and bearings operate in a transport medium. The wet rotor motor requires special attention during design, assembly, and commissioning to ensure that its interior is filled and vented, and that solids in the transport medium are kept away from the liquid-lubricated sliding bearings.

[0006] The pump and electric motor are housed in a common pressure-resistant housing with a thermal barrier between the pump and motor sections. The thermal barrier can be configured as an active or passive component, allowing for conveying medium temperatures up to 420°C. The bearings are lubricated by the conveying medium, and dynamic seals are not required.

[0007] A wet rotor motor is completely filled with fluid. The stator and windings, along with the rotor and its bearings, are submerged in the fluid, including the supply line connections. Essential requirements include water-resistant and pressure-resistant insulation for all live parts. Wet rotor motors are used as drive motors for circulating pumps in conventional power plants that do not have stuffing boxes.

[0008] In a conventional bushing device for supplying power to a wet rotor motor, the insulation can consist of two parts: an inner insulator and an outer insulator.

[0009] Patent Document 2 discloses a bushing device having a single insulating portion surrounding a conductor.

[0010] Patent Document 3 describes an insulating element attached to a cable and fed through a cable bushing opening in the body of an electrical device. A flange-like projection is formed on part of the insulating element, which abuts against a shoulder formed inside the body of the device and is secured by a fastening sleeve.

[0011] In known bushing devices, the inner insulator forms the pressure-resistant portion. The outer insulator is positioned on top of the inner insulator. Combined, the two insulators require a very long overlap to achieve the required creepage distance. This increases the installation space. Multiple metal rings are used for protection under high loads. These require additional sealing points and can be heated by eddy currents.

[0012] Patent Document 4 discloses a device comprising a pump driven by a wet rotor motor. The device has a housing equipped with a bushing device for supplying power to the wet rotor motor. The bushing device comprises a cable element and an insulating portion. The bushing device comprises a power transmission element. [Prior art documents] [Patent Documents]

[0013] [Patent Document 1] European Patent No. 1910685 [Patent Document 2] U.S. Patent No. 3,043,903 [Patent Document 3] JITZEN No. 55-15968 [Patent Document 4] German Patent Application Publication No. 102014209517 [Overview of the Initiative] [Problems that the invention aims to solve]

[0014] The weaknesses of cable bushings for wet rotor motors, especially under high fluid pressure, are their ability to seal against ambient pressure and their protection against breakage in the event of an accident.

[0015] The object of the present invention is to provide a pump unit with a pump and cable bushing that is extremely compact in design. In addition, the cable bushing should ensure a high level of safety and occupy the smallest possible installation space. The fewest possible sealing points should be required. [Means for solving the problem]

[0016] According to the present invention, this objective is achieved by a pump unit comprising a pump having the features of claim 1. Preferred modifications can be obtained from further independent main claims, dependent claims, the specification and drawings.

[0017] According to the present invention, the insulator part has at least a partially conical surface that interacts with the conductor part.

[0018] A cone is a planar, bounded, continuous surface piece where all points are connected by straight lines to a point outside the plane. In the special case of a circular surface piece, this solid is also called a cone. When the axis is perpendicular to the base, this is a right circular cone.

[0019] Ideally, the conical surface of the insulator part is formed as a partial surface of a right circular cone.

[0020] Preferably, the conductor part has at least a partially conical surface. In one particularly advantageous variant of the present invention, the conical surface of the conductor part is formed as a partial surface of a right circular cone.

[0021] Advantageously, the conical surface of the conductor part interacts with the conical surface of the insulator part. In one particularly advantageous variant of the present invention, the conical surface of the conductor part is formed as a pair of corresponding active surfaces with the conical surface of the insulator part (active surface pair / Wirkflaechenpaar).

[0022] Preferably, the conductor part comprises a rod-shaped part and a part in the form of a double cone. The conductor part is preferably formed as an elongated, mostly cylindrical rod, and at the ends of the rod, connections to the connector lines of the stator winding are arranged. Advantageously, at the ends of the conductor part, before the connection to the connector lines, a thickening in the form of a double cone is formed, and this double cone forms the conical surface of the conductor part.

[0023] Ideally, the insulator part is formed in a way of shrink fit (shrunk fit / aufgeschrumpft) onto the conductor part. Here, the shrinkable composite extends over as much of the full length of the rod-shaped part of the conductor part as possible and terminates at the transition to the double cone. Here, the conical surface of the insulator part and the conical surface of the conductor part form a particularly stable end piece of the shrinkable composite. Ideally, the insulator part is subject to significantly reduced mechanical stress when received by the double cone due to shrink fitting, and thus has better durability during operation.

[0024] In addition, by shrink fitting the insulator part onto the conductor part, particularly advantageous anti-torsion protection is provided, especially compared to previous adhesive bonded connections.

[0025] Ideally, the conical surface of the insulator part interacts with the conical surface of the conductor part. This interaction is initiated by shrink fitting the insulator part onto the conductor part. In addition, at the transition of the conical surface, an O-ring for sealing is embedded in the conductor part, so that even if the conical surface of the insulator part is damaged in the connection on the conical surface of the conductor part, there is redundant protection against fluid leakage.

[0026] Advantageously, the thickened part in the form of a double cone is formed at the end of the conductor part before connection to the connector wire, and the double cone forms the conical surface of the conductor part. This double cone provides advantageous breakage or penetration protection to the cable bushing.

[0027] In one particularly advantageous variant of the invention, the insulator part is formed from a high-performance plastic. High-performance plastics are a subgroup of thermoplastic resins, which are advantageously different from engineering plastics and standard plastics, not only with respect to heat resistance, but also with respect to chemical resistance and mechanical properties.

[0028] In one particularly advantageous variant of the present invention, the insulating portion is formed from polyetheretherketone (PEEK).

[0029] Polyether ether ketones are high-temperature resistant thermoplastic resins belonging to the polyaryl ether ketone group. Their melting point 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 hydrolysis up to approximately 280°C. PEEK is preferably used as an insulating material in high-voltage technology due to its good electrical insulation resistance and low dielectric loss tangent.

[0030] Preferably, the insulator portion has an elongated shape with an internal cylindrical cavity. The conductive portion is inserted into the cavity, and the insulator portion is crimped onto the conductive portion. Preferably, a thickened portion is located in the center of the insulator portion, which is formed as a seat for the cable bushing in the opening of the housing. For this purpose, the thickened portion has a first recess for mounting an O-ring in the direction of the opening of the housing, and the O-ring takes on the role of sealing the cable bushing in the opening of the housing.

[0031] In addition, the thickened portion of the insulator has a further recess in the center of the thickened portion, where an additional O-ring for sealing can be mounted. This second O-ring is advantageously provided as a redundant seal for the cable bushing at the opening of the housing. In an undesirable emergency involving very high pressure and a rise in temperature, the second O-ring can maintain the sealing effect after the sealing effect of the first O-ring is lost. For this purpose, the placement of the second O-ring is designed so that there is no direct contact initially, and in the event of damage to the first O-ring, there is no severe contact with the hot liquid.

[0032] Furthermore, the thickened portion on the side away from the O-ring has a seat for the ring, designed as a fracture protection measure. This ring can ideally be designed as a metal ring, and the metal material may be, for example, brass or iron, and not a magnetic component. In addition, high-temperature resistant plastics are also suitable. In the event of so-called fracture, i.e., when the insulator portion breaks and the conductor portion is pushed out of the cable bushing, the fracture protection ring, in combination with the double-conical portion of the conductor portion, prevents actual fracture or break-through and, advantageously, seals the pressure of the fluid present in the wet rotor motor. This design protects the conductor portion from projection leakage from the housing and prevents large-scale leakage along the conductor portion.

[0033] In one preferred variant of the present invention, the insulating portion has a metal coating.

[0034] For this purpose, the metal coating is preferably in the form of a substituted nickel layer that achieves reproducible conductivity by a specified layer thickness. The nickel layer is preferably deposited on the inner hollow cylinder of the insulator portion. This shows a very significant improvement in reproducible conductivity compared, among other known, manually applied conductive lacquers.

[0035] The combination of the tight fit of the insulator and the metal coating on the inside of the insulator ensures a play-free, airless contact between the conductor and the insulator. This means that partial discharge caused by the cable bushing design is particularly effectively avoided or significantly reduced.

[0036] Compared to known cable bushings, the cable bushing of the present invention requires neither sealing tape, conductive lacquer, nor adhesive, thereby achieving an extremely strong connection between the conductive and insulating parts, which also provides improved electric field control characteristics.

[0037] Ideally, the cable bushing has an electric field control varnish or electric field control element. In one preferred modification of the present invention, the cable bushing has an electric field control element, which significantly reduces the maximum electric field strength and simultaneously increases the partial discharge initiation voltage.

[0038] So-called electric field control includes all means used to reduce the local electric field strength so that the electrical strength of the insulating material and interface does not exceed any point.

[0039] For example, an electric field control lacquer or electric field control element has a significantly higher dielectric constant compared to the insulator, and can achieve the target reduction of the original electric field strength.

[0040] In one preferred variation of the present invention, the cable bushing has an additional outer insulator portion. Preferably, the additional outer insulator portion is positioned within a non-magnetic threaded bushing that secures the cable bushing to the opening of the housing, above the interlocked insulator portion. In addition, the outer insulator portion can be adjusted at its upper end by a fixing element. Preferably, the threaded bushing is designed with an M64 male thread.

[0041] Preferably, the conductive portion has connections to the connector wires of the stator windings of the wet rotor motor. In one preferred modification of the present invention, the connection is formed as a press-fit joint.

[0042] Press-fit joining is a type of joining that utilizes friction between two parts. Press-fit joining belongs to the category of non-positive connections (kraftschluessig Verbindung) used in joining techniques and is standardized according to DIN 8593.

[0043] Preferably, the conductive portion has connections to plastic-insulated connector wires of the stator windings of the wet rotor motor. In one preferred modification of the present invention, the connection is formed as a press-fit joint.

[0044] In one advantageous modification of the present invention, the conductive portion has an extension formed as a hollow cylinder.

[0045] Ideally, the stator winding has at least one wire end inserted into a hollow cylinder. The wire end of the plastic-insulated connector wire is insulated with PE insulation up to the portion inserted into the hollow cylinder.

[0046] Advantageously, the hollow cylinder of the conductive part and the wire ends of the connector wires of the stator winding have non-positive connections.

[0047] In one particularly preferred variant, the connection, in particular the press-fit joint, is designed as a crimp connection.

[0048] Crimping is understood as a joining process in which two parts are joined together by plastic deformation, such as flanging, crushing, curling (Kraeuseln), or folding. Crimped connections are only partially retractable and can only be replaced with the appropriate tools in case of repair.

[0049] When crimping is performed correctly, an airtight connection is formed. By deforming the crimp sleeve and connector wire in the form of a hollow cylindrical extension of the conductive part, a structure is formed that is largely sealed from oxygen and therefore largely protected from internal corrosion.

[0050] Ideally, the connector wires and the extensions of the conductive parts are made of the same material, preferably copper. Copper is an almost ideal conductor, especially for use in wet rotor motors. Copper-based crimp connections provide excellent, virtually lossless conductivity.

[0051] Advantageously, the hollow cylindrical extension of the conductive section is, ideally, an integrated connecting bolt designed integrally with the conductive section. This means that no additional parts are required, thereby saving further assembly effort and preventing cable loss due to the use of separate parts. The crimp connection between the connector wire and the conductive section is, advantageously, achieved directly.

[0052] Preferably, a cylindrical connecting wire or winding in the form of a connector wire is inserted directly into the cylindrical cavity of the extension below the double cone of the conductive part, and is ideally connected in a non-positive conductive manner.

[0053] Compared to known cable bushings for wet rotor motors, rigid soldering is unnecessary. This avoids excessive heat input to the connection, meaning that stress on the conductive connection and deterioration of the insulation over time cannot occur. Furthermore, it eliminates the need for solder, which is not always ideally conductive.

[0054] In one advantageous modification of the present invention, the connection comprises at least four, preferably at least six, outer surfaces, in each case two outer surfaces facing each other. By crimp connection, the cylindrical extension of the conductive portion is preferably deformed into a hexagonal shape, thereby securing the inserted cylindrical connector wire within the extension of the conductive portion in a non-positive manner.

[0055] In one preferred modification of the present invention, the bushing device comprises three cable bushings. In one alternative modification, six cable bushings in a single bushing device can also be realized.

[0056] According to the present invention, a pump unit comprising a pump driven by a wet rotor motor, wherein a bushing device for supplying power to the wet rotor motor comprises at least one cable bushing, and the cable bushing comprises a conductive portion and an insulating portion, is manufactured by a method of crimping the insulating portion onto the conductive portion.

[0057] According to the present invention, in a power plant circuit with high system pressure, a pump unit equipped with a pump is used to seal the power supply of a wet rotor motor against the high system pressure using a cable bushing.

[0058] Further features and advantages of the present invention will become apparent from the description of exemplary embodiments with reference to the drawings, and from the drawings themselves. [Brief explanation of the drawing]

[0059] [Figure 1] This is a cross-sectional view of the motor pump unit. [Figure 2] This is a perspective view of the bushing device. [Figure 3] This is a cross-sectional view of a bushing device. [Figure 4] This is a cross-sectional view of a cable bushing. [Modes for carrying out the invention]

[0060] Figure 1 shows a motor pump unit equipped with a wet rotor motor 2. The motor housing 3 forms part of the pressure cover. The inside of the wet rotor motor 2 is filled with liquid and has a thermal barrier 25. A cooling system 17 is provided to eliminate power loss. The wet rotor motor 2 is equipped with two radial bearings 13, 14 and an axial bearing 40.

[0061] The driving force of the wet rotor motor 2 acts on the shaft train 18 and thus transmits torque to the pump 1. The pump 1 comprises a pump housing 19 in which an impeller 20 and a guide device 21 are housed. The pump housing 19 is connected to the motor housing 3 via at least four tie rods 22.

[0062] The motor housing 3 and the pump housing 19 together form a pressure cover. This is designed for high system pressures.

[0063] In the exemplary embodiment, the wet rotor motor 2 is completely filled with liquid. The stator windings 24 and stator winding head 16, along with the rotor 23 and its bearings, are also submerged in the liquid, including the supply line connections. A bushing device 4 is provided in the motor housing 3 for power supply to the wet rotor motor 2. For this purpose, in this design variant, plastic-insulated copper wire 27 with PE insulation is connected from the multilayer coil of the stator windings 24 to the cable bushing 7 using a connection 15.

[0064] The bushing device 4 includes a portion 5 formed by a collar-shaped protrusion. The portion 5 is integrally formed with the motor housing 3, thereby enabling it to withstand high fluid pressures. The portion 5 of the motor housing 3 has multiple openings 6, each containing a cable bushing 7. The number of openings 6 corresponds to the number of cable bushings 7 required to operate the wet rotor motor 2. Each of the openings 6, as can be seen in Figure 4, has a section 43 with a reduced inner diameter and a section 42 with an increased inner diameter.

[0065] A terminal box 28, through which a cable bushing 7 opens, is positioned on the bushing device 4. Inside the terminal box 28, a support 29 is positioned in each case for mechanical isolation of the so-called conductive expansion connector (leitend Dehnband) 30. In this exemplary embodiment, the support 29 is designed as an epoxy resin insulator.

[0066] Figure 2 is a perspective view of a bushing device 4 equipped with three cable bushings 7. In conjunction with Figure 3, it is clear that the cable bushings 7 are fixedly positioned within the opening 6 of a portion 5 of the motor housing 3 using one retaining element 8 in each case. The outer insulator portion 26 covers the retaining element 8. For this purpose, the outer insulator portion 26 is insert-connected to the inner insulator portion 10 and secured on top by washers 32 and nuts 31.

[0067] The retaining element 8 is designed as a non-magnetic threaded bushing, for example, an M64 male thread. In the exemplary embodiment shown, the terminal box 28 is mounted directly to a collar-shaped protrusion of part 5 of the motor housing 3. Three cable bushings 7 open into the terminal box 28 and each have connections to a conductive expansion connector 30, which in each case is connected to a support 29 for mechanical isolation.

[0068] Figure 4 is a detailed cross-sectional view of the cable bushing 7. The cable bushing 7 comprises a conductive portion 9 having a rod-shaped portion 11 and a double-cone portion 12. The double-cone portion 12 provides a conical surface for the conductive portion 9, which is formed as a partial surface of a right cone. The conductive portion 9 is largely formed as an elongated cylindrical rod, with a connection (not shown) to the end of its reference numeral 44 for the plastic-insulated copper wires 27 of the stator winding 24. The conical surface of the conductive portion 9 interacts with the conical surface of the insulator portion 10 to form a corresponding pair of working surfaces 41.

[0069] The insulator portion 10 is formed from polyetheretherketone (PEEK) and is crimped onto the conductive portion 9. Here, the crimpable composite extends beyond at least half the length of the rod-shaped portion 11 of the conductive portion 9 and terminates at the transition to the double cone portion 12. The crimping onto the double cone portion 12 significantly reduces the mechanical load on the composite of the insulator portion 10 and the conductive portion 9, and therefore improves durability during operation.

[0070] The insulator portion 10 has a metal coating in the form of a substituted nickel layer, which is applied to the inner hollow cylinder of the insulator portion 10. As a result, reproducible conductivity is achieved by a specified layer thickness.

[0071] The cable bushing 7 has an additional outer insulator portion 26, which is positioned within a non-magnetic threaded bushing 8 that secures the cable bushing 7 within the opening 6 of the housing 3, on the interlocked insulator portion 10. The outer insulator portion 26 is adjusted at its upper end by a washer 32 and a nut 31. The threaded bushing 8 is designed with male threads. The spacer sleeve 46 is made of PEEK and positions the electric field control element 45.

[0072] In the central part of the insulator portion 10 is a thickened portion 33 formed to serve as a seat for the cable bushing 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 area of ​​section 42 of the opening 6 of the housing 3 for mounting a first O-ring 35, the O-ring 35 which is responsible for sealing the cable bushing 7 within the opening 6 of the housing 3.

[0073] In addition, the thickened portion 33 of the insulator portion 10 has a second recess 36 in the form of a radially and circumferentially oriented groove in the center of the thickened portion 33, and a second O-ring 37 can be mounted inside therein for sealing. Advantageously, this second O-ring 37 is provided as a redundant seal for the cable bushing 7 within the opening 6 of the housing 3. In undesirable emergencies involving very high pressure and temperature rise, the second O-ring 37 can maintain its sealing effect even after the sealing effect of the first O-ring 35 is lost.

[0074] The thickened portion 33 has a seat on the side away from the first O-ring 35 for a ring 38 designed as a fracture protection means. This ring 38 is designed as a metal ring. The metal ring is preferably formed as a brass ring or a non-magnetic iron ring. In the event of a so-called fracture, i.e., when the insulator portion 10 breaks and the conductor portion 9 is pushed out of the cable bushing 7, the fracture protection ring 38, in combination with the double cone portion 12 of the conductor portion 9, prevents it from coming out of the insulator portion 10.

[0075] In addition, since a third O-ring 39 for sealing is embedded within the conductive part 9 at the transition between the conical surfaces of the insulator part 10 and the conductive part 9, a redundant safety device against fluid leakage exists even if the connection between the conical surface of the insulator part 10 and the conical surface of the conductive part 9 is damaged.

Claims

1. A pump unit comprising a pump (1) driven by a wet rotor motor (2), The wet rotor motor (2) is surrounded by a motor housing (3), The motor housing (3) is equipped with a bushing device (4) for supplying power to the wet rotor motor (2), and the bushing device (4) has a plurality of openings (6) in a part (5) of the motor housing (3), and one cable bushing (7) is fixedly arranged in each of the openings (6) using a retaining element (8). Each cable bushing (7) has a conductive portion (9) and an insulating portion (10). In the pump unit, The pump unit is characterized in that the insulating portion (10) has at least a partially conical surface that interacts with the conductive portion (9).

2. The pump unit according to claim 1, characterized in that the conductive portion (9) has at least a partially conical surface.

3. The pump unit according to claim 1 or 2, characterized in that the conductive portion (9) comprises a rod-shaped portion (11) and a double-cone-shaped portion (12).

4. The pump unit according to any one of claims 1 to 3, characterized in that the insulating portion (10) is crimped onto the conductive portion (9).

5. The pump unit according to any one of claims 1 to 4, characterized in that the conical surface of the insulating portion (10) interacts with the conical surface of the conductive portion (9).

6. The pump unit according to any one of claims 1 to 5, characterized in that the insulating portion (10) is made of high-performance plastic.

7. The pump unit according to any one of claims 1 to 6, characterized in that the insulating portion (10) has a metal coating.

8. The pump unit according to any one of claims 1 to 7, characterized in that the cable bushing (7) has an electric field control element (45).

9. The pump unit according to any one of claims 1 to 8, characterized in that at least one first sealing ring (35) and one second sealing ring (37) are arranged on the cable bushing (7).

10. The pump unit according to any one of claims 1 to 9, characterized in that the conductive portion (9) has a connection (15) to a connector wire (27) of the stator winding (24) of the wet rotor motor (2), and the connection (15) is formed as a press-fit connection.

11. A method for manufacturing a pump unit comprising a pump (1) driven by a wet rotor motor (2), wherein a bushing device (4) for supplying power to the wet rotor motor (2) comprises a cable bushing (7) having a conductive portion (9) and an insulating portion (10), characterized in that the insulating portion (10) is crimped onto the conductive portion (9).

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

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