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 being enclosed by a motor housing 3 and having stator windings 24. The motor housing 3 includes a bushing device 4 for supplying power to the stator windings 24 of the wet rotor motor 2. In a portion 5 of the motor housing 3, the bushing device 4 has a plurality of openings 6, and a cable bushing 7 is fixedly positioned within each of the openings 6 by a retaining element 8. The cable bushing 7 has a conductive element 9 and an insulating element 10. The conductive element 9 and the stator windings 24 have a connection 15, which is formed as a crimped connection.

Description

Technical Field

[0001] The present invention relates to a pump unit provided with a pump driven by a wet rotor motor, the wet rotor motor being surrounded by a motor housing and a stator winding, the motor housing being provided with a bushing device for supplying power to the stator winding of the wet rotor motor, the bushing device having a plurality of openings in a part of the motor housing, and cable bushings being fixedly arranged in respective openings by holding elements, each of the cable bushings having a conductor part and an insulator part.

Background Art

[0002] Such a pump unit is used, for example, in the construction of power plants. The housing part forms a pressure-resistant container that separates the internal space from the surrounding atmosphere. The pressure-resistant container 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 liquid. The motor has a housing that is part of a pressure-resistant container.

[0004] A circulation pump without a shaft seal is called a glandless circulation pump and is often a vertical pump driven by a wet-rotor motor regardless of the presence or absence of a can (cylinder) for separation.

[0005] A wet rotor motor is usually an asynchronous cage-type motor in which its rotor and bearings operate in a transport medium. The wet rotor motor requires special attention in the design, assembly, and commissioning stages to ensure reliable filling and evacuation of internal components and to prevent solid particles in the transport medium from contacting the liquid lubricated bearings.

[0006] The pump and electric motor are housed in a common pressure-resistant housing with a heat barrier between the pump and motor sections. This heat barrier can be configured as either active or passive, and the temperature of the conveyed medium can tolerate up to 420°C. Since the bearings are lubricated by the conveyed medium, dynamic seals are not required.

[0007] A wet rotor motor is completely filled with liquid. In addition to the rotor and its bearings, the stator, windings, and power supply line connections are also immersed in the liquid. Therefore, it is a prerequisite that all electrically conductive components are insulated with waterproof and pressure-resistant properties. Wet rotor motors are used as drive motors for glandless circulation pumps in conventional power plants.

[0008] In conventional bushing devices for supplying power to wet rotor motors, the insulation consists 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 to be attached to a cable inserted into a cable entry opening of an electrical device body. A flange-shaped projection is formed on a part of the insulating element, which abuts against a shoulder formed inside the device body and is fixed by a fastening sleeve.

[0011] In known bushing devices, the inner insulator forms the pressure-resistant section, with the outer insulator positioned above it. A very long overlap is required to combine these two insulators and achieve the necessary creepage distance, which increases the installation space. Multiple metal rings are used for protection under high loads, but 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, and further 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 project] [Problems that the invention aims to solve]

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

[0015] The objective of the present invention is to provide a pump unit with a very compact design, comprising a pump and cable bushing. In addition, the cable bushing must ensure a high level of safety, minimize the installation space, and minimize the number of sealing points. [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 conductor part and the stator winding have a connection, and the connection is formed as a press-fit joint.

[0018] A press-fit joint is a joint between two parts that utilizes the friction between these two parts. A press-fit joint belongs to the non-positive connection (kraftschluessig Verbindung) used in joining techniques and is standardized according to DIN 8593.

[0019] Preferably, each conductor part has a connection to the plastic-insulated conductive wire of the stator winding of the wet rotor motor. In one preferred variant of the present invention, the connection is formed as a press-fit joint.

[0020] In one advantageous variant of the present invention, the conductor part has an extension formed as a hollow cylinder.

[0021] Ideally, the cable wire of the stator winding has at least one wire end inserted into the hollow cylinder. The wire end of the plastic-insulated conductive wire is insulated here up to the part inserted into the hollow cylinder with PE insulation.

[0022] Advantageously, the hollow cylinder of the conductor part and the wire end of the conductive wire of the stator winding have a non-positive connection.

[0023] In one particularly preferred variant, the connection, especially the press-fit joint, is designed as a crimp connection.

[0024] Crimping is understood as a joining process in which two parts are connected together by plastic deformation, for example, by flanging, swaging, crimping (Kraeuseln) or bending. Since a crimp connection is semi-detachable, it can be replaced using appropriate tools in the case of repairs, etc.

[0025] When the crimping is performed correctly, an airtight connection is formed. By deforming the crimping sleeve and the conductive wire in the form of the hollow cylindrical extension of the conductor part, a structure that is mostly sealed from oxygen and thus mostly protected from corrosion inside is formed.

[0026] Ideally, the extension of the conductive wire and the conductor part are made of the same material, preferably copper. Copper is an almost ideal conductor, especially for use in wet rotor motors. The crimp connection based on copper provides excellent conductivity with almost no loss.

[0027] Advantageously, the hollow cylindrical extension of the conductor part is ideally an integrated connection bolt designed integrally with the conductor part. This means that no additional parts are required, saving further assembly labor and preventing cable loss due to the use of another part. The crimp connection between the conductive wire and the conductor part is advantageously realized directly.

[0028] Preferably, the cylindrical connection wire or winding in the form of the conductive wire is directly inserted into the cylindrical cavity of the extension under the double cone of the conductor part and is ideally connected in a non-positive conductive manner.

[0029] Compared with known cable bushings for wet rotor motors, hard soldering is not required. This avoids excessive heat input to the connection, which means that load on the conductive connection and aging deterioration of the insulation cannot occur. Furthermore, solder that is not necessarily ideally conductive can be eliminated.

[0030] In one advantageous variant of the present invention, the connection includes at least partially at least four, preferably at least six outer surfaces, and in each case two outer surfaces are arranged opposite to each other. By the crimp connection, the cylindrical extension of the conductor part is preferably deformed into a hexagonal body, whereby the inserted cylindrical conductive wire is fixed in a non-positive manner within the extension of the conductor part.

[0031] Preferably, the connections and conductors are covered with a shrink-fit tube (Schrumpfschlauch) at least up to the insulating portion.

[0032] In one advantageous modification of the present invention, the insulating portion has at least a partially conical surface that interacts with the conductive portion.

[0033] A cone is a geometric solid formed when all points on a continuous, bounded surface are connected by straight lines to a point outside the plane. In the special case of a circular surface, this solid is also called a cone. When the axis is perpendicular to the base, it is a right circular cone.

[0034] Ideally, the conical surface of the insulating portion is formed as a partial surface of a right-circular cone.

[0035] Preferably, the conducting portion has at least a partially conical surface. In one particularly advantageous modification of the present invention, the conical surface of the conducting portion is formed as a partial surface of a right cone.

[0036] Advantageously, the conical surface of the conductor interacts with the conical surface of the insulator. In one particularly advantageous modification of the present invention, the conical surface of the conductor is formed as an active surface pair (Wirkflaechenpaar) with the conical surface of the insulator.

[0037] Preferably, the conductor portion comprises a rod-shaped portion and a double-cone-shaped portion. Preferably, the conductor portion is formed as an elongated, mostly cylindrical rod, with connections to the conductive wires of the stator windings located at the ends of the rod. Advantageously, a double-cone-shaped thickened portion is formed at the ends of the conductor portion, prior to the connections to the conductive wires, and this double cone forms the conical surface of the conductor portion.

[0038] Ideally, the insulator is formed by a shrunken fit onto the conductor, where the shrinkable composite extends as far as possible along the rod portion of the conductor and terminates at the transition to the double cone. Here, the conical surfaces of the insulator and the conductor form particularly stable end pieces of the shrinkable composite. Ideally, the mechanical stress on the double cone is significantly reduced by the shrunken fit, and therefore the insulator is more durable during operation.

[0039] In addition, by crimping the insulating portion onto the conductor portion, advantageous anti-twist protection is provided, particularly compared to previous adhesive bonding connections.

[0040] Ideally, the conical surface of the insulator interacts with the conical surface of the conductor. This interaction is initiated by interlocking the insulator onto the conductor. In addition, an O-ring for sealing is embedded within the conductor at the transition of the conical surfaces, resulting in redundant protection against fluid leakage even if the connection on the conical surface of the conductor is damaged.

[0041] Advantageously, the double-conical thickened section (large diameter section) is formed at the end of the conductor section, before connection to the conductive wire, and the double cone forms the conical surface of the conductor section. This double cone provides advantageous break or puncture protection to the cable bushing.

[0042] In one particularly advantageous modification of the present invention, the insulating portion 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 in terms of heat resistance but also in terms of chemical resistance and mechanical properties.

[0043] In one particularly advantageous variant of the present invention, the insulating portion is formed from polyetheretherketone (PEEK).

[0044] 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.

[0045] Preferably, the insulator portion has an elongated shape with an internal cylindrical cavity. The conductor portion is inserted into the cavity, and the insulator portion is crimped onto the conductor portion. Preferably, a thickened portion (large diameter 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.

[0046] 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 rising 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.

[0047] Furthermore, the thicker 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 insulating 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.

[0048] In one preferred variant of the present invention, the insulating portion has a metal coating.

[0049] 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.

[0050] 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.

[0051] 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 conductor and the insulator, and also possessing improved electric field control characteristics.

[0052] Ideally, the cable bushing has an electric field control lacquer. In one preferred modification of the present invention, the cable bushing has an electric field control element, which can significantly reduce the maximum electric field strength and simultaneously increase the partial discharge initiation voltage.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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 having a conductor portion and an insulating portion, is manufactured by crimping the insulating portion onto the conductor portion, inserting the wire ends of the stator windings into the hollow cylinder of the conductor portion for each cable bushing, and establishing a positive lock connection using a press tool.

[0058] 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.

[0059] 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]

[0060] [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. [Figure 5] This is a detailed diagram of a cable bushing. [Modes for carrying out the invention]

[0061] 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 heat 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.

[0062] 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.

[0063] The motor housing 3 and the pump housing 19 together form a pressure cover. This is designed for high system pressures.

[0064] The wet rotor motor 2 shown in the exemplary embodiment 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.

[0065] 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 pressure. 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.

[0066] 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.

[0067] Figure 2 is a perspective view of a bushing device 4 with three cable bushings 7. In conjunction with Figure 3, it is clear that the cable bushings are fixedly positioned within the opening 6 of a portion 5 of the motor housing 3 by a 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.

[0068] 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.

[0069] Figure 4 is a detailed cross-sectional view of the cable bushing 7. The cable bushing 7 comprises a conductor 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 conductor portion 9, which is formed as a partial surface of a right cone. The conductor portion 9 is largely formed as an elongated cylindrical rod, with a connection (not shown) to the plastic-insulated copper wire 27 of the stator winding 24 located at its end, reference numeral 44. The conical surface of the conductor portion 9 interacts with the conical surface of the insulator portion 10 to form a corresponding pair of working surfaces 41.

[0070] The insulator portion 10 is formed from polyetheretherketone (PEEK) and is crimped onto the conductor portion 9. Here, the crimpable composite extends beyond at least half the length of the rod-shaped portion 11 of the conductor 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 conductor portion 9, and therefore improves durability during operation.

[0071] 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.

[0072] 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 top of 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.

[0073] In the center of the insulator portion 10 is a thickened portion 33 (large diameter portion) 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 chamfered portion 34 in the area of ​​section 42 of the opening 6 of the housing 3 for mounting a first O-ring 35, and the O-ring 35 is responsible for sealing the cable bushing 7 within the opening 6 of the housing 3.

[0074] In addition, the thickened portion 33 of the insulator 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 it 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.

[0075] The thickened portion 33 has a seat on the side away from the first O-ring 35 for a ring 38 designed as a break 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 break, i.e., when the insulator portion 10 breaks and the conductor portion 9 is pushed out of the cable bushing 7, the break 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.

[0076] In addition, since a third O-ring 39 for sealing is embedded within the conductor portion 9 at the transition between the conical surfaces of the insulator portion 10 and the conductor portion 9, a redundant safety device against liquid leakage exists even if the connection between the conical surface of the insulator portion 10 and the conical surface of the conductor portion 9 is damaged.

[0077] Figure 5 shows a detailed view of the cable bushing 7, in particular the connection 15 designed as a press-fit or crimp connection. The conductor portion 9 has an extension formed as a hollow cylinder 47. The cylindrical ends 18 of the conductive wire 27 are introduced into the hollow cylinder 47 and joined by a press tool to form a non-positive connection 15.

[0078] The conductive wire 27, including the cylindrical wire end 18, and the extension of the conductor section 9 are made of copper. The copper-based crimp connections provide excellent, virtually lossless conductivity.

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) and has stator windings (24). The motor housing (3) is equipped with a bushing device (4) for supplying power to the stator winding (24) of the wet rotor motor (2), the bushing device (4) has a plurality of openings (6) in a part (5) of the motor housing (3), and cable bushings (7) are fixedly positioned in each of the openings (6) by retaining elements (8). In the case where each of the cable bushings (7) has a conductor portion (9) and an insulating portion (10), A pump unit characterized in that the conductor portion (9) and the stator winding (24) have a connection (15), and the connection (15) is formed as a press-fit connection.

2. The pump unit according to claim 1, characterized in that the conductive portion (9) has an extension portion formed as a hollow cylinder (47).

3. The pump unit according to claim 1 or 2, characterized in that the stator winding (24) has at least one wire end (18) inserted into the hollow cylinder (47).

4. The pump unit according to claim 2 or 3, characterized in that the hollow cylinder (47) and the wire end (18) have a non-positive connection (15).

5. The pump unit according to any one of claims 1 to 4, characterized in that the connection (15) has at least four, preferably at least six, outer surfaces, and two of the outer surfaces are arranged facing each other.

6. The pump unit according to any one of claims 1 to 5, characterized in that the insulator portion (10) has at least a partially conical surface that interacts with the conductor portion (9).

7. The pump unit according to any one of claims 1 to 6, characterized in that the conductor portion (9) has at least a partially conical surface.

8. The pump unit according to any one of claims 1 to 7, characterized in that the conductor portion (9) comprises a rod-shaped portion (11) and a double-cone-shaped portion (12).

9. The pump unit according to any one of claims 1 to 8, characterized in that the insulator portion (10) is fitted into the conductor portion (9).

10. The pump unit according to any one of claims 1 to 9, characterized in that the insulating portion (10) is made of high-performance plastic.

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

12. The pump unit according to any one of claims 1 to 11, characterized in that the cable bushing (7) has an electric field control element (45).

13. 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 conductor portion (9) and an insulating portion (10), characterized in that the wire ends (18) of the stator windings (24) are inserted into the hollow cylinders (47) of the conductor portion (9) of each cable bushing (7), and a positive lock connection (15) is established using a press tool.

14. Use of a pump unit equipped with a pump (1) to seal the power supply of the 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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