Modular motor construction

[0002] The present invention relates generally to electric motors, and particularly to a modular stator assembly that facilitates motor construction.

[0003] Currently, electric motors, particularly elongate motors such as those used in electrical submergible pumping systems for pumping petroleum, are constructed with unitary stators. Traditionally, individual stator laminations have been stacked together to the full length of the desired stator, and conductive wires have been wound through corresponding openings formed longitudinally through the stator laminations.

[0004] Depending on the horsepower required of the motor, electric submergible pumping system motors can utilize stator assemblies thirty feet long or more. Preparation of the stator windings requires long, thin polished rods that serve as needles for pulling the insulated, conductor wires through the lengthy assembly of stator laminations during winding of the motor. This conventional process is a comparatively slow and expensive process for manufacturing such motors. Additionally, repair or rebuilding of such motors often requires complete destruction or tear down of the motor with little component repair value due to the unitary stator assembly.

[0005] It would be advantageous to have a modular stator that could be used to construct motors, such as motors utilized in electric submergible pumping systems. Benefits of such a modular construction would include reduced cost and assembly time, reduced repair time and reduced motor component inventory.

[0006] The present invention features a modular stator for use in an electric motor. The stator comprises a plurality of stator sections and a plurality of connectors. The connectors are disposed between sequential stator sections, and the stator sections are selectively coupleable with the plurality of connectors to form stators in a variety of desired lengths.

[0007] According to another aspect of the invention, an electric motor is provided that utilizes a modular stator assembly. The electric motor includes an outer housing having a generally hollow interior. A stator is sized to fit within the hollow interior and is formed from a plurality of stator sections. The stator includes at least a first stator section and a second stator section. The first stator section includes a plurality of first stator section conductors extending therethrough. Similarly, the second stator section includes a plurality of second stator section conductors extending therethrough. A connector region is disposed between the first and second stator sections and permits the first and second stator section conductors to be selectively electrically coupled together.

[0008] According to another aspect of the invention, a method is provided for facilitating the assembly of an electric motor. The method includes assembling individual stator laminations into a plurality of modular stator sections. Each stator section has a plurality of electrical conductors that may selectively be coupled to each other. The method further includes determining a desired motor length for a given application, and electrically coupling an appropriate number of the modular stator sections to construct the desired motor.

[0009] The invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and:

[0010] FIG. 1 is a front view of an electric motor, according to a preferred embodiment of the present invention;

[0011] FIG. 2 is a partial cross-sectional view taken generally along line 2—2 of FIG. 1;

[0012] FIG. 3 is a cross-sectional view similar to that of FIG. 2 but showing modular stator components in an exploded view;

[0013] FIG. 4 is an end view of the stacked stator laminations;

[0014] FIG. 5 is a an end view of the completed stator illustrated in FIG. 2;

[0015] FIG. 6 is an end view of a plurality of conductors mounted in an individual slot of the stator illustrated in FIG. 5;

[0016] FIG. 7 is a cross-sectional view taken generally along line 7—7 of FIG. 5;

[0017] FIG. 8 is an enlarged cross-sectional view taken generally along line 8—8 of FIG. 7;

[0018] FIG. 9 is an end view of a connector disposed between stator sections;

[0019] FIG. 10 is an enlarged view taken generally along line 10—10 of FIG. 9;

[0020] FIG. 11 is a cross-sectional view taken generally along line 11—11 of FIG. 9;

[0021] FIG. 12 is an enlarged view of the upper portion of the illustration in FIG. 11; and

[0022] FIG. 13 is a front elevational view of a submergible pumping system positioned in a wellbore and utilizing an electric motor of the type illustrated in FIG. 1.

[0023] Referring generally to FIG. 1, an electric motor 20 is illustrated according to a preferred embodiment of the present invention. Motor 20 is an exemplary motor, such as an elongate, submergible motor that may be connected in a submergible pumping system of the type deployed in a wellbore to pump production fluids, e.g. petroleum. However, the present invention should not be limited to submergible motors.

[0024] Referring also to FIGS. 2 and 3, electric motor 20 generally includes a stator assembly 22 mounted in an outer housing 24. Additionally, a rotor 26 is mounted to a shaft 28 for rotation about an axis 30 within outer housing 24, as is understood by those of ordinary skill in the art.

[0025] Stator assembly 22 is a modular assembly including a plurality of stator sections 32 that may be selectively coupled to one another at one or more connection regions 34. Stator assembly 22 typically includes at least two stator sections 32 and often several stator sections 32, depending on the desired length of motor 20. The use of modular stator sections 32 allows the construction of stator assemblies of a variety of lengths simply by selecting the appropriate number of individual sections 32 and electrically coupling them together.

[0026] Preferably, each connection region 34 comprises a connector 36 to which adjacent stator sections 32 may be selectively plugged and unplugged. The ability of connectors 36 and adjacent stator sections 32 to be easily connected and disconnected facilitates assembly and disassembly of stator assembly 22 as well as electric motor 20.

[0027] Stator assembly 22 further includes a pair of modular end coils 38. End coils 38 may be selectively coupled and uncoupled from the axially outlying stator sections 32 via the axially outlying connectors 36, as illustrated best in FIG. 2. It should be noted that the end coils 38 also can be coupled and uncoupled from a single stator section. The use of a single modular stator section and modular end coils similarly eliminates winding the conductive wires, thereby simplifying construction and repair of the motor.

[0028] The various stator sections 32 and connectors 36 may be mounted within outer housing 24 by a variety of methods. In the illustrated embodiment, a retainer 40 abuts each axially outlying connector 36 (see FIG. 2). An exemplary retainer 40 comprises a snap ring 42 disposed in a groove 44 formed in the inside surface or wall of outer housing 24.

[0029] As best illustrated in FIG. 3, the preferred stator sections 32 are made from a plurality of metallic laminations 46 that are stacked together, as in conventional stator construction. The laminations 46 have an interior opening 48 into which the rotor 26 and shaft 28 are received when the motor 20 is fully assembled. Additionally, each lamination 46 includes a plurality, e.g. 18, of axial openings 50 that are radially outlying from interior opening 48, as best illustrated in the end view of FIG. 4. As the laminations 46 are stacked together to form a stator section 32, the axial openings 50 are aligned to create longitudinal slots 52 through each stator section 32.

[0030] As illustrated in FIGS. 5 through 8, a plurality of conductors 54 are disposed longitudinally through each stator section 32. Preferably, at least two (and more typically eight conductors 54) are disposed through each longitudinal slot 52 (see FIG. 5). As illustrated best in FIG. 6, the individual conductors 54 are insulated from one another and from laminations 46.

[0031] Because of the unique design of stator sections 32, bare wire conductors, such as copper wires, can be insulated from one another and held in place by an insulator block 56 that may be readily formed from a moldable polymeric material. For example, the individual conductors 54 can be held in proper position and orientation within each longitudinal slot 52 while a moldable polymeric material is injected into each longitudinal slot 52 and allowed to solidify. Exemplary insulating materials include polyetheretherketone (PEEK), kapton, and mylar. Once the moldable material sets, the bare wire conductors 54 are securely held in place within their corresponding longitudinal slots 52.

[0032] Individual stator sections 32 may be coupled together in a variety of ways at the various connection regions 34 disposed between adjacent stator sections 32. However, in the preferred embodiment, each stator section 32 is formed with a plug connection 58 disposed at each of its longitudinal ends, as best illustrated in FIGS. 7 and 8.

[0033] In the embodiment illustrated, each plug connection 58 includes a plurality of protrusions or terminal ends 60 that are electrically coupled to conductors 54. Protrusions 60 may comprise the protruding ends of the wires or conductive elements used to form conductors 54.

[0034] Connectors 36 are constructed for engagement with plug connection ends 58 of adjacent stator sections 32. Connectors 36 may be formed as part of one or more of the adjacent stator sections 32 or as independent connectors. With reference to FIGS. 9-12, a preferred, exemplary embodiment of an independent connector 36 can be described.

[0035] Generally, each connector 36 is circular in shape and includes a central opening 62 that is aligned with the interior openings 48 of stator sections 32. In other words, each connector 36 is generally “donut-shaped,” having a pair of axial side walls 64, an interior wall or surface 66 and an exterior wall or surface 68. Exterior wall 68 has a radius that permits the connector 36 to be slid into outer housing 24 of motor 20 adjacent the interior surface of outer housing 24.

[0036] As illustrated best in FIG. 9 and the enlarged view of FIG. 10, each exemplary connector 36 includes a plurality of plug connectors 70 disposed along each of its axial sidewalls 64. Plug connectors 70 are arranged for engagement with the plug connectors 58 of adjacent stator sections 32. In the illustrated embodiment, each plug connector 70 includes a plurality of recesses 72 arranged and sized to receive protrusions 60 of a corresponding stator section plug connector 58. Thus, adjacent stator sections can be electrically coupled together via an appropriate connector 36 disposed therebetween, as illustrated in FIG. 3.

[0037] In the preferred embodiment, each connector 36 comprises a connector block 74 formed of an insulative material, such as a polymeric material. Exemplary insulation materials include PEEK, kapton, and mylar. Within each connector block 74, a plurality of conductive elements 76 are arranged in a generally axial direction, as best illustrated in FIGS. 11 and 12.

[0038] Conductive elements 76 may be made of copper or other appropriate, conductive materials to form conductive paths from one stator section 32 to another. The conductive elements 76 are arranged to be contacted by protrusions 60 when adjacent stator sections 32 are coupled to a given connector 36. For example, each conductive element may include a central solid body 78 (see FIG. 12) having a socket 80 disposed at each axial end. Sockets 80 are sized to matingly receive protrusions 60 to form a conductive path.

[0039] Preferably, each socket 80 extends to a chamfered opening 82 formed in the axial side wall 64 at each conductive element 76. Chamfered openings 82 facilitate the insertion of protrusions 60 when stator sections 32 and connectors 36 are assembled.

[0040] Furthermore, end coils 38 preferably include ends 84 designed for coupling with a stator section 32. Ends 84 may be in the form of plug ends having a plurality of plug protrusions 86 (see FIG. 2) arranged for insertion into a corresponding plug connector 70 of the axially outlying connector 36 at each end of stator assembly 22. The protrusions 86 form a conductive path with a plurality of corresponding conductive wires 88. Generally, the wires 88 (for each plug connector 70) are wrapped by an insulating material, such as a tape 90. Thus, each cluster of wrapped conductive wires 88 has a pair of plug connectors 84 that may be selectively plugged into the appropriate stator section via, for instance, the plug connectors 70 of each axially outlying connector 36. Connection of the end coils completes the windings of stator assembly 22. A continuous conductive path is formed between each stator section 32 via the intermediate connectors 36 and the end coils 38.

[0041] During assembly, the modular components, e.g. connectors 36, stator sections 32 and end coils 38, can be preassembled and slid into outer housing 24 as a unit. Alternatively, the individual components can be assembled as they are moved into outer housing 24. Furthermore, the number of stator sections 32 and connectors 36 can be selected according to the desired length/horsepower for a given motor, provided the outer housing 24 is of an appropriate length to accommodate the selected number of modular components.

[0042] In the event of repair or servicing, the stator assembly 22 simply can be removed from outer housing 24 and uncoupled as necessary. For example, if a certain stator section 32 requires replacement, the surrounding components can be uncoupled, e.g. unplugged, and a replacement stator section 32 inserted. This modular concept greatly simplifies the assembly, servicing, repair, and stocking of replacement stator components for electric motor 20.

[0043] Referring generally to FIG. 13, an exemplary use of motor 20 is illustrated. In this particular utilization, motor 20 is connected as an integral component in a submergible pumping system 100. Submergible pumping system 100 may comprise a variety of components depending on the particular application or environment in which it is used. However, system 100 typically includes a submergible motor, such as motor 20, that drives a submergible pump 102 having a pump intake 103.

[0044] Additionally, a motor protector 104 is connected between submergible pump 102 and motor 20 to isolate well fluid from internal motor oil within motor 20. A connector 106 is used to connect the submergible pumping system to a deployment system 108, e.g. production tubing, cable or coil tubing. Power is supplied to electric motor 20 by a power cable 109.

[0045] Submergible pumping system 100 is designed for deployment in a well 110 containing desirable production fluids, such as petroleum. In a typical application, a wellbore 112 is drilled and lined with a wellbore casing 114. System 100 is deployed within wellbore 112 to a desired location for pumping of the wellbore fluids.

[0046] Because of the relatively small diameter and space constraints in a wellbore environment, elongate motors, often thirty feet in length or more, are used. The above-described modular approach to motor construction facilitates the assembly, servicing, repair and storage of replacement components for such motors.

[0047] It will be understood that the foregoing description is of a preferred embodiment of this invention, and that the invention is not limited to the specific form shown. For example, a variety of connection regions can be used to couple individual stator sections to one another; a variety of component shapes and sizes may be utilized; different motor styles and types may benefit from the modular construction described above; other components may be combined with the modular stator sections; single modular stator sections can be utilized with modular end coils; various plug configurations and coupling structures can be used to combine components; and the subject motor may be utilized in a variety of systems and environments. These and other modifications may be made in the design and arrangement of the elements without departing from the scope of the invention as expressed in the appended claims.