Abstract:
A modular electric motor for use in a wellbore. The modular motor includes a plurality of modular motor sections. The modular motor sections being mechanically and electrically coupleable. At least one modular motor section having a rotor. The rotor of one modular motor section having a rotor being drivingly coupleable to the rotor of a second modular motor section having a rotor. Thus, a given motor may be assembled to a variety of desired lengths by connecting the appropriate number of modular motor sections.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to electric motors, and particularly to a modular motor that facilitates motor construction.  
         BACKGROUND OF THE INVENTION  
         [0002]    Submersible electric motors are used in submersible pumping systems to lift wellbore fluids from depths of up to several thousand feet. A conventional motor used to provide the equivalent pumping power on the surface cannot be used in a wellbore because the diameter of such a motor would be too wide to fit into the wellbore. Therefore, as compared to short, thick surface motors, the stators of submersible electric motors are relatively thin and extremely elongated.  
           [0003]    Elongating the stator allows the motor to produce the required torque to drive a pump by developing magnetic force over a stator of a much larger length. Thus, if long enough, a motor that produces a relatively smaller torque per foot can produce a sufficient total torque. Depending on the horsepower required of the motor, electric submersible 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 a lengthy assembly of stator laminations. 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.  
           [0004]    It would be advantageous to have a modular motor that could be used to construct motors in the field, such as motors utilized in electric submersible pumping systems. Benefits of such a modular construction would include reduced cost and assembly time, reduced repair time and reduced motor component inventory.  
         SUMMARY OF THE INVENTION  
         [0005]    The present invention features a modular electric motor. The modular electric motor comprises a plurality of motor sections selectively coupleable, mechanically and electrically, to form electric motors in a variety of desired lengths. The modular electric motor features a rotor in each motor section that is drivingly coupleable to at least one other motor section.  
           [0006]    According to another aspect of the invention, a submersible pumping system is featured. The submersible pumping system includes a submersible electric motor and a submersible pump. The submersible electric motor has a plurality of motor sections which are mechanically and electrically coupleable to form a motor of a desired length. Each motor section has a modular stator section and a modular rotor section.  
           [0007]    According to another aspect of the invention, a method is provided for facilitating the assembly of an electric motor. The method features the act of manufacturing a plurality of motor sections having modular stator and rotor components. The method further includes determining a desired motor horsepower for a given application, and connecting the modular components to assemble a motor of the required length and horsepower. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    The invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and:  
         [0009]    [0009]FIG. 1 is a front elevational view of a submersible pumping system that utilizes a submersible electric motor, according to a preferred embodiment of the present invention;  
         [0010]    [0010]FIG. 2 is a cross-sectional view of the submersible electric motor illustrated in FIG. 1;  
         [0011]    [0011]FIG. 3 is an end view of a stator lamination from the motor of FIG. 2;  
         [0012]    [0012]FIG. 4 is an end view of conductors, i.e. windings, extending through radial openings in the stator lamination illustrated in FIG. 3;  
         [0013]    [0013]FIG. 5 is an end view of a portion of a female insulated block and female terminations for the conductive windings;  
         [0014]    [0014]FIG. 6 is an end view of a portion of a male insulated block and male terminations for the conductive windings;  
         [0015]    [0015]FIG. 7 is an end view of a modular motor section having a female end;  
         [0016]    [0016]FIG. 8 is an end view of a modular motor section having a male end;  
         [0017]    [0017]FIG. 9 is a cross-sectional view of two modular motor sections prior to coupling;  
         [0018]    [0018]FIG. 10 is a cross-sectional view of two modular motor sections coupled together;  
         [0019]    [0019]FIG. 11 is an alternative embodiment of an electric motor illustrating a coupling device to couple two middle motor sections; and  
         [0020]    [0020]FIG. 12 is an alternative embodiment of an electric motor featuring two middle motor sections coupled together.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]    Referring generally to FIG. 1, a submersible pumping system  20  is shown that utilizes a modular electric motor  22 , according to a preferred embodiment of the present invention. The submersible pumping system  20  may be comprised of a variety of components depending on the particular application or environment in which it is used. However, submersible pumping system  20  typically includes a submersible motor, such as modular electric motor  22 , to drive a submersible pump  24 . Fluid is drawn into the submersible pump  24  through a pump intake  26 . Typically, a motor protector  28  is connected between submersible pump  24  and electric motor  22  to isolate well fluid from internal motor oil within motor  22 . A connector  30  is used to connect the submersible pumping system to a deployment system  32 , such as production tubing, cable or coil tubing. A multi-conductor cable  34  supplies three-phase alternating current (AC) electrical power from the surface to the motor  22 .  
         [0022]    Submersible pumping system  20  is designed for deployment in a wellbore  36  containing desirable production fluids, such as petroleum. In a typical application, wellbore  36  is drilled and lined with a wellbore casing  38 . Holes  40  in the wellbore casing  38  allow production fluids to enter the wellbore  36 . The submersible pumping system  20  is deployed within wellbore  36  to a desired location for pumping production fluids. Instead of a unitary stator, that may be thirty feet long or more, electric motor  22  utilizes modular motor sections. For example, motor  22  may include a top motor section  42 , a bottom motor section  44 , and two middle motor sections  46 . Electricity flowing through the middle motor sections  46  produces a rotating magnetic field that causes a rotor within each of the middle motor sections to rotate. The rotors within the middle motor sections are coupled together and drivingly coupled through the motor protector  28  and pump intake  26  to the submersible pump  24 .  
         [0023]    Although two middle motor sections  46  are illustrated, the exact number of middle motor sections  46  in a given submersible electric motor  22  can vary depending on the system requirements. During assembly, the modular motor sections are assembled to form electric motor  22 . In the event of repair or servicing, the modular motor sections can be disassembled and uncoupled as necessary. For example, if a particular motor section requires replacement, the surrounding components can be uncoupled, e.g. unplugged, and a replacement motor section inserted. This modular concept greatly simplifies the assembly, servicing, repair, and stocking of replacement components for electric motor  22 .  
         [0024]    Referring generally to FIG. 2, a cross-sectional view is shown of submersible electric motor  22 . Electric power from multi-conductor cable  34  is coupled through an outer housing  47  of stator section  42  to an electrical connector  48  of the stator section  42 . Conductors  50  in cable  34  are coupled to a female connector  52  in top motor section  42 . Conductors  54  in middle motor section  46  are coupled to a male electrical connector  56 . When top motor section  42  is mated to middle motor section  46 , conductors  50  in top motor section  42  are electrically coupled to conductors  54  in the first middle motor section  46 . In this view, for clarity, only two conductors  54  are shown extending through each middle stator section  46 . Typically, there are multiple conductors for each single conductor shown here. Furthermore, as will be more fully discussed in the following paragraphs, there are multiple groups of these multiple conductors oriented around a central axis.  
         [0025]    Conductors  54  of middle motor section  46  extend longitudinally through middle motor section  46  to another female connector  52 . This female connector is designed to engage the male connector  56  of the second middle motor section  46 . Similarly, conductors  54  extend through the second middle motor section  46  to another female connector  52 . Bottom motor section  44  also has a male connector  56 , disposed within an outer housing  57 , and conductors  58  of bottom motor section  44  are coupled to male connector  56 . When bottom motor section  44  is mated to the second middle motor section  46 , conductors  58  of bottom motor section  44  electrically couple each conductor  54  of middle motor section  46  with a corresponding conductor  54  disposed through the middle motor section  46  at a different location.  
         [0026]    In the illustrated embodiment, each middle motor section  46  is formed with male connector  56  at one end and female connector  52  at the other end. This allows a plurality of middle motor sections  46  to be coupled together end-to-end. Additionally, the top motor section  42  is configured with a female connector  52  and the bottom motor section  44  is configured with a male connector  56 . Note that the selection of whether a top or bottom motor section is to be male or female is entirely arbitrary, as long as the selection is consistent so that the modular stator sections can be assembled together.  
         [0027]    When the modular stator sections are joined, the conductors in the top, middle and bottom motor sections are electrically coupled to a source of electrical power on the surface. Electricity flowing through conductors  54  produces a rotating magnetic field that causes a rotor  60  within each of the middle motor sections  46  to rotate. Each rotor  60  is coupled together, and ultimately, to a shaft  62  that rotates pump  24 . Bearings  63  are used to support each rotor  60 . The magnetic field that causes rotation of rotor  60  is prompted by a plurality of metallic laminations  64  that are stacked together and held in place within an outer housing  65  by snap rings  66 , as in conventional stator construction.  
         [0028]    As best illustrated in FIG. 3, each metallic lamination  64  has a central opening  67 . As laminations  64  are stacked to form a middle motor section  46 , central openings  67  form an interior passage or opening  68  that extends through the middle motor section  46  in which rotor  60  is disposed. Laminations  64  also have a plurality of openings  70  that are radially outlying from the central opening  67 . As laminations  64  are stacked, openings  70  are aligned to create longitudinal slots  72 . Typically, multiple conductors  54  are inserted through each of the longitudinal slots  72 . The lamination stacks are disposed within outer housing  65 .  
         [0029]    Motor sections may be drivingly coupled to each other in a variety of ways. In the illustrated embodiment, a typical middle motor section  46  has a protrusion  71  at one end of rotor  60  and a recess  73  at the opposite end of rotor  60 . Protrusion  71  of one rotor  60  is configured to mate with recess  73  of an adjacent rotor  60  so that the two rotors are drivingly coupled together. In the illustrated embodiment, a recess  74  in a coupler  76  of top motor section  42  is configured to mate with protrusion  71  of rotor  60  in an adjacent middle motor section  46 . Additionally, a protrusion  78  of a coupler  80  in bottom motor section  44  is configured to mate with recess  73  in the rotor  60  of an adjacent middle motor section  46 . Coupler  76 , in top motor section  42 , is drivingly coupled to shaft  62 . Ultimately, shaft  62  is drivingly coupled to pump  24 . Shaft  62  and rotor  60  rotate about axis  61 .  
         [0030]    Other methods of drivingly coupling motor sections could include protrusions and recesses configured in a variety of polygonal shapes, including octagonal and hexagonal. Alternatively, a motor section could be configured with a spline for engagement with a respective motor section configured with a spline shaft.  
         [0031]    Modular motor sections may be mechanically coupled together in a variety of ways. In the illustrated embodiment, mechanical coupling is provided by plug connectors  52 ,  56 , and by threaded collar assemblies mounted to the external housings  47 ,  57  and  65 . The modular motor sections  42 ,  44  and  46  are configured with either male threaded end  88  or female threaded collar  90  formed as part of or mounted to the corresponding outer housing  47 ,  57  or  65 . Seal  92 , such as an O-ring, a crush ring, or a metal-to-metal seal, maintains a fluid seal between the inside of motor  22  and the wellbore  36 . A passageway  94  allows motor oil to pass from one modular motor section to another. A passageway  95  allows motor oil to pass from the modular motor to motor protector  28 .  
         [0032]    Referring generally to FIG. 4, a cross-sectional view is shown of a metallic lamination  64  with a plurality of conductors  54  wound through each axial opening  70 . However, as described above, FIGS. 2, 9 and  10  only illustrate one conductor  54  disposed through each axial opening  70  for clarity.  
         [0033]    Referring generally to FIGS. 5 and 6, each group of conductors disposed through the axial opening  70  is terminated in an insulated block in the connectors. Female connector  52  has a female insulated block  98 , while male connector  56  has a male insulated block  100 . The insulated blocks insulate the conductors, e.g. bare copper wires, from one another. The insulated blocks may be readily formed from a moldable polymeric material. Exemplary insulating materials include polyetheretherketone (PEEK), kapton, and mylar.  
         [0034]    In the illustrated embodiment, the plurality of conductive strands, disposed through each axial opening  70 , are terminated in the insulated blocks with a single electrical termination. This reduces the overall number of electrical terminations that must be completed between modular motor modules. However, each conductor could have it&#39;s own individual termination. Conductors that are terminated at female insulated block  98  are terminated with a female termination  102 , while conductors terminated in male insulated block  100  are terminated with a male termination  104 . Male termination  104  is disposed within a raised portion  114  of male insulated block  100 , while female termination  102  is disposed in a recess  116  in female insulated block  98 . When two modular motor sections are abutted, raised portion  114  of male insulated block  100  is inserted into recess  116  in female insulated block  98 . This causes male terminations  104  to be guided and inserted into female terminations  102 .  
         [0035]    Referring generally to FIG. 7, a female end of a middle motor section  46  is illustrated. This view illustrates female threaded collar  90  and recess  73  in rotor  60 . Female connector  52  is surrounded by threaded collar  90 , having internal threads  101 . In FIG. 8, an end view of the male end of a middle motor section  46  is illustrated. Rotor  60  includes protrusion  71 . Male connector  56  is surrounded by threaded end  74 , having external threads  103 . Radial alignment of the two ends is provided by a key  106  and keyway  108 .  
         [0036]    Referring generally to FIGS. 9 and 10, cross-sectional views are shown illustrating the process of joining two middle motor sections  46 . In FIG. 9, the two middle motor sections  46  have not yet been joined. The threaded female collar  90  is moveable along a slot  96  in the outer housing, e.g. housing  65 , of the motor section. Typically, collar  90  includes a ring  105  captured in slot  96  such that collar  90  is retained to the appropriate outer housing.  
         [0037]    Initially, the threaded female collar  90  is pulled away from the end of the modular motor section  46  on which it is mounted. With the ends exposed, the two modular motor sections  46  are axially aligned and brought together. In the illustrated embodiments, the insulated blocks and terminations are aligned with the key  106  and keyway  108  system and the protrusion and recess on the rotors are aligned. Once aligned, the two sections are brought together.  
         [0038]    Coupling is accomplished by forcing the two motor sections together so that the male terminations  88  of one middle motor section  46  are inserted into the female terminations  90  of the next adjacent middle motor section  46 . Additionally, protrusion  71  is inserted into recess  73 . Once joined, threaded collar  90  is tightened over threaded end  88 , as illustrated in FIG. 10. This ensures a secure coupling of the components. Top motor section  42  and bottom stator section  44  may be joined to the appropriate ends of middle stator sections  46  in a similar fashion.  
         [0039]    An alternate embodiment of the present invention is illustrated in FIGS. 11 and 12. Separate coupler  118  is used to couple two middle motor sections  120 , according to an alternative embodiment of the present invention. In this embodiment, a separate coupler  118  may be configured such that middle motor sections  120  are electrically, mechanically, and drivingly coupled through coupler  118 . Alternatively, coupler  118  may be configured such that middle motor sections  120  are mechanically coupled through coupler  118 , but drivingly coupled directly to each other.  
         [0040]    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, more or less than two middle motor sections  46  could be coupled together to form a motor of a desired length. Furthermore, a variety of different methods and configurations can be can be used to electrically and mechanically couple the modular motor sections together. Indeed, various plug configurations and coupling structures can be used to combine components. Furthermore, different motor styles and types may benefit from the modular construction described above. The subject motor may also 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.