Abstract:
A motor assembly has electrical connectors between them that are shielded from any metallic debris generated in the motors. The motor assembly includes upper and lower motors, each having an adapter coupled together. Each adapter has a wire passage for each phase of the motor. Wires from the motors join electrical connectors, the electrical connectors being mounted to insulators in the adapter passages. A debris seal locates above the upper electrical connector in each upper adapter passage. Another debris seal locates between the overlapping portions of the two insulators of each adapter passage.

Description:
FIELD OF THE INVENTION 
     This invention relates in general to electrical submersible well pump motors, and in particular to debris seals to protect electrical connectors. 
     BACKGROUND OF THE INVENTION 
     Electrical submersible well pumps are often employed in low pressure oil wells that produce large amounts of water along with the oil. The pump assembly is typically suspended on a string of production tubing within casing. Normally, the pump is located at the upper end of the assembly and connects to an electrical motor assembly at the lower end of the pump. A seal section locates between the motor and the pump for equalizing the pressure of dielectric liquid in the motor with hydrostatic pressure in the well. 
     An electrical connection receptacle is located near the upper end of the motor. A power cable extends from the surface into the well. The power cable has a motor lead on its lower end that releasably connects to the receptacle. In some cases, due to the size of the pump, tandem motors will be used. The upper tandem motor has a base or adapter on its lower end that connects to an adapter on the upper end of the lower tandem motor. Wires from the upper tandem motor lead to electrical connectors in the adapter of the upper tandem motor. These electrical connectors engage electrical connectors on the upper end of the lower motor. The motors are filled with the dielectric liquid or lubricant, and the interiors of the motors are in fluid communication with each other. 
     Submersible motors typically use bronze bushings and bearing sleeves that produce metallic debris from normal wear over time. Metallic debris will sometimes migrate through the dielectric oil and lodge around and inside the open spaces of the electrical connectors. This can cause a phase-to-phase or phase to-to-ground short, thus destroying the motors. Also, it is possible for small amounts of water or moisture to migrate to the electrical connectors, creating a short. 
     SUMMARY OF THE INVENTION 
     The motor assembly of this invention has an electrical connector assembly with an insulator having a passage. An electrical conductor having an insulation layer on its exterior extends extending from the motor into the passage of the insulator. The passage has an inner diameter that is larger than an outer diameter of the insulation layer, defining an annular cavity between the insulation layer and the inner diameter of the passage. An electrical connector is joined to the electrical conductor within the passage. 
     An elastomeric debris seal is positioned around the insulation layer. The debris seal has a final size in which it seals around the insulation layer and blocks entry of debris into the annular cavity. The debris seal is of a material that swells upon contact with a dielectric fluid and has an having an initial size in which it does not seal the annular cavity to enable the dielectric fluid to flow into the annular cavity prior to the debris seal reaching the final size. 
     The operator fills the motor by drawing a vacuum, then introducing dielectric oil. The dielectric oil initially flows past the debris seal to fill the annular cavity surrounding the insulation layer. Then over time, the seal will swell to seal the cavity to prevent the entry of debris. 
     In the embodiment shown, the motor assembly is a tandem motor assembly. The upper tandem motor has a plurality of wires that extend downward to upper electrical connectors in an upper adapter. Similarly, the lower motor has wires that extend upward to lower electrical connectors at the upper end of a lower adapter. An elastomeric debris seal locates in the upper adapter passage that surrounds each wire. The upper adapter debris seal seals around the upper wire in each upper adapter passage to prevent debris from collecting around the upper electrical connector. 
     In the preferred embodiment, each adapter wire passage has an insulator located within it. The insulator in the upper adapter passage has one of the debris seals located above it to prevent entry of debris between the inner diameter of the insulator and the wire. The insulator of the lower adapter electrical connector engages the insulator of the upper adapter in a sliding overlapping engagement. Another debris seal locates in the overlapping walls of the insulators. This debris seal prevents debris from migrating into contact with the electrical connectors of the lower motor. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic elevational view illustrating an electrical submersible pump installation constructed in accordance with this invention. 
     FIG. 2 is an enlarged sectional view of the adapters of the tandem pump motors of FIG.  1 . 
     FIG. 3 is a further enlarged sectional view of one of the insulators of the upper adapter of FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, a well pump assembly in accordance with this invention is shown installed in a well. The well pump assembly includes a pump  11 , which may be made up of one or more pump modules. Pump  11  is secured to the lower end of a string of production tubing  13 . Pump  11  has an intake  15  at its lower end for drawing in well fluid. 
     A seal section  17  connects between pump  11  and an upper motor  19  of a tandem motor assembly. A lower motor  21  is secured to upper motor  19 . Seal section  17  reduces the pressure differential between the pressure of dielectric oil contained in motors  19 ,  21  and the exterior hydrostatic pressure of the well fluid. Upper motor  19  has an upper adapter  23  on its lower end that secures to a lower adapter  25  on the upper end of lower motor  21 . A power cable  26  extends from the surface alongside tubing  13 . Power cable  26  has a motor lead on its lower end that plugs into an electrical receptacle  28  near the upper end of upper motor  19 . 
     Referring to FIG. 2, upper adapter  23  may be secured to upper motor  19  in a variety of ways. In this example, a threaded sleeve  27  secures to internal threads in housing  31  of upper motor  19 . Upper adapter  23  is mounted to sleeve  27  by bolts  29 . Upper adapter  23  has a plurality of wire passages  33  (only one shown). Upper adapter  23  also has at least one communication passage  35  that communicates oil in the interior of upper motor  19  with oil in the interior of lower motor  21 . Upper motor  19  has a shaft  37  that extends through a central bore  39  in upper adapter  23 . Shaft  37  has a splined coupling  41  on its lower end. 
     A plurality of power wires  43  extend downward from the windings (not shown) of upper motor  19 . Only one of the wires  43  is shown in FIG.  2 . Wire  43  extends into an upper insulator  45  that is located at the lower end of each wire passage  33 . Referring to FIG. 3, upper insulator  45  is a tubular member of rigid electrical insulation material. Insulator  45  has a flange  47  that locates in a counterbore formed at the lower end of wire passage  33 . A plate (not shown) is secured by screws to the downward facing surface of upper adapter  23  to hold insulators  45  in wire passages  33 . Insulator  45  has a tubular lower portion  49  that extends downward from flange  47 . 
     Wire  43  has one or more insulation layers  51  surrounding a copper conductor  53 . Conductor  53  is joined by soldering or crimping to an electrical connector  55 . Electrical connector  55  has a threaded upper portion that secures to threads (not shown) within an inner diameter portion  56   a  of upper insulator  45 . Inner diameter portion  56   b  of upper insulator  45  is slightly smaller and closely receives electrical insulation layer  51 . Inner diameter portion  56   c , however, is larger than inner diameter portion  56   b  and provides-an annular clearance or cavity  57  surrounding electrical insulation layer  51 . 
     An upper debris seal  59  is located at the upper end of annular cavity  57  to prevent the migration of any metallic debris into annular cavity  57 . Upper debris seal  59  is preferably an elastomeric  0 -ring. Upper debris seal  59  is preferably of a material that swells when immersed in dielectric oil. While upper seal  59  could locate between inner diameter  56   c  and insulation layer  51 , preferably it locates at the upper end of insulator  47 . In this position, seal  59  seals between insulation layer  51  of wire  43  and the inner diameter of upper adapter wire passage  33 . Although the lower side of upper debris seal  59  is shown contacting the upper end of upper insulator  45 , this is not necessary because in this embodiment, upper debris seal  59  does not seal directly to upper insulator  45 . 
     Referring again to FIG. 2, lower adapter  25  has a wire passage  61  that aligns with each of the upper wire passages  33 . Lower adapter  25  also has a communication passage  62  that joins upper communication passage  35 . An insulated lower wire  63  extends upward from the windings of lower motor  21  through each wire passage  61 . A shaft  65  ends concentrically through lower motor  21  and has an upper end that engages splines  41 . 
     A lower insulator  67  is located at the upper end of each wire passage  61 . Lower insulator  67  is also of a rigid insulation material but differs in configuration from upper insulator  45  in this example. Lower insulator  67  has a tubular upper portion  69  (FIG. 3) that slidingly receives lower portion  49  of upper insulator  45 . A lower electrical connector  71  is secured by threads in a passage in lower insulator  67 . In this example, lower electrical connector  71  is a socket that receives a pin from upper electrical connector  55 . The pin and socket could be reversed, however, with the socket being located above and the pin below. Also, tubular portions  49  and  69  could be reversed with portion  69  locating within portion  49 . 
     A lower debris seal  73  is located in a groove formed on the exterior of upper insulator lower portion  49 . Lower debris seal  73  is also elastomeric and preferably an O-ring. Lower debris seal  73  also is formed of a material that swells when contacted with. dielectric oil. Lower debris seal  73  seals a cavity  74  that is located within lower insulator upper portion  69 , thereby blocking debris from contact with lower electrical connector  71 . 
     Motors  19 ,  21  have a fill port  75 , which is shown in the sidewall of lower adapter  25  in FIG.  2 . Fill port  75  allows an operator to evacuate air from the interiors of motors  19 ,  21  and fill the motors with dielectric oil. Adapters  23 ,  25  are secured to each other in a conventional manner. In this example, upper adapter  23  has a flange  77  that bolts to a similar flange of lower adapter  25  by fasteners  79 . Seals  81  seal the interior of upper adapter  23  to lower adapter  25 . 
     Debris seals  59  and  73  are sized so that in an initial configuration, prior to the introduction of dielectric oil, they will not seal. That is, upper debris seal  59  will not seal to upper wire  43  or to the inner diameter of adapter wire passage  33 . Similarly, lower debris seal  73  will not seal to the inner diameter of lower insulator upper portion  69 . Debris seals  59 ,  73  are initially undersized so as to be able to evacuate and fill annular cavities  57  and  74  with lubricant. 
     Once assembled, the operator connects a vacuum pump to port  75  (FIG. 2) and evacuates substantially all of the air. Air will be evacuated also from annular cavities  57  and  74  because the air can flow past debris seals  59  and  73  while in their non sealing configurations. The operator then introduces dielectric oil into the interiors of motors  19 ,  21 . The oil flows through communication passages  35 ,  62  and around shafts  37 ,  65 . As shown in FIG. 2, oil will fill central bore  39  and flow past debris seal  73  into cavity  74 . Also, oil in the interior of upper motor  19  flows downwardly past upper debris seal  59  into annular cavity  57 . 
     Within a short period after immersion in dielectric fluid, debris seals  59 ,  73  will swell and form seals. Preferably the amount of squeeze after swelling is about  10  percent. Debris seal  59  will seal cavity  57 , and debris seal  73  will seal cavity  74 . During operation, the rotation of shafts  37  and  65  causes turbulence of the dielectric oil surrounding them. Metallic debris from the bushings and bearings may migrate downward around wire  43 , but once reaching upper debris seal  59 , will not be allowed to move any further downward. Debris may also migrate down central passage  39  around upper portion  69  of lower insulator  67 . The debris, however, cannot pass between insulator portions  49 ,  69  because of lower debris seal  73 . Lower debris seal  73  prevents debris from migrating into cavity  74 . 
     In some cases upper motor  19  may be operated alone, without being connected to lower tandem motor  21 . In that case, an end cap with a shorting plate is mounted to upper adapter  23  instead of lower adapter  25 . The shorting plate electrically connects electrically connectors  55  to each other, and the end cap seals them from well fluid. 
     Referring again to FIG. 1, electrical receptacle  28  is not shown in detail, but may also contain a debris seal similar to debris seal  59  (FIG.  2 ). Electrical receptacle  28  has a rigid insulation block (not shown) with a passage for each electrical wire and each electrical connector. A debris seal optionally may be located around each insulated wire within a counterbore formed in each passage of the rigid insulation block. 
     The invention has significant advantages. The debris seals block metallic debris from migrating into contact with the electrical connectors. The debris seal increases the electrical leak path distance from the electrical conductor to the motor housing. The debris seals, nevertheless, allow complete filling of dielectric oil because they form seals only after being immersed in the dielectric oil. 
     While the invention has been shown in only one of its forms, it should be apparent to those skilled in the art that it is not so limited but susceptible to various changes without departing from the scope of the invention.