Patent Application
20090058221
Submersible motors are used in a wide variety of well related applications. For example, submersible motors are utilized in electric submersible pumping systems employed to produce fluids, such as hydrocarbon based fluids. The electric submersible pumping systems also can be used to deliver fluid downhole or to transfer fluid to other locations. The submersible motor generally is a long cylindrical motor sized to fit within a wellbore and designed to drive a centrifugal pump.
Because submersible motors operate in a submerged environment, conventional submersible motor stators have been insulated with a varnish material. However, with recent modifications made to the magnet wire, and impregnating the stator and windings with varnish is a relatively expensive procedure. Additionally, the varnish can degrade over time and cause a variety of problems, including contamination of the motor oil and cause bearing failures. The varnish also can limit certain operational parameters of the submersible motor. As a result, attempts have been made to construct submersible motors without varnish. Other insulating materials, including epoxies, have been used to cover the windings and end coils associated with the stator of the submersible motor. However, these approaches have proved inadequate in providing support for the winding end coils to prevent them from collapsing into the stator bore, particularly with larger submersible motors.
In general, the present invention provides a system and method for constructing a submersible motor. A stator is positioned within a housing, and stator windings are arranged with an end coil on an end of the stator. The winding end coil is supported by a support structure that prevents the end coil from collapsing inwardly and causing failure.
Certain embodiments of the invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and:
In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those of ordinary skill in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.
The present invention generally relates to a well system that utilizes a submersible motor. For example, a submersible motor may be used in an electric submersible pumping system to produce or otherwise move desired well fluids. The technique improves the run life of submersible motors and facilitates the use of both larger motors and motors constructed without varnish to isolate the stator and windings of the motor. In some applications, for example, motors are constructed without varnish to reduce cycle time and cost. However, removing the varnish also removes some of the support for the winding end coils.
In the present system and methodology, the end coils of the stator windings are supported by an insert. The insert prevents the winding end coils from moving and collapsing into the stator bore due to its own weight, thus avoiding failure or detrimental operation of the submersible motor. By way of specific example, the insert may comprise a conical structure positioned on the radially inward side of the end coils to prevent detrimental movement and collapse of the end coils in a radially inward direction toward the stator bore.
Referring generally to
In the embodiment illustrated, electric submersible pumping system 34 is designed for deployment in a well 40 within a geological formation 42 containing desirable production fluids, such as hydrocarbon based fluids. A wellbore 44 typically is drilled into formation 42 and, at least in some applications, is lined with a wellbore casing 46. The wellbore casing 46 is perforated to form a plurality of openings (perforations) 48 through which production fluids can flow from formation 42 into wellbore 44. In other applications, the submersible pumping system 34 can be used to deliver treatment fluids downhole and out through perforations 48 into the surrounding reservoir.
The electric submersible pumping system 34 may be deployed into wellbore 44 with a suitable conveyance system 50 that can be constructed in a variety of forms and configurations depending on the application. For example, conveyance system 50 may comprise a tubing 52, such as production tubing or coiled tubing. The conveyance system 50 is connected to submersible pump 36 or to another appropriate component of electric submersible pumping system 34 by a connector 54. In the embodiment illustrated, a power cable 56 is routed downhole along conveyance system 50 and electric submersible pumping system 34 to submersible motor 32. The power cable 56 provides electrical power to submersible motor 32 so the submersible motor can, in turn, power submersible pump 36. In operation, submersible pump 36 draws well fluid into the electric submersible pumping system 34 via a pump intake 58 and pumps the fluid to a collection location through, for example, tubing 52. By way of example, submersible motor 32 may comprise a three-phase, induction motor in which stator windings provide the motor field. The submersible motor may be constructed with/without varnish, and the stator windings have end coils that are uniquely supported with a support structure, as described in greater detail below.
Referring generally to
By way of example, stator 62 is formed with a plurality of laminations 70, such as steel laminations. The stack of steel laminations may be insulated by suitable insulating laminations 72 disposed at opposed axial ends of the lamination stack. In many applications, the laminations are perforated in a manner that creates generally axial slots to receive insulated wire conductors 74 that form the motor windings 76. At axial ends of the lamination stack, the insulated wire conductors 74 of the windings 76 are looped into end turns 77 that form winding end coils 78. The end turns 77 enable the insulated wire conductors 74 to be directed back through the lamination stack via axial slots according to a desired winding pattern. The insulated wire conductors 74 that form end coils 78 can be grouped together with each group secured by a suitable wrap 80 or other type of covering. Electrical power can be supplied to winding 76 via appropriate lead wires 82. If submersible motor 32 is a three-phase motor, the end coils 78 comprise end turns 77 for all three phases.
The end coils 78 are supported by a support structure 84 that limits or prevents radial collapse of the end coils by preventing undesirable movement of the end turns 77. Generally support structure 84 comprises an insert 86, and typically a pair of inserts 86, that are inserted at a radially inward position relative to the end coils 78, as illustrated in
In the embodiment illustrated, inserts 86 are preformed inserts constructed from a stiff, high temperature, insulation material. The inserts 86 may be secured in position by an appropriate adhesive material 88, such as glue or epoxy. The end coils 78 also can be infused or covered with the adhesive material 88, e.g. glue or epoxy, to further enhance the mechanical stability of the end coils. In some applications, the end coils 78 can be further supported by appropriate structures, such as coil forming blocks or wedges 90.
With added reference to
The shape, size, material and configuration of support structure 84 and inserts 86 can be adjusted according to the environment and the type/size of submersible motor 32. If a conical structure 92 is utilized, the diameter and length of the conical structure can vary from one application to another or even within the same submersible motor 32. In
The embodiments described above provide examples of submersible motors and support structures that can be used to improve the run life of a variety of well systems. It should be noted, however, that the support structures can be used to prevent the radially inward collapse of end coils in many types of motors and in a wide variety of well related applications. Additionally, the material used to create the support structure, the number of support structure components used in an individual motor, and the configuration of those components can be adjusted as needed for a given application. Though multiple end coils 78 are noted most often, one or more end coils are contemplated. Also, though end coils 78 and associated parts and description and most often contemplated with respect to both ends of a motor/stator device, it is contemplated that separate features are equally applicable to only one end thereof.
Accordingly, although only a few embodiments of the present invention have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this invention. Such modifications are intended to be included within the scope of this invention as defined in the claims.
