Patent Application
20140145530
This invention relates generally to the field of electric motors, and more particularly, but not by way of limitation, to improved magnet wire for use in high-temperature downhole pumping applications.
Electrodynamic systems such as electric motors, generators, and alternators typically include a stator and a rotor. The stator typically has a metallic core with electrically insulated wire winding through the metallic core to form the stator coil. When current is alternately passed through a series of coils, magnetic flux fields are formed, which cause the rotor to rotate in accordance with electromagnetic physics. To wind the stator coil, the wire is first threaded through the stator core in one direction, and then turned and threaded back through the stator in the opposite direction until the entire stator coil is wound. Each time the wire is turned to run back through the stator, an end turn is produced. A typical motor will have many such end turns upon completion.
Electrical submersible pumping systems include specialized electric motors that are used to power one or more high performance pump assemblies. The motor is typically an oil-filled, high capacity electric motor that can vary in length from a few feet to nearly fifty feet, and may be rated up to hundreds of horsepower. The electrical submersible pumping systems are often subjected to high-temperature, corrosive environments. Each component within the electrical submersible pump must be designed and manufactured to withstand these hostile conditions.
In the past, motor manufacturers have used various insulating materials on the magnet wire used to wind the stator. Commonly used insulation includes polyether ether ketone (PEEK) thermoplastics. Insulating the conductor in the magnet wire prevents the electrical circuit from shorting or otherwise prematurely failing. The insulating material is typically extruded or sprayed onto the underlying copper conductor. In recent years, manufacturers have used insulating materials that are resistant to heat, mechanical wear and chemical exposure.
Although widely accepted, current insulation materials may be inadequate for certain high-temperature downhole applications. In particular, motors employed in downhole applications where modern steam-assisted gravity drainage (SAGD) recovery methods are employed, the motor may be subjected to elevated temperatures. There is, therefore, a need for an improved magnet wire that exhibits enhanced resistance to heat, corrosive chemicals, mechanical wear and other aggravating factors. It is to this and other deficiencies in the prior art that the present invention is directed.
In a preferred embodiment, the present invention provides an electric motor assembly configured for use in a downhole pumping system. The motor assembly includes a plurality of stator coils and each of the plurality of stator coils includes magnet wire that has an insulator surrounding a conductor. In preferred embodiments, the insulator is manufactured from a material selected from the group consisting of polyether ketone and polyether ketone ether ketone ketone.
In accordance with a preferred embodiment of the present invention,
As used herein, the term “petroleum” refers broadly to all mineral hydrocarbons, such as crude oil, gas and combinations of oil and gas. The production tubing 102 connects the pumping system 100 to a wellhead 106 located on the surface. Although the pumping system 100 is primarily designed to pump petroleum products, it will be understood that the present invention can also be used to move other fluids. It will also be understood that, although each of the components of the pumping system 100 are primarily disclosed in a submersible application, some or all of these components can also be used in surface pumping operations.
The pumping system 100 preferably includes some combination of a pump assembly 108, a motor assembly 110 and a seal section 112. In a preferred embodiment, the motor assembly 110 is an electrical motor that receives its power from a surface-based supply. The motor assembly 110 converts the electrical energy into mechanical energy, which is transmitted to the pump assembly 108 by one or more shafts. The pump assembly 108 then transfers a portion of this mechanical energy to fluids within the wellbore, causing the wellbore fluids to move through the production tubing to the surface. In a particularly preferred embodiment, the pump assembly 108 is a turbomachine that uses one or more impellers and diffusers to convert mechanical energy into pressure head. In an alternative embodiment, the pump assembly 108 is a progressive cavity (PC) or positive displacement pump that moves wellbore fluids with one or more screws or pistons.
The seal section 112 shields the motor assembly 110 from mechanical thrust produced by the pump assembly 108. The seal section 112 is also preferably configured to prevent the introduction of contaminants from the wellbore 104 into the motor assembly 110. Although only one pump assembly 108, seal section 112 and motor assembly 110 are shown, it will be understood that the downhole pumping system 100 could include additional pumps assemblies 108, seals sections 112 or motor assemblies 110.
Referring now to
The stator core 126 includes multiple stator slots. Each stator coil is preferably created by winding a magnet wire 128 back and forth though slots in the stator core 126. Each time the magnet wire 128 is turned 180° to be threaded back through an opposing slot, an end turn (not shown in
Electricity flowing through the stator 122 according to different commutation states creates a rotating magnetic field, which acts upon rotor bars (not shown) and causes the rotor 124 to rotate. This, in turn, rotates the shaft 120. The phases in a motor assembly 110 are created by sequentially energizing adjacent stator coils, thus creating the rotating magnetic field. Motors can be designed to have different numbers of phases and different numbers of poles. In a preferred embodiment, an ESP motor is a two pole, three phase motor in which each phase is offset by 120°. It will be understood, however, that the method of the preferred embodiment will find utility in motors with different structural and functional configurations or characteristics.
Turning to
In a first preferred embodiment, the insulator 132 is a polyether ketone (PEK) thermoplastic. Particularly preferred PEK thermoplastics have a melting point of above about 373° C. Suitable PEK insulation is available from Victrex Manufacturing Limited, Rotherham, South Yorkshire, United Kingdom, under the Victrex-HT line of products. Particularly preferred products include Victrex® PEEK-HT™ G22 brand PEK thermoplastic.
In a second preferred embodiment, the insulator 132 is a polyetherketoneehterketonekteone (PEKEKK) thermoplastic having a melting point of above about 387° C. Suitable PEKEKK insulation is available from Victrex Manufacturing Limited, Rotherham, South Yorkshire, United Kingdom, under the Victrex-ST line of products. Particularly preferred products include Victrex® ST™ STG45 brand PEKEKK thermoplastic.
The insulator 132 is preferably extruded onto the conductor 130 to provide a seamless layer of insulation having a consistent thickness. The thickness of the insulator 132 can be adjusted during manufacturing of the magnet wire 128 to meet the requirements of particular applications. Although a single form of insulation has traditionally been used, it is contemplated as within the scope of the present invention to magnet wire 128 having different insulators 132 on different portions of the conductor 130. For example, it may be desirable to use higher-temperature insulator 132 on portions of the magnet wire 128 that are exposed to higher temperatures within the motor assembly 110. The use of PEK and PEKEKK insulators 132 significantly increases the thermal resistance of the magnet wire 128 over the prior art use of traditional polyarylketones, such as polyether ether ketone (PEEK).
In alternate embodiment, one or more fillers are added to the PEK or PEKEKK to form a composite insulator 132. Suitable fillers include glass fiber, talc and other minerals. In yet an additional embodiment, glass fibers can be used to create a separate glass fiber cloth layer that is distinct from the glass fiber filler used in the composite insulator 132. Furthermore, it may be desirable to prepare a magnet wire 128 that includes multiple layers of insulator 132. In a first preferred multilayer embodiment, the magnet wire includes an inner layer constructed from a first insulator selected from the group consisting of PEK, PEKEKK, composite insulators, glass fiber cloth, and polyimide films and an outer layer constructed from a second insulator selected from the group consisting of PEK, PEKEKK, composite insulators, glass fiber cloth and polyimide films. In particularly preferred embodiments, the magnet wire 128 includes an outer insulation layer constructed from PEK or PEKEKK.
Turning to
The power cable conductors 136 are preferably manufactured from copper wire or other suitable metal. The power cable conductors 136 can include a solid core (as shown in
In a first preferred embodiment, the power cable insulators 138 preferably include at least one layer of a polyether ketone (PEK) thermoplastic having a melting point of above about 373° C. Suitable PEK insulation is available from Victrex Manufacturing Limited, Rotherham, South Yorkshire, United Kingdom, under the Victrex-HT line of products. Particularly preferred products include Victrex® PEEK-HT™ G22 brand PEK thermoplastic. In a second preferred embodiment, the power cable insulators 138 include at least one layer of a polyetherketoneehterketonekteone (PEKEKK) thermoplastic having a melting point of above about 387° C. Suitable PEKEKK insulation is available from Victrex Manufacturing Limited, Rotherham, South Yorkshire, United Kingdom, under the Victrex-ST line of products. Particularly preferred products include Victrex® ST™ G45 brand PEKEKK thermoplastic.
It may be desirable to prepare a power cable 134 that includes multiple layers of power cable insulator 138 around the power cable conductor 136. In a first preferred multilayer embodiment, the magnet wire includes an inner layer constructed from a first insulator selected from the group consisting of PEK, PEKEKK, glass fiber filler and polyimide films and an outer layer constructed from a second insulator selected from the group consisting of PEK, PEKEKK, glass fiber cloth and polyimide films. In particularly preferred embodiments, the magnet wire 128 includes an outer insulation layer constructed from PEK or PEKEKK.
It is to be understood that even though numerous characteristics and advantages of various embodiments of the present invention have been set forth in the foregoing description, together with details of the structure and functions of various embodiments of the invention, this disclosure is illustrative only, and changes may be made in detail, especially in matters of structure and arrangement of parts within the principles of the present invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. It will be appreciated by those skilled in the art that the teachings of the present invention can be applied to other systems without departing from the scope and spirit of the present invention.
