Thermally conductive wire insulation

Abstract

A compound for insulation may include a polymer and a filler. A method for insulating a wire using said compound comprises melting a polymer to form a molten polymer, mixing the molten polymer with a filler to form an insulation compound, applying the insulation compound along a wire, and cooling the insulation compound at a controlled rate to form a uniform crystal.

Description

PATENT Attorney Docket No. IS23 0166-WO-PCTTHERMALLY CONDUCTIVE WIRE INSULATIONCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] Any and all applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application are hereby incorporated by reference under 37 CFR 1.57. The present application claims priority benefit of U.S. Provisional Application No. 63 / 685,765, filed August 22, 2024, the entirety of which is incorporated by reference herein and should be considered part of this specification.BACKGROUND

[0002] High power induction and permanent magnet electric motors are commonly used in downhole, automotive, and industrial applications. A common problem across all industries is excessive heat buildup in the stator. Due to space constraints, there is a limit to how high the voltage can be increased without causing problems with discharge or insulator breakdown. As a result, power is increased by increasing motor amperage. Power is generated as the square of the amperage, so at high amperage, a significant amount of heat will be generated at the motor windings.SUMMARY

[0003] In some configurations a compound for insulation in electric motors includes a polymer and a filler. The polymer can be selected from the group consisting of polyarylether ketone (PAEK), polyester, polyimide, polyether-imide, polyamide, polyphenylene sulfide, or a combination thereof. The filler can be selected from the group consisting of alumina, alumina trihydrate, Boron nitride, silica, zinc oxide, silicon nitride, or a combination thereof. The filler can be a spherical, dielectric ceramic filler. The filler can be amorphous fused silica having a spherical morphology. A motor can include an electrically conductive winding, and insulation comprising the compound disposed about at least a portion of the electrically conductive winding. The motor can be used in an electric submersible pump.Schlumberger-Private Page 1 of 13PATENT Attorney Docket No. IS23 0166-WO-PCT

[0004] In some configurations, a method for insulating a wire includes melting a polymer to form a molten polymer; mixing the molten polymer with a filler to form an insulation compound; applying the insulation compound along a wire; and cooling the insulation compound at a controlled rate to form a uniform crystal. The uniform crystal can have a nominal final crystallinity of 25% to 40%. The polymer can be selected from the group consisting of polyarylether ketone (PAEK), polyester, polyimide, polyether-imide, polyamide, polyphenylene sulfide, or a combination thereof. The filler can be selected from the group consisting of alumina, alumina trihydrate, Boron nitride, silica, zinc oxide, silicon nitride, or a combination thereof. The filler can be a spherical, dielectric ceramic filler. The filler can be amorphous fused silica having a spherical morphology.

[0005] In some configurations, an electric motor includes a rotor and a stator. The stator includes a plurality of stacked stator laminations; a plurality of slots extending axially through and defined by the stacked stator laminations; magnet wire disposed within and extending axially through the slots; and magnet wire insulation surrounding the magnet wire. The magnet wire includes a polymer selected from the group consisting of polyarylether ketone (PAEK), polyester, polyimide, polyether-imide, polyamide, polyphenylene sulfide, or a combination thereof; and a filler selected from the group consisting of alumina, alumina trihydrate, Boron nitride, silica, zinc oxide, silicon nitride, or a combination thereof. The filler can be a spherical, dielectric ceramic filler. The filler can be amorphous fused silica having a spherical morphology. The motor can be included in an electric submersible pump.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Certain embodiments, features, aspects, and advantages of the disclosure will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. It should be understood that the accompanying figures illustrate the various implementations described herein and are not meant to limit the scope of various technologies described herein.

[0007] FIG. 1 shows a schematic of an electric submersible pump (ESP) system.

[0008] FIG. 2 shows a schematic of a portion of a motor of the ESP system.Schlumberger-Private Page 2 of 13PATENT Attorney Docket No. IS23 0166-WO-PCT

[0009] FIG. 3 shows a schematic of a portion of a stator of the motor of FIG. 2.DETAILED DESCRIPTION

[0010] In the following description, numerous details are set forth to provide an understanding of some embodiments of the present disclosure. It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the disclosure. These are, of course, merely examples and are not intended to be limiting. However, it will be understood by those of ordinary skill in the art that the system and / or methodology may be practiced without these details and that numerous variations or modifications from the described embodiments are possible. This description is not to be taken in a limiting sense, but rather made merely for the purpose of describing general principles of the implementations. The scope of the described implementations should be ascertained with reference to the issued claims.

[0011] Further, as used herein, the article “a” is intended to have its ordinary meaning in the patent arts, namely “one or more.” Herein, the term “about” when applied to a value generally means within the tolerance range of the equipment used to produce the value, or in some examples, means plus or minus 10%, or plus or minus 5%, or plus or minus 1%, unless otherwise expressly specified. Further, herein the term “substantially” as used herein means a majority, or almost all, or all, or an amount with a range of about 51% to about 100%, for example. Moreover, examples herein are intended to be illustrative only and are presented for discussion purposes and not by way of limitation.

[0012] High power induction and permanent magnet electric motors are commonly used in various industries, for example, downhole, automotive, and industrial applications. An example application for a downhole motor is an electric submersible pump (ESP), used for artificial lift in oil and gas applications. As shown in the example embodiment of Figure 1, an ESP 110 typically includes a motor 116, a protector 115, a pump 112, a pump intake 114, and one or more cables 111, which can include an electric power cable. The motor 116 can be powered and controlled by a surface power supply and controller, respectively, via the cables 111. In some configurations, the ESP 110 also includes gas handling features 113 and / or one or more sensors 117 (e.g., forSchlumberger-Private Page 3 of 13PATENT Attorney Docket No. IS23 0166-WO-PCT temperature, pressure, current leakage, vibration, etc.). As shown, the well may include one or more well sensors 120.

[0013] The motor 116 can include a stator disposed within a housing, and a rotor disposed within the stator. Figure 2 shows a perspective partial cut-away view of an example motor 116, including stacked stator laminations 680, stator or motor windings 670 of wire (e.g., electrically conductive winding or magnet wire), rotor laminations 690, and rotor windings 695. Figure 3 shows a portion of an example stator, including stator lamination 680 having a plurality of slots 782 lined with slot liner material 783, magnet wire 792 disposed within the slots, magnet wire insulation 791 surrounding the magnet wire 792, and polymeric material 793 at least partially filling spaces defined by the slots 782 of the lamination 680.

[0014] A common problem with electric motors is excessive heat buildup in the stator. Due to space constraints, there is a limit to how high the voltage can be increased without causing problems with discharge or insulator breakdown. As a result, power is increased by increasing motor amperage. Power is generated as the square of the amperage, so at high amperage, a significant amount of heat will be generated at the motor windings.

[0015] The present disclosure provides systems and methods for improved heat dissipation in motors. While systems and methods of the present disclosure can be used for ESP motors, these systems and methods can also or alternatively be used in and for other electric motors for other industries, particularly for any high amperage application. Currently used mechanisms to help dissipate heat in the motor include maximizing the copper slot fill; forcing convection of fluid - either through the rotor gap, outside the stator laminations, or through cooling channels in the laminations; and / or encapsulating the motor windings with a filled, thermally conductive resin.

[0016] A largely neglected area for improved heat dissipation in motors is improving the thermal conductivity of the wire insulation, for example, wire insulation 791 in the example motor 116 of Figures 2-3. As the wire insulation is closest to the primary heat source (the copper conductor) improving the insulation thermal conductivity at this location yields significantly better temperature reduction than improving thermal conductivity in materials farther away from the heat source (encapsulation, laminations, etc). However, motor designers have not used thermally conductive insulation materials because there is not an insulation material available that currently meets the requirements ofSchlumberger-Private Page 4 of 13PATENT Attorney Docket No. IS23 0166-WO-PCT a. Excellent dielectric properties - high dielectric strength. b. Sufficient ductility and flexibility to be bent and formed into coils. c. High thermal conductivity. d. Extrudable or processable into thin insulation layers on small wires.

[0017] Currently available thermally conductive materials achieve their heat dissipative properties by incorporating medium to high loadings of ceramic or inorganic fillers into the polymer matrix. However, incorporating a sufficiently high volume of filler into polymers tends to reinforce the material, resulting in a composite with a high melt viscosity, high modulus, and low elongation to break. These stiff, brittle materials are not well suited for motor winding. Therefore, there is a need for a low cost, high temperature, thermally conductive, and high dielectric strength insulation material with significantly improved flexibility and ductility.

[0018] The present disclosure provides methods and formulations for incorporation of high filler loadings into a polymer while maintaining sufficiently low modulus and flexibility. This advantageously allows for manufacture of improved insulation material with significantly improved flexibility and ductility for motor winding. By reducing the operating temperature of the cable, this insulation material allows for either more efficient power transfer (less loss) or for higher power output (increased amperage).

[0019] Moreover, by utilizing a filler material of selected morphology and surface area and controlling the particle size distribution, a significant loading of thermally conductive filler can be incorporated into a high temperature thermoplastic polymer matrix. Through careful control of these factors, a final composite can be manufactured that incorporates a high volume of filler while retaining low viscosity for good processability, as well as a low modulus and high elongation for improved ductility in bending and winding.

[0020] In some configurations, methods and formulations according to the present disclosure provide a polymer composite filled with a high-volume fraction of spherical, dielectric ceramic fillers. The high filler content and the particle morphology control result in a final product with a unique combination of valuable properties such as: a. High thermal conductivity b. Low thermal expansionSchlumberger-Private Page 5 of 13PATENT Attorney Docket No. IS23 0166-WO-PCT c. Improved dielectric properties (higher resistivity and lower loss) vs. virgin polymer d. Good processability e. Minimum increase in stiffness (vs. virgin polymer) f. High elongation at breakThese properties are especially valuable for a heat dissipative thin wall dielectric material for use in high output electric motors.Polymer Selection

[0021] There are several critical considerations or criteria in the selection of polymer for formulations according to the present disclosure: a. Sufficiently low melt viscosity to be melt processable for filler incorporation, and for extrusion / inj ection molding of components afterward. b. Good compatibility with the selected filler. c. Inherently good dielectric properties. d. Good toughness and elongation at break when unfilled.

[0022] In one example, polyarylether ketone (PAEK) polymers have shown to be ideal or preferred due to their excellent fluid and heat resistance. In particular, Solvay XT-920 based “high temperature” PAEK has a higher glass transition temperature (Tg) and melting temperature (Tm) vs. standard PAEK as well as excellent elongation at break. This combination is well suited to oil and gas equipment. However, there are a number of other polymers apart from the above example that could also be suitable for this application, especially in other industries, for example, polyester, polyimide, polyether-imide, polyamide, or polyphenylene sulfide.Filler Selection

[0023] A critical element of formulations according to the present disclosure is the filler selection. The filler should be selected from a group of materials that have excellent dielectric properties as well as good thermal conductivity. Examples include, but are not limited to, Alumina, alumina trihydrate, Boron nitride, silica, zinc oxide, or silicon nitride.Schlumberger-Private Page 6 of 13PATENT Attorney Docket No. IS23 0166-WO-PCT

[0024] In some configurations, the proposed filler used is amorphous fused silica with a spherical morphology. By processing ground silica through a flame spray method, nearly perfect spherical particulates can be obtained. The spherical shape provides the lowest possible surface area relative to the volume, and particles prepared in this manner consist of single dense particles, without porosity or agglomeration. The ultra-low relative surface area allows for the minimum amount of polymer-filler interaction relative to the amount of filler introduced. As the surface area is the only part of the particle that interacts with the polymer matrix, this parameter is critical for achieving the desired properties.

[0025] In some configurations, in addition to the particle morphology, the particle size and size distribution (PSD) are also critical for the below reasons: a. Particles that are too large will create defects in the matrix that will be weak points for dielectric or mechanical failure. b. Particles that are too small will have a relatively high surface area: volume ratio, resulting in a higher degree of polymer filler interaction. This mechanism increases the reinforcing behavior of the filler, resulting in higher viscosity, higher stiffness, and lower elongation at break of the final product. For many applications this may be desirable, but for this application it is not. c. A monodisperse distribution (all particles the same size) is also not desirable as it limits the packing ability. Rather a distribution of particles of relatively small, medium and large sizes is ideal for optimal packing.

[0026] Various silica grade PSDs are possible. In some configurations, the 507M particle has the ideal or a preferred PSD. The narrow distribution minimizes small, high surface area particles that increase viscosity while limiting the size and number of large particles resulting in greater retained elongation at break.Manufacturing Process

[0027] As with any polymer based final product, the manufacturing process is critical in ensuring the optimum final properties. This is especially true for PAEK type polymers as used in configurations according to the present disclosure.Schlumberger-Private Page 7 of 13PATENT Attorney Docket No. IS23 0166-WO-PCT

[0028] In some configurations of the present invention, to ensure a final product with the highest possible elongation, the temperature of the wire and the polymer melt must be well controlled. After application of the molten polymer to the wire, the cooling rate of the polymer must also be controlled. If the polymer is cooled too quickly, thermal stresses will create a matrix prone to cracking. If it is cooled too slowly, the material may sag and form an uneven wall around the wire. Some PAEK materials if cooled too slowly will also achieve close to the maximum possible crystallinity, which will also result in reduced elongation and higher stiffness.

[0029] An ideal cooling process will result in a uniform crystallinity through the wall thickness and a nominal final crystallinity of 25-40%.Experimental Results

[0030] In the development of formulations according to the present disclosure, numerous trials were held to experimentally determine the ideal filler material and loading. Table 1 below shows a unique compound with significantly improved thermal conductivity while retaining toughness and elongation at break.Table 1 : HT-HK PAEK Compound data

[0031] For comparison, Table 2 below highlights the most commonly used commercially available Victrex PAEK grade (450G) in comparison to a 20% by volume silica glass fiber filled version (450GL30).Table 2: Victrex PAEK 450G vs 450GL30 (Victrex Data Sheet information)Schlumberger-Private Page 8 of 13PATENT Attorney Docket No. IS23 0166-WO-PCTAs shown in table 2, the 20% filled version (450GL30) is able to achieve a much higher thermal conductivity at a much lower loss of elongation and much improved flexibility / ductility . In addition to the results shown above, loading may be pushed to higher levels to further increase thermal conductivity.

[0032] As shown, formulations according to the present disclosure demonstrate a novel approach to significantly improve wire insulation performance.

[0033] In some configurations, while especially valuable in high output electric motors, this material design could be used in any area where a heat dissipative dielectric material would be desired, such as power cables, electrical connectors, dielectric films, overmolded feedthroughs, electrical bulkheads, etc.

[0034] The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the disclosure. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the systems and methods described herein. The foregoing descriptions of specific examples are presented for purposes of illustration and description. They are not intended to be exhaustive of or to limit this disclosure to the precise forms described. Obviously, many modifications and variations are possible in view of the above teachings. The examples are shown and described in order to best explain the principles of this disclosure and practical applications, to thereby enable others skilled in the art to best utilize this disclosure and various examples with various modifications as are suited to the particular use contemplated. It is intended that the scope of this disclosure be defined by the claims and their equivalents below.Schlumberger-Private Page 9 of 13

Claims

PATENT Attorney Docket No. IS23 0166-WO-PCTCLAIMSWhat is claimed is:

1. A compound for insulation comprising: a polymer; and a filler.

2. The compound for insulation of claim 1, wherein the polymer is selected from the group consisting of polyarylether ketone (PAEK), polyester, polyimide, polyether-imide, polyamide, polyphenylene sulfide, or a combination thereof.

3. The compound for insulation of claim 1, wherein the filler is selected from the group consisting of alumina, alumina trihydrate, Boron nitride, silica, zinc oxide, silicon nitride, or a combination thereof.

4. The compound for insulation of claim 1, wherein the filler is a spherical, dielectric ceramic filler.

5. The compound for insulation of claim 1, wherein the filler is amorphous fused silica having a spherical morphology.

6. A motor comprising an electrically conductive winding; and insulation disposed about at least a portion of the electrically conductive winding, the insulation comprising the compound of any of claims 1-5.

7. An electric submersible pump comprising the motor of claim 6.

8. A method for insulating a wire comprising: melting a polymer to form a molten polymer; mixing the molten polymer with a filler to form an insulation compound; applying the insulation compound along a wire; and cooling the insulation compound at a controlled rate to form a uniform crystal.Schlumberger-Private Page 10 of 13PATENT Attorney Docket No. IS23 0166-WO-PCT9. The method of claim 6, wherein the uniform crystal has a nominal final crystallinity of 25% to 40%.

10. The method of claim 6, wherein the polymer is selected from the group consisting of polyarylether ketone (PAEK), polyester, polyimide, polyether-imide, polyamide, polyphenylene sulfide, or a combination thereof.

11. The method of claim 6, wherein the filler is selected form the group consisting of alumina, alumina trihydrate, Boron nitride, silica, zinc oxide, silicon nitride, or a combination thereof.

12. The method of claim 6, wherein the filler is a spherical, dielectric ceramic filler.

13. The method of claim 6, wherein the filler is amorphous fused silica having a spherical morphology.

14. An electric motor comprising: a rotor; and a stator, the stator comprising: a plurality of stacked stator laminations; a plurality of slots extending axially through and defined by the stacked stator laminations; magnet wire disposed within and extending axially through the slots; and magnet wire insulation surrounding the magnet wire, the magnet wire insulation comprising: a polymer selected from the group consisting of polyarylether ketone (PAEK), polyester, polyimide, polyether-imide, polyamide, polyphenylene sulfide, or a combination thereof; and a filler selected from the group consisting of alumina, alumina trihydrate, Boron nitride, silica, zinc oxide, silicon nitride, or a combination thereof.

15. The electric motor of Claim 14, wherein the filler is a spherical, dielectric ceramic filler.Schlumberger-Private Page 11 of 13PATENT Attorney Docket No. IS23 0166-WO-PCT16. The electric motor of Claim 14, wherein the filler is amorphous fused silica having a spherical morphology.

17. An electric submersible pump comprising the electric motor of Claim 14.Schlumberger-Private Page 12 of 13

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