Stator winding for power system

Abstract

A stator winding is provided that includes a protective member that covers and surrounds at least a portion of the conductive member. The protective member includes a polymer composition that includes a polymer matrix including a thermotropic liquid crystal polymer. The polymer composition exhibits a melt viscosity of about 150 Pa·s or less and a heat deflection temperature of about 170°C or higher.

Description

Background Art

[0001]

[0001] Electric vehicles such as battery - powered electric vehicles, plug - in hybrid electric vehicles, mild hybrid electric vehicles, or full hybrid electric vehicles generally have an electric powertrain containing an electric propulsion source (e.g., a battery) and a transmission. The electric motors used in such vehicles generally contain a stator and a rotor disposed within a housing. The rotor can be attached to a generally cylindrical shaft that is coaxial with the stator and is rotatably mounted within the housing. The stator may include a generally cylindrical stator body in which a plurality of slots are formed. A plurality of copper wires are formed in the slots of the stator body in a predetermined polyphase (e.g., 3 - phase or 6 - phase) winding pattern. The copper wires are typically coated with an insulator to prevent excessive heat generation, fire concerns, electric shock, and to ensure the proper functioning and safety of the conductors and the related devices (if any). Materials that have been used for the insulator include polyetheretherketone ("PEEK") due to its allowable temperature range for high - temperature use and its inherent resistance to many chemical substances present in industrial and automotive environments. However, unfortunately, PEEK has poor melt - flow characteristics, so it is often difficult to directly extrude it onto the copper wires. Further, attempting to change the flow characteristics tends to adversely affect other properties of the insulator, such as mechanical properties and / or thermal conductivity. Therefore, currently, there is a need for improvement in the stator windings used in the power system of the stator.

Summary of the Invention

Means for Solving the Problems

[0002]

[0002] According to one embodiment of the present invention, a stator winding is disclosed that includes a protective member covering and surrounding at least a part of a conductive member. The protective member includes a polymer composition member containing a polymer composition including a polymer matrix containing a thermotropic liquid - crystal polymer. The polymer composition exhibits a melt viscosity of about 300 Pa·s or less and a deflection temperature under load of about 170°C or higher.

[0003]

[0003] Other features and aspects of the present invention will be described in more detail below.

[0004] A complete and enabling disclosure of the present invention, including the best mode thereof for those skilled in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying drawings.

Brief Description of the Drawings

[0004]

Figure 1

[0005] It is a cross-sectional view of one embodiment of the stator winding of the present invention.

Figure 2

[0006] It is a cross-sectional view of another embodiment of the stator winding of the present invention.

Figure 3

[0007] It is an end view of one embodiment of a stator that can use the stator winding of the present invention.

Figure 4

[0008] It is a view of one embodiment of a power system that can use the stator of FIG. 3.

Figure 5

[0009] It is a view showing one embodiment of an electric vehicle that can use the stator winding of the present invention.

Best Mode for Carrying Out the Invention

[0005]

[0010] It will be understood by those skilled in the art that this discussion is only a description of exemplary embodiments and is not intended to limit the broader aspects of the present invention.

[0011] Generally speaking, the present invention relates to a stator and a stator winding for use in an electric power system. The stator winding includes a protective member that covers at least a portion of a conductive member (e.g., a copper wire). In particular, the protective member contains a polymer composition including a liquid crystal polymer and exhibits a combination of high flow characteristics and good heat resistance. More specifically, the composition has a shear rate of 1,000 s -1and at a temperature about 15 °C higher than the melting temperature of the composition (e.g., about 350 °C), shows a melt viscosity of about 300 Pa·s or less, in some embodiments about 150 Pa·s or less, in some embodiments about 5 to 100 Pa·s, in some embodiments about 10 to about 95 Pa·s, in some embodiments about 15 to about 80 Pa·s, as measured according to ISO 11443:2021. The deflection temperature under load (“DTUL”), which is a measure of short-term heat resistance, can also remain relatively high. For example, the DTUL can be about 170 °C or higher, in some embodiments about 200 °C or higher, in some embodiments about 210 °C to about 300 °C, in some embodiments about 220 °C to about 280 °C, as measured at a load of 1.8 MPa according to, for example, ISO 75:2013. Even with such DTUL values, the ratio of the melting temperature to the DTUL value can still remain relatively high. For example, this ratio can be in the range of about 0.5 to about 1.00, in some embodiments about 0.6 to about 0.95, in some embodiments about 0.65 to about 0.85. The detailed melting temperature of the polymer composition can be, for example, about 250 °C to about 440 °C, in some embodiments about 260 °C to about 400 °C, in some embodiments about 300 °C to about 380 °C.

[0006]

[0012] In addition to exhibiting good flow characteristics and heat resistance, the polymer composition can exhibit a high thermal conductivity. Such a high thermal conductivity value enables the composition to form a thermal path for heat transfer away from the conductive elements of the stator winding. In this way, "hot spots" can be quickly eliminated and the overall temperature during use can be reduced. The polymer composition can exhibit an in-plane (or "flow") thermal conductivity of, for example, about 2 W / m·K or more as measured according to ASTM E 1461-13(2022), about 2.5 to about 15 W / m·K in some embodiments, about 3 to about 10 W / m·K in some embodiments, and about 4 to about 8 W / m·K in some embodiments. Similarly, the polymer composition can exhibit a cross-plane (or "cross-flow") thermal conductivity of about 0.8 W / m·K or more as measured according to ASTM E1461-13(2022), about 1 to about 12 W / m·K in some embodiments, and about 2 to about 8 W / m·K in some embodiments. The composition can also exhibit an out-of-plane thermal conductivity of about 0.2 W / m·K or more as measured according to ASTM E 1461-13(2022), about 0.3 W / m·K or more in some embodiments, about 0.5 to about 4 W / m·K in some embodiments, and about 0.6 to about 2 W / m·K in some embodiments.

[0007]

[0013] While being thermally conductive, the polymer composition is electrically insulating and can maintain a high short-time dielectric strength even when exposed to an electric field. "Dielectric strength" generally refers to the voltage that a material can withstand before breakdown occurs. For example, the polymer composition generally exhibits a dielectric strength of about 10 kilovolts per millimeter (kV / mm) or more, in some embodiments about 15 kV / mm or more, and in some embodiments about 25 kV / mm to about 60 kV / mm, as measured in accordance with, for example, IEC 60234-1:2013. The insulation properties of the polymer composition can also be characterized by a high comparative tracking index ("CTI") of about 150 volts or more, in some embodiments about 170 volts or more, in some embodiments about 200 volts or more, and in some embodiments about 220 to about 350 volts, as measured in accordance with, for example, IEC 60112:2003 at a thickness of 3 millimeters.

[0008]

[0014] Despite having the above characteristics, the polymer composition can maintain high strength, thereby providing improved flexibility and impact resistance. The polymer composition can have, for example, a tensile breaking stress (i.e., strength) of about 40 Mpa to about 300 MPa, in some embodiments about 50 MPa to about 250 MPa, and in some embodiments about 70 to about 200 MPa; a tensile breaking strain (i.e., elongation) of 0.5% or more, in some embodiments about 1% to about 8%, and in some embodiments about 2% to about 5%; and / or a tensile modulus of about 5,000 to about 30,000 MPa, in some embodiments about 6,000 MPa to about 25,000 MPa, and in some embodiments about 9,000 MPa to about 22,000 MPa. The tensile properties can be determined at a temperature of 23 °C in accordance with ISO 527:2019. The composition can also have a flexural strength of about 20 MPa or more, in some embodiments about 50 to about 300 MPa, in some embodiments about 70 to about 250 MPa, and in some embodiments about 80 to about 200 MPa; and / or a flexural modulus of about 10,000 MPa or less, in some embodiments about 5,00 MPa to about 30,000 MPa, in some embodiments about 8,000 MPa to about 25,000 MPa, and in some embodiments about 9,000 MPa to about 20,000 MPa. The flexural properties can be determined at a temperature of 23 °C in accordance with ISO 178:2019. The polymer composition can also exhibit high impact strength, thereby imparting improved flexibility to the resulting parts. For example, the polymer composition has a notched Charpy impact strength of about 2 kJ / m 2 or more, in some embodiments about 4 to about 20 kJ / m 2 and in some embodiments about 6 to about 18 kJ / m 2 and / or a notched Charpy impact strength of about 10 kJ / m 2 or more, in some embodiments about 15 to about 50 kJ / m 2 and in some embodiments about 20 to about 40 kJ / m 2 as measured at 23 °C in accordance with ISO 179-1:2010.

[0009]

[0015] Here, various embodiments of the present invention will be described in more detail. I. Polymer Composition A. Polymer Matrix

[0016] As described above, the polymer matrix contains at least one liquid crystal polymer. For example, the liquid crystal polymer typically constitutes about 50% to 100% by weight of the polymer matrix, in some embodiments about 70% to 100% by weight, and in some embodiments about 90% to 100% by weight (e.g., 100% by weight). The liquid crystal polymer generally has a rod-like structure and is classified as "thermotropic" as long as it can exhibit crystalline behavior in a molten state (e.g., a thermotropic nematic state). Such polymers typically have a DTUL value of about 200°C to about 340°C, in some embodiments about 210°C to about 300°C, and in some embodiments about 220°C to about 280°C, measured at a load of 1.8 MPa in accordance with ISO 75-2:2013. The polymer may also have a relatively high melting temperature of about 250°C to about 440°C, in some embodiments about 260°C to about 400°C, and in some embodiments about 300°C to about 380°C. The polymer can be formed from one or more repeating units, as is known in the art. The liquid crystal polymer may, for example, generally contain one or more aromatic ester repeating units represented by the following formula (I).

[0010]

Chemical formula

[0011] (In the formula, Ring B is a substituted or unsubstituted 6-membered aryl group (e.g., 1,4-phenylene or 1,3-phenylene), a substituted or unsubstituted 6-membered aryl group condensed with a substituted or unsubstituted 5- or 6-membered aryl group (e.g., 2,6-naphthalene), or a substituted or unsubstituted 6-membered aryl group bonded to a substituted or unsubstituted 5- or 6-membered aryl group (e.g., 4,4-biphenylene); Y1 and Y2 are independently O, C(O), NH, C(O)HN, or NHC(O).

[0017] Typically, at least one of Y1 and Y2 is C(O). Examples of such aromatic ester repeating units include, for example, aromatic dicarboxylic acid repeating units (in formula I, Y1 and Y2 are C(O)), aromatic hydroxycarboxylic acid repeating units (in formula I, Y1 is O and Y2 is C(O)), and various combinations thereof.

[0012]

[0018] Aromatic hydroxycarboxylic acid repeating units are derived from, for example, aromatic hydroxycarboxylic acids such as 4-hydroxybenzoic acid; 4-hydroxy-4'-biphenylcarboxylic acid; 2-hydroxy-6-naphthoic acid; 2-hydroxy-5-naphthoic acid; 3-hydroxy-2-naphthoic acid; 2-hydroxy-3-naphthoic acid; 4'-hydroxyphenyl-4-benzoic acid; 3'-hydroxyphenyl-4-benzoic acid; 4'-hydroxyphenyl-3-benzoic acid, etc., as well as their alkyl, alkoxy, aryl, and halogen substituents, and combinations thereof. Particularly preferred aromatic hydroxycarboxylic acids are 4-hydroxybenzoic acid ("HBA") and 6-hydroxy-2-naphthoic acid ("HNA"). When used, the repeating units derived from hydroxycarboxylic acids (e.g., HBA and / or HNA) typically constitute about 20 mol% to about 80 mol% of the polymer, in some embodiments about 25 mol% to about 75 mol%, and in some embodiments about 30 mol% to about 70 mol%.

[0013]

[0019] The aromatic dicarboxylic acid repeating unit can also be derived from aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyl ether-4,4'-dicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 4,4'-dicarboxybiphenyl, bis(4-carboxyphenyl) ether, bis(4-carboxyphenyl) butane, bis(4-carboxyphenyl) ethane, bis(3-carboxyphenyl) ether, bis(3-carboxyphenyl) ethane, etc., as well as their alkyl, alkoxy, aryl and halogen substituents, and combinations thereof can be used. Particularly preferred aromatic dicarboxylic acids include, for example, terephthalic acid ("TA"), isophthalic acid ("IA"), and 2,6-naphthalenedicarboxylic acid ("NDA"). When used, the repeating unit derived from the aromatic dicarboxylic acid (e.g., IA, TA, and / or NDA) typically constitutes from about 1 mol% to about 50 mol% of the polymer, in some embodiments from about 5 mol% to about 40 mol%, and in some embodiments from about 10 mol% to about 35 mol%.

[0014]

[0020] Other repeating units may also be used in the polymer. In certain embodiments, for example, repeating units derived from aromatic diols such as hydroquinone, resorcinol, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 4,4'-dihydroxybiphenyl (or 4,4'-biphenol), 3,3'-dihydroxybiphenyl, 3,4'-dihydroxybiphenyl, 4,4'-dihydroxybiphenyl ether, bis(4-hydroxyphenyl)ethane, etc., as well as their alkyl, alkoxy, aryl and halogen substituents, and combinations thereof may be used. Particularly suitable aromatic diols include, for example, hydroquinone ("HQ") and 4,4'-biphenol ("BP"). When used, the repeating units derived from aromatic diols (e.g., HQ and / or BP) typically constitute from about 1 mol% to about 40 mol% of the polymer, from about 2 mol% to about 35 mol% in some embodiments, and from about 5 mol% to about 30 mol% in some embodiments. Also, repeating units derived from aromatic amides (e.g., acetaminophen ("APAP")) and / or aromatic amines (e.g., 4-aminophenol ("AP"), 3-aminophenol, 1,4-phenylenediamine, 1,3-phenylenediamine, etc.) may also be used. When used, the repeating units derived from aromatic amides (e.g., APAP) and / or aromatic amines (e.g., AP) typically constitute from about 0.1 mol% to about 20 mol% of the polymer, from about 0.5 mol% to about 15 mol% in some embodiments, and from about 1 mol% to about 10 mol% in some embodiments. It should also be understood that various other monomer repeating units may be incorporated into the polymer. For example, in certain embodiments, the polymer may contain one or more repeating units derived from non-aromatic monomers such as aliphatic or alicyclic hydroxycarboxylic acids, dicarboxylic acids, diols, amides, amines, etc.Of course, in other embodiments, the polymer may be "wholly aromatic" in that it has no repeating units derived from non-aromatic (e.g., aliphatic or alicyclic) monomers.

[0015]

[0021] Although not required, the liquid crystal polymer may be a "high naphthenic" polymer in that it has a relatively high content of repeating units derived from naphthenic hydroxycarboxylic acids and naphthenic dicarboxylic acids such as NDA, HNA, or combinations thereof. That is, the total amount of repeating units derived from naphthenic hydroxycarboxylic acids and / or dicarboxylic acids (e.g., NDA, HNA, or a combination of HNA and NDA) is typically at least about 10 mol% of the polymer, at least about 12 mol% in some embodiments, at least about 15 mol% in some embodiments, from about 15 mol% to about 50 mol% in some embodiments, and from 16 mol% to about 30 mol% in some embodiments. In one embodiment, for example, the repeating units derived from NDA are within the above ranges. The liquid crystal polymer may also contain various other monomers. For example, the polymer may contain repeating units derived from HBA in an amount of from about 20 mol% to about 60 mol%, from about 25 mol% to about 55 mol% in some embodiments, and from about 30 mol% to about 50 mol% in some embodiments. The polymer may also contain aromatic dicarboxylic acids (e.g., IA and / or TA) in an amount of from about 1 mol% to about 15 mol% and / or aromatic diols (e.g., BP and / or HQ) in an amount of from about 10 mol% to about 35 mol%. Of course, in other embodiments, the liquid crystal polymer may be a "low naphthenic" polymer in that it has a relatively low content of repeating units derived from naphthenic hydroxycarboxylic acids and naphthenic dicarboxylic acids such as naphthalene-2,6-dicarboxylic acid ("NDA"), 6-hydroxy-2-naphthoic acid ("HNA"), or combinations thereof. That is, the total amount of repeating units derived from naphthenic hydroxycarboxylic acids and / or dicarboxylic acids (e.g., NDA, HNA, or a combination of HNA and NDA) can be at most about 10 mol% of the polymer, at most about 8 mol% in some embodiments, and from about 1 mol% to about 6 mol% in some embodiments.

[0016]

[0022] In many cases, it is desirable that a substantial portion of the polymer matrix be formed from such high-naphthenic polymers. For example, the high-naphthenic polymers described herein typically constitute 50% by weight or more of the polymer matrix, in some embodiments about 65% by weight or more, in some embodiments about 70% to 100% by weight, and in some embodiments about 80% to 100% (e.g., 100% by weight). In some cases, blends of polymers may also be used. For example, the low-naphthenic liquid crystal polymer may constitute about 1% to about 50% by weight of the total amount of liquid crystal polymers in the composition, in some embodiments about 2% to about 40% by weight, and in some embodiments about 5% to about 30% by weight, and the high-naphthenic liquid crystal polymer may constitute about 50% to about 99% by weight of the total amount of liquid crystal polymers in the composition, in some embodiments about 60% to about 98% by weight, and in some embodiments about 70% to about 95% by weight.

[0017] B. Optional Additive

[0023] In certain embodiments, the polymer composition may be entirely formed from the polymer matrix (i.e., 100% by weight). Of course, in other embodiments, one or more additives may be dispersed throughout the polymer matrix to help provide the desired properties. When used, such additives typically constitute about 0.1 to about 300 parts by weight, in some embodiments about 0.5 to about 250 parts by weight, and in some embodiments about 1 to about 200 parts by weight, per 100 parts by weight of the polymer matrix. The additives may, for example, constitute about 0.1% to about 80% by weight of the polymer composition, in some embodiments about 0.5% to about 70% by weight, and in some embodiments about 1% to about 60% by weight.

[0018]

[0024] In a particular embodiment, for example, the polymer composition may contain a thermally conductive filler dispersed within a polymer matrix. To help achieve a desired balance among thermal conductivity, high fluidity, and good mechanical properties, the relative amount of the thermally conductive filler is typically in the range of about 10 to about 250 parts by weight, in some embodiments about 40 to about 250 parts by weight, in some embodiments about 60 to about 200 parts by weight, and in some embodiments about 80 parts by weight to about 190 parts by weight, based on 100 parts by weight of the polymer matrix. The thermally conductive filler may constitute, for example, about 20 wt% to about 70 wt% of the polymer composition, in some embodiments about 28 wt% to about 62 wt%, in some embodiments about 35 wt% to about 65 wt%, and in some embodiments about 40 wt% to about 60 wt%.

[0019]

[0025] Optionally, the thermally conductive filler may include materials with high intrinsic thermal conductivity. For example, the polymer composition may contain materials with an intrinsic thermal conductivity of 50 W / m·K or more, in some embodiments 100 W / m·K or more, and in some embodiments 150 W / m·K or more. Examples of such materials with high intrinsic thermal conductivity include, for example, boron nitride, aluminum nitride, magnesium silicon nitride, graphite (e.g., expanded graphite), silicon carbide, carbon nanotubes, zinc oxide, magnesium oxide, beryllium oxide, zirconium oxide, yttrium oxide, aluminum powder, and copper powder. Although such materials can be used in certain embodiments, it has been found that high thermal conductivity can be achieved without using conventional materials with high intrinsic thermal conductivity. For example, the polymer composition may generally not include fillers having an intrinsic thermal conductivity. That is, such fillers may constitute about 10 wt% or less of the polymer composition, in some embodiments about 5 wt% or less, and in some embodiments 0 wt% to about 2 wt% (e.g., 0 wt%).

[0020]

[0026] In a particular embodiment, for example, the thermally conductive filler may contain mineral particles. When used, such mineral particles typically constitute about 70 to about 250 parts by weight, in some embodiments about 75 to about 200 parts by weight, and in some embodiments about 90 to about 190 parts by weight, based on 100 parts by weight of the polymer matrix. The mineral particles may constitute, for example, about 30 wt% to about 70 wt% of the polymer composition, in some embodiments about 35 wt% to about 65 wt%, and in some embodiments about 40 wt% to about 60 wt%. The mineral particles can be formed from natural and / or synthetic silicate minerals such as talc, mica, halloysite, kaolinite, illite, montmorillonite, vermiculite, palygorskite, pyrophyllite, calcium silicate, aluminum silicate, wollastonite, etc. Talc is particularly suitable for use in the polymer composition. The shape of the particles may vary as desired, such as granular, flaky, etc. The particles typically have a median particle diameter (D50) of about 1 to about 25 micrometers, in some embodiments about 2 to about 15 micrometers, and in some embodiments about 4 to about 10 micrometers, as measured by sedimentation analysis (e.g., Sedigraph 5120). If desired, the particles may also have a high specific surface area, such as about 1 square meter / gram (m 2 / g) to about 50 m 2 / g, in some embodiments about 1.5 m 2 / g to about 25 m 2 / g, and in some embodiments about 2 m 2 / g to about 15 m 2 / g. The surface area can be determined by the physical gas adsorption (BET) method (adsorption gas is nitrogen) in accordance with DIN 66131:1993. The moisture content may also be relatively low, such as about 5% or less, in some embodiments about 3% or less, and in some embodiments about 0.1 to about 1%, when determined according to ISO 787-2:1981 at a temperature of 105 °C.

[0021]

[0027] In addition to, and / or in place of, mineral particles, the thermally conductive filler may also contain mineral fibers (also known as "whiskers"). When used, such mineral fibers typically constitute from about 10 to about 150 parts by weight, in some embodiments from about 15 to about 100 parts by weight, and in some embodiments from about 20 to about 80 parts by weight, per 100 parts by weight of the polymer matrix. The mineral fibers may constitute, for example, from about 10 wt% to about 50 wt% of the polymer composition, in some embodiments from about 15 wt% to about 45 wt%, and in some embodiments from about 20 wt% to about 40 wt%. Examples of such mineral fibers include those derived from silicates, such as neosilicates, sorosilicates, inosilicates (e.g., calcium inosilicates such as wollastonite; calcium magnesium inosilicates such as tremolite; calcium magnesium iron inosilicates such as actinolite; magnesium iron inosilicates such as anthophyllite; etc.), phyllosilicates (e.g., aluminum phyllosilicates such as palygorskite), tectosilicates, etc.; sulfates, such as calcium sulfate (e.g., dehydrated gypsum or anhydrite); mineral wool (e.g., rock or slag wool); etc. Particularly preferred are inosilicates, such as wollastonite fibers available under the trade name NYGLOS® (e.g., NYGLOS® 4W or NYGLOS® 8) from Nyco Minerals. The mineral fibers may have a median diameter of from about 1 to about 35 micrometers, in some embodiments from about 2 to about 20 micrometers, in some embodiments from about 3 to about 15 micrometers, and in some embodiments from about 7 to about 12 micrometers. The mineral fibers can also have a narrow size distribution. That is, at least about 60 volume % of the fibers, in some embodiments at least about 70 volume % of the fibers, and in some embodiments at least about 80 volume % of the fibers may have sizes within the above ranges.In addition to having the above size characteristics, the mineral fibers may have a relatively high aspect ratio (the value obtained by dividing the average length by the median diameter), which helps to further improve the mechanical properties and surface quality of the resulting polymer composition. For example, the mineral fibers may have an aspect ratio of about 2 to about 100, in some embodiments about 2 to about 50, in some embodiments about 3 to about 20, and in some embodiments about 4 to about 15. The volume average length of such mineral fibers may be, for example, in the range of about 1 to about 200 micrometers, in some embodiments about 2 to about 150 micrometers, in some embodiments about 5 to about 100 micrometers, and in some embodiments about 10 to about 50 micrometers.

[0022]

[0028] The polymer composition may also contain various other optional components to help improve its overall properties. For example, the polymer composition may contain a metal hydroxide that can effectively "lose" hydroxide ions during processing with the polymer, initiate chain scission of the polymer to reduce the molecular weight, and reduce the melt viscosity of the polymer under shear. When used, the metal hydroxide may constitute about 0.05 to about 10 parts by weight, in some embodiments about 0.1 to about 5 parts by weight, and in some embodiments about 0.2 to about 3 parts by weight per 100 parts by weight of the polymer matrix. For example, the metal hydroxide may constitute about 0.01 wt% to about 5 wt% of the polymer composition, in some embodiments about 0.05 wt% to about 4 wt%, and in some embodiments about 0.1 wt% to about 2 wt%.

[0023]

[0029] An example of a suitable metal hydroxide is of the general formula M(OH) s(In the formula, s is an oxidation state (typically 1 to 3), and M is a metal such as a transition metal, an alkali metal, an alkaline earth metal, or a main group metal). There are those having such. Examples of suitable metal hydroxides include copper (II) hydroxide (Cu(OH)2), potassium hydroxide (KOH), sodium hydroxide (NaOH), magnesium hydroxide (Mg(OH)2), calcium hydroxide (Ca(OH)2), aluminum hydroxide (Al(OH)3), and the like. Also suitable are metal alkoxide compounds capable of forming a hydroxyl functional group in the presence of a solvent such as water. Such compounds have the general formula M(OR) s (wherein s is an oxidation state (usually 1 to 3), M is a metal, and R is an alkyl). It can have such. Examples of such metal alkoxides include copper (II) ethoxide (Cu 2+ (CH3CH2O - )2), potassium ethoxide (K + (CH3CH2O - ), sodium ethoxide (Na + (CH3CH2O - ), magnesium ethoxide (Mg 2+ (CH3CH2O - )2), calcium ethoxide (Ca 2+ (CH3CH2O - )2), etc.; aluminum ethoxide (Al 3+ (CH3CH2O - )3), and the like. In certain embodiments, the metal hydroxide can be in the form of metal hydroxide particles. For example, the particles have the general formula: Al(OH) a O b(wherein 0 ≦ a ≦ 3 (for example, 1), b = (3 - a) / 2) may contain at least one aluminum hydroxide. In one particular embodiment, for example, the particles exhibit a boehmite crystal phase and the aluminum hydroxide has the formula AlO(OH) (“aluminum oxide hydroxide”). The metal hydroxide particles can be acicular, ellipsoidal, plate-like, spherical, etc. In any case, the particles typically have a median particle diameter (D50) of about 50 to about 800 nanometers, in some embodiments about 150 to about 700 nanometers, and in some embodiments about 250 to about 500 nanometers as measured by non-invasive backscattering (NIBS) technology. If desired, the particles may also have a high specific surface area of about 2 square meters / gram (m 2 / g) to about 100 m 2 / g, in some embodiments about 5 m 2 / g to about 50 m 2 / g, and in some embodiments about 10 m 2 / g to about 30 m 2 / g, etc. The surface area can be determined by the physical gas adsorption (BET) method (adsorption gas is nitrogen) in accordance with ISO 9277:2010. The moisture content may also be relatively low, such as about 5% or less, in some embodiments about 3% or less, and in some embodiments about 0.1 to about 1% when determined in accordance with ISO 787-2:1981.

[0024]

[0030] Other components that may be included in the composition include, for example, reinforcing fibers (such as glass fibers), pigments (such as black pigments), antioxidants, stabilizers, crosslinking agents, lubricants, impact resistance improvers, flow promoters, and other materials added to improve properties and processability.

[0025] II. Melt Processing

[0031] Methods of combining liquid crystal polymers with various other optional additives (such as heat conductive fillers, pigments, lubricants, etc.) can vary widely as is known in the art. For example, the materials can be fed simultaneously or sequentially into a melt processing device that dispersively mixes the materials. Batch and / or continuous melt processing techniques can be used. For example, a mixer / kneader, Banbury mixer, Farrel continuous mixer, single screw extruder, twin screw extruder, roll mill, etc. can be utilized to mix and melt process the materials. A particularly preferred melt processing device is a co-rotating twin screw extruder (e.g., Leistritz co-rotating fully intermeshing twin screw extruder). Such an extruder is provided with feed ports and exhaust ports and can perform strong distributive mixing and dispersive mixing. For example, the components can be fed into the same or different feed ports of the twin screw extruder and melt mixed to form a substantially homogeneous melt mixture. The melt mixing can be carried out at high shear force / pressure and high temperature to ensure sufficient dispersion. For example, the melt processing can be carried out at a temperature of about 150 °C to about 450 °C, and in some embodiments about 250 °C to about 400 °C. Similarly, the apparent shear rate during melt processing can range from about 100 sec -1 ~ about 10,000 sec -1 and in some embodiments about 500 sec -1 ~ about 1,500 sec -1 . Of course, other variables such as the residence time during melt processing (which is inversely proportional to the throughput rate) can also be controlled to achieve the desired degree of homogeneity.

[0026]

[0032] Optionally, one or more distributive and / or dispersive mixing elements can be used within the mixing section of the melt processing unit. Suitable distributive mixers include, for example, Saxon, Dulmage, Cavity Transfer mixer, etc. Similarly, suitable dispersive mixers include Blister ring, Leroy / Maddock, CRD mixer, etc. As is well known in the art, the intensity of mixing can be further enhanced by using pins in the barrel that cause folding and reorientation of the polymer melt, such as those used in a Buss kneader extruder, a Cavity Transfer mixer, and a Vortex Intermeshing Pin mixer. Also, the screw speed can be controlled to improve the properties of the composition. For example, in one embodiment, the screw speed can be about 400 rpm or less, such as about 200 rpm to about 350 rpm, or about 225 rpm to about 325 rpm. In one embodiment, the compounding conditions can be balanced to result in a polymer composition exhibiting improved properties. For example, compounding conditions can include a screw design that results in mild, medium, or aggressive screw conditions. For example, the system can have a mild-aggressive screw design with a single melt section downstream of the screw for gentle melting and homogenization of the distributive melt. A medium-aggressive screw design can have a more powerful melt section with a greater emphasis on more powerful dispersive elements upstream of the filler feed barrel to achieve a uniform melt. Further, the design can have another gentle mixing section downstream for mixing the filler. This section can be of low intensity but increase the shear strength of the screw and be more powerful overall than the mild-aggressive design. A very aggressive screw design can have the greatest shear strength among the three designs.The main melting section can be composed of a long array of kneading blocks having a high dispersion effect. In the downstream mixing section, a combination of distributive and intensive dispersion elements can be utilized to achieve uniform dispersion of all types of fillers. The shear strength of a very aggressive screw design can be significantly higher than the other two designs. In one embodiment, the system can include a medium to aggressive screw design at a relatively mild screw speed (e.g., from about 200 rpm to about 300 rpm).

[0027] III. Stator Coil

[0033] Parts of any suitable shape can be formed, but the polymer composition of the present invention is particularly useful for forming stator windings. Generally speaking, a stator winding includes a protective member that covers and surrounds at least a part of a conductive member. In one embodiment, for example, the protective member completely surrounds the conductive member. The winding may have a substantially circular cross-sectional dimension. Of course, any other various shapes, such as a cross-sectional shape of a polygon (e.g., a square or a rectangle), can also be used. The elongated protective member may contain multiple layers or a single layer. Examples of the conductive member can include metal wires such as copper, aluminum, stainless steel, magnesium, nickel, chromium, titanium, and alloys thereof. Due to the characteristic properties of the polymer composition, the resulting protective member can be formed relatively thin without adversely affecting its performance. The protective member may have a thickness of, for example, from about 0.01 to about 1 millimeter, in some embodiments from about 0.02 to about 0.8 millimeter, and in some embodiments from about 0.05 to about 0.4 millimeter. Similarly, the thickness of the entire stator winding may also have a thickness of, for example, from about 0.02 to about 4 millimeters, in some embodiments from about 0.05 to about 2 millimeters, and in some embodiments from about 0.1 to about 1 millimeter.

[0028]

[0034] Referring to FIG. 1, for example, a particular embodiment of a stator winding 10 is shown that includes a protective member 14 that covers and surrounds a conductive member 12 (e.g., a copper wire). Although not shown, the protective member 14 is generally elongated and can cover and surround the conductive member 12 along all or substantially all of the length of the conductive member 12. As described above, the protective member 14 may be formed from the polymer composition of the present invention. Another embodiment of the stator winding 18 is shown in FIG. 2. In this particular embodiment, the protective member contains a plurality of layers, namely an outer layer 16 and an inner layer 14, and one or both of them may be formed from the polymer composition of the present invention. For example, the outer layer 16 may be formed from the polymer composition of the present invention, while the inner layer 14 may be formed from the same or a different insulating material (e.g., a polymer material, a ceramic material, a fiber material, etc.).

[0029] IV. Stator

[0035] The stator windings of the present invention may be used in a wide range of product applications, but are particularly useful in power systems that use stators and rotors. A stator generally includes a stator body, from which a plurality of slot segments are spaced apart and extend, and an intermediate slot is defined between the slot segments. As is well known to those skilled in the art, one or more stator windings of the present invention can be disposed on the slot segment surface to form the resulting stator. For example, the winding may be disposed on a part of the slot segment. In this way, the protective member on the winding surface is disposed between the conductive material (e.g., a copper wire) and the slot segment and helps to electrically insulate the slot segment from the copper wire. In another embodiment, the winding may be adhered to the slot segment by an adhesive polymer composition that may be the same as or different from the polymer composition used to form the insulating member.

[0030]

[0036] Referring to FIG. 3, for example, an embodiment of a stator 100 containing a stator main body 110 is shown. The stator main body 110 generally has an annular shape formed by an outer peripheral wall, and this outer peripheral wall defines an annular central bore 112 for receiving a rotor (FIG. 4). The stator main body 110 contains a plurality of slot segments 114 (i.e., teeth) that are spaced apart from each other along the circumferential direction and extend axially along the longitudinal central axis of the stator main body 110, and thus extend perpendicular to the circumferential direction. The stator main body 110 and / or the slot segments 114 may be formed from a conductive material, such as any of a variety of different metals, such as aluminum, stainless steel, magnesium, nickel, chromium, copper, titanium, and alloys thereof. The slot segments 114 extend from a surface 122 between both ends of the main body 110 and project radially toward the central bore 114. Slots 116 are defined between adjacent segments 114 in the circumferential direction. As shown, the slots 116 have slot openings 118 that extend toward the bore 112. In other words, the slots 116 open toward the inside of the stator main body 110. Further, the slots 116 include at least one bend 120 in which the segment 114 extends in a direction away from the inner surface 122 of the stator main body 110. In the illustrated embodiment, the bend 120 is approximately 90°.

[0031]

[0037] As shown, the stator 100 is disposed (e.g., wound) on at least a portion of the stator main body 110 and is used to conduct current to effect relative movement of the rotor with respect to the stator 100 when used with a motor, or to effect transmission of current generated when the rotor rotates with respect to the stator 100 when used with a generator, and also includes one or more stator windings 130. In the illustrated embodiment, for example, the stator winding 130 is wound around the slot segment 114. The winding 130 wound around a given slot segment 114 passes through the slots 116 on both sides of the particular slot segment 114. If desired, a slot liner 140 can be interposed between the winding 130 and the stator main body 110 to further electrically insulate the stator main body 110 from the winding 130. The slot liner 140 can also be formed from any conventional insulating material such as a polymer material, a ceramic material, a fiber material, etc., or from the polymer composition of the present invention. For clarity and ease of illustration, only a portion of the stator main body 110 is shown in FIG. 1, and the stator 100 is shown in a partially assembled state (e.g., only some of the slots have slot liners and only some of the windings have been added).

[0032]

[0038] The overall relationship between the stator 100 and other components or aspects of a power system (e.g., a motor or a generator) is shown in FIG. 4. FIG. 4 provides a schematic view of a power system 200 according to various embodiments. The power system 200 includes a rotor 210, a stator 220 (which may generally be similar in various respects to the stator 100 described herein), a housing 230, and a shaft 240. The power system 200 may be configured as a generator or as a motor. In various embodiments, the power system 200 may be configured for alternating current (AC) operation. Further, the power system 200 may be configured for direct current (DC) operation in various embodiments. Generally, the rotor 210 is disposed within the bore 222 or the central opening of the stator 220 and is configured to rotate relative to the stator 220. When the power system 200 operates as a motor, a current passing through the windings of the rotor 210 and / or the windings of the stator 220 causes the rotor 210 to rotate relative to the stator 220. When the power system 200 operates as a generator, rotation of the rotor 210 relative to the stator 220 generates a current within the windings of the rotor 210 and / or the stator, which may be output. This current may be output by the generator for use by one or more external (e.g., external to the power system 200) devices and / or systems. The housing 230 in the illustrated embodiment supports and attaches the stator 220 and helps to maintain the stator 220 in a stationary position while the rotor 210 rotates. The housing 230 may also provide attachment features, such as one or more bearings, for attaching the rotor 210. Further, the illustrated housing 230 is configured to function as a heat sink or otherwise for heat transfer away from the stator 220. The shaft 240 is operably coupled to the rotor 210 and is configured to rotate with the rotor 210. The shaft 240 is configured to facilitate conversion of mechanical power (e.g., rotation) to electrical power (e.g., current) or vice versa.When the power system 200 operates as a generator, the shaft 240 is used to provide a rotational input to the power system 200 that is used to generate an electric current. When the power system 200 operates as a motor, the shaft 240 is used to output a rotation that is used by a system coupled to the power system 200.

[0033]

[0039] The stator core and stator / rotor system may be used in a wide range of product applications, but are particularly beneficial in use in an electric motor of an electric vehicle such as a battery-powered electric vehicle, a fuel cell-powered electric vehicle, a plug-in hybrid electric vehicle (PHEV), a mild hybrid electric vehicle (MHEV), a full hybrid electric vehicle (FHEV). Referring to FIG. 5, for example, one embodiment of an electric vehicle 12 including a powertrain 10 is shown. The powertrain 10 contains one or more electric machines 14 connected to a transmission 16, which in turn is mechanically connected to a drive shaft 12 and drive wheels 22. Although not at all essential, in this particular embodiment, the transmission 16 is also connected to an engine 18. However, the description herein is equally applicable to a pure electric vehicle. The electric machine 14 may be an electric motor containing a stator / rotor system that provides propulsion and deceleration capabilities. The powertrain 110 also includes a propulsion source such as a battery assembly 24 that stores and supplies the energy used by the electric machine 14. The battery assembly 24 typically supplies a high voltage current output (e.g., a direct current voltage of about 400 volts to about 800 volts) from one or more battery cell arrays that may include one or more battery cells.

[0034]

[0056] The power train 10 may also contain at least one power electronics module 26 that is connected to a battery assembly 24 (commonly also referred to as a battery pack) and may contain a power converter (e.g., a converter, etc., and combinations thereof). The power electronics module 26 is typically electrically connected to the electromechanical device 14 and provides the ability to transfer electrical energy bidirectionally between the battery assembly 24 and the electromechanical device 14. For example, while the battery assembly 24 may supply a DC voltage, the electromechanical device 14 may require a three-phase AC voltage to function. The power electronics module 26 can convert the DC voltage into the three-phase AC voltage required by the electromechanical device 14. In the regenerative mode, the power electronics module 26 can convert the three-phase AC voltage from the electromechanical device 14 functioning as a generator into the DC voltage required by the battery assembly 24. The battery assembly 24 can also supply energy to other vehicle electrical systems. For example, the power train may use a DC / DC converter module 28 that converts the high-voltage DC output from the battery assembly 24 into a low-voltage DC power supply suitable for other vehicle loads such as a compressor or an electric heater. In a typical vehicle, the low-voltage system is electrically connected to an auxiliary battery (e.g., a 12V battery). There may also be a battery energy control module (BECM) 33 that communicates with the battery assembly 24 and may include an electronic monitoring system that functions as a controller for the battery assembly 24 and manages the temperature and state of charge of each battery cell. The battery assembly 24 may also have a temperature sensor 31 such as a thermistor or other thermometer. The temperature sensor 31 may communicate with the BECM 33 to provide temperature data regarding the battery assembly 24. The temperature sensor 31 may also be disposed on or near the battery cells within the traction battery 24. It is also contemplated that two or more temperature sensors 31 may be used to monitor the temperature of the battery cells.

[0035]

[0057] The battery assembly 24 can be recharged by an external power source 36 such as an electrical outlet. The external power source 36 may be electrically connected to an electric vehicle supply equipment (EVSE) that regulates and manages the transfer of electrical energy between the power source 36 and the vehicle 12. The EVSE 38 may have a charging connector 40 for insertion into the charging port 34 of the vehicle 12. The charging port 34 may be any type of port configured to transfer power from the EVSE 38 to the vehicle 12 and may be electrically connected to a charger or an in-vehicle power conversion module 32. The power conversion module 32 can adjust the power supplied from the EVSE 38 and supply appropriate voltage and current levels to the battery assembly 24. The power conversion module 32 can cooperate with the EVSE 38 to regulate the power supply to the vehicle 12.

Example

[0036] Test Method

[0058] Thermal conductivity As is known in the art, the thermal diffusivity of a sample in various directions (in-plane, cross-plane, out-of-plane) can first be determined based on the laser flash method in accordance with ASTM E1461-13(2022). The thermal conductivity (in-plane direction, cross-plane direction, and out-of-plane direction) can then be calculated according to the following equation. Thermal conductivity (W / m·K) = Cp × ρ × α (where Cp is the specific heat capacity of the sample (J / kgK), ρ is the intrinsic density of the sample determined in accordance with ISO 11831-1:2019 (Method A) (kg / m 3 ), α is the measured thermal diffusivity (m 2 / s))

[0059] Melt viscosity The melt viscosity (Pa·s) is measured using a Dynisco LCR7001 capillary rheometer at a shear rate of 1,000 s -1It can be determined in accordance with ISO 11443:2021. The diameter of the rheometer orifice (die) can be 1 mm, the length can be 20 mm, the L / D ratio can be 20.1, and the inlet angle can be 180°. The diameter of the barrel can be 9.55 mm + 0.005 mm, and the length of the rod can be 233.4 mm. The melt viscosity is typically determined at a temperature 15 °C higher than the melt temperature of the polymer and / or composition, for example, about 350 °C.

[0037]

[0060] Melt temperature The melt temperature (“Tm”) can be determined by differential scanning calorimetry (“DSC”) as is known in the art. The melt temperature is the differential scanning calorimetry (DSC) peak melt temperature determined in accordance with ISO test number 11357-3:2018. In the DSC procedure using DSC measurements performed on a TA Q2000 instrument, the sample was heated and cooled at 20 °C per minute as described in ISO standard 10350.

[0038]

[0061] Tensile modulus, tensile breaking stress, and tensile breaking strain Tensile properties can be tested in accordance with ISO 527:2019 (technically equivalent to ASTM D638-14). Measurements of modulus and strength can be performed on the same test strip sample having a length of 80 mm, a thickness of 10 mm, and a width of 4 mm. The test temperature can be 23 °C, and the test speed can be 5 mm / min for tensile strength and tensile breaking strain, and 1 mm / min for tensile modulus.

[0039]

[0062] Flexural modulus and flexural stress Flexural properties can be tested in accordance with ISO 178:2019 (technically equivalent to ASTM D790-10). This test can be performed with a support span of 64 mm. The test can be performed on the central part of an uncut ISO 3167 multi-purpose bar. The test temperature can be 23 °C, and the test speed can be 2 mm / min.

[0040]

[0063] Charpy impact strength The Charpy properties can be tested in accordance with ISO 179-1:2010 (technically equivalent to ASTM D256-10, Method B). This test can be carried out using type 1 specimen sizes (length 80 mm, width 10 mm, thickness 4 mm). The specimens can be cut out from the center of the multi-purpose specimens using a single-tooth milling cutter. The test temperature may be 23 °C. For the notched impact strength, this test can be carried out using type A notches (bottom radius 0.25 mm) and type 1 specimen sizes (length 80 mm, width 10 mm, and thickness 4 mm).

[0041]

[0064] Comparative Tracking Index (「CTI」) The Comparative Tracking Index (CTI) is determined in accordance with the international standard IEC 60112-2003 and can provide a quantitative indicator of the ability of a composition to function as an electrical insulating material under wet and / or contaminated conditions. When determining the CTI evaluation of a composition, two electrodes are placed on the molded specimen. Then, while dropping a 0.1% aqueous ammonium chloride solution onto the specimen, a voltage difference is provided between the electrodes. During the test of 50 drops, the maximum voltage that five specimens can withstand without failure is determined. The test voltage ranges from 100 to 600 V in 25 V increments. The numerical value of the voltage at which the electrolyte fails after 50 drops is the "Comparative Tracking Index". This value serves as an indicator of the relative tracking resistance of the material. According to UL746A, a nominal partial thickness of 3 mm is considered representative of the performance at other thicknesses.

[0042] Examples 1 - 2

[0065] The following two commercially available samples were compounded and injection molded for use in the stator winding.

[0043]

Table 1

[0044]

[0066] LCP1 is formed from 73% HBA and 27% HNA. LCP2 is considered to be formed from 50% HBA, 25% BP, and 25% TA. Samples were tested for the mechanical properties, thermal properties, and thermal conductivity described herein. The results are described below.

[0045]

Table 2

[0046] Example 3

[0067] The following samples were compounded and injection molded for use in stator windings.

[0047]

Table 3

[0048]

[0068] LCP3 is formed from 43% HBA, 20% NDA, 9% TA, and 28% HQ. Samples were tested for the mechanical properties, thermal properties, and thermal conductivity described herein. The results are described below.

[0049]

Table 4

[0050]

[0069] These and other modifications and variations of the present invention can be made by those skilled in the art without departing from the spirit and scope of the invention. Furthermore, it should be understood that aspects of the various embodiments can be wholly or partially interchangeable. Additionally, those skilled in the art will understand that the foregoing description is merely exemplary and is not intended to limit the invention as further described in the appended claims.

Claims

1. A stator winding comprising a protective member that covers and surrounds at least a part of a conductive member, wherein the protective member includes a polymer composition, the polymer composition includes a polymer matrix including a thermotropic liquid crystal polymer, and further the polymer composition has a melt viscosity of about 300 Pa·s or less measured according to ISO 11443:2021 at a shear rate of 1,000 s －１ , and at a temperature about 15 °C higher than the melting temperature of the composition, and a load deflection temperature of about 170 °C or higher measured with a load of 1.8 MPa according to ISO 75:2013.

2. The stator winding according to claim 1, wherein the polymer composition exhibits a melting temperature of about 250 °C to about 440 °C.

3. The stator winding according to claim 1, wherein the thermotropic liquid crystal polymer contains repeating units derived from one or more aromatic dicarboxylic acids, one or more aromatic hydroxycarboxylic acids, or a combination thereof.

4. The stator winding according to claim 3, wherein the aromatic hydroxycarboxylic acid includes 4-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, or a combination thereof.

5. The stator winding according to claim 4, wherein the aromatic dicarboxylic acid includes terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, or a combination thereof.

6. The stator winding according to claim 3, wherein the liquid crystal polymer further contains repeating units derived from one or more aromatic diols.

7. The stator winding according to claim 6, wherein the aromatic diol includes hydroquinone, 4,4'-biphenol, or a combination thereof.

8. The stator winding according to claim 1, wherein the thermotropic liquid crystal polymer is wholly aromatic.

9. The stator winding according to claim 1, wherein the thermotropic liquid crystal polymer contains repeating units derived from naphthenic hydroxycarboxylic acids and / or dicarboxylic acids in an amount of about 10 mol% or more.

10. The stator winding according to claim 1, wherein the polymer composition exhibits an in-plane thermal conductivity of about 2 W / m·K or more as measured according to ASTM E1461-13 (2022).

11. The stator winding according to claim 1, wherein the polymer composition exhibits a cross-plane thermal conductivity of about 0.8 W / m·K or more as measured according to ASTM E1461-13 (2022).

12. The stator winding according to claim 1, wherein the polymer composition exhibits an in-plane thermal conductivity of about 4 to about 8 W / m·K as measured according to ASTM E1461-13 (2022).

13. The stator winding according to claim 1, wherein the polymer composition exhibits an insulation resistance of about 10 kV / mm or more as measured according to IEC 60234-1:2013.

14. The stator winding according to claim 1, wherein the polymer composition further includes a thermally conductive filler.

15. The stator winding according to claim 14, wherein the heat conductive filler contains mineral particles.

16. The stator winding according to claim 15, wherein the mineral particles contain talc.

17. The stator winding according to claim 15, wherein the mineral particles constitute about 70 to about 250 parts by weight with respect to 100 parts by weight of the polymer matrix.

18. The mineral particles have a median diameter of about 1 to about 25 micrometers, a specific surface area of about 1 to about 50 m ２ / g measured in accordance with DIN 66131:1993, and / or a water content of about 5% or less measured in accordance with ISO 787-2:1981 at a temperature of 105°C, the stator winding according to claim 15.

19. The stator winding according to claim 14, wherein the heat conductive filler contains mineral fibers.

20. The stator winding according to claim 19, wherein the mineral fibers contain wollastonite.

21. The stator winding according to claim 19, wherein the mineral fibers constitute about 10 to about 150 parts by weight with respect to 100 parts by weight of the polymer matrix.

22. The stator winding according to claim 1, wherein the polymer composition does not contain a filler having an intrinsic thermal conductivity of 100 W / m·K or more.

23. The stator winding according to claim 1, wherein the polymer composition exhibits a comparative tracking index of about 170 volts or more as measured in accordance with IEC 60112:2003 at a thickness of 3 millimeters.

24. The stator winding according to claim 1, wherein the protective layer includes a single layer formed from the polymer composition.

25. The stator winding according to claim 1, wherein the conductive member includes a copper wire.

26. The stator winding according to claim 1, wherein the winding has a substantially circular cross-sectional shape.

27. The stator winding according to claim 1, wherein the protective member has a thickness of about 0.01 to about 1 millimeter.

28. A stator including a stator main body, from which a plurality of slot segments are spaced apart and extend, and an intermediate slot is defined between the slot segments, wherein the stator winding according to any one of claims 1 to 27 is disposed on at least one of the slot segments.

29. The stator according to claim 28, wherein the stator winding is wound around at least one of the slot segments.

30. The stator according to claim 28, wherein the stator main body has an annular shape and defines a central bore for receiving a rotor.

31. The stator according to claim 30, wherein the slot segments are spaced apart in the circumferential direction and project radially toward the central bore.

32. A power system comprising a stator according to claim 28 and a rotor.

33. An electric vehicle comprising a power train including the power system according to claim 32 and a transmission connected to a propulsion source via at least one power electronics module.

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