Stator core for a power system

Abstract

There is provided a stator core that contains a stator main portion, from which a plurality of slot segments are spaced apart and extend, a plurality of intermediate slots are defined between the slot segments, and an insulating member is disposed in at least one of the plurality of intermediate slots. The insulating member contains 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.

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 that contains an electric propulsion source (e.g., a battery) and a transmission. The electric motors used in such vehicles generally contain a power system that includes 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 core in which a plurality of slots are formed. A plurality of stator wires (windings) are formed in the slots of the stator core in a predetermined polyphase (e.g., 3-phase or 6-phase) winding pattern. The slot segments are typically insulated from the core by a sheet-type insulator. One representative sheet-type insulator is Nomex (trademark) paper (commonly known as a "slot liner"). While this material is somewhat beneficial, it is often difficult to incorporate into the small slots of the stator core. Further, Nomex (trademark) paper is expensive and lacks various beneficial properties that could improve ease of manufacture and the overall performance of the stator, such as good heat resistance, high fluidity, and high thermal conductivity. Therefore, there is a need for improvement in the stator core used in the power systems of electric vehicles.

Summary of the Invention

Means for Solving the Problems

[0002] According to an embodiment of the present invention, a stator core is disclosed that includes a stator main body, from which a plurality of slot segments are spaced apart and extend, and a plurality of intermediate slots are defined between the slot segments. An insulating member is disposed in at least one of the plurality of intermediate slots. The insulating member contains 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 heat deflection temperature of about 170°C or higher.

[0003]

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

[0004] The complete and enabling disclosure of the present invention, including the best mode for those skilled in the art, is described in more detail in the remainder of this specification, including reference to the accompanying drawings.

Brief Description of the Drawings

[0004]

Figure 1a

[0005] FIG. 1a is a view showing an embodiment of the stator core of the present invention before contact with the insulating member.

Figure 1b

Figure 2a

[0006] FIG. 2a is a view showing an embodiment of the stator core of the present invention after contact with the insulating member (e.g., overmolding).

Figure 2b

Figure 2c

Figure 3a

[0007] FIG. 3a is a view showing an embodiment of a stator containing the stator core of FIGS. 2a and 2b in combination with a stator winding.

Figure 3b

Figure 3c

Figure 4

[0008] FIG. 7 is a diagram of an embodiment of a power system in which the stator of FIG. 3 can be used.

Figure 5

[0009] FIG. 11 is a diagram showing an embodiment of an electric vehicle in which the stator core of the present invention can be used.

DETAILED DESCRIPTION OF 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 core for use in a power system of an electric vehicle. The stator core includes a stator main body that contains a plurality of slot segments that are spaced apart and extend in the axial direction, and a plurality of intermediate slots are defined between the slot segments. An insulating member is disposed in at least a part of the slots. In particular, the insulating member contains a polymer composition including a liquid crystal polymer and exhibits a combination of high fluidity 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 about 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. 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 can exhibit 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 when measured in accordance with, for example, IEC 60234-1:2013. The insulating 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 when measured in accordance with, for example, IEC 60112:2003 at a thickness of 3 millimeters.

[0008]

[0014] Despite having the above properties, the polymer composition can maintain high strength, thereby providing improved flexibility and impact resistance. The polymer composition can have, for example, a tensile break 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 break 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 providing 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 wt% to 100 wt% of the polymer matrix, about 70 wt% to 100 wt% in some embodiments, and about 90 wt% to 100 wt% (e.g., 100 wt%) in some embodiments. The liquid crystal polymer generally has a rod-like structure and is classified as "thermotropic" as long as it can exhibit crystalline behavior in the molten state (e.g., thermotropic nematic state). Such polymers typically have a DTUL value of about 200 °C to about 340 °C, about 210 °C to about 300 °C in some embodiments, and about 220 °C to about 280 °C when measured at a load of 1.8 MPa in accordance with ISO 75-2:2013. The polymer can also have a relatively high melting temperature of about 250 °C to about 440 °C, about 260 °C to about 400 °C in some embodiments, and about 300 °C to about 380 °C in some embodiments. The polymer can be formed from one or more repeating units, as is known in the art. The liquid crystal polymer is, for example, generally represented by the following formula (I):

[0010]

Chemical formula

[0011] (wherein, Ring B may contain one or more aromatic ester repeating units represented by 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 linked to a substituted or unsubstituted 5- or 6-membered aryl group (e.g., 4,4-biphenylene), and Y1 and Y2 are independently O, C(O), NH, C(O)HN, or NHC(O).

[0012]

[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.

[0013]

[0018] The 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., and their alkyl, alkoxy, aryl, and halogen substituents, and combinations thereof can be used. 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, about 25 mol% to about 75 mol% in some embodiments, and about 30 mol% to about 70 mol% in some embodiments.

[0014]

[0019] The aromatic dicarboxylic acid repeating unit is also 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., and 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 units derived from the aromatic dicarboxylic acid (e.g., IA, TA, and / or NDA) typically constitute about 1 mol% to about 50 mol% of the polymer, about 5 mol% to about 40 mol% in some embodiments, and about 10 mol% to about 35 mol% in some embodiments.

[0015]

[0020] Other repeating units can 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 can 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, in some embodiments from about 2 mol% to about 35 mol%, and in some embodiments from about 5 mol% to about 30 mol%. 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.) can 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, in some embodiments from about 0.5 mol% to about 15 mol%, and in some embodiments from about 1 mol% to about 10 mol%. 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 "fully aromatic" in that it has no repeating units derived from non-aromatic (e.g., aliphatic or alicyclic) monomers.

[0016]

[0021] Although not necessary, 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, in some embodiments at least about 12 mol%, in some embodiments at least about 15 mol%, in some embodiments from about 15 mol% to about 50 mol%, and in some embodiments from 16 mol% to about 30 mol%. 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 about 20 mol% to about 60 mol%, in some embodiments about 25 mol% to about 55 mol%, and in some embodiments about 30 mol% to about 50 mol%. The polymer may also contain aromatic dicarboxylic acids (e.g., IA and / or TA) in an amount of about 1 mol% to about 15 mol% and / or aromatic diols (e.g., BP and / or HQ) in an amount of 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) may be at most about 10 mol% of the polymer, in some embodiments at most about 8 mol%, and in some embodiments from about 1 mol% to about 6 mol%.

[0017]

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

[0023] In certain embodiments, the polymer composition may be entirely formed from the polymer matrix (i.e., 100 wt%). 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 wt% to about 80 wt% of the polymer composition, in some embodiments about 0.5 wt% to about 70 wt%, and in some embodiments about 1 wt% to about 60 wt%.

[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 having a high intrinsic thermal conductivity. For example, the polymer composition may contain materials having an intrinsic thermal conductivity of 50 W / m·K or higher, in some embodiments 100 W / m·K or higher, and in some embodiments 150 W / m·K or higher. Examples of such materials having a 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 having a 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 in accordance with 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-described 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 from about 2 to about 100, in some embodiments from about 2 to about 50, in some embodiments from about 3 to about 20, and in some embodiments from about 4 to about 15. The volume average length of such mineral fibers may be, for example, in the range of from about 1 to about 200 micrometers, in some embodiments from about 2 to about 150 micrometers, in some embodiments from about 5 to about 100 micrometers, and in some embodiments from 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 from about 0.05 to about 10 parts by weight, in some embodiments from about 0.1 to about 5 parts by weight, and in some embodiments from about 0.2 to about 3 parts by weight, based on 100 parts by weight of the polymer matrix. For example, the metal hydroxide may constitute from about 0.01 wt% to about 5 wt% of the polymer composition, in some embodiments from about 0.05 wt% to about 4 wt%, and in some embodiments from about 0.1 wt% to about 2 wt%.

[0023]

[0029] An example of a suitable metal hydroxide has the general formula M(OH) s(wherein 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). 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 alkyl). 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 - ), 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 such as 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. 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. II. Melt Processing

[0031] Methods of combining liquid crystal polymers with various other optional additives (e.g., thermal conductivity 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, mixers / kneaders, Banbury mixers, Farrel continuous mixers, single screw extruders, twin screw extruders, roll mills, etc. can be utilized to mix and melt process the materials. A particularly suitable melt processing device is a co-rotating twin screw extruder (e.g., Leistritz co-rotating fully intermeshing twin screw extruder). Such extruders are provided with feed ports and vent 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 to about 10,000 sec -1 and in some embodiments from about 500 sec -1 to 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.

[0025]

[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 yield a polymer composition with improved properties. For example, compounding conditions can include screw designs that result in mild, medium, or aggressive screw conditions. For example, the system can have a mild-aggressive screw design with a single melting section downstream of the screw for gentle melting and homogenization of the distributive melt. A medium-aggressive screw design can have a more powerful melting section that emphasizes 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 have a 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 highest shear strength among the three designs.The main melting section can be composed of a long array of kneading blocks with a high dispersion effect. In the downstream mixing section, a combination of distributive and intensive dispersion elements can be utilized to achieve a uniform dispersion of all types of fillers. The shear strength of a very aggressive screw design can be significantly higher than that of the other two designs. In one embodiment, the system can include a medium to aggressive screw design with a relatively mild screw speed (e.g., from about 200 rpm to about 300 rpm). III. Stator Core

[0033] The stator core generally includes a stator main body, and a plurality of slot segments are spaced apart from the stator main body and extend therefrom, and a plurality of intermediate slots are defined between the slot segments. Referring to, for example, FIG. 1a, an embodiment of the stator main body 2 of the stator core 1 is shown in more detail. The stator main body 2 generally has an annular shape formed by an outer peripheral wall, and this outer peripheral wall defines an annular central bore for receiving the rotor. The stator main body 2 contains a plurality of slot segments 3 (i.e., teeth) that are spaced apart from each other along the circumferential direction U and extend in the axial direction A along the longitudinal central axis M of the stator main body 2, and thus extend perpendicular to the circumferential direction U. The radial direction R also extends perpendicularly from the longitudinal central axis M, and thus extends orthogonally to both the axial direction A and the circumferential direction U. The stator main body 2 and / or the slot segments 3 may be formed of a conductive material, for example, any of various different metals, such as aluminum, stainless steel, magnesium, nickel, chromium, copper, titanium, and their alloys. As shown, the slot segments 3 extend between both ends of the main body 2 and project radially toward the central bore. A slot 13 containing an intermediate space 4 is defined between the segments 3 adjacent to each other in the circumferential direction. Referring to FIG. 1b, two slot segments 3 arranged adjacent to each other in the circumferential direction U are shown. At the end away from the stator main body 2, each slot segment 3 includes extensions 12a, 12b that project from the slot segment 3 in the circumferential direction U and in the opposite direction of the circumferential direction U, whereby in all cases, two extensions 12a, 12b at positions facing each other in the circumferential direction U of two adjacent slot segments 3 in the circumferential direction U partially form the boundary of the intermediate space 4 while forming the slot 13 radially inward.

[0026]

[0034] As described above, the polymer composition of the present invention is used for an insulating member disposed within one or more slots of a stator core. The insulating member may be relatively thin in nature, for example, having a thickness of from about 0.01 to about 4 millimeters, in some embodiments from about 0.1 to about 2 millimeters, and in some embodiments from about 0.2 to about 1 millimeter.

[0027]

[0035] The ability to form such thin insulating members for use in a stator can be obtained in a variety of ways. In one embodiment, for example, the polymer composition may simply be used to form individual insulating members that are inserted into one or more individual slots. However, in another embodiment, the polymer composition may simply be molded (i.e., “overmolded”) onto the stator body surface, thereby forming an insulating member that contains portions disposed within one or more slots. Referring to FIGS. 2a, 2b, and 2c, an overmolded and integrally formed insulating member containing a portion K1 disposed within slot 13 is shown. If desired, prior to overmolding, a first mask 6a, such as a plate-like metal insert 17a, may first be introduced into an intermediate slot 4 between slot segments 3. More specifically, the mask 6a may cover a surface portion 7, be introduced at the radially outer end 10a of each intermediate slot 13, and may completely fill each radially outer end 10a.

[0028]

[0036] Suitable molding techniques include, for example, injection molding, low-pressure injection molding, extrusion compression molding, gas injection molding, foam injection molding, low-pressure gas injection molding, low-pressure foam injection molding, gas extrusion compression molding, foam extrusion compression molding, extrusion molding, foam extrusion molding, compression molding, foam compression molding, gas compression molding, etc. For example, an injection molding system including a mold into which the polymer composition can be injected can be used. The time in the injector can be controlled and optimized so that the polymer matrix does not solidify prematurely. When the cycle time is reached and the barrel is full for ejection, a piston can be used to inject the composition into the mold cavity. A compression molding system can also be used. Similar to injection molding, the molding of the polymer composition into the desired article is also carried out in a mold. The composition may be placed into the compression mold using any known technique, such as being picked up by an automated robotic arm. The temperature of the mold can be maintained above the solidification temperature of the polymer composition for a desired time to enable solidification. The molded article can then be solidified by bringing it to a temperature below the melting temperature. The resulting product may be demolded. To achieve sufficient bonding and enhance the productivity of the overall process, the cycle time of each molding process may be adjusted according to the polymer composition.

[0029]

[0037] Regardless of the process used, as is well known to those skilled in the art, one or more stator windings (e.g., copper wires) can be disposed on the slot segment surface to form the resulting stator. For example, when used with a motor, the windings may be disposed in a portion of the slot segment and used to conduct current to enable relative movement of the rotor with respect to the stator. In this way, an insulating member, or a portion of the insulating member, is disposed between the winding and the slot segment to electrically insulate the slot segment from the winding. 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. Referring, for example, to FIGS. 3a, 3b, and 3c, a stator winding 5 (e.g., a copper wire) is shown disposed on the surface of a slot segment 3 to form a stator.

[0030]

[0038] As described above, a rotor (not shown) is disposed within the central bore of the stator core 1 and is configured to rotate relative to the stator. In this way, the current passing through the windings of the rotor and / or stator can drive the rotation of the rotor relative to the stator. A shaft (not shown) may also be operably coupled to the rotor and configured to rotate with the rotor. The shaft is configured to facilitate the conversion of mechanical power (e.g., rotation) to electrical power (e.g., current), or vice versa. 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 diagram 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 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, the 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, the 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 can 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 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.Furthermore, the housing 230 shown functions as a heat sink or, alternatively, is configured 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., electric 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.

[0031]

[0039] The stator and the power 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, an 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 having a voltage of about 400 volts to about 800 volts) from one or more battery cell arrays that may include one or more battery cells.

[0032]

[0056] The power train 10 may also be connected to a battery assembly 24 (commonly also referred to as a battery pack) and may contain at least one power electronics module 26 that 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 source 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.

[0033]

[0057] The battery assembly 24 can be recharged by an external power source 36 such as an 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

[0034] 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). Then, the thermal conductivity (in-plane, cross-plane, and out-of-plane) can be calculated according to the following formula. Thermal conductivity (W / m·K) = Cp × ρ × α (where Cp is the specific heat capacity of the sample (J / kgK), ρ is the bulk 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.

[0035]

[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.

[0036]

[0061] Tensile modulus, tensile break stress, and tensile break 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 made 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 break strain, and 1 mm / min for tensile modulus.

[0037]

[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 portion of an uncut ISO 3167 multi-purpose bar. The test temperature can be 23 °C, and the test speed can be 2 mm / min.

[0038]

[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 multipurpose 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).

[0039]

[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 dropping 50 times, 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 is dropped 50 times and failure occurs 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.

[0040] Examples 1 - 2

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

[0041]

Table 1

[0042]

[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.

[0043]

Table 2

[0044] Example 3

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

[0045]

Table 3

[0046]

[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.

[0047]

Table 4

[0048]

[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 present invention. Further, it should be understood that aspects of the various embodiments may 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 core, comprising: A stator main body, from which a plurality of slot segments arranged at intervals extend, and a plurality of intermediate slots are defined between the slot segments; and An insulating member disposed in at least one of the intermediate slots; The insulating member contains a polymer composition, the polymer composition includes a polymer matrix containing a thermotropic liquid crystal polymer, and further the polymer composition has a melt viscosity of about 300 Pa·s or less as 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 shows a load deflection temperature of about 170 °C or higher as measured with a load of 1.8 MPa according to ISO 75:2013, The stator core.

2. The stator core according to claim 1, wherein the stator main body has an annular shape and defines a central bore for receiving a rotor.

3. The stator core according to claim 2, wherein the slot segments are arranged at intervals in the circumferential direction and protrude radially toward the central bore.

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

5. The stator core 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.

6. The stator core according to claim 5, wherein the aromatic hydroxycarboxylic acid includes 4-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, or a combination thereof.

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

8. The stator core according to claim 5, wherein the liquid crystal polymer further contains repeating units derived from one or more aromatic diols.

9. The stator core according to claim 8, wherein the aromatic diol includes hydroquinone, 4,4'-biphenol, or a combination thereof.

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

11. The stator core 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.

12. The stator core 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).

13. The stator core 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).

14. The stator core 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).

15. The stator core 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.

16. The stator core according to claim 1, wherein the polymer composition further comprises a thermally conductive filler.

17. The stator core according to claim 16, wherein the thermally conductive filler comprises mineral particles.

18. The stator core according to claim 17, wherein the mineral particles comprise talc.

19. The stator core according to claim 17, wherein the mineral particles constitute about 70 to about 250 parts by weight based on 100 parts by weight of the polymer matrix.

20. The mineral particles have a median diameter of about 1 to about 25 micrometers, a specific surface area of about 1 to 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 core according to claim 17.

21. The stator core according to claim 16, wherein the thermally conductive filler comprises mineral fibers.

22. The stator core according to claim 21, wherein the mineral fibers comprise wollastonite.

23. The stator core according to claim 21, wherein the mineral fibers constitute about 10 to about 150 parts by weight based on 100 parts by weight of the polymer matrix.

24. The stator core 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.

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

26. The stator core according to claim 1, wherein the insulating member is overmolded on the surface of the stator main body, whereby at least a part of the insulating member is disposed in at least a part of the intermediate slot.

27. A stator comprising the stator core according to any one of claims 1 to 26 and at least one winding disposed on the surface of the slot segment of the stator core, wherein an insulating member is disposed between the winding and the slot segment.

28. A power system comprising a stator according to claim 27 and a rotor.

29. An electric vehicle comprising a power train including at least one electric propulsion source and a transmission connected to the propulsion source via at least one power electronics module, the electric vehicle comprising a stator core according to any one of claims 1 to 26.

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