COIL CONSTRUCTION FOR AUTOMOTIVE WIRELESS CHARGING

Background

[0001] Wireless charging uses magnetic fields to transfer power from a transmitter coil of a charging station to a receiver coil of the device that is being charged. These coils are often constructed with copper wire. However, copper coils may be unsuitable for high power wireless charging applications because copper loses mechanical strength at high temperatures, leading to failure of the wireless charging system. Furthermore, copper coils for high power charging applications are heavy and bulky, making them unsuitable for automotive applications where vehicle weight and aerodynamics are important.

Summary

[0002] In broad summary, herein are disclosed coils, assemblies and systems for inductive charging. A coil for inductive charging can include wire wound in a number of turns and comprising at least one strand of a metal matrix composite material. The metal matrix composite material can comprise a metal with a plurality of non-metallic fibers embedded therein. These and other aspects will be apparent from the detailed description below. In no event, however, should this broad summary be construed to limit the claimable subject matter, whether such subject matter is presented in claims in the application as initially filed or in claims that are amended or otherwise presented in prosecution.

Brief Description of the Drawings

[0003] FIG. 1 is a diagram of a wireless power transfer system in an automotive application according to an example embodiment.

[0004] FIG. 2 illustrates a rectangular coil that can be used in wireless power transfer (WPT) applications in accordance with some embodiments.

[0005] FIG. 3 illustrates a circular coil that can be used in WPT applications in accordance with some embodiments.

[0006] FIG. 4A illustrates a coil having four turns in one layer in accordance with some embodiments.

[0007] FIG. 4B illustrates a coil having six turns in two layers in accordance with some embodiments.

[0008] FIG. 4C illustrates a coil having three turns in three layers in accordance with some embodiments. [0009] FIG. 5 is a cross-sectional view of a strand of the metal matrix composite material in accordance with some embodiments.

[0010] FIG. 6 illustrates a circular wire that includes strands of metal alloy and strands of the metal matrix composite material, with at least some of the strands including individual strand insulation according to some embodiments.

[0011] FIG. 7 illustrates a wire in which the number of strands of the metal alloy is greater than the number of strands of the metal matrix composite material according to some embodiments.

[0012] FIG. 8 illustrates a wire in which the number of strands of the metal alloy is less than the number of strands of the metal matrix composite material according to some embodiments.

[0013] FIG. 9 illustrates a wire in a rectangular configuration and comprised only of strands of the metal matrix composite material according to some embodiments.

[0014] FIG. 10 illustrates a wire in a rectangular configuration comprised only of strands of the metal alloy according to some embodiments.

[0015] FIG. 11 illustrates a wire that is comprised of Aluminum Conductor Composite

Reinforced (ACCR) according to some embodiments.

[0016] FIG. 12 illustrates a coil fabricated using copper or an aluminum matrix composite core according to some embodiments.

[0017] FIG. 13 illustrates measured power transfer efficiency when the transmitter coil and the receiver coil are comprised of various materials according to some embodiments.

[0018] FIG. 14 illustrates an example test setup according to some embodiments.

[0019] FIG. 15 illustrates electromagnetic modeling of coils according to some embodiments.

[0020] FIG. 16 illustrates simulated power transfer efficiency when the transmitter coil and the receiver coil are comprised of various materials according to some embodiments.

[0021] FIG. 17 illustrates a coil assembly for wireless charging of an electrical vehicle according to embodiments.

[0022] FIG. 18 illustrates a coil assembly that includes transmitter coil according to some embodiments.

Detailed Description

[0023] In the following description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments which may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural, logical and electrical changes may be made without departing from the scope of the present invention. The following description of example embodiments is, therefore, not to be taken in a limited sense, and the scope of the present invention is defined by the appended claims.

[0024] Wireless power transfer (WPT) uses magnetic fields to transfer power from a transmitter coil of a charging station to a receiver coil of the device that is being charged. FIG. 1 is a diagram of a WPT system 100 in an automotive application according to an example embodiment. In automotive applications, the transmitter coil 102 may be embedded in the ground at a

predesignated location for stationary WPT, or on a road surface for WPT while electric vehicles (EVs) are in motion, for example. An EV 104 will include a receiver coil 106, usually attached to the EV 104 undercarriage although embodiments are not limited thereto. The transmitter coil 102 and the receiver coil 106 may have dimensions in accordance with standards of the Society of Automotive Engineers (SAE) family of standards. These and other dimensions are described later herein. The transmitter coil 102 and the receiver coil 106 must be protected from environmental elements, including but not limited to excessive heat, precipitation, salt, vibrations, impacts, etc.

[0025] Wireless charging may increase EV market penetration by allowing EVs to use smaller batteries. However, wireless charging of EVs presents challenges in durability because of the high amounts of power that must be transmitted and because of the heat that is generated by high-power transmission. For example, in some charging applications, hundreds or thousands of watts of power may be dissipated depending on, for example, power transmission level and the resistance of the material making up either or both of the transmitter coil 102 and the receiver coil 106. This produces waste heat that causes either or both coils, and surrounding materials to heat up and expand according to the respective coefficients of thermal expansion of the coil/s and materials. When the charging stops the materials will cool and contract. This expansion and contraction may cause degradation in the materials. Charging is likely to happen multiple times per day. If not properly designed and managed, thermal cycling is likely to be a large factor contributing to the failure rate of EV WPT systems. Furthermore, EV WPT requires high input power and therefore the transmitter coil 102 and receiver coil 106 must be able to withstand large currents.

[0026] The receiver coil 106 will typically be mounted on the EV 104 and therefore should be lightweight and not interfere with the aerodynamics of the EV 104. The receiver coil 106 may be provided in an assembly such as that described below with respect to FIG. 17, and the transmitter coil 102 may be provided in an assembly such as that described below with respect to FIG. 17.

The receiver coil 106 and the transmitter coil 102 can be constructed using wires as described below with respect to FIG. 2-10. The receiver coil 106 and the transmitter coil 102 may be provided access to a pair of antennas 108, 110 to communicate control information over a communication channel to control a wireless charging operation between the receiver coil 106 and the transmitter coil 102. Antennas 108, 110 can be provided within EV 104 or as part of the body of transmitter coil 102, among other possible locations.

[0027] Embodiments provide coils for WPT that are constructed with materials reliably capable of carrying high current. FIG. 2 illustrates a rectangular coil 200 that can be used in WPT applications in accordance with some embodiments. The coil 200 can be used as one or both of the transmitter coil 102 (FIG. 1) and the receiver coil 106 (FIG. 1). FIG. 3 illustrates a circular coil 300 that can be used in wireless power transfer (WPT) applications in accordance with some embodiments. Other coil shapes can be used, and embodiments are not limited to rectangular coils and circular coils. In some embodiments, rectangular coil 200 or circular coil 300 (e.g., transmitter coil 102 or receiver coil 106) comprises a wire 202 or 302.

[0028] The wire 202, 302 is wound in a number of turns as shown in FIG. 2 and FIG. 3. All the turns may lie in a single plane in some embodiments, while in in other embodiments at least some turns of the turns may be elevated relative to other turns as shown in FIGs. 4A, 4B, and 4C. FIG. 4A depicts four turns shown in one layer (e.g., no turns are elevated). FIG. 4B depicts six turns in two layers, and FIG. 4C depicts three turns in three layers. The coil 200, 300 may have at least one dimension in accordance with a standard of the Society of Automotive Engineers (SAE) family of standards. For example, in some embodiments, the number of turns may be in accordance SAE standards. In some embodiments, the coil 200, 300 can have a diameter of about 25-70 centimeters. For example, the coil 200, 300 can have a diameter of about 40 centimeters.

[0029] The wire 202, 302 can be comprised, in a first portion, of at least one strand of a metal matrix composite material. The wire 202, 203 can further comprise a second portion comprised of at least one strand of a metal or metal alloy. The wire 202, 302 can be in a variety of shapes, including a substantially round shape, a substantially oval shape, a substantially rectangular shape, or other shape. The wire 202, 302 can have a cross sectional area of about 1 mm ² to 10000mm ² , with wires of some embodiments having a cross sectional area of about 10 mm ² to 1000 mm ² .

[0030] FIG. 5 is a cross-sectional view of a strand 500 of the metal matrix composite material in accordance with some embodiments, wherein the metal matrix composite material is comprised of a metal 502 having fibers 504 embedded therein as described below. The metal matrix composite material can be comprised of an aluminum matrix composite material. The metal matrix composite material can have a plurality of continuous fibers 504 embedded therein. The continuous fibers 504 may be comprised of non-metallic material. For example, the continuous fibers 504 can be comprised of aluminum oxide. Therefore, in some embodiments, the metal matrix composite material can be comprised of aluminum matrix composite material having a plurality of aluminum oxide continuous fibers 504 embedded therein, although embodiments are not limited thereto. [0031] In some embodiments, the non-metallic fibers 504 are aligned with the long axis of the respective wire (e.g., wire 202, 302), although embodiments are not limited thereto. In some embodiments, strands of the metal matrix composite material may be comprised of up to 80% by volume of non-metallic fibers 504. For example, strands of the metal matrix composite material may be comprised of 10% to 50% by volume of non-metallic fibers 504. The non-metallic fibers 504 can have a diameter of about 7-20 microns, and the non-metallic fibers 504 can be of a variety of shapes, including a substantially round shape, a substantially oval shape, a substantially hourglass shape, or other shapes. In some embodiments, strands of the metal matrix composite material may contain non-metallic particles having a diameter of about 0.3 microns to 10 microns. In some examples, the non-metallic particles may have a diameter of about 1 micron to 4 microns.

[0032] Referring again to FIG. 2 and FIG. 3, the wire 202, 302 can comprise a plurality of strands of the metal matrix composite material (the metal matrix composite material being described above with respect to FIG. 5) in some embodiments. In some embodiments, the wire 202, 302 is comprised of 2 to 1000 strands of the metal matrix composite material, each having a diameter of between 0.1 and 10 millimeters. For example, strands of the metal matrix composite material can have a diameter of between .1 and 2 millimeters in some embodiments.

[0033] In some embodiments, the second portion is comprised of a plurality of strands of the metal alloy. The plurality of strands of the metal matrix composite material can be interspersed among plurality of strands of the metal alloy. In some embodiments, the metal alloy includes an alloy of aluminum. In some embodiments, the aluminum alloy is aluminum zirconium (AlZr). At least one strand of the metal alloy may be encased in an electrically insulating material in some examples. FIG. 6 illustrates a circular wire that includes strands 602 of metal alloy and strands 604 of the metal matrix composite material, with at least some of strands 602, 604 including individual strand insulation according to some embodiments. It will be appreciated that a subset of strands 602, 604 may be insulated in some embodiments, or all of strands 602, 604 may be insulated.

[0034] In some embodiments, the number of strands of the metal alloy can be greater than the number of strands of the metal matrix composite material. FIG. 7 illustrates a wire 700 in which the number of strands 702 of the metal alloy is greater than the number of strands 704 of the metal matrix composite material according to some embodiments.

[0035] In some embodiments, the number of strands of the metal alloy can be less than the number of strands of the metal matrix composite material. FIG. 8 illustrates a wire 800 in which the number of strands 802 of the metal alloy is greater than the number of strands 804 of the metal matrix composite material according to some embodiments. [0036] In some embodiments, the wire 202, 302 may be comprised of only strands of the metal alloy while in some embodiments, the wire 202, 302 may be comprised of only strands of the metal matrix composite material. FIG. 9 illustrates a wire 900 in a rectangular configuration and comprised only of strands 902 of the metal matrix composite material according to some embodiments. FIG. 10 illustrates a wire 1000 in a rectangular configuration and comprised only of strands 1002 of the metal alloy according to some embodiments. Electrical insulation 1004 can be provided in these or other embodiments. The electrical insulation can include epoxy resin, although embodiments are not limited thereto.

[0037] In some embodiments, the wire 202, 302, or components thereof, can be comprised of Aluminum Conductor Composite Reinforced (ACCR), available from 3M of Maplewood, Minnesota, or components of ACCR. FIG. 11 illustrates a wire 1100 that is comprised of ACCR according to some embodiments. The wire 1100 includes ceramic fibers embedded in aluminum to form an aluminum matrix composite core 1102, which is then surrounded by a heat-resistant, Al-Zr alloy 1104. Relative to copper wire, the wire 1100 can exhibit high heat-resistance, low thermal expansion, and resistance to corrosion. The wire 1100 can be lightweight while still having high strength, relative to copper wire.

[0038] Table 1 illustrates impedance measurements of coils (e.g., a coil 1200 fabricated using copper material or an aluminum matrix composite core (FIG. 12)) as described herein.

Table 1: Impedance measurement of the fabricated coils.

[0039] As can be seen by Table 1, the DC conductivity of coil fabricated using AMC is around 25% that of copper, in other words the DC resistivity is four times that of copper. Due to this higher resistance, the temperature increase of AMC coils is higher than that of copper coils for the same current. When an outer conductor (e.g., Al-Zr conductor) is used, the DC conductivity of the coil using AMC increased to around 60% that of copper. The temperature increase can also be reduced by adding the outer conductor, or by increasing wire diameter. The temperature increase can also be reduced by reducing the amount of A1203 in the volume. [0040] In general, for wires AC resistance is greater than but proportional to DC resistance. The proportion is influenced by frequency and materials that make up the conductor. It is also noted that the percent increase in resistance from DC resistance to AC resistance was much lower for AMC coils than for copper coils. For example, the increase in resistance for Copper samples (for DC resistance relative to AC resistance) was around 30%. In contrast, the increase for AMC sample 1 was only around 2%.

[0041] FIG. 13 illustrates measured power transfer efficiency (S21) when the transmitter coil and the receiver coil are comprised of various materials according to some embodiments. The transmitter coil 1200 and receiver coil 1200 were kept at a small distance of about 1 centimeter in the example test setup 1400 illustrated in FIG. 14. Referring again to FIG. 13, curve 1302 illustrates S21 when both the transmitter coil and the receiver coil are comprised of AMC. Curve 1304 illustrates S21 when one of the transmitter coil and the receiver coil is comprised of copper and the other is comprised of AMC. Curve 1306 illustrates S21 when both the receiver coil and the transmitter coil are comprised of copper. Table 2 illustrates the power efficiency in table form.

Table 2: Measurement of power transfer efficiency of fabricated coils using different materials.

[0042] As shown in Table 2, the maximum power transfer efficiency is with both the transmitter coil and the receiver coil being comprised of copper. However, using a combination of copper and AMC, the maximum power transfer efficiency degrades but not significantly. The power transfer efficiency of the Copper-AMC and AMC-AMC can be made to approximate the copper-copper configuration by increasing the diameter and/or decreasing the ceramic content and other physical parameter of either or both the transmitter coil and the receiver coil wires. Parameters for the transmitter coil and receiver coil, constructed with ACCR or AMC material, can include number of turns, diameter, width and turn spacing, which can be adjusted based on laboratory modeling or other experiments.

[0043] FIG. 15 is a three-dimensional (3D) rendering of transmitter and receiver coils according to some embodiments. By performing simulations using the model of FIG. 15, users can generate a simulation of power transfer efficiency between coils as shown in FIG. 16. Curve 1602 illustrates S21 when both the transmitter coil 102 and the receiver coil 106 are comprised of AMC. Curve 1604 illustrates S21 when one of the transmitter coil 102 and the receiver coil 106 is comprised of copper and the other is comprised of AMC. Curve 1606 illustrates S21 when both the receiver coil 106 and the transmitter coil 102 are comprised of copper. By comparing simulation results shown in FIG. 16 to measurement results shown in FIG. 13, measurement results can be validated.

[0044] As described earlier herein, the coils and systems of various embodiments can be used for WPT of EVs. FIG. 17 illustrates a coil assembly 1700 for wireless charging of an EV according to embodiments.

[0045] Referring to FIG. 17, the coil assembly 1700 for wireless charging of an EV comprises a means 1702 to attach the coil assembly to a vehicle body. The means 1702 can include a housing, adhesive, epoxy, or other substance or apparatus capable of securing the coil assembly 1700 to, for instance, the undercarriage of an EV (e.g., EV 104 (FIG. 1)). The means 1702 can also include an electrically and/or thermally conductive shield portion that can comprise a metallic material. The conductive shield portion or any other portion of the coil assembly 1700 can be included in or part of an attachment mechanism. The means 1702 can bind the coil assembly 1700 together in addition to helping in attachment of the coil assembly to the EV.

[0046] The coil assembly 1700 includes a receiver coil 1703 comprising a wire wound in a number of turns (not shown in FIG. 17). The receiver coil 1703 and wire can be similar to the coils and wires described earlier herein with respect to FIGs. 1-16. For example, the wire can comprise at least one strand of a metal matrix composite material, the metal matrix composite material comprising a metal with a plurality of non-metallic fibers embedded therein. The receiver coil 1703 can have dimensions and other properties in accordance with a standard of the SAE family of standards, for example the SAE J2954 standard. For example, the distance 1704 between the receiver coil 1703 and the outer edge of the coil assembly 1700 can be about 2-25 millimeters, or in accordance with a standard of the SAE family of standards. The coil assembly height 1706 can be about 3-50 millimeters.

[0047] The coil assembly 1700 can further include magnetic material 1708. The magnetic material 1708 can have an intrinsic magnetic permeability of greater than 10 in some

embodiments. The magnetic material can include ferrite, nanocrystalline ribbons, polymer composite, etc.

[0048] As described earlier herein, in automotive applications, a transmitter coil may be embedded in the ground or on the surface. The transmitter coil may be at a predesignated location for stationary WPT or interspersed on or in a road for WPT while EVs are in motion. FIG. 18 illustrates a coil assembly 1800 that includes transmitter coil 1802 according to some

embodiments. The transmitter coil 1802 and wire can be similar to the coils and wires described earlier herein with respect to FIGs. 1-16. For example, the wire can comprise at least one strand of a metal matrix composite material, the metal matrix composite material comprising a metal with a plurality of non-metallic fibers embedded therein. The coil assembly 1800 can further include an interface 1804 to draw power from an electrical grid 1806. Similarly to the receiver coil 1703 described above, the transmitter coil 1802 can have dimensions and other properties in accordance with a standard of the SAE family of standards, for example the SAE J2954 standard. Also similarly to the coil assembly 1700 (FIG. 17), the coil assembly 1800 can include a housing, adhesive, epoxy, or other substance or apparatus capable of securing the coil assembly 1800 to, for example, protect the coil assembly from environmental factors such as impact, cold, heat, salt, etc. The coil assembly 1800 height can be larger than that of coil assembly 1800, for example, the coil assembly can have a height of 2-200 millimeters in accordance with SAE standards. Similarly to the coil assembly 1700 described above with reference to FIG. 17, the coil assembly 1800 can further include magnetic material with an intrinsic magnetic permeability of greater than 10 in some embodiments. The magnetic material can include ferrite, nanocrystalline ribbons, polymer composite, etc.

[0049] By applying the above-described coils and coil assemblies to high-power WPT, users can achieve charging with fewer failures in the WPT system, relative to copper-based coils and coil assemblies. The coils and coil assemblies described herein will have thermal advantages including high heat resistance and low thermal expansion coefficients at larger power levels such as seen in EV charging applications. Mechanical strength of coil materials is thereby maintained and results in a reduction in the number and severity of mechanical failures in WPT systems. Power transfer efficiency can approach that seen in copper coil-based systems, while allowing for a more lightweight charging system desired by vehicle manufacturers.

[0050] Various modifications and alterations to this invention will become apparent to those skilled in the art without departing from the scope and spirit of this invention. It should be understood that this invention is not intended to be unduly limited by the illustrative embodiments and examples set forth herein and that such examples and embodiments are presented by way of example only with the scope of the invention intended to be limited only by the claims set forth herein as follows.

Additional Embodiments

[0051] The following exemplary embodiments are provided, the numbering of which is not to be construed as designating levels of importance:

[0052] Embodiment 1 provides a coil for inductive charging, the coil comprising: a wire wound in a number of turns, the wire comprising at least one strand of a metal matrix composite material, the metal matrix composite material comprising a metal with a plurality of non-metallic fibers embedded therein.

[0053] Embodiment 2 provides the coil of Embodiment 1, wherein the wire comprises a second portion comprised of at least one strand of a metal alloy.

[0054] Embodiment 3 provides the coil of Embodiment 1, wherein the wire is wound such that all turns of the number of turns he in a single plane.

[0055] Embodiment 4 provides the coil of Embodiment 1, wherein the wire is wound such that at least some turns of the number of turns are elevated relative to other turns of the number of turns.

[0056] Embodiment 5 provides the coil of Embodiment 1, wherein the coil has at least one dimension in accordance with a standard of the Society of Automotive Engineers (SAE) family of standards.

[0057] Embodiment 6 provides the coil of Embodiment 5, wherein the number of turns is in accordance with a standard of the SAE family of standards.

[0058] Embodiment 7 provides the coil of any one of Embodiments 1-6, wherein the coil is wound in a substantially circular configuration and has a diameter of 25-70 centimeters.

[0059] Embodiment 8 provides the coil of any one of Embodiments 1-7, wherein the coil is wound in a substantially circular configuration and has a diameter of about 40 centimeters.

[0060] Embodiment 9 provides the coil of any one of Embodiments 1-8, wherein the coil is wound in a substantially rectangular configuration and wherein a length of the coil is 25-70 centimeters.

[0061] Embodiment 10 provides the coil of any one of Embodiments 1-9, wherein the coil is wound in a substantially rectangular configuration and wherein a length of the coil is about 40 centimeters.

[0062] Embodiment 11 provides the coil of any one of Embodiments 1-10, wherein the wire comprises a plurality of strands of the metal matrix composite material, the second portion is comprised of a plurality of strands of the metal alloy, and the plurality of strands of the metal matrix composite material are interspersed among plurality of strands of the metal alloy.

[0063] Embodiment 12 provides the coil of Embodiment 11, wherein the number of strands of the metal alloy is greater than the number of strands of the metal matrix composite material.

[0064] Embodiment 13 provides the coil of Embodiment 11, wherein the number of strands of the metal matrix composite material is greater than the number of strands of the metal alloy.

[0065] Embodiment 14 provides the coil of any one of Embodiments 1-13, wherein the metal alloy includes an alloy of aluminum.

[0066] Embodiment 15 provides the coil of Embodiment 14, wherein the aluminum alloy is aluminum zirconium (Al-Zr). [0067] Embodiment 16 provides the coil of any one of Embodiments 1-15, wherein the non- metallic fibers are comprised of Ah O3.

[0068] Embodiment 17 provides the coil of any one of Embodiments 11-16, wherein the wire is comprised of 2 to 1000 strands of the metal matrix composite material.

[0069] Embodiment 18 provides the coil of any one of Embodiments 1-17, wherein strands of the metal matrix composite material have a diameter of between 0.1 and 10 millimeters.

[0070] Embodiment 19 provides the coil of any one of Embodiments 1-18, wherein strands of the metal matrix composite material have a diameter of between .1 and 2 millimeters.

[0071] Embodiment 20 provides the coil of any one of Embodiments 1-19, wherein strands of the metal matrix composite material are up to 80% by volume of non-metallic fibers.

[0072] Embodiment 21 provides the coil of any one of Embodiments 1-20, wherein strands of the metal matrix composite material are 10% to 50% by volume of non-metallic fibers.

[0073] Embodiment 22 provides the coil of any one of Embodiments 1-21, wherein the non- metallic fibers have a diameter of about 7-20 microns.

[0074] Embodiment 23 provides the coil of any one of Embodiments 1-22, wherein the non- metallic fibers are substantially round.

[0075] Embodiment 24 provides the coil of any one of Embodiments 1-22, wherein the non- metallic fibers are substantially oval.

[0076] Embodiment 25 provides the coil of any one of Embodiments 1-22, wherein the non- metallic fibers are substantially hourglass-shaped.

[0077] Embodiment 26 provides the coil of any one of Embodiments 1-25, wherein the at least one strand of the metal matrix composite material is encased in a protective material.

[0078] Embodiment 27 provides the coil of any one of Embodiments 1-26, wherein the at least one strand of the metal matrix composite is encased in an electrically insulating material.

[0079] Embodiment 28 provides the coil of any one of Embodiments 1-27, wherein the at least one strand of the metal alloy is encased in a protective material.

[0080] Embodiment 29 provides the coil of any one of Embodiments 1-28, wherein the at least one strand of the metal alloy is encased in an electrically insulating material.

[0081] Embodiment 30 provides the coil of any one of Embodiments 1-29, wherein the wire is substantially round.

[0082] Embodiment 31 provides the coil of any one of Embodiments 1-29, wherein the wire is substantially oval.

[0083] Embodiment 32 provides the coil of any one of Embodiments 1-29, wherein the wire is substantially rectangular. [0084] Embodiment 33 provides the coil of any one of Embodiments 1-32, wherein the strands of the metal matrix composite material contain non-metallic particles.

[0085] Embodiment 34 provides the coil of any one of Embodiments 1-33, wherein the non- metallic particles have a diameter 0.3 microns to 10 microns.

[0086] Embodiment 35 provides the coil of any one Embodiments 1-34, wherein the non-metallic particles have a diameter of 1 micron to 4 microns.

[0087] Embodiment 36 provides the coil of any one of Embodiments 1-35, wherein the wire has a cross sectional area of 1 mm ² to 10000mm ²

[0088] Embodiment 37 provides the coil of any one of Embodiments 1-36, wherein the wire has a cross sectional area of 10 mm ² to 1000 mm ² .

[0089] Embodiment 38 provides a coil assembly for wireless charging of an electric vehicle, the coil assembly comprising: a means to attach the coil assembly to a vehicle body; within the coil assembly, a receiver coil, the receiver coil comprising a wire wound in a number of turns, the wire comprising at least one strand of a metal matrix composite material, the metal matrix composite material comprising a metal with a plurality of non-metallic fibers embedded therein.

[0090] Embodiment 39 provides the coil assembly of Embodiment 38, wherein the wire comprises a second portion comprised of at least one strand of a metal alloy.

[0091] Embodiment 40 provides the coil assembly of Embodiment 38, wherein the receiver coil is in accordance with a standard of the Society of Automotive Engineers (SAE) family of standards.

[0092] Embodiment 41 provides the coil assembly of any one of Embodiments 38-40 wherein the receiver coil is in accordance with SAE J2954.

[0093] Embodiment 42 provides the coil assembly of any one of Embodiments 38-41, wherein the means to attach the coil assembly to a vehicle body includes a housing.

[0094] Embodiment 43 provides the coil assembly of any one of Embodiments 38-41, wherein the means to attach the coil assembly includes an adhesive.

[0095] Embodiment 44 provides the coil assembly of any one of Embodiments 38-41, wherein the means to attach the coil assembly includes an epoxy.

[0096] Embodiment 45 provides the coil assembly of any one of Embodiments 38-44, wherein the receiver coil is wound in a substantially circular configuration and has a diameter of 25-70 centimeters.

[0097] Embodiment 46 provides the coil assembly of any one of Embodiments 38-45, wherein the receiver coil is wound in a substantially circular configuration and has a diameter of about 40 centimeters. [0098] Embodiment 47 provides the coil assembly of any one of Embodiments 38-46, wherein the receiver coil is wound in a substantially rectangular configuration and wherein a length of the coil is 25-70 centimeters.

[0099] Embodiment 48 provides the coil assembly of any one of Embodiments 38-47, wherein the receiver coil is wound in a substantially rectangular configuration and wherein a length of the coil is about 40 centimeters.

[00100] Embodiment 49 provides the coil assembly of any one of Embodiments 38-48, wherein the distance between the receiver coil and outer edge of the coil assembly is 2-25 millimeters.

[00101] Embodiment 50 provides the coil assembly of any one of Embodiments 38-49, wherein the distance between the receiver coil and the outer edge of the coil assembly is in accordance with a standard of the SAE family of standards.

[00102] Embodiment 51 provides the coil assembly of any one of Embodiments 38-50, wherein the coil assembly has a height of 3-50 millimeters.

[00103] Embodiment 52 provides the coil assembly of any one of Embodiments 38-51, wherein the coil assembly has a height in accordance with a standard of the SAE family of standards.

[00104] Embodiment 53 provides the coil assembly of any one of Embodiments 38-52, wherein the coil assembly further comprises magnetic material.

[00105] Embodiment 54 provides the coil assembly of any one of Embodiments 38-53, wherein the magnetic material has an intrinsic magnetic permeability of greater than 10.

[00106] Embodiment 55 provides the coil assembly of any one of Embodiments 38-54, wherein the magnetic material includes ferrite.

[00107] Embodiment 56 provides the coil assembly of any one of Embodiments 38-54, wherein the magnetic material includes nanocrystalline ribbons.

[00108] Embodiment 57 provides the coil assembly of any one of Embodiments 38-56, wherein the magnetic material includes polymer composite.

[00109] Embodiment 58 provides the coil assembly of any one of Embodiments 38-57, wherein the coil assembly further comprises an electrically and/or thermally conductive shield.

[00110] Embodiment 59 provides the coil assembly of any one of Embodiments 38-58, wherein the electrically and/or thermally conductive shield is metallic.

[00111] Embodiment 60 provides a coil assembly for wireless charging of an electric vehicle, the coil assembly comprising: a transmitter coil, the transmitter coil comprising a wire wound in a number of turns, the wire comprising at least one strand of a metal matrix composite material, the metal matrix composite material comprising a metal with a plurality of non-metallic fibers embedded therein; and an interface to draw power from an electrical grid. [00112] Embodiment 61 provides the coil assembly of Embodiment 60, wherein the wire comprises a second portion comprised of at least one strand of a metal alloy.

[00113] Embodiment 62 provides the coil assembly of Embodiment 60, wherein the transmitter coil has a diameter in accordance with a standard of the Society of Automotive Engineers (SAE) family of standards.

[00114] Embodiment 63 provides the coil assembly of any one of Embodiments 60-62, wherein the transmitter coil is in accordance with SAE J2954.

[00115] Embodiment 64 provides the coil assembly of any one of Embodiments 60-63, wherein the coil assembly includes a housing.

[00116] Embodiment 65 provides the coil assembly of any one of Embodiments 60-63, wherein the coil assembly includes adhesive.

[00117] Embodiment 66 provides the coil assembly of any one of Embodiments 60-65, wherein the coil assembly includes epoxy.

[00118] Embodiment 67 provides the coil assembly of any one of Embodiments 60-66, wherein the transmitter coil is wound in a substantially circular configuration and has a diameter of 25-70 centimeters.

[00119] Embodiment 68 provides the coil assembly of any one of Embodiments 60-67, wherein the transmitter coil is wound in a substantially circular configuration and has a diameter of about 40 centimeters.

[00120] Embodiment 69 provides the coil assembly of any one of Embodiments 60-67, wherein the transmitter coil is wound in a substantially rectangular configuration and wherein a length of the coil is 25-70 centimeters.

[00121] Embodiment 70 provides the coil assembly of Embodiment 69, wherein the transmitter coil is wound in a substantially rectangular configuration and wherein a length of the coil is about 40 centimeters.

[00122] Embodiment 71 provides the coil assembly of any one of Embodiments 60-70, wherein the distance between the transmitter coil and an outer edge of the coil assembly is 2-25 millimeters.

[00123] Embodiment 72 provides the coil assembly of any one Embodiments 60-71, wherein the distance between the transmitter coil and the outer edge of the coil assembly is in accordance with a standard of the SAE family of standards.

[00124] Embodiment 73 provides the coil assembly of any of Embodiments 60-72, wherein the coil assembly has a height of 2-200 millimeters.

[00125] Embodiment 74 provides the coil assembly of any one of Embodiments 60-73, wherein the coil assembly has a height in accordance with a standard of the SAE family of standards. [00126] Embodiment 75 provides the coil assembly of any one of Embodiments 60-74, wherein the coil assembly further encloses magnetic material.

[00127] Embodiment 76 provides the coil assembly of any one of Embodiments 60-75, wherein the magnetic material has an intrinsic magnetic permeability of greater than 10.

[00128] Embodiment 77 provides the coil assembly of any one of Embodiments 60-76, wherein the magnetic material includes ferrite.

[00129] Embodiment 78 provides the coil assembly of any one of Embodiments 60-77, wherein the magnetic material contains nanocrystalline ribbons.

[00130] Embodiment 79 provides the coil assembly of any one of Embodiments 60-78, wherein the magnetic material includes polymer composite.

[00131] Embodiment 80 provides the coil assembly of any one of Embodiments 60-78, wherein the coil assembly further encloses an electrically conductive shield.

[00132] Embodiment 81 provides the coil assembly of any one of Embodiments 60-78, wherein the coil assembly further encloses a thermally conductive shield.

[00133] Embodiment 82 provides the coil assembly of any one of Embodiments 60-80, wherein the electrically conductive shield or the thermally conductive shield are metallic.

[00134] Embodiment 83 provides a system for wireless charging, the system comprising: a receiver coil assembly comprising a receiver coil, the receiver coil comprising a wire wound in a number of turns, the wire comprised of at least one strand of a metal matrix composite material, the metal matrix composite material comprising a metal with a plurality of non-metallic fibers embedded therein; a transmitter coil assembly a transmitter coil, the transmitter coil comprising a wire wound in a number of turns, the wire comprised of at least one strand of a metal matrix composite material, the metal matrix composite material comprising a metal with a plurality of non-metallic fibers embedded therein, and an interface to draw power from an electrical grid.

[00135] Embodiment 84 provides the system of Embodiment 83, wherein the wire comprises a second portion comprised of at least one strand of a metal alloy.

[00136] Embodiment 85 provides the system of any one of Embodiments 83-84, wherein one or more of the receiver coil and transmitter coil are in according with Society of Automotive Engineers standard J2954.

[00137] Embodiment 86 provides the system of any one of Embodiments 83-85, wherein one or more of the receiver coil assembly and the transmitter coil assembly includes a housing.

[00138] Embodiment 87 provides the system of any one of Embodiments 83-86, wherein one or more of the receiver coil assembly and the transmitter coil assembly includes adhesive.

[00139] Embodiment 88 provides the system of any one of Embodiments 83-87, wherein or more of the receiver coil assembly and the transmitter coil assembly includes epoxy. [00140] Embodiment 89 provides the system of Embodiment 83, wherein the receiver coil has a diameter in accordance with a standard of the Society of Automotive Engineers (SAE) family of standards.

[00141] Embodiment 90 provides the system of any one of Embodiments 88-89, wherein the receiver coil is wound in a substantially circular configuration and has a diameter of 25-70 centimeters.

[00142] Embodiment 91 provides the system of any one of Embodiments 88-90, wherein the receiver coil is wound in a substantially circular configuration and has a diameter of about 40 centimeters.

[00143] Embodiment 92 provides the system of any one of Embodiments 88-91, wherein the receiver coil is wound in a substantially rectangular configuration and wherein a length of the coil is 25-70 centimeters.

[00144] Embodiment 93 provides the system of any one of Embodiments 88-92, wherein the receiver coil is wound in a substantially rectangular configuration and wherein a length of the coil is about 40 centimeters.

[00145] Embodiment 94 provides the system of any one of Embodiments 83-93, wherein the distance between the transmitter coil and an outer edge of the transmitter coil assembly is 2-25 millimeters.

[00146] Embodiment 95 provides the system of any one of Embodiments 83-94, wherein the distance between the receiver coil and an outer edge of the receiver coil assembly is 2-25 millimeters.

[00147] Embodiment 96 provides the system of any one of Embodiments 83-95, wherein the receiver coil assembly has a height of 2-200 millimeters.

[00148] Embodiment 97 provides the system of any one of Embodiments 83-96, wherein at least one of the receiver coil assembly and the transmitter coil assembly contains magnetic material.

[00149] Embodiment 98 provides the system of any one of Embodiments 83-97, wherein the magnetic material has an intrinsic magnetic permeability of greater than 10.

[00150] Embodiment 99 provides the system of any one of Embodiments 83-98, wherein the magnetic material includes ferrite.

[00151] Embodiment 100 provides the system of any one of Embodiments 83-99, wherein the magnetic material contains nanocrystalline ribbons.

[00152] Embodiment 101 provides the system of any one of Embodiments 83-100, wherein the magnetic material incudes polymer composite.

[00153] Embodiment 102 provides the system of any one of Embodiments 83-101, wherein the receiver coil assembly further encloses an electrically conductive shield. [00154] Embodiment 103 provides the system of any one of Embodiments 83-101, wherein the receiver coil assembly further encloses a thermally conductive shield.

[00155] Embodiment 104 provides the system of any one of Embodiments 83-103, wherein the transmitter coil assembly further encloses an electrically conductive shield.

[00156] Embodiment 105 provides the system of any one of Embodiments 83-103, wherein the transmitter coil assembly further encloses a thermally conductive shield.

[00157] Embodiment 106 provides the system of any one of Embodiments 83-105, wherein the transmitter coil has at least one dimension in accordance with a standard of the Society of Automotive Engineers (SAE) family of standards.

[00158] Embodiment 107 provides the system of any one of Embodiments 83-106, further comprising a pair of antennas to communicate control information over a communication channel to control a wireless charging operation between the receiver coil and the transmitter coil.

[00159] Embodiment 108 provides a system for wireless charging comprising means to inductively receive power, according to any of Embodiments 38-59; and means to inductively transmit power according to any of Embodiments 60-82.