Low Resistance Capacitive Cable

Abstract

The capacitive cable comprises (a) a first plurality of conductors for connection to a power source, (b) a second plurality of conductors for connection to a load, and (c) a dielectric material between the first and second plurality of conductors. Each conductor is individually insulated. At least one conductor of the first plurality of conductors and at least one conductor of the second plurality of conductors are braided or wound into one or more bundles, with each individual conductor repeatedly transitioning between the outside and inside of the one or more bundles along the length of the one or more bundles. The capacitive cable can be used as both a transmission line and a return line.

Description

[Technical Field]

[0001] (Introduction) The present invention relates to a power transmission cable (hereinafter referred to as "capacitive cable") with a capacitive power transmission system, the use of such a cable in power transmission, and a method of power transmission using such a cable. In particular, the present invention relates to a capacitive cable having reduced resistance compared to capacitive cables known in the art, and the use of such a cable in power transmission and a method of power transmission using such a cable. [Background technology]

[0002] (background) Conventional power transmission cables ("conventional cables") are known in the art and are described, for example, in GB 895,501. Capacitive cables for transmitting power between a power source and a load are also known and are described, for example, in EP 3996114, WO 2010 / 026380, WO 2019 / 234449, WO 2021 / 094783, WO 2021 / 094782, and WO 2020 / 120932.

[0003] Capacitive cables are known to be advantageous in certain situations because they transmit power along their length with lower voltage losses than conventional cables, i.e., they can improve the efficiency of a power transmission system. Capacitive cables can have this advantage because they have much lower reactance than conventional cables.

[0004] Domestic power transmission systems in the UK use alternating current (AC) transmitted at a frequency of approximately 50 Hz. Similar systems in the US transmit AC at a frequency of approximately 60 Hz. Power transmission systems with capacitive cables are known to be very efficient when power / electricity is transmitted along the capacitive cables at these relatively low frequencies.

[0005] While domestic power grids transmit power at low frequencies, power grids that use much higher frequencies are also known. For example, power grids in aircraft and airports typically transmit power at a frequency of around 400 Hz. Similar frequencies are also used in power grids for maritime applications. High frequency power transmission is also used in the application of wireless charging for electric vehicles. It will be appreciated that there are other known applications for high frequency power transmission. Currently, power standards in the UK and the US approve the supply of high frequency power at frequencies of around 20 kHz and around 70 kHz to 95 kHz (usually around 80 kHz to 85 kHz, especially around 85 kHz).

[0006] It is known that the magnitude of voltage loss when transmitting power along a cable depends on the frequency at which the power is transmitted. Specifically, the higher the frequency used, the greater the loss. When low frequencies such as 50 Hz and / or 60 Hz are used, the low reactance of capacitive cables is sufficient to minimize voltage loss along these cables. However, it has been reported that significant voltage loss occurs when transmitting power at high frequencies along these cables. Therefore, known capacitive cables are not well suited for applications that transmit power at high frequencies, as they may not be able to transmit power efficiently at such frequencies. This means that, until now, it has been impossible to realize the benefits of using capacitive cables to transmit power at low frequencies when high frequencies are used instead.

[0007] The above-mentioned problems associated with using capacitive cables for high-frequency power transmission have traditionally been attributed to the high capacitance of these cables. Accordingly, those skilled in the art currently believe that high capacitance is undesirable for cables designed to transmit power at high frequencies. For example, US 2015 / 041172 teaches that cables for efficient power transmission at high frequencies should be designed to have low capacitance. DE 102016210152 similarly teaches that cables with high capacitance exhibit undesirable heating and increased losses when power is transmitted at high frequencies along such cables. However, the present inventors have newly discovered that the above-mentioned problems associated with using capacitive cables for high-frequency power transmission are actually primarily due to the high resistance of these cables, rather than their high capacitance.

[0008] It is desirable to provide a capacitive cable suitable for efficient power transmission at high frequencies with minimal voltage loss along its length, and the present inventors are the first to recognize that this may be achieved by designing the capacitive cable to have low resistance.

[0009] Power transmission systems using capacitive cables as transmission lines for transmitting power from a power source / power supply to a load are known. In such power transmission systems, a ground is typically used as a return line to return power from the load to the source, completing the electrical circuit. While these circuits typically operate with sufficiently low voltage losses when low-frequency power transmission is used, a new problem discovered by the inventors is that when high-frequency power transmission is used instead, large voltage losses are typically observed. This is particularly true when the cable and / or ground have high resistance characteristics. Such large voltage losses are partially due to high resistance in the transmission line and / or return line, which causes current to flow more easily through one line than the other, resulting in an imbalance between the current flow in the transmission line and the current flow in the return line.

[0010] It would therefore be desirable to provide a power transfer system including a capacitive cable that has low resistance and is therefore suitable for high frequency transmission of power.

[0011] Furthermore, power transmission systems that include capacitive cables as transmission lines and grounds as return lines typically generate large electric and magnetic fields around the ground / return lines. If these electric and magnetic fields are generated with sufficient magnitude, they can harm the health of people and animals in close proximity and can cause significant voltage losses. When power is transmitted through such systems at low frequencies, the magnitude of the generated electric and magnetic fields is small enough that these problems are hardly noticeable. However, the inventors have newly discovered that when power is transmitted through such systems at high frequencies, these electric and magnetic fields can be generated with much larger magnitudes, making such systems inefficient and potentially posing a dangerous health hazard. Therefore, the use of capacitive cables in high-frequency power transmission systems has previously been considered impractical. Summary of the Invention [Problem to be solved by the invention]

[0012] Therefore, there remains a desire to provide a power transmission system that includes a capacitive cable as a transmission line that improves the safety and efficiency of such power transmission systems by minimizing the electric and magnetic fields generated around the return wire, thereby ensuring that the power transmission system is suitable for high frequency applications.

[0013] It is also generally desirable to provide alternative, and preferably improved, power transfer systems and capacitive cables. [Means for solving the problem]

[0014] The present invention provides a capacitive cable that has lower resistance than known prior art capacitive cables. The present invention also provides the use of low resistance capacitive cables in power transmission systems and methods of power transmission using low resistance capacitive cables.

[0015] An advantage of the capacitive cable of the present invention is that the cable can be designed so that resistance to current flow is reduced, preferably minimized, and so that reactance is reduced, preferably minimized. The low reactance of the cable means that the advantages of prior art capacitive cables over conventional cables apply equally to the capacitive cable of the present invention. The low resistance of the cable of the present invention means that the cable may be particularly suitable for power transmission at high frequencies. Such power transmission has previously been possible with known capacitive cables, as described elsewhere, but has nevertheless been non-ideal and difficult to achieve.

[0016] Another advantage of the capacitive cables of the present invention is that they can be designed to transmit power with lower voltage losses along their length, reduced harmonics, and increased power delivery compared to conventional cables of similar dimensions. Thus, the capacitive cables of the present invention can provide more efficient power transmission along their length than conventional cables of similar dimensions.

[0017] The capacitive cables of the present invention may be suitable for efficiently transmitting power at any frequency generally considered "high frequency," i.e., at least 350 Hz. The capacitive cables of the present invention may be particularly suitable for efficiently transmitting power at frequencies between 400 Hz and 3 MHz, and particularly between 400 Hz and 2.8 MHz. The capacitive cables of the present invention may also be particularly suitable for efficiently transmitting power at frequencies corresponding to those recognized by UK and US electrical power standards, i.e., frequencies of about 20 kHz and about 70 kHz to 95 kHz (usually about 80 kHz to 85 kHz, particularly about 85 kHz).

[0018] An advantage of using the capacitive cable of the present invention in a power transfer system is that the resistance of the system may be reduced compared to power transfer systems that use prior art capacitive or conventional cables instead.

[0019] A further advantage of using the capacitive cable of the present invention in a power transmission system is that improved balance between the transmission line and the return line may be achieved, thereby increasing the efficiency of the system compared to known power transmission systems. Alternatively or additionally, two capacitive cables of the present invention or two sub-cables of a capacitive cable of the present invention (one as the transmission line and the other as the return line) may be used in the same power transmission system, which may further improve the balance between the transmission line and the return line and maximize the efficiency of the system.

[0020] A third advantage of using the capacitive cable of the present invention in a power transfer system is that, in embodiments where a ground is not used as a return conductor, the electric and magnetic fields around the return conductor can be reduced and localized near the cable rather than being spread out over a wider area. This minimizes the electric and magnetic fields around the return conductor, thereby reducing the potential for harm from the power transfer system to people or animals near the system and improving the efficiency of the system.

[0021] An advantage of the method of the present invention is that power can be transmitted with minimal resistance, i.e., with high efficiency, from a power source at / connected to one end of the capacitive cable to a load at / connected to the other end of the capacitive cable, even when the power is transmitted at high frequency. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 shows a schematic perspective view of a capacitive cable bundle according to an embodiment of a first aspect of the present invention. [Figure 2]FIG. 2 shows a schematic perspective view of a capacitive cable bundle according to an embodiment of a first aspect of the present invention, the bundle comprising a first plurality of conductors and a second plurality of conductors. [Figure 3] FIG. 3 shows a schematic cross-sectional view (end view) of a capacitive cable comprising the bundle of FIG. [Figure 4] FIG. 4 shows a schematic cross-sectional view (end view) of a capacitive cable according to an embodiment of the first aspect of the present invention. [Figure 5] FIG. 5 shows a schematic cross-sectional view (end view) of another capacitive cable according to an embodiment of the first aspect of the present invention. [Figure 6] FIG. 6 shows a schematic cross-sectional view (end view) of another capacitive cable according to an embodiment of the first aspect of the present invention. [Figure 7] FIG. 7 shows a schematic cross-sectional (end) view of a capacitive cable similar to that shown in FIG. 3, but further comprising a conductive screen. [Figure 8] FIG. 8 shows a schematic cross-sectional (end) view of another capacitive cable according to an embodiment of the first aspect of the present invention, where the bundle is arranged so that two capacitive sub-cables are radially aligned. [Figure 9] FIG. 9 shows a schematic cross-sectional (end) view of another capacitive cable according to an embodiment of the first aspect of the present invention, in which the bundles are arranged such that two capacitive sub-cables are side-by-side and the bundles of each sub-cable are aligned vertically. [Figure 10] FIG. 10 shows a schematic cross-sectional (end) view of another capacitive cable according to the first embodiment of the present invention, in which two capacitive sub-cables are arranged side by side with the bundles of each sub-cable aligned diagonally. [Figure 11] FIG. 11 shows a schematic cross-sectional (end) view of another capacitive cable according to an embodiment of the first aspect of the present invention, where the bundle is arranged so that four capacitive sub-cables are side-by-side. [Figure 12]FIG. 12 shows a schematic cross-sectional (end) view of another capacitive cable according to an embodiment of the first aspect of the present invention, where the bundle is arranged so that six capacitive sub-cables are side-by-side. [Figure 13] FIG. 13 shows a circuit diagram of a capacitive cable according to the first aspect of the present invention, used in accordance with an embodiment of the second aspect of the present invention. [Figure 14] FIG. 14 shows a circuit diagram of a capacitive cable according to the first aspect of the present invention used in accordance with another embodiment of the second aspect of the present invention. [Figure 15] FIG. 15 shows a circuit diagram of two capacitive cables according to the first aspect of the invention used in accordance with the third aspect of the invention. [Figure 16] FIG. 16 shows a schematic cross-sectional view (end view) of a capacitive cable according to an embodiment of the first aspect of the present invention. [Figure 17] FIG. 17 shows a schematic extrusion side view of braiding / wrapping two of the cables of FIG. 16 around each other. DETAILED DESCRIPTION OF THE INVENTION

[0023] (Detailed Description of the Invention) According to a first aspect of the present invention, (a) a first plurality of conductors for connection to a power source; (b) a second plurality of conductors for connection to a load; (c) a dielectric material between the first plurality of conductors and the second plurality of conductors; A capacitive cable comprising: A capacitive cable is provided in which each conductor is individually insulated.

[0024] The capacitive cable can transmit power at high frequencies.

[0025] The phrase "each" conductor is individually insulated is intended to mean that most conductors are individually insulated. Thus, there may be one or more, e.g., some, conductors that are not individually insulated. The important point is that a sufficient number of conductors must be individually insulated to prevent or at least substantially minimize the number of direct electrical connections between conductors, particularly between a first plurality of conductors and a second plurality of conductors. Preferably, however, all conductors are individually insulated.

[0026] The first plurality of conductors may be for connection only to a power source, i.e., not connected to a load. Alternatively or additionally, the second plurality of conductors may be for connection only to a load, i.e., not connected to a power source. Connecting the first plurality of conductors only to a power source and the second plurality of conductors only to a load may establish a capacitive relationship between the first and second plurality of conductors. It will be understood that "connected" in this context is intended to mean "direct electrical connection."

[0027] The conductors may be made of any material capable of conducting electricity, however, the conductors are preferably made of copper or aluminum.

[0028] The conductors may be of any shape. Preferably, when viewed in cross section from one end thereof, each conductor is circular, square, rectangular, or triangular in shape. It will be understood that different conductors may be of different shapes. Preferably, however, all conductors of the first plurality of conductors are the same shape and all conductors of the second plurality of conductors are the same shape. All conductors may be the same shape.

[0029] The dielectric material may be comprised of any type of substance having suitable properties, such as a dielectric constant large enough to achieve a capacitive relationship between the first and second plurality of conductors when the capacitive cable is used for power transmission. However, the dielectric material is preferably selected from the group consisting of polyvinyl chloride, low density polyethylene, high density polyethylene, ethylene propylene rubber ("EPR"), polyurethane, polyamide nylon ruslan, Grade 12 nylon, polyethylene terephthalate, polypropylene, polyvinylidene chloride, tetrafluoroethylene, polytetrafluoroethylene, perfluoroalkyl, polyimide, silicone rubber, and aluminum-based dielectric tape.

[0030] A capacitive cable may be comprised of only one type of dielectric material. Alternatively, a capacitive cable may be comprised of multiple types of dielectric materials. It will be understood that the type, number, and / or thickness of the dielectric materials used in a capacitive cable will be determined based on the intended use of the capacitive cable and may be selected based on the capacitive, mechanical, thermal, and / or other electrical properties of each type of dielectric material. Accordingly, as used herein, the phrase "dielectric material" will be interpreted to mean "one or more dielectric materials."

[0031] The conductors may be individually insulated using any material capable of preventing the flow of current between adjacent conductors, i.e., electrically insulating adjacent conductors from each other. However, the insulator is typically enamel. Preferably, the enamel is polyurethane or polyesterimide. The insulator may also be a dielectric material.

[0032] At least one conductor of the first plurality of conductors and at least one conductor of the second plurality of conductors may be braided or wound into one or more bundles, and each individual conductor may repeatedly transition between the outside of the one or more bundles and the inside of the one or more bundles along the length of the one or more bundles.

[0033] At least one conductor of the first plurality of conductors and at least one conductor of the second plurality of conductors may be braided or wound into one or more bundles, and each individual conductor may be repeatedly positioned outside the one or more bundles for a distance along the length of the one or more bundles and inside the one or more bundles for a distance.

[0034] At least one conductor of the first plurality of conductors and at least one conductor of the second plurality of conductors may be braided or wound into one or more bundles, and each conductor may transition repeatedly from inside the one or more bundles to outside the one or more bundles along the length of the one or more bundles.

[0035] At least one conductor of the first plurality of conductors and at least one conductor of the second plurality of conductors may be braided or wound into one or more bundles, and each conductor may be positioned along the length of the one or more bundles on the outside of the one or more bundles for a portion of the length of the one or more bundles and on the inside of the one or more bundles for a portion of the length of the one or more bundles.

[0036] At least one conductor of the first plurality of conductors and at least one conductor of the second plurality of conductors may be braided or wound into one or more bundles, and each conductor may be positioned outside one or more bundles for part or portions of the length of the one or more bundles and inside one or more bundles for part or portions of the length of the one or more bundles.

[0037] At least one conductor of the first plurality of conductors and at least one conductor of the second plurality of conductors may be braided or wound into one or more bundles, and each individual conductor may be repeatedly positioned outside the one or more bundles over a portion of the length of the one or more bundles and inside the one or more bundles over a portion of the length of the one or more bundles.

[0038] At least one conductor of the first plurality of conductors and at least one conductor of the second plurality of conductors may be braided or wound into one or more bundles, and each conductor may transition repeatedly from inside the one or more bundles to outside the one or more bundles along the length of the one or more bundles.

[0039] At least one conductor of the first plurality of conductors and at least one conductor of the second plurality of conductors may be braided or wound into one or more bundles, and each conductor may transition between the inside and outside of the one or more bundles along the length of the one or more bundles.

[0040] As detailed above, braiding / winding the conductors into one or more bundles may reduce the resistance, particularly the AC resistance, of a capacitive cable when power is transmitted in the form of alternating current ("AC") from one end of the capacitive cable to the other. In particular, braiding / winding the conductors in this manner may minimize the skin effect and / or proximity effect exhibited by each conductor when power is transmitted, compared to a capacitive cable in which the conductors are not braided or wound in this manner. Reducing the skin effect and / or proximity effect in this manner may significantly reduce voltage losses along the length of the cable.

[0041] As used herein, the term "capacitive cable" is intended to mean a cable having capacitive coupling within its conductors. The term "capacitive cable" does not refer to the capacitance characteristics of a conventional cable, i.e., a conventional conductive cable such as those used in conventional power transmission systems. Nor does the term "capacitive cable" refer to the capacitance between two insulated conductors in a conventional power transmission system. Instead, the term "capacitive cable" refers to a cable that is part of a capacitive transmission system and is represented in a circuit diagram as a capacitor. As noted above, examples of capacitive cables known in the art are described in EP 3996114, WO 2010 / 026380, WO 2019 / 234449, WO 2021 / 094783, WO 2021 / 094782, and WO 2020 / 120932.

[0042] As used herein, the term "conventional cable" is intended to mean a cable having conductors for connection to or connected to both a power source and a load. Typically, one end of the conductor is connected to the power source and the other end of the conductor is connected to the load.

[0043] As used herein, the term "transmission line" is intended to mean an electrical component used in an electrical circuit / power transmission system to transmit power from a source to a load. In contrast, the term "return conductor" is intended to mean an electrical component used in an electrical circuit / power transmission system to transmit power from a load to a source. It will be understood that both a transmission line and a return conductor are required for an electrical circuit to be complete and function as an electrical circuit.

[0044] As used herein, the term "conductor" is intended to mean any material that can conduct electricity, i.e., that is capable of conducting electricity. It will be understood that a conductor in the context of a cable typically has an elongated structure that can be disposed along the length of the cable. Conductors having such a structure may also be conveniently referred to as "conductive strands," or simply "strands."

[0045] As used herein, the term "dielectric material" is intended to mean any substance having dielectric properties that, when positioned between a first conductor connected to a power source and a second conductor connected to a load, can mediate a capacitive relationship between a first conductor and a second conductor when the power source is activated and power is being applied. It will be understood that the dielectric properties, e.g., dielectric strength, of a particular substance can be determined by factors such as the dielectric constant of the substance, the dissipation factor of the substance, the breakdown voltage of the substance, the chargeability of the substance, the dielectric polarization of the substance, the total polarization of the substance, and the dielectric dispersion of the substance.

[0046] As used herein, the term "insulator" is intended to mean any material that electrically insulates one material from another. Thus, when a first conductor is said to be "insulated" from a second conductor, this means that the insulator electrically separates the first conductor from the second conductor.

[0047] As used herein, the term "bundle" is intended to be a generic term used to describe multiple conductors that are braided or wound together.

[0048] As used herein, the term "power transmission system" is intended to mean any electrical circuit in which power is transmitted from a power source / power supply to a load.

[0049] As used herein, the term "radial" is intended to mean the direction between the center of the cable and the outer periphery of the cable when the cable is viewed in cross section from one end thereof.

[0050] As used herein, the term "cable" is intended to mean an electrical component used to transmit power between a power source and a load. A cable may transmit power over an overhead tower. A cable may transmit power from a household outlet to a household electrical machine / appliance.

[0051] All of the conductors may be braided or wound into one or more bundles. Braiding / wrapping all of the conductors into one or more bundles may maximize the efficiency of the cable by ensuring that skin and / or proximity effects are minimized in all conductors, not just some, compared to embodiments in which not all conductors are braided or wound into one or more bundles. It will be appreciated that this may help reduce the resistance of capacitive cables.

[0052] The percentage of the length of one or more bundles that each conductor is outside of the bundle may be similar (or the same) among the conductors. By braiding / winding the conductors in this manner, it is possible to ensure that the skin effect and / or proximity effect is similar (or the same) among each conductor, rather than some conductors exhibiting a greater skin effect and / or proximity effect than others. It will be appreciated that this may help reduce the resistance of capacitive cables.

[0053] The capacitive cable may transmit power in a single phase, three phases, six phases, or nine phases. Alternatively, a number of phases greater than nine may be used. In such embodiments, the capacitive cable may be described as a "single phase capacitive cable," a "three phase capacitive cable," a "six phase capacitive cable," a "nine phase capacitive cable," etc., respectively, i.e., a capacitive cable of such phases.

[0054] It will be appreciated that any cable having at least three conductors may be used as a three-phase cable by appropriately connecting the conductors to each phase of a three-phase power supply, or as a single-phase cable by connecting all conductors to a single-phase power supply.

[0055] Similarly, it will be appreciated that a cable having at least six conductors may be used as a six-phase cable by connecting a conductor to each phase of a six-phase power supply, as a three-phase cable by connecting a conductor (or conductor pair) to each phase of a three-phase power supply, or as a single-phase cable by connecting all conductors to a single-phase power supply.

[0056] It will also be understood that a cable having at least nine conductors may be used as a nine-phase cable by connecting a conductor to each phase of a nine-phase power supply, as a three-phase cable by connecting conductors (in groups of three) to each phase of a three-phase power supply, or as a single-phase cable by connecting all conductors to a single-phase power supply.

[0057] It will be appreciated that, in general, the more phases used, the more efficient the power transmission along the cable. However, it will also be appreciated that, in general, the more phases used, the more costly the power transmission along the cable will be due to the increased complexity of the power source / power supply required. It will therefore be appreciated that the selection of the number of phases used requires a trade-off between efficiency and cost.

[0058] The capacitive cable can have any number of conductors. However, preferably, each bundle contains at least 300, more preferably at least 500, even more preferably at least 1000, and even more preferably at least 2000 conductors. In a specific embodiment described in more detail below, one bundle had 1600 conductors and another bundle had 1620 conductors. Using such a number of conductors can improve the ability of the capacitive cable to transmit current along its length due to reduced resistance, making the capacitive cable particularly suitable for use in typical high-frequency power transmission system applications, including, for example, airport and aircraft applications, as well as maritime and wireless electric vehicle charging applications. It will be appreciated that fewer conductors are required to transmit the same amount of power if the cable is intended for connection as a three-phase capacitive cable than if the cable is intended for connection as a single-phase capacitive cable. Similarly, it will be appreciated that even fewer conductors are required if the cable is intended for connection as a six-phase capacitive cable, and even fewer conductors are required if the cable is intended for connection as a nine-phase capacitive cable.

[0059] The conductors may be braided or wound together into a single bundle, and each conductor may be individually insulated with a dielectric material. Alternatively, the conductors may be braided or wound together into multiple bundles. For example, a first plurality of conductors may be braided or wound together into a first bundle, and a second plurality of conductors may be braided or wound together into a second bundle. As another example, the first plurality of conductors may be braided or wound together into a first plurality of bundles, and the second plurality of conductors may be braided or wound together into a second plurality of bundles. As a variation of this example, the first and second plurality of bundles may be arranged into one or more concentric bundles. As a third example, the first and second plurality of conductors may be braided or wound together into multiple bundles, each bundle including at least one conductor from the first plurality of conductors and at least one conductor from the second plurality of conductors.

[0060] The conductors / conductor bundles may be arranged around a shaped portion, which may be located in the center of the cable (when the cable is viewed in cross section from one end of the cable). The shaped portion may consist of any material, but is preferably made of a plastic or metal material.

[0061] Each conductor may be a non-tubular conductor or a tubular conductor, such as a tubular copper conductor. Tubular conductors may be advantageous because they may achieve a lower skin effect and therefore a lower overall resistance than non-tubular conductors when power is transmitted along / through them at high frequencies.

[0062] Each conductor may be copper clad aluminum wire ("CCA wire"), which may have the advantage of being less expensive to manufacture than conductors made solely of copper and having improved conductivity and strength compared to conductors made solely of aluminum.

[0063] Each bundle may be a litz wire. The litz wire may be any type of litz wire, but is preferably selected from the group consisting of basic litz wire, concentric litz wire, bundled litz wire, molded litz wire, tape-shaped litz wire, extruded litz wire, rectangular ("profiled") litz wire, coated litz wire, litz wire with strain relief, EFOLIT litz wire, litz magnetic plate wire ("LMPW"), litz magnetic coated wire ("LMCW"), type 1 litz wire, type 2 litz wire, type 3 litz wire, type 4 litz wire, type 5 litz wire, type 6 litz wire, type 7 litz wire, type 8 litz wire, and type 9 litz wire. It is noteworthy that in conventional litz wire, not all conductors are insulated to completely eliminate direct electrical connections between the conductors. Therefore, in the present invention, preferably, all conductors are individually insulated to eliminate direct electrical connections between the conductors.

[0064] The type of litz wire used may depend on factors such as the frequency at which power will be transmitted along the length of the cable, the magnitude of the current and / or voltage at which power will be transmitted along the length of the cable, the maximum temperature rise allowed in the cable used, and / or the diameter of the conductor used. The inventors have found that certain types of litz wire may be preferred at certain frequencies of power transmission because they can transmit power more efficiently at those frequencies than other types of litz wire.

[0065] In embodiments where the capacitive cable transmits power at frequencies between 400 Hz and 1 kHz, the litz wire is preferably type 8 litz wire.

[0066] In embodiments in which the capacitive cable transmits power at frequencies between 1 kHz and 2 MHz, the litz wire is preferably selected from the group consisting of concentric litz wire, bundled litz wire, covered litz wire, formed litz wire, Type 2 litz wire, Type 7 litz wire, and Type 8 litz wire. In embodiments in which power is transmitted at frequencies near the lower end of this range, i.e., between 1 kHz and 50 kHz, the litz wire is preferably concentric litz wire or Type 8 litz wire. In embodiments in which power is transmitted at frequencies slightly higher than near the lower end of this range, i.e., between 50 kHz and 850 kHz, the litz wire is preferably bundled litz wire or Type 8 litz wire. In embodiments in which power is transmitted at frequencies near the higher end of this range, i.e., between 850 kHz and 2 MHz, the litz wire is preferably selected from the group consisting of covered litz wire, formed litz wire, Type 2 litz wire, Type 7 litz wire, and Type 8 litz wire.

[0067] The capacitive cable may further include a conductive screen. This "conductive screen" may be referred to, for example, as a "conductive shield," or simply as a "screen" or "shield." Typically, the conductive screen may be located on the outside of the capacitive cable, i.e., on the outer periphery of the cable, when the cable is viewed in cross section from one end of the cable. The inclusion of a conductive screen may be beneficial because it can shield people or animals in the vicinity of the capacitive cable from electric and magnetic fields that are generated around the cable as power is transmitted along the length of the cable. This may improve the safety of power transmission systems in which capacitive cables are used. The conductive screen may be made of any conductive material. Preferably, the conductive screen is made of copper or aluminum. More preferably, the conductive screen is made of multiple copper strands or multiple aluminum strands.

[0068] The conductive screen may be for connection as a return conductor. In a power transmission system where the screen is used as a return conductor, the screen may exhibit a lower resistance than ground (which may be used as a return conductor in a power transmission system where a conductive screen is not present), which means that the balance between the power transmission line and the return conductor may be improved compared to using ground as the return conductor.

[0069] Additionally, the conductive screen may be a litz wire. This configuration may be particularly advantageous in power transmission systems where the conductive screen is connected as a return conductor, as using litz wire as the conductive screen ensures that the return conductor resistance is minimized. By minimizing the return conductor resistance in this manner, a better balance may be achieved between the transmission line and the return conductor during use, further improving the efficiency of the power transmission system.

[0070] In embodiments where the conductors are braided or wound into multiple bundles, the bundles may be side-by-side or radially aligned.

[0071] The capacitive cable may be for connection as both a transmission line and a return line. Thus, the capacitive cable may include at least four bundles of conductors. Preferably, the first plurality of conductors is braided / wound into at least two bundles, and the second plurality of conductors is braided / wound into at least two bundles. More preferably, the first plurality of conductors is braided / wound into first and second bundles, and the second plurality of conductors is braided / wound into third and fourth bundles. Such an embodiment may be particularly advantageous because it facilitates integrating the transmission line and the return line into the same capacitive cable, for example, by using one bundle formed by the first plurality of conductors and one bundle formed by the second plurality of conductors together as a transmission line, and another bundle formed by the first plurality of conductors and another bundle formed by the second plurality of conductors together as a return line. Braiding / wrapping the first plurality of conductors into first and second bundles and braiding / wrapping the second plurality of conductors into third and fourth bundles may be particularly advantageous because it may facilitate separation of the conductors for connection to the power source and the conductors for connection to the load at the end of the cable, and may also facilitate separation of the transmission line conductors and the return line conductors from each other.

[0072] The insulation of the first plurality of conductors may be a different color than the insulation of the second plurality of conductors. For example, the insulation of the first plurality of conductors may be red and the insulation of the second plurality of conductors may be green. The use of different colors may be advantageous because it allows personnel installing the capacitive cable at the installation site to easily distinguish between the first and second plurality of conductors, thereby facilitating separation of the two types of conductors from each other at the end of the cable and connection of the first plurality of conductors to a power source and the second plurality of conductors to a load.

[0073] Alternatively or additionally, four different colors may be used, i.e., two colors for the first plurality of conductors and two colors for the second plurality of conductors. For example, the insulation of half of the first plurality of conductors may be a first color (e.g., red), the insulation of the other half of the first plurality of conductors may be a second color (e.g., blue), the insulation of half of the second plurality of conductors may be a third color (e.g., green), and the insulation of the other half of the second plurality of conductors may be a fourth color (e.g., yellow). The use of four colors may be particularly advantageous in embodiments in which the capacitive cable is for connection as both a transmission line and a return line, as it may allow the four conductor groups (transmission line / power, transmission line / load, return line / power, and return line / load) to be easily identified.

[0074] The bundle may be arranged to form two or more capacitive sub-cables within a capacitive cable. As used herein, the terms “capacitive sub-cable” and “sub-cable” are used interchangeably and are intended to refer to a structure that, while isolated, has the characteristic properties of a capacitive cable described elsewhere and herein. Thus, each capacitive sub-cable may include a first plurality of conductors for connection to a power source (but not for connection to a load) and a second plurality of conductors for connection to a load (but not for connection to a power source). The capacitive sub-cables may be side-by-side, e.g., adjacent to each other when the capacitive cable is viewed in cross section from one end. Alternatively or additionally, the capacitive sub-cables may be radially aligned, i.e., one capacitive sub-cable may be positioned radially outward of the other capacitive sub-cable so that it radially surrounds the other capacitive sub-cable when the capacitive cable is viewed in cross section from one end. It will also be appreciated that by arranging the bundle into two or more capacitive sub-cables, one or more of the capacitive sub-cables can be easily connected as a transmission line and one or more of the other capacitive sub-cables can be easily connected as a return line. Thus, a capacitive cable can include a first capacitive sub-cable for connection as a transmission line and a second capacitive sub-cable for connection as a return line.

[0075] The capacitive cable may include four conductor bundles arranged side by side to form two sub-cables, each sub-cable including a bundle formed of a first plurality of conductors and a bundle formed of a second plurality of conductors. The two bundles of each sub-cable may be arranged diagonally or vertically side by side when the capacitive cable is viewed in cross section from one end of the cable. It will be appreciated that these arrangements allow one sub-cable to be easily connected as a transmission line and the other sub-cable to be easily connected as a return line. This embodiment is preferable because it reduces inductance and improves the balance between the transmission line and the return line, thereby improving the efficiency of the cable, compared to when the transmission line and the return line are provided in separate cables.

[0076] To facilitate the connection of capacitive cables as both transmission and return lines, capacitive cables are (a) a first plurality of conductors for connection to a power source (but not for connection to a load); (b) a second plurality of conductors for connection to a load (but not for connection to a power source); (c) a third plurality of conductors for connection to a power source (but not for connection to a load); and (d) a fourth plurality of conductors for connection to a load (but not for connection to a power source); and (e) a dielectric material between the first plurality of conductors and the second plurality of conductors; (f) a dielectric material between the third plurality of conductors and the fourth plurality of conductors; and the first plurality of conductors and the second plurality of conductors are collectively connected as a transmission line; the third plurality of conductors and the fourth plurality of conductors are for connection together as a return line; Each conductor is individually insulated.

[0077] At least one conductor of the first plurality of conductors, at least one conductor of the second plurality of conductors, at least one conductor of the third plurality of conductors, and at least one conductor of the fourth plurality of conductors may be braided or wound into one or more bundles, and each individual conductor may repeatedly transition between the outside of the one or more bundles and the inside of the one or more bundles along the length of the one or more bundles.

[0078] It should be understood that for a cable of the present invention to be considered a “capacitive cable,” a capacitive relationship must exist between the first and second conductors during use. To achieve this, the first conductors should be connected to a power source (but not a load) and the second conductors should be connected to a load (but not a power source). To facilitate such connection of the conductors, the first conductors may be connected to one another at a first end of the capacitive cable, and the second conductors may be connected to one another at a second end of the capacitive cable. It should be understood that for a capacitive relationship to exist between the first and second conductors when the cable is used to transmit power, there must be no direct electrical connection between the first and second conductors along the length of the cable. In other words, for a capacitive relationship to exist between the first and second conductors when the cable is used to transmit power, the first and second conductors must be electrically isolated from one another.

[0079] In embodiments where the capacitive cable is for connection as both a transmission line and a return line, half of the conductors of the first plurality may be connected to each other at a first end of the capacitive cable, another half of the conductors of the first plurality may be connected to each other at the first end of the capacitive cable, half of the conductors of the second plurality may be connected to each other at a second end of the capacitive cable, and another half of the conductors of the second plurality may be connected to each other at the second end of the capacitive cable, which may facilitate connection of the conductors in an appropriate manner.

[0080] According to a second aspect of the present invention, (i) the first plurality of conductors are connected to the power source (but not to the load); (ii) There is provided the use of a capacitive cable according to the first aspect of the invention in a power transmission system, wherein the second plurality of conductors are connected to the load (but not to the power source).

[0081] The cable is used for power transmission. It should be understood that connecting the conductors in the above manner establishes a capacitive relationship between the first and second conductors. This makes the cable a capacitive cable, ensuring power transfer from the source to the load.

[0082] The cable may be used to transmit power at high frequencies.

[0083] The first and second plurality of conductors may be used together as a transmission line, with a ground or conventional cable used as a return line. In such an embodiment, by using the capacitive cable of the first aspect of the present invention as the transmission line rather than a conventional cable, the resistance of the transmission line may be reduced compared to a power transmission system that uses a conventional cable as the transmission line instead. This may improve the efficiency of the system.

[0084] Alternatively, the first and second plurality of conductors may be used together as a transmission line, with the conductive screen used as a return line. A conductive screen typically exhibits a lower resistance to current flowing along it than ground (which may be used as a return line in embodiments where a conductive screen is not present). This means that the balance between the transmission line and the return line can be improved compared to using ground as a return line.

[0085] As explained above in relation to the first aspect of the present invention, a capacitive cable may be configured to integrate a conductor for use as a transmission line and a conductor for use as a return line in the same capacitive cable, and thus the capacitive cable may be used as both a transmission line and a return line.

[0086] In an embodiment in which the first and second conductors are braided or wound into multiple bundles, one or more of the bundles forming the first and second conductors may be used together as a transmission line, while one or more other bundles forming the first and second conductors may be used together as a return line. In this manner, the transmission line and the return line may be integrated into the same capacitive cable. This embodiment is preferred because it may facilitate easier installation of the cable at the installation site compared to providing the transmission line and the return line in separate cables. In this embodiment, the capacitive cable may preferably include at least four conductor bundles.

[0087] In embodiments where the capacitive cable is used as a three-phase capacitive cable, it may not be necessary to provide a separate return conductor from the transmission line. This may be because only one of the three phases of the transmission line may be active and transmitting power at any given time, allowing one or both of the other two phases to be used as the return conductor at that time. This configuration may be advantageous because it requires less material to manufacture the cable than if the transmission line and return conductor were separate from each other.

[0088] According to a third aspect of the present invention, (i) a first plurality of conductors of a first capacitive cable are connected to a power source (but not to a load); (ii) a second plurality of conductors of the first capacitive cable are connected to a load (but not to a power source); (iii) a first plurality of conductors of the second capacitive cable are connected to a power source (but not to a load); (iv) There is provided the use of a first capacitive cable according to the first aspect of the invention and a second capacitive cable according to the first aspect of the invention in a power transmission system, wherein a second plurality of conductors of the second capacitive cable are connected to a load (but not to a power source).

[0089] The cable can be used to transmit power at high frequencies.

[0090] A first capacitive cable may be used as the transmission line and a second capacitive cable may be used as the return line. Using the second capacitive cable as the return line rather than a ground, conventional cable, or conductive screen may further help improve the balance between the transmission line and the return line when power is transmitted along them, as the two capacitive cables have very similar reactances and resistances. In such a system, using two capacitive cables that are substantially identical to each other may further improve the balance between the transmission line and the return line when power is transmitted along them, as the cables may have nearly the same, if not exactly the same, reactance and / or resistance.

[0091] As used herein, the term "balance" is intended to refer to the ratio of (i) the impedance of the transmission line relative to the flow of current to (ii) the impedance of the return line relative to the flow of current. A system described as "balanced" is intended to mean a system in which the impedance of the transmission line is substantially equal to the impedance of the return line, and an "unbalanced" system is intended to mean a system in which the difference between these impedances is relatively large. It will be understood that a balanced system generally transfers power more efficiently than an unbalanced system. Perfect balance is an optimal result because it can maximize the efficiency of the power transfer system by eliminating voltage losses due to imbalance. While perfect balance (or near-perfect balance) can be achieved in most preferred embodiments of the present invention, it is expected that many embodiments will instead achieve very good balance.

[0092] The first capacitive cable and the second capacitive cable may be braided or wound around each other. Wrapping the two cables around each other in this manner may have several advantages. For example, electric and magnetic fields generated by the cables may be reduced, improving the safety and efficiency of the power transmission system. Furthermore, in embodiments in which the first and second capacitive cables are not braided or wound around each other, there is a risk that the electric and magnetic fields generated by one of the cables may interfere with the power transmission of the other cable. This interference between the cables is known as "crosstalk" and reduces the efficiency of the system. Braiding / wrapping the two cables around each other may reduce crosstalk between the two cables, thereby improving the efficiency of the system compared to embodiments that do not employ such braiding / wrapping. Furthermore, braiding / wrapping the two cables around each other in this manner may reduce the system's susceptibility to electric and magnetic fields generated by external electromagnetic field sources in the vicinity of one or both of the cables, i.e., electromagnetic field sources that are not part of the system.

[0093] According to a fourth aspect of the present invention, (a) connecting a first plurality of conductors of a capacitive cable according to the first aspect of the present invention to a power source (but not to a load); (b) connecting the second plurality of conductors of the capacitive cable according to the first aspect of the present invention to a load (but not to a power source); (c) activating the power supply; A power transfer method is provided, comprising:

[0094] Activating the power supply in this context may be accomplished by switching the power supply on.

[0095] The method may be a method of transmitting power at high frequency.

[0096] In view of the advantages of using the capacitive cable of the present invention detailed above, it will be appreciated that by transmitting power, i.e., transmitting or conducting electricity (in the form of alternating current), in this manner, highly efficient transmission of that power may be achieved, and thus this power / electricity transmission method may be advantageous over prior art power / electricity transmission methods.

[0097] According to a fifth aspect of the present invention, (a) a first conductor for connection to a power source; (b) a second conductor for connection to a load; (c) a dielectric material between the first conductor and the second conductor; A capacitive cable comprising: Each conductor is optionally individually insulated, A capacitive cable is provided in which at least one of the conductors transitions between the outside and the inside of the cable.

[0098] According to a sixth aspect of the present invention, (a) a first conductor for connection to a power source; (b) a second conductor for connection to a load; (c) a dielectric material between the first conductor and the second conductor; A Litz wire or cable is provided comprising:

[0099] Additionally, in all aspects of the present invention, it should be understood that the capacitive cable may further comprise an outer sheath, the purpose of which is to (i) protect the internal components of the cable from the surrounding environment and (ii) hold the internal components of the cable in place within the cable. [Example]

[0100] The present invention will now be described by way of the following examples with reference to the accompanying drawings.

[0101] Example 1 - Bundle Referring to FIG. 1, a bundle 1 of the present invention comprises a plurality of conductors 2 braided / wound around each other, with each individual conductor repeatedly transitioning between the outside of the bundle and the inside of the bundle along the length of the bundle.

[0102] The proportion of the bundle length that each conductor is outside the bundle is similar between conductors, and each conductor is individually insulated from all other conductors in the bundle (insulation omitted from Figure 1).

[0103] Example 2 - Low Resistance Capacitive Cable with One Bundle 2 and 3, capacitive cable 3 comprises a first plurality of conductors 4 and a second plurality of conductors 5 braided / wound around each other into a single bundle 1. The single bundle is radially surrounded by an outer sheath 6 that protects the bundle from the surrounding environment.

[0104] Each conductor of the first and second pluralities of conductors is individually insulated with a dielectric material (omitted from Figures 2 and 3) such that, during use of the capacitive cable, a capacitive relationship exists between the first and second pluralities of conductors along the length of the capacitive cable.

[0105] Example 3 - Low Resistance Capacitive Cable with Two Radially Aligned Bundles Referring to FIG. 4, the capacitive cable 3 comprises a first plurality of conductors 4 braided / wound into a first bundle and a second plurality of conductors 5 braided / wound into a second bundle.

[0106] A first plurality of conductor bundles is located at the center of the cable (when the cable is viewed in cross section from one end of the cable) and is radially surrounded by a layer of dielectric material 7. Radially outward of the dielectric material, a second plurality of conductor bundles is positioned to wrap around the layer of dielectric material, and an outer sheath 6 further wraps around the other components of the cable to protect the internal components of the cable from the surrounding environment.

[0107] Both the first and second plurality of conductors are braided / wound such that the bundles formed by each of these conductors are in the form of a Litz wire.

[0108] Each conductor is individually insulated from all other conductors (insulation is omitted from Figure 4). This arrangement is such that a capacitive relationship exists between the first and second bundles when the first plurality of conductors is connected to a power source but not to a load and the second plurality of conductors is connected to a load but not to a power source, i.e., when the capacitive cable is being used to transfer power from a power source to a load.

[0109] The two bundles are arranged such that the second plurality of conductors is radially outward of the first plurality of conductors when the cable is viewed in cross section from one end of the cable.

[0110] Example 4 - Low Resistance Capacitive Cable with Two Side-by-Side Bundles Referring to Figure 5, capacitive cable 3 comprises a first plurality of conductors 4 braided / wound into a first bundle and a second plurality of conductors 5 braided / wound into a second bundle. Each bundle is radially surrounded by a layer of dielectric material 7. An outer sheath 6 is wrapped around these components of the cable to protect the internal components of the cable from the surrounding environment.

[0111] Each conductor is individually insulated from all other conductors (insulation is omitted from Figure 5). This arrangement is such that a capacitive relationship exists between the first and second bundles when the first plurality of conductors is connected to a power source but not to a load and the second plurality of conductors is connected to a load but not to a power source, i.e., when the capacitive cable is being used to transfer power from a power source to a load.

[0112] The two bundles are arranged such that the second plurality of conductors is adjacent to the first plurality of conductors when the cable is viewed in cross section from one end of the cable.

[0113] Example 5 - Low Resistance Capacitive Cable with Two Types of Multiple Bundles Side-by-Side Referring to Figure 6, capacitive cable 3 comprises a first plurality of conductors 4 braided / wound into a first plurality of bundles, and a second plurality of conductors 5 braided / wound into a second plurality of bundles. Each conductor is individually insulated from all other conductors (insulation is omitted from Figure 6). Furthermore, each bundle is radially surrounded by a layer of dielectric material 7.

[0114] The first and second pluralities of bundles are concentrically arranged around the forming portion 8 so that the forming portion is located at the center of the cable (when the cable is viewed in cross section from one end of the cable). The outer sheath 6 is positioned around the outside of the other parts of the cable to protect them from the environment and to hold the other parts of the cable in place.

[0115] It will be appreciated that this capacitive cable, when used in a power transmission system, is particularly suited to transmitting power in a three-phase manner because it includes six conductor bundles (three bundles formed by / from the first plurality of conductors and three bundles formed by / from the second plurality of conductors). These six conductor bundles can be connected into three pairs of bundles (each pair including one bundle of the first plurality of conductors and one bundle of the second plurality of conductors), each pair being used to transmit one phase of the transmitted power. In this manner, when the capacitive cable is used to transmit power, a capacitive relationship exists between the two bundles of each pair, and each pair of bundles can be considered a capacitive sub-cable.

[0116] Example 6 - Low Resistance Capacitive Cable with Conductive Screen Referring to Figure 7, capacitive cable 3 comprises a first plurality of conductors 4 and a second plurality of conductors 5 braided / wound into a single bundle. Each conductor is individually insulated from the other conductors in the bundle using a dielectric material (not shown in Figure 7). The bundle is radially surrounded by a layer of insulation 9, which is further radially surrounded by a conductive screen 10. Radially outward of the conductive screen is a protective outer sheath 6.

[0117] In this capacitive cable, the conductive screen comprises multiple conductors (omitted in FIG. 7) braided / wound around each other such that the conductive screen is formed of Litz wire.

[0118] Example 7 - Low Resistance Capacitive Cable with Bundles Arranged into Two Radially Aligned Capacitive Sub-Cables 8, capacitive cable 3 comprises a first plurality of conductors braided / wound into first and second bundles 4a and 4b, and a second plurality of conductors braided / wound into third and fourth bundles 5a and 5b. The individual conductors are omitted from FIG. 8.

[0119] The first bundle 4a is located at the center of the cable (when viewed in cross section from one end of the cable) and is radially surrounded by a layer of dielectric material 7a. Radially outward from the dielectric material, a third bundle 5a is positioned so as to wrap around the layer of dielectric material. Together, the first and third bundles, with the dielectric material between them, form the first capacitive sub-cable 3a.

[0120] A layer of insulation 9 is wrapped around the first sub-cable 3a, thereby separating it from the second sub-cable 3b.

[0121] The layer of insulation is wrapped around a second bundle 4b, which is further surrounded by a layer of dielectric material 7b. Radially outward from the layer of dielectric material 7b is a fourth bundle 5b. Together, the second and fourth bundles, with the dielectric material disposed between them, form a second capacitive sub-cable 3b.

[0122] An outer sheath 6 protects the internal components of the cable from the surrounding environment by wrapping around all other components of the cable.

[0123] Both the first plurality of conductors and the second plurality of conductors are braided / wound such that the four bundles formed by these conductors are in the form of a Litz wire.

[0124] Each conductor is individually insulated from all other conductors (insulation is omitted from Figure 8). This arrangement is such that when the first plurality of conductors is connected to a power source but not to a load and the second plurality of conductors is connected to a load but not to a power source, i.e., when the capacitive cable is being used to transmit power, a capacitive relationship exists between the first and third bundles and between the second and fourth bundles.

[0125] By including two sub-cables 3a and 3b in the capacitive cable 3, when the capacitive cable 3 is used in a power transmission system, one sub-cable can be used as a transmission line and the other sub-cable can be used as a return line. Thus, the transmission line and return line of the power transmission system are integrated in this way to be the same capacitive cable 3.

[0126] The two sub-cables are arranged such that the second sub-cable 3b is radially outward of the first sub-cable 3a when the cable is viewed in cross section from one end thereof.

[0127] Example 8 - A low resistance capacitive cable having a bundle arranged as two side-by-side capacitive sub-cables, with each sub-cable bundle arranged vertically side-by-side. 9, capacitive cable 3 comprises a first plurality of conductors braided / wound into first and second bundles 4a and 4b, and a second plurality of conductors braided / wound into third and fourth bundles 5a and 5b. The individual conductors are omitted from FIG. 9.

[0128] The four bundles are arranged around the periphery of the forming portion 8 .

[0129] The first bundle 4a and the third bundle 5a are each radially surrounded by a layer of dielectric material 7a, and the first bundle 4a and the third bundle 5a and their respective layers of dielectric material 7a are arranged side-by-side to form the first capacitive sub-cable 3a (shown by the dashed line in FIG. 9).

[0130] The second bundle 4b and the fourth bundle 5b are each radially surrounded by a layer of dielectric material 7b. The first bundle 4b and the third bundle 5b and their respective layers of dielectric material 7b are arranged side-by-side to form the second capacitive sub-cable 3b (shown by the dotted line in FIG. 9).

[0131] The first sub-cable 3 a and the second sub-cable 3 b are arranged side by side in the vertical direction within the capacitive cable 3 .

[0132] A layer of insulation (omitted from FIG. 9) wraps around the first sub-cable 3a and the second sub-cable 3b, thereby separating the two sub-cables from the conductive screen 10 that radially surrounds the sub-cables 3a and 3b.

[0133] An outer sheath 6 protects the internal components of the cable from the surrounding environment by wrapping around all other components of the cable.

[0134] Each conductor is individually insulated from all other conductors (insulation is omitted from Figure 9). This arrangement is such that when the first plurality of conductors is connected to a power source but not to a load and the second plurality of conductors is connected to a load but not to a power source, i.e., when the capacitive cable is being used to transmit power, a capacitive relationship exists between the first and third bundles and between the second and fourth bundles.

[0135] By including two sub-cables 3a and 3b within the capacitive cable 3, when the capacitive cable 3 is used in a power transmission system, one sub-cable may be used as a transmission line and the other sub-cable as a return line. Thus, the transmission line and return line of the power transmission system are integrated in this way into the same capacitive cable 3. It will be appreciated that a conductive screen may alternatively be used as the return line.

[0136] Example 9 - A low resistance capacitive cable having bundles arranged as two side-by-side capacitive sub-cables, with each sub-cable bundle arranged diagonally side-by-side. 10, capacitive cable 3 comprises a first plurality of conductors braided / wound into first and second bundles 4a and 4b, and a second plurality of conductors braided / wound into third and fourth bundles 5a and 5b. The individual conductors are omitted from FIG. 10.

[0137] The four bundles are arranged around the periphery of the forming portion 8 .

[0138] The first bundle 4a and the third bundle 5a are each radially surrounded by a layer of dielectric material 7a, and the first bundle 4a and the third bundle 5a and their respective layers of dielectric material 7a are arranged side by side to form the first capacitive sub-cable 3a (shown by the dashed line in FIG. 10).

[0139] The second bundle 4b and the fourth bundle 5b are each radially surrounded by a layer of dielectric material 7b. The first bundle 4b and the third bundle 5b and their respective layers of dielectric material 7b are arranged side-by-side to form the second capacitive sub-cable 3b (shown by the dotted line in FIG. 10).

[0140] The first sub-cable 3a and the second sub-cable 3b are arranged diagonally side by side within the capacitive cable 3.

[0141] A layer of insulation (omitted from FIG. 10) wraps around the first sub-cable 3a and the second sub-cable 3b, thereby separating the two sub-cables from the conductive screen 10 that radially surrounds the sub-cables 3a and 3b.

[0142] An outer sheath 6 protects the internal components of the cable from the surrounding environment by wrapping around all other components of the cable.

[0143] Each conductor is individually insulated from all other conductors (insulation is omitted from FIG. 10). This arrangement is such that when the first plurality of conductors is connected to a power source but not to a load and the second plurality of conductors is connected to a load but not to a power source, i.e., when the capacitive cable is being used to transmit power, a capacitive relationship exists between the first and third bundles and between the second and fourth bundles.

[0144] By including two sub-cables 3a and 3b within the capacitive cable 3, when the capacitive cable 3 is used in a power transmission system, one sub-cable can be used as a transmission line and the other sub-cable can be used as a return line. Thus, the transmission line and return line of the power transmission system are integrated in this way into the same capacitive cable 3. It will be appreciated that a conductive screen may alternatively be used as the return line.

[0145] Example 10 - Transmission and return lines integrated side-by-side into the same capacitive cable 11, capacitive cable 3 comprises a first plurality of conductors 4 braided / wound into bundles of four, and a second plurality of conductors 5 braided / wound into bundles of four. The individual conductors are omitted from FIG. 11.

[0146] The eight conductor bundles are arranged within capacitive cable 3 into four adjacent / spaced sub-cables (one such sub-cable is shown in dashed lines in FIG. 11 ). Each sub-cable comprises one of four bundles formed by a first plurality of conductors, located at the center of the respective sub-cable (when viewed in cross section from one end thereof). The bundle is radially surrounded by a layer of dielectric material 7, which is in turn radially surrounded by one of four bundles formed by a second plurality of conductors. Each sub-cable further comprises a layer of insulator 9 as its radially outermost layer, thereby electrically isolating the sub-cable from the other three sub-cables.

[0147] The four sub-cables are arranged in an annular fashion around the forming portion 8 and are collectively radially surrounded by a conductive screen 10. All these components of the capacitive cable are collectively enclosed within an outer sheath 6 which protects the internal components of the cable from the surrounding environment.

[0148] Each conductor is individually insulated from all other conductors (insulation is omitted in Figure 11). This arrangement is such that a capacitive relationship exists between the two conductor bundles within each sub-cable when the first plurality of conductors is connected to a power source but not to a load and the second plurality of conductors is connected to a load but not to a power source, i.e., when the capacitive cable is being used to transmit power.

[0149] By including four sub-cables within the capacitive cable 3, when the capacitive cable 3 is used in a power transmission system, one or more of the sub-cables may be used as a transmission line and one or more of the sub-cables may be used as a return line. Thus, the transmission line and return line of the power transmission system are integrated in this manner into the same capacitive cable 3. It will be appreciated that a conductive screen may alternatively be used as the return line.

[0150] Example 11 - Transmission and return lines integrated side-by-side into the same capacitive cable 12, capacitive cable 3 comprises a first plurality of conductors 4 braided / wound into bundles of six, and a second plurality of conductors 5 braided / wound into bundles of six. The individual conductors are omitted from FIG. 12.

[0151] The 12 conductor bundles are arranged within the capacitive cable 3 into six adjacent / spaced sub-cables (one such sub-cable is shown in dashed lines in FIG. 12). Each sub-cable comprises one of six bundles formed by the first plurality of conductors, located at the center of the respective sub-cable (when viewed in cross section from one end thereof). The bundle is radially surrounded by a layer of dielectric material 7, which is further radially surrounded by one of six bundles formed by the second plurality of conductors. Each sub-cable further comprises a layer of insulator 9 as its radially outermost layer, thereby electrically isolating the sub-cable from the other five sub-cables.

[0152] The six sub-cables are arranged in a ring shape around the forming portion 8 and are collectively radially surrounded by a conductive screen 10. All these components of the capacitive cable are collectively enclosed within an outer sheath 6 which protects the internal components of the cable from the surrounding environment.

[0153] Each conductor is individually insulated from all other conductors (insulation is omitted from Figure 12). This arrangement is such that a capacitive relationship exists between the two conductor bundles within each sub-cable when the first plurality of conductors is connected to a power source but not to a load and the second plurality of conductors is connected to a load but not to a power source, i.e., when the capacitive cable is being used to transmit power.

[0154] By including six sub-cables within the capacitive cable 3, when the capacitive cable 3 is used in a power transmission system, one or more of the sub-cables may be used as a transmission line and one or more of the sub-cables may be used as a return line. Thus, the transmission line and return line of the power transmission system are integrated in this manner into the same capacitive cable 3. It will be appreciated that a conductive screen may alternatively be used as the return line.

[0155] Because capacitive cable 3 has six sub-cables, it is particularly suitable for transmitting power in a three-phase manner, i.e., by connecting the six sub-cables as three pairs of sub-cables, with each pair being used to transmit one of the three phases. To maximize the balance between the different pairs of sub-cables, the sub-cables may be connected in pairs (two sub-cables per phase) to each phase of a three-phase power supply, such that (when viewed in cross section from one end of the sub-cables) the distance between the centers of the two sub-cables of each pair is the same.

[0156] Example 12 - Use of one capacitive cable in a power transfer system 13, a capacitive cable 3 is used to transmit power from a power source 11 to a load 12. The capacitive cable is used as a transmission line by connecting a first plurality of conductors 4 of the capacitive cable to the power source and a second plurality of conductors 5 of the capacitive cable to the load. A layer of dielectric material 7 is located between the first and second plurality of conductors to ensure a capacitive relationship exists between the conductors when the power source is activated.

[0157] To ensure that the circuit formed is a complete circuit, before the power supply is turned on, both the power supply and the load are connected to ground 13 which acts as a return for the circuit.

[0158] In this manner, power is efficiently transferred from the power source to the load via the power transfer system 14 .

[0159] Example 13 - Use of one capacitive cable in a power transfer system 14, a capacitive cable 3 is used to transmit power from a power source 11 to a load 12. The capacitive cable is used as a transmission line by connecting a first plurality of conductors 4 of the capacitive cable to the power source and a second plurality of conductors 5 of the capacitive cable to the load. A layer of dielectric material 7 is located between the first and second plurality of conductors to ensure a capacitive relationship exists between the conductors when the power source is activated.

[0160] To ensure that the circuit formed is a complete circuit, before the power supply is turned on, both the power supply and the load are connected to a conventional cable 15 which acts as a return for the circuit. The conventional cable comprises multiple conductors 16 connected to both the power supply and the load.

[0161] In this manner, power is efficiently transferred from the power source to the load via the power transfer system 14 .

[0162] Example 14 - Use of two capacitive cables in a power transfer system 15, two capacitive cables 3 are used in a power transfer system 14. A first plurality of conductors 4 of each cable are connected to a power source 11, and a second plurality of conductors 5 of each cable are connected to a load 12.

[0163] The dielectric material 7 between the first and second plurality of conductors ensures that a capacitive relationship is established between these plurality of conductors when the power transfer system is activated and transferring power from the source to the load.

[0164] When the power supply is turned on, power is transmitted to the load via a first capacitive cable acting as a transmission line. The load uses a certain amount of the supplied power, and the remaining power is returned to the power supply via a second capacitive cable acting as a return line.

[0165] Example 15 - Fabrication of a Low Resistance Capacitive Cable Referring to FIG. 16, a capacitive cable 3 was fabricated having the following structure radially outward from the center toward the outer periphery (when the cable is viewed in cross section from one end thereof). a first plurality of conductors 4 (individual conductors omitted from FIG. 16) 9 layers of insulator Layer of dielectric material 7 Second plurality of conductors 5 (omitted for individual conductors 16) Further layer of insulator 9 Outer sheath 6

[0166] A first plurality of 1600 copper conductors were individually insulated with solderable enamel (insulation omitted from Figure 16) and braided / wound into a bundle at the center of the cable (when the cable is viewed in cross section from one end as in Figure 16). Each insulated conductor had a diameter of 0.1 mm (0.108 mm to 0.117 mm including insulation), and the total cross-sectional area of ​​the first plurality of conductors was 12.57 mm. 2 It was.

[0167] A layer of insulation was formed by spirally wrapping polyethylene terephthalate ("PET") separator tape around the radially outer side of the first plurality of conductors. The insulation was 23 μm thick and had grooves (not shown in FIG. 16 ) along its inner (radially inner) surface that corresponded to the conductor arrangement of the first plurality of conductors. The grooves allowed the insulation to fit snugly against the first plurality of conductors, holding them in place within the bundle.

[0168] The next layer, radially outward of the insulator, was a layer of PA12L25W20Y (grade 12 nylon) dielectric material, with a thickness of 0.3 mm. A second plurality of copper conductors, each consisting of 1620 copper conductors individually insulated with solderable enamel (insulation omitted from Figure 16), was braided / wound into a bundle around the layer of dielectric material. Each insulated conductor had a diameter of 0.1 mm (0.108 mm to 0.117 mm including insulation); thus, like the first plurality of conductors, the second plurality of conductors had a total cross-sectional area of ​​12.72 mm. 2 It was.

[0169] In both the first and second pluralities of conductors, the conductors were each braided / wound to form a Litz wire.

[0170] Radially outward of the second plurality of conductors, a further layer of insulation was placed around the second plurality of conductors using a spirally wrapped polyethylene terephthalate ("PET") separator tape. This layer of insulation was 23 μm thick and, like the layer of insulation radially adjacent to the first plurality of conductors, had retaining grooves (omitted from FIG. 16 ) along its inner surface to hold the second plurality of conductors in place within the bundle.

[0171] The cable components were radially surrounded by an outer sheath made of low-density polyethylene and had a thickness of 1.25 mm.

[0172] The resulting diameter of the completed cable was 10mm to 11mm.

[0173] Example 16 - Use of two capacitive cables from Example 15 Referring to FIG. 16, similarly to the capacitive cable of Example 15, two capacitive cables 3 were fabricated.

[0174] These capacitive cables were used in a power transfer system in which a first plurality of conductors of each cable was connected to a power source but not to a load, and a second plurality of conductors of each cable was connected to a load but not to a power source, thus using one cable as a transmission line and the other cable as a return line (similar to that shown in FIG. 15).

[0175] In this system, the power supply provided power with a voltage of 900 V to 1 kV, a current of 17 A to 19 A, and a frequency of 85.22 kHz. The length of each capacitive cable was 107 m.

[0176] Measurements of the inherent electrical properties of the capacitive cables at 85kHz to 85.5kHz (the resonant frequency of two capacitive cables connected in series) showed that the inductance of these cables was 0.23458mH / km, the capacitance was 326.17nF / km (the active capacitance value at 85kHz to 85.5kHz when two cables are capacitively connected in series), and the resistance was 740.6mΩ / km (captured / measured during factory acceptance testing). The dielectric constant of the Grade 12 nylon used as the dielectric layer of each cable was 8.8 (according to the datasheet).

[0177] When this power transmission system was operated, the voltage loss along the length of the cable was found to be 63.32 V. Therefore, high frequency power could be transmitted efficiently through this power transmission system.

[0178] Example 17 - Use of two capacitive cables of Example 15 braided / wrapped around each other Referring to FIG. 17, similarly to the capacitive cable of Example 15, two capacitive cables 3 are fabricated and used in a power transmission system.

[0179] The two capacitive cables are braided / wound around each other, reducing the electric and magnetic fields generated by the cables compared to a power transfer system in which the capacitive cables are not braided / wound around each other.

[0180] Example 18 - Comparison of a Low-Resistance Capacitive Cable and a Low-Resistance Conventional Cable Having Similar Structures Referring to FIG. 16, similarly to the capacitive cable of Example 15, two capacitive cables 3 were fabricated.

[0181] These capacitive cables were used in a power transmission system in which a first plurality of conductors of each cable was connected to a power source but not to a load, and a second plurality of conductors of each cable was connected to a load but not to a power source. Thus, in this power transmission system, one cable was used as a transmission line and the other cable was used as a return line (similar to that shown in FIG. 15). It will be appreciated that in this power transmission system, two capacitive cables can accurately be described as being connected in series with each other. The cables were placed next to each other so that their outer sheaths touched each other along their lengths.

[0182] The capacitive cables were initially manufactured with a length of 130 m each. The lengths of the two cables were then gradually shortened, and the resonant frequencies of the two cables connected in series with each other during use were measured with varying cable lengths. Other electrical parameters were not changed. The relevant data obtained are shown in Table 1.

[0183] [Table 1]

[0184] From Table 1, it can be seen that a resonant frequency of approximately 85 kHz was achieved when each cable was 107 m long. It will be appreciated that a cable capable of operating at a resonant frequency of 85 kHz is advantageous because this is a resonant frequency recognized by industry standards relevant to many high-frequency applications, such as wireless electric vehicle charging systems. It will also be appreciated that a resonant frequency of 85 kHz can be achieved using cables having lengths other than 107 m, for example, by modifying the dimensions / structure of the capacitive cable, e.g., the type and / or thickness of the dielectric material used, the topology and / or shape of the conductors, and / or by connecting one or more additional electrical components, such as capacitors and / or inductors, to the circuit.

[0185] Next, a test was conducted to compare the efficiency of a 107-meter-long cable when used as a capacitive cable with that when used as a conventional cable with a similar structure at transmitting power at a resonant frequency of approximately 85 kHz. To conduct this test, the cables were first connected as capacitive cables, i.e., the first plurality of conductors of each cable were connected to a power source but not to a load, and the second plurality of conductors of each cable were connected to a load but not to a power source. The first and second plurality of conductors were then directly electrically connected to each other at each end of the cable, causing each cable to transmit power as a conventional cable rather than a capacitive cable. Various electrical parameters and characteristics of the cable were measured when used as a capacitive cable, and then the same electrical parameters were measured again when used as a conventional cable. In this manner, a direct comparison was made between two capacitive cables of the present invention and two conventional cables with similar structures.

[0186] The first electrical parameter compared between the capacitive cable and the conventional cable was the harmonic content at the input terminals of the cable during operation. The relevant data obtained are shown in Tables 2 and 3. Table 2 shows the data on the voltage-induced total harmonic distortion, and Table 3 shows the data on the current-induced total harmonic distortion.

[0187] [Table 2]

[0188] [Table 3]

[0189] Tables 2 and 3 show that when the cable functions as a capacitive cable, it has lower voltage-induced total harmonic distortion and lower current-induced total harmonic distortion compared to a conventional cable. These data therefore demonstrate that the capacitive cable of the present invention provides improved harmonic filtration compared to a conventional cable of similar construction. The second electrical parameter compared between the capacitive and conventional cables was the voltage drop / loss along the length of the cable. Measurements were taken at 3 minutes 50 seconds (230 seconds) after the start of operation and again at 22 minutes 27 seconds (1347 seconds) after the start of operation. The relevant data obtained are shown in Table 4.

[0190] [Table 4]

[0191] This experiment was repeated using different input voltages and measurements at different times. Specifically, the input voltage was controlled to be approximately the same for both the capacitive cable and the conventional cable at the corresponding time. The relevant data obtained are shown in Table 5.

[0192] [Table 5]

[0193] From Tables 4 and 5, it can be seen that the capacitive cable has less voltage loss along its length than the conventional cable.

[0194] This experiment was repeated again using different input voltages and measuring at different time points. In this repetition, the input voltage was controlled so that the output voltage was the same for both the capacitive cable and the conventional cable at the corresponding time points. The relevant data obtained are shown in Table 6.

[0195] [Table 6]

[0196] From Table 6, we can see that the capacitive cable has less voltage loss along its length than the conventional cable, which means that the same output voltage can be achieved with a lower input voltage (for the capacitive cable compared to the conventional cable), making the capacitive cable more efficient than the conventional cable.

[0197] All experiments were performed using a single-phase power supply and therefore using the cable as a single-phase cable. [Explanation of symbols]

[0198] (Explanation of symbols) 1 bunch 2 conductors 3 Capacitive Cable 4. First Plurality of Conductors 5 Second plurality of conductors 6. Outer sheath 7. Dielectric Materials 8 Formation part 9. Insulators 10 Conductive Screen 11 Power supply 12 Load 13 Grounding 14 Power Transmission Systems 15 Conventional cable 16 Conductor of conventional cable

Claims

1. (a) a first plurality of conductors for connection to a power source; (b) a second plurality of conductors for connection to a load; (c) a dielectric material between the first plurality of conductors and the second plurality of conductors; A capacitive cable comprising: Each conductor is individually insulated, a capacitive cable, wherein at least one conductor of the first plurality of conductors and at least one conductor of the second plurality of conductors are braided or wound into one or more bundles, each individual conductor repeatedly transitioning between the outside of the one or more bundles and the inside of the one or more bundles along the length of the one or more bundles.

2. 10. The capacitive cable of claim 1, wherein all of the conductors are braided or wound into the one or more bundles.

3. 3. The capacitive cable of claim 1, wherein the proportion of the length of each conductor outside the bundle is similar or identical between the conductors.

4. 4. The capacitive cable of claim 1, wherein the conductors are braided or wound into a bundle, and each conductor is individually insulated with a dielectric material.

5. 4. A capacitive cable according to claim 1, wherein the conductors are braided or wound into multiple bundles.

6. 6. The capacitive cable of claim 5, wherein the first plurality of conductors are braided or wound into a first bundle and the second plurality of conductors are braided or wound into a second bundle.

7. 6. The capacitive cable of claim 5, wherein the first plurality of conductors are braided or wound into a first plurality of bundles and the second plurality of conductors are braided or wound into a second plurality of bundles.

8. The capacitive cable of claim 7 , wherein the first plurality of bundles and the second plurality of bundles are arranged in one or more concentric bundles.

9. 9. A capacitive cable according to any one of claims 1 to 8, wherein each bundle is a Litz wire.

10. The capacitive cable of claim 1 , wherein the capacitive cable further comprises a conductive screen.

11. 11. The capacitive cable of claim 10, wherein the conductive screen is for connection as a return wire.

12. 12. A capacitive cable according to claim 10 or claim 11, wherein the conductive screen is a litz wire.

13. 13. A capacitive cable according to any one of claims 1 to 12 for connection as both a transmission line and a return line.

14. 14. The capacitive cable of claim 1, wherein insulation of the first plurality of conductors has a different color than insulation of the second plurality of conductors.

15. 15. The capacitive cable of claim 1, wherein the bundles are arranged to form two or more capacitive sub-cables within the capacitive cable.

16. 16. The capacitive cable of claim 1, wherein the first plurality of conductors are connected to each other at a first end of the capacitive cable and the second plurality of conductors are connected to each other at a second end of the capacitive cable.

17. 17. The capacitive cable of claim 1, wherein the capacitive cable is a three-phase capacitive cable.

18. Use of a capacitive cable according to any one of claims 1 to 17 in a power transmission system, comprising: (i) the first plurality of conductors are connected to the power source but not to the load; (ii) Use of a capacitive cable, wherein the second plurality of conductors are connected to the load but not to the power source.

19. 20. The use of a capacitive cable according to claim 18, wherein the first and second plurality of conductors are used together as a transmission line and the conductive screen is used as a return line.

20. Use of a first capacitive cable according to any one of claims 1 to 17 and a second capacitive cable according to any one of claims 1 to 17 in a power transmission system, comprising: (i) the first plurality of conductors of the first capacitive cable are connected to the power source but not to the load; (ii) the second plurality of conductors of the first capacitive cable are connected to the load but not to the power source; (iii) the first plurality of conductors of the second capacitive cable are connected to the power source but not to the load; (iv) Use of a first capacitive cable and a second capacitive cable, wherein the second plurality of conductors of the second capacitive cable are connected to the load but not to the power source.

21. 21. The use of a first capacitive cable and a second capacitive cable according to claim 20, wherein the first capacitive cable is used as a transmission line and the second capacitive cable is used as a return line.

22. 22. Use of a first capacitive cable and a second capacitive cable according to claim 20 or claim 21, wherein the first capacitive cable and the second capacitive cable are braided or wound around each other.

23. A power transmission method, comprising: (a) connecting the first plurality of conductors of the capacitive cable of any one of claims 1 to 17 to the power source but not to the load; (b) connecting the second plurality of conductors of the capacitive cable of any one of claims 1 to 17 to the load but not to the power source; (c) activating the power supply; A method comprising:

24. (a) a first plurality of conductors for connection to a power source but not for connection to a load; (b) a second plurality of conductors for connection to the load but not for connection to the power source; (c) a third plurality of conductors for connection to the power source but not for connection to the load; (d) a fourth plurality of conductors for connection to the load but not for connection to the power source; (e) a dielectric material between the first plurality of conductors and the second plurality of conductors; (f) a dielectric material between the third plurality of conductors and the fourth plurality of conductors; A capacitive cable comprising: the first plurality of conductors and the second plurality of conductors are collectively connected as a transmission line; the third plurality of conductors and the fourth plurality of conductors are for connection together as a return line; Each conductor is individually insulated, a capacitive cable, wherein at least one conductor of the first plurality of conductors, at least one conductor of the second plurality of conductors, at least one conductor of the third plurality of conductors, and at least one conductor of the fourth plurality of conductors are braided or wound into one or more bundles, each individual conductor repeatedly transitioning between the outside of the one or more bundles and the inside of the one or more bundles along the length of the one or more bundles.

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