WO2018190729A1 - Régulation thermique dans des structures de couplage par transfert de puissance inductive - Google Patents

Régulation thermique dans des structures de couplage par transfert de puissance inductive Download PDF

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Publication number
WO2018190729A1
WO2018190729A1 PCT/NZ2018/050048 NZ2018050048W WO2018190729A1 WO 2018190729 A1 WO2018190729 A1 WO 2018190729A1 NZ 2018050048 W NZ2018050048 W NZ 2018050048W WO 2018190729 A1 WO2018190729 A1 WO 2018190729A1
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WO
WIPO (PCT)
Prior art keywords
heat
coil
transfer means
heat transfer
electric vehicle
Prior art date
Application number
PCT/NZ2018/050048
Other languages
English (en)
Inventor
John Talbot Boys
Grant Anthony Covic
Dr Simon BICKERTON
Matthew Paul BATTLEY
Ahmad Bilal
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Auckland Uniservices Limited
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Application filed by Auckland Uniservices Limited filed Critical Auckland Uniservices Limited
Publication of WO2018190729A1 publication Critical patent/WO2018190729A1/fr

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F38/00—Adaptations of transformers or inductances for specific applications or functions
    • H01F38/14—Inductive couplings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/08—Cooling; Ventilating
    • H01F27/10—Liquid cooling
    • H01F27/18—Liquid cooling by evaporating liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/08—Cooling; Ventilating
    • H01F27/22—Cooling by heat conduction through solid or powdered fillings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/34—Special means for preventing or reducing unwanted electric or magnetic effects, e.g. no-load losses, reactive currents, harmonics, oscillations, leakage fields
    • H01F27/36—Electric or magnetic shields or screens
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/34—Special means for preventing or reducing unwanted electric or magnetic effects, e.g. no-load losses, reactive currents, harmonics, oscillations, leakage fields
    • H01F27/36—Electric or magnetic shields or screens
    • H01F27/363—Electric or magnetic shields or screens made of electrically conductive material
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J50/00—Circuit arrangements or systems for wireless supply or distribution of electric power
    • H02J50/10—Circuit arrangements or systems for wireless supply or distribution of electric power using inductive coupling
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J50/00—Circuit arrangements or systems for wireless supply or distribution of electric power
    • H02J50/70—Circuit arrangements or systems for wireless supply or distribution of electric power involving the reduction of electric, magnetic or electromagnetic leakage fields
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0042—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries characterised by the mechanical construction

Definitions

  • the technical field relates generally to wireless power transfer, and more specifically to devices, systems, and methods related to wireless power transfer. More particularly, the present disclosure relates to magnetic coupling structures and winding arrangements used in wireless power transfer systems, and in particular inductive power transfer (IPT) systems.
  • IPT inductive power transfer
  • Remote systems such as personal electronic devices or vehicles, have been introduced that include power derived from electricity received from an energy storage device such as a battery.
  • hybrid electric vehicles include on-board chargers that use power from vehicle braking and traditional motors to charge the vehicles. Vehicles that are solely electric generally receive the electricity for charging the batteries from other sources.
  • Battery electric vehicles (electric vehicles) are often proposed to be charged through some type of wired alternating current (AC) such as household or commercial AC supply sources.
  • the wired charging connections require cables or other similar connectors that are physically connected to a power supply. Cables and similar connectors may sometimes be inconvenient or cumbersome and have other drawbacks.
  • IPT inductive power transfer
  • a primary power device to a secondary (or "pick-up") power device.
  • each device includes one or more windings of electric current conveying media, such as wires.
  • the arrangement results in little leakage of flux below the coils on the side of the core.
  • the primary winding it is desirable for the primary winding to have a low inductance.
  • a winding with a high inductance is difficult to drive at high frequencies because large voltages are required across the coil terminals.
  • a physically thin winding is unobtrusive and is advantageous in wireless power transfer systems for electric vehicles where base or primary windings are positioned at ground level and the vehicle is charged by positioning a pick-up coil over the base winding.
  • base winding inductance may be tuned to an expected winding separation distance for optimal charging.
  • a thin base winding means greater tolerance to different installations of a base winding relative to the ground.
  • Typical base windings are designed with a specific inductance and to work at a specified frequency and current to ensure optimal charging of batteries connected to pick-up windings designed with complimentary characteristics. Attempting to charge pick-up windings that are sub-optimally compatible with the base winding can lead to slow charging times, energy waste or overheating components. However, different types or models of vehicles may have different pick-up windings or batteries. It is therefore desirable for base chargers in a wireless charging system to be able to charge vehicles of differing characteristics with minimal loss of efficiency.
  • winding arrangements are typically provided in magnetic association with a magnetic structure comprising a material of high magnetic permeability, such as ferrite, which may be referred to as a core, despite the winding or coils that comprise the winding not necessarily being wound around the magnetically permeable material.
  • a material of high magnetic permeability such as ferrite
  • the problem of suitable construction of high power base winding arrangements suitable for burying in a roadway environment is a significant issue especially where ferrite is used for the core material.
  • multifilar windings add additional problems in that proximity affects can mean that unequal current flows in the parallel wires. This unequal current distribution in the copper further exacerbates the potential for further losses.
  • Designing flux coupling structures for thermal energy management is highly desirable since overheating can lead to failure of the structure or related system, and presents safety issues. Preventing overheating is challenging because active heating solutions such as fans or liquid cooling systems are either not practically feasible, or are too expensive for most applications.
  • a magnetic structure for a magnetic flux coupling apparatus comprising:
  • a coil a magnetically permeable material, and a conductive heat transfer means.
  • the heat transfer means can allow heat in a first region of the structure to be transferred to a second region of the structure. In this manner, the heat can be distributed to prevent the first region overheating.
  • the heat transfer means can alternatively or additionally allow heat to be transferred from the structure, or a first region of the structure, to a second region external of the structure.
  • the heat transfer means comprises a heat conductor and may alternatively or additionally have a property of heat absorption. Therefore, the heat transfer means may absorb heat from a first region of the structure and distribute heat energy over time to the first region and/or to a second region.
  • the heat transfer means may be provided between two or more pieces or lengths of the magnetically permeable material. Thus the heat transfers means may conduct heat from the permeable material.
  • the heat transfer means comprises a heat pipe.
  • a further heat conducting structure such as a back plate may be provided.
  • the heat transfer means may transfer heat from the magnetically permeable material to the back plate.
  • a magnetic structure for a magnetic flux coupling apparatus comprising:
  • a coil and a magnetically permeable material, wherein at least a part of the coil is embedded or immersed in a heat conductive medium to conduct heat from that part of the coil.
  • the heat conductive medium may transfer heat to another region of the structure, or to a region external of the structure.
  • the coil and/or the lengths of magnetically permeable may be partially or fully embedded or immersed in the heat conductive medium.
  • the heat conductive medium may comprise a solid or semi-solid, such as a thermally conductive epoxy, paste or grease.
  • An additional heat transfer means such as a heat pipe, may also be provided.
  • a magnetic structure for a magnetic flux coupling apparatus comprising:
  • a coil a magnetically permeable material and an electrically conductive heat transfer means, wherein the heat transfer means conducts heat away from at least a part of the structure, and wherein the heat transfer means is located in the structure dependent on a magnetic property of the structure.
  • the magnetic property may comprise a flux path or pattern produced upon energisation of the coil.
  • the heat transfer means may be located so as to avoid the flux path. Alternatively, the heat transfer means may be located relative to the coil and/or the permeable material so as to provide or assist in providing a required flux path or flux pattern.
  • Figure 1 is a diagrammatic illustration of an IPT system for a vehicle application
  • Figure 2 is a circuit diagram of an IPT system such as that illustrated in Figure 1 ;
  • Figure 3 is a diagrammatic plan view of a bifilar winding arrangement comprising two coils, (the general form of single winding two coil arrangement being referred to in this document as a DD or DoubleD winding arrangement);
  • Figure 4 is a plan view of a practical quadfilar DD winding arrangement with balanced inductances
  • Figures 5 to 7 are partial side elevations in transverse cross section of a magnetic structure and winding arrangement.
  • Figures 8(a)-(c) are a plan view, and perspective sectional views, of another magnetic structure arrangement in which an electrically conductive material is used to transfer heat within the structure.
  • Figure 9 shows a graph showing temperature improvements achieved with certain
  • Figure 10 shows results of a thermally potted simulation.
  • Figure 1 1 shows a graph comparing the results of Figure 10 with an experimental result.
  • Wirelessly transferring power may refer to transferring any form of energy associated with electric fields, magnetic fields, electromagnetic fields, or otherwise from one magnetic flux coupling structure to another without the use of physical electrical conductors (e.g., power may be transferred through free space).
  • the power output into a wireless field e.g., a magnetic field
  • a receiving power transfer structure such as a winding to achieve power transfer.
  • the term windings is intended to refer to a component that may wirelessly output or receive energy for coupling to another winding.
  • the winding may typically be magnetically associated with a physical magnetically permeable material of the structure such as a ferrite core. Physical cores including ferromagnetic or ferromagnetic materials may allow development of a stronger electromagnetic field and improved coupling. It should be noted that a winding is not necessarily wound around a core.
  • a winding comprises one or more turns of conducting material.
  • the term coil may be used in both the sense of meaning any part of a winding arrangement of electrically conducting material and in the sense of a localised arrangement having a number of turns of conducting material that all go around a single central point.
  • a winding as described herein can take a number of different shapes and may comprise a single coil or a number of coils. The term coil is used for convenience with reference to figures 1 and 2, but the person skilled in the art will appreciate that use of the term with reference to those figures may be substituted with references to a winding.
  • An electric vehicle is used herein to describe a remote system, an example of which is a vehicle that includes, as part of its locomotion capabilities, electrical power derived from a chargeable energy storage device (e.g., one or more rechargeable electrochemical cells or other type of battery).
  • a chargeable energy storage device e.g., one or more rechargeable electrochemical cells or other type of battery.
  • some electric vehicles may be hybrid electric vehicles that include besides electric motors, a traditional combustion engine for direct locomotion or to charge the vehicle's battery. Other electric vehicles may draw all locomotion ability from electrical power.
  • An electric vehicle is not limited to an automobile and may include
  • a remote system is described herein in the form of an electric vehicle (EV).
  • EV electric vehicle
  • other remote systems that may be at least partially powered using a chargeable energy storage device are also contemplated (e.g., electronic devices such as personal computing devices and the like).
  • FIG. 1 is a diagram of an exemplary wireless power transfer system 100 for charging an electric vehicle 1 12, in accordance with an exemplary embodiment of the invention.
  • the wireless power transfer system 100 enables charging of an electric vehicle 1 12 while the electric vehicle 1 12 is parked near a base wireless charging system 102a. Spaces for two electric vehicles are illustrated in a parking area to be parked over corresponding base wireless charging system 102a and 102b.
  • a local distribution center 130 may be connected to a power backbone 132 and configured to provide an alternating current (AC) or a direct current (DC) supply through a power link 1 10 to the base wireless charging system 102a.
  • the base wireless charging system 102a also includes a base system coil 104a for wirelessly transferring or receiving power.
  • An electric vehicle 1 12 may include a battery unit 1 18, an electric vehicle coil 1 16, and an electric vehicle wireless charging system 1 14.
  • the electric vehicle coil 1 16 may interact with the base system coil 104a for example, via a region of the electromagnetic field generated by the base system coil 104a.
  • the electric vehicle coil 1 16 may receive power when the electric vehicle coil 1 16 is located in an energy field produced by the base system coil 104a.
  • the field corresponds to a region where energy output by the base system coil 104a may be captured by an electric vehicle coil 1 16.
  • the field may correspond to the "near field" of the base system coil 104a.
  • the near-field may correspond to a region in which there are strong reactive fields resulting from the currents and charges in the base system coil 104a that do not radiate power away from the base system coil 104a.
  • the near-field may correspond to a region that is within about 1/2 ⁇ of the wavelength of the base system coil 104a (and vice versa for the electric vehicle coil 1 16) as will be further described below.
  • Local distribution 130 may be configured to communicate with external sources (e.g., a power grid) via a communication backhaul 134, and with the base wireless charging system 102a via a communication link 108.
  • external sources e.g., a power grid
  • the base wireless charging system 102a may be located in a variety of locations. As non- limiting examples, some suitable locations include a parking area at a home of the electric vehicle 1 12 owner, parking areas reserved for electric vehicle wireless charging modeled after petroleum-based filling stations, and parking lots at other locations such as shopping centers and places of employment.
  • Charging electric vehicles wirelessly may provide numerous benefits. For example, charging may be performed automatically, virtually without driver intervention and manipulations thereby improving convenience to a user. There may also be no exposed electrical contacts and no mechanical wear out, thereby improving reliability of the wireless power transfer system 100. Manipulations with cables and connectors can be avoided, and there may be no cables, plugs, or sockets that may be exposed to moisture and water in an outdoor environment, thereby improving safety.
  • V2G Vehicle-to-Grid
  • a wireless power transfer system 100 as described with reference to FIG. 1 may also provide aesthetical and non-impedimental advantages. For example, there may be no charge columns and cables that may be impedimental for vehicles and/or pedestrians.
  • the wireless power transmit and receive capabilities may be configured to be reciprocal such that the base wireless charging system 102a transfers power to the electric vehicle 1 12 and the electric vehicle 1 12 transfers power to the base wireless charging system 102a e.g., in times of energy shortfall. This capability may be useful to stabilize the power distribution grid by allowing electric vehicles to contribute power to the overall distribution system in times of energy shortfall caused by over demand or shortfall in renewable energy production (e.g., wind or solar).
  • renewable energy production e.g., wind or solar
  • FIG. 2 is a schematic diagram of exemplary key components of the wireless power transfer system 100 of FIG. 1 .
  • the wireless power transfer system 200 may include a base system transmit circuit 206 including a base system coil 204 having an inductance L1 .
  • the wireless power transfer system 200 further includes an electric vehicle receive circuit 222 including an electric vehicle coil 216 having an inductance L2.
  • Embodiments described herein may use capacitively loaded wire loops (i.e., multi-turn coils) forming a resonant structure that is capable of efficiently coupling energy from a primary structure (transmitter) to a secondary structure (receiver) via a magnetic or electromagnetic near field if both primary and secondary are tuned to a common resonant frequency.
  • capacitively loaded wire loops i.e., multi-turn coils
  • a resonant frequency may be based on the inductance and capacitance of a transmit circuit including a coil (e.g., the base system coil 204) as described above.
  • inductance may generally be the inductance of the coil
  • capacitance may be added to the coil to create a resonant structure at a desired resonant frequency.
  • a capacitor may be added in series with the coil to create a resonant circuit (e.g., the base system transmit circuit 206) that generates an electromagnetic field, which may be referred to as a series-tuned resonant circuit.
  • the value of capacitance for inducing resonance may decrease as the diameter or inductance of the coil increases. Inductance may also depend on a number of turns of a coil. Furthermore, as the diameter of the coil increases, the efficient energy transfer area of the near field may increase. Other resonant circuits are possible. As another non limiting example, a capacitor may be placed in parallel between the two terminals of the coil (e.g., a parallel resonant circuit, alternatively referred to as a parallel-tuned resonant circuit). Furthermore an coil may be designed to have a high quality (Q) factor to improve the resonance of the coil.
  • Q quality
  • the coils may be used for the electric vehicle coil 216 and the base system coil 204.
  • Using resonant structures for coupling energy may be referred to as “magnetic coupled resonance,” “electromagnetic coupled resonance,” and/or “resonant induction.”
  • the operation of the wireless power transfer system 200 will be described based on power transfer from a base wireless power charging system 202 to an electric vehicle 1 12, but is not limited thereto.
  • the electric vehicle 1 12 may transfer power to the base wireless charging system 102a.
  • a power supply 208 (e.g., AC or DC) supplies power PSDC to the base wireless power charging system 202 to transfer energy to an electric vehicle 1 12.
  • the base wireless power charging system 202 includes a base charging system power converter 236.
  • the base charging system power converter 236 may include circuitry such as an AC/DC converter configured to convert power from standard mains AC to DC power at a suitable voltage level, and a DC/low frequency (LF) converter configured to convert DC power to power at an operating frequency suitable for wireless high power transfer.
  • LF low frequency
  • the base charging system power converter 236 supplies power P1 to the base system transmit circuit 206 including a base charging system tuning circuit 205 which may consist of reactive tuning components in a series or parallel configuration or a combination of both with the base system coil 204 to emit an electromagnetic field at a desired frequency.
  • a capacitor may be provided to form a resonant circuit with the base system coil 204 that resonates at a desired frequency.
  • the base system transmit circuit 206 including the base system coil 204 and electric vehicle receive circuit 222 including the electric vehicle coil 216 may be tuned to substantially the same frequencies and may be positioned within the near-field of an electromagnetic field transmitted by one of the base system coil 204 and the electric vehicle coil 216.
  • the base system coil 204 and electric vehicle coil 216 may become coupled to one another such that power may be transferred to the electric vehicle receive circuit 222 including an electric vehicle charging system tuning circuit 221 and electric vehicle coil 216.
  • the electric vehicle charging system tuning circuit 221 may be provided to form a resonant circuit with the electric vehicle coil 216 that resonates at a desired frequency.
  • the mutual coupling coefficient resulting at coil separation is represented in the diagram by k(d).
  • Equivalent resistances Req1 and Req2 represent the losses that may be inherent to the coils 204 and 216 and any anti-reactance capacitors that may, in some embodiments, be provided in the base charging system tuning circuit 205 and electric vehicle charging system tuning circuit 221 respectively.
  • the electric vehicle receive circuit 222 including the electric vehicle coil 216 and electric vehicle charging system tuning circuit 221 receives power P2 and provides the power P2 to an electric vehicle power converter 238 of an electric vehicle charging system 214.
  • the electric vehicle power converter 238 may include, among other things, a LF/DC converter configured to convert power at an operating frequency back to DC power at a voltage level matched to the voltage level of an electric vehicle battery unit 218.
  • the electric vehicle power converter 238 may provide the converted power PLDC to charge the electric vehicle battery unit 218.
  • the power supply 208, base charging system power converter 236, and base system coil 204 may be stationary and located at a variety of locations as discussed above.
  • the battery unit 218, electric vehicle power converter 238, and electric vehicle coil 216 may be included in an electric vehicle charging system 214 that is part of electric vehicle 1 12 or part of the battery pack (not shown).
  • the electric vehicle charging system 214 may also be configured to provide power wirelessly through the electric vehicle coil 216 to the base wireless power charging system 202 to feed power back to the grid.
  • Each of the electric vehicle coil 216 and the base system coil 204 may act as transmit or receive coils based on the mode of operation.
  • the electric vehicle charging system 214 may include switching circuitry (not shown) for selectively connecting and disconnecting the electric vehicle coil 216 to the electric vehicle power converter 238. Disconnecting the electric vehicle coil 216 may suspend charging and also may adjust the "load" as "seen” by the base wireless charging system 102a (acting as a transmitter), which may be used to decouple the electric vehicle charging system 214 (acting as the receiver) from the base wireless charging system 202. The load changes may be detected if the transmitter includes the load sensing circuit. Accordingly, the transmitter, such as a base wireless charging system 202, may have a mechanism for determining when receivers, such as an electric vehicle charging system 1 14, are present in the near-field of the base system coil 204.
  • the base system coil 204 and electric vehicle coil 1 16 are configured according to a mutual resonant relationship such that when the resonant frequency of the electric vehicle coil 216 and the resonant frequency of the base system coil 204 are very close or substantially the same. Transmission losses between the base wireless power charging system 202 and electric vehicle charging system 214 can be reduced when the electric vehicle coil 216 is located in the near-field of the base system coil 204.
  • an efficient energy transfer occurs by coupling a large portion of the energy in the near field of a transmitting coil to a receiving coil rather than propagating most of the energy in an electromagnetic wave to the far-field.
  • a coupling mode may be established between the transmit coil and the receive coil.
  • the area around the coils where this near field coupling may occur is referred to herein as a near field coupling mode region.
  • an electric vehicle 1 12 may be aligned along an X direction and a Y direction to enable an electric vehicle coil 1 16 within the electric vehicle 1 12 to be adequately aligned with a base wireless charging system 102a within an associated parking area.
  • the electric vehicle charging system 1 14 may be placed on the underside of the electric vehicle 1 12 for transmitting and receiving power from a base wireless charging system 102a.
  • an electric vehicle coil 1 16 may be integrated into the vehicle's underbody near a centre position providing maximum safety distance in regards to EM exposure and permitting forward and reverse parking of the electric vehicle.
  • a coil comprises lengths of conducting material wound in a plurality of individual coils.
  • FIG. 3 is a diagram of one example of a winding arrangement 600 of two lengths of conducting material being filars 601 and 604 are used in a coil according to one embodiment of the invention.
  • Conducting material 601 and 604 may be any suitable material formed of electrically conducting media and may include wires and the like.
  • conducting material 601 and 604 comprises litz wire because of its advantageous properties of reducing the skin effect and the proximity effect when carrying alternating currents.
  • a "length of conducting material" i.e. a wire or filar may be formed from one or more smaller lengths connected together in a way whereby the longer length acts like a single length of conducting material. For example, lengths of wire may be wound, tied, plugged, fused, soldered or the like together to form a longer length of wire.
  • the coil arrangement shown in Figure 3 is but one example of a possible winding arrangement that may be used. It will be appreciated by those skilled in the art that many other winding arrangements, for example single coils rather than multiple coils, may be used, and that the invention is not solely applicable to mutlifilar windings.
  • lengths of conducting material 601 and 604 are wound into an arrangement comprising two substantially co-planar coils 602 and 603 positioned generally adjacent one another.
  • the lengths of conducting material 601 and 604 are wound in a spiral arrangement, that is, an arrangement such that each coil 602 and 607 is formed from a spiral of loops of increasing radius where the length of conducting material does not cross over itself within each coil.
  • the ends of conducting material 601 and 604 form terminals 605 and 606 that, in use, are electrically connected to a power source or battery in a wireless power transfer system.
  • Coils 602 and 603 are wound in opposition such that one is wound clockwise and the other is wound counter-clockwise. In this way, coils 602 and 602 are wound such that electric current passing through the lengths of conducting material flows in the same direction in adjacent portions of the two coils.
  • the two coils 602 and 603 may be positioned in magnetic association with one or more magnetically permeable members.
  • the coils may be positioned on top of a core formed of a number of parallel ferrite bars.
  • the coils 602 and 603 act as pole areas and lines of magnetic flux arc between them in the form of a "flux pipe" above the coils, a zone of high flux concentration.
  • a pick-up coil can be positioned within the flux pipe to achieve wireless, or more specifically inductive, power transfer.
  • the two coils 602 and 603 are formed from the same length of conducting material wound continuously around the coils.
  • a multifilar winding is a winding that is wound using two or more filars, that is to say wires, provided in parallel.
  • the parallel wires are joined at each of the two end terminals of the winding.
  • Each wire can carry a rated current and hence multiple filars in parallel can be used to conduct a greater overall magnitude of current.
  • a problem with the multiple parallel wires forming a multifilar winding is ensuring that the current distribution among all the parallel paths be substantially equal. This means that not only the self- inductance of each parallel path created by the constituent wires should be the same, or substantially the same, but the mutual inductance between the various parallel paths must also be substantially balanced.
  • FIG. 4 An example of a practical implementation of a winding arrangement similar to that of Figure 3 is shown in Figure 4.
  • the winding arrangement is provided as part of a pad structure 401 which includes a layer of magnetically permeable material that in this example comprises strips of permeable material 402 (for example ferrite material) which are separated by gaps or spaces 403.
  • Filars 404 are laid over the layer of permeable material.
  • the winding arrangement of pad 401 happens to be a quadfilar arrangement, having four filars in each turn, but as mentioned above, other arrangements may be used.
  • filars cross over each other at crossing points 405 which are selectively located at a gap 403 in the permeable layer. Crossing the filars enables the inductance of each filar to be equal, or at least sufficiently balanced.
  • a problem with wireless power transfer magnetic structures is overheating.
  • an approach to manage or assist with the management of overheating is to conduct heat away from regions of the magnetic structure that are at risk of overheating.
  • the heat can be absorbed and/or transferred to other parts of the structure, or transferred externally of the structure.
  • specific examples are discussed in the context of a magnetic coupling structure with two coils and with at least two pieces of magnetically permeable material (ferrite).
  • the heat transfer methods and devices that are described may be used with magnetic coupling devices that have other coil and permeable material arrangements.
  • the heat transfer mechanisms described are applicable to single coil structures.
  • the heat transfer or conduction mechanisms described below may be used with the arrangements of permeable material (such as the introduction of controlled gaps in the permeable material structure) and/or with the multifliar winding arrangement as described above.
  • a heat conductive medium may be used to affect the heat transfer.
  • the heat conductive medium may transfer heat to another region of the structure, and/or to a region external of the structure.
  • the coil and/or the lengths of magnetically permeable may be partially or fully embedded or immersed i.e. potted in the heat conductive medium.
  • the heat conductive medium may comprise a solid or semi-solid, such as a thermally conductive epoxy, paste or grease.
  • the coil or the permeable material, or a region of one or both of these is embedded or immersed in a heat conductive medium to conduct heat from that part of the structure to another part of the structure.
  • a heat conductive medium such as a heat conductive epoxy, paste or grease, for example a 5 W/mK grease, or a 6 W/mK paste.
  • the heat conductive medium distributes the thermal energy throughout the structure, preventing problematic hotspots.
  • a heat transfer means may be provided to assist with heat transfer.
  • This may comprise a body of material with good thermal conduction and/or absorption properties and which may be placed in thermal contact with regions of the structure from which heat should be removed.
  • the physical form of the heat transfer means may be formed to comply with adjacent physical contours of the structure so that adequate thermal conduction is achieved.
  • a heat transfer means is simply a piece of highly thermally conductive material.
  • Another example is a heat pipe.
  • the permeable material used in the magnetic structures is arranged in lengths or strips.
  • the permeable material may have one or more gaps or recesses.
  • Heat transfer apparatus may be located in gaps or recesses or between strips in order to redistribute heat and thus even the overall thermal profile or properties of the structure.
  • a heat pipe may be used in between ferrite strips to assist in heat transfer.
  • Figure 5 shows part of a magnetic structure such as that of Figure 4, in cross section along what may be considered to be a vertical line in Figure 4.
  • ferrite strips 1801 and 1802 Corresponding to strips 402 in Figure 4) have a heat pipe 1803 located between them to transfer heat between the strips.
  • the heat pipe 1803 is located in a gap between strips (e.g. gap 403 of Figure 4).
  • a backing plate 1804 (which could be a metallic material) may also be provided in a layer beneath the permeable material, and the heat pipe may also or alternatively function to transfer heat to the backing plate.
  • Electrically insulating sheet material 1805 may be used between the filars and the ferrite, and between the backplate and the ferrite. Filar 1508 on top of the permeable material and the heat pipe 1803 corresponds to one of the filars 404 in Figure 4.
  • the heat pipe 1803 it is possible for the heat pipe 1803 to be formed in such a way that it can form a space or recess to accommodate wires or filars 1901 and 1902 which may be run along the heat pipe to exit the arrangement at a termination such as a connection to a power supply.
  • the heat pipe 1803 may also be formed to allow a space to accommodate filar crossover points (corresponding to crossover areas 405 in Figure 4) without adding to the overall height or thickness of the winding arrangement.
  • the heat pipe is formed from non-
  • the heat pipe described above may be constructed from an electrically conductive material.
  • the magnetic flux paths concentrate in the permeable material so there is little flux in the region between the two pieces 1801 and 1802. Therefore, the eddy currents are low, meaning there is little if any additional heat generated by the presence of an electrically conductive material, and hence there is a net improvement in thermal management of the structure.
  • the heat pipe 1803 is replaced with a block of electrically and thermally conductive material, such as block 2001 as shown in Figure 8(a) and 8(c).
  • FIG 8(a) a plan view is shown of a structure which includes aluminium block 2001 between permeable material 1801 and 1802.
  • Figures 8(b) and (c) are a cross section through the centre of Figure 8(a).
  • the aluminium block is removed to shown the gap or cavity in which the block can be located.
  • Heat conducting pads or pastes or greases may be placed in the cavity to allow good thermal conduction to occur between parts of the structure and the block.
  • the block may also be in thermal contact with the coils 1901 and/or 1902 as shown in Figure 8(c).
  • the coils 1901 and 1902 are wound about a former 2002 which may be constructed from a suitable non-conductive material, for example a plastics material.
  • the former sits on top of a base such as an aluminium base 2003.
  • a further layer of material, for example a heat conductive but non-electrically conducted material 2004 may be provided if necessary between the conductive base plate 2003 and the coils so as to help insulate the coils from the base plate.
  • the layer 2004 is removed in the area where the aluminium bar 2001 is to be located. Therefore, as shown in Figure 8(c), the aluminium bar 2001 is in direct thermal contact with the base plate 2003, which in this example is also made from aluminium, so that a highly thermally conductive connection between the bar 2001 and the base plate 2003 is established.
  • thermally and electrically conductive material such as block 2001 can be located in the structure to alter a magnetic flux path produced or received by the structure.
  • location of aluminium for example at one side of a structure may be beneficially used to control heat at that location and also reflect or repel magnetic flux in that region so that a desired flux pattern is produced.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Electric Propulsion And Braking For Vehicles (AREA)

Abstract

Une structure de couplage à flux magnétique comprend une bobine, un matériau magnétiquement perméable et un moyen de transfert de chaleur électroconducteur qui conduit la chaleur à l'opposé d'au moins une partie de la structure.
PCT/NZ2018/050048 2017-04-10 2018-04-10 Régulation thermique dans des structures de couplage par transfert de puissance inductive WO2018190729A1 (fr)

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WO2023047380A1 (fr) * 2021-09-24 2023-03-30 Auckland Uniservices Limited Magnétiques à haute puissance dans des systèmes de charge sans fil
WO2023248164A1 (fr) * 2022-06-21 2023-12-28 Auckland Uniservices Limited Coupleur de transfert de puissance sans fil

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