WO2014166942A2

WO2014166942A2 - Inductive power transfer pad and system for inductive power transfer

Info

Publication number: WO2014166942A2
Application number: PCT/EP2014/057044
Authority: WO
Inventors: Dominik Anders; Robert Czainski
Original assignee: Bombardier Transportation Gmbh
Priority date: 2013-04-09
Filing date: 2014-04-08
Publication date: 2014-10-16
Also published as: WO2014166942A3

Abstract

Inductive power transfer pad and system for inductive power transfer The invention relates to an inductive power transfer pad, in particular an inductive power transfer pad (1) of a system for inductive power transfer to a vehicle, comprising: - a housing (2), - a primary winding structure (15), - a connecting terminal (4, 6), wherein the inductive power transfer pad (1) further comprises an inverter (5), wherein the inverter (5) is arranged within the housing (2), wherein an input side of the inverter (5) is electrically coupled to the connecting terminal (4, 6) and an output side of the inverter (5) is electrically coupled to the primary winding structure (15). Furthermore, the invention relates to a method of operating an inductive power transfer pad and a method of manufacturing an inductive power transfer pad.

Description

Inductive power transfer pad and system for inductive power transfer

The invention relates to an inductive power transfer pad and a system for inductive power transfer to a vehicle. Furthermore, the invention relates to a method of manufacturing and a method of operating said inductive power transfer pad.

Electric vehicles, in particular a track-bound vehicle, and/or a road automobile, can be operated by electric energy which is transferred by means of an inductive power transfer. Such a vehicle may comprise a circuit arrangement, which can be a traction system or a part of a traction system of the vehicle, comprising a receiving device adapted to receive an alternating electromagnetic field and to produce an alternating electric current by electromagnetic induction. Furthermore, such a vehicle can comprise a rectifier adapted to convert an alternating current (AC) to a direct current (DC). The DC can be used to charge a traction battery or to operate an electric machine. In the latter case, the DC can be converted into an AC by means of an inverter.

The inductive power transfer is performed using two sets of e.g. three-phase windings. A first set is installed on the ground (primary windings) and can be fed by a wayside power converter (WPC). The second set of windings is installed on the vehicle. For example, the second set of windings can be attached underneath the vehicle, in the case of trams under some of its wagons. For an automobile it can be attached to the vehicle chassis. The second set of windings or, generally, the secondary side is often referred to as pickup-arrangement or receiver. The first set of windings and the second set of windings form a high frequency transformer to transfer electric energy to the vehicle. This can be done in a static state (when there is no movement of the vehicle) and in a dynamic state (when the vehicle moves).

In particular in the case of road automobiles, a stationary primary unit comprises a plurality of elements which are often arranged spatially separated. WO 2008/140333 A2 discloses an inductive power transfer pad comprising a coil having at least one turn of a conductor, one or more ferromagnetic slabs and a shield member arranged around both said coil and said ferromagnetic slabs for channeling

electromagnetic flux when in use.

WO 201 1/145953 A1 discloses a multiphase IPT primary track conductor arrangement comprising a first phase conductor and a second phase conductor, wherein the conductors are being arranged substantially in a plane and so as to overlap each other and being arranged such that there is substantially balanced mutual coupling between the phase conductors.

EP 2081792 B1 discloses a cladding element having a receiving unit integrated therein. The receiving unit comprises a receiver coil for contactless transmission of electrical energy and a plurality of flow conducting elements that are allocated to the receiver coil and designed to concentrate the field strength and are made from a material having high permeability compared with air.

It is an object of the invention to provide an inductive power transfer pad and a system for inductive power transfer comprising said inductive power transfer pad, wherein a manufacturing and installation effort is reduced and an usability is improved.

It a basic idea of the invention to spatially integrate all elements needed for the generation of a power transfer field from an arbitrary alternating current voltage and/or an arbitrary direct current voltage into a single inductive power transfer pad.

The present invention can be applied in particular to the field of energy transfer to any land vehicle, for example track bound vehicles, such as rail vehicles (e.g. trams). In particular, the invention relates to the field of energy transfer to road automobiles, such as individual (private) passenger cars or public transport vehicles (e.g. busses).

An inductive power transfer pad, in particular a transfer pad of a system of inductive power transfer to a vehicle, is proposed. The inductive power transfer pad (IPT pad) is part of a primary unit of a system for inductive power transfer. The IPT pad comprises a housing. The housing can have a cuboid shape. As such, the housing can have a bottom side, e.g. provided by a base plate, four sidewalls, and a top side, e.g. provided by a top plate. It is, however, alternatively possible that the housing is partly opened, e.g. on the top side. The housing encloses an inner volume of the housing. Alternative to the cuboid shape of the housing, other shapes known to the person skilled in the art can be chosen.

Furthermore, the IPT pad comprises a primary winding structure. The primary winding structure generates an alternating (electro-)magnetic field which can be also referred to as power transfer field if the primary winding structure is energized or supplied with an operating current.

The primary winding structure can comprise one or more, preferably three, phase lines. This/These phase line(s) can be fed with an alternating current to generate the

aforementioned power transfer field.

Furthermore, the IPT pad comprises a connecting terminal. The connecting terminal provides connecting means for connecting an external power supply to the IPT pad. The connecting terminal can e.g. be designed as a socket, in particular a male socket or a female socket. Via the said connecting terminal, an external power supply, e.g. an external electrical network or an external energy storage, e.g. a battery, can be connected to the IPT pad, e.g. by means of a cable.

According to the invention, the IPT pad further comprises an inverter. The inverter can be used to generate an alternating current (AC) output voltage from a direct current (DC) input voltage. The inverter can comprise active electric or electronic elements, e.g. IGBTs or MOSFETs. By controlling an operation of said elements, an AC output current with desired characteristics, e.g. a desired amplitude and/or frequency and/or phase, can be generated. The inverter can be provided by a converter.

An input side of the inverter is electrically coupled to the connecting terminal and an output side of the inverter is electrically coupled to the primary winding structure. Thus, an electric connection of the primary winding structure to an external power supply is provided at least partially by the inverter which is, in contrast to the aforementioned state of the art, integrated into the IPT pad, in particular into the housing of the IPT pad. This advantageously allows connecting an arbitrary DC input voltage to the connecting terminal of the IPT pad, wherein the desired AC output voltage to energize the primary winding structure is generated by the pad-sided inverter.

This, in turn, increases a usability of the proposed IPT pad since the IPT pad can be operated independent from an input voltage. The IPT pad can be supplied by an arbitrary DC input voltage and operation is not restricted to an AC input voltage with desired characteristics, e.g. a desired amplitude and/or frequency.

For example, the proposed IPT pad can be installed in a garage of a private house or in a parking slot for an automobile, wherein the IPT pad can be connected to a household electric network (which will be explained later) or a battery providing a DC battery voltage with an arbitrary output voltage level. In particular, the IPT pad can be installed on the ground such that a vehicle can be positioned above the IPT pad.

It is also possible that the IPT pad is connected to a DC current generator, wherein a desired DC voltage can be generated by the DC generator. The DC generator can e.g. be installed at a wall, i.e. within a so called wall box. In this case, the DC generator can also be connected to a household electric network. The wall box can also provide a human- machine-interface for controlling an operation of the IPT pad. In this case, there are also means for data communication between the wall box and the IPT pad, e.g. means for wireless data communication.

Furthermore, the IPT pad can comprise one or more fixation means for fixing or attaching the IPT pad to the ground, e.g. a route surface or a surface of a parking lot or a garage.

The inverter is arranged within the housing. In particular, the inverter can be arranged within the aforementioned inner volume of the housing. In this case, the connecting terminal can provide an electric connecting means of the inner volume of the housing to an external volume with respect to the housing.

The housing can have predetermined dimensions, in particular a predetermined length, a predetermined width and a predetermined height. By integrating the inverter into the housing, a compact and highly integrated IPT pad can be realized. Thus, an installation space required for the installation of primary-sided components can be reduced. This further enhances the usability of the proposed IPT pad.

The IPT pad can be designed such that a power in the range of 3 kW to 20 kW can be transferred to e.g. a vehicle comprising a corresponding receiving device which can be also referred to as pick-up. In a first alternative, an amplitude of an input voltage of the IPT pad can be 230V and an input current can be 16A. This allows transferring 3 kW to 7 kW to a receiving device on a secondary side. In a second alternative, an amplitude of an input voltage of the IPT pad can be 460V and an input current can be 32A. This allows transferring around 20 kW to a receiving device on a secondary side.

In another embodiment, the inductive power transfer pad comprises a rectifier, wherein the inverter is coupled to the connecting terminal via the rectifier. By means of the rectifier, an AC voltage can be transformed into a DC voltage, wherein the DC voltage can provide the input voltage of the inverter. By arranging the rectifier in a current path connecting the connecting terminal and the inverter, the IPT pad can be connected to an external power supply, in particular a household power supply, which provides an AC voltage. Such an AC voltage provided by the external network can, for example, have a frequency of 50Hz or 60Hz. A nominal value of such an AC voltage can be 120V or 230V. It is, of course, possible that the AC voltage features different characteristics.

In this case, the connecting terminal can provide an AC connecting terminal for connecting the inductive power transfer pad to an external AC voltage supply means, wherein the inverter is coupled to the AC connecting terminal via a rectifier. The external AC voltage supply means can e.g. be an AC voltage source or an electric element or circuit providing an AC voltage, e.g. an external AC network such as a household network. Thus, the power transfer pad can be operated by an external AC voltage. This further increases the usability of the power transfer pad.

By providing the rectifier, the usability of the IPT pad can be increased. It is, for instance, possible, to install the IPT pad in a garage of a private house and connect the IPT pad to the standard household electrical network which provides an AC input voltage.

As the inverter, the rectifier can be arranged within the housing of the IPT pad, in particular within the inner volume of the housing. In another embodiment, the inductive power transfer pad comprises another connecting terminal, wherein the inverter is coupled directly to the other connecting terminal, e.g. by a current path. In this case, the other connecting terminal can be used to connect the IPT pad to another external power supply which provides a DC voltage with an arbitrary voltage level, e.g. to the aforementioned wall box. As the other connecting terminal is directly connected to the inverter, the DC voltage provided by the external power supply is equal to the input voltage of the inverter.

In this case, the other connecting terminal can provide a DC connecting terminal for connecting the stationary part to an external DC voltage supply means, wherein an input side of the inverter is electrically coupled to the DC connecting terminal and an output side of the converter is electrically coupled to the primary winding structure. The external DC voltage supply means can e.g. be a DC voltage source or an electric element or circuit providing a DC voltage, e.g. an external rectifier. The external DC voltage supply means can e.g. be integrated into a so-called wall box, wherein the wall box can fed by a household electric network and provide a DC voltage.

In this case, the IPT pad can be operated both by an external AC voltage and by an external DC voltage. This further increases the usability of the IPT pad.

In another embodiment, the inverter is coupled directly to the connecting terminal. In this case, the said connecting terminal can provide a DC connecting terminal for connecting the stationary part to an external DC voltage supply means. In this case, the IPT pad can only be supplied by an external power supply which provides a DC voltage.

Thus, three possible configurations are described. In a first configuration, the inductive power transfer pad comprises only the AC connecting terminal. In a second configuration, the power transfer pad comprises both terminals, a DC connecting terminal and an AC connecting terminal. In a third configuration, the power transfer pad comprises only the DC connecting terminal.

A DC connecting terminal of the inductive power transfer pad allows connecting an arbitrary DC input voltage to the DC connecting terminal of the power transfer pad, wherein the desired AC output voltage to energize the primary winding structure is generated by the pad-sided inverter. This, in turn, increases a usability of the proposed power transfer pad since the power transfer pad can be operated independent from characteristics of an input voltage. For example, the power transfer pad can be installed in a garage of a private house or in a parking slot of an automobile, wherein the power transfer pad can be connected to a DC voltage supply means, a household electric network or a battery providing DC battery voltage with an arbitrary output voltage level. In particular, the power transfer pad can be installed on the ground such that a vehicle can be positioned above the power transfer pad. The power transfer pad can be supplied by an arbitrary DC input voltage and/or operation is not restricted to an AC input voltage with desired characteristics, e.g. a desired amplitude and/or frequency.

In another embodiment, the inductive power transfer pad is connected to a DC current generator, wherein a desired DC voltage is generatable by the DC current generator. In particular, the inductive power transfer pad can be connected to the DC current generator via a DC connecting terminal. The DC current generator can denote or be provided by the aforementioned external DC voltage supply means. The DC generator can e.g. be integrated into a so-called wall box, wherein the wall box can fed by a household electric network and provide a DC voltage. The DC voltage supply means, e.g. the DC current generator, can be provided by a unit separate of the inductive power transfer pad, in particular a unit arranged outside the housing of the inductive power transfer pad.

The DC current generator or the DC voltage supply means can comprise at least one filter element for filtering a DC output voltage and/or a DC output current of the DC current generator. The at least one filter element can e.g. be also integrated into the wall box. It is, however, also possible that the inductive power transfer pad comprises at least one filter element, wherein the at least one filter element can e.g. be arranged within the housing. In this case, an input voltage and/or current of the inverter and/or an output voltage and/or current can be filtered by at least one filter element.

Thus, an arrangement of an inductive power transfer pad and an DC voltage supply means, e.g. a DC current generator, is described, wherein the inductive power transfer pad is connected to the DC voltage supply means, e.g. via a DC connecting terminal.

In another embodiment, the inductive power transfer pad comprises a control unit for controlling an operation of the inverter. As the inverter, the control unit can be arranged within the housing, in particular within an inner volume of the housing. A control unit can e.g. control an operation of electric or electronic elements of the inverter such that the inverter provides a desired AC output voltage which is used to energize the primary winding structure in order to generate a desired power transfer field.

It is, of course, possible, that the control unit is used to control an operation of other elements of the IPT pad, in particular of elements integrated into the housing of the IPT pad. The control unit can also be referred to as wayside control unit. The control unit can e.g. be responsible for all logical processes within the IPT pad. Furthermore, the control unit can manage a communication of the IPT pad with external control units. It is, for instance possible that the control unit and/or the IPT pad has/have an interface for data communication with other electronic devices.

In another embodiment, the inductive power transfer pad comprises a vehicle detection system.

The vehicle detection system, in particular one, multiple or all elements of the vehicle detection system can be arranged within the housing, in particular within an inner volume of the housing. Elements of the vehicle detection system can e.g. be sensors and corresponding control units for an evaluation of output signals of the sensors.

The vehicle detection system is a system by which the presence of a vehicle in the surrounding of the IPT pad can be detected. It can, for instance, be possible to detect if a vehicle is located above a charging surface of the IPT pad. The charging surface can denote a surface of the IPT pad arranged above the aforementioned primary winding structure. The charging surface can e.g. be an area enclose by a projection of an envelope of the primary winding structure to a surface of a top side of the housing of the IPT pad. Alternatively, the charging surface can be a subpart of the surface of the IPT pad through which the primary field or a predetermined portion, e.g. a portion larger than 80%, 90% or 95%, of the primary field extends during inductive power transfer, in particular during static charging.

The vehicle detection system can e.g. comprise an inductive or capacitive sensor element for detecting a vehicle. Preferably, the vehicle detection system is provided by a winding structure, e.g. a coil. The winding structure can be arranged adjacent to the primary winding structure, e.g. if the primary winding structure and the winding structure of the vehicle detection system are projected into a common plane of protection. It is, however, possible that the primary winding structure and the winding structure of the vehicle detection system partially overlap in the common plane of projection or that the winding structure of the vehicle detection system encloses the primary winding structure.

Alternatively, the vehicle detection system can comprise an optical sensor element such as a camera.

It is also possible that the vehicle comprises at least one enable signal transmitter which repeatedly or continuously emits an enable signal. The enable signal is received by the vehicle detection system, e.g. by a signal receptor. The enable signal received enables the operation of the IPT pad, i.e. the inductive power transfer. If the enable signal is not received or is not received any more within an expected period of time, the IPT pad is not operated, i.e. the primary winding structure is not energized, or an operation is interrupted.

The transmission of the enable signal may be realized by inductive coupling or by other procedures. Inductive coupling means that the signal is transferred by electromagnetic waves which induce a voltage in a receiving antenna of the IPT pad. Preferably, the signal receptor is realized as a receiving loop having at least one winding of a conductor.

Therefore, it is preferred that the signal receptor which is assigned to the IPT pad comprises a loop of an electric conductor, wherein the receiving area is defined by the area surrounded by the loop. If the IPT pad is arranged horizontally, e.g. mounted on a surface of the IPT pad, the area is therefore also a horizontal area. Preferably, the length of the area is equal or nearly equal to the length of the IPT pad. The width of the area may be in the range of some centimeters and is preferably smaller than 50 cm. A small width has the advantage that the receiving area is less sensitive to stray components of the enable signal, especially stray components of enable signals transmitted from vehicles on parallel tracks do not enable the operation of the IPT pad.

Moreover, it is possible that the vehicle detection system is a system by which the position of the vehicle with respect to the IPT pad, in particular to the charging surface of the IPT pad, can be determined. This advantageously increases a functional capability of the IPT pad. Using a IPT pad with a vehicle detection system advantageously allows detecting if a vehicle is located within a desired charging volume assigned to the IPT pad, e.g. directly above an upper or top surface of the IPT pad and, if applicable, to detect if the vehicle is in a correct position such that a predetermined amount of the total power transfer field can be received by a vehicle-sided secondary winding structure.

The aforementioned control unit can be used to evaluate output signals of the sensors. If no vehicle or an incorrect positioned vehicle, e.g. a vehicle which is not positioned within a predetermined position range, is detected, the inverter will not be operated and/or the primary winding structure is not energized. Thus, no alternating electromagnetic field is generated by the primary winding structure. In contrast, if a correctly positioned vehicle is detected by the vehicle detection system, the control unit can control the inverter such that a desired power transfer field is generated.

In another embodiment, the vehicle detection system comprises a RFID (radio frequency identification) unit. The RFID unit can be arranged within the housing, in particular within the inner volume of the housing. Using the RFID unit, a vehicle and, if applicable, a position of the vehicle with respect to the IPT pad can be detected. Thus, the RFID unit can be used as an element, in particular a sensor, of the aforementioned vehicle detection system.

In another embodiment, the inductive power transfer pad comprises at least one guiding means for guiding a magnetic flux. In particular, the IPT pad can comprise a ferrite arrangement, wherein the ferrite arrangement can e.g. comprise one or more ferrite bars or slabs. In this case, the ferrite arrangement can be used to guide a magnetic flux of the electromagnetic field which is generated if the primary winding structure is energized. The guiding means can be arranged within the housing, in particular within the aforementioned inner volume. As the magnetic flux can be guided along a desired path, the use of such guiding means for the magnetic flux advantageously increases an efficiency of the inductive power transfer system.

In another embodiment, the inductive power transfer pad can comprise a compensating unit for compensating a self-inductance of the primary winding structure. As the inverter, the compensating unit can be arranged within the housing, in particular within the aforementioned inner volume of the housing. By providing or operating the compensating unit, the self-inductance of the primary winding structure can be compensated which advantageously allows operating the primary winding structure only with a desired active power.

The compensating unit can e.g. comprise one or more compensating capacitors which can be connected in series to the aforementioned phase line(s) of the primary winding structure. A capacitance of the capacitors can be chosen such that the resonant frequency of a resonant circuit provided by the inductance of the phase line and the capacitance is equal or nearly equal to an operating frequency of the primary winding structure, e.g. 20 kHz. Such an arrangement provides a tuned arrangement. The capacitance can be a fixed or a variable capacitance.

Thus, an efficiency of the inductive power transfer can advantageously be increased.

In another embodiment, the inductive power transfer pad comprises a foreign object detection system. The foreign object detection system can be a metal object detection system and/or a moving object detection system. It is possible that the foreign object detection system comprises both, a metal object detection part and a moving object detection part.

Using a foreign object detection system, a foreign object, in particular a foreign metal object such as a coin, a can or another metal object, which is located close to, in particular on a (charging) surface of, the IPT pad can be detected. If the primary winding structure is energized, the resulting power transfer field can induce eddy currents within the foreign object. On the one hand, these eddy currents will reduce the amount of energy which is transferred to the secondary side while, on the other hand, the foreign object can heat up which, in turn, can be dangerous for persons or vehicles.

One, multiple or all elements of the foreign object detection system, in particular sensor elements and control units, can be arranged within the housing, in particular within the aforementioned inner volume of the housing. The detection system can e.g. comprise inductive or capacitive elements. Such elements advantageously allow detecting a foreign object depending on a change of an inductance or capacitance of the aforementioned inductive or capacitive elements. The detection system can e.g. comprise at least one inductive sensing system, wherein the inductive sensing system comprises one or multiple detection winding(s). Multiple detection windings can be arranged in an array structure, wherein the array structure covers a charging surface of the route at least partially. Using an inductive detection system, an active or passive detection can be realized. In the case of an active detection, one or more excitation winding(s) are used. An active object detection is performed by monitoring properties of an excitation field generated by the excitation winding(s). In the case of a passive detection, only one or more passive winding(s) are used. The passive object detection is performed by monitoring properties of the passive winding(s), in particular an inductance.

Such an inductive detection system is disclosed in the GB 1222712.0 (not yet published). In the context of this invention, a detection system can be designed according to one of the embodiments claimed in GB 1222712.0.

In particular, at least one detection winding can be part of a LC oscillating circuit. The LC oscillating circuit comprises at least one capacitive element, e.g. a capacitor. Furthermore, the LC oscillating circuit comprises at least one inductive element, wherein the inductive element is provided at least partially by the detection winding. Furthermore, the LC oscillating circuit comprises a voltage generator which is able to provide an alternating voltage with the resonant frequency of the oscillating circuit. Output terminals of the voltage source are connected to the LC oscillating circuit which is e.g. provided by a parallel connection of the capacitive element and the inductive element. Furthermore, the oscillating circuit can comprise an element with a predetermined impedance, wherein the element can be arranged such that the oscillating circuit is decoupled from the voltage source.

The oscillating circuit is designed such that if a foreign object is placed within the proximity of the detection winding, the oscillating circuit is detuned. In this case, the changed or detuned resonant frequency of the oscillating circuit does not match the operating frequency of the voltage source. The resonant current can decrease significantly if the oscillating circuit is detuned. This will, in turn, result in a voltage drop of the voltage falling across the aforementioned parallel connection.

Depending on the voltage falling across the parallel connection of the inductive element and the capacitive element, the presence of the foreign object in the proximity of the detection winding can be detected. Such a design of a detection winding provides a high detection sensitivity and an increased robustness of detection.

It is also possible that a predetermined number of oscillating circuits are connected parallel to each other, wherein the inductive elements of each of the oscillating circuits are at least partially provided by one detection winding respectively.

The detection system can alternatively comprise at least one capacitive sensing system. In the case of a capacitive detection, the detection system can comprise at least one capacitive sensing system, wherein the capacitive sensing system comprises one or multiple detection capacitors. Multiple detection capacitors can be are arranged in an array structure, wherein the array structure covers the charging surface at least partially. Using a passive detection system, a passive object detection is performed by monitoring properties of the detection capacitor(s), in particular a capacitance.

Such a capacitive detection system is disclosed in the GB 1222713.8 (not yet published). In the context of this invention, a detection system can be designed according to one of the embodiments claimed in GB 1222713.8.

A foreign object detection system can also comprise a microwave transmitting device and a microwave receiving device. The transmitting device and receiving device can comprise or be designed as an antenna. The transmitting device can be designed and/or arranged such that radar waves or microwaves can be emitted along the charging surface. In this case, the waves reflected by the foreign object can be received by receiving device which is built as a radar or microwave sensor. This allows an additional radar-based detection of foreign objects in the proximity of the primary unit.

In particular, the microwave transmitting device can be operated by or comprise a LC generator which generates the microwaves. The LC generator comprises at least one inductive element, one capacitive element and one voltage source. The inductive and capacitive element can be connected in parallel or in series. The voltage source provides voltage with the resonant frequency of the parallel or series connection of the inductive and capacitive element. The LC generator can be designed such that if a stationary, in particular metal, object is located within the proximity of the LC generator, the operating frequency of the LC generator is detuned because of the changed inductance of the inductive element.

In this case, the waves received by the receiving device will have frequency depending on the amount of detuning which, in turn, depends on the change of the inductivity of the LC generator by the foreign object. Based on the changed frequency, a stationary object can be detected. In addition, it is also possible that the change of the frequency of the reflected microwaves can be caused by a moving object. This allows detection of moving objects within a detection range of the microwave transmitter-receiver configuration.

The transmitting device and the receiving device can be designed as elements separate from the detection windings or excitation windings.

In particular, metal objects can be detected by the proposed safety system. Also, moving objects, such as animals or the aforementioned vibrating metal object, can be detected by the proposed safety system due to an evaluation according to the Doppler effect.

It is, however, possible that the moving object detection system can be provided by any system for motion detection.

In another embodiment, the inductive power transfer pad comprises a human-machine- interface and/or signal transmitting means. The human-machine-interface allows providing an input to e.g. the control unit which controls the operation of the inverter. This, in turn, allows adjusting the amount of energy which is transferred inductively or other operational characteristics of the proposed IPT pad.

The signal transmitting and receiving means allow, e.g. wireless, communication with the IPT pad. It is, for instance, possible that a vehicle located above the IPT pad

communicates with the IPT pad. In this way, a driver of the vehicle can activate the inductive charging and/or choose a duration of the charging process and/or choose characteristics, such as the amount of power to be transferred, of the inductive charging process. The signal transmitting and receiving means can also be designed as a data interface, e.g. an interface for a CAN bus for data communication.

The human-machine-interface can also be provided by a monitor or a display which displays information on a status of the IPT pad, e.g. if a charging process is in progress, to a user. For this purpose, the IPT pad can also comprise a display and/or input means such as a keyboard.

Using the signal transmitting and receiving means, said information can be send to the vehicle and then displayed to a driver on a vehicle-sided display. In turn, the driver can input information via vehicle-sided input means, wherein the input data is sent to the pad- sided receiving means.

In another embodiment, at least one phase line of the primary winding structure has a meandering course. In this context, the term "meandering" means that at least one phase line of the primary winding structure extends along the track or route in a meandering manner, i.e. sections of an electric line which provides the phase line which extend in the a longitudinal direction of the IPT pad are followed in the course of the conductor by sections which extend transversely to the longitudinal direction, etc. In the case of a multiphase system with at least two electric phase lines, this preferably applies to all the phase lines.

The expression "meandering" used above covers both the laying of an electric line with smoothly curved transitions (having large radii of curvature) between straight electric line sections as well as configurations with sharp, angular transition regions between adjacent straight sections.

In alternative embodiment, at least one phase line of the primary winding structure is designed such that a course of the phase line provides an even number of sub-windings which are arranged adjacent to each other. In this context, a sub-winding denotes a, preferably complete, conductor loop which encloses a predetermined area. The conductor loop can provide or comprise one turn or multiple turns of the respective sub-winding. Adjacent to each other means that central axes of said sub-windings, in particular the axes of symmetry, are spaced apart from one another, e.g. with a predetermined distance, along a common straight line. In this context, the straight line corresponds to a direction of extension of the primary winding structure. This means that a phase line of the primary winding structure extends in a direction of extension, wherein a predetermined even number of sub-windings is provided along the direction of extension.

Neighboring sub-windings can be counter-oriented. In this context counter-oriented means that a current flow in a first sub-winding is oriented clockwise, wherein the current flow in the neighboring second sub-winding is oriented counter-clockwise. The clockwise direction is defined with respect to the parallel central axes which point into the same direction. If a current flows through the set of sub-windings, the neighboring sub-windings will generate a magnetic field of the same magnitude but oriented in opposite direction.

Such a design of the at least one phase line advantageously allows reducing an installation space required for the primary winding structure. This, in turn, allows an even more compact design of the proposed IPT pad while keeping an active area of the energy transfer constant.

In another embodiment, the course of the phase line is 8-shaped. This means that the phase line comprises two, e.g. circular-shaped, sub-windings which are arranged adjacent to each other along the direction of extension according to the aforementioned

embodiment.

This provides a simple design of the sub-windings.

In an alternative embodiment, at least one phase line of the primary winding structure is designed such that a course of the phase line provides an uneven number of subwindings which are arranged adjacent to each other, in particular along the direction of extension.

In this case, a phase line of the primary winding structure extends in a direction of extension, wherein a predetermined uneven number of sub-windings is provided along the direction of extension. Each sub-winding can provide or comprise one turn or multiple turns.

Preferably, the primary winding structure comprises three phase lines, wherein each phase line comprises three sub-windings which extend along a common direction of extension. Each sub-winding of each phase line can provide or comprise one or multiple turns. Simulations have shown that such a design provides desired properties of a power transfer field emission.

In another embodiment, the inductive power transfer pad comprises at least one cable bearing element. The cable bearing element can be adapted to position and/or to hold a plurality of line sections of one or more electric lines which can provide the phase line(s) of the primary winding structure.

The cable bearing element can comprise recesses forming spaces and/or projections delimiting spaces for receiving at least one of the line sections. The electric line or lines can extend through these spaces. The electric line(s) extend(s) along and/or under the surface of the route, e.g. an (upper) surface of the IPT pad. In particular, the electric line(s) can extend in and/or about a longitudinal direction of the IPT pad which can correspond to the aforementioned direction of extension.

The cable bearing element can be formed as a shaped block which is described in GB 2485616 A or in the GB 1215759.0 (not yet published). Therefore, the disclosure of GB 2485616 A and the GB 1215759.0, in particular the claimed embodiments, is/are incorporated into the present description. In a preferred embodiment, at least one end section of the cable bearing element can have a tapered or frustumed shape.

The cable bearing element can be arranged within the housing, in particular within the aforementioned inner volume of the housing.

This advantageously allows designing a compact IPT pad.

In another embodiment, the inductive power transfer pad comprises a magnetic shielding element. The magnetic shielding element can be used to shield an external area of the IPT pad from the electromagnetic field generated during inductive power transfer. This enhances an electromagnetic compatibility of the IPT pad during operation. The magnetic shielding element can e.g. be made of aluminum.

As the aforementioned elements, the magnetic shielding element can be integrated or arranged in the housing of the IPT pad, in particular within the inner volume of the housing. Further proposed is an inductive power transfer system, in particular for an inductive energy transfer to a vehicle, wherein the inductive power transfer system comprises an inductive power transfer pad according to one of the previously described embodiments. Further, the inductive power transfer system comprises at least one receiving device for receiving an alternating electromagnetic field generated by the primary winding structure of the IPT pad. In particular, the receiving device, which can be also referred to as pickup, can be attached to the vehicle, in particular to a bottom side of the vehicle. The receiving device can comprise the secondary winding structure for receiving the alternating electromagnetic field (power transfer field).

The receiving device can have a housing, wherein the secondary winding structure is arranged within the housing. Also, other elements of the receiving device, e.g. magnetic shielding elements and/or means for guiding a magnetic flux such as ferrite bars or slabs, can be arranged within the housing of the receiving device.

Such an inductive power transfer system advantageously features an increased usability since the IPT pad can be designed a compact fashion, wherein an arbitrary DC voltage and/or AC voltage can be used to operate the IPT pad for inductive power transfer.

In another embodiment, at least one dimension of the inductive power transfer pad is larger than a corresponding dimension of the receiving device. In particular, at least one dimension of the housing of the inductive power transfer pad is larger than corresponding dimension of the housing of the receiving device. In particular, a length and/or a width and/or a height of the housing of the IPT pad can be larger than the corresponding length and/or width and/or height of the housing of the receiving device.

This advantageously increases a positioning space of a vehicle with the receiving device with respect to the IPT pad, in particular above the IPT pad. In particular, it is not necessary to place the receiving device at a specific position or within a very narrow range of positions with respect to the IPT pad in order to provide an efficient inductive power transfer. Since the dimension(s) of the IPT pad is/are larger than the corresponding dimension(s) of the receiving device, the range of feasible relative positions is larger which, in turn, improves a usability of the inductive power transfer system. Preferably, the dimension of the IPT pad is equal to or larger by a factor of 1 .1 than the corresponding dimension of the receiving device.

Further proposed is a method of manufacturing an inductive power transfer pad which comprises the steps of:

- providing a housing,

- providing a primary winding structure,

- providing a connecting terminal.

Furthermore, the method comprises the steps of

- providing an inverter, and

- electrically coupling an input side of the inverter to the connecting terminal and an output side of the inverter to the primary winding structure.

This advantageously allows manufacturing a previously described IPT pad.

In another embodiment, the primary winding structure and the inverter are arranged within the housing, in particular within the inner volume of the housing.

It is of course possible to provide all the other aforementioned elements of the IPT pad and arrange said elements within the housing, in particular within its inner volume, during manufacturing the IPT pad.

This allows providing a very compact IPT pad with a high usability.

Further proposed is a method of operating an inductive power transfer pad according to one of the previously described embodiments. The inverter of the IPT pad is controlled such that a desired electromagnetic field (power transfer field) is generated.

This advantageously allows providing a desired inductive transfer of energy from the IPT pad (primary-sided) to e.g. a vehicle-sided receiving device.

The invention will be explained with reference to the attached figures. The figures show: Fig. 1 a schematic block diagram of a proposed inductive power transfer pad, Fig. 2 a first embodiment of a primary winding structure,

Fig. 3 another embodiment of one phase line of the primary winding structure,

Fig. 4 another embodiment of a primary winding structure,

Fig. 5 an explosion diagram of a proposed inductive power transfer pad,

Fig. 6 a top view on a winding structure of one phase line, and

Fig. 7 a top view on an inductive power transfer pad.

In Fig. 1 , a schematic block diagram of an inductive power transfer pad (IPT pad) 1 is shown. The IPT pad 1 comprises a housing 2 which encloses an inner volume 3 of the housing 2. The IPT pad 1 comprises a first connecting terminal 4 for connecting an external DC voltage to the IPT pad 1 . The first connecting terminal 4 can be designed such that a so called fast charger can be connected to the IPT pad 1 . Such a fast charger provides a predetermined DC voltage. It is possible that the first connecting terminal 4 is designed as a female socket, wherein a male socket of a charging cable (not shown) can be connected to the first connecting terminal 4. It is shown that the first connecting terminal is electrically directly coupled to an inverter 5 which is arranged in the inner volume 3. In the context of Fig. 1 , electric connections for transferring electric power are symbolized by solid lines, wherein connections for data communication are represented by dashed lines. The IPT pad 1 further comprises a second connecting terminal 6 for connecting the IPT pad 1 to an external AC voltage. The external AC voltage can be provided by a common electric network such as a household electric network. The second connecting terminal 6 is electrically connected to the inverter 5 by a rectifier 7 which rectifies the AC voltage provided by the external electric network. The second input terminal 6 can e.g. be used to connect the IPT pad 1 to an external power supply network which provides e.g. an AC voltage with an amplitude of 230V and a frequency of 50Hz.

The rectifier 7 rectifies an AC voltage, wherein an amplitude of the DC voltage generated by rectifying the AC voltage can be varied by the rectifier 7. Furthermore, the rectifier 7 can reduce undesired harmonic components of the AC voltage and reduces a disturbance voltage.

Also shown is a control unit 8 which is arranged within the inner volume 3. The first connecting terminal 4 can provide data communication means for establishing data communication to external elements, e.g. external control units. Therefore, the control unit 8 is connected to the first input terminal 4 via a data line. Furthermore, the IPT pad 1 comprises a vehicle detection system 9. The vehicle detection system 9 can comprise a RFID unit 10. Both, the vehicle detection system 9 and the RFID unit 10 are arranged within the inner volume 3. The vehicle detection system 9 is connected to the control unit 8 via a data line. The vehicle detection system 9 detects a vehicle and its correct location above the IPT pad 1 .

Furthermore, the IPT pad 1 comprises a foreign object detection system 1 1 and a human- machine-interface 12. The foreign object detection system 1 1 can detect if a foreign object is located within a predetermined proximity of the IPT pad 1 . The object detection system 1 1 is connected to the control unit 8 via a data line. If a foreign object is detected, the control unit 8 can interrupt or prevent an inductive power transfer.

A human-machine-interface 12 provides status information on charging process to a user, e.g. a driver of a vehicle to be charged. Furthermore, the human-machine-interface 12 can provide input means for a user in order to control parameters of a charging process, e.g. a charging process duration. The human-machine-interface 12 is connected to the control unit 8 via a data line.

Also shown is a magnetic layer 13 which is used to guide a magnetic flux during inductive power transfer. The magnetic layer 13 can be designed as a ferrite structure, e.g. a ferrite bar or ferrite strip.

It is also possible that the IPT pad 1 comprises a field shaping layer comprising magnetizable material adapted to shape magnetic field lines of the electromagnetic field. The field shaping layer can comprise a plurality of elements made of the magnetizable material, wherein neighbouring elements are positioned at a distance to each other. The distance between two neighbouring elements can be smaller than the extension of the neighbouring elements in the direction across the distance. The elements can be in the shape of tiles. The elements can be evenly distributed over the extension of the field shaping layer in a longitudinal direction 16 of the layer and/or in a lateral direction of the layer. The elements can be fixed to a continuous supporting layer, which can be made of an electrically conducting material. Further shown is a compensating unit 14 which compensate a self-inductance of a primary-side winding structure 15. The compensating unit 14 can comprise one or more capacitive element(s), in particular one or more capacitor(s). A capacitance of the capacitive element(s) is chosen such that a resonant frequency of a resonant circuit comprising at least the capacitive element and an inductive element provided by the primary winding structure 15 matches the desired operating frequency. It is possible that for each phase line of the primary winding structure, at least one compensating capacitive element is provided.

The primary winding structure 15 is designed as a three-phase winding structure. It is electrically connected to the inverter 5. The inverter 5 generates a desired AC voltage which is supplied to the phase lines of the primary winding structure 15. Thus, a desired electromagnetic field, which can also be referred to as power transfer field, is generated. The primary winding structure 15 is located or arranged within the inner volume 3. Also shown is a longitudinal axis of the IPT pad 1 extending into the longitudinal direction 16. This longitudinal direction 16 can be a direction of extension of the phase lines L1 , L2, L3 of the primary winding structure 15 (see e.g. Fig. 2).

It is possible that at least one primary side shielding assembly or a part of the primary side shielding assembly is arranged adjacent to at least a part of the primary winding structure 15 to reduce a field emission in a lateral direction. The primary side shielding assembly can be a ferrite structure. Adjacent means that the ferrite structure is arranged lateral to the primary winding structure 15, wherein the longitudinal direction 16 can be defined as a direction of extension of the primary winding structure 15 and the lateral direction is perpendicular to the longitudinal direction 16. For example, the primary side shielding assembly or a part of the primary side shielding assembly extends sideways of the primary side conductor assembly on the same level as the primary side conductor assembly, thereby shielding regions, which are located beyond the magnetizable material, from the electromagnetic field. Also, the primary side shielding assembly can extend from sideways of the primary side conductor assembly to a level above (with respect to a vertical direction) the level of a lateral edge of the primary side conductor assembly, thereby also shielding regions, which are located beyond the magnetizable material and at a higher level as the lateral edge, from the electromagnetic field. The vertical direction can be perpendicular to the plane of projection of Fig. 1 and point towards an observer. More particular, the primary side shielding assembly can extend into a region above the lateral edge of the primary side conductor assembly, thereby shielding regions, which are located beyond the magnetizable material and above the lateral edge, from the

electromagnetic field. Moreover, a primary side shielding assembly can extend from sideways of the primary side conductor assembly to a level below the level of a lateral edge of the primary side conductor assembly, thereby also shielding regions, which are located beyond the magnetizable material and at a lower level as the lateral edge, from the electromagnetic field. Also, the primary side shielding assembly can extend into a region below the lateral edge of the secondary side conductor assembly, thereby shielding regions, which are located beyond the magnetizable material and below the lateral edge, from the electromagnetic field.

The aforementioned ferrite structure can be designed as a ferrite strip or ferrite bar.

Alternatively, the ferrite structure can have a C-profile, wherein the C-profile is provided in a cross section of the ferrite structure within a section plane perpendicular to the longitudinal direction 16. The ferrite structure can be arranged such that the inner volume comprised by the C-profile is oriented or opened towards the primary winding structure 15.

In Fig. 2, a first embodiment of a primary winding structure 15 is shown. The primary winding structure 15 comprises a first phase line L1 , a second phase line L2 and a third phase line L3. A first phase current 11 , a second phase current I2 and third phase current I3 are shown. A longitudinal direction is symbolized by an arrow 16. All phase lines L1 , L2, L3 are connected at a star point 17. Each phase line L1 , L2, L3 comprises longitudinal sections 18 which extend into the longitudinal direction 16. Furthermore, each phase line comprises lateral sections which extend perpendicular to the longitudinal direction 16.

The phase lines L1 , L2, L3 extend along the longitudinal direction 16 in a meandering manner. This means that sections of each phase line L1 , L2, L3 which extend in the longitudinal direction 16 are followed in the course of the phase line L1 , L2, L3 by sections which extend transversely to the longitudinal direction 16. Consecutive sections which extend transversely to the longitudinal direction 16 of one phase line L1 , L2, L3 can be spaced apart with a distance T_p. A distance between the phase lines L1 , L2, L3 is chosen such that a phase difference of 120 ° between the phase currents 11 , I2, I3 is provided. In Fig. 2 it is shown that a feeding section 20 is arranged at a first side A of the primary winding structure 15, wherein the star point 17 is arranged at an opposite side B of the primary winding structure 15 with respect to a longitudinal axis of the phase lines L1 , L2, L3 which extends in the longitudinal direction 16. The longitudinal direction 16 can correspond to the direction of travel of a vehicle if the vehicle travels straight forward.

In Fig. 3, another layout of a phase line L1 is shown. The phase line L1 is designed such that a course of the phase line L1 provides a first sub-winding 21 and a second sub- winding 22 which are arranged adjacent to each other. The first sub-winding 21 has an axis of symmetry 23, wherein the second sub-winding 22 has an axis of symmetry 24, which is oriented perpendicular to the plane of projection and points towards the observer. With respect to the axis of the symmetry 23 of the first sub-winding 21 , the phase current 11 flows in a clockwise direction through the sections of the phase line L1 which enclose an inner charging area and provide the first sub-winding 21 . In contrast, the phase current 11 flows in a counter-clockwise direction through sections of the phase line L1 which provide the second sub-winding 22 with respect to the axis of symmetry 24 of the second sub-winding 22. The phase line L1 shown in Fig. 3 comprises longitudinal sections 18 which extend in a longitudinal direction 16 and lateral sections 19, which extend in a direction transverse to the longitudinal direction 16. In contrast to the meandering structure shown in Fig. 2, the longitudinal and lateral sections 18, 19 are arranged such that each sub-winding 21 , 22 provides a complete conductor loop. The axes of symmetry 23, 24 are arranged on a common central longitudinal axis of the phase line L1 with a predetermined distance. With respect to the longitudinal direction 16, a front-sided lateral section 19 is spaced apart from rear-sided lateral section 19 of the phase line L1 with a distance n. The phase line L1 shown in Fig. 3 provides two poles, wherein the first sub- winding 21 , in particular the conductor loop providing the first sub-winding 21 , provides the first pole and the second sub-winding, in particular the conductor loop providing the second sub-winding 22, provides the other pole. If a phase current 11 flows through the phase line L1 , the first sub-winding 21 will generate an electromagnetic field which has the same magnitude as an electromagnetic field generated by the second sub-winding 22 but is directed in an opposite direction.

In the arrangement shown in Fig. 3, the phase line L1 starts from a feeding area 20 and returns to said feeding area 20. Within the phase line L1 , the phase current 11 will flow in the same direction through neighboring or adjacent lateral sections 19 of the adjacent sub-windings 21 , 22. The phase line L1 shown in Fig. 3 provides two alternating poles with pole areas being enclosed by the conductor loops, respectively. The ratio of the length of the longitudinal sections and lateral sections 18, 19 can be smaller than one, equal to one or larger than one.

In Fig. 4, an arrangement of three phase lines L1 , L2, L3 and the directions of a first phase current 11 , a second phase current I2 and a third phase current I3 is shown. Each phase line L1 , L2, L3 is designed according to the embodiment shown in Fig. 3. This means that each phase line L1 , L2, L3 is designed such that a course of the phase line L1 , L2, L3 provides two sub-windings 21 , 22 (see Fig. 3) which are arranged adjacent to each other along a common central longitudinal axis which extends in a longitudinal direction 16. Shown is also a feeding area 20 and a star point 17. Each phase line L1 starts at the feeding area 20 and returns to the star point 17 which is located close to the feeding area 20, in particular on the same side of the primary winding structure 15 with respect to the common central longitudinal axis. Lateral sections 19 of the phase lines L1 , L2, L3 are spaced apart with a predetermined distance M in the longitudinal direction 16. This distance M provides a pole pitch of the poles provided by the sub-windings. It is also shown that longitudinal sections 18 of each phase line L1 , L2, L3 are spaced apart with a predetermined distance in a lateral direction which is transverse to the longitudinal direction 16. The shown primary winding structure 15 advantageously allows a very compact design of the primary winding structure 15.

A distance between the phase lines L1 , L2, L3 is chosen such that a phase difference of 60° between the phase currents 11 , I2, I3 is provided.

It can be seen that the phase lines L1 , L2, L3 overlay each other. The distance M can be chosen such that the phase lines L1 , L2, L3 are mutually decoupled.

In Fig. 5, an explosion view of an IPT pad 1 according to the invention is shown. The IPT pad 1 comprises an aluminum plate 25 which provides a shielding element. Furthermore, the aluminum plate provides a base plate of a housing 2 of the IPT pad 1 . Furthermore, the IPT pad 1 comprises a frame 26 which provides sidewalls of the housing 2. The frame 26 comprises four sidewalls 27, in particular a front sidewall 27a, a rear sidewall 27b and two longitudinal sidewalls 27c. Also, the frame 26 also comprises a supporting layer 28. The supporting layer 28 can have a grid shape which comprises division bars extending in a longitudinal direction 16 and division bars extending in a lateral direction which is transverse to the longitudinal direction 16. The supporting layer 28 is used to carry ferrite elements 29, wherein the supporting layer 28 is designed such that ferrite elements 29 are arranged in a predetermined position. These ferrite elements 29 provide the magnetic layer 13 shown in Fig. 1 . These ferrite elements 29 are used to shape magnetic field lines of an electromagnetic field generated by the primary winding structure 15 which is also shown in Fig. 5. The primary winding structure 15 comprises three phase lines L1 , L2, L3 as shown in Fig. 7. Also shown is a cable bearing element 30 which will be arranged within the frame 26. Within guiding channels of the cable bearing element 30, the phase lines L1 , L2, L3 are arranged.

The sandwich construction shown in Fig. 5 advantageously allows using a magnetizable material, e.g. the ferrite elements 29, in order to shield a part of the surroundings of the IPT pad 1 , in particular an area below the primary windings structure 15, from

electromagnetic field generated by the primary winding structure 15 during inductive power transfer. For this, the shielding element provided by the aluminum plate 25 is combined with a further shielding assembly comprising the ferrite elements 29. In this case, the shielding assembly comprises electrically conducting material, which is, in particular, not magnetizable material. In particular, the electric conductivity of the electrically conducting material is higher than the electric conductivity of the magnetizable material by a factor of at least 1 .000, preferably by a factor of at least 10.000. For example, in practice, the electric conductivity of the ferrite elements 29 may be in the range of 10^~7 to 1 A/(Vm) and the electric conductivity of the electrically conducting material (for example of the aluminum plate 25) may be in the range of 10⁶ to 10⁸ A/(Vm). In Fig. 5 it is shown that the shielding assembly extends below the primary winding structure 15 with respect to a vertical direction which extends from the base plate to a top cover 34.

The cable bearing element 30 is adapted to position and/or to hold a plurality of line sections of the phase lines L1 , L2, L3. The cable bearing element 30 can comprise recesses spaces and/or projections delimiting spaces for receiving at least one of the line sections. The electric line or lines of the phase lines L1 , L2, L3 can extend through these spaces. Longitudinal sections of the recesses extend in the longitudinal direction 16 and lateral sections of the recesses extend in the aforementioned lateral directions. Thus, the lateral sections extend perpendicular to the longitudinal sections. The IPT pad 1 further comprises a bottom cover 31 for the cable bearing element 30. The bottom cover 31 is used to cover the open recesses of the cable bearing element 30 after the phase lines L1 , L2, L3 are arranged within the recesses.

Furthermore, the IPT pad 1 comprises spacing elements 32 for the winding structure 15, in particular each phase line L1 , L2, L3, more particular for the winding heads 33 of each phase line L1 , L2, L3. A winding head 33 denotes a lateral sub section of each phase line L1 , L2, L3 which extends into the longitudinal direction 16.

The spacing elements 32 are used in order to provide and maintain a predetermined distance between the phase lines L1 , L2, L3 of the winding structure 15.

The IPT pad 1 further comprises a top cover 34 which is used to cover the housing 2. The top cover has a marking 35 which extends into the longitudinal direction 16. This means that a length of the marking 35 in the longitudinal direction 16 is longer than a width of the marking 35 in the lateral direction. The marking is used to indicate the longitudinal direction 16 to e.g. a driver of a vehicle. Thus, a vehicle can be positioned over the IPT pad 1 by controlling the vehicle such that the longitudinal direction 16 corresponds to a direction of travel if the vehicle is traveling straight forward.

Furthermore, the IPT pad 1 comprises a metal detection board 36 which comprises a metal object detection system. By the metal object detection system, a foreign metal object placed on or close to an upper surface of the top cover 34 can be detected.

The IPT pad 1 further comprises compensating capacitors 37, wherein only one capacitor 37 is referenced. The capacitors 37 are installed on an isolating carrier plate 38.

Furthermore, the IPT pad 1 comprises an inverter 5 which is also installed on the isolating carrier plate 38. Also shown is that the IPT pad 1 comprises a rectifier 7. Also shown is an opening 39 in the rear side wall 27b which provides an access to a second input terminal 6 (see Fig. 1 ). Not shown is an electric connection between the rectifier 7, the inverter 5 and the capacitors 37 which can e.g. be provided by busbars. Fig. 5 shows also fixations holes 40 within the lateral side walls 27c of the housing 2. Through these fixations holes 40, the frame 27 can be attached to the aluminum plate 25 and to the ground.

Fig. 6 shows a top view on a phase line L of a primary winding structure 15 (see Fig. 5). The phase line L comprises three sub-windings SW1 , SW2, SW3. Each sub-winding SW1 , SW2, SW 3 provides one or multiple turns of the phase line L.

The phase line L extends in a direction of extension which corresponds to a longitudinal direction 16. Along the direction of extension, the three sub-windings SW1 , SW2, SW3 are provided adjacent to each other. This means that the sub-windings SW1 , SW2, SW3 are arranged consecutively. Axes of symmetry A1 , A2, A3 of each sub-winding SW1 , SW2, SW3 are arranged along the direction of extension with a predetermined distance.

Consecutive sub-windings SW1 , SW2, SW3 are counter-oriented.

Each sub-winding SW1 , SW2, SW3 comprises lateral sections LAS, wherein the phase line L extends in a lateral direction which is perpendicular to the longitudinal direction. Also, each subwinding SW1 , SW2, SW3 comprises longitudinal sections LOS, wherein the phase line L extends in the longitudinal direction 16. The longitudinal sections LOS can provide so-called winding heads 33 (see Fig. 5) of the sub-windings SW1 , SW2, SW3.

Within transition sections between the lateral sections LAS and the longitudinal sections LOS, the phase line can extend in a vertical direction which is perpendicular to the longitudinal direction 16 and the lateral direction. With respect to this vertical direction (which is oriented perpendicular to the plane of projection), the lateral sections LAS and the longitudinal sections LOS can be arranged at different levels.

If more than one phase line L is used, the vertical distance between the lateral sections LAS and the longitudinal sections LOS of each phase line L can be different. This advantageously allows a compact design of a winding structure 15 (see Fig. 5) with more than one phase line L.

Fig. 7 shows a top view on an inductive power transfer pad 1 shown in Fig. 5. The winding structure 15 comprises three phase lines L1 , L2, L3. Phase lines L1 , L2, L3 are designed as the phase line L shown in Fig. 6. As mentioned before, the vertical distance between the lateral sections LAS and the longitudinal sections LOS of each phase line L1 , L2, L3 are different. Thus, it is shown that the longitudinal sections LOS of each phase line L1 , L2, L3 partially overlap in a vertical direction.

Claims

1 . An inductive power transfer pad, in particular an inductive power transfer pad (1 ) of a system for inductive power transfer to a vehicle, comprising:

- a housing (2),

- a primary winding structure (15),

- a connecting terminal (4, 6),

characterized in that

the inductive power transfer pad (1 ) further comprises an inverter (5), wherein the inverter (5) is arranged within the housing (2), wherein an input side of the inverter (5) is electrically coupled to the connecting terminal (4, 6) and an output side of the inverter (5) is electrically coupled to the primary winding structure (15).

2. The inductive power transfer pad of claim 1 , wherein the inductive power transfer pad (1 ) comprises a rectifier (7), wherein the inverter (5) is coupled to the connecting terminal (6) via the rectifier (7).

3. The inductive power transfer pad of claim 2, wherein the inductive power transfer pad (1 ) comprises another connecting terminal (4), wherein the inverter (5) is coupled directly to the other connecting terminal (4).

4. The inductive power transfer pad of one of the claims 1 to 3, wherein the input of the inverter (5) is coupled directly to the connecting terminal (4).

5. The inductive power transfer pad of one of the claims 3 or 4, wherein the inductive power transfer pad (1 ) is connected to a DC current generator, wherein a desired DC voltage is generatable by the DC generator.

6. The inductive power transfer pad of one of the claims 1 to 5, wherein the inductive power transfer pad (1 ) comprises a control unit (8) for controlling an operation of the inverter (5).

7. The inductive power transfer pad of one of the claims 1 to 6, wherein the inductive power transfer pad (1 ) comprises a vehicle detection system (9).

8. The inductive power transfer pad of one of claim 7, wherein the vehicle detection system (9) comprises a RFID unit (10).

9. The inductive power transfer pad of one of the claims 1 to 8, wherein the inductive power transfer pad (1 ) comprises at least one guiding means for guiding a magnetic flux.

10. The inductive power transfer pad of one of the claims 1 to 9, wherein the inductive power transfer pad (1 ) comprises a compensating unit (14) for compensating a self inductance of the primary winding structure (15).

1 1 . The inductive power transfer pad of one of the claims 1 to 10, wherein the inductive power transfer pad (1 ) comprises a foreign object detection system (1 1 ).

12. The inductive power transfer pad according to claim 1 1 , wherein the foreign object detection system (1 1 ) is a metal object detection system.

13. The inductive power transfer pad according to claim 12, wherein the foreign object detection system (1 1 ) is a moving object detection system.

14. The inductive power transfer pad of one of the claims 1 to 13, wherein the inductive power transfer pad (1 ) comprises a human machine interface (12) and/or signal transmitting and receiving means.

15. The inductive power transfer pad of one of the claims 1 to 14, wherein at least one phase line (L1 , L2, L3) of the primary winding structure (15) has a meandering course.

16. The inductive power transfer pad of one of the claims 1 to 14, wherein at least one phase line (L1 , L2, L3) of the primary winding structure (15) is designed such that a course of the phase line (L1 , L2, L3) provides an even number of subwindings (21 , 22) which are arranged adjacent to each other.

17. The inductive power transfer pad according to claim 16, wherein the course of the phase line (L1 , L2, L3) is 8-shaped.

18. The inductive power transfer pad of one of the claims 1 to 14, wherein at least one phase line (L1 , L2, L3) of the primary winding structure (15) is designed such that a course of the phase line (L1 , L2, L3) provides an uneven number of subwindings (21 , 22, 23) which are arranged adjacent to each other.

19. The inductive power transfer pad of one of the claims 1 to 18, wherein the inductive power transfer pad (1 ) comprises a cable bearing element (30).

20. The inductive power transfer pad of one of the claims 1 to 19, wherein the inductive power transfer pad (1 ) comprises a magnetic shielding element.

21 . An inductive power transfer system, in particular for an inductive energy transfer to a vehicle, comprising an inductive power transfer pad (1 ) according to one of the claims 1 to 19 and at least one receiving device for receiving an alternating electromagnetic field generated by a primary winding structure (15) of the inductive power transfer pad (1 )-

22. The inductive power transfer system according to claim 21 , wherein at least one

dimension of the inductive power transfer pad (1 ) is larger than a corresponding dimension of the receiving device.

23. A method of manufacturing an inductive power transfer pad, comprising the steps of:

- providing a housing (2),

- providing a primary winding structure (15),

- providing a connecting terminal (4, 6),

characterized in that

the method further comprises the steps of

- providing an inverter (5),

- arranging the primary winding structure (15) and the inverter (5) within the housing (2),

- electrically coupling an input side of the inverter (5) to the connecting terminal (4, 6) and an output side of the inverter (5) to the primary winding structure (15).

24. A method of operating an inductive power transfer pad according to one of the claims 1 to 20, wherein the inverter (5) is controlled such that a desired electromagnetic field is generated.