GB2543343A

GB2543343A - Receiving device for receiving an electromagnetic field and for producing an alternating electric current by magnetic induction, method of operating the recei

Info

Publication number: GB2543343A
Application number: GB1518312.2A
Authority: GB
Inventors: Wirth Christian
Original assignee: Bombardier Transportation GmbH
Current assignee: Alstom Transportation Germany GmbH
Priority date: 2015-10-16
Filing date: 2015-10-16
Publication date: 2017-04-19
Also published as: WO2017064184A1; GB201518312D0

Abstract

A receiving device 3 for receiving an electromagnetic field and producing an alternating current by magnetic induction comprises at least one phase line 13 and first and second electric connections 19, 29. Each phase line comprises a number of inductances L11-33 that produce an AC voltage by magnetic induction during operation of the receiving device. The first connection connects the phase line(s) to a first load 7 and the second connection connects the phase line(s) to a first load and/or a second load . The first and second connections have first and second resonant frequencies respectively, formed by the inductances of the phase line(s) and capacitances of the phase line(s) C11-C33 or the connections C1x, C2x, C3x, CL. The circuits formed by the first and second connections comprise different sections of the phase line(s) and therefore have different resonant frequencies. The arrangement is particularly suitable for generating energy for operating an electric or hybrid vehicle

Description

Receiving device for receiving an electromagnetic field and for producing an alternating electric current by magnetic induction, method of operating the receiving device and method of manufacturing the receiving device

The invention relates to a receiving device for receiving an electromagnetic field and for producing an alternating electric current by magnetic induction, in particular for generating electric energy for operating a vehicle. The invention also relates to a method of operating the receiving device and to a method of manufacturing the receiving device.

Electric vehicles, in particular a track-bound vehicle (such as trams) and/or a road automobile (such as private vehicles or public transport vehicles, like buses), can be operated at least partially by electric energy which is transferred to the vehicle by means of an inductive power transfer system. The vehicle comprises a receiving device for receiving the electromagnetic field generated by a primary side generating device of the inductive power transfer system. The receiving device produces an alternating electric current by magnetic induction, while the electromagnetic field is received and while a load is connected to the receiving device. A rectifier may be connected to the receiving device for converting the alternating electric current (AC) to a direct current (DC). The DC can be used to charge a traction battery, to operate a propulsion motor of the vehicle and/or to operate other loads, for example via an electric network on board the vehicle. Such an inductive power transfer system is described, for example, in WO 2010/031595.

Typically, the primary side generating device which generates the electromagnetic field is operated using a constant alternating current, i.e. an alternating current having a constant amplitude. This has the advantage that the same current flows through the generating device independent of the power which is actually transferred to the vehicle or the vehicles.

In some cases, the energy storage on board the vehicle is to be charged and the charging power depends on the charging state and possibly on other parameters of the electric system on board the vehicle. One way of varying the power transferred from the primary side generating device to the secondary side receiving device on board the vehicle is to vary the gap between the generating device and the receiving device. Thereby, the charging voltage of the battery charger on board the vehicle can be adjusted. However, in case of a constant alternating current through the primary side generating device, the same resistive losses would be generated in the generating device independent of the power transferred to the vehicle. If the transferred power would be reduced for example to less than 50% of the maximum possible transferred power, the resistive losses would be still the same as with the maximum power and the percentage of the resistive losses would be significantly higher than during operation at maximum power.

It is an object of the present invention to provide a receiving device for receiving an electromagnetic field and for producing an alternating electric current by magnetic induction which enables an inductive power transfer system to reduce the losses during partial load operation.

It is a basic idea of the present invention to use different electric connection points to the phase line or phase lines of the receiving device, depending on the power level which is to be transferred to the receiving device from the primary side generating device. The load or the loads is/are connected to the respective connection point (or set of connection points) depending on the mode of operation. The different electric circuits which are formed by the phase line or phase lines and the electric connection from the connection point to the load have different electrical properties for the different connection points (or sets of connection points). In particular, each electric circuit has a different resonance frequency. Therefore, the resonance frequency of a first electric circuit using a first connection point may be smaller than for a second electric circuit using a second electric connection point to the phase line(s) of the receiving device. Therefore, it is possible to operate the inductive power transfer system at the respective resonance frequency in order to transfer power at different power levels to the load(s) which is/are connected to the receiving device. For example, at high power transfer level, the electric connection point(s) corresponding to the first electric circuit and the lower resonance frequency can be used. At partial power transfer level (e.g. in the range of 10 to 50 percent of the maximum power level) the frequency of the electromagnetic field produced by the primary side generating device can be smaller so as to correspond to the resonance frequency of the second electric circuit which uses the second electric connection point(s) for transferring the received power from the receiving device to the load(s). Operating the system at the resonance frequency of the receiving device has the advantage that power transfer is efficient. However, it is in particular possible to generate the electromagnetic field by the generating device with at least two different frequency components. It is therefore possible, to transfer the power received by the receiving device via the different electric connections at the same time.

If a smaller primary side generating device, or a smaller region of the same primary side generating device, is used during partial load power transfer compared to the full power transfer, the generated electromagnetic field (i.e. zones having a field intensity above a predetermined threshold value) can be restricted to the active part of the secondary side receiving device. In the terminology used below, the active part corresponds to the active section(s) of the phase line(s). Therefore, the field intensity in the non-active part of the receiving device can be kept below the threshold value. Consequently, the magnetic induction in the non-active part is small. In practice, this is achieved by aligning the primary side generating device or the active region of the primary side generating device with the active part of the secondary side receiving device. For example, these active devices or parts may be placed in close proximity to each other so that the magnetic field line of the electromagnetic field having the highest field intensity passes through the centre of the primary side generating device or of the active region of the primary side generating device and also passes through the centre of the active part of the secondary side receiving device.

It is another basic idea of the present invention to use a receiving device having a distributed impedance. This means that the phase line or the phase lines in which the alternating electric current is produced by magnetic induction, form the total impedance of the receiving device distributed over the extension of the phase line or phase lines. Preferably, compensating capacitances for reducing the reactive power and for defining the resonance frequency together with the impedance or impedances involved, are also distributed over the extension of the electric phase line or electric phase lines. This allows for connection points in between the different capacitances within the same phase line and, therefore, meeting the requirements of small reactive power and desired resonance frequency is facilitated compared to a single capacitance per phase line. In particular, each of several sections of the same phase line may comprise at least one capacitance of the same value and all section of the same phase line may have equal lengths. In this case, there may be a connection point for connecting a connection line to a load at each interface between these sections of the phase line.

One possibility to realize a phase line having a distributed impedance is to connect different coils of an electric line to each other. Each coil may be connected in series to a capacitance. However, it would also be possible to realize the basic idea of the present invention by using a single coil for each phase line and to provide at least one additional electric connection point between the ends of the coil. For a single intermediate electric connection point, which can be shifted along the extension of the electric phase line, this corresponds to an auto-transformer.

The receiving device may comprise a single phase line, which means that a one-phase alternating electric current would be produced by magnetic induction. However, some receiving devices comprise more than one phase line, for example three phase lines which are connected to each other at a star point. The other end of the three phase lines may be connected to a rectifier for rectifying the induced alternating electric current to a direct current for providing at least one load with energy. Other receiving devices may comprise two or more than three phase lines. In case of more than one phase line and the star point connection mentioned before, one set of electric connection points for connecting the receiving device to a load may be at the ends of the phase lines opposite to the star point connection. At least one further set of electric connection points is then located in between the opposite ends of the phase lines. This means that each of the phase lines has at least one additional electric connection point in between its opposite ends. The term “opposite” refers to the extension of the electric line. Opposite ends are therefore not necessarily located on opposite sides of the phase line. In particular, the electric line forming the phase line can be wound to at least one coil as mentioned above and the ends of the coil may be located on the same side of the coil. The star point connection of several phase lines is only one example. Another example is a delta-connection.

In particular, the following is proposed: A receiving device for receiving an electromagnetic field and for producing an alternating electric current by magnetic induction, in particular for generating electric energy for operating a vehicle, wherein the receiving device comprising: • at least one electric phase line for carrying a phase of the alternating electric current, wherein sections of the electric phase line (or of each of the phase lines in case of more than one phase line form inductances that produce an alternating electric voltage by magnetic induction during operation of the receiving device, • a first electric connection being connected or connectable to at least one first connection point of the at least one phase line for connecting the at least one phase line to a first electric load, wherein the first electric connection and the section or sections of the at least one electric phase line which can be connected via the first electric connection to the first electric load form a first electric circuit having a first resonance frequency defined by the inductance or inductances of the section or sections and by at least one capacitance of the at least one electric phase line and/or the first electric connection, • a second electric connection being connected or connectable to at least one second connection point of the at least one phase line for connecting the at least one phase line to the first electric load and/or to a second electric load, wherein the second electric connection and the section or sections of the at least one electric phase line which can be connected via the second electric connection to the first electric load and/or to the second electric load form a second electric circuit having a second resonance frequency defined by the inductance or inductances of the section or sections and by at least one capacitance of the at least one electric phase line and/or the second electric connection, wherein the first electric circuit and the second electric circuit comprise different sets of in each case at least one section of the at least one electric phase line, so that a first total inductance of the first electric circuit differs from a second total inductance of the second electric circuit and, thereby, the first resonance frequency differs from the second resonance frequency.

In addition, a method is proposed of operating a receiving device for receiving an electromagnetic field and for producing an alternating electric current by magnetic induction, in particular for generating electric energy for operating a vehicle, and the method comprising: • producing an alternating electric voltage by magnetic induction and, thereby, producing the alternating electric current through at least one electric phase line of the receiving device, wherein sections of the electric phase line (or of each of the phase lines in case of more than one phase line) form inductances that produce the alternating electric voltage, • in a first operating state, using a first electric connection to at least one first connection point of the at least one phase line for providing energy from the at least one phase line to a first electric load while the first electric connection is connected to the at least one first electric connection point of the at least one electric phase line, wherein the first electric connection and the section or sections of the at least one electric phase line which are connected via the first electric connection to the first electric load form a first electric circuit having a first resonance frequency defined by the inductance or inductances of the section or sections and by at least one capacitance of the at least one electric phase line and/or of the first electric connection, • in a second operating state, using a second electric connection to at least one second connection point of the at least one phase line for providing energy from the at least one phase line to the first electric load and/or to a second electric load while the second electric connection is connected to the at least one second electric connection point of the at least one electric phase line, wherein the second electric connection and the section or sections of the at least one electric phase line which are connected via the second electric connection to the first electric load and/or to the second electric load form a second electric circuit having a second resonance frequency defined by the inductance or inductances of the section or sections and by at least one capacitance of the at least one electric phase line and/or of the second electric connection, wherein the first electric circuit and the second electric circuit comprise different sets of in each case at least one section of the at least one electric phase line, so that a first total inductance of the first electric circuit differs from a second total inductance of the second electric circuit and, thereby, the first resonance frequency differs from the second resonance frequency.

Also, a corresponding method of manufacturing a receiving device, in particular the receiving device mentioned above, and its embodiments belongs to the present invention.

Embodiments of the methods of operating a receiving device and of manufacturing a receiving device follow from the description of the embodiments of the receiving device.

Kinds of vehicles to which the energy can be or is provided are mentioned above.

Providing different electric circuits (at least the first and the second electric circuit) by providing and using different sets of sections in the different operation modes, wherein the different electric circuits have different resonance frequencies, enables the primary side generating device of the inductive power transfer system being operated in different manners. Therefore, partial load operation is possible in at least one of the operation modes while reducing the electric losses of the generating device and its power supply compared to maximum load operation. In particular, the alternating electric current through the generating device can be reduced while the generating device is operated at the higher resonance frequency of partial load operation. The term “generating device” covers different cases. For example the same unit of the generating device may be operated in different manners during the first operation mode and the second operation mode. Alternatively, different units of the generating device may be used during different operation modes. A first unit may be used during the first operation mode and a second unit may be used during the second operation mode.

From the description of the primary side generating device follows, that the invention also relates to an inductive power transfer system comprising the generating device and the receiving device, to a method of manufacturing such a system and to a method of operating such a system.

The first electric connection and/or the second electric connection may be connected permanently to the respective connection point(s). Since the resonance frequencies of the first electric circuit and the second electric circuit differ, and since the different electric connections are electrically parallel to each other with respect to the phase line(s) and the load(s), inducing an alternating electric current which oscillates with one of the resonance frequencies only produces a significant load current through only one of the electric connections. The load current through the other electric connection(s) is small, since the corresponding electric circuit has a different resonance frequency. As mentioned before, the invention is not limited to two electric connections from the phase line(s) to the load(s). Furthermore, the first electric connection and the second electric connection could comprise sections of the same electric line, according to a specific embodiment. For example, the first electric connection may connect one end of the phase line(s) with a rectifier in the first operating state and may be disconnected from the end of the phase line(s) in the second operating state, for example by opening a corresponding switch or set of switches at the end of the phase line(s). Furthermore, in the second operating state, the electric line(s) of the first electric connection may be connected in series to a further electric line or to further electric lines which connect(s) the rectifier to the at least one second electric connection point in the phase line(s). Thereby, the first electric connection and the further electric line(s) form the second electric connection in the second operating state. If the first and second electric connections are connected to the same load, in particular via the same rectifier, this has the advantage that no additional device is required for connecting the connections to a load, in particular no additional rectifier.

It is mentioned above that the respective section or sections of the at least one electric phase line can be connected or is connected via the respective electric connection to a load. It is understood that this section or sections carry/carries the induced alternating electric current which flows through the respective connection to the load. Of course, one of the electric connections, in particular the second electric connection being part of the second electric circuit having the higher resonance frequency, is also connected to a section or sections of the at least one phase line which is/are not carrying the alternating electric current that flows through the connection line. Therefore, the expression “section or sections of the at least one electric phase line which can be connected via the respective electric connection to the load” refers to the section or sections which carry the alternating electric current which flows through the electric connection to the load (or of the loads).

As mentioned above, a phase line having a distributed impedance can be realized by connecting different coils of an electric line to each other. In particular each of the sections of the electric phase line or of each of the electric phase lines can be formed by a coil of an electric line. In this case, all of the connection points for connecting a phase line to an electric connection (and thereby to the load or loads) are located in between different coils or at the end of a phase line. In particular, the second connection point is located in between different coils of the same phase line in this case.

The term “which can be connected via the respective electric connection to the load or loads” refers to the fact that the load or loads is/are not part of the receiving device. The respective electric connection may or may not be connected permanently to the at least on phase line.

As mentioned before, each section of the phase line or of each of the phase lines may comprise an inductance in which an electric voltage is induced during operation.

Therefore, the total inductance of the phase line or of each of the phase lines is formed by the individual inductances of all sections of the phase line. In at least one of the operating states, in particular in the second operating state, not all of the sections of the phase line or of each of the phase lines carry the alternating electric current which flows through the electric connection to the load(s).

As mentioned above, the field intensity in the non-active part of the receiving device can be kept below a threshold value. Therefore, with respect to the second operating state, the section or sections of the second electric circuit may receive the electromagnetic field at a field intensity above a predetermined threshold value and a remaining section or remaining sections of the at least one phase line, which does/do not belong to the second electric circuit, receive(s) the electromagnetic field at a field intensity below the predetermined threshold value.

According to an optional design of the receiving device, the capacitance which is required to form a resonant electric circuit may be arranged within the electric connection and no additional discrete elements having a capacitance may be arranged within the phase line(s). However, this embodiment is not preferred. It is preferred, as mentioned above, that each section of the phase line(s) comprises a compensating capacitance, in particular formed by at least one discrete element, so that the reactive power is minimized during operation. However, this does not exclude the possibility that the electric connection also comprises at least one discrete element having a capacitance.

The concept that the alternating electric current which flows through the electric connection in at least one of the operating states does not flow through all sections of the phase line or phase lines has been explained above. The section or sections which actually carry the alternating electric current, which current also flows through the electric connection, form the respective set mentioned above.

Each set of the at least one electric phase line comprises at least one section per phase line. Therefore, in case of a single phase line, a set may consist of one section only. Sections may be defined by interfaces between neighboring sections, which in turn may be defined by one of the electric connection points and/or by at least one discrete element having a capacitance.

In particular, the second electric connection may comprise at least one capacitance being part of the second electric circuit, the capacitance determining the second resonance frequency together with the section or sections of the at least one phase line in the second electric circuit. This capacitance can be chosen in a manner so that the second electric circuit has a desired, predetermined resonance frequency. An equation for calculating the capacitance within the second electric connection will be stated below with respect to the attached figures. Optionally, the second electric connection may comprise at least one additional discrete inductive element (such as a coil) being part of the second electric circuit. By choosing the inductance of the inductive element(s), the second resonance frequency can be adapted to a desired value, such as the resonance frequency of the primary side generating device during partial load power transfer.

In particular, the section or sections of the at least one electric phase line which are part of the first electric circuit has/have a larger impedance than the section or sections of the electric phase line which are part of the at least one second electric circuit and wherein the first resonance frequency is smaller than the second resonance frequency. Since, in case of a series resonant circuit with at least one capacitance and at least one inductance being connected in series to each other, the resonance frequency of the electric circuit is proportional to the inverse of the square root of the product of the capacitance(s) and the impedance(s), using a section or sections having a smaller impedance facilitates designing/using an electric circuit which has a larger resonance frequency.

As mentioned above, the first electric connection may be connected to a first rectifier for rectifying the alternating electric current and providing a direct current to the first electric load. This makes it possible to use the electric energy produced by the receiving device for a DC load, such as a battery charger and a battery on board a vehicle. In this case, the second electric connection may optionally be connected to a second rectifier for rectifying the alternating electric current and for providing a direct current to the first electric load and/or to the second electric load. Thereby, different loads (and/or the same load) can be provided with energy during the first and second operating states. However, two different rectifiers also have the advantage that the rectifiers can be designed to be operated at different power levels. In particular, the first resonance frequency may be smaller than the second resonance frequency and the first rectifier may be designed for a larger maximum power provided by the receiving device during operation than the second rectifier.

According to a specific embodiment which allows for an additional operation mode using an electric circuit having a further resonance frequency, the second electric connection can be switched alternatively to be connected to the at least one second connection point of the at least one phase line or to be connected to at least one third connection point of the at least one phase line, so that the second connection forms the second electric circuit, if it is connected to the at least one second connection point of the at least one phase line, or forms a third electric circuit, if it is connected to the at least one third connection point, wherein the third electric connection is adapted to connect the at least one phase line to the first electric load and/or to the second electric load and/or to a third electric load, wherein the second electric connection and the section or sections of the at least one electric phase line which can be connected via the at least one third electric connection point and via the second electric connection to the first electric load, to the second electric load, and/or to the third electric load form a third electric circuit having a third resonance frequency being different from the first resonance frequency and from the second resonance frequency. The third electric circuit and the second electric circuit comprise different sets of in each case at least one section of the at least one electric phase line, so that a third total inductance of the third electric circuit differs from the second total inductance of the second electric circuit. The effort of providing a third electric circuit is low, since the second electric connection is used.

Examples of the present invention will be described with reference to the attached figures. The individual figures show:

Fig.1 an inductive power transfer system comprising a generating device, a receiving device and a rectifier which is connected to a load,

Fig. 2 a simplified representation of the receiving device and the rectifier shown in

Fig. 2,

Fig. 3 a receiving device having two electric connections which are attached to different connection points of a three-phase receiving device,

Fig. 4 a schematic top view of a single phase line having four coils.

Fig. 1 schematically shows an inductive power transfer system comprising a primary side generating device 1 and a secondary side receiving device 3 having three phase lines 13a, 13b, 13c. At one of their ends, the phase lines 13 are connected to each other at a star point 14. At their opposite ends, the phase lines 13 are connected to in each case one branch 16a, 16b, 16c of a rectifier 5. Each branch 16 comprises a series connection of two diodes D11, D12; D21, D22; D31, D32. The phase lines 13 are connected to a connection point 17a, 17b, 17c in between the diodes of each branch 16. A smoothing capacitance CL is connected in parallel to the branches 16 of the rectifier 5. A load 7, such as a vehicle battery, is connected to the opposite connections of the capacitance CL and, thereby, to the opposite ends of the three branches 16 of the rectifier 5. The connection from one end of the branches 16 to the capacitance CL may comprise a switch S1, which can be switched on and off, thereby enabling or disabling operation of the receiving device 3 and the rectifier 5. There may be an additional controllable switch S2 in the connection from the rectifier 5 to the load 7.

The three phase lines 13 of the receiving device 3 are connected to the connection points 17 of the rectifier 5 by an electric connection 19 comprising one connection line 19a, 19b, 19c for each of the phase lines 13a, 13b, 13c. The connection 19 connects connection points 15a, 15b, 15c at the ends of the phase lines 13 to the connection points 17a, 17b, 17c of the rectifier 5.

The generating device 1, which is schematically shown without any details in Fig. 1, is typically operated with a constant alternating current during operation, according to the prior art. The amplitude of the constant current does not depend on the power which is actually transferred from the generating device 1 to the receiving device 3. According to the prior art, the gap between the generating device 1 and the receiving device 3 can be varied in order to vary the power transferred, thereby varying the voltage induced in the phase lines 13 of the receiving device 3 so that the battery 7 can be charged with the required charging voltage. However, the resistive losses produced within the generating device 1 are constant as well, so that the ratio of the loss power to the transferred power increases with decreasing transferred power. For a system having a maximum transferred power of e.g. 200 kW, the electric current through the generating device 1 may be 400 A at a frequency of 20 kHz, for example. This may produce resistive losses in the generating device 1 at a power of 3 kW. If the transferred power would be 50 kW only, during partial load operation, the ratio of the loss power to the transferred power would be 6 %. If the transferred power would become even smaller, the ratio would become unacceptably high.

For efficient partial load operation, the receiving device comprises sections in each phase line and different electric connection points at the interfaces between neighboring sections for connecting a load. In the example shown in Fig. 1, each of the three phase lines 13a, 13b, 13c comprises three sections. Each section comprises a series connection of a capacitance and an inductance. The possible connection points at the interfaces between neighboring sections are represented in Fig. 1 by a small solid circle. The capacitances of the first phase line 13c are represented by the letter C followed by the reference numeral 1 and followed by one further reference numeral for indicating the order number of the section. The inductances are represented by the letter L followed by two reference numerals in the same manner. The capacitances C and the inductances L of the other two phase lines 13a, 13b are represented by reference signs in the same manner as described for the first phase line 13c in Fig. 1. Therefore, for example, the second section of the second phase line 13b comprises a series connection of a capacitance C22 and an inductance L22. Each capacitance and each inductance may be realized by a single discrete element or by a partial circuit comprising more than one discrete element in parallel and/or in series to each other. A discrete element constituting a capacitance or part of the partial circuit may be a capacitor. A discrete element constituting an inductance may be a coil of an electric line. However, the total inductance and the total capacitance of each of the phase lines and of each section of the phase lines usually comprise additional contributions of the arrangement. For example, a coil of an electric line also has a capacitance and each line section connecting discrete elements and sections to each other has an inductance. Therefore, the representation shown in Fig. 1 is a simplified example only. In any case, each discrete inductive element may be a coil.

Furthermore, the structure of the receiving device 3 shown in Fig. 1 can be modified within the limits of the present invention. In particular, there can be only one phase line, two phase lines or more than three phase lines. Although not preferred, the construction of different phase lines of the same receiving device may differ. In addition or alternatively, each phase line may comprise more than three sections or only two sections.

Furthermore, there may be an electric connection point for connecting the electric connection to the load(s) at the interfaces of only some of the sections. For example in Fig. 1, there may be connection points between the first and second sections, but not between the second and third sections or vice versa. In addition or alternatively, any load which is to be supplied with electric energy by the receiving device may be connected to the receiving device via an alternating current line, i.e. the load may be an AC load. Furthermore, the same rectifier and/or the same electric connection from the receiving device may connect not only one load to the receiving device, but a plurality of loads, such as a vehicle battery including a battery charger and at least one electric network on board the vehicle with additional loads, such as a propulsion motor and/or auxiliary devices which do not produce propulsion energy. Furthermore, since Fig. 1 is a simplified and schematic illustration, additional elements and devices may be provided and used, such as a filter for reducing frequency components of the current rectified by the rectifier. Optionally, one of the switches S1, S2 in Fig. 1 omitted.

In order to illustrate the relation between the capacitances and inductances to the resonance frequency, Fig. 2 shows the receiving device 3 with a further simplified representation. There is only one capacitance C connected in series to only one inductance L in each phase line 13a, 13b, 13c. The letters representing the capacitance C and the inductance L are therefore followed by only one reference numeral indicating the order number of the phase line. Therefore, the resonance frequency fres can be calculated from the inductance Ln and from the capacitance Cn of each phase line according to the following equation, in which the letter n indicates the order number 1,2, 3 of any of the phase lines 13:

Consequently, if the resonance frequency of the first section of the first phase line 13c is calculated, which is a part of the first phase line 13c only, the resonance frequency is smaller than for the complete first phase line. The same applies to other sections of the phase lines. As a result, a second connection line in addition to the connection line 19 shown in Fig. 1 can be connected to connection points in between sections of the phase lines and the resulting resonance frequency of the resonant electric circuit which includes the section or sections of the phase lines and the connection to the load differs from the resonance frequency in case the connection line 19 and the complete phase lines are used for generating an alternating electric current and transferring the corresponding power to a load or to loads as shown in Fig.1.

Fig. 3 shows one example of a receiving device having a first electric connection 19 like the arrangement shown in Fig. 1 and having a second electric connection 29 being connected to connection points in between the first sections and the second sections of the phase lines 13a, 13b, 13c. The second electric connection 29 connects the phase lines 13 to a second rectifier 25, which may have three branches 26a, 26b, 26c in the same manner as the first rectifier5, but is preferably designed for smaller maximum load power compared to the first rectifier 5.

In the example shown, the first rectifier 5 and the second rectifier 25 are connected to the same smoothing capacitor CL and to the same load 7 via an optional controllable switch S2. While the first rectifier 5 can be decoupled from the smoothing capacitor using the first switch S1, the second rectifier 25 may be permanently connected to the smoothing capacitor CL. Since the first rectifier 5 and the second rectifier 25 are coupled to electric circuits having different resonance frequencies, a switch for decoupling the second rectifier 25 from the smoothing capacitor CL or from the load 7 is not necessary, although a controllable switch for decoupling may be provided and used.

Therefore, the generating device on the primary side of the inductive power transfer system may be operated at the resonance frequency of the first electric circuit, which comprises the complete phase lines and the first electric connection 19, in order to transfer electric energy from the receiving device 3 via the first rectifier 5 to the load 7 (or to another load). However, if the generating device is operated at a higher frequency of the primary side alternating electric current, the generated electromagnetic field also has a higher frequency of its magnetic component and the alternating electric current produced by the receiving device 3 is mainly flowing through the first sections of the phase lines 13 only and through the second electric connection 29 to the second rectifier 25, which rectifies the current and provides energy to the load 7 (or to another load). In particular if the capacitances and the inductances of all sections of the phase lines 13 are equal, no other electric circuit comprising the second and/or third sections of the phase lines 13 would have a resonance frequency being equal to the resonance frequency of the electric circuit formed by the first sections and the second electric connection 29.

Optionally, each electric line 29a, 29b, 29c of the second electric connection 29 may comprise a capacitance C1x, C2x, C3x formed by at least one discrete element, which capacitances contribute to the resonance frequency of the second electric circuit formed by the first sections of the phase lines 13 and the second electric connection 29. On the other hand, if the resonance frequency is predetermined (for example because the generating device can be operated at this resonance frequency), the value of the capacitances C1x, C2x, C3x can be calculated and correspondingly chosen according to the following equation:

in which the variable Cnx denotes the capacitance C1x, C2x or C3x, Cn1 denotes the capacitance C11, C21, C31 in the first sections of the phase lines 13 and Ln1 denotes the inductance L11, L21, L31 in the first sections of the phase lines 13.

Optionally, the capacitances C1x, C2x, C3x (or capacitances of another arrangement) may be variable and adjustable so that their valued can be varied in an existing receiving device. Consequently, the resonance frequency of the second electric circuit comprising the first sections of the phase line and the second electric connection can be adjusted. This enables the receiving device to be operated in combination with different generating devices producing alternating electromagnetic fields at different frequencies. In addition or alternatively, the second electric connection may be switched to different electric connection points within the phase lines. For example, with reference to Fig. 3, each electric line 29a, 29b, 29c of the second electric connection 29 can be disconnected by opening a switch (not shown) from the electric connection points shown in Fig. 3 and can be connected via additional switches (not shown) and via additional line sections (not shown) to connection points in between the second and third sections of the phase lines 13. The resulting electric circuit, which is used during operation for generating the alternating electric load current and for transferring the load power to the load via the second electric connection 29, would comprise the capacitances and inductances of the first and the second sections of the phase lines 13. Therefore, the resonance frequency differs from the resonance frequency of the arrangement shown in Fig. 3.

Since, as preferred, the second rectifier 25 is designed for a smaller maximum load power than the first rectifier 5, the components of the rectifier (in particular the diodes and the electric lines) can be constructed and manufactured as smaller components compared to the components of the first rectifier 5. Therefore the effort for realizing the second rectifier 25 is low.

Using only some of the sections, but not all of the sections of the phase lines 13 has the advantage that the receiving device can be operated in partial load operating mode at higher frequencies as in full load operation mode. Furthermore, resistive losses through any section of the phase line which does not carry the alternating electric current produced by the receiving device, are minimized and nearly zero. In addition, these passive sections of the receiving device act as filters minimizing the alternating electric current through the passive section. Therefore, in case of the example shown in Fig. 3, the alternating electric current to the first rectifier 5 is very small while the receiving device is operated at the resonance frequency of the electric circuit comprising only some of the sections and the second electric connection 29.

The examples of partial load operation described with reference to Fig. 3 illustrate a principle of partial load of operation in case of a plurality of phase lines being connected to a common star point at one of their ends. If only one section or only some of the sections of each phase line is/are used for producing the alternating electric current through the electric connection to the load, all sections (i.e. at least one section) of each phase line between the electric connection point (i.e. from the electric connection line) to the star point are part of the electric circuit which produces the alternating electric current for the load by magnetic induction. The reason for this principle is that these active sections require the star point connection.

Although not absolutely necessary, it is preferred that the switch S1 shown in Fig. 3 is in its open state during the second operating state in which the second rectifier 25 is used to transfer the load power from the receiving device 3 to the load 7. This reduces parasitic electromagnetic fields which may be generated by small electric currents through the passive sections of the phase lines 13 and the rectifier 5.

During partial load operation, the primary side generating device can be a smaller (and in particular portable) unit compared to full load operation.

An arrangement as for example shown in Fig. 3 which has at least two electric connections 19, 29 for transferring a load current to at least one load can optionally be operated at at least two different operating frequencies at the same time, which may correspond to two different resonance frequencies of the electric circuits of the device. For example, the electromagnetic field produced by the primary side generating device may comprise a superimposed second frequency component in addition to the smaller frequency component typically used for full load operation. In particular, such a superimposed frequency component can be used to transfer additional power from the primary side generating device to the second side receiving device and, thereby, to the load or loads. Optionally, the operation at at least two different operating frequencies can be performed permanently or temporarily.

Furthermore, not only one, but a plurality (i.e. at least two) of receiving devices according to the present invention can be used to provide electric power to a load or to a plurality of loads, for example within the same vehicle. While both or all receiving devices may comprise an electric circuit having a first resonance frequency (which may be the same resonance frequency for both or all receiving devices), at least two of the plurality of receiving devices may comprise an electric circuit having a second resonance frequency which differs from a second resonance frequency of the other of the two or more than two receiving devices according to the present invention. In particular, the second resonance frequency may be higher than the first resonance frequency for both or all receiving devices. For example, the second resonance frequency of one of the receiving devices may be 85 kFIz and the second resonance frequency of another of the receiving devices may be 150 kFIz.

Fig. 4 shows four coils CL, CM1, CM2, CR which form a sequence of coils of a single phase line 19. The phase line 19 may be one of the phase lines of the arrangement shown in Fig. 1 or 3, or a phase line of another arrangement (e.g. an arrangement having only one phase line). In case of plural phase lines, all other phase lines of the same arrangement may be constructed in the same manner as the phase line 19 shown in Fig. 4 and the different sequences of in each case four coils may be placed at shifted positions relative to each other in longitudinal direction (the horizontal direction in Fig. 4) so that the electromagnetic field produces different phases of the same alternating electric current during operation.

All coils of the sequence shown in Fig. 4 may be formed by a spirally wound phase line, so that the arrangement is particularly flat in the direction perpendicular to the image plane of Fig. 4. Flowever, other configurations of coils are also possible.

The phase line 19 has two terminal connection points 20a, 20b for connecting the phase line to external devices such as a rectifier and/or the on-board electric network of the vehicle shown in Fig. 6 and Fig. 7, or to a star point of different phase lines connected to each other in case of terminal connection point 20a. Following the extension of the phase line 19 starting from terminal connection point 20a, the phase line 19 performs three turns 31 a, 31 b, 31 c to form the spiral first end coil CL. The inner turn 31 c is connected to a first connection line 32 for connecting the first end coil CL with the first middle coil CM1.

Following the further extension of the phase line 19, the first connection line 32 is connected to the inner turn 33f of the first middle coil CM1, which has also several turns 33a - 33f forming a spiral coil, but the number of turns of the first middle coil CM1 is six in this specific example. The outer turn 33a of the first middle coil CM1 is connected via a second connection line 34 to the outer turn 35a of the second middle coil CM2. The second middle coil CM2 is configured in the same manner as the first middle coil CM1, i.e. it has also six turns 35a - 35f.

The inner turn 35 of the second middle coil CM2 is connected via a third connection 36 to the inner turn 37c of the second end coil CR, which has three turns 37a, 37b, 37c and is configured in the same manner as the first end coil CL. The outer turn 37a of the second end coil CR is connected with the second terminal connection point 20b of the phase line 19.

An additional connection point 20c is connected to the first connection lines 32. Furthermore, an additional connection point 20d is connected to the second connection line 34. Therefore, a second electric connection (not shown in Fig. 4) can be connected to the connection point 20c. In this case, the first end coil CL may be the only active coil during operation, i.e. may be the only coil of the phase line receiving energy and delivering energy to the load(s). Alternatively, the second electric connection or a third electric connection (not shown in Fig. 4) can be connected to the connection point 20d. In this case, the first end coil and the first middle coil CM1 may be the only active coils of the phase line during operation.

Fig. 4 does not show additional discrete capacitive elements, such as capacitors or arrangement of capacitors, which are preferably connected to each of the four coils. For example, there may be at least one discrete capacitor element within each of the three connection lines 32, 34, 36 and between the first end coil CL and the first terminal connection point 20a.

Claims

1. A receiving device (3) for receiving an electromagnetic field and for producing an alternating electric current by magnetic induction, in particular for generating electric energy for operating a vehicle, the receiving device (3) comprising: • at least one electric phase line (13) for carrying a phase of the alternating electric current, wherein sections of the electric phase line (13) form inductances that produce an alternating electric voltage by magnetic induction during operation of the receiving device (3), • a first electric connection (19) being connected or connectable to at least one first connection point of the at least one electric phase line (13) for connecting the at least one electric phase line (13) to a first electric load (7), wherein the first electric connection (19) and the section or sections of the at least one electric phase line (13) which can be connected via the first electric connection (19) to the first electric load (7) form a first electric circuit having a first resonance frequency defined by the inductance or inductances of the section or sections and by at least one capacitance of the at least one electric phase line (13) and/or the first electric connection (19), • a second electric connection (29) being connected or connectable to at least one second connection point of the at least one electric phase line (13) for connecting the at least one electric phase line (13) to the first electric load (7) and/or to a second electric load, wherein the second electric connection (29) and the section or sections of the at least one electric phase line (13) which can be connected via the second electric connection (29) to the first electric load (7) and/or to the second electric load form a second electric circuit having a second resonance frequency defined by the inductance or inductances of the section or sections and by at least one capacitance of the at least one electric phase line (13) and/or the second electric connection (29), wherein the first electric circuit and the second electric circuit comprise different sets of in each case at least one section of the at least one electric phase line (13), so that a first total inductance of the first electric circuit differs from a second total inductance of the second electric circuit and, thereby, the first resonance frequency differs from the second resonance frequency.

2. The receiving device of claim 1, wherein the second electric connection (29) comprises at least one capacitance being part of the second electric circuit, the capacitance determining the second resonance frequency together with the section or sections of the at least one electric phase line (13) in the second electric circuit.

3. The receiving device of claim 1 or 2, wherein the section or sections of the at least one electric phase line (13) which are part of the first electric circuit has/have a larger impedance than the section, or sections of the electric phase line (13) which are part of the at least one second electric circuit and wherein the first resonance frequency is smaller than the second resonance frequency.

4. The receiving device of one of claims 1 to 3, wherein the inductance of each of the sections of the electric phase line (13) or of each of the electric phase lines (13) is formed by a coil of an electric line.

5. The receiving device of one of claims 1 to 4, wherein the first electric connection (19) is connected to a first rectifier for rectifying the alternating electric current and providing a direct current to the first electric load (7).

6. The receiving device of claim 5, wherein the second electric connection (29) is connected to a second rectifier for rectifying the alternating electric current and for providing a direct current to the first electric load (7) and/or to the second electric load.

7. The receiving device of claim 6, wherein the first resonance frequency is smaller than the second resonance frequency, and wherein the first rectifier is designed for a larger maximum power provided by the receiving device (3) during operation than the second rectifier.

8. The receiving device of one of claims 1 to 7, wherein the second electric connection (29) can be switched alternatively to be connected to the at least one second connection point of the at least one electric phase line (13) or to be connected to at least one third connection point of the at least one electric phase line (13), so that the second connection forms the second electric circuit, if it is connected to the at least one second connection point of the at least one electric phase line (13), or forms a third electric circuit, if it is connected to the at least one third connection point, wherein the third electric connection is adapted to connect the at least one electric phase line (13) to the first electric load (7) and/or to the second electric load and/or to a third electric load, wherein the second electric connection (29) and the section or sections of the at least one electric phase line (13) which can be connected via the at least one third electric connection point and via the second electric connection (29) to the first electric load (7), to the second electric load, and/or to the third electric load form a third electric circuit having a third resonance frequency being different from the first resonance frequency and from the second resonance frequency.

9. A method of operating a receiving device (3) for receiving an electromagnetic field and for producing an alternating electric current by magnetic induction, in particular for generating electric energy for operating a vehicle, and the method comprising: • producing an alternating electric voltage by magnetic induction and, thereby, producing the alternating electric current through at least one electric phase line (13) of the receiving device (3), wherein sections of the electric phase line (13) form inductances that produce the alternating electric voltage, • in a first operating state, using a first electric connection (19) to at least one first connection point of the at least one electric phase line (13) for providing energy from the at least one electric phase line (13) to a first electric load (7) while the first electric connection (19) is connected to the at least one first electric connection (19) point of the at least one electric phase line (13), wherein the first electric connection (19) and the section or sections of the at least one electric phase line (13) which are connected via the first electric connection (19) to the first electric load (7) form a first electric circuit having a first resonance frequency defined by the inductance or inductances of the section or sections and by at least one capacitance of the at least one electric phase line (13) and/or of the first electric connection (19), • in a second operating state, using a second electric connection (29) to at least one second connection point of the at least one electric phase line (13) for providing energy from the at least one electric phase line (13) to the first electric load (7) and/or to a second electric load while the second electric connection (29) is connected to the at least one second electric connection (29) point of the at least one electric phase line (13), wherein the second electric connection (29) and the section or sections of the at least one electric phase line (13) which are connected via the second electric connection (29) to the first electric load (7) and/or to the second electric load form a second electric circuit having a second resonance frequency defined by the inductance or inductances of the section or sections and by at least one capacitance of the at least one electric phase line (13) and/or of the second electric connection (29), wherein the first electric circuit and the second electric circuit comprise different sets of in each case at least one section of the at least one electric phase line (13), so that a first total inductance of the first electric circuit differs from a second total inductance of the second electric circuit and, thereby, the first resonance frequency differs from the second resonance frequency.

10. The method of claim 9, wherein the second electric connection (29) comprises at least one capacitance being part of the second electric circuit, the capacitance determining the second resonance frequency together with the section or sections of the at least one electric phase line (13) in the second electric circuit.

11. The method of claim 9 or 10, wherein the section or sections of the at least one electric phase line (13) which are part of the first electric circuit has/have a larger impedance than the section or sections of the at least one electric phase line (13) which are part of the second electric circuit and wherein the first resonance frequency is smaller than the second resonance frequency.

12. The method of one of claims 9 to 11, wherein the inductance of each of the sections of the electric phase line (13) or of each of the electric phase lines (13) is formed by a coil of an electric line.

13. The method of one of claims 9 to 12, wherein the first electric connection (19) is connected in the first operating state to a first rectifier which rectifies the alternating electric current and provides a direct current to the first electric load (7).

14. The method of claim 13, wherein the second electric connection (29) is connected in the second operating state to a second rectifier which rectifies the alternating electric current and provides a direct current to the first electric load (7) and/or to the second electric load.

15. The method of claim 14, wherein the first resonance frequency is smaller than the second resonance frequency, and wherein the receiving device (3) provides power to the first electric load (7) up to a larger maximum power in the first operating state than the second rectifier to the first electric load (7) and/or second electric load in the second operating state.

16. The method of one of claims 9 to 15, wherein the second electric connection (29) is switched for operation in a third operating state to at least one third connection point of the at least one electric phase line (13), so that the second connection forms in the third operating state a third electric circuit together with section or sections of the at least one electric phase line (13) which are connected via the at least one third electric connection point and via the second electric connection (29) to the first electric load (7), to the second electric load, and/or to a third electric load, and wherein the third electric circuit has a third resonance frequency being different from the first resonance frequency and the second resonance frequency.

17. The method of one of claims 9 to 16, wherein the first operating state and the second operating state are performed simultaneously by providing energy from the at least one electric phase line (13) via the first electric connection (19) to the first electric load (7) while the first electric connection (19) is connected to the at least one first electric connection (19) point of the at least one electric phase line (13) and by providing energy from the at least one electric phase line (13) via the second electric connection (29) to the first electric load (7) and/or to the second electric load while the second electric connection (29) is connected to the at least one second electric connection (29) point of the at least one electric phase line (13).

18. The method of one of claims 9 to 17, wherein, in the second operating state, the section or sections of the second electric circuit receive the electromagnetic field at a field intensity above a predetermined threshold value and a remaining section or remaining sections of the at least one phase line (13), which does/do not belong to the second electric circuit, receives the electromagnetic field at a field intensity below the predetermined threshold value.

19. A method of manufacturing a receiving device (3) for receiving an electromagnetic field and for producing an alternating electric current by magnetic induction, in particular the receiving device (3) of one of claims 1 to 7, wherein: • providing at least one electric phase line (13) for carrying a phase of the alternating electric current, wherein sections of the electric phase line (13) form inductances that produce an alternating electric voltage by magnetic induction during operation of the receiving device (3), • connecting a first electric connection (19) for connecting the at least one electric phase line (13) to a first electric load (7) permanently or via at least one switch to at least one first connection point of the at least one electric phase line (13), wherein the first electric connection (19) and the section or sections of the at least one electric phase line (13) which can be connected via the first electric connection (19) to the first electric load (7) form a first electric circuit having a first resonance frequency defined by the inductance or inductances of the section or sections and by at least one capacitance of the at least one electric phase line (13) and/or the first electric connection (19), • connecting a second electric connection (29) for connecting the at least one electric phase line (13) to the first electric load (7) and/or to a second electric load permanently or via at least one switch to at least one second connection point of the at least one electric phase line (13), wherein the second electric connection (29) and the section or sections of the at least one electric phase line (13) which can be connected via the second electric connection (29) to the first electric load (7) and/or to the second electric load form a second electric circuit having a second resonance frequency defined by the inductance or inductances of the section or sections and by at least one capacitance of the at least one electric phase line (13) and/or the second electric connection (29), wherein the first electric circuit and the second electric circuit comprise different sets of in each case at least one section of the at least one electric phase line (13), so that a first total inductance of the first electric circuit differs from a second total inductance of the second electric circuit and, thereby, the first resonance frequency differs from the second resonance frequency.