NL2019705B1

NL2019705B1 - Compensating apparatus for reducing leakage current

Info

Publication number: NL2019705B1
Application number: NL2019705A
Authority: NL
Inventors: Van Bommel Johan
Original assignee: Van Bommel Johan
Priority date: 2017-10-11
Filing date: 2017-10-11
Publication date: 2019-04-19
Also published as: EP3695497A1; WO2019074362A1

Abstract

A device for compensating a leakage current comprises a common mode coil comprising a first plurality of windings (1) and a first common mode transformer comprising a second plurality of windings (2) and a further winding (5). The device further comprises a plurality of capacitors. A first end (4) of each of the second plurality of windings (2) is connected to a first end (3) of a respective winding of the first plurality of windings (1). The first end (4) of each of the second plurality of windings (2) is connected through a respective capacitor of the plurality of capacitors to a first end (6) of the further winding (5) of the first common mode transformer.

Description

Compensating apparatus for reducing leakage current FIELD OF THE INVENTION

The invention relates to a device and a method for reducing effect of leakage current. In particular, the invention relates to leakage current occurring in the process of power supply or power consumption.

BACKGROUND OF THE INVENTION A leakage current reducing apparatus known from US 2013/0147419 A1 can be provided between a first electric apparatus and a second electric apparatus, via a plurality of connection lines connected between the first and the second electric apparatuses, and reduces leakage current flowing from the first electric apparatus to the connection lines. In addition, the leakage current reducing apparatus includes: a voltage detection section which detects, as detected voltage, the leakage current flowing from the first electric apparatus to the connection lines; a filter apparatus which receives the detected voltage; a voltage amplifier which amplifies the output ofthe filter apparatus and outputs the amplified voltage as output voltage; and a current supply section which is provided, on the second electric apparatus side with respect to the voltage detection section, between the first and the second electric apparatuses, and supplies current having substantially the same phase as the phase ofthe leakage current, to the connection lines. Further, the current supply section has a plurality of injection capacitors whose terminals on one side are connected to the connection lines and whose terminals on the other side are commonly connected to a common connection point, and applies the output voltage to the common connection point, thereby supplying the current having substantially the same phase as the phase of the leakage current from the injection capacitors to the connection lines.

The prior art current reducing apparatus needs an amplifier and thereby consumes power. Moreover, it is desirable to further reduce leakage current and reduce AC (alternating current) leakage currents having a high frequency.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an improved apparatus for reducing leakage current. To that end, a device for compensating a leakage current is provided. The device comprises a common mode coil comprising a first plurality of windings; a first common mode transformer comprising a second plurality of windings and a further winding; and a plurality of capacitors, wherein a first end of each of the second plurality of windings is connected to a first end of a respective winding of the first plurality of windings, and wherein the first end of each of the second plurality of windings is connected through a respective capacitor of the plurality of capacitors to a first end of the further winding of the first common mode transformer.

The common mode coil may provide a high impedance, whereas the transformer provides a low impedance. The further winding of the first common mode transformer may detect leaking current by connecting it to e.g. a ground terminal of an electric apparatus that is connected to the second ends of the second plurality of windings. This current detected at the second end of the further winding passes through the further winding, through the capacitors connected to the first end of the further winding, inverting the phase of the current, and is provided to the first ends of the windings. Since the first common mode transformer is configured as a low-impedance transformer, the current provided through the capacitors flows through the first common mode transformer, effectively compensating the leaking current in the common mode coil. Since the common mode coil has a relatively large impedance, the current flowing through the capacitors may not substantally pass through the common mode coil. This effect may be further enhanced by providing a series of common mode coils, so that the common mode coil is a first one of a series of at least one common mode coil connected in series, the series also comprising a last common mode coil.

The device may further comprise a second common mode transformer comprising a third plurality of windings and a further winding, wherein the common mode coil may be a first common mode coil of a series of at least one common mode coil connected in series, the series also comprising a last common mode coil; wherein a first end of each of the third plurality of windings is connected to a second end of a respective winding of the last common mode coil, and wherein the first end of each of the third plurality of windings is connected through a respective capacitor of the plurality of capacitors to a first end of the further winding of the second common mode transformer.

This way, current leakage may be reduced in both directions. Current leaking occurring in or caused by a device connected to the second ends of the second plurality of windings may be detected and compensated through the further winding of the first common mode transformer. Herein, either device may be the mains (electricity grid) or an electricity consumer, such as a machine. Current leaking in or caused by a device connected to the second ends of the third plurality of windings may be detected and compensated through the further winding of the second common mode transformer. By reducing leaking currents in both directions, an improved reduction of leaking currents may be achieved in this way. The (series of at least one) common mode coil improves the functioning of the transformers, and a separate detection and/or reduction of leaking currents occurring in a first device connected to the second ends of the second plurality of windings and in a second device connected to the second ends of the third plurality of windings may be achieved. This separation also allows to find the source of the common mode leaking current.

The device may further comprise a plurality of third common mode transformers, wherein each common mode coil of the third common mode transformers comprises a first winding, a second winding, and a third winding, a winding direction of the third winding being opposite to a winding direction of the first winding and of the second winding, the winding direction of the first winding and the second winding being the same; a second end of the first winding being connected to a second end of the second winding and to a second end of the third winding, and wherein a second end of each of the second plurality of windings is connected to a first end of the first winding of a different one of the plurality of third common mode transformers, and a second end of the further winding is connected to a first end of the third winding of each of the third common mode transformers.

This addition improves the flow of the current through the compensating current provided back to the device. In this case, the second end of the further winding needs not be connected to ground. This prevents mixing of leakage currents of the two devices that may be connected to each other through the device for compensating leakage current. A low impedance is achieved by connecting the second end of the further winding to all phases and/or the neutral phase.

Respective ones of the windings may be configured to be connected to respective terminals of a source of electricity and a load, and the source of electricity may comprise at least one of two-phase electricity, three-phase electricity, and three-phase-and-neutral electricity. This way, the device may be made suitable for different types of electricty, by connecting a number of windings to a corresponding number of terminals of the electricity. By serially connecting the device in between the source of electricity and the load, leakage currents of the two may be separated and leakage currents of at least one of the source of electricity and the load may be reduced or compensated. A first end of each second winding of the third common mode transformers may be configured to be connected to a source of alternating electricity or a load. This way the leakage current in the source of alternating electricity is effectively fed back into the source of alternating electricity or the load.

The common mode coil may be a first one of a series of at least one common mode coil connected in series, the series also comprising a last common mode coil, wherein an end of each of the plurality of windings of the last common mode coil of the series may be configured to be connected to a source of alternating electricity or to a load. This allows to isolate the source of alternating electricity or the load, allowing to feed back leakage current from the filter device to another connected device. A second end of each of the second plurality of windings may be configured to be connected to a source of alternating electricity or a load, wherein a second end of the further winding may be configured to be connected to a ground or to a neutral line of an electircity system of the source of electricity or the load. This way leakage current in the source of alternating electricity or the load is compensated.

In any embodiment, the ground may be implemented by means of a separate earthing pin. This may reduce undesired connection between grounds of devices. By connecting the further winding alternatively to a neutral line of the electricity grid or load, at least part of the leakage current may be guided into the electricity grid or load. A second end of each of the third plurality of windings may be configured to be connected to a source of alternating electricity or a load, and a second end of the further winding of the second common mode transformer may be configured to be connected to a ground or to a neutral line of an electricity system of that source of electricity or load. This allows to reduce or compensate leakage current also from a device connected to the third plurality of windings.

In any case, the ground may be implemented by means of a separate connection between the second end of the further winding with ground in a distribution center (node) of the power grid. This avoids a shortcut of the ground to the connected device.

According to another aspect of the invention, a method of compensating for leaking current is provided. The method comprises electrically connecting a device according to any preceding claim in between a source of electricity and a load that consumes the electricity.

The person skilled in the art will understand that the features described above may be combined in any way deemed useful. Moreover, modifications and variations described in respect of the device may likewise be applied to the method, and modifications and variations described in respect of the method may likewise be applied to the device.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, aspects of the invention will be elucidated by means of examples, with reference to the drawings. The drawings are diagrammatic and may not be drawn to scale. Throughout the drawings, similar items may be indicated with the same reference numerals.

Fig. 1 shows a first example of a device for reducing leakage current.

Fig. 2 shows another illustration of the device for reducing leakage current.

Fig. 3 shows a device for reducing leakage current of two electrically connected devices.

Fig. 4 shows another example of a device for reducing leakage current.

DETAILED DESCRIPTION OF EMBODIMENTS

Certain exemplary embodiments will be described in greater detail, with reference to the accompanying drawings.

The matters disclosed in the description, such as detailed construction and elements, are provided to assist in a comprehensive understanding of the exemplary embodiments. Accordingly, it is apparent that the exemplary embodiments can be carried out without those specifically defined matters, also, well-known operations or staictures are not described in detail, since they would obscure the description with unnecessary detail. Throughout this disclosure, a connection refers to an electric connection, unless noted otherwise.

Leaking current may be caused by a capacitance between an apparatus and Earth, for example, even if the apparatus is electrically shielded. The common mode transformer, formed by the common mode coil with the further winding, as described in detail elsewhere in this disclosure, receives these leakage currents through the further winding, inverts the received leakage current, for example by means of a capacitance, and feeds back the inverted leakage current. This may be in accordance, for example, with a formula Zc =1 / ( 2 * π * f * C ), wherein Zc denotes the impedance of a capacitor, f denotes the frequency of a source of alternating electricity or any frequency found in the frequency spectrum of the leakage current, and C denotes the value of a capacitor.

Fig. 1 shows a diagram of a filter. Fig. 2 shows another diagram of the filter, showing the structure of the coils in greater detail. In Fig. 1, Ilek denotes a leaking current. An electric apparatus (not illustrated) connected to the terminals LI ’, L2’, L3’, and N’ may leak a portion of the current circulating within or through it to ground. The common mode transformer 51 comprises a conductive ring-shaped core with a plurality of windings arranged around the core. Separate windings 2 are provided for each terminal LI’, L2’, L3’, and N’, and a further winding 5 has its second end 9 connected to a ground. This ground may be a ground terminal of the connected electric apparatus, or a general ground connection.

The number of turns around the core that a winding makes, may be substantially the same for all the phases of a coil. The further winding may have the same number of turns as the windings of the phases, however the further winding may also have a different number of windings. When the number of turns is the same, the common mode current is inverted and fed back. If the number of turns is different, a remaining current may exist. If the total current through a cable is small (close to zero), the impedance of that cable may become low, so that the high frequency leak currents may flow through that cable rather than another, higher-impedance cable.

The load leaks some of the current supplied to it via L1 ’, L2’, L3’, and N’ to ground. This leaking current has a certain frequency. The higher harmonics of this leaking current may be difficult to remove using existing filters. The filter disclosed hereing is better capable of filtering higher harmonics of leakage current.

In electric installations, current may leak to ground undesirably through for example data cables. High frequency alternating currents may leak to ground via unintended capacitance.

The filter allows to meet certain EMC (electromagnetic compatibility) norms regarding leaking currents. The filter can, for example, achieve 20-40 dB (a factor of 10 to 100) of additional reduction compared to an all-pole-sinus filter, in a test environment.

The power supply may be a 3-phase electric power supply (also known as strong power / energy power). This power supply may or may not have an additional neutral terminal, as well as a separate ground terminal. Corresponding terminals and windings may be provided in the filter. The power supply may have any number of phases, including simple single-phase electric power supply. Alternatively, a two-phase electric power supply may be used.

The filter has a high-impedance portion and a low-impedance portion. Common mode coil 1 typically has a high impedance, whereas common mode transformer 2 typically has a low impedance.

Examples of sources of leaking currents include frequency regulators, converters for solar panels, and power supplies based on pulse width modulation and devices connected thereto. The filter proposed in this disclosure may be used to reduce the effect of such leaking currents.

In Fig. 1 and Fig. 2, when comparing the coil 51 on the left-hand side with the coil 52 on the right hand side, the coil on the right-hand side 52 has a further winding 5 connected to ground. This way, leaking high-frequency currents are drawn from ground into the filter. They are coupled by the capacitor and these high-frequency currents flow back into the load (indicated in Fig. 1 by Ilek). A filter for removing leaking current may comprise a common mode coil having windings corresponding to one or more phases of a source of electricity, a common mode transformer having windings corresponding to these phases of the source of electricity and a further winding connected to ground. The windings of the common mode coil may be connected to corresponding windings of the common mode transformer. Additionally, these windings of the common mode coil may be connected via respective capacitors to the further winding of the common mode transformer. On the other side of the common mode coil, the windings can be connected to a source of electric power (or, in another example, to a load). On the other side of the common mode transformer, the windings can be connected to a load (or, in the other example, to the source of electric power). The further winding of the common source transformer is connected to a ground. In another embodiment, the filter is electrically connected in between two different apparatuses (neither side of the filter being directly connected to a source of electricity)

The common mode coil can also comprise a winding connected to the neutral wire of the source of electricity, wherein the common mode transformer also comprises a corresponding winding, and this winding may be connected via a respective capacitor to the further wire of the common mode transformer.

The position of the load and the mains (=power source) with respect to the filter may be reversed. The mains may be connected to the common mode coil, i.e. LI, L2, L3, N, and the load may be connected to the common mode transformer, i.e., LI’, L2’, L3’, and N’. However, alternatively the load may be connected to the common mode coil, i.e., LI, L2, L3, N, and the mains may be connected to the common mode transformer, i.e. LI’, L2’, L3’, and N’. In that case, high frequency current leakage by the mains net may be removed.

In the following, detailed examples of the filter and its variants and extensions will be described in greater detail. These details, however, are not intended to be regarded to limit the invention. Rather, the detailed description may aid in an improved understanding of the invention.

Fig. 1 shows an example implementation of the filter. The filter comprises a common mode coil 51 and a first common mode transformer 52. A common mode transformer may be regarded as a common mode coil that has a function of a transformer. As shown in Fig. 2, a common mode coil or transformer may comprise an annular core and a number of windings around the annular coil. Each winding may comprise a wire having a first end and a second end, with, a number of turns around the core in between the first end and the second end. Windings may be wound around the core in different directions, including left-winding and right-winding. In the example shown in Fig. 2, all the windings have the same direction. Fig. 1 shows an implementation intended for 3-phase electricity having 3 phases and a neutral phase.

The number of windings of the common mode coil 51 corresponds to the number of phases of the electricity system used. The number of windings of the common mode transformer 52 corresponds to the number of phases of the electricity system plus a further winding. That is, for a single-phase electricity system with a neutral phase, the number of the first plurality of windings 1 may be two, and the number of the second plurality of windings 2 may also be two. For a three-phase electricity system, the number of the first plurality of windings 1 may be three, and the number of the second plurality of windings 2 may also be three. If the electricity system further includes a neutral phase, the number of the first plurality of windings 1 may be four, and the number of the second plurality of windings 2 may also be four.

The windings on a coil may have the same winding direction usually. A first end 3 of each winding 1 of the common mode coil 51 is connected to a corresponding first end 4 of a respective winding 2 of the common mode transformer 52. A first end 6 of the further winding 5 of the common mode transformer 52 is connected to each of the other windings via a respective capacitor Cl, C2, C3, C4. To that end, separate capacitors Cl, C2, C3, C4 may be provided, one for each phase of the electricity system. The second ends of the windings may be connected to external devices. The filter may thus be connected in between two devices. One device may be connected to the second ends 7 of the windings 1 of the common mode coil 51. Another device may be connected to the second ends 8 of the windings 2 of the common mode transformer 52. In some applications, one of those devices is the electricity network, and the other device is an apparatus that consumes the power of the electricity network.

Fig. 3 shows a diagram of a filter device that can compensate leakage currents of both connected devices. The filter device comprises the common mode coil 51 and the common mode transformer 52, in a similar configuration as shown in Fig. 1 and Fig. 2. However, the device shown in Fig. 3 comprises more components.

First, as shown in Fig. 3, the fdter device may comprise more than one common mode coil 51. More particularly, the filter device may comprise a plurality of common mode coils 51, 51’, 51”, connected in series. Such a sequence of common mode coils provides a relatively large impedance, so that the windings of the second and optional second common mode transformer, which have a lower impedance than the series of common mode coils, will conduct most of the leakage current supplied via the further winding. Moreover, this way internal and external leakage current may be separated. It will be understood that such a sequence of common mode coils 51, 5Γ, 51” may be added to the filter of Fig. 1, even without adding the further components of Fig. 3. The last common mode coil 51” in the series may thus be directly connected to an external device, in certain embodiments, replacing the second common mode transformer 53.

Second, the filter shown in Fig. 3 comprises an additional common mode transformer 53 connected to the last one of the common mode coils 51”. It will be understood that, although the drawing shows a sequence of three common mode coils 51, 5Γ, 51”, this number may be varied. To improve the efficiency, capacitors connected to ground or neutral may be connected to the windings in between the common mode coils. In certain implementations, the number of common mode coils may one, two, three, or more common mode coils, which may be connected in series. The windings of the first common mode coil 51 are connected to the windings of the first common mode transformer 52, and the windings of the last common mode coil 51” are connected to windings of another common mode transformer, herein referred to as second common mode transformer 53. The second common mode transformer 53 comprises a third plurality of windings 10 and a further winding 11, similar to the first common mode transformer 52. A first end 12 of each of the third plurality of windings 10 is connected to a second end 14 of a respective winding 13 of the last common mode coil 51”. Moreover, the first end 12 of each of the third plurality of windings 10 is connected through a respective capacitor (Cl’, C2’, C3’, C4’) of the plurality of capacitors to a first end 15 of the further winding 11 of the second common mode transformer 53. The second end 16 of the further winding 11 of the second common mode transformer 53 may be connected or connectable, for example, to ground. The ground may be a ground terminal of the externally connected device, or a general ground of a mains or a heavy object, which may be capacitively coupled to the externally connected device. The electric phases of the externally connected device, may be connected or connectable to the second ends 17 of respective third windings 10 of the second common mode transformer 53.

If the separated common mode leakage current of the mains side is coupled to ground, the possibility is created that it might return through ground into the load. To reduce or avoid this effect, certain techniques may be applied. An extra grounding pin may be provided, which may be provided at a certain distance away from the load, for example a couple of meters or a couple of tens of meters, or a couple of hundreds of meters away from the load, to provide a large enough impedance, depending on the amount of current involved. Alternatively, the further winding may be connected to a neutral phase of electricity instead of ground. In that case, a differential mode current is coupled, so that part of the current will flow to a star node of the electricity grid, although another part of the leakage current may flow into the load depending on the impedances of the filter device and other involved impedances. Alternatively, an extra ground wire may be provided to connect the further winding to a far away ground, for example inside the closest star node (distribution node) of the electricity grid. Alternatively, the configuration of Fig. 4 may be applied to feed the leakage current directly back into the connected device or mains.

Fig. 4 illustrates another implementation of the filter. It is noted that Fig. 4, by means of illustration, shows a configuration suitable for a one-phase electricity system. However, it will be understood that this configuration, and also the other configurations disclosed herein, may be adapted to other electricity systems by adding coils and windings corresponding to the number of phases to be included in the filter.

The filter shown in Fig. 4 shows a common mode coil 51, which basically corresponds to the common mode coil 51 shown in Fig. 1 and 2, and a first common mode transformer 52, which basically corresponds to the first common mode transformer 52 of Fig. 1 and 2. Note that, by means of illustrative example, the coils 51, 52 of Fig. 4 are adapted to a single-phase electricity system with respect to the number of windings. The filter further comprises a plurality of third common mode transformers 54, 54’. These may also be referred to herein as third common mode transformers 54, 54’.

In Fig. 4, the external device or mains is not connected directly to the second ends 28 of the second plurality of windings 2. Rather, the second ends 28 of the second plurality of windings 2 are each connected to a first end (24) of a first winding 21 of a different one 54 of the plurality of third common mode transformers 54, 54’.

Each of the third common mode transformers 54, 54’ comprises a first winding 21 and a second winding 22 connected in sequence, and a third winding 23. The winding direction of the third winding 23 is opposite to a winding direction of the first winding 21 and second winding 22. The latter two have the same winding direction.

The main current passes through windings 22 and 21. The fields generated by these windings cancel each other, so that saturation of the core of the coil does not occur. The common mode current is determined by transformer 52. The connections of the windings through ends 24, 28, 29 and 30 form a shortcut loop that may allow a realtively large current to flow through it. By selecting a different number of windings for the third winding 23, a ratio defined as the current in the first winding 21 divided by the current in the third winding 23 may equal a ratio defined as the number of turns of the third winding 23 divided by the number of turns of the first winding 21. This may also determine the current through the second winding 22, because the current in the second winding 22 may equal the current in the third winding 23 minus the current in the first winding 21. Since the whole system may be regarded a closed feedback loop, the system may self regulate.

The second end 25 of the first winding 21 is connected to a second end 26 of the second winding 22. A second end 28 of each of the second plurality of windings 2 of the common mode transformer 2 is connected to a first end 24 of the first winding 21 of a third common mode transformer 54. Different windings are connected to different ones of the common mode transformers 54, 54’, one winding and common mode transformer for each phase of the electricity system. The second end 29 of the further winding 5 of the common mode transformer 52 is connected to a first end 30 of the third winding 23 of each of the third common mode transformers. That is, one further winding 5 is connected to the third winding 23 of all third common mode transformers 54, 54’.

In operation, a main current circuit is formed by the first winding 21 and the second winding 22. These two windings have the same number of turns around the core. The third winding 23 may be considered to have a control lunction, to control the current flowing through the first and second windings 21, 22. Therefore, the number of turns around the core may be different for the third winding 23 than for the first and second winding 21, 22.

The circuit of Fig. 4 may have a lower impedance of the leakage current that is fed back towards the terminals L, N. Therefore, the performance of the filter may be improved.

For example, a first end 27 of each second winding 22 of the third common mode transformers is configured to be connected to an external device, such as a source of alternating electricity or a load. Moreover, for example, a second end 7 of each of the first plurality of windings 1 (more particularly, the windings of the last one of a sequence of common mode coils) may be connected to a load.

It will be understood that the features of the configurations of Fig. 3 and Fig. 4 may also be combined. For example, to the right of the common mode coil 1 at points L’ and N’, shown in Fig. 4, there may be a sequence of common mode coils Γ. Moreover, another common mode transformer may be connected thereto. That other common mode transformer may also have corresponding third common mode transformers 54, connected in a similar way as shown in Fig. 4.

As will be clear from the above description, respective ones of the windings may be configured to be connected to respective terminals of a source of electricity and a load, and the source of electricity may comprise, for example, two-phase electricity, three-phase electricity, or three-phase-and-neutral electricity.

In all described examples, a second end 9, 16 of the further winding 5, 11 of the first or second common mode transformer may be configured to detect at least part of the leaking current of the device connected to the other windings of that coil. For example, the further winding may be connected to a ground. The ground may be any suitable ground. The ground may be, for example, a ground of a central node of a power grid. The ground may be a ground terminal of the external device. Alternatively, the further winding may be connected to neutral phase of a source of alternating electricity.

In operation, the source of electricity may be connected to one set of windings and a consumer of electricity may be connected to the other set of windings of the filter, as described above. The electricity may thus flow in either direction through the filter. The common mode transformers 52 and 53 may detect and compensate leaking currents of the devices connected thereto.

In the filter shown in Fig. 1 and 2, the second common mode transformer 53 may be omitted. Then, the filter still can detect the leaking current of the device connected to the remaining first common mode transformer 52. A device may be connected to the common mode coil 51 (or 5 Γ ’ in case of a sequence of common mode coils) instead of the second common mode transfonner 53. The leaking current detected by the further winding 5 does not flow towards that device due to the high impedance of the common mode coil(s) 51, 5 Γ, 51” compared to the low impedance of the common mode transformer 52.

In the filter, of any of Fig. 1 to 4, the common mode coil 51 helps to isolate the two connected devices from each other with respect to leaking currents, because of a high impedance. This effect is improved further when a sequence of a plurality of common mode coils 51, 51’, 51” is provided. A leakage current reduction filter may be provided, which can be connected in between the power grid and a load. The load can, for example, be an industrial machine or equipment. A suitable application of the filter is leaking current reduction in agricultural equipment such as milking and feeding robots for animals. However, the filter can be applied in any application of leakage current reduction.

The filter can remove high frequency leakage currents. Depending on the caracteristies of the used core materials in the coils, the filter may be tuned to remove lower frequency leakage currents as well. The reduction of leakage currents may be beneficial for example for well-being of animals or humans in the environment of the machine. In an animal farm it may enhance production.

The examples and embodiments described herein serve to illustrate rather than limit the invention. The person skilled in the art will be able to design alternative embodiments without departing from the spirit and scope of the present disclosure, as defined by the appended claims and their equivalents. Reference signs placed in parentheses in the claims shall not be interpreted to limit the scope of the claims. Items described as separate entities in the claims or the description may be implemented as a single hardware or software item combining the features of the items described.

Claims

An apparatus for compensating a leakage current, comprising a shared-mode coil with a first amount of windings (1); a first shared mode transformer comprising a second amount of windings (2) and a further winding (5); and an amount of capacities; wherein a first end (4) of each of the second amount of windings (2) is electrically connected to a first end (3) of a respective winding of the first amount of windings (1), and wherein the first end (4) of each of the second amount of windings (2) is electrically connected by means of a respective capacitance of the amount of capacities with a first end (6) of the further winding (5) of the first shared-mode transformer.

The apparatus of claim 1, further comprising a second shared-mode transformer comprising a third amount of windings and a further winding (11), wherein the shared-mode coil comprises a first of a series of at least one shared-mode coil electrically connected is in series, the series further comprising a final shared-mode coil; wherein a first end of each of the third amount of windings (10) is electrically connected to a second end (14) of a respective winding (13) of the last divided-mode coil, and wherein the first end (12) of each of the third amount of windings (10) is electrically connected by means of a respective capacitance of the amount of capacities with a first end (15) of the further winding (11) of the second shared-mode transformer.

The apparatus of claim 1 or 2, further comprising an amount of third shared-mode transformers, wherein each shared-mode coil of the third shared-mode transformers has a first winding (21), a second winding (22), and a third comprises a winding (23), wherein a winding direction of the third winding (23) is opposite to a winding direction of the first winding (21) and of the second winding (22), and the winding direction of the first winding (21) and the second winding winding (22) is the same; a second end (25) of the first winding (21) is electrically connected to a second end (26) of the second winding (22) and to a second end of the third winding (23), and wherein a second end (28 ) of each of the second amount of windings (2) is electrically connected to a first end (24) of the first winding (21) of a different one from the amount of third shared-mode transformers, and a second end (29) of the further winding (5) is electrically connected to a first end (30) of the third winding (23) of each of the third shared-mode transformers.

The device of any of the preceding claims, wherein respective windings of the windings are arranged to be electrically connected to respective terminals of a source of electricity and a load, and the source of electricity at least one of two-phase electricity, three -phase electricity and three-phase-with-neutral electricity, and the device is serially connected between the source of electricity and the load.

The apparatus of claim 3, wherein a first end (27) of each second winding (22) of the third shared-mode transformer is adapted to be electrically connected to at least one of a source of alternating current and a load.

The apparatus of claim 1, wherein the shared mode coil (51) is a first of a series of at least one shared mode coil that is electrically connected in series, the series further comprising a final shared mode coil of the series wherein an end (7) of each of the plurality of turns of the last shared-mode coil of the series is adapted to be electrically connected to an alternating current source or to a load.

The apparatus of claim 1 or 2, wherein a second end (8) of each of the second plurality of windings (2) is adapted to be electrically connected to a source of electricity or a load, wherein a second end (9) of the further winding (5) is arranged to be electrically connected to a ground or to a neutral line of an electricity system from the source of electricity or the load.

The apparatus of claim 2, wherein a second end (17) of each of the third plurality of windings (10) is adapted to be electrically connected to an alternating current source or a load, and a second end (16) of the further winding (11) of the second shared-mode transformer is arranged to be electrically connected to a ground or to a neutral line of an electricity system from that source of electricity or load.

The device of claim 7 or 8, wherein the ground is a ground of a distribution point of an electricity network.

A method for compensating leakage current, the method comprising electrically connecting a device according to any of the preceding claims between a source of electricity and a load that consumes the electricity.