Manufacturing an electrical power supply device for electrical coupling with a multi-phase electrical power supply network, power supply device and magnetic resonance device

Abstract

Method for manufacturing an electrical power supply device (56) for electrical coupling, in particular without reference potential or neutral conductor, to a multi-phase electrical power supply network (58), wherein the power supply device (56) has a multi-phase inductive or capacitive load unit (72) with a number of load connections (74, 76, 78) corresponding to a number of phases (L1, L2, L3) of the power supply network (58), wherein each of the load connections (74, 76, 78) is electrically coupled to a respective phase (L1, L2, L3) of the electrical power supply network (58), wherein the respective electrical phase currents of the load connections (74, 76, 78) are detected by means of at least one current sensor (100, 102, 104), the phase currents are evaluated and a differential current is determined, characterized in that the phase (L1, L2,L3) of the electrical power supply network (58) with the smallest or the largest phase current is determined and this phase (L1, L2, L3) is electrically coupled to an electrical reactance component (84) whose reactance value is determined depending on the differential current.

Description

[0001] The invention relates to a method for producing an electrical power supply device for electrical coupling, in particular a reference-potential-free or neutral-conductor-free electrical coupling, to a multi-phase electrical power supply network. The power supply device comprises a multi-phase inductive or capacitive load unit with a number of load connections corresponding to the number of phases of the power supply network. Each of the load connections is electrically coupled to a respective phase of the electrical power supply network. The respective electrical phase currents of the load connections are detected by means of at least one current sensor, the phase currents are evaluated, and a differential current is determined. The invention further relates to a method for operating a power supply device.Furthermore, the invention also relates to a power supply device for electrical connection, in particular a reference-potential-free or neutral-conductor-free connection, to a multiphase electrical power supply network, comprising a multiphase inductive or capacitive load unit having a number of load terminals corresponding to the number of phases of the power supply network, and a connection unit for electrically coupling the power supply network. The connection unit has a number of phase terminals corresponding to the number of phases of the power supply network, wherein a respective load terminal is electrically coupled to a respective phase terminal in order to carry a respective phase current. Finally, the invention also relates to a magnetic resonance apparatus having a gradient power amplifier and a power supply device.

[0002] Generic methods and energy supply devices are extensively known in the prior art, so that separate written proof is not required. Generic energy supply devices are used, for example, but not exclusively, in devices that serve the non-destructive examination of objects and that use radiation or energy fields for the examination. Such devices include, for example, magnetic resonance systems, X-ray systems, or the like, which are used for imaging examinations similar to computed tomography, in particular in medical diagnostics or the like. In such devices, the electrical energy supply is generally provided by a generic energy supply device, which for this purpose has a transformer as an inductive load unit.A rectifier unit is often connected to the transformer, which supplies the device with electrical energy.

[0003] Typically, the transformer is designed as a three-phase transformer for connection to a three-phase power supply network, such as the public power grid. The power supply network is often designed as an AC network and provides alternating voltages corresponding to the number of its phases. The alternating voltages generally have approximately the same amplitude and frequency. However, they are phase-shifted relative to each other. The phase shift usually depends on the number of phases and is approximately 120° for a three-phase power supply network.

[0004] The power supply device is often connected without a neutral conductor. The transformer can be connected to the power grid, for example, in a star or delta configuration. In addition, a corresponding multiphase, particularly three-phase, filter can be provided for reasons of electromagnetic compatibility and / or, if necessary, to comply with grid perturbations.

[0005] Neither the filter nor the transformer can achieve a completely symmetrical impedance with respect to the power grid, for example due to component tolerances, design limitations, and / or the like. Furthermore, the transformer may be dimensioned too small for cost reasons. This accepts the possibility that the electrical ratings of the transformer may be exceeded for short-term high power loads. This can lead to magnetic flux guidance within the transformer being partially impaired due to saturation phenomena in the corresponding flux guidance materials, resulting in a poorer coupling between the primary side of the transformer on the power grid side and the secondary side of the transformer on the device side, compared to lower power loads.Poor coupling can be explained, among other things, by an increase in the stray inductance of the transformer or the corresponding section of the transformer. This can cause an asymmetry with respect to the power grid-side impedance. This can manifest itself, among other things, in the form of a star point shift.

[0006] This effect can be particularly amplified with high power or phase currents at the load terminals or transformer terminals. The aforementioned effects can lead to a leakage current occurring or being increased. In addition, the filter can also cause a leakage current, especially if it contains Y capacitors. From the above, it follows that the leakage current can be power- or current-dependent.

[0007] For reasons of electrical safety, the aforementioned devices are often electrically connected to the power supply network via a residual current device. Standards stipulate that residual current devices are designed, for example, for a rated residual current of 30 mA at a frequency of 50 Hz. If a residual current or leakage current greater than the rated residual current is detected, the residual current device trips and electrically disconnects the device from the power supply network. This electrical isolation is usually achieved using electromechanical switching contacts. The aforementioned effects resulting in the leakage current can, for example, lead to the unwanted tripping of a residual current device at high power levels, thus disrupting the device's intended operation.

[0008] To mitigate the aforementioned problem, attempts have been made to implement the most symmetrical winding patterns and the smallest possible leakage capacitances for the transformer. Furthermore, attempts have been made to select a higher rated residual current of the residual current device, for example, 300 mA. However, for electrical safety reasons, the latter option is not always possible. Furthermore, the problem is particularly exacerbated in newer devices that have multiple systems with higher leakage capacitances.

[0009] DE 195 25 417 A1 discloses an arrangement for ground fault current compensation comprising a controllable compensation element with inductive reactance for generating a compensation current. DE 10 2012 103 735 A1 discloses a ground fault system comprising a ground fault coil, a control device, and a semiconductor tap changer for the ground fault coil. DE 10 2020 104 133 A1 discloses a compensation device for compensating a leakage current with a compensation current generation device and a compensation current selection device.

[0010] The invention is based on the object of reducing the aforementioned leakage current problem in the simplest possible way.

[0011] As a solution, the invention proposes methods and an energy supply device according to the independent claims.

[0012] Advantageous further training results from features of the dependent claims.

[0013] With regard to a generic method for producing an electrical power supply device, the invention proposes in particular that the phase of the electrical power supply network with the smallest or the largest phase current is determined and that this phase is electrically coupled to an electrical reactance component whose reactance value is determined as a function of the differential current.

[0014] With regard to a generic method for operating a power supply device, the invention proposes in particular that an electrical power of the transformer is determined during normal operation and the electrical reactance component is activated depending on the determined electrical power.

[0015] With regard to a generic power supply device, the invention proposes in particular that the device has at least one electrical reactance component which is electrically coupled to one of the transformer terminals, wherein the reactance component is electrically coupled to that one of the transformer terminals at which the smallest or the largest phase current occurs during normal operation.

[0016] With regard to a magnetic resonance apparatus, the invention proposes in particular that the energy supply device is designed according to the invention.

[0017] The power supply device serves, among other things, to supply electrical devices with electrical energy. For this purpose, the power supply device can draw electrical energy from an electrical power supply network such as the public electrical power grid; in particular, the power supply device can be connected to the electrical power supply network. The power supply device provides the electrical energy for the electrical device. The electrical device can be a magnetic resonance system or a magnetic resonance examination arrangement, in particular a magnetic resonance device, an X-ray system, or the like. The power supply device is electrically coupled to the electrical device, in particular connected to it.

[0018] The invention is based, among other things, on the idea that the leakage current problem described above can be reduced by using the reactance component to at least partially compensate for the aforementioned star point shift, especially at high power levels. This makes it possible to significantly reduce the leakage current, especially at high electrical power levels.

[0019] This avoids the need for a complex and expensive special design of the load unit, especially the transformer. It also prevents the deterioration of the protective functionality of a residual current device due to an increased rated residual current. In this context, reference is also made to the relevant standards, such as IEC 60364 (VDE 0100), IEC 60479 (VDE V 0140 / 479), IEC 61008 (VDE 0664 / 10), IEC 61009 (VDE 0664 / 20), IEC 60947 / 4 (VDE 0660 / 101), and / or similar. These standards relate, among other things, to the protection of persons against electric shock, particularly in low-voltage systems.

[0020] The power supply network is preferably a low-voltage power supply network based on Directive 2014 / 35 / EU of the European Parliament and of the Council of February 26, 2014, on the harmonisation of the laws of the Member States relating to the making available on the market of electrical equipment designed for use within certain voltage limits. The Low Voltage Directive serves the purpose of ensuring a high level of protection of electrical equipment with regard to the health and safety of people, domestic animals, and property, while simultaneously safeguarding the functioning of the European internal market. The power supply device is preferably designed to be supplied with a multi-phase low voltage.

[0021] The reactance component can have at least one electrical capacitance, for example in the form of an electrical capacitor, or at least one electrical inductance, for example in the form of an electrical coil, combination circuits thereof, and / or the like. The reactance value of the reactance component can be determined, for example, by means of simulation, empirically, for example by conducting series of measurements or the like. For this purpose, it can be provided, for example, that the reactance value is increased gradually and its effect on the differential current is determined.If, for a specific choice of reactance value, the differential current is smaller than a specified reference value, the resulting dimensioning of the reactance value can be implemented in the reactance component, and the reactance component can be connected and / or installed in the power supply device at the specified position. However, it can also be provided that the reactance value is increased until a minimum differential current is determined. In this case, the reactance value determined in this way can then be determined accordingly. This procedure can take into account that by selecting the appropriate reactance value, only a minimum differential current can be achieved, and that if the reactance value is increased further, the differential current will increase again, for example due to overcompensation or the like.

[0022] Reference potential-free means that in particular no neutral conductor or earth conductor of the power supply network, if present, needs to be electrically connected to the power supply line. It is therefore preferably provided that only the phases of the multi-phase power supply network are coupled to the corresponding load connections or transformer connections. Preferably, the power supply network is a public power supply network, which is preferably three-phase and provides an effective voltage of approximately 400 V at approximately 50 Hz between the phases. In principle, however, the invention is not limited to such an alternating current network or power supply network and can also be used in power supply networks that provide a different effective voltage or a different network frequency.Furthermore, the invention can of course also be used in energy supply networks that have more than three phases, for example four phases, five phases, six phases or the like.

[0023] Terms such as apparent power, active power, reactive power, effective resistance, impedance, reactance, and the like are familiar to those skilled in the art, so further explanations will be omitted. In this regard, reference is made only to the textbook "The Complex Calculation of Alternating Current Circuits" by Prof. Dr. Hans Heinrich Meinke, published by Walter de Gruyter & Co., Berlin, 1965, 3rd edition, Volume 1156 / 1156a.

[0024] The load unit, in particular the transformer, is designed as a multi-phase load unit adapted to the power grid. Depending on the number of phases of the power grid, the load unit has a corresponding number of load terminals, to each of which at least one terminal of the load unit is connected. When a transformer is used as the load unit, the corresponding transformer terminals of a respective phase winding are electrically coupled to the phases of the power grid.

[0025] The transformer can have any type of connection, for example, a star connection, a delta connection, a zigzag connection, or the like. The connection types for transformers are also known to those skilled in the art, which is why explanations regarding the connection types of transformers will be omitted here. In principle, this also applies generally to the load unit.

[0026] It is also irrelevant for the invention whether the transformer continues to provide galvanic isolation between a primary side that can be electrically coupled to the power supply network and a secondary side that is or can be electrically connected to device-side devices.

[0027] Coupling the power supply device to the power grid may require the transformer to be coupled to the phases of the power grid via an appropriate filter. The filter may serve, among other things, to meet electromagnetic compatibility requirements, in particular to reduce the emission of conducted electrical interference. In this regard, reference is made, among other things, to Directive 2014 / 30 / EU of the European Parliament and of the Council of February 26, 2014, on the harmonisation of the laws of the Member States relating to electromagnetic compatibility. This directive deals with the electromagnetic compatibility of equipment. Y-capacitors are generally provided in generic filters, particularly to reduce conducted common-mode interference. As already explained, the use of such Y-capacitors can contribute to the leakage current.This is also taken into account by the invention.

[0028] The power supply device according to the invention is preferably manufactured according to the method according to the invention for manufacturing the power supply device. The power supply device according to the invention therefore has an electrically determined reactance component that is electrically coupled to the load terminal at which the smallest or largest phase current occurs during normal operation. This makes it possible to reduce, if not completely eliminate, the problem of leakage current during normal operation by means of the power supply device according to the invention.

[0029] The power supply device preferably has an electrical contact device that is connected to all load terminals and that has contact points electrically connected to the respective load terminals for, preferably, detachably electrically contacting the reactance component. This makes it possible to electrically connect the power supply device to the reactance component as needed during the manufacturing process or an initialization procedure. The reactance component can thus be electrically connected to the respective load terminal depending on the smallest or largest phase current determined during intended operation. This can be achieved, for example, by suitably inserting the reactance component into the corresponding contact point. The contact point can, for example, provide a detachable electrical plug connection.However, it can also be provided that the reactance component has a connection contact that can be connected to the contact point, for example by soldering, clamping, and / or the like. Of course, additional mechanical parts can also be provided with which the reactance component can be fixed so that reliable contact can be made with the respective contact point. The detachability of the electrical connection means that reinitialization can be carried out at a later time. This makes it possible to adapt to changes that occur during normal operation by adjusting the reactance component, for example with regard to the reactance value or with regard to the coupling of the respective load connection.

[0030] In this context, the term "production" not only encompasses initial or one-time production, but can also include a re-initialization. Initialization can be repeated at specified times.

[0031] The invention is particularly suitable for retrofitting existing energy supply systems.

[0032] If the reactance component is formed by an electrical capacitor, the capacitor preferably has an electrical capacitance in a range from approximately 1 nF to, for example, approximately 250 nF, preferably in a range from approximately 10 nF to 150 nF, particularly preferably in a range from approximately 50 nF to approximately 150 nF, particularly preferably in the range of approximately 100 nF. The electrical capacitance of the capacitor can preferably be selected in a range of a capacitance of a capacitive coupling of the load unit.

[0033] The magnetic resonance apparatus preferably comprises at least one patient receiving area, a main magnet, a gradient coil unit, a radio frequency antenna unit, a control unit and a power supply device.

[0034] Furthermore, it is proposed that the electrical contact device has two electrical contact points for each of the load connections, wherein the electrical contact device is electrically coupled in series with the load connections. The respective load connections are thus electrically coupled via the contact device to the respective phase connections of the connection unit. For example, a respective contact pair provides an electrical interruption between the respective load connection and the respective phase connection. The reactance component, which has at least two electrical connection contacts, can provide the electrical connection when connected. An electrical bridge, for example a wire connection, can be fitted to the further contact pairs.In the phase in which the smallest or largest phase current occurs during intended operation, the reactance component is therefore connected to the two respective electrical contact points. The other pairs of contact points are each connected to one another via an electrically conductive connection. In this way, the reactance component can also be connected in series in the respective phase in which the smallest phase current occurs. This enables a simple structural implementation of the invention. In this way, the reactance component is only connected in the phase in which the smallest or largest phase current occurs. The other phases are essentially directly electrically coupled to the respective load terminals by the electrical contact device.

[0035] Alternatively or additionally, it can be provided that the electrical contact device has precisely one electrical contact point for each of the phase connections, wherein the electrical contact device has at least one further contact point, which is electrically coupled, for example, to an electrical ground potential. In this way, the reactance component establishes a connection between the phase in which the smallest or largest phase current occurs during intended operation and the electrical ground potential. This embodiment also makes it possible to achieve a corresponding improvement with regard to the leakage current. Furthermore, no additional electrically conductive bridges need to be provided with this development.

[0036] According to a further development, it is proposed that the reactance component comprise an electrical inductance connected in series with the load terminal at which the largest phase current occurs during normal operation. In this case, the reactance component is preferably formed by the electrical inductance. The use of a reactance component in the form of an electrical inductance can be particularly advantageously combined with the electrical contact device, which provides two electrical contact points for each of the load terminals. In this way, the series connection of the electrical inductance can be implemented particularly simply and cost-effectively.

[0037] A further development provides that the reactance component has an electrical capacitance that is connected between the load connection at which the smallest phase current occurs during normal operation and the electrical ground potential. This electrical development can advantageously be combined with the contact device, which has exactly one electrical contact point or contact location for each of the load connections. With the electrical capacitance, which preferably comprises an electrical capacitor, a corresponding electrical connection can be established between the respective load connection at which the smallest phase current occurs during normal operation and the electrical ground potential. This embodiment is also suitable for reducing the leakage current within the meaning of the invention. Combinations of the various embodiments can of course also be provided.

[0038] According to an advantageous development, it is proposed that the energy supply device has an electrical switching element for activating the reactance component. This development has the advantage that the effect of the reactance component does not need to be permanently activated. Rather, the electrical switching element enables the reactance component to be activated only when needed. It proves particularly advantageous if the electrical switching element or the reactance component is only activated when a high electrical power is present. For this purpose, it can be provided that the power and / or the phase currents are detected by means of respective sensors, corresponding sensor signals are evaluated to determine the corresponding power, and compared with a predetermined reference value.This design proves particularly advantageous when the reactance component could have an adverse effect on the leakage current at low power levels. The electrical switching element can be formed, for example, by an electromechanical switching element or an electronic switching element.

[0039] An electronic switching element within the meaning of this disclosure is a preferably controllable electronic switching element, for example a transistor, a thyristor, combination circuits thereof, in particular with parallel-connected freewheeling diodes, for example a metal oxide semiconductor field-effect transistor (MOSFET), an insulated gate bipolar transistor (IGBT), preferably with integrated freewheeling diodes, or the like.

[0040] The switching operation of a transistor means that, in the switched-on state, a very low electrical resistance is provided between the terminals forming the switching path, allowing a high current flow with a very low residual voltage. In the switched-off state, the switching path of the transistor is high-ohmic, meaning it provides a high electrical resistance, so that even with a high voltage applied across the switching path, there is essentially no current flow or only a very small, particularly negligible, current flow. This differs from linear operation, which, however, is not used in switch-mode energy converters.

[0041] The reactance component can be provided as a separate component. However, it can also be partially integrated into the filter or at least partially formed by one or more components of the filter.

[0042] The determination of the reactance value can be carried out at least partially automatically using a determination device that can be electrically detachably coupled to the power supply device, at least during the manufacturing process. The determination device can be signal-coupled to the current sensors and configured to determine the differential current. Furthermore, the determination device can be electrically detachably coupled to the load terminals in order to simulate an adjustable reactance component. Using an algorithm, it can then be determined to which of the phases the reactance component should be connected and what reactance value it should have. For this purpose, the determination device can have a program-controlled computer unit that at least partially provides the functionality of the determination device.Depending on this, the reactance component can then be determined and connected to the power supply device.

[0043] Furthermore, it is proposed that a reactance value of the electrical reactance component be set depending on the determined electrical power of the load unit, in particular the transformer. This further development allows the reactance value to be set at least partially during the intended operation of the energy supply device. For this purpose, it can be provided that the differential current is determined at predetermined times or at least partially continuously. Depending on this, a reactance value to be set can then be determined. The reactance component can be designed to be adjustable so that its reactance value can be changed. For this purpose, the reactance component can have an adjustment connection that is connected to the control unit of the energy supply device for signaling purposes.This allows the control unit to adjust the reactance value depending on the measured differential current. This adjustment process can be repeated at predefined times or upon specified events. A specified event could, for example, be a high power demand on the power supply system or something similar.

[0044] Although the method can, in principle, preferably be used during the manufacture of the power supply device, it is not limited to this. It is also possible to apply the method according to the invention repeatedly at predefined times and / or under predefined events, for example, to take into account changes to the power supply device due to its intended use.

[0045] For use cases or application situations that may arise during the method and which are not explicitly described here, it may be provided that, in accordance with the method, an error message and / or a request to enter user feedback is issued and / or a default setting and / or a predetermined initial state is set.

[0046] The features and combinations of features mentioned above in the description as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the respective combination specified, but also in other combinations without departing from the scope of the invention.

[0047] The exemplary embodiments explained below are preferred embodiments of the invention. The features and combinations of features previously specified in the description, as well as the features and combinations of features mentioned in the following description of exemplary embodiments and / or shown alone in the figures, can be used not only in the respective combinations specified, but also in other combinations. Thus, embodiments are also encompassed by the invention or considered disclosed that are not explicitly shown and explained in the figures, but which emerge and can be produced from the explained embodiments through separate combinations of features.The features, functions, and / or effects illustrated by the exemplary embodiments may, in and of themselves, represent individual, independently considered features, functions, and / or effects of the invention, each of which also further develops the invention independently of one another. Therefore, the exemplary embodiments are intended to encompass combinations other than those in the explained embodiments. Furthermore, the described embodiments may also be supplemented by further features, functions, and / or effects of the invention already described. The scope of protection of the invention is determined by the patent claims.

[0048] In the figures, the same reference symbols denote the same features or functions.

[0049] Regardless of the grammatical gender of a particular term, persons with male, female or other gender identities are included.

[0050] They show: Fig. 1 a magnetic resonance examination arrangement with a magnetic resonance device and an MR local coil connected to the magnetic resonance device, which is arranged on a patient for performing an examination on the patient; Fig. 2 shows a schematic block diagram of an energy supply device as used by the magnetic resonance examination arrangement according to Fig. 1 is included; Fig. 3 shows a schematic block diagram of a determination device for determining a reactance component for the power supply device according to Fig. 2; Fig. 4 is a schematic diagram in which two graphs show a leakage current at a low power and at a high power without the reactance component; and Fig. 5 a schematic diagram representation such as Fig. 4, in which the effects of the reactance component on the leakage current are shown by means of several graphs.

[0051] Fig. Figure 1 shows a partially sectioned view of a magnetic resonance examination system 10 comprising a magnetic resonance device 14 and a local coil 16. The magnetic resonance examination system 10 serves as an imaging method for the medical examination of a patient 12.

[0052] The magnetic resonance scanner 14 includes, among other things, a gradient power amplifier (GPA) and a main magnet 18. The gradient power amplifier is not shown in the figures. The main magnet 18 serves to generate a strong, in particular temporally constant, main magnetic field in a direction 20. The magnetic resonance scanner 14 further includes a patient receiving area 22, which is provided here as a tunnel and serves to receive the patient 12. The patient receiving area 22 is essentially cylindrical in shape and is surrounded in a circumferential direction by the main magnet 18. In principle, however, the patient receiving area 22 can also be designed differently.

[0053] The magnetic resonance device 14 further comprises a patient support device 24, which makes it possible to move the patient 12 into the patient receiving area 22.

[0054] For this purpose, the patient support device 24 has a patient table 26 that is arranged at least partially movable within the patient receiving area 22.

[0055] The magnetic resonance scanner 14 further includes a gradient coil unit 28, which can be used to generate magnetic field gradients that can be used for spatial encoding during an imaging examination. The gradient coil unit 28 is controlled in this case by a gradient control unit 32 of the magnetic resonance scanner 14. The main magnet 18 and the gradient coil unit 28 form a magnetic field source.

[0056] The magnetic resonance scanner 14 further includes a radio-frequency antenna unit 34, which, in the present embodiment, is permanently integrated into the magnetic resonance scanner 14 as a body coil. The radio-frequency antenna unit 34 is controlled by a radio-frequency antenna control unit 36 ​​of the magnetic resonance scanner 14. This makes it possible to generate radio-frequency magnetic resonance sequences in the examination area 30. During proper operation of the magnetic resonance scanner 14, excitation of atomic nuclei in the examination area 30 of the patient 12 can be achieved. MR signals are generated by relaxation of the excited atomic nuclei. The MR signals can be received by the radio-frequency antenna unit 34.

[0057] To control the components of the magnetic resonance scanner 14, the magnetic resonance scanner 14 has a control unit 38. The control unit 38 centrally controls the magnetic resonance examination system 10, for example, with respect to performing a predetermined examination on the patient 12, in particular performing a predetermined imaging gradient echo sequence. Furthermore, the control unit 38 has an evaluation unit (not shown in detail), by means of which received MR signals acquired during the examination can be evaluated.

[0058] The magnetic resonance scanner 14 further comprises a user interface 40, which is communicatively connected to the control unit 38. The user interface 40 comprises a display unit 42 and an input unit 44, each of which is communicatively connected to the control unit 38. Data and information, evaluation results, for example, imaging results, parameters related to the evaluation, and / or the like can be visually displayed via the display unit 42. The display unit 42 can, for example, comprise a monitor or the like. Using the user interface 40, it is possible for a user of the magnetic resonance scanner 14 and the magnetic resonance examination arrangement 10 to supply data to the control unit 38, for example, parameters for conducting the examination, control data, information, and / or the like.

[0059] To supply the magnetic resonance device 14, in particular the gradient power amplifier, with electrical energy, the magnetic resonance device 14 is connected to a power supply device 56. In the present case, the power supply device 56 is part of the magnetic resonance examination arrangement 10 and is designed separately from the magnetic resonance device 14. In alternative embodiments, the power supply device 56 can also be at least partially a component of the magnetic resonance device 14. The power supply device 56 can be provided exclusively for supplying the magnetic resonance device 14 with electrical energy. However, it can also be provided that the power supply device 56 supplies other devices of the magnetic resonance examination arrangement 10 with electrical energy.

[0060] Out of Fig. 1 shows that a local coil 16 is arranged on the patient 12 in the examination area 30. In this case, the local coil 16 is arranged on a surface of the patient 12 in the examination area 30. The local coil 16 has a connecting cable 46, which is connected in a connecting area 52 to a connecting cable 54 of the magnetic resonance device 14 for communication and / or signaling purposes. For this purpose, a coil connecting element 48 is provided in the connecting area 52, which in this case is firmly connected to the connecting cable 46. The coil connecting element 48 is designed as a plug.

[0061] Furthermore, a device connection element 50 is provided in the connection area 52, which in this case is firmly connected to the connecting cable 54. With the coil connection element 48 and the device connection element 50, a detachable connection of the local coil 16 to the magnetic resonance device 14 can be realized in the connection area 52. In this way, it is possible to couple a respective local coil 16 to the respective magnetic resonance device 14. The device connection element 50 can be designed as a socket. The connection area 52 is a standardized connection area in this case, so that a connection of any local coil 16 to any magnetic resonance device 14 can be achieved based on this standard. Both the coil connection element 48 and the device connection element 50 are shielded in this case.

[0062] In Fig. 1, only a single connection unit 52 is provided for connecting a single local coil 16. In alternative embodiments, it can of course be provided that multiple connection units 52 are provided, which allow more than one local coil to be connected. Furthermore, it can be provided that the device connection element 50 can be arranged at any suitable location on the patient table 26. It can also be provided that more than one single device connection element 50 is provided, wherein the multiple device connection elements 50 can preferably be arranged at different positions, in particular on the patient table 26. The radio-frequency antenna unit 34 can be adapted accordingly, if necessary.

[0063] Fig. Figure 2 shows a schematic block diagram of the energy supply device 56 as used by the magnetic resonance examination arrangement 10 according to Fig. 1. The power supply device 56 is connected in this case to a three-phase power supply network 58 via a residual current device 62. The three-phase power supply network 58 is in this case a public power supply network which provides a three-phase alternating voltage with an effective value of approximately 400 volts between the respective phases at a frequency of approximately 50 Hz. The power supply network 58 provides a first phase L1, a second phase L2, and a third phase L3, each of which provides an alternating voltage with an amplitude of approximately 325 volts. The alternating voltages of the three phases L1, L2, L3 are in this case phase-shifted by approximately 120°.

[0064] The alternating voltages of phases L1, L2, and L3 are provided relative to an electrical ground potential 60. The power supply network 58 can be formed, for example, by an IT network or the like. IT networks are preferably used, for example, in hospital operating rooms, because an interruption in the power supply can endanger the life of the patient. However, IT networks are also frequently used in hospital intensive care units. There are also other applications in industry. The use, advantages, and effects of different types of power supply networks are known to those skilled in the art, which is why further detailed explanations are omitted here.

[0065] Out of Fig. 2 shows that phases L1, L2, and L3 of the power supply network 58 are electrically coupled to the respective phase terminals 66, 68, and 70 of the power supply device 56 via the residual current circuit breaker 62. The function of the residual current circuit breaker 62 is also known to those skilled in the art, which is why a detailed explanation is also omitted here.

[0066] In the present case, the residual current device 62 is designed for a rated residual current or tripping current of approximately 30 mA. For this purpose, the functionality of the residual current device 62 includes determining a differential current of the respective phase currents of the respective phases L1, L2, L3. This differential current essentially corresponds to the leakage current flowing from the power supply device 56 to the electrical ground potential 60. As soon as this leakage current reaches a value of approximately 30 mA, the residual current device 62 trips and disconnects the phases L1, L2, L3 from the respective phase terminals 66, 68, 70. This allows for appropriate protection, as required, among other things, by standards.

[0067] The power supply device 56 is designed to be neutral conductor-free. The power supply device 56 serves for the reference-potential-free electrical connection to the three-phase electrical power supply network 58. In this case, the connection is designed to be neutral conductor-free.

[0068] The power supply device 56 has a connection unit 80 for electrically coupling the power supply network 58. The connection unit 80 has a number of phase connections 66, 68, 70 corresponding to the number of phases L1, L2, L3 of the power supply network 58. Thus, the phase connection 66 is electrically coupled to phase L1, the phase connection 68 to phase L2, and the phase connection 70 to phase L3. The electrical coupling is established via the residual current device 62.

[0069] The power supply device 56 has a transformer 72 as a load unit with transformer terminals 74, 76, 78 as load terminals. A respective transformer terminal 74, 76, 78 is electrically coupled to the respective phase terminal 66, 68, 70 via a filter unit 82 in order to carry a respective phase current. The filter unit 82 is included in the power supply device 56 and serves, among other things, to reduce line-borne interference. The filter unit can, as can be seen from Fig. 2, a three-phase current-compensated choke 96 in conjunction with respective Y capacitors 94. The filter unit 82 is electrically coupled to the ground potential 60.

[0070] In addition to the transformer terminals 74, 76, 78, the transformer 72 has terminals for secondary phases U, V, W. A three-phase bridge rectifier (not shown in the figures) is connected to the terminals for secondary phases U, V, W.

[0071] The transformer 72 is designed as a three-phase transformer, with a primary side configured as a delta connection and a secondary side configured as a star connection. However, depending on requirements, the connection type of the primary side and / or the secondary side can also vary. For example, both the primary side and the secondary side can be configured as a star connection.

[0072] The power supply device 56 further comprises an electrical contact device 86 which is electrically coupled to all transformer terminals 74, 76, 78.

[0073] The contact device 86 has contact points 88 electrically connected to the respective transformer terminals 74, 76, 78. The electrical contact device 86 has exactly one electrical contact point or contact point 88 for each of the transformer terminals 74, 76, 78. Each of the contact points 88 is electrically coupled to one of the transformer terminals 74, 76, 78. In addition, the electrical contact device 86 has a further contact point 90 that is electrically coupled to an electrical ground potential 60. In the present case, it is provided that a corresponding contact point 90 is provided for each contact point 88, so that a contact point pair is formed in each case, which can be connected to a two-pole reactance component.

[0074] In this case, transformer 72 is designed as a galvanically isolated transformer between the primary and secondary sides. However, this is not relevant to the invention. Therefore, galvanic isolation does not need to be provided by transformer 72.

[0075] In this case, the filter unit 82 comprises at least the current-compensated choke 96, as well as a Y capacitor 94 for each of the phases L1, L2, L3. The Y capacitors 94 are electrically coupled to the respective phase L1, L2, L3 by one of their respective terminals. The other terminal of the Y capacitors 94 is connected to the electrical potential 60.

[0076] In the present case, it is provided that the power supply device 56 has a capacitor 84 as an electrical reactance component, which is electrically coupled to one of the transformer terminals, in this case to the transformer terminal 76. During normal operation, the smallest phase current occurs at this transformer terminal 76. The fact that during normal operation, particularly at high power levels, a not insignificant leakage current occurs due to tolerances and / or asymmetries can have undesirable consequences. In particular, there is the possibility that the residual current device 62 may undesirably trigger even though no fault is actually present. This problem can be reduced by means of the capacitor 84, as will be explained in more detail below.

[0077] For this purpose, it is provided that at least during the manufacture of the energy supply device 56, respective electrical phase currents of the transformer terminals 74, 76, 78 are measured by means of respective current sensors 100, 102, 104 ( Fig. 3) are recorded and the phase currents are evaluated to determine a differential current.

[0078] In the present embodiment, this is carried out by means of a determination device 64 during the manufacture of the energy supply device 56, as shown in Fig. 3 using an electrical schematic block diagram. The determination device 64 has the current sensors 100, 102, and 104, which can be designed in the manner of a respective current clamp to be detachably connected to corresponding line sections of the power supply device 56 in which the respective phase currents of the phases L1, L2, L3 occur. Furthermore, the determination device 64 has a control unit 98 to which the current sensors 100, 102, and 104 are connected in order to provide respective sensor signals. The differential current can be determined by means of a control unit 98.

[0079] In addition, the determination device 64 has a connection unit 106 connected to the control unit, which has six contact pins 108. The contact pins 108 are connected via electrical lines to a control unit 98 of the determination device 64. The contact pins 108 serve to be electrically detachably connected to the contact points 88, 90 for determining the reactance component and its reactance value.

[0080] Between respective pairs of contact pins 108, a respective adjustable electrical capacitance can be provided by means of the control unit 98, as shown in Fig. 3 is shown by the dashed representation of adjustable capacitors. The respective capacitance value can be adjusted from approximately 0 F to approximately 500 nF by means of the control unit. The control unit 98 executes an automated sequence in which the respective capacitance values ​​between the contact pins 108 are increased to determine the effect on the differential current.

[0081] First, the phase where the smallest phase current occurs is determined. The capacitance value is then adjusted as a reactance value for this phase until a reduction in the differential current or leakage current can be achieved. For this purpose, the differential current can be compared with a specified reference value. As soon as the comparison shows that the differential current is smaller than the reference value, the determined capacitance value can be output. The determination device 64 can then be disconnected from the power supply device 56.

[0082] For the specific phase, a capacitor 84 with the determined capacitance value can then be connected to the contact device 86. For this purpose, the capacitor 84 is soldered to the corresponding contact pins. Alternatively, the capacitor 84 can also be electrically connected using terminals or plug contacts.

[0083] In this way, the power supply device 56 already receives the corresponding reactance component during production, namely in this case the capacitor 84, with which a reduction of the leakage current can be achieved during normal operation, especially during high power levels.

[0084] The effect of the invention is illustrated by the following diagrams according to the Fig. 4 and Fig. 5 is further explained.

[0085] Fig. Figure 4 shows a schematic diagram of the differential current determined by the determination device 64. An ordinate represents the current, and an abscissa represents time. For a low power of the power supply device 56, a graph 110 shows that the leakage current is essentially in the range of approximately zero mA. However, if a high power is provided by the power supply device 56, even if only briefly, it becomes apparent that a considerable leakage current occurs due to tolerances and asymmetries, as shown by graph 112. This leakage current can lead to nuisance tripping of the residual current device 62.

[0086] Fig. 5 shows a schematic diagram of how Fig. 4, in which graphs 114 to 120 illustrate the effects at high power when a capacitor 84 is provided for the phase with the smallest phase current. It can be seen that graph 114 shows the differential current for a capacitance of approximately zero farads. Graph 116 shows the differential current for a capacitance value of 50 nF under otherwise identical conditions. Graph 118 shows the differential current for a capacitance value of approximately 100 nF. It can be seen that the amplitude of the differential current decreases with increasing capacitance value. Graph 120 further illustrates how the leakage current develops when the capacitance value is 500 nF. The result is a significant increase in the differential current. This is a consequence of overcompensation.

[0087] Overall, the invention can reduce leakage current problems by selecting a suitable reactance component, in this case a capacitor. Alternatively or additionally, a corresponding inductance can also be provided.

[0088] Out of Fig.2 further shows that the capacitor 84 is electrically connected to the ground potential 60 via an electrical switching element 92, depending on its switching state. The electrical switching element 92 is formed in the present case by a relay, the switching state of which is controlled by a control unit (not shown) of the power supply device 56. For this purpose, the control unit (not shown) detects an electrical power of the power supply device 56. The electrical power is compared with a comparison value. As long as the electrical power is less than the comparison value, the switching element 92 remains in the off switching state, i.e., it provides an electrical interruption.As soon as the electrical power is greater than the comparison value, the switching element 92 is switched to the switched-on state, and an electrical connection is established between the capacitor 84 and the ground potential 60. This makes it possible to reduce or prevent any adverse effect of the capacitor 84 at low power. This configuration allows the invention to be further improved.

[0089] The embodiments serve solely to explain the invention and are not intended to limit it.

Claims

[1] Method for producing an electrical energy supply device (56) for electrical coupling, in particular a reference-potential-free or neutral-conductor-free electrical coupling, to a multi-phase electrical energy supply network (58), wherein the energy supply device (56) has a multi-phase inductive or capacitive load unit (72) with a number of load connections (74, 76, 78) corresponding to a number of phases (L1, L2, L3) of the energy supply network (58), wherein a respective one of the load connections (74, 76, 78) is electrically coupled to a respective phase (L1, L2, L3) of the electrical energy supply network (58), wherein respective electrical phase currents of the load connections (74, 76, 78) are detected by means of at least one current sensor (100, 102, 104), the phase currents are evaluated and a differential current is determined, characterized bythat the phase (L1, L2, L3) of the electrical power supply network (58) with the smallest or the largest phase current is determined and this phase (L1, L2, L3) is electrically coupled to an electrical reactance component (84) whose reactance value is determined as a function of the differential current. [2] Method for operating a power supply device (56) manufactured according to claim 1, characterized by that during normal operation an electrical power of the load unit (72) is determined and the electrical reactance component (84) is activated depending on the determined electrical power. [3] Method according to claim 2, characterized by that a reactance value of the electrical reactance component (84) is set depending on the determined electrical power of the load unit (72). [4] Energy supply device (56) for electrical connection, in particular without reference potential or without a neutral conductor, to a multi-phase electrical energy supply network (58), with - a multi-phase inductive or capacitive load unit (72) having a number of load connections (74, 76, 78) corresponding to a number of phases (L1, L2, L3) of the power supply network (58), and - a connection unit (80) for electrically coupling the power supply network (58), wherein the connection unit (80) has a number of phase connections (66, 68, 70) corresponding to the number of phases (L1, L2, L3) of the power supply network (58), wherein a respective load connection (74, 76, 78) is electrically coupled to a respective phase connection (66, 68, 70) in order to carry a respective phase current, characterized by - at least one electrical reactance component (84) which is electrically coupled to one of the load connections (74, 76, 78), wherein the reactance component (84) is electrically coupled to that one of the load connections (74, 76, 78) at which the smallest or the largest phase current occurs during normal operation, wherein, during manufacture of the energy supply device (56), respective electrical phase currents of the load connections (74, 76, 78) are detected by means of at least one current sensor (100, 102, 104), the phase currents are evaluated, a differential current is determined, and a reactance value of the reactance component (84) is determined as a function of the differential current, and wherein the energy supply device (56) is manufactured in particular according to claim 1. [5] Energy supply device (56) according to claim 4, characterized byan electrical contact device (86) which is electrically coupled to all load terminals (74, 76, 78) and which has contact points (88) electrically connected to the respective load terminals (74, 76, 78) for, in particular, detachably electrically contacting the reactance component (84). [6] Energy supply device (56) according to claim 5, characterized by that the electrical contact device (86) has two electrical contact locations for each of the load terminals (74, 76, 78), wherein the electrical contact device (86) is electrically coupled in series with the load terminals (74, 76, 78). [7] Energy supply device (56) according to claim 5 or 6, characterized bythat the electrical contact device (86) has exactly one electrical contact point (88) for each of the load connections (74, 76, 78), wherein the electrical contact device (86) has a further contact point (90) which is electrically coupled to an electrical ground potential (60). [8] Energy supply device (56) according to one of claims 4 to 7, characterized by that the reactance component (84) has an electrical inductance which is connected in series with the load terminal (74, 76, 78) at which the largest phase current occurs during normal operation. [9] Energy supply device (56) according to one of claims 4 to 8, characterized by that the reactance component (84) has an electrical capacitance which is connected between the load terminal (74, 76, 78) at which the smallest phase current occurs during normal operation and the electrical earth potential (60). [10] Energy supply device (56) according to one of claims 4 to 9, characterized by an electrical switching element (92) for activating the reactance component (84). [11] Magnetic resonance apparatus (14) with a gradient power amplifier and a power supply device (56), characterized by that the energy supply device (56) is designed according to one of claims 4 to 10.

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