Optimized power resistor with improved electromagnetic tolerance

Abstract

The invention relates to a power resistor unit (1) which has an integrated electromagnetic interference damping function. The direct integration of at least one inductance element (4) into the resistor element (2) or within the power resistor unit (1) results in an effective damping of electromagnetic emissions which arise when switching the resistor element (2). This integration makes it possible to combat electromagnetic interference at the source thereof.

Description

[0001] 2024P00371 EN November 20, 2024

[0002] 1

[0003] Optimized power resistance with improved electromagnetic compatibility

[0004] DESCRIPTION

[0005] The present application relates to a power resistor, which can be constructed from resistor units that are connected together. In particular, such a resistor is used as a braking resistor.

[0006] In the field of drive technology, particularly in commercial vehicles, excess braking energy can be converted into braking resistors. For example, the vehicle's kinetic energy is converted into electrical energy by a regenerative brake (in recuperation mode for drive motors), and if this energy cannot be used otherwise (e.g., stored in a battery), it is converted into a braking resistor.

[0007] It is important to avoid current spikes, especially when switching (on / off or regulating the current flow) the power resistors, in order to ensure good electromagnetic compatibility and controllability of the power resistors. Attenuation of electromagnetic interference or parasitic capacitances that can occur during their operation is equally important.

[0008] Document DE 10 2023 202 784 A1 discloses a liquid-cooled braking resistor which has at least two coolable resistance units, each of which has at least one liquid-flowable area and at least one electrical conductor with two electrical contact surfaces, wherein a sealing element is arranged between two coolable resistance units and the at least one spring contact of the sealing element touches two electrical contact surfaces of each adjacent coolable resistance unit.

[0009] Furthermore, in the current state of the art, internal electromagnetic interference filters (EMI-2024P00371 DE) are used for the operation of so-called choppers, such as traction converters.

[0010] 2

[0011] Internal EMI filters are used to minimize electromagnetic interference. These filters are essential for ensuring electromagnetic compatibility (EMC) compliance. However, using the chopper often requires modifying or updating these internal EMI filters to effectively limit disruptive emissions (conducted and radiated electromagnetic emissions / interference). This presents a challenge, as such modifications incur additional costs and slow down the implementation process.

[0012] The object of the present invention is therefore to provide resistors that enable the use of inverters (devices for adjusting the supply voltage and frequency) without extensive hardware modifications, especially to EMI filters, while effectively attenuating (or suppressing) electromagnetic interference. This should not only ensure the electromagnetic compatibility of the system but also reduce installation and operating costs.

[0013] This problem is solved by a power resistance unit according to claim 1 and a use according to claim 12. Further advantageous embodiments are the subject of the dependent claims.

[0014] A power resistor unit according to the invention comprises: at least one resistive element and at least one connection device as well as an electromagnetic interference filter configured to dampen electromagnetic emissions caused by switching the at least one resistive element (e.g. switching on / off or regulating the current flow), wherein the electromagnetic interference filter includes at least one inductor element which is directly integrated into the power resistor unit.

[0015] The advantage of the power resistor unit is that the disruptive electromagnetic interference within the power resistor unit is dampened by the inductor element. Thus, the power resistor 2024P00371 DE

[0016] 3

[0017] The unit can also be controlled with a converter without having to adjust the hardware, especially the interference filters.

[0018] Preferably, the inductance element is further configured to have a resonant frequency that is matched to the frequency range of the electromagnetic emissions generated by switching in order to maximize their absorption and thus effective damping.

[0019] Preferably, the power resistance unit of a first embodiment is configured as follows: The at least one inductance element is connected in series to a resulting total resistance, wherein the resulting total resistance is formed by an arrangement of at least two parallel-connected resistance elements.

[0020] The advantage of this embodiment is that only a single coil is sufficient to dampen the interference of the resistive elements.

[0021] Preferably, the power resistor unit of a second embodiment is configured as follows: At least one inductance element is connected in series to each of at least two parallel-connected resistor elements, which is integrated directly onto the respective resistor element, wherein preferably the dimensioning of the individual inductance elements is oriented to the partial currents flowing through the respective parallel-connected resistor elements in order to enable effective damping of electromagnetic interference.

[0022] The advantage of this embodiment is that each resistor element inherently contains an interference filter, and the individual resistor elements can be combined as desired within a module. This enables easier and more cost-effective manufacturing.

[0023] Preferably, the power resistor unit of a second embodiment is configured as follows: The at least one inductance element is applied directly to the resistor element, preferably soldered on. 2024P00371 DE

[0024] 4

[0025] This enables even simpler and more cost-effective manufacturing, which can be carried out in one process step, for example by printing the conductor track of the resistor element onto a plate or similar.

[0026] Preferably, the coolable power resistor unit comprises at least one inductance element and at least one coil.

[0027] The advantage is that an inductance element can be implemented simply and cost-effectively as a coil.

[0028] Preferably, the power resistor unit is further configured such that the electromagnetic interference filter enables the use of inverters by attenuating electromagnetic emissions of the electromagnetic interference filter to a level that corresponds to the electromagnetic compatibility of the inverter.

[0029] The advantage is that the inductor element dampens electromagnetic interference sufficiently to ensure electromagnetic compatibility of the entire system. Furthermore, there is no need to adjust the internal electromagnetic interference filters of the inverters, as the power resistor unit already incorporates an integrated electromagnetic interference filter.

[0030] Preferably, the power resistor unit is further configured such that the inductance element is dimensioned to have an inductance optimized for a specific frequency range associated with the electromagnetic emissions caused by switching the at least one resistor element.

[0031] The inductor element can be adjusted to filter or attenuate the desired high-frequency signals. 2024P00371 DE

[0032] 5

[0033] Preferably, the power resistance unit is further configured to consist of braking resistors and / or heating elements.

[0034] Preferably, the power resistor unit is further configured such that the electromagnetic interference filter includes additional filter components consisting of at least one of capacitors, resistors and ferrite spheres, and which are preferably arranged to improve the attenuation of electromagnetic interference filter emissions.

[0035] Preferably, the power resistor unit is further configured in such a way that the power resistor unit is coolable.

[0036] One use of the power resistance unit according to the invention is particularly in road and rail vehicles.

[0037] In other words, the present invention solves the aforementioned problem by integrating an inductor element directly into the power resistor unit. This inductor element, integrated into the power resistor or unit, forms a filter that effectively attenuates EMI emissions without requiring any hardware modifications for operation with inverters. This solution offers a direct and cost-effective approach to reducing electromagnetic interference, thereby enabling the use of inverters in a wider range of applications without the need to update internal EMI filters or make other hardware-based adjustments.

[0038] Exemplary embodiments of the present invention will be explained in more detail below with reference to the accompanying figures.

[0039] Fig. 1 shows a first side of a plate for a power resistance element according to the present invention.

[0040] Fig. 2 shows a schematic equivalent circuit of a power resistor element according to the prior art. 2024P00371 DE

[0041] 6

[0042] Fig. 3 shows a circuit diagram of a power resistor unit according to a first embodiment of the present invention with an inductance element on the resistor plane.

[0043] Fig. 4 shows a schematic equivalent circuit diagram of a power resistance element according to a second embodiment of the present invention.

[0044] Fig. 5 shows a circuit diagram of a power resistance unit according to a second embodiment of the present invention with an inductance element on the plate plane.

[0045] Figure 1 shows a first side 19e of a plate 19. This plate 19 generally has a hexagonal shape (essentially consisting of two triangles and a rectangle), with an elongated part and a shorter part. Several protrusions 15 are arranged on the surface (especially the rectangular, elongated part) of the first side 19e. On the first side 19e, the protrusions 15 therefore have the form of depressions. An electrical conductor 17 extends between the protrusions 15. This conductor is arranged on an electrically insulating layer 18, which was previously applied to the first side 19e of the plate 19 – for example, by a screen printing process. The electrical conductor 17 also has two electrical contact surfaces 13 on the first surface 19e. The electrical conductor 17 is arranged in a meandering pattern around the first protrusions 15. The electrical conductor 17 thus has the largest possible surface area.A cooling fluid flows on the second side of plate 19. Mounting sections (not shown here) can be provided at both outermost points (the apex of the hexagon's triangles) – these serve to clamp several plates 19 together using a fixing element (not shown here), for example, a screw.

[0046] The electrical conductor 17 can be connected to a power terminal 3 (not shown here) via an electrical connection. This electrical connection is called a connection device. If several plates 19 are connected, and thus 2024P00371 DE

[0047] 7

[0048] If the resistance elements 2 (not shown here) are connected, they can also be connected with electrical connections.

[0049] Several plates – each acting as a power resistor – can be connected together to form a power resistor unit. The resulting resistor element can be any resistor of any dimension.

[0050] The power resistance unit can also be operated uncooled or not liquid-cooled according to the present invention.

[0051] Figure 2 shows a schematic equivalent circuit of a resistive element, or plate 19, of a power resistor according to the prior art. The schematic equivalent circuit shown depicts a plate 19 on which an electrical conductor, serving as the resistive element, is mounted. This assembly is typically part of a larger electronic or electrical system in which the resistive element functions, for example, as a braking resistor or heating element. A control unit is provided to control the resistive element, for example, by switching it on and off or regulating the amount of current flowing through it. In reality, the physical proximity and mutual electromagnetic interference between the system components (plate, electrical conductor, control unit, etc.) lead to parasitic capacitive effects.These capacitive effects can be schematically represented within the circuit as a capacitor. This means that the real-world resistance element, together with these parasitic effects, can be considered a series circuit of a resistor (represented by the electrical conductor on the plate) and a capacitor (represented by the parasitic capacitances).

[0052] The main problem identified in the prior art concerns the behavior of the resistive element under load conditions, particularly during switching. High current spikes occurring during switching of the resistive element lead to undesirable electromagnetic emissions and interference (EMC / EMI problems). These can affect the performance of other electronic components within the system.

[0053] 8 negatively affect the same system or adjacent systems. Furthermore, the limited controllability of the resistance element presents another problem.

[0054] Figure 3 illustrates, according to a first embodiment, an improved arrangement of a plate with a resistive element, in which a solution for damping parasitic capacitive effects is implemented by integrating at least one inductor element 4, preferably a coil, at the resistive level. The design aims to increase the electromagnetic compatibility (EMC) of the system and to enable more efficient control of the resistive element.

[0055] The focus is on the coil, which is positioned in series with a parallel connection of several individual resistors. Each of these resistors is arranged on separate plates, which provide the physical basis for defining the individual resistance parameters. The series connection of the coil with the parallel resistors forms a network dimensioned to effectively dampen the effects of parasitic capacitive effects occurring in the circuits. The dimensioning of inductor 4 is such that it provides the necessary inductance for damping while simultaneously minimizing the voltage drop across the overall arrangement.

[0056] To determine the dimensions and inductance of the coil, it is first necessary to identify the frequency ranges of the EMI interference generated by the power resistor or to which it is exposed. These frequencies can result from the switching behavior of the semiconductor and the switching frequency. Based on the identified interference frequencies, the required filter characteristics are determined. This includes determining the attenuation requirement at the relevant frequencies to effectively reduce interference and, if applicable, to meet the required EMC standards. The dimensioning of the coil and, if applicable, the coil type (e.g., choke coils, common-mode chokes, etc.) involves defining all physical parameters, such as inductance value, core material, core shape, and windings, necessary to achieve the desired attenuation. 2024P00371 DE

[0057] 9

[0058] The coil within this arrangement serves to dampen the current spikes that occur during system operation and the electromagnetic interference caused by parasitic capacitances. This configuration achieves a significant reduction in electromagnetic emissions, resulting in improved electromagnetic compatibility of the entire system.

[0059] The coil can either be arranged directly in series connection on one of the plates 19 (not shown here) or on a separate plate 19. The coil can also be arranged in the electrical circuit outside of a plate 19. In either case, the coil is arranged so that it is installed within the power resistor unit 1 in the circuit.

[0060] The inductance element 4 within the power resistor unit 1 makes it possible to use inverters without extensive hardware modifications, especially to the EMI filters, and to effectively dampen the electromagnetic interference of the system.

[0061] Figure 4 shows an equivalent circuit diagram of a power resistance element of a second embodiment, which differs from the prior art - as shown in Figure 2 - by the introduction of an inductance element 4, preferably a coil, which is positioned directly on the plate 19.

[0062] The figure shows a circuit in which the coil (inductor element 4) is connected in series with the resistor element 2 and the capacitor 5 (shown schematically here – which is formed by the resistor element 2). This configuration aims to effectively dampen the effects of high-frequency current spikes. The direct integration of the coil onto the plate 19, on which the resistor elements 2 are also arranged, provides a compact and efficient solution for minimizing electromagnetic interference.

[0063] The coil works synergistically with the resistor and capacitor elements to form a resonant circuit that dampens the high-frequency current components, in order to reduce the 2024P00371 DE

[0064] 10. To improve the electromagnetic compatibility of the circuit. This improved harmonization leads to a significant reduction in unwanted electromagnetic emissions and increases the reliability and performance of the entire system.

[0065] The inductance element 4, which is embedded directly onto the plate 19 of a resistance element 2, also makes it possible to use inverters without extensive modifications to the hardware, especially the EMI filters, and thereby effectively dampen the electromagnetic interference of the system.

[0066] The coil can be attached to the resistor layout of a single plate 19 by direct soldering. This integration enables spatial and functional optimization within the overall circuit design. The production of the power resistor unit 1 with integrated inductor element 4 is achieved by soldering or printing the inductor element 4, preferably the coil, directly onto the electrical conductor 17 of the resistor element 2.

[0067] The coil is not considered a separate component, but rather an integral part of the resistor array on the plates 19. By directly placing and connecting it to the resistor layout, this design enables a modular approach. The stacked arrangement of the individual plates 19 – each with an integrated coil – allows for the efficient integration of small coils. This approach makes optimal use of the available space and results in a compact design.

[0068] A significant advantage of the second embodiment lies in the simplification of the manufacturing processes. By directly applying and soldering the coil onto the plate 19, additional manufacturing processes are eliminated. This direct integration not only reduces manufacturing costs but also minimizes the likelihood of connection problems that could occur with separate components.

[0069] Furthermore, the described configuration offers additional functional advantages.

[0070] By integrating it into the resistor layout, the coil also benefits from a 2024P00371 DE

[0071] 11 Improved thermal management capability, as heat can be efficiently dissipated via the cooled plate 19. This increases the overall reliability of the circuit and prevents overheating, which could impair the performance and lifespan of the components.

[0072] Figure 5 shows the circuit diagram of a power resistor unit 1, in which various resistor elements 2 are each connected in series with an inductor element 4 and combined to form a functional unit. Each of these series-connected pairs is integrated on a single plate 19 (see Figure 4 - not explicitly shown here), with several of these plates subsequently connected in parallel to each other to form the entire power resistor unit 1.

[0073] The layout of this circuit allows the current from the input source to be distributed across all parallel-connected resistor and inductor pairs. This targeted current distribution offers the advantage of minimizing the size of each inductor. As a result, each individual coil within the system can be assigned a smaller dimension (number of turns, size, etc.) without compromising the functionality or efficiency of the entire unit.

[0074] Another advantage of this arrangement lies in the improved scalability and flexibility of the power resistor unit 1. The parallel connection allows the electrical properties of the unit, such as the total resistance, to be specifically controlled, with each plate already incorporating an intrinsic electromagnetic interference filter.

[0075] The power resistors according to the first or second embodiment are also controllable (regulating current flow or switching on and off), wherein the internal electromagnetic interference filter or the internal inductance element 4 of the resistor element 2 is used to dampen electromagnetic emissions during operation of the system, thereby enabling the use of standard inverters without special electromagnetic 2024P00371 DE

[0076] 12

[0077] Interference filter modifications are enabled. Therefore, no external EMI filters are required. The system can thus attenuate emissions without any hardware adjustments (such as modifying an external filter).

[0078] 2024P00371 DE

[0079] 13

[0080] REFERENCE MARK LIST

[0081] 1 power resistor unit

[0082] 2 Resistance element 3 Electrical energy source

[0083] 4 inductance element

[0084] 5 Capacitor

[0085] 13 electrical contact area 15 elevation

[0086] 17 electrical conductors

[0087] 18 insulating layer

[0088] 19 plates

[0089] 19e first side of the record

Claims

2024P00371 DE 14 PATENT CLAIMS 1. Power resistance unit (1) comprising: at least one resistive element (2); at least one terminal device (3); an electromagnetic interference filter configured to attenuate electromagnetic emissions caused by switching the at least one resistive element, wherein the electromagnetic interference filter includes at least one inductor element (4) integrated into the power resistance unit (1).

2. Power resistance unit (1) according to claim 1, wherein the inductance element (4) is configured to have a resonant frequency that is tuned to the frequency range of the electromagnetic emissions generated by switching in order to maximize their absorption and thus effective damping.

3. Power resistance unit (1 ) according to claim 1 or 2, wherein the at least one inductance element (4) is connected in series to a resultant total resistance, wherein the resultant total resistance is formed by an arrangement of at least two parallel connected resistance elements (2).

4. Power resistance unit (1 ) according to claim 1 or 2, wherein at least one inductance element (4) is connected in series to each of at least two parallel-connected resistance elements (2), which is integrated on the respective resistance element (2), wherein preferably the dimensioning of the individual inductance elements (4) is oriented to the partial currents flowing through the respective parallel-connected resistance elements (2) in order to enable effective damping of electromagnetic interference.

5. Power resistance unit (1) according to claim 4, 2024P00371 DE 15 wherein the at least one inductance element (4) is applied to the resistance element (2), preferably soldered on.

6. Power resistance unit (1 ) according to one of the preceding claims, wherein the at least one inductance element (4) comprises at least one coil.

7. Power resistance unit (1) according to any of the preceding claims, further comprising: an inverter, wherein the electromagnetic interference filter is configured to enable the use of the inverter by attenuating electromagnetic emissions of the electromagnetic interference filter to a level corresponding to the electromagnetic compatibility of the inverter.

8. Power resistance unit (1) according to one of the preceding claims, wherein the inductance element (4) is dimensioned to have an inductance optimized for a specific frequency range associated with the electromagnetic emissions caused by switching the at least one resistance element (2).

9. Power resistance unit (1) according to one of the preceding claims, wherein the power resistance unit (1) comprises braking resistors and / or It has heating elements.

10. Power resistor unit (1) according to one of the preceding claims, wherein the electromagnetic interference filter comprises additional filter components consisting of at least one of capacitors, resistors and ferrite spheres, and which are preferably arranged to improve the attenuation of electromagnetic interference filter emissions.

11. Power resistance unit (1) according to one of the preceding claims, wherein the power resistance unit (1) is coolable. 2024P00371 DE 16 12. Use of the power resistance unit (1 ) according to any one of claims 1 to 11 in vehicles, in particular in road and rail vehicles.

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