Electrical resistance

Abstract

Disclosed is an electrical resistor (1), in particular an electrical braking resistor, comprising: - a first electrical connection (3); - a second electrical connection (4); - a plurality of partial resistors (2) connected in parallel, each partial resistor (2.1, 2.2, ..., 2.n) being designed for a maximum power that can be supplied individually to the partial resistor (2.1, 2.2, ..., 2.n); - a switching device (5) which is designed to connect individual partial resistors (2.1, 2.2, ...2.n) of the at least two partial resistors (2) to the first electrical connection (3) and the second electrical connection (4), wherein the resistor (1) is designed to distribute an electrical power, which is supplied to the resistor (1) via the terminals (3, 4), by means of the switching device (5) as partial power to individual partial resistors (2.1, 2.2, ...2.n) of the plurality of partial resistors (2), that the partial power supplied to at least one partial resistor (2.1, 2.2, ...2.n) of the plurality of partial resistors (2) corresponds at least to the maximum power that can be supplied to this partial resistor (2.1, 2.2, ...2.n) or that the partial power which is supplied to the at least one partial resistor (2.1, 2.2, ...2.n) of the plurality of partial resistors (2) is supplied by means of an electrical connection, which is permanently established by the switching device (5), between the first electrical connection (3), the at least one partial resistor (2.1, 2.2, ...2.n) and the second electrical connection (4).

Description

[0001] The present invention relates to an electrical resistor, in particular a braking resistor.

[0002] Particularly in the field of drive technology, especially in commercial vehicles, excess braking energy can be converted into braking resistors. The vehicle's kinetic energy is converted into electrical energy, for example, by a generator brake (drive motor in recuperation mode). If this energy cannot be used elsewhere (for example, stored in a battery), it is converted into heat in a braking resistor. The resistor acts as a consumer, converting electrical energy into heat. This heat must then be dissipated accordingly to prevent the braking resistor from overheating.

[0003] Resistors of this type typically comprise a plurality of partial resistors connected in parallel. The power is conducted through these partial resistors, which are supplied to the resistor via electrical connections. The electrical power is typically supplied to the partial resistors by a switching device, in particular comprising switching means, which sets the required current using pulse width modulation (PWM).

[0004] Since the partial resistors act as parasitic capacitances, this results in the problem that high current inputs into the partial resistors occur due to the PWM.

[0005] Therefore, the object of the present invention is to reduce this.

[0006] This problem is solved by the subject matter of the independent claims. Advantageous further developments are the subject matter of the dependent claims.

[0007] Disclosed is an electrical resistor, in particular an electrical braking resistor. The resistor comprises the following elements: - a first electrical connection; - a second electrical connection; - a plurality of partial resistors connected in parallel, each partial resistor being designed for a maximum power that can be supplied to the partial resistor individually; - a switching device which is designed to connect individual partial resistors of the at least two partial resistors to the first electrical connection and the second electrical connection, wherein the resistor is designed to distribute an electrical power which is supplied to the resistor via the connections as partial powers to individual partial resistors of the plurality of partial resistors by means of the switching device.

[0008] Preferably, the resistor is designed to distribute the partial powers to individual partial resistors of the plurality of partial resistors in such a way that the partial power supplied to at least one partial resistor of the plurality of partial resistors corresponds to the maximum power that can be supplied to this partial resistor or at least to the maximum power that can be supplied to this partial resistor.

[0009] Alternatively or additionally, it can be provided that the partial power supplied to the at least one partial resistor of the plurality of partial resistors is supplied by means of an electrical connection established permanently, in particular by the switching device, between the first electrical connection, the at least one partial resistor, and the second electrical connection. A "permanently established" or "permanently closed" electrical connection is to be understood as an electrical connection established by the switching device without switching operations and in particular without PWM-based operation or PWM-based operation with 100% control. Switching means of the switching device provided for controlling the at least one partial resistor are then operated permanently closed, for example.The partial power can be supplied at any time using PWM-based operation should the control requirements change. It is also possible to interrupt the supply of partial power by having the switching device interrupt the corresponding electrical connection to at least one partial resistor if the control requirements change.

[0010] Configuring the resistor according to the options described above allows for a reduction in parasitic currents, as at least one partial resistor is supplied with the maximum possible partial power and is not controlled in a switching PWM-based mode. Parasitic currents due to PWM-based power distribution to this partial resistor are thus reduced.

[0011] The maximum power that can be supplied can be a design value for the corresponding partial resistor, such as a nominal power. The nominal power then applies to a specific operating state of the resistor, i.e. at a specific electrical voltage applied to the first and second terminals, the nominal voltage, and a partial electrical current conducted through the corresponding partial resistor. If the electrical voltage applied to the first and second terminals changes, the partial power supplied to the individual partial resistor can also change. If this voltage drops because the mains voltage of the network in which the resistor is provided changes, the current intensity and thus also the power conducted through the individual partial resistor is reduced, particularly when the individual partial resistor is permanently connected to the first and second terminals.Overload operation of individual or all partial resistors is described below.

[0012] If there is no PWM-based control, i.e. the partial resistor is permanently electrically connected to the first and second terminals, the power output is influenced by the resistance value of the partial resistor and the voltage applied to the first and second terminals. The respective resistance value of the partial resistors in the warm state is designed so that no overload, especially thermal overload, of the resistor occurs when the nominal voltage is applied and, if applicable, the maximum coolant temperature. If an overload of the partial resistor is nevertheless detected, it must be completely removed from the control system or a PWM-based control system must be initiated, provided the resistor temporarily or generally does not allow overload operation as described below.

[0013] Preferably, the resistor, in particular the switching device, is designed to detect and monitor partial electrical power supplied to the individual partial resistors. The partial power can be detected and monitored, for example, by detecting and evaluating individual partial currents supplied to the partial resistors and the voltages applied to the partial resistors. For this purpose, the resistor, in particular the switching device, has appropriately designed detection means, such as current or voltage sensors.

[0014] Preferably, the resistor, in particular the switching device, is designed to detect and monitor the thermal states of individual partial resistors. The thermal states can be detected and monitored, for example, by detecting and evaluating individual partial currents supplied to the partial resistors or by evaluating the temperatures prevailing at the partial resistors. For this purpose, the resistor, in particular the switching device, has appropriately designed detection means, such as current or temperature sensors. If the resistor is liquid-cooled, as explained below, such detection means can be specifically designed to detect the coolant temperature or the coolant mass flow.

[0015] The resistor itself can be designed as a liquid-cooled resistor, with a coolant flowing through the resistor ensuring the cooling of the individual sub-resistors.

[0016] The resistor elements can be designed as plates or pairs of plates, in particular with essentially the same contour. If the resistor is liquid-cooled, coolant channels can be formed between the plates, or coolant channels can be formed through the pairs of plates. The coolant can flow through the coolant channels to cool the resistor elements.

[0017] If the partial resistors are controlled by the switching device using PWM rather than permanently closed switching means, the associated switching processes can give rise to EMC-relevant interference currents, particularly EMC-relevant current peaks, in the individual partial resistors caused by the parasitic capacitances of these partial resistors. This is particularly due to the charging and discharging processes of these capacitances caused by PWM operation. This negative effect is avoided or at least mitigated by the invention in that as many partial resistors as possible, through which partial power is conducted, are operated at their maximum deliverable power or are permanently connected to the first and second terminals, i.e., are not controlled by PWM.

[0018] Especially with a resistor that consists of plate-type resistors arranged in a stack of plates, mutual heating of the resistors, particularly due to alternating power supply to the resistors, can be avoided or reduced. Furthermore, by dividing the resistor into several resistors, the absolute switchable current is reduced, also leading to a reduction in EMC-relevant interference.

[0019] The disclosed resistor is designed in particular for use in vehicles, preferably in commercial vehicles or rail vehicles. The vehicles are capable of recuperating electrical power. This can be done via a generator-driven drive machine of the vehicle. Particularly at high battery charging voltages and low or high temperatures, the energy storage capacity is limited and the recuperated power must be converted in the resistor. Preferably, the power to be converted is >20 kW. Preferably, the power to be converted is <250 kW. Recovered electrical power that cannot be fed to an electrical energy storage device of the vehicle, such as a battery, because, for example, the battery can no longer absorb any power and / or which cannot be fed to other consumers because, for example,whose power consumption is insufficient or which are not switched on, can be passed through the resistor and converted into heat.

[0020] Preferably, the resistor is configured to distribute the partial powers among individual partial resistors of the plurality of partial resistors in such a way that the number of individual partial resistors for which the supplied partial power is below the maximum power that can be supplied to this partial resistor is minimized. This is advantageous for reducing parasitic currents. For this purpose, the partial powers are preferably distributed among the partial resistors in such a way that only one of the partial resistors to which partial power is supplied receives a partial power that is lower than its maximum power that can be supplied. Thus, EMC-relevant interference currents can only occur at this partial resistor in the parasitic capacitance of this partial resistor.

[0021] Preferably, the gradation of the maximum power delivered by the individual resistors should be chosen sensibly when designing the resistor. For this purpose, reference is made to the following sections, which discuss advantageous gradations.

[0022] If the braking resistor requires electrical power to be delivered that can be represented by the sum of the maximum power that can be delivered to certain partial resistors, the corresponding partial power can be supplied to these partial resistors. There is then no need for PWM-based distribution of partial power to one or more additional partial resistors.

[0023] Alternatively or additionally, the resistor is designed to distribute the partial powers among individual partial resistors of the plurality of partial resistors in such a way that the number of individual partial resistors for which the partial power is supplied PWM-based is minimized. This is advantageous for reducing parasitic currents. For this purpose, the partial powers are preferably distributed among the partial resistors in such a way that the corresponding partial power is supplied PWM-based by the switching device to only one partial resistor of the plurality of partial resistors. Thus, EMC-relevant interference currents can only occur at this partial resistor in the parasitic capacitance of this partial resistor. Particularly preferably, the resistor is designed such that PWM-based control does not occur, at least not in an electrically stationary state.

[0024] Preferably, the resistor is configured to distribute the partial powers among individual partial resistors of the plurality of partial resistors such that a partial power is supplied to at least two individual partial resistors that is less than the maximum power that can be supplied. The resistor is further configured to perform the switching operations with a time offset from one another when these at least two partial resistors are controlled by PWM. In this case, transient current inrush peaks occur with a time offset, so that the absolute current value of a partial resistor is not exceeded.

[0025] Preferably, the plurality of partial resistors comprises at least two partial resistors that are designed for an equally high, individually supplyable maximum power. This has the advantage that the resistor has a second partial resistor that is identical to another partial resistor in terms of power control or its electrical resistance. This results in the possibility, for example, of designing the resistor, in particular the switching device, such that a partial power that corresponds in particular to the maximum power that can be supplied to these partial resistors is supplied alternately to one and the other partial resistor. In this way, PWM-based power distribution to these partial resistors is not necessary, and thermal overload can preferably be avoided by allowing the partial resistor through which the partial power is not currently being conducted to cool down.Alternatively or additionally, this is a possibility to design the braking resistor redundantly with regard to this partial resistance or the power level embodied by this partial resistance.

[0026] Preferably, for a case where the total power supplied to the resistor is divided into discrete, smallest partial powers, for example by the switching device, the following configuration can be provided: The at least two or more partial resistors, each designed for an equal individual maximum power, can be designed to include or exclusively represent the partial resistors with the smallest maximum powers in the plurality of partial resistors. In particular, it can be provided that the maximum power that can be supplied to these at least two or more partial resistors corresponds to a smallest discrete partial power into which the total power can be divided.

[0027] This means that if the resistor is designed in such a way that the total power can be divided into discrete, smallest partial powers, then preferably a sufficient number of these partial resistors are provided whose maximum deliverable power corresponds precisely to this smallest partial power. These partial resistors can thus be used to divide the total power supplied to the resistor in such a way that the partial resistors that are supplied with partial power are fully controlled or receive their maximum deliverable power. This makes it possible to conduct each of the provided discrete power stages of the total power via the resistor or its partial resistors without PWM-based operation. In this way, the occurrence of parasitic interference currents can be avoided for each required power level.The following configuration is discussed as an example: 1 kW is assumed to be the smallest discrete partial power into which the total power is to be divided. The partial resistors are divided into partial resistors whose maximum deliverable power is an integer multiple of 4 kW. In addition, there are three partial resistors for which the maximum deliverable power is 1 kW. The total power to be supplied via the resistor, which is divided into discrete 1 kW steps (for example, by a control or data processing device of the resistor), can then be distributed among the partial resistors in such a way that the supplied partial power always corresponds to the maximum deliverable power of the corresponding partial resistor. Partial resistance no. Maximum power available [kW] possible maximum power supply [kW) 1 1 1 2 1 2 3 1 3 4 4 7 5 8 15 6 16 31 7 32 63 8 64 127 9 128 255 10 256 511

[0028] As an example, the circuit of the partial resistors with the numbers 1 to 4 is shown here, where the total power is divided into discrete 1 kW steps: Total power to the resistor [kW] Partial resistance 1max. 1 kW Partial resistance 2max. 1 kW Partial resistance 3max. 1 kW Partial resistance 4 max. 4 kW 1,0 1.0 kW 0 0 0 2,0 1.0 kW 1.0 kW 0 0 3,0 1.0 kW 1.0 kW 1.0 kW 0 4,0 0 0 0 4.0 kW 5,0 1.0 kW 0 0 4.0 kW 6,0 1.0 kW 1.0 kW 0 4.0 kW 7,0 1.0 kW 1.0 kW 1.0 kW 4.0 kW

[0029] Resistors 1 to 3 serve as a bridge, so to speak, to represent the discrete power levels, which cannot be represented as integer multiples of 4 kW. This is independent of whether the maximum power delivered by the individual resistors numbered 4 and higher is the same per resistor or whether, as in the example above, this maximum power delivered per resistor is doubled.

[0030] Preferably, the subdivision of the smallest partial resistances in this case is as follows: Minimum number of partial resistors with the smallest maximum power supply = (second smallest maximum power supply of a partial resistor) / (smallest discrete partial power) − 1

[0031] Additional aspects can be taken into account when making the subdivision. The above assumption applies under the assumption that the resistance value of the partial resistors does not change when heated.

[0032] Preferably, the plurality of partial resistors comprises at least two partial resistors that are designed for different, individually deliverable maximum power levels. In this way, the partial resistors can be selected as needed. In particular, the resistor can be configured to distribute the partial power levels among the partial resistors in such a way that at least one of the partial resistors is supplied with a partial power level that corresponds to the deliverable maximum power of this partial resistor as often as possible.

[0033] Preferably, the plurality of partial resistors comprises at least two partial resistors whose individually deliverable maximum powers differ by a factor of two. Particularly preferably, partial resistors ranging from a partial resistor with the lowest deliverable maximum power to a partial resistor with the highest deliverable maximum power are included in the plurality of partial resistors according to this gradation. In particular, it can be provided that the plurality of partial resistors exclusively comprise partial resistors that correspond to this gradation. This allows for flexible combination of individual partial resistors or flexible distribution of the electrical power conducted via the resistor into corresponding partial powers.

[0034] The following table shows an example of such a gradation: Partial resistance no. Maximum power available [kW] possible maximum power supply [kW) 1 1 1 2 2 3 3 4 7 4 8 15 5 16 31 6 32 63 7 64 127 8 128 255 9 256 511 10 512 1023

[0035] This makes it clear that for power outputs of maximum / kW only the partial resistors with the numbers 1, 2 and 3 need to be selected.

[0036] One possibility to control the partial resistors, whereby as few of the controlled partial resistors as possible should be controlled by PWM-based control, as mentioned above, can be done, for example, for the total power supplied via the resistor as follows: Total power to the resistor [kW] Partial resistance 1max. 1 kW Partial resistance 2max. 2 kW Partial resistance 3 max. 4 kW 0,5 0.5 kW (PWM) 0 0 1,0 1.0 kW 0 0 1,5 1.0 kW 0.5 kW (PWM) 0 2,0 0 2 kW 0 2,5 0.5 kW (PWM) 2 kW 0 3,0 1.0 kW 2 kW 0 3,5 1.0 kW 2 kW 0.5 kW (PWM) 4,0 0 0 4 kW 4,5 0.5 kW (PWM) 0 4 kW 5,0 1.0 kW 0 4 kW 5,5 1.0 kW 0.5 kW (PWM) 4 kW 6,0 0 2 kW 4 kW 6,5 0.5 (PWM) 2 kW 4 kW 7,0 1.0 kW 2 kW 4 kW Each power value with the suffix "PWM" in parentheses means that this partial resistor in this case receives a partial power that is controlled via PWM. This means that the corresponding partial resistor is not supplied with the maximum power that can be supplied. In this case, losses or high current inputs occur at this partial resistor due to the parasitic capacitance of the partial resistors. A power value of 0 means that in this case no partial power is fed through the corresponding partial resistor. This example makes it clear that with this type of staggering of the partial resistors for the overall power range shown, only a maximum of one partial resistor or even no partial resistor at all (for total powers of 1.0 kW, 2 kW, 3.5 kW, 4 kW, 5 kW, 6 kW and 7 kW) needs to be controlled via PWM, which greatly reduces the high current inputs.

[0037] Preferably, it can be provided that all partial resistors are designed for an equally high, individually deliverable maximum power. Such an equidistant staggering of the partial resistors with regard to the maximum deliverable power has the advantage that the resistor, in particular the switching device, can be designed such that different partial resistors can be controlled while the total power to be conducted through the resistor remains constant, or that it is possible to switch to other partial resistors while the total power remains constant. For example, if a partial resistor is in a thermally critical state, the control or supply of the partial power can be terminated and instead supplied to another partial resistor.

[0038] Such a gradation is as follows for partial resistors with a supply power of 2 kW: Partial resistance no. Maximum power available [kW] possible maximum power supply [kW] 1 2 2 2 2 4 3 2 6 4 2 8 5 2 10 6 2 12 7 2 14 8 2 16 9 2 18 10 2 20

[0039] For example, the control of the partial resistors can be designed as follows for the total power range from 0.5 kW to 7 kW: Total power to the resistor [kW] Partial resistance 1 max. 2 kW Partial resistance 2max. 2 kW Partial resistance 3max. 2 kW Partial resistance 4max. 2 kW 0,5 0.5 kW (PWM) 0 0 0 1,0 1.0 kW (PWM) 0 0 0 1,5 1.5 kW (PWM) 0 0 0 2,0 2.0 kW 0 0 0 2,5 2.0 kW 0.5 kW (PWM) 0 0 3,0 2.0 kW 1.0 kW (PWM) 0 0 3,5 2.0 kW 1,5 kW (PWM) 0 0 4,0 2,0 kW 2,0 kW 0 0 4,5 2,0 kW 2,0 kW 0,5 kW (PWM) 0 5,0 2,0 kW 2,0 kW 1,0 kW (PWM) 0 5,5 2,0 kW 2,0 kW 1,5 kW (PWM) 0 6,0 2,0 kW 2,0 kW 2,0 kW 0 6,5 2,0 kW 2,0 kW 2,0 kW 0,5 kW (PWM) 7,0 2,0 kW 2,0 kW 2,0 kW 1,0 kW (PWM)

[0040] Compared to the previously discussed gradation, it becomes clear here that although only the partial resistor with No. 1 is required for the lower total power up to 2 kW, this must be kept in PWM operation until the 2 kW of supplied partial power is reached, which has a detrimental effect on the resulting high current inputs due to the parasitic capacitances.

[0041] Preferably, the resistor is designed to alternately supply a partial power, particularly by means of the switching device, to the at least two partial resistors, which are designed for an identical, individually supplyable maximum power. Such an alternation is advantageous if excessive heating of an individual partial resistor is to be avoided. For example, with the same total power supplied via the resistor, the partial power supplied to a first partial resistor can then be supplied to a second partial resistor with the same supplyable maximum power through the alternation. In this way, the first partial resistor, which is now preferably supplied with a lower or, more preferably, no partial power at all, can cool down again.The change can be designed in such a way that both partial resistors do not exceed a predetermined temperature or a predetermined average power input into the respective partial resistor.

[0042] Preferably, the change in the supply of partial power to the at least two partial resistors takes place according to a predetermined switching pattern, in particular by the switching device. The predetermined switching pattern can, for example, be designed such that, as described above for two partial resistors, individual partial resistors do not exceed a predetermined temperature or a predetermined average power input into the respective partial resistor. The change can take place between two or more partial resistors. Preferably, such a switching pattern is already defined when the resistor is designed. It is then present in the resistor, in particular in the switching device, as a control pattern. An adaptation of the switching pattern due to changing thermal, power-based, or current-based boundary conditions in the resistor is conceivable. The boundary conditions can, for example, be recorded and evaluated using the aforementioned recording means.For example, it is then possible to switch to a different switching scheme, which is also stored in the resistor, in particular in the switching device.

[0043] Alternatively or additionally, the resistor is designed so that the changeover during the supply of partial power to the at least two partial resistors takes place in a controlled manner, in particular by the switching device, wherein the control is particularly thermally based, power based, or current based. By means of appropriately designed detection means, such as those mentioned above, it is possible to detect the state of a first partial resistor (e.g., temperature, power, current). If this is in a particularly critical state, which can be defined in advance, the changeover can take place to a second partial resistor, to which, for example, no partial power was supplied before the changeover or which, for example, had a more favorable state (e.g., temperature, power, current) compared to the first partial resistor. The controlled changeover can be applied in such a way that the above-mentioned switching scheme is overridden. This meansThat the controlled change takes precedence over the switching pattern, and the switching pattern is not further executed during a controlled change. Furthermore, resistor designs are conceivable that do not have the above-mentioned switching pattern and are designed only to perform the controlled change.

[0044] Further aspects of the resistor described above are described below. The design of the switching device will now be discussed.

[0045] The switching device preferably has a plurality of switching means, wherein individual switching means from the plurality of switching means are assigned to individual partial resistors and are designed to connect the respective partial resistor to the first terminal and the second terminal, such that the electrical connection from the first terminal to the second terminal exists via the respective partial resistor. In this case, it can be provided that several switching means of the plurality of switching means are connected in series together with the resistor assigned to them, such that the electrical connection between the first terminal and the second terminal only exists when all of these switching means assume a closed state, i.e. establish their respective partial connection. Alternatively, it can be provided that individual switching means assigned to the respective partial resistor are connected in parallel to one another.Then, the establishment of the electrical connection between the first terminal and the second terminal is possible via individual branches of the parallel circuit of switching means, regardless of the switching state of the other switching means provided in other branches of the parallel circuit.

[0046] The switching means themselves can be designed as power semiconductors (e.g. IGBTs or MOSFETs based on silicon carbide technology), particularly those suitable for industrial use.

[0047] The switching means can be designed to control the associated partial resistors using PWM. A permanent electrical connection can be established by permanently closing the corresponding switching means. The electrical connection can be interrupted by opening appropriately arranged switching means.

[0048] Preferably, the resistor, in particular the switching device, is designed to detect and monitor partial electrical power supplied to the individual switching means. The partial power can be detected and monitored, for example, by detecting and evaluating individual partial currents supplied to the switching means, voltages applied to the switching means, and / or switching cycles performed by the switching means, or switching frequencies applied to the switching means. For this purpose, the resistor, in particular the switching device, has appropriately designed detection means.

[0049] Preferably, the resistor, in particular the switching device, is designed to detect and monitor thermal states of individual switching devices. The thermal states can be detected and monitored, for example, by detecting and evaluating individual partial currents supplied to the switching devices, temperatures prevailing at the partial resistors, and / or switching cycles performed by the switching devices or switching frequencies applied to the switching devices. For this purpose, the resistor, in particular the switching device, has appropriately designed detection means.

[0050] Preferably, at least two switching means are assigned to an individual partial resistor, so that the electrical connection of the individual partial resistor from the first terminal to the second terminal can be made via an assigned switching means or via the at least two assigned switching means, wherein the resistor is designed to alternately control the switching means assigned to the individual partial resistor.

[0051] Assigning at least two switching devices to a partial resistor allows for a protected control option for this partial resistor. If the switching devices are connected in series with the resistor (e.g. one switching device before and one switching device after the partial resistor or both switching devices before and after the partial resistor), a first switching device can take over the actual control of the partial resistor or supply the partial power to the partial resistor by controlling it using PWM or by being permanently closed or open as required, while the second switching device is closed. In the event that the first switching device fails, the second switching device is designed to interrupt the series connection. In the event of such a failure, the first switching device remains, for example, in a closed position that can no longer be controlled.This avoids the risk of uncontrolled operation of the resistor or damage to the resistor.

[0052] Irrespective of the above considerations regarding protection, the arrangements of the switching means described above can be controlled alternately. The change in the control of the switching means assigned to the individual partial resistor can take place according to a predetermined switching pattern, in particular by the switching device. The predetermined switching pattern can, for example, be designed such that individual switching means assigned to a partial resistor do not exceed a predetermined temperature or a predetermined average power input into the respective switching means. The change can take place between two or more switching means assigned to the respective partial resistor. Preferably, such a switching pattern is already defined when the resistor is designed. It is then present in the resistor, in particular in the switching device, as a control pattern.Adapting the circuit pattern due to changing thermal, power-based, or current-based boundary conditions in the resistor, particularly in the switching devices, is conceivable. The boundary conditions can be recorded and evaluated, for example, using the aforementioned recording devices. For example, a switch can then be made to a different circuit pattern that is also stored in the resistor, particularly in the switching device.

[0053] Preferably, the predetermined switching pattern is designed such that switching occurs at regular time intervals between the switching means assigned to a partial resistor, in particular when the partial power is supplied to the individual partial resistor via the assigned switching means, wherein the supplied partial power is less than the maximum power that can be supplied to the individual partial resistor. In this case, the partial power would be supplied using PWM, which, due to the associated switching operations, causes an increased heat input into the respective switching means compared to a permanently closed position, so that excessive heating due to regular switching can be avoided. The switching pattern provided for this purpose and the time intervals required for this can be determined during the design of the resistor.

[0054] Alternatively or additionally, the resistor is designed so that the change in the control of the switching means assigned to the individual partial resistor takes place in a controlled manner, in particular by the switching device, wherein the control is particularly thermally based, power-based, or current-based. Appropriately designed detection means, such as those mentioned above, enable detection of the state of a first switching means (e.g., temperature, power, current). If this is in a particularly critical state, which can be defined in advance, the change can take place to a second switching means which, prior to the change, was, for example, permanently closed or permanently open, or which, prior to the change, had a more favorable state (e.g., temperature, power, current) compared to the first partial resistor. The controlled change can be applied in such a way that the above-mentioned switching pattern is overridden. This meansThat the controlled change takes precedence over the switching pattern, and the switching pattern is not further executed during a controlled change. Furthermore, resistor designs are conceivable that do not have the above-mentioned switching pattern and are designed only to perform the controlled change.

[0055] Preferably, switching means arranged directly adjacent to one another in the plurality of switching means are assigned to partial resistors from the plurality of partial resistors whose maximum power delivery differs. In this way, heat transfer from switching means assigned to the same partial resistor can be reduced or completely avoided.

[0056] Preferably, the resistor is designed to perform the change in the control of the switching means assigned to the individual partial resistor in such a way that a switching means, particularly thermally critical, which supplies the partial power to the individual partial resistor via PWM control, is switched to a conducting position or is switched off, and another switching means assigned to the individual partial resistor takes over the supply of the partial power to the partial resistor via PWM control. In this way, heating of the switching means can be prevented by regularly changing the switching means.

[0057] The resistor is preferably designed to carry out overload operation of individual partial resistors. In particular when such a partial resistor is fully controlled, i.e. there is a permanently closed electrical connection to this partial resistor and no PWM-based control or supply of the partial power to this partial resistor is carried out. If the mains voltage is equal to or higher than the nominal voltage on which the maximum power that can be supplied or the rated power is based, then, with an otherwise constant or increasing current flowing through the partial resistor, the corresponding partial resistor can be overloaded, in which more than the maximum power that can be supplied is conducted through the partial resistor. The resistor and in particular the switching device are then preferably designed to monitor this overload operation.If the state of the corresponding partial resistor or other partial resistors that experience thermal power input due to this partial resistor in overload operation is in a predetermined cut-off state, the electrical current flowing through this partial resistor, in particular through the switching device, is reduced by supplying the partial power via PWM-based control and no longer via a permanently closed electrical connection. Overload operation can be intended or useful in particular when power is to be supplied via the resistor that cannot be adequately represented by grading the maximum power that can be supplied to the individual partial resistors. The state of the corresponding partial resistor can be detected in particular by the detection means mentioned above.If the resistor is liquid-cooled, a detection means can be provided in particular which is designed to detect the state of the partial resistor via the coolant temperature, in particular in the flow direction behind the partial resistor.

[0058] Preferably, the resistor is designed to permanently connect all of the partial resistors to the first and second terminals when an electrical voltage that is lower than the nominal voltage of the resistor is applied to the first and second terminals. This means that all of the partial resistors are connected in parallel and connected to the first and second terminals without any PWM-based switching. At such low electrical voltages, a reduced power is then supplied to the partial resistors, which is below the thermally possible. Depending on the lower voltage range, there is a reduced power output from the plurality of partial resistors, but this is not a problem because the increased power requirement only occurs at higher voltages or at voltages equal to or greater than the nominal voltage of the resistor.

[0059] The invention is described in more detail below with reference to the accompanying drawings.

[0060] They show: Fig. 1 a general configuration of a resistor, Fig. 2a a first possible arrangement of switching means and a proposal to control them, Fig. 2b a second possible arrangement of switching devices and a proposal to control them, Fig. 3a a first possible connection of switching means with a partial resistor, Fig. 3b shows a second possible connection of switching devices with partial resistors.

[0061] Fig. Figure 1 shows a general configuration of a resistor.

[0062] Shown is an electrical resistor 1, specifically an electrical braking resistor. Resistor 1 comprises the following elements: - a first electrical connection 3; - a second electrical connection 4; - a plurality of partial resistors 2 connected in parallel, each partial resistor 2.1, 2.2, ..., 2.n being designed for a maximum power that can be supplied individually to the partial resistor 2.1, 2.2, ..., 2.n; - a switching device 5, which is designed to connect individual partial resistors 2.1, 2.2, ...2.n of the at least two partial resistors 2, to the first electrical connection 3 and the second electrical connection 4, wherein the resistor 1 is designed to distribute an electrical power, which is supplied to the resistor 1 via the connections 3, 4, by means of the switching device 5 as partial powers to individual partial resistors 2.1, 2.2, ...2.n of the plurality of partial resistors 2.

[0063] In the illustration shown, the switching device 5 has a plurality of switching elements 6, which comprise individual switching elements 6.1, 6.2, ...6.n. The switching elements 6.1, 6.2, ...6.n themselves can be designed as power semiconductors (e.g., IGBTs or MOSFETs based on silicon carbide technology), particularly those suitable for industrial use.

[0064] The individual switching devices 6.1, 6.2, ...6.n are arranged here, starting from the first electrical connection 3 and extending to the second electrical connection 4, behind the individual partial resistors 2.1, 2.2, ...2.n. However, this is merely an example. A skilled person can deduce from this arrangement of the individual switching devices 6.1, 6.2, ...6.n that an arrangement of individual switching devices 6.1, 6.2, ...6.n or all switching devices 6.1, 6.2, ...6.n upstream of the individual partial resistors 2.1, 2.2, ...2.n is also possible. Likewise, individual switching devices 6.1, 6.2, ...6.n can be arranged upstream of, and individual switching devices 6.1, 6.2, ...6.n downstream of, their assigned partial resistors 2.1, 2.2, ...2.n. It is also possible that one or all of the partial resistors 2.1, 2.2, ...2.n are assigned more than one individual switching device 6.1, 6.2, ...6.n. An example is the Fig. 3a. If several switching devices 6.1, 6.2, ...6.n are located in one branch of the parallel circuit shown, i.e., if several switching devices 6.1, 6.2, ...6.n are assigned to a single partial resistor 2.1, 2.2, ...2.n, these can all be arranged upstream or downstream of the respective partial resistor 2.1, 2.2, ...2.n, starting from the first electrical connection 3 to the second electrical connection 4, or individual switching devices 6.1, 6.2, ...6.n can be arranged upstream and individual switching devices 6.1, 6.2, ...6.n can be arranged downstream of the respective partial resistor 2.1, 2.2, ...2.n.

[0065] The switching device 5 may comprise an electronic data processing means (not shown) for receiving data from detection means (not shown, e.g. as described above), such as current, voltage and / or temperature sensors, in order to be able to detect, analyze or monitor states of individual partial resistors 2.1, 2.2, ...2.n and / or states of individual switching means 6.1, 6.2, ...6.n.

[0066] The switching device 5 can have an electronic control means (not shown) for controlling the individual switching means 6.1, 6.2, ... 6.n. In particular, the individual switching means 6.1, 6.2, ... 6.n can be selectively controlled and maintained permanently open, permanently closed, or in PWM-based operation.

[0067] The switching device 5 can be designed in particular to control the individual switching means 6.1, 6.2, ... 6.n according to a switching scheme that is previously stored in the switching device 5. Examples of switching schemes are shown in the Fig. 2a and Fig. 2b discussed.

[0068] In addition, the switching device 5 can be configured to perform a controlled activation of the individual switching means 6.1, 6.2, ... 6.n. This can, as described above, be based on the data from the detection means and can be carried out in such a way that any existing switching scheme is overridden.

[0069] The functionality of the resistor 1 shown is as follows: Resistor 1 is designed to convert electrical power, which is generated, for example, during recuperation of an electric vehicle and which cannot be used for any other purpose (e.g., because an electrical storage device can no longer store energy or because no other consumer of the vehicle can absorb any more power), into heat. In this case, resistor 1 is a braking resistor. To dissipate the heat generated at the individual partial resistors 2.1, 2.2 ..., 2.n from the supplied electrical power, resistor 1 can be connected to a cooling circuit (not shown). This cooling circuit can, in particular, be designed such that it has channels (not shown) that run through individual partial resistors 2.1, 2.2 ..., 2.n. Coolant can be conducted through these channels to dissipate the resulting heat.

[0070] The total power to be converted into heat is supplied to resistor 1, which is connected to the first terminal 3 and the second terminal 4 in a circuit with the recuperative source, as an electrical current via these terminals 3, 4. The switching device 5 is designed to analyze the supplied and converted total power and to distribute it as partial power to the partial resistors 2.1, 2.2, ...2.n by controlling the individual switching means 6.1, 6.2, ..., 6.n accordingly.

[0071] Preferably, the switching device 5 is designed to distribute the partial powers to individual partial resistors 2.1, 2.2, ...2.n of the plurality of partial resistors 2 such that the partial power supplied to at least one partial resistor 2.1, 2.2, ...2.n of the plurality of partial resistors 2 corresponds to the maximum power that can be supplied to this partial resistor 2.1, 2.2, ...2.n.

[0072] This resistor configuration allows for a reduction in parasitic currents, as the maximum possible power is supplied to at least one partial resistor. Parasitic currents due to PWM-based power distribution to this partial resistor are thus reduced.

[0073] Preferably, the switching device 5 is designed to control the switching means 6.1, 6.2, ..., 6.n such that all switching means 6.1, 6.2, ..., 6.n are either closed or open, wherein a maximum of one switching means 6.1, 6.2, ..., 6.n is in PWM-based operation.

[0074] Below are the Fig. 2a, Fig. 2b, Fig. 3a and Fig. 3b shows individual partial resistors and individual switching devices. Their reference symbols do not necessarily refer to the partial resistors 2.1, 2.2, ...2.n and the switching devices 6.1, 6.2, ..., 6.n, which are shown in Fig. 1 are shown.

[0075] Fig. Figure 2a shows a first possible arrangement of switching devices and a proposal for controlling them.

[0076] Shown is a plan view of a plurality of switching elements 6 arranged in a 3x3 matrix. In this arrangement, several switching elements 6.1, 6.2, ..., 6.9 are directly adjacent. Heat transfer by thermal radiation or thermal conduction (e.g., if individual switching elements 6.1, 6.2, ..., 6.9 are arranged on the same base plate) from one switching element 6.1, 6.2, ..., 6.9 to an adjacent one is possible here. In particular, the switching element 6.5, which is arranged in the center position of this matrix, can receive heat input from each of the surrounding switching elements 6.1, 6.2, 6.3, 6.4, 6.6, 6.7, 6.8, 6.9.

[0077] In order to optimize heat generation and heat distribution within the plurality of switching devices 6, the individual switching devices 6.1, 6.2, 6.3, 6.4, 6.6, 6.7, 6.8, 6.9 can be controlled in a rotating manner. This is indicated by the arrows shown. The straight arrow shows a jump from switching device 6.1 to switching device 6.9 if, for example, switching device 6.1 has reached a particularly thermally critical state due to PWM-based control, which triggers a change. The furthest-away switching device 6.9 is then controlled. This allows switching device 6.1 to cool down due to the relatively large distance between these switching devices 6.1, 6.9, while switching device 6.9 is now controlled PWM-based. If switching device 6.9 reaches a state that requires a change, a rotation in the control can occur, indicated by the round arrow. This means that switching device 6 is no longer used.1 but instead to switching element 6.2, which is then controlled using PWM. This results in a control sequence within the switching elements that can be as follows: 1. Switching devices 6.1 2. Switching devices 6.9 3. Switching devices 6.2 4. Switching devices 6.8 5. Switching devices 6.3 6. Switching devices 6.7 7. Switching devices 6.6 8. Switching devices 6.4

[0078] Switching device 6.5 can be omitted here and only controlled PWM-based when the other switching devices 6.1, 6.2, 6.3, 6.4, 6.6, 6.7, 6.8, 6.9 are open.

[0079] The switching sequence discussed here is advantageous when all switching means 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9 are assigned to partial resistors that have an equally high maximum power that can be supplied.

[0080] Fig. 2b shows a second possible arrangement of switching devices and a proposal for controlling them.

[0081] This shows a plurality of switching devices 6, comprising eight switching devices 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, and 6.8. A circuit diagram is also indicated by the straight arrows. Here, switching devices 6.1 and 6.6, as well as 6.3 and 6.8, are each assigned to a single resistor element of the resistor. If switching device 6.1 becomes thermally critical due to PWM-based operation, switching device 6.6 is switched over, which then controls the supply of the partial power to the same resistor element, allowing switching device 6.1 to cool down. The same applies to switching devices 6.3 and 6.8.

[0082] Fig. Figure 3a shows a first possible connection of switching devices with a partial resistor.

[0083] A partial resistor 2.1 is shown, which is arranged between a first switching device 6.1 and a second switching device 6.2. This is therefore a series circuit of partial resistor 2.1 and switching devices 6.1, 6.2.

[0084] If both switching devices 6.1, 6.2 are closed, an electrical connection exists between the first terminal 3 and the second terminal 4 via this partial resistor 2.1. Electrical power, in particular a partial power supplied to the resistor not shown here, can then be conducted via the partial resistor 2.1 and converted into heat.

[0085] The design shown here enables, on the one hand, a secure control of the partial resistor 2.1 in that, for example, the second switching means 6.2 is permanently closed and the supply of the partial power or control of the partial resistor 2.1 is carried out solely by the first switching means 6.1. This can be closed, open, or in PWM-based operation. If the first switching means 6.1 fails, it can change to a permanently closed position. It then establishes a permanent and no longer controllable connection. In this case, the resistor in which the partial resistor 2.1 is provided or the switching device of the resistor is designed such that the second switching means 6.2 is now permanently opened. As a result, the branch in which the partial resistor 2.1 shown here is arranged is permanently interrupted. A further supply of partial power to the partial resistor 2.1 is then no longer carried out. The second switching means 6.1 can therefore2 can be used to deactivate this partial resistor 2.1 or the branch shown here.

[0086] The switching means 6.1, 6.2 can also be designed in reverse, so that the first switching means 6.1 is permanently closed and is permanently opened in case of failure of the second switching means 6.2.

[0087] The configuration shown also allows, as an alternative or in addition to this protection, a switchover between the two switching devices 6.1, 6.2 if one switching device has a particularly critical state or a switching pattern specifies a switchover. When the PWM-based control of the first switching device 6.1 changes, the second switching device 6.2 switches to a closed position and vice versa. This, of course, assumes that both switching devices 6.1, 6.2 are functional.

[0088] Fig. 3b shows a second possible connection of switching devices with partial resistors.

[0089] Here, two partial resistors 2.1 and 2.2 are shown in parallel, with each branch of the parallel circuit having a switching device 6.1 and 6.2. The partial resistors 2.1 and 2.2 are identically designed and have the same maximum power rating.

[0090] An electrical connection between the first terminal 3 and the second terminal 4 can be established by closing the first switching means 6.1 via the first partial resistor 2.1. A further electrical connection between the first terminal 3 and the second terminal 4 can be established by closing the second switching means 6.2 via the second partial resistor 2.2.

[0091] If the first switching device 6.1 is in PWM-based operation, this operation can be continued by switching to the second switching device 6.2. The other switching device 6.1, 6.2 then moves to a closed or open position as required. Thus, the total resistance between the first terminal 3 and the second terminal 4 remains unchanged. LIST OF REFERENCE SYMBOLS 1 electrical resistance 2 Variety of partial resistors 2.1-2.n partial resistance 3 first connection 4 second connection 5 Switching device 6 Variety of switching devices 6.1-6.n Switching devices

Claims

[1] Electrical resistor (1), in particular electrical braking resistor, comprising: - a first electrical connection (3); - a second electrical connection (4); - a plurality of partial resistors (2) connected in parallel, each partial resistor (2.1, 2.2, ..., 2.n) being designed for a maximum power that can be supplied individually to the partial resistor (2.1, 2.2, ..., 2.n); - a switching device (5) which is designed to connect individual partial resistors (2.1, 2.2, ...2.n) of the at least two partial resistors (2) to the first electrical connection (3) and the second electrical connection (4), wherein the resistor (1) is designed to distribute an electrical power, which is supplied to the resistor (1) via the terminals (3, 4), by means of the switching device (5) as partial power to individual partial resistors (2.1, 2.2, ...2.n) of the plurality of partial resistors (2), that the partial power supplied to at least one partial resistor (2.1, 2.2, ...2.n) of the plurality of partial resistors (2) corresponds at least to the maximum power that can be supplied to this partial resistor (2.1, 2.2, ...2.n) or that the partial power which is supplied to the at least one partial resistor (2.1, 2.2, ...2.n) of the plurality of partial resistors (2) is supplied by means of an electrical connection, which is permanently established by the switching device (5), between the first electrical connection (3), the at least one partial resistor (2.1, 2.2, ...2.n) and the second electrical connection (4). [2] Resistor (1) according to claim 1, wherein the resistor (1) is designed to distribute the partial powers to individual partial resistors (2.1, 2.2, ...2.n) of the plurality of partial resistors (2) in such a way that a number of individual partial resistors (2.1, 2.2, ...2.n) is minimized in which the supplied partial power is below the maximum power that can be supplied to this partial resistor (2.1, 2.2, ...2.n) or that a number of individual partial resistors (2.1, 2.2, ...2.n) is minimized in which the supply of the partial power is PWM-based. [3] Resistor (1) according to one of the preceding claims, wherein the resistor (1) is designed to distribute the partial powers to individual partial resistors (2.1, 2.2, ...2.n) of the plurality of partial resistors (2) in such a way that a partial power which is lower than the maximum power which can be supplied is supplied to at least two individual partial resistors (2.1, 2.2, ...2.n), wherein the resistor (1) is further designed to carry out the switching operations with a time offset from one another when these at least two partial resistors (2.1, 2.2, ...2.n) are controlled by PWM. [4] Resistor (1) according to one of the preceding claims, wherein the plurality of partial resistors (2) comprises at least two partial resistors (2.1, 2.2, ..., 2.n) which are designed for an equally high individually supplyable maximum power. [5] Resistor (1) according to one of the preceding claims 1 to 3, wherein the plurality of partial resistors (2) comprises at least two partial resistors (2.1, 2.2, ..., 2.n) which are designed for a different individually supplyable maximum power. [6] Resistor (1) according to one of the preceding claims 1 to 3 and / or 5, wherein the plurality of partial resistors (2) comprises at least two partial resistors (2.1, 2.2, ..., 2.n) whose individually deliverable maximum powers differ by a factor of two. [7] Resistor (1) according to one of the preceding claims 1 to 4, wherein all partial resistors (2.1, 2.2, ..., 2.n) are designed for an equally high individually supplyable maximum power. [8] Resistor (1) according to claim 4 and one of claims 1 to 3 and 5 to 7, wherein the resistor (1) is designed to supply a partial power alternately by means of the switching device (5) to the at least two partial resistors (2.1, 2.2, ..., 2.n) which are designed for an identical individually supplyable maximum power. [9] Resistor (1) according to claim 8, wherein the change in the supply of the partial power to the at least two partial resistors (2.1, 2.2, ..., 2.n) is carried out by the switching device (5) according to a predetermined switching pattern. [10] Resistor (1) according to claim 8 or 9, wherein the resistor (1) is designed such that the change in the supply of the partial power to the at least two partial resistors (2.1, 2.2, ..., 2.n) is controlled by the switching device (5), wherein the control is in particular thermally based, power based or current based. [11] Resistor (1) according to one of the preceding claims, wherein the switching device (5) has a plurality of switching means (6), wherein individual switching means (6.1, 6.2, ... 6.n) from the plurality of switching means (6) are assigned to individual partial resistors (2.1, 2.2, ...2.n) and are designed to connect the respective partial resistor (2.1, 2.2, ...2.n) to the first terminal (3) and the second terminal (4), so that the electrical connection from the first terminal (3) to the second terminal (4) exists via the respective partial resistor (2.1, 2.2, ...2.n). [12] Resistor (1) according to claim 11, wherein at least two switching means (6.1, 6.2, ... 6.n) are assigned to an individual partial resistor (2.1, 2.2, ...2.n), so that the electrical connection of the individual partial resistor (2.1, 2.2, ...2.n) from the first terminal (3) to the second terminal (4) can be made via an assigned switching means (6.1, 6.2, ... 6.n) or via the at least two assigned switching means (6.1, 6.2, ... 6.n), wherein the resistor (1) is designed to alternately control the switching means (6.1, 6.2, ... 6.n) assigned to the individual partial resistor (2.1, 2.2, ...2.n). [13] Resistor (1) according to claim 12, wherein the change in the control of the switching means (6.1, 6.2, ... 6.n) assigned to the individual partial resistor (2.1, 2.2, ...2.n) is carried out by the switching device (5) according to a predetermined switching pattern. [14] Resistor (1) according to claim 13, wherein the predetermined switching pattern is designed such that switching between the associated switching means (6.1, 6.2, ... 6.n) is carried out at regular time intervals, in particular when the partial power is supplied to the individual partial resistor (2.1, 2.2, ...2.n) via the associated switching means (6.1, 6.2, ...6.n), wherein the supplied partial power is less than the maximum power that can be supplied to the individual partial resistor (2.1, 2.2, ...2.n). [15] Resistor (1) according to one of claims 8 to 14, wherein the resistor (1) is designed such that the change in the control of the switching means (6.1, 6.2, ... 6.n) assigned to the individual partial resistor (2.1, 2.2, ...2.n) is controlled by the switching device (5), wherein the control is in particular thermally based, power-based or current-based. [16] Resistor (1) according to one of claims 8 to 15, wherein in the plurality of switching means (6) directly adjacently arranged switching means (6.1, 6.2, ... 6.n) are assigned to partial resistors (2.1, 2.2, ...2.n) from the plurality of partial resistors (2) whose supplyable maximum power is different. [17] Resistor (1) according to one of claims 12 to 16, wherein the resistor (1) is designed to carry out the change in the control of the switching means (6.1, 6.2, ... 6.n) assigned to the individual partial resistor (2.1, 2.2, ...2.n) in such a way that a, in particular thermally critical, switching means (6.1, 6.2, ... 6.n), which supplies the partial power by means of PWM control to the individual partial resistor (2.1, 2.2, ...2.n), is switched to a through position or is switched off, and another switching means (6.1, 6.2, ... 6.n) assigned to the individual partial resistor (2.1, 2.2, ...2.n) takes over the supply of the partial power by means of PWM control to the partial resistor (2.1, 2.2, ...2.n). [18] Resistor (1) according to one of the preceding claims, wherein the resistor (1) is designed to carry out an overload operation of individual partial resistors.

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