DE102022133875A1 - Limiting the voltage in recuperation mode - Google Patents

Abstract

A recuperation circuit (12) with two connecting lines (10a,b) and a self-switching diode arrangement (22) and switchable resistance arrangement (26) connected thereto contains a control device (32) which, in a recuperation mode (RB), switches the resistance arrangement (26) on with a clock ratio (T1,2) from a first limit voltage (UG1) less than the threshold voltage (US) of the diode arrangement (22) between the connecting lines (10a,b) and otherwise switches it off.A control device (8) contains the recuperation circuit (12) and an inverter (16) and/or a direct current link (18).A drive arrangement (2) contains the recuperation circuit (12) or the control device (8) and a feed module (4) and a motor module (6), which are connected to one another by the two connecting lines (10a,b).In one method, the resistance arrangement (26) is always switched off in the drive mode (AB), and in the Recuperation mode (RB) only switches on from the first limit voltage (UG1) with the duty cycle (Ta,2).

Description

The invention relates to electrical drive arrangements that can be operated in a recuperation mode. In such a mode, electrical power from a motor module is fed back into a power supply module. Since voltages can occur in a recuperation mode that are higher than the voltages in drive mode (power from the power supply module to the motor module), protection against such overvoltages must be implemented, in particular to protect the power supply module or an intermediate intermediate circuit from such overvoltages.

It is known from practice that suppressor diodes can be used. Suppressor diodes become conductive when a component-specific voltage is exceeded. These suppressor diodes limit the voltage above a certain value, e.g. 60 V.

It is also known in practice to use a braking resistor in frequency converters to limit the voltage when these are included in drive arrangements. In this case, a switch is installed in series with a braking resistor parallel to the intermediate circuit. When the switch is closed, energy is converted into heat at the braking resistor. Opening and closing the switch decides how much energy is destroyed. This limits the intermediate circuit voltage.

The object of the present invention is to provide improvements with regard to the limitation of the voltage in recuperation mode.

The object is achieved by a recuperation circuit according to patent claim 1. Preferred or advantageous embodiments of the invention and other categories of invention emerge from the further claims, the following description and the attached figures.

The recuperation circuit is one for an electric drive arrangement. In other words, the recuperation circuit is installed, connected and operated in the electric drive arrangement as intended. “As intended” means that the recuperation circuit is structurally matched to a specific or a specific type of drive arrangement and is set up for use there; e.g. it is designed for the electrical requirements determined by this, etc. In other words, a particular drive arrangement is assumed to be known in terms of its properties, etc.

In this sense, the following drive arrangement is assumed: the drive arrangement contains a supply module and a motor module. The drive arrangement can be operated in a drive mode. In this mode, electrical power is supplied from the supply module to the motor module in order to operate a motor in the motor module. Alternatively, the drive arrangement can be operated in a recuperation mode. In this mode, electrical energy is generated in the motor module/motor and supplied (in the opposite direction to the drive mode) from the motor module to the intermediate circuit module.

The recuperation circuit contains at least one respective section of two connecting lines. These are used or are set up for the actual electrical connection between the power module and the motor module. Each of the connecting lines therefore represents a single-pole connection between the power module and the motor module. For example, the first connecting line carries a supply voltage during operation and the second connecting line is a ground line or carries a negative supply voltage, etc. In other words, the two connecting lines must be connected in parallel to one another between the power module and the motor module.

The invention is explained here using two connecting lines, but the invention can also be extended to several connecting lines, for example for systems with several phases; however, this will not be explained in more detail here.

The recuperation circuit contains a diode arrangement. This is connected between the connecting lines. This means that one end of the diode arrangement is connected to the first line and the other end of the diode arrangement is connected to the second line. The diode arrangement is designed to automatically connect the two connecting lines in a conductive manner above a threshold voltage and otherwise (i.e. below the threshold voltage) to isolate the two lines from each other. The threshold voltage refers to the voltage that is present on the diode arrangement or between the two lines. "Isolating" is to be understood in such a way that although a comparatively small current, for example a diode blocking current between the two lines, may flow through the diode arrangement, this is negligible, i.e. no significant electrical power is converted in the recuperation circuit in the diode arrangement. In the conductive state, on the other hand, a much larger, noticeable first power is dissipated from the connecting lines and consumed or destroyed in the diode arrangement, in particular converted into heat.

“Self-switching” is to be understood as meaning that the basic electrical properties of diodes, namely their (automatic, without additional switching process, etc.) current conduction from a certain voltage value (forward direction / reverse direction), are used.

The threshold voltage is chosen so high that it is never reached in regular, intended and error-free drive operation, but can be reached in recuperation mode and - at least without the measures of the recuperation circuit - can be exceeded. Furthermore, the threshold voltage is chosen so that from this value onwards the supply module (an intermediate circuit) is protected from even significantly higher voltages in recuperation mode. This means that from this voltage onwards sufficient energy should be destroyed/removed from the drive arrangement in order to protect its components.

The recuperation circuit also contains an ohmic resistor arrangement. This is connected between the connecting lines (like the diode arrangement or parallel to it). The resistor arrangement can be switched on or off as desired. In the same way as the diode arrangement, when switched off the resistor arrangement isolates the two connecting lines from each other, i.e. only insignificant leakage currents flow through it. In the deliberately switched on state, however, a significant current flows through the resistor arrangement and is consumed, destroyed or converted into heat in an ohmic resistor. Here too, in the same way as above, a significant amount of power is dissipated from the connecting lines when switched on. In contrast to the diode arrangement, the resistor arrangement is not self-switching above a certain voltage, but can or must be switched on or off as desired in order to consume power or not.

The recuperation circuit also contains a control device. This has an input. The input is used or is set up to receive a value. The value is correlated with the (in particular current) voltage between the connecting lines. “Correlated” means that it is, for example, the corresponding voltage value of the voltage itself or any value correlated with this voltage value that is suitable for the protection purposes at hand. The voltage between the connecting lines corresponds in particular to the voltage in the supply module or an intermediate circuit between the supply module and the connecting lines. The value can reach the input in the form of an analogue measured value, in the form of data, etc.

The control device is set up to switch on the resistor arrangement in the recuperation mode of the recuperation circuit in a clocked manner with a switching cycle with a duty cycle (duty cycle). The duty cycle is the proportion of switching on in relation to an entire clock period under consideration, e.g. according to the standard PWM (pulse width modulation). However, this only happens from a value that corresponds to a first limit voltage between the connecting lines, i.e. as soon as the above-mentioned value reflects the reaching of the limit voltage between the connecting lines and thus across the resistor arrangement and the diode arrangement. Otherwise, the control device switches off the resistor arrangement. This switching off therefore always applies both in drive mode and in recuperation mode, as long as the limit voltage is not reached. The first limit voltage is selected to be lower than the threshold voltage.

According to the invention, the voltages between the two connecting lines are limited in recuperation mode. This happens when the power supplied by the motor module is partially destroyed in the resistor arrangement and possibly also in the diode arrangement, thus preventing it from being passed on to the feed module. According to the invention, a combination of diodes in the form of suppressor diodes in the diode arrangement and a braking resistor in the form of an ohmic resistor in the resistor arrangement is used. The recuperation circuit works as intended as follows: in a first step, for increased voltages from the first limit voltage (for example 58V in a 48V drive arrangement), the switch of the braking resistor (resistance arrangement) is opened and closed with a first duty cycle. In this way, some of the energy is already destroyed. The suppressor diodes do not absorb any energy here because the threshold voltage has not yet been reached. This means that the recuperation power is still high, but there is already weak protection for the feed module.

In a second step, from the threshold voltage of, for example, 60V, the suppressor diodes are additionally active, the braking resistor (resistor arrangement) continues to absorb energy and is in particular set to a second duty cycle, which in particular corresponds to a maximum possible duty cycle with regard to heat dissipation or maximum possible heat absorption in the resistor arrangement in order to also absorb energy (or even more than before).

If the voltage falls below the threshold again, the suppressor diodes become ineffective again and the switch of the braking resistor is However, it continues to operate at the duty cycle, particularly at a lower duty cycle, in order to reduce the energy dissipation in the resistor arrangement. If the voltage continues to fall below the first limit voltage, the brake resistor switch remains open so that no more energy is absorbed in the resistor arrangement. The suppressor diodes are also still ineffective.

Thus, an escalation arrangement/procedure is established that enables targeted, step-by-step energy destruction and thus different levels of protection for the power supply module.

In a preferred embodiment, the control device is designed to switch on the resistance arrangement with the switching clock with a first clock ratio in the recuperation mode of the recuperation circuit for voltages from the first limit voltage. From a second limit voltage that is greater or higher than the first, it then switches on the resistance arrangement with the switching clock with a second clock ratio. The second clock ratio is different from the first clock ratio, in particular higher than it, which leads to a higher power consumption in the resistance arrangement.

Further "second stages" are also possible here, with increasingly higher second limit voltages and different clock ratios, whereby a subsequent clock ratio differs from the previous one; in particular, the clock ratio increases successively. In this way, escalating (in particular more) power can be implemented in the resistor arrangement. In this way, different (increasingly more) power can be dissipated gradually from the connecting lines in order to (increasingly) protect the supply module / the intermediate circuit.

In a preferred variant of this embodiment, the second limit voltage (at least one of the second limit voltages, if there are several) is the threshold voltage. Alternatively or additionally, the second duty cycle (particularly associated with the threshold voltage) is greater than the first duty cycle. This ensures at least a two-stage escalating process in order to absorb a lower power in the resistor arrangement below the limit voltage and a higher power above the threshold voltage/relevant second limit voltage.

In a preferred variant of this embodiment, the second clock ratio (at least one of several, in particular the one belonging to the threshold voltage) is selected such that (at this voltage) a maximum permissible electrical power is absorbed in the resistor arrangement or the power is limited to a maximum. The second clock ratio can also be adjusted, for example, depending on the voltage - even dynamically - to further increasing voltage, for example step by step through the higher second limit voltages mentioned above. This ensures that (almost) the desired ohmic power is always absorbed and destroyed in the resistor arrangement, in order to optimally support the diode arrangement in particular or to optimally protect the supply module / intermediate circuit, but only destroy the necessary power.

In a preferred embodiment, the diode arrangement contains at least two diodes which are connected in series between the connecting lines. In particular, the diode arrangement contains diodes in pairs, i.e. 2, 4, 6, etc., with 2 diodes in series and such series connections connected in parallel. This makes it possible to realize a particularly effective diode arrangement.

In a preferred embodiment, the diode arrangement and the resistor arrangement are dimensioned such that they have the same impedances for voltages between the connecting lines at or above the threshold voltage, in particular already from the (lower) first limit voltage. This is to be understood within the scope of usual tolerances of, for example, 0.1%, 1%, 2%, 5%, 10%, 20%, etc. From this voltage, the dimensioning is chosen in particular such that currents through the diode arrangement and the resistor arrangement are evenly distributed. All of this applies in particular to the time average in relation to the clocking of the resistor arrangement. In particular, this makes it possible to achieve an equal distribution of the average power that is implemented in the diode arrangement and the resistor arrangement. Neither of the two arrangements/circuits (diodes/resistors) is thus excessively loaded.

The object of the invention is also achieved by a control device according to claim 7 for the electric drive arrangement as described above. The control device contains the recuperation circuit according to the invention. Furthermore, the control device contains an inverter connected to the connecting lines on one side of the recuperation circuit towards the motor module. Alternatively or additionally, the control device contains a direct current link (DC link, contains or is a direct current intermediate circuit) for the feed module connected to the connecting lines on the other side of the recuperation circuit, namely towards the feed module. The recuperation The control circuit protects the intermediate circuit in particular against overvoltages in recuperation mode. The intermediate circuit reduces the recuperation voltage (e.g. greater than 58V) to the maximum permitted voltage of the supply module or a corresponding recuperation circuit (e.g. arrangement according to VDA 320. For a 48V converter, voltages between 36V and 58V are permitted). The inverter is used to convert direct voltage/direct current on the connecting lines to alternating quantities on the part of the motor module. The control unit and at least some of its possible embodiments as well as the respective advantages have already been explained in connection with the recuperation circuit according to the invention.

The object of the invention is also achieved by a drive arrangement according to claim 8, as already described above. This contains the recuperation circuit according to the invention or the control unit according to the invention and thus also contains the feed module and the motor module. The feed module and motor module are connected to one another by the two connecting lines. The drive arrangement and at least some of its possible embodiments as well as the respective advantages have already been explained in connection with the recuperation circuit according to the invention and the control unit.

The object of the invention is also achieved by a method according to claim 9 for operating the recuperation circuit according to the invention or the control device according to the invention or the drive arrangement according to the invention. In the method, the control device always switches the resistance arrangement off in drive mode or leaves it permanently switched off. In recuperation mode, however, the control device switches the resistance arrangement on from values corresponding to the first limit voltage with the switching cycle with the (respective, if different, see above) cycle ratio. Otherwise, it switches the resistance arrangement off in recuperation mode too (i.e. for voltages below the first limit voltage) or leaves it switched off.

The method and at least some of its possible embodiments as well as the respective advantages have already been explained in connection with the recuperation circuit according to the invention and the control unit and the drive arrangement.

The invention is based on the following findings, observations and considerations and also has the following preferred embodiments. These embodiments are sometimes referred to as "the invention" for the sake of simplicity. The embodiments can also contain parts or combinations of the above-mentioned embodiments or correspond to them and/or possibly also include embodiments not previously mentioned.

According to the present invention, among other things, a method for limiting the voltage of the supply module / the intermediate circuit voltage during recuperation is provided.

The present invention also relates to a control device. The control device comprises, for example, an inverter and an intermediate circuit to the supply module. The intermediate circuit consists, for example, of one or more capacitors. The invention also requires a motor, in particular an AC motor (in the case of the inverter), which is connected to the control device. The motor and control device can be part of a higher-level system, such as a roll stabilizer of a motor vehicle.

The higher-level system must be designed in such a way that recuperation operation is possible. This means that there is an energy flow from the engine towards the control unit. The energy is processed by the inverter and from there it reaches an on-board network connected to the system. During recuperation operation, the inverter converts AC currents and voltages into DC currents and voltages. 48V systems can be used, for example, in hybrid vehicles that use recuperation to charge the vehicle's battery. The present invention can also be used for other voltage classes, e.g. 12 V, 24 V. The present invention is described for a 48V system as an example.

Strict ASIL safety requirements apply to automotive systems. Excessively high voltages can damage components (e.g. intermediate circuit capacitors, semiconductor components) or the vehicle electrical system. Therefore, a device for limiting the voltage must typically be built into the control unit if high recuperation voltages are possible.

The suppressor diodes known from practice become conductive when a component-specific voltage is exceeded. These suppressor diodes limit the voltage from a certain value, e.g. 60 V. The application of the suppressor diodes is limited to short-term overvoltages, so the suppressor diodes can destroy a certain amount of energy. If the amount of energy is greater than a critical value, the suppressor diodes are destroyed. The current of the voltage pulse is reduced by connecting the Suppressor diodes are routed past the component to be protected.

In practice, braking resistors in frequency converters for voltage limitation are used, whereby a switch is installed in series with a braking resistor parallel to the intermediate circuit. When the switch is closed, energy is converted into heat at the braking resistor. The braking resistor must be dimensioned sufficiently large to be able to dissipate the energy. Opening and closing the switch determines how much energy is destroyed. This limits the intermediate circuit voltage.

Both systems known from practice, voltage limitation with suppressor diodes and with braking resistors, have disadvantages. One disadvantage of suppressor diodes is that they are only designed for short-term voltage pulses. They are destroyed after a certain amount of energy has been absorbed. In addition, the voltage can only be limited at exactly one threshold value.

The disadvantages of the braking resistor are that it has to be dimensioned relatively large in order to be able to dissipate the heat.

The invention is based on the consideration of how the voltage can be limited even at higher recuperation energy.

• - In einem ersten Schritt wird für erhöhte Spannungen, ab einer ersten Grenzspannung von z. B. 58 V, der Schalter des Bremswiderstandes mit einem ersten Tastverhältnis geöffnet und geschlossen. Somit wird schon ein Teil der Energie vernichtet. Die Supperssordioden nehmen hier noch keine Energie auf.
• - In einem zweiten Schritt werden ab einer Schwellspannung, die gleich einer zweiten Grenzspannung ist, von z. B. 60 V die Suppressordioden aktiv, der Bremswiderstand wird dann zusätzlich in das zweite Tastverhältnis versetzt (maximal mögliches Tastverhältnis bezüglich Wärmeabfuhr), um ebenfalls Energie aufzunehmen.
• - Fällt die Spannung wieder unter die Schwellspannung / zweite Grenzspannung (60 V), dann wird die Suppressordiode unwirksam und für den Schalter des Bremswiderstandes wird wieder das erste Tastverhältnis (weniger Energievernichtung) gesetzt.
• - Fällt die Spannung unter den ersten Grenzwert (58 V) bleibt der Schalter des Bremswiderstandes geöffnet, so dass keine Energie absorbiert wird. Die Suppressordioden sind ebenfalls unwirksam.

The invention therefore relates to methods and devices for limiting the voltages in recuperation mode. The essential features of the invention are that a combination of supersor diodes and braking resistors is used. The method comprises the following steps:

• - In a first step, for increased voltages, starting from a first limit voltage of e.g. 58 V, the switch of the braking resistor is opened and closed with a first duty cycle. In this way, part of the energy is already destroyed. The supersor diodes do not absorb any energy at this point.
• - In a second step, the suppressor diodes become active from a threshold voltage that is equal to a second limit voltage, e.g. 60 V, and the braking resistor is then additionally set to the second duty cycle (maximum possible duty cycle with regard to heat dissipation) in order to also absorb energy.
• - If the voltage falls below the threshold voltage / second limit voltage (60 V) again, the suppressor diode becomes ineffective and the first duty cycle (less energy dissipation) is set again for the braking resistor switch.
• - If the voltage falls below the first limit (58 V), the braking resistor switch remains open so that no energy is absorbed. The suppressor diodes are also ineffective.

In particular, two suppressor diodes should be connected in series. For example, two or four suppressor diodes can be used. The suppressor diodes should be arranged parallel to the supply module/intermediate circuit. The braking resistor with switch should also be arranged parallel to the supply module/intermediate circuit.

There should be a particularly analogue monitoring of the voltage between the connecting cables / in the supply module / intermediate circuit voltage, which passes its measured value on to the control device, e.g. a µC (microcontroller). Depending on the measured value, the µC then decides how the brake resistor switch should be controlled. When designing the components, it is particularly important to ensure that both impedances (of diodes and resistor arrangement) are similar for the operating state above the threshold voltage (60 V) so that the current is distributed evenly (between both arrangements).

Depending on the requirements of the higher-level system, this method/device has the flexibility to adjust thresholds (limit values/threshold values) and duty cycles. This flexibility is an advantage of the method/device, which is based on a topology of braking resistors and suppressor diodes. Another advantage is that the braking resistor can be made smaller because the suppressor diodes absorb some of the energy.

• 1 eine Antriebsanordnung in einer Prinzipskizze,
• 2 verschiedene Ströme und Leistungen in der Antriebsanordnung nach 1 für verschiedene Spannungen zwischen den Verbindungsleitungen.

Further features, effects and advantages of the invention emerge from the following description of a preferred embodiment of the invention and the attached figures. Each of these shows a schematic principle sketch:

• 1 a drive arrangement in a schematic diagram,
• 2 different currents and powers in the drive arrangement according to 1 for different voltages between the connecting lines.

1 shows a drive arrangement 2. This contains a power module 4, here a 48V electrical system of a motor vehicle. The drive arrangement 2 contains a motor module 6, here a motor operated with alternating voltage or alternating current (AC motor). This is part of a higher-level system, namely a roll stabilizer in the motor vehicle. The drive arrangement 2 also contains a control unit 8, which is also part of the higher-level system, i.e. the wall stabilizer.

In the higher-level system, a recuperation mode RB is possible, which is indicated here by an arrow. The arrow symbolizes the flow of energy from the motor module 6 to the feed module 4 through the control unit 8. The drive arrangement 2 can also be operated in a drive mode AB. In this, electrical energy is transported from the feed module 4 to the motor module 6, which in 1 is also symbolized by an arrow.

The control unit 8 contains a recuperation circuit 12 and, on its side 14a towards the motor module 6, an inverter 16 and, on its side 14b towards the feed module 4, a DC link 18, here a DC intermediate circuit.

The feed module 4 is connected to the recuperation circuit 12 via the DC link 18. This is connected to the motor module 6 via the inverter 16. Two connecting lines 10a,b connect the feed module 4 and the motor module 6, here in particular the DC link 18 to the inverter 16 and lead through the recuperation circuit 12. The recuperation circuit 12 contains a section of each of the connecting lines 10a,b.

The control unit 8 contains a voltmeter 20, which is only symbolically indicated here and is designed to map the voltage U between the connecting lines 10a,b to a value W, here the voltage value of the voltage U.

The recuperation circuit 12 also contains a diode arrangement 22 which is connected between the two connecting lines 10a,b. In the present case, the diode arrangement 22 contains two suppressor diodes 24 connected in series. The diode arrangement 22 is thus designed to be self-switching in such a way that it only electrically connects the connecting lines 10a,b (significant, apart from leakage/blocking currents) above a threshold voltage US (here the breakdown voltage of the series connection of the two suppressor diodes 24) and otherwise electrically isolates them from one another (below the threshold voltage US, possibly only leakage/blocking currents).

2 shows a purely qualitative diagram in which the voltage U is plotted between the two connecting lines 10a,b. The voltage UN here is the nominal voltage of the circuit module 4, here 48 V. This voltage is present when the drive arrangement 2 is in drive mode Abi.

2 shows qualitatively the course of a diode current ID, which flows between the connecting lines 10a,b through the diode arrangement 22. The current ID is plotted against the voltage U. This is initially zero, this also applies at the nominal voltage UN of 48V (drive operation AB) and up to the threshold voltage US of 60V. Here the diodes 24 switch through and the current ID increases abruptly. At the threshold voltage US the self-switching switching through of the diode arrangement 22 takes place, which is why it connects the connecting lines 10a,b conductively above the threshold voltage US in order to enable the current flow ID. As a result, an electrical power PD (in 2 symbolically indicated) in the diode arrangement 22, namely and discharged from the connecting lines 10a,b and destroyed in the diode arrangement 22 in the form of heat. This relieves the load on the direct current link 18, since the voltage U does not increase or does not increase as much as in a situation without recuperation circuit 12. All of this only applies in recuperation mode RB, since only then can voltages above the nominal voltage UN occur.

The recuperation circuit 12 also contains a resistor arrangement 26. This is connected in parallel to the diode arrangement 22 between the connecting lines 10a,b. This or its effect can be switched on or off. For this purpose, it has a switching element 28 and an ohmic resistor 30, which are connected in series between the connecting lines 10a,b. The switching element 28 achieves the switchability mentioned above. If the switching element 28 is switched off (off, open, OFF), no current flow of a resistance current IR takes place through the resistor arrangement 26. If the switching element 28 is switched on (on, closed, ON), the resistance current IR flows through the ohmic resistor 30 and an electrical power PR is withdrawn from the connecting lines 10a,b and destroyed in the resistor arrangement 26 (converted into heat). In the same way as above, this also reduces the voltage U compared to a state when no power PR would be destroyed in recuperation mode RB.

The switching element 28 or the resistor arrangement 26 is controlled here in a clocked manner with a switching clock (for example PWM operation, pulse width modulation, 10kHz). By changing the The magnitude of the electrical power PR which is absorbed and dissipated in the resistance arrangement 26 on average over time can be controlled by the clock ratio T (ON/clocking period) of the switching clock.

The recuperation circuit 12 also contains a control device 32. This contains an input 34 for receiving the value W, which is correlated with the current voltage U between the connecting lines 10a,b, here corresponds to this. The control device 32 is set up to control the resistor arrangement 26 in a clocked manner with a switching clock with a first clock ratio T1 of here 25% only in the recuperation mode RB and only for values W that correspond to voltage values of the voltage U from or above a first limit voltage UG1. The resistance current IR (the time average is indicated in the figure) thus flows in a clocked manner through the resistor arrangement 26. In this case, the resistor arrangement absorbs or destroys a time-averaged electrical power PR. The limit voltage UG1 is smaller than the threshold voltage US.

The control device 32 is designed to control the resistor arrangement 26 with a second duty cycle T2, here 75%, starting from values W that correspond to a second limit voltage UG2, here the threshold voltage US. The time-averaged current IR current as well as the electrical power PR thus increase.

The clock ratio T2 is chosen so that the power PR now corresponds to the power PD. In 1 For the sake of clarity, this is indicated by a slightly offset line for the resistance current IR.

The control device 32 is also designed as follows: Both in drive mode AB and in recuperation mode RB below the first limit voltage UG1, the resistance arrangement 26 remains switched off, the resistance current IR is zero, as is the power PR.

The second clock ratio T2 is therefore different from the first clock ratio T1 and higher than the latter. Alternatively, the second clock ratio T2 is always selected such that the maximum permissible electrical power PR is always absorbed in the resistor arrangement 26, i.e. the ohmic resistor 30 is operated at its thermal limit load.

This ensures that the voltage U can hardly rise above the threshold voltage US (in 2 (shown enlarged for clarity).

The equality of the powers PD and PR is achieved by keeping the impedances of the resistor arrangement 26 and the diode arrangement 22 equal from the threshold voltage US onwards, so that approximately the same amounts of diode current ID and resistor current IR always flow.

Reference symbols

2

Drive arrangement

4

Feed module

6

Motor module

8th

Control unit

10a,b

Connecting line

12

Recuperation circuit

14a,b

Page

16

Inverter

18

DC link

20

Voltmeter

22

Diode arrangement

24

Diodes

26

Resistor arrangement

28

Switching element

30

ohmic resistance

32

Control device

34

Entrance

RB

Recuperation mode

AWAY

Drive operation

U

Tension

US

Threshold voltage

U.N.

nominal voltage

ID

Diode current

IR

Resistance current

PD,PR

Power (electrical)

W

Value

UG1,2

Limit voltage

T1,2

Clock ratio

Claims (9)

Recuperation circuit (12) for an electric drive arrangement (2) which contains a feed module (4) and a motor module (6) and which can be operated in a drive mode (AB) and in a recuperation mode (RB), - with at least one respective section of two connecting lines (10a,b) for connecting Supply module (4) and motor module (6), - with a diode arrangement (22) connected between the connecting lines (10a,b), which is designed to connect the two connecting lines (10a,b) in a conductive manner from a threshold voltage (US) and otherwise to isolate them from one another, - with an ohmic resistance arrangement (26) connected between the connecting lines (10a,b) so that it can be switched on or off, - with a control device (32) with an input (34) for receiving a value (W) which is correlated with the voltage (U) between the connecting lines (10a,b), - wherein the control device (32) is designed to switch the resistance arrangement (26) on in the recuperation mode (RB) of the recuperation circuit (12) from values (W) corresponding to a first limit voltage (UG1) between the connecting lines (10a,b) in a clocked manner with a switching clock with a clock ratio (T1,2) and to switch them off otherwise, - where the first limit voltage (UG1) is smaller than the threshold voltage (US). Recuperation circuit (12) after Claim 1 , characterized in that - the control device (32) is set up to switch on the resistance arrangement (26) in the recuperation mode (RB) of the recuperation circuit (12) from values (W) corresponding to the first limit voltage (UG1) with the switching clock with a first clock ratio (T1) and to switch on the resistance arrangement (26) from values (W) corresponding to a second limit voltage (UG2) with the switching clock with a second clock ratio (T2), - wherein the second limit voltage (UG2) is higher than the first limit voltage (UG1) and the second clock ratio (T2) is different from the first clock ratio (T1). Recuperation circuit (12) after Claim 2 , characterized in that the second limit voltage (UG2) is the threshold voltage (US) and / or the second clock ratio (T2) is greater than the first clock ratio (T1). Recuperation circuit (12) according to one of the Claims 2 until 3 , characterized in that the second clock ratio (T2) is selected such that a maximum permissible electrical power (PR) is always absorbed in the resistance arrangement (26). Recuperation circuit (12) according to one of the preceding claims, characterized in that the diode arrangement (22) contains at least two diodes (24) connected in series between the connecting lines (10a,b). Recuperation circuit (12) according to one of the preceding claims, characterized in that the diode arrangement (22) and the resistor arrangement (24) are dimensioned such that they have equal impedances starting from the threshold voltage (US) between the connecting lines (10a,b). Control device (8) for an electric drive arrangement (2) which contains a feed module (4) and a motor module (6) and which can be operated in a drive mode (AB) and in a recuperation mode (RB), - with the recuperation circuit (12) according to one of the preceding claims, and - with an inverter (16) connected to the connecting lines (10a,b) on one side (14a) of the recuperation circuit (12) towards the motor module (6), - and/or with a DC voltage link (18) connected to the connecting lines (10a,b) on the other side (14b) towards the feed module (4). Drive arrangement (2), with the recuperation circuit (12) according to one of the Claims 1 until 6 or with the control unit (8) after Claim 7 , - and with the feed module (4) and the motor module (6), - wherein the feed module (4) and the motor module (6) are connected to one another by the two connecting lines (10a,b). Method for operating the recuperation circuit (12) according to one of the Claims 1 until 6 or the control unit (8) after Claim 7 or the drive arrangement (2) according to Claim 8 , in which: - in drive mode (AB) the control device (32) always switches off the resistance arrangement (26), - in recuperation mode (RB) the control device (32) switches on the resistance arrangement from values (W) corresponding to the first limit voltage (UG1) with the switching cycle with the cycle ratio (Ta,2), and otherwise switches it off.

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