Device for de-energizing at least one rotor winding of a synchronous machine, synchronous machine, method for operating a synchronous machine, motor vehicle

Abstract

Device (100) for de-energizing at least one rotor winding (110) of an electrically separately excited synchronous machine (925), wherein the device (100) has the following feature: a stator current control unit (102) configured to imprint a stator current value onto a stator current such that a value of Id stator current (515) after deactivation of the synchronous machine (925) has a predefined, positive value and is higher than the Id stator current (515) before deactivation.

Description

[0001] The present invention relates to a device for de-energizing at least one rotor winding of a synchronous machine, a synchronous machine, a method for operating a synchronous machine and a motor vehicle.

[0002] DE 10 2018 201 321 A1 discloses a method for operating an arrangement comprising an electrical machine and a rectifier.

[0003] The document DE 10 2017 202 714 A1 discloses a method and a system for controlling a separately excited electrical synchronous machine.

[0004] The document DE 10 2017 200 220 A1 discloses a control method and a switching device.

[0005] The document DE 10 2017 112 572 A1 discloses a self-exciting active discharge circuit for electric vehicle inverters.

[0006] The document US 2016 / 0233816 A1 discloses a motor drive device and a laundry treatment device comprising this motor drive device.

[0007] Against this background, the present invention provides an improved device for de-energizing at least one rotor winding of a synchronous machine, an improved synchronous machine, an improved method for operating a synchronous machine, and an improved motor vehicle according to the main claims. Advantageous embodiments emerge from the subclaims and the following description.

[0008] The advantages achievable with the approach presented here consist in particular in the fact that a device is created which can enable a reliable and rapid de-excitation of at least one rotor winding of a synchronous machine.

[0009] A corresponding device for de-energizing at least one rotor winding of an electrically separately excited synchronous machine comprises a stator current control unit. The stator current control unit is designed to impress a stator current value onto a stator current such that a value of an Id stator current after deactivation of the synchronous machine has a predefined, positive value and is higher than the Id stator current before deactivation.

[0010] The electrically separately excited synchronous machine can be an electric machine for driving a motor vehicle. The stator current control unit can generate or adjust the stator current, for example the Id stator current. When the synchronous machine is deactivated, the synchronous machine can switch to generator operation. In this state, at least one rotor winding can be de-excited using the predefined or actively adjustable Id stator current. By actively adjusting the Id stator current, a significantly faster de-excitation of the rotor current can be achieved than would be the case if the stator current were allowed to run freely. The approach presented here can therefore also be understood as a rapid rotor de-excitation of the electrically excited synchronous machine or as a rapid de-excitation of the rotor winding of the electrically excited synchronous machine.The electrically excited synchronous machine can also be abbreviated to EESM. The approach presented here can enable overvoltage and overcurrent prevention of the electrically excited synchronous machine in the event of a fault. A fault could be, for example, a load shedding of the battery at the generator's corner point, an active short circuit (ACS), and / or an inverter lockout (WRS).

[0011] The stator current control unit can be designed to impress the stator current such that the value of the Id stator current can lie within a tolerance range of 50 percent of the maximum possible Id stator current value. In particular, the value of the Id stator current can lie within a tolerance range of 10 percent of the maximum possible Id stator current value. In particular, the value of the Id stator current can be set to the maximum possible Id stator current value. Advantageously, the at least one rotor winding can be de-energized reliably and quickly if the stator current is impressed to a high Id stator current value. The higher or more positive the value of the Id stator current, the faster the rotor winding can be de-energized.

[0012] The stator current control unit can be configured to impose a stator current value on the stator current such that, after deactivation of the synchronous machine, the Iq stator current can have a value of 0 amperes within a tolerance range. The Iq stator current can be regulated from a negative value to 0 amperes after deactivation of the synchronous machine. This can have a beneficial effect on the de-excitation of the rotor winding.

[0013] The device may comprise a rotor current control unit, which may be configured to actively short-circuit a rotor current of a rotor of the synchronous machine after deactivation of the synchronous machine. Short-circuiting the rotor current may have a beneficial effect on the speed of de-excitation.

[0014] The stator current control unit can be configured to activate an inverter lock mode after deactivating the synchronous machine. An inverter lock mode can be understood as a state in which an inverter is locked, so that no electrical power is transported or transmitted via the inverter. For example, such an inverter lock can be achieved by opening all switching elements of the inverter. Activating the inverter lock in this way can accelerate de-excitation of the electrical machine.

[0015] The device may include a discharge resistor device connected between two terminals of an intermediate circuit of the synchronous machine to cause a discharge current between the terminals of the intermediate circuit via a discharge resistor when a voltage between the two terminals exceeds a threshold value. Thus, damage to the device can be avoided or prevented. The discharge resistor can be manufactured cost-effectively.

[0016] The discharge resistance device can be configured to suppress the discharge current when the voltage between the terminals falls below the specified threshold, and additionally or alternatively to prevent it. Thus, an active short circuit can only be activated for those scenarios in which damage to components of the devices used is to be expected.

[0017] The discharge resistance device may comprise a switching device that may be connected in series with the discharge resistance. The switching device can be manufactured inexpensively and quickly.

[0018] The switching device can comprise a MOSFET semiconductor component and a comparator circuit, a thyristor, an IGBT, and additionally or alternatively a Zener diode. The advantages of the approach described here can also be realized very efficiently using such an embodiment.

[0019] An electrically separately excited synchronous machine comprises one embodiment of a device mentioned herein. In particular, a rotor of the synchronous machine is electrically coupled, or can be coupled, or fed inductively or conductively. Such an embodiment also allows the advantages of the approach described here to be realized very efficiently.

[0020] In addition, the invention relates to a power converter, in particular an inverter, for a motor vehicle with an embodiment of a device mentioned herein.

[0021] In addition, the invention relates to an electric axle drive for a motor vehicle with at least one electric machine, a transmission device and an embodiment of a power converter described herein.

[0022] Using the inverter, the alternating electrical current required to operate the electric machine can be provided. Using the transmission device, a torque provided by the electric machine can be converted into a drive torque for driving at least one wheel of the motor vehicle. The transmission device can have a gearbox for reducing the speed of the electric machine and, optionally, a differential.

[0023] The invention also relates to a motor vehicle with an embodiment of a power converter mentioned herein and, additionally or alternatively, with an embodiment of an electric axle drive mentioned herein and, additionally or alternatively, with an embodiment of a device mentioned herein. The motor vehicle can additionally have an embodiment of an electrically separately excited synchronous machine mentioned herein.

[0024] A method for operating an embodiment of an electrically separately excited synchronous machine mentioned herein comprises an impressing step. In the impressing step, a stator current is impressed to a stator current value such that a value of an Id stator current after deactivation of the synchronous machine has a predefined, positive value that is higher than the Id stator current before deactivation.

[0025] Also advantageous is a computer program product or computer program with program code that can be stored on a machine-readable carrier or storage medium such as a semiconductor memory, a hard disk memory or an optical memory and is used to carry out, implement and / or control the steps of the method according to one of the embodiments described above, in particular when the program product or program is executed on a computer or a device.

[0026] The invention is explained in more detail by way of example with reference to the accompanying drawings. They show: Fig. 1 is a circuit diagram of an embodiment of a device for a synchronous machine; Fig. 2 a circuit diagram of an embodiment of a device for a synchronous machine; Fig. 3 is a diagram of a discharge resistance device for an embodiment of a device; Fig. 4 shows a representation of a diode circuit for an embodiment of a device; Fig. 5 is a diagram illustrating signal waveforms to explain an embodiment of a device; Fig. 6 is a diagram illustrating signal waveforms to explain an embodiment of a device; Fig. 7 is a diagram illustrating signal waveforms to explain an embodiment of a device; Fig. 8 is a diagram illustrating signal waveforms to explain an embodiment of a device; Fig. 9 is a schematic representation of an embodiment of a motor vehicle; and Fig. 10 a flowchart of an embodiment of a method for operating a synchronous machine.

[0027] In the following description of preferred embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the various figures and having a similar effect, whereby a repeated description of these elements is omitted.

[0028] Fig. Figure 1 shows a circuit diagram of an embodiment of a device 100 for a synchronous machine. In other words, Fig. 1 shows a circuit for an inductive exciter. The device 100 is designed, for example, to de-energize at least one rotor winding 110 of the synchronous machine. The synchronous machine is designed, for example, as an electrically separately excited synchronous machine and is part of a motor vehicle to drive the motor vehicle. De-energizing the rotor winding 110 is important, for example, in the event of a fault in the synchronous machine to prevent damage to the device 100. The following applies: the faster the rotor winding 110 is de-energized, the faster the synchronous machine or the motor vehicle is in a safe state.

[0029] The device 100 has a stator current control unit 102 and, according to one exemplary embodiment, additionally a rotor current control unit 104 and a discharge resistance device 116. The stator current control unit 102 can also be referred to as a stator, and the rotor current control unit 104 can be referred to as a rotor. The stator current control unit 102 has, merely by way of example, a bridge circuit unit 106, wherein the discharge resistance device 116 is connected, for example, within the bridge circuit unit 106. In addition, the stator current control unit 106 has a filter device 114 and at least partially a transformer device 112. The rotor current control unit 104 has, merely by way of example, a further bridge circuit unit 108, which has at least one rotor winding 110 and at least partially the transformer device 112.

[0030] According to one exemplary embodiment, the device 100 has a first supply voltage terminal 124 and a second supply voltage terminal 134 for applying a DC supply voltage. An energy storage device 144, in this case a capacitor, is connected between the first supply voltage terminal 124 and the second supply voltage terminal 134. For example, a high-voltage battery can be connected to the supply voltage terminals 124, 134. A second energy storage device 154, for example, is connected between the supply voltage terminals 124, 134. The supply terminals 124, 134 and the energy storage devices 144, 154 are merely exemplary parts of the filter device 114, which can also be referred to as an EMI filter. According to one exemplary embodiment, the filter device 114 has two chokes 164, 174 connected between the energy storage devices 144, 154.The choke 164 is connected between a first tapping point of the energy storage device 144 and a second tapping point of the second energy storage device 154. The further choke 174 is connected between another first tapping point of the energy storage device 144 and another second tapping point of the second energy storage device 154. The filter device 114 is designed, for example, to reduce electromagnetic high-frequency interference that is transmitted through the lines and can cause interference with other devices.

[0031] The bridge circuit unit 106 is designed, for example, to convert the DC supply voltage into an AC supply voltage. The AC supply voltage is subsequently converted by the transformer device 112 into an AC output voltage, with the further bridge circuit unit 108 converting the AC output voltage into the DC output voltage. According to one embodiment, the bridge circuit unit 106 is designed as an H-bridge and can also be referred to as an H-bridge. For this purpose, the bridge circuit unit 106 has, for example, a first half-bridge 126 and a second half-bridge 136. The first half-bridge 126 has a first switch 146 and a second switch 156, with the switches 146, 156 being connected to one another via a first tapping point 103.The first switch 146 is connected, for example, between the first supply voltage terminal 124 and the first tapping point 103, and the second switch 156 is connected between the second supply voltage terminal 134 and the first tapping point 103. The second half-bridge 136 has a third switch 166 and a fourth switch 176, wherein the switches 166, 176 are connected to one another via a second tapping point 113. The third switch 166 is connected, for example, between the first supply voltage terminal 124 and the second tapping point 113, and the fourth switch 176 is connected between the second supply voltage terminal 134 and the second tapping point 113. The switches 146, 156, 166, 176 are designed, for example, as transistors.Each of the transistors comprises, for example, a control input and a first switching input and a second switching input, wherein a current flow between the switching inputs can be controlled via a switching signal applied to the control input. The tapping points 103, 113 are designed, for example, to output the AC supply voltage.

[0032] According to one embodiment, a third energy storage device 123 is connected between the supply terminals 124, 134 and the first half-bridge 126. According to one embodiment, the discharge resistor device 116 is connected between the half-bridges 126, 136.

[0033] The transformer device 112 is connected, for example, between the bridge circuit unit 106 and the further bridge circuit unit 108 and can also be referred to as a rotary transformer. The transformer device 112 has a first choke 122 and a second choke 132 for converting the AC supply voltage into the AC output voltage, wherein the chokes 122, 132 are coupled, for example, via a common core for conducting a magnetic field. In order to convert the AC supply voltage into the AC output voltage, which differs from the AC supply voltage in terms of an electrical voltage magnitude, the chokes 122, 132 can differ in the number of their turns. The first choke 122 is connected to the first tapping point 103 via a first contact and to the second tapping point 113 via a second contact.According to one embodiment, a further choke 142 is connected between the first contact and the first tapping point 103.

[0034] The further bridge circuit unit 108 can, for example, be designed as a rectifier and can therefore also be referred to as a rectifier. The further bridge circuit unit 108 has, for example, a third half-bridge 118 and a fourth half-bridge 128. The third half-bridge 118 has a first diode 148 and a second diode 158, wherein the diodes 148, 158 are connected to one another via a third tapping point 133. The fourth half-bridge 128 has a third diode 168 and a fourth diode 178, wherein the diodes 168, 178 are connected to one another via a fourth tapping point 143.

[0035] The second choke 132 of the transformer device 112 is connected to the third tapping point 133 via a further first contact and to the fourth tapping point 143 via a further second contact.

[0036] The at least one rotor winding 110, which can also be referred to as rotor windings, is connected, for example, adjacent to the further bridge circuit unit 108 and has a choke 120 and a resistor 130. The choke 120 and the resistor 130 are connected in series.

[0037] The stator current control unit 102 is configured to generate a stator current, and the rotor current control unit 104 generates a rotor current. When the synchronous machine is deactivated, the stator current is impressed with a positive stator current value so that the rotor current or the rotor winding 110 is quickly de-energized, depending on the positive stator current value. The discharge resistor device 116 can optionally be additionally switched on during de-energization to cause a discharge current when a voltage of the stator current exceeds a threshold value.

[0038] Fig. Figure 2 shows a circuit diagram of an embodiment of a device 100 for a synchronous machine. The device 100 is similar or corresponds to the device of Fig. 1, except that only the stator current control unit 102, the rotor current control unit 104, and the discharge resistance device 116 are shown. The discharge resistance device 116 is connected between the stator current control unit 102 and the rotor current control unit 104 merely by way of example. In other words, Fig. 2, a power electronics system, wherein the stator current control unit 102 can also be referred to as stator power electronics, and the rotor current control unit 104 can be referred to as exciter power electronics. The discharge resistor device 116 can also be referred to as a switchable discharge resistor.

[0039] The stator current control unit 102 has the bridge circuit unit 106, which in Fig. 2, however, additionally has a further half-bridge 226. The further half-bridge 226 has a further switch 206 and an additional switch 216, wherein the switches 206, 216 are connected to each other via a further tapping point 203. The switches 146, 156, 166, 176, 206, 216 of the bridge circuit unit 106 are designed as MOSFET switches merely by way of example.

[0040] According to one embodiment, the discharge resistor device 116 comprises a switching device 236 and a discharge resistor 246, wherein the switching device 236 and the discharge resistor 246 are connected in series. The switching device 236 is connected to the stator current control unit 102 and the rotor current control unit 104 via a tapping point. The discharge resistor 246 is also connected to the stator current control unit 102 and the rotor current control unit 104 via another tapping point.

[0041] The rotor current control unit 104 has the further bridge circuit unit 108, but in Fig. 2 the switches 148, 158, 168, 178 are designed as transistors, merely as an example as MOSFET switches.

[0042] When the device 100 is in an operational state, an Id stator current and an Iq stator current flow through the stator current control unit 102. A rotor current, which can also be referred to as a lexc rotor current, flows in the rotor current control unit 104. The rotor current is designed to energize or drive at least one rotor winding of the synchronous machine. In certain situations, it is important that the rotor current is de-energized as quickly as possible, for example in the event of a fault in the synchronous machine and / or a load shedding of the battery. In this case, the synchronous machine is deactivated, for example. After the synchronous machine is deactivated, the rotor current is not de-energized immediately. The rotor current is completely de-energized when it has a current of zero amperes. The approach presented here enables fast and reliable de-energization of the rotor current using the Id stator current.After deactivation of the synchronous machine, a positive Id stator current value is applied to the stator current, which is higher than the Id stator current before deactivation. The higher or more positive the Id stator current is applied, the faster the rotor current is de-excited.

[0043] The discharge resistor device 116 can optionally be additionally controlled if, for example, during de-energization of the rotor current, a voltage in the stator current control unit 102 exceeds a threshold value, for example, a threshold value of 1000 volts. In this case, the discharge resistor device 116 causes a discharge current to protect the device 100 from damage. For this purpose, the discharge resistor device 116 has the switching device 236 and the discharge resistor 246, wherein the switching device 236 and the discharge resistor 246 are connected in series according to one embodiment. The switching device 236 is closed, so that the voltage from the stator current control unit 102 is applied to the discharge resistor 246. If the voltage from the stator current control unit 102 is below the threshold value, the switching device 236 remains open. Optionally, the discharge resistor device 116 additionally has a Zener diode.For example only, the discharge resistor device 116 additionally has a current measuring device 256 which is connected in series with the switching device 236 and the discharge resistor 246.

[0044] The current axes of an electrically excited synchronous machine exhibit very strong cross-coupling. The currents Id and lexc (= if) in particular have a very strong influence on the other axes and thus interact strongly. This is largely due to cross-coupling, but also due to saturation effects. The Iq current has a significantly lower cross-coupling effect, with a minor effect due to saturation. A significant change in lexc with an Id change is theoretically known. The influence of Iq on lexc depends on the operating point. A significant change in lexc occurs, for example, if an Iq change @Id=-100A. A slight change in lexc occurs, for example, if an Iq change @id=-300A. The influence of Idq on lexc depends on a change or gradient of a setpoint as well as on transient response, e.g., overshoot, controller parameters, decoupling, etc. u→x=R⋅i→x+ddtψ→x+ω⋅J⋅ψ→x(UdUqUexc)=(Rs000Rs000Rexc)(IdIqIexc)+(0−ω0ω00000)(ψdψqψexc)+ddt(ψdψqψexc)(ψdψqψexc)=(Ld0Lm0Lq032Lm0Lexc)(IdIqIexc)MLS=32zpIq(LmIexc+(Ld−Lq)Id)

[0045] In other words, the current axes of an electrically excited synchronous machine exhibit very strong cross-coupling. This means that the currents Id, Iq, and lexc have a very strong effect on each other's axes and thus interact strongly due to cross-saturation. The approach presented here exploits this effect. By injecting a positive Id stator current, the rotor current lexc is de-excited as quickly as possible, thereby bringing the electric drive into a safe state. In other words, active control injects a positive Id stator current with maximum dynamics. The steep +di / dt de-excites the rotor current to 0 amperes with maximum dynamics. This rapid de-excitation, i.e. setting the rotor current lexc to 0 amperes as quickly as possible, ensures that no further voltage is induced during rotating operation.The approach presented here concerns an electrically separately excited synchronous machine with a conductive exciter, i.e. with brushes, and with an inductive exciter, i.e. with a transformer.

[0046] This is advantageous in the event of an electric motor fault: This usually involves an active short circuit (ACS) with high phase currents, or an inverter lock (WRS), where all switches are open and voltage is induced. The first case can lead to an unacceptably high rotor current in an electrically separately excited synchronous machine and damage the windings, rotor winding, or rectifier diodes. The second case can lead to an unacceptably high DC voltage. This approach de-energizes the rotor very quickly and only subsequently switches it to WRS or ACS, thus preventing both of these types of damage.

[0047] During battery load shedding, the battery is disconnected from the drive system during rotating operation, the generator's cornerstone. In this case, the induced voltage can no longer be stabilized by the battery, and the intermediate circuit is protected from an impermissibly high DC voltage during inverter operation, for example, to protect the intermediate circuit capacitor, on-board electronics, etc. This approach avoids damaging effects in the intermediate circuit. In other words, the approach presented here de-energizes the rotor very quickly and subsequently switches it to inverter operation or auxiliary operation without causing any damage.

[0048] In other words, the approach presented here performs an active and dynamic adjustment of a positive Id current in order to de-excite the excitation current lexc = 0A through the cross-coupling effect, without additional expensive components.

[0049] The most critical operating point is the generator corner point, where power is fed into the battery, a high negative Id current is present, and the battery voltage is at its maximum. If battery load shedding occurs here, the stator control remains active and regulates the Id current to a high positive d-current, the Iq current to 0 amperes, and the exciter goes into AKS or WRS. Until the id current has changed sign, the voltage increase in the DC link is briefly discharged, for a maximum of two milliseconds, via a parallel discharge resistor to U_dc. As soon as the Id current is positive or the Iq current = 0 amperes, there is no longer any feedback and the DC link is no longer charged; the discharge resistor 246 can be disconnected again. The steep +di / dt gradient in the d-current also quickly de-excites the exciter.The trick is that you can even drive the d-current so far into the positive in order to have the largest possible positive di / dt, so that the exciter is really completely de-excited (I_exc=0A).

[0050] After rapid de-excitation, when U_zk slowly decreases, the d-current automatically decreases slowly toward 0 amperes, and the d-set current should also be 0 amperes. Since there is no steep gradient, the exciter current is not excited again. Thus, the primary goal of the approach presented here is to set the exciter current, i.e., the rotor current, to 0 amperes as quickly as possible and then maintain it in this state.

[0051] The advantage of the approach presented here is the rapid de-excitation of the rotor current, so that the electric motor is in a safe state. For this, no additional components are required for the rotor with a conductive exciter. For inductive exciters, only a Zener diode is required, see Fig. 4, and an additional standard diode. However, this is helpful anyway to protect the rotor. A combination of the discharge resistor and a semiconductor can also be used to conduct the short-circuit current, so no additional costs are incurred in this case. Since rapid de-excitation means the resistor only needs to conduct the current for a very short time in any fault situation, for a maximum of two milliseconds, the resistor can be designed inexpensively and simply.

[0052] In other words, the approach presented here enables cross-coupling of the axes for rotor de-excitation. The d-axis couples very strongly to the lexc excitation axis. By using a steep positive di / dt in the Id stator current axis, the excitation current can be completely de-excited.

[0053] The discharge resistor 246 is connected in hardware. This is done either by a MOSFET + comparator circuit or directly by a Zener diode. Both elements switch as soon as a critical voltage for the hardware components is reached, for example, 1000 volts, because at this voltage, components such as the capacitor would be damaged. The hardware circuit thus protects the components during the brief period when the Id current changes from negative to positive or rises. The greater the positive Id current gradient (di / dt), the faster the rotor current is discharged. The goal is to reduce the rotor current to 0 amperes as quickly as possible.

[0054] Fig. Figure 3 shows a diagram of a discharge resistance device 116 for an embodiment of a device. The discharge resistance device 116 is similar to or corresponds to the discharge resistance device of Fig. 1 and / or Fig. 2. More specifically, the discharge resistance device 116 corresponds to the discharge resistance device of Fig. 2.

[0055] In other words, Fig. 3 is necessary hardware. The additional discharge resistor 246 and the switching device 236 at U_zk carry the current only briefly, for a maximum of two milliseconds, because after that, the current indicator is switched from the generator to the motor mode, and then the energy flows from the U_zk into the stator winding. This is the difference from the actual U_zk discharge resistor in a permanent magnet synchronous machine, or PMSM for short. In a PMSM, the U_zk must be completely discharged, but here it only briefly limits the voltage peak. And because it only carries current for a very short time, it doesn't get as worn or overheated as in emergency mode.

[0056] Fig. Figure 4 shows a diagram of a diode circuit 400 for one embodiment of a device. The diode circuit 400 can be arranged in the device, for example, the rotor current control unit, by way of example only, and is designed to protect the additional bridge circuit unit of the rotor current control unit.

[0057] In other words, Fig. 4 for a special case of an inductive exciter, two additional diodes to protect the four rectifier diodes of the further bridge circuit device, see Fig. 1. A Zener diode is necessary to ensure that the current in the rotor current control unit also becomes negative as soon as the rotor voltage becomes too high. This wouldn't be a problem with a conductive exciter, since rotor current can flow negatively.

[0058] Fig. Figure 5 shows a diagram illustrating signal waveforms for explaining an embodiment of a device. More specifically, Fig. 5 shows the signal curves during de-energization of at least one rotor winding. In other words, Fig. 5 a fast de-excitation at 3000 revolutions per minute and an inductive coupling M of -100 Newton meters.

[0059] The time is plotted on the abscissa and the current in amperes on the ordinate. The ordinate is divided into two operating states 505, 510 merely for the purpose of example, with the temporal progressions of the operating states 505, 510 being represented by a double arrow. According to one exemplary embodiment, the first operating state 505, which may also be referred to as M-control, represents a state in which the device or the synchronous machine is in a normal state. In a normal state, the synchronous machine drives, for example, a motor vehicle, as is exemplified in Fig. 9. The second operating state 510, which can also be referred to as rotor-ACS, stator-controlled, represents a state in which de-excitation takes place or a state in which the Id stator current 515 is impressed with a positive value.

[0060] During the first operating state 505, the rotor current lexc 520 has a current of 10 amperes, for example only. The Id stator current 515 has a current of -30 amperes, and the Iq stator current 525 has a current of -150 amperes. When the synchronous machine is deactivated, the de-excitation of the rotor current 520 begins, which is indicated by a drop in the rotor current 520 from, for example, only 10 amperes to initially 5 amperes. In the second operating state 510, the Id stator current 515 is impressed to a positive value, here, for example, only to a value of 0 amperes. Depending on this, the rotor current 520 continuously decreases until it reaches a value of 0 amperes and is thus completely de-excited. In the second operating state 510, the Iq stator current 525 is also impressed to a positive value, here also to 0 amperes merely as an example.According to one embodiment, the Id stator current 515 and the Iq stator current 525 are simultaneously impressed to the same positive value, namely 0 amperes. Depending on the positively impressed Id stator current 525, the rotor current 520 is de-energized. Thus, the device is in a safe state, for example, after a fault in the synchronous machine.

[0061] Fig. Figure 6 shows a diagram illustrating signal waveforms to explain an embodiment of a device. The signal waveforms are similar to the signal waveforms of Fig. 5 with the difference that the Id stator current 515 is impressed to a different positive value.

[0062] According to one embodiment, the Id stator current 515 is impressed to a positive current of 140 amperes in the second operating state 510. Depending on this, the rotor current 520 is quickly de-energized, which results in Fig. 6 is illustrated by a significant drop in the current intensity of the rotor current 520 from, for example, 10 amperes to 0 amperes. Therefore, the higher the Id stator current 515 is impressed, the faster the rotor current 520 is de-energized.

[0063] Fig. Figure 7 shows a diagram illustrating signal waveforms to explain an embodiment of a device. The signal waveforms are similar to the signal waveforms from one of the Fig. 5 and / or 6. More precisely, Fig. 7 shows the signal curves during de-energization of at least one rotor winding. In other words, Fig. 7 a fast de-excitation at 1000 revolutions per minute and an inductive coupling M of 50 Newton meters.

[0064] In the first operating state 505, the rotor current 520 has, merely as an example, a current of 6 amperes, the Id stator current 525 has a current of -5 amperes, and the Iq stator current 525 has a current of 100 amperes. In the second operating state 510, the Id stator current 515 is regulated from -5 amperes to 0 amperes, whereby the rotor current 520 continuously drops to 0 amperes, i.e., is de-energized. The Iq stator current 525 is also regulated to 0 amperes at the same time as the Id stator current 515, with the Iq stator current 525 in particular being immediately regulated to 0 amperes.

[0065] Fig. Figure 8 shows a diagram illustrating signal waveforms to explain an embodiment of a device. The signal waveforms are similar to the signal waveforms of Fig. 7 with the difference that the Id stator current 525 is impressed to a different positive value.

[0066] According to one embodiment, the Id stator current 525 is impressed to a positive current of 140 amperes in the second operating state 510. Depending on this, the rotor current 520 is quickly de-energized, which results in Fig. 8 is illustrated by a significant drop in the current intensity of the rotor current 520 from, for example, 6 amperes to 0 amperes. Therefore, the higher the Id stator current 515 is impressed, the faster the rotor current 520 is de-energized.

[0067] Fig. 9 shows a schematic representation of an embodiment of a motor vehicle 900.

[0068] The motor vehicle 900 is shown with wheels 905, four wheels only by way of example, an electrical energy storage device 910, for example a battery, and an electric axle drive 915. The electric axle drive 915 comprises a power converter 920, a synchronous machine 925, and a transmission device 930.

[0069] Electrical energy for operating the synchronous machine 925 is provided by an energy supply device, here the electrical energy storage device 910. The electrical energy storage device 910 is designed to provide direct current, which is converted into an alternating current, for example a three-phase alternating current, using a power converter 920 of the electric axle drive 915 and provided to the synchronous machine 925. A shaft driven by the synchronous machine 925 is coupled directly or using the transmission device 930 to at least one wheel 905 of the motor vehicle 900. Thus, the motor vehicle 900 can be propelled using the synchronous machine 925. According to one exemplary embodiment, the electric axle drive 915 comprises a housing in which the power converter 920, the synchronous machine 925, and the transmission device 930 are arranged.

[0070] According to one embodiment, the power converter 920 comprises at least one device 100, as described with reference to the preceding figures. For example, the device 100 is arranged in an intermediate circuit of the power converter 920.

[0071] Fig. Figure 10 shows a flowchart of an embodiment of a method 1000 for operating a synchronous machine. The synchronous machine corresponds to or is similar to the synchronous machine from one of the figures described herein.

[0072] The method 1000 includes a step 1005 of impressing a stator current onto a stator current value. The stator current is impressed onto the stator current value such that an Id stator current value has a predefined, positive value after deactivation of the synchronous machine. The positive value is higher than the Id stator current before deactivation.

[0073] The exemplary embodiments described and shown in the figures are selected only as examples. Different exemplary embodiments can be combined with each other in their entirety or with regard to individual features. Furthermore, one exemplary embodiment can be supplemented by features of another exemplary embodiment.

[0074] Furthermore, method steps according to the invention can be repeated and carried out in a different order than that described.

[0075] If an embodiment comprises an “and / or” link between a first feature and a second feature, this can be read such that the embodiment according to one embodiment has both the first feature and the second feature and according to another embodiment has either only the first feature or only the second feature. Reference symbol 100 device 102 Stator current control unit 103 first tapping point 104 Rotor current control unit 106 Bridge circuit unit 108 additional bridge circuit units 110 Rotor winding 112 Transformer device 113 second tapping point 114 Filter device 116 Discharge resistance device 118 third half bridge 120 Rotor winding choke 122 first throttle 123 third energy storage 124 first supply voltage connection 126 first half bridge 128 fourth half-bridge 130 resistance 132 second throttle 133 third tapping point 134 second supply voltage connection 136 second half bridge 142 additional choke of the transformer device 143 fourth tapping point 144 energy storage 146 first switch 148 first diode 154 second energy storage 156 second switch 158 second diode 164 Throttle 166 third switch 168 third diode 174 more throttles 176 fourth switch 178 fourth diode 203 additional tapping point 206 additional switches 216 additional switches 226 further half bridges 236 Switching device 246 Discharge resistor 256 ammeter 400 diode circuit 505 first operating state 510 second operating state 515 Id stator current 520 rotor current 525 Iq stator current 900 motor vehicles 905 Wheel 910 electrical energy storage 915 electric axle drive 920 power converters 925 synchronous machine 930 Gearbox device 1000 methods for operating a synchronous machine 1005 Step of Memorization

Claims

[1] Device (100) for de-energizing at least one rotor winding (110) of an electrically separately excited synchronous machine (925), the device (100) having the following feature: a stator current control unit (102) configured to impress a stator current value onto a stator current such that a value of an Id stator current (515) after deactivation of the synchronous machine (925) has a predefined, positive value and is higher than the Id stator current (515) before deactivation. [2] Device (100) according to claim 1, wherein the stator current control unit (102) is designed to impress the stator current such that the value of the Id stator current (515) lies in a tolerance range of 50 percent of the maximum possible Id stator current value, in particular wherein the value of the Id stator current (515) is in a tolerance range of 10 percent of the maximum possible Id stator current value, in particular wherein the value of the Id stator current (515) is set to the maximum possible Id stator current value. [3] Device (100) according to one of the preceding claims, wherein the stator current control unit (102) is designed to impress a stator current value on the stator current such that a value of the Iq stator current (525) after deactivation of the synchronous machine (925) has a value of 0 amperes within a tolerance range. [4] Device (100) according to one of the preceding claims, comprising a rotor current control unit (104) which is designed to actively short-circuit a rotor current (520) of a rotor of the synchronous machine (925) after deactivation of the synchronous machine (925). [5] Device (100) according to one of the preceding claims, wherein the stator current control unit (102) is designed to activate an inverter blocking mode after deactivation of the synchronous machine (925). [6] Device (100) according to one of the preceding claims, comprising a discharge resistor device (116) connected between two terminals of an intermediate circuit of the synchronous machine (925) to cause a discharge current between the terminals of the intermediate circuit via a discharge resistor (246) when a voltage between the two terminals exceeds a threshold value. [7] Device (100) according to claim 6, wherein the discharge resistance device (116) is designed to suppress and / or prevent the discharge current when the voltage between the terminals falls below the threshold. [8] Device (100) according to one of claims 6 to 7, wherein the discharge resistance device (116) comprises a switching device (236) connected in series with the discharge resistance (246). [9] The device (100) according to claim 8, wherein the switching device (236) comprises a MOSFET semiconductor device and a comparator circuit, a thyristor, an IGBT and / or a Zener diode. [10] Electrically separately excited synchronous machine (925), with a device (100) according to one of claims 1 to 9, in particular wherein a rotor of the synchronous machine (925) is inductively or conductively electrically coupled or can be coupled or fed. [11] Power converter (920), in particular inverter, with a device (100) according to one of the preceding claims. [12] Electric axle drive (915) for a motor vehicle (900) with at least one synchronous machine according to claim 10, a transmission device (930) and a power converter (920) according to claim 11. [13] Motor vehicle (900) comprising an electric axle drive (915) according to claim 12 and / or a power converter (920) according to claim 11 and / or a device (100) according to one of claims 1 to 9. [14] Method (1000) for operating an electrically separately excited synchronous machine (925) according to claim 10, wherein the method (1000) comprises the following step: Impressing (1005) a stator current to a stator current value such that a value of an Id stator current (515) after deactivation of the synchronous machine (925) has a predefined, positive value that is higher than the Id stator current (515) before deactivation. [15] Computer program adapted to carry out and / or control the step of the method according to claim 14.

Images