PROTECTION DEVICE FOR A LOAD RESISTOR

Abstract

A protection device, for operating an electric machine at a converter, comprises a first and second conductor of a DC link, a switching device having a first and second switch, a link capacitor, a load resistor as a precharge and braking resistor, a semiconductor switch and an electrical fuse for protecting the load resistor. The electrical fuse and the first switch are connected in series to the first conductor and to a first resistor connection of the load resistor and to a first power connection of the semiconductor switch. The second switch is connected to the electrical conductor and to a first capacitor connection of the link capacitor and to a second resistor connection of the load resistor. The semiconductor switch is connected by a second power connection to the second conductor and the link capacitor is connected by a second capacitor connection to the second conductor.

Claims

1.-15. (canceled)

16. A protection apparatus of a converter for operating an electric machine, said protection apparatus comprising: a DC link including a first conductor and a second conductor; a switching apparatus having a first switch and second switch; a link capacitor; a load resistor functioning as a combination of a precharge resistor and a braking resistor; a semiconductor switch; and an electrical fuse for protecting the load resistor, wherein the electrical fuse and the first switch are electrically connected in series to the first conductor on one side of a series connection formed by the electrical fuse and the first switch, and electrically connected to a first resistor connection of the load resistor and to a first power connection of the semiconductor switch on another side of the series connection, wherein the second switch is electrically connected to the first conductor on one side of the second switch and to a first capacitor connection of the link capacitor and to a second resistor connection of the load resistor on another side of the second switch, and wherein the second conductor is electrically connected to a second power connection of the semiconductor switch and to a second capacitor connection of the link capacitor.

17. The protection apparatus of claim 16, further comprising an alternating circuit formed from the first switch and the second switch, wherein the first switch is closed when the second switch is open, or the first switch is open when the second switch is closed.

18. The protection apparatus of claim 16, further comprising a controller, said controller generating a control command for switching the first switch and the second switch.

19. The protection apparatus of claim 18, further comprising a first temperature detector arranged at the load resistor, said first temperature detector detecting a resistance temperature of the load resistor as a first temperature signal and transmitting the first temperature signal to the controller.

20. The protection apparatus of claim 18, further comprising a second temperature detector arranged at the semiconductor switch, said second temperature detector detecting a semiconductor temperature of the semiconductor switch as a second temperature signal and transmitting the second temperature signal to the controller.

21. The protection apparatus of claim 18, further comprising a voltage detector electrically connected to the first power connection and the second power connection of the semiconductor switch, said voltage detector detecting a semiconductor output voltage of the semiconductor switch as a voltage signal and transmitting the voltage signal to the controller.

22. The protection apparatus of claim 18, further comprising a current detector electrically connected in series either to the first power connection of the semiconductor switch or in series to the second power connection of the semiconductor switch, said current detector detecting a semiconductor output current of the semiconductor switch as a current signal and transmitting the current signal to the controller.

23. The protection apparatus of claim 18, further comprising an actuation detector detecting an actuation command for a control connection of the semiconductor switch as an actuation signal and transmitting the actuation signal to the controller.

24. A method for operating a protection apparatus as set forth in claim 16, said method comprising: opening the first switch of the switching apparatus and closing the second switch of the switching apparatus in fault-free regenerative operation of the converter when braking an electric machine by the load resistor and the semiconductor switch, or in fault-free motor operation of the converter when the electric machine is driven by the link capacitor; checking for a presence of or an expectation of an unintentional short circuit of the semiconductor switch in test operation; closing the first switch and opening the second switch in fault operation when the unintentional short circuit of the semiconductor switch is present or expected; and tripping the electrical fuse for protecting the load resistor in protective operation.

25. The method claimed of claim 24, further comprising switching the switches when the unintentional short circuit is present or expected by a switching command from a controller and a trigger signal for tripping the electrical fuse is generated.

26. The method of claim 24, further comprising determining the presence or expectation of the unintentional short circuit by a controller based on a resistance temperature of the load resistor.

27. The method of claim 24, further comprising determining the presence or expectation of the unintentional short circuit by a controller based on a semiconductor temperature of the semiconductor switch.

28. The method of claim 24, further comprising determining the presence or expectation of the unintentional short circuit by a controller based on an actuation command for a control connection of the semiconductor switch and a semiconductor output voltage of the semiconductor switch.

29. The method of claim 24, further comprising determining the presence or expectation of the unintentional short circuit by a controller based on an actuation command for a control connection of the semiconductor switch and a semiconductor output current of the semiconductor switch.

30. A converter, comprising: a protection apparatus operated by a method set forth in claim 24 for operating an electric machine, said protection apparatus comprising a DC link including a first conductor and a second conductor, a switching apparatus including a first switch and second switch, an link circuit capacitor, a load resistor functioning as a combination of a precharge resistor and a braking resistor, a semiconductor switch, and an electrical fuse for protecting the load resistor, wherein the electrical fuse and the first switch are electrically connected in series to the first conductor on one side of a series connection, and electrically connected to a first resistor connection of the load resistor and to a first power connection of the semiconductor switch on another side of the series connection, wherein the second switch is electrically connected to the first conductor on one side of the second switch and to a first capacitor connection of the link capacitor and to a second resistor connection of the load resistor on another side of the second switch, and wherein the second conductor is electrically connected to a second power connection of the semiconductor switch and to a second capacitor connection of the link capacitor; said converter being configured to operate the electric machine on an electrical network, wherein in the protective operation, the regenerative or motor operation of the converter and precharging of the link capacitor of the protection apparatus are blocked by the protection apparatus after the electrical fuse has been tripped.

Description

[0045] The properties, features and advantages of this invention described above, and the manner in which they are achieved, will become clearer and more readily comprehensible in connection with the following description of the exemplary embodiments which are described in more detail in connection with the figures, in which:

[0046] FIG. 1 shows a first schematic representation of a protection apparatus according to the invention,

[0047] FIG. 2 shows a second schematic representation of the protection apparatus according to FIG. 1 with a controller,

[0048] FIG. 3 shows a structure chart of a method for the operation of the protection apparatus according to FIG. 1 or FIG. 2 and

[0049] FIG. 4 shows a schematic representation of a converter with a protection apparatus and a method for the protection apparatus, it being possible to operate an electric machine on an electrical network by means of the converter.

[0050] FIG. 1 shows a first schematic representation of a protection apparatus 1 according to the invention.

[0051] A DC voltage intermediate circuit 2 has a first conductor 4 and a second conductor 5.

[0052] An electrical fuse 12 and a first switch 7 of a switching apparatus 6 are electrically connected in series to the first conductor 4 on one side and to a first resistor connection 13 of a load resistor 10 and to a first power connection 14 of a semiconductor switch 11 on the other side.

[0053] A second switch 8 is electrically connected to the first conductor 4 on one side and to a first capacitor connection 15 of an intermediate circuit capacitor 9 and to a second resistor connection 16 of the load resistor 10 on the other side.

[0054] The semiconductor switch 11 is electrically connected to the second conductor 5 by means of a second power connection 17, and the intermediate circuit capacitor 9 is electrically connected to the second conductor 5 by means of a second capacitor connection 18.

[0055] To precharge the intermediate circuit capacitor 9, as shown in FIG. 1, the first switch 7 of the switching apparatus 6 is closed and the second switch 8 of the switching apparatus 6 is open. The intermediate circuit capacitor 9 can be precharged via the DC voltage intermediate circuit 2, the first conductor 4, the closed first switch 7, the electrical fuse 12, the load resistor 10, the intermediate circuit capacitor 9 and the second conductor 5.

[0056] In the case of regenerative or motor operation of the protection apparatus 1, the first switch 7 of the switching apparatus 6 is open and the second switch 8 of the switching apparatus 6 is closed (switching states are not shown in FIG. 1). In regenerative operation, the electrical energy from the DC voltage intermediate circuit 2 can be converted into thermal energy via the first conductor 4, the closed second switch 8 (closed switching state not shown in FIG. 1), the load resistor 10, the semiconductor switch 11 and the second conductor 5 by means of the load resistor 10 and the semiconductor switch 11 at the load resistor 10.

[0057] It is also possible to feed electrical energy into the intermediate circuit capacitor 9 in regenerative operation, provided its charging capacity still makes this possible, this being performed via the first conductor 4, the closed second switch 8 (closed switching state not shown in FIG. 1), the intermediate circuit capacitor 9 to be charged and the second conductor 5.

[0058] The motor operation of the protection apparatus 1 likewise takes place via the closed second switch 8 (closed switching state in FIG. 1 not shown). The intermediate circuit capacitor 9 electrically connected in this way to the DC voltage intermediate circuit 2 then ensures, inter alia, that the level of the DC voltage is as constant as possible and is smoothed.

[0059] FIG. 2 shows a second schematic representation of the protection apparatus 1 according to FIG. 1.

[0060] A controller 19 can generate a control command 20 by means of which the first switch 7 and the second switch 8 of the switching apparatus 6 can be switched.

[0061] A resistance temperature 22 of the load resistor 10 can be detected by means of a first temperature detector 21 and can be transmitted to the controller 20 as a first temperature signal.

[0062] A semiconductor temperature 24 of the semiconductor switch 11 can be detected by means of a second temperature detector 23 and can be transmitted to the controller 20 as a second temperature signal.

[0063] A semiconductor output voltage 26 of the semiconductor switch 11 can be detected by means of a voltage detector 25, connected to a first and a second power connection 14,17 of the semiconductor switch 11, and can be transmitted to the controller 20 as a voltage signal.

[0064] By means of a current detector 27, which is electrically connected in series to the first power connection 14 of the semiconductor switch 11, between the first power connection 14 of the semiconductor switch 11 and the second conductor 5, a semiconductor output voltage 26 of the semiconductor switch 11 can be detected and transmitted to the controller 20 as a voltage signal.

[0065] FIG. 3 shows a structure chart of a method 42 for operating the protection apparatus 1 according to FIG. 1 or FIG. 2.

[0066] In fault-free regenerative operation 37 of a converter, when braking an electric machine by means of the load resistor and the semiconductor switch or in fault-free motor operation 38 of the converter, when the electric machine is driven by means of the intermediate circuit capacitor, the first switch 7 of the switching apparatus 6 is open and the second switch 8 of the switching apparatus 6 is closed.

[0067] In test operation 39, the semiconductor switch 11 is checked for the presence 40 or expectation 29 of an unintentional short circuit 41 both in regenerative operation 37 and in motor operation 38.

[0068] In fault operation 35, in the presence 40 or expectation 29 of the unintentional short circuit 41 of the semiconductor switch 11, the first switch 7 is closed and the second switch 8 is opened.

[0069] In protective operation 36, the electrical fuse 12 for protecting the load resistor is tripped.

[0070] When the unintentional short circuit 41 is present 40 or expected 29, the switches 7,8 are switched by means of the switching command 20 from the controller 19. A trigger signal 43 for tripping the electrical fuse 7 is generated by the controller 19.

[0071] FIG. 4 visualizes a schematic representation of a converter 3 with a protection apparatus 1 and a method 42 for the protection apparatus 1.

[0072] An electric machine 33 can be operated on an electrical network 34 by means of the converter 3. The electrical connections of the converter to the electrical network 34 and the electric machine 33 are shown here, by way of example, by means of three-phase conductor systems.

[0073] In protective operation 36, the regenerative or motor operation 37,38 of the converter 3 and the precharging of the intermediate circuit capacitor of the converter can be blocked by means of the protection apparatus 1 after the electrical fuse 12 has been tripped.