DETERMINING THE REMAINING USABILITY OF A SEMICONDUCTOR MODULE IN NORMAL USE

Abstract

A method for determining the remaining usability of a semiconductor module in normal use. The semiconductor module is thermally coupled to a cooling device. A predefined electrical load is applied to the semiconductor module while predefined cooling is effected by the cooling device. A temperature of a semiconductor element of the semiconductor module is sensed at least for the predefined electrical load on the semiconductor module. The sensed temperature is compared with a comparison temperature in a first comparison. The comparison temperature is assigned to the predefined electrical load with the predefined cooling, and prediction data for the remaining usability of the semiconductor module in normal use up to a usability end are determined at least in accordance with the first comparison.

Claims

1.-14. (canceled)

15. A method for determining a remaining usability of at least one semiconductor module in normal use comprising: connecting an energy converter to an electric machine; electrically coupling the electric machine to a d.c. link with the energy converter, thermally coupling the at least one semiconductor module to a cooling device; electrically coupling at least one energy store to the at least one semiconductor module; switching the at least one semiconductor module in a predefinable switching mode to electrically couple the d.c. link to the electric machine; controlling the electric machine in accordance with a vector controller and setting an exclusively field-forming current in respect of the electric machine as a predefinable electrical load; applying a predefined electrical load comprising predefined switching patterns with a predetermined voltage stress and/or current stress to the at least one semiconductor module in normal operation while effecting a predefined cooling by the cooling device; sensing an electrical load of the at least one semiconductor module and cooling during normal operation; sensing a temperature of a semiconductor element of the at least one semiconductor module at least for the predefined electrical load of the at least one semiconductor module; comparing as soon as the predefined electrical load during the predefined cooling is determined, the sensed temperature with a comparison temperature assigned to the predefined electrical load while the predefined cooling is effected in a first comparison; and determining prediction data for the remaining usability of the at least one semiconductor module as a function of the first comparison.

16. The method as claimed in claim 15, further comprising: determining a thermal resistance between the at least one semiconductor element and the cooling device; comparing the determined thermal resistance with a thermal reference resistance in a second comparison; and additionally determining the prediction data as a function of the second comparison.

17. A method for determining a remaining usability of at least one semiconductor module in normal use comprising: connecting an energy converter to an electric machine; electrically coupling the electric machine to a d.c. link with the energy converter; thermally coupling the at least one semiconductor module to a cooling device; electrically coupling at least one energy store to the at least one semiconductor module; switching the at least one semiconductor module in a predefinable switching mode to electrically couple the d.c. link to the electric machine; controlling the electric machine in accordance with a vector controller and setting an exclusively field-forming current in respect of the electric machine as a predefinable electrical load; applying a predefined electrical load comprising predefined switching patterns with a predetermined voltage stress and/or current stress to the at least one semiconductor module in normal operation while effecting a predefined cooling by the cooling device; sensing an electrical load of the at least one semiconductor module and cooling during normal operation; determining a thermal resistance between a semiconductor element of the at least one semiconductor module and the cooling device; comparing as soon as the predefined electrical load during the predefined cooling is determined, the determined thermal resistance with a thermal reference resistance in a second comparison; and determining prediction data for the remaining usability of the at least one semiconductor module as a function of the second comparison.

18. The method of claim 15 further comprising: storing the temperature sensed in respect of the predefined load during the predefined cooling.

19. The method of claim 17 further comprising: storing the determined thermal resistance.

20. The method of claim 18 further comprising: documenting due to the storage an aging of the semiconductor module and increasing a cooling function based on aging effects.

21. The method of claim 19 further comprising: documenting due to the storage an aging of the semiconductor module and increasing a cooling function based on aging effects.

22. The method of claim 15 further comprising: determining the prediction data before an end of usability for the usability of the semiconductor module in normal use is reached.

23. The method of claim 17 further comprising: determining the prediction data before an end of usability for the usability of the semiconductor module in normal use is reached.

24. The method of claim 15 further comprising: displaying the end of usability in an event of a difference between the sensed temperature and the comparison temperature is greater than a predefined reference value.

25. The method of claim 17 further comprising: displaying the end of usability in an event of a difference between a difference between the determined thermal resistance and the thermal reference resistance is greater than a predefined reference value.

26. The method of claim 15 further comprising: outputting a load signal to set a maximum load of the at least one semiconductor module as a function of a difference between the sensed temperature and the comparison temperature.

27. The method of claim 17 further comprising: outputting a load signal to set a maximum load of the at least one semiconductor module as a function of a difference between the determined thermal resistance and the thermal reference resistance.

28. The method of claim 15 further comprising: externally setting the field-forming current to normal operation of the electric machine.

29. The method of claim 17 further comprising: externally setting the field-forming current to normal operation of the electric machine.

30. A control unit for controlling at least one semiconductor module thermally coupled to a cooling device, wherein the control unit is configured to carry out the method of claim 15.

31. A control unit for controlling at least one semiconductor module thermally coupled to a cooling device, wherein the control unit is configured to carry out the method of claim 17.

32. An energy converter for connection to an electric machine, said energy converter comprising: at least one semiconductor module; at least one cooling device thermally coupled to the at least one semiconductor module; at least one energy store electrically coupled to the at least one semiconductor module; connection contacts for connection of the electric machine; a d.c. link terminal for connecting the energy converter to a d.c. link; and a control unit of claim 30 electrically coupled to the at least one semiconductor module for controlling the at least one semiconductor module in a predefinable switching mode, in order to electrically couple the d.c. link and the electric machine to one another.

33. An energy converter for connection to an electric machine, said energy converter comprising: at least one semiconductor module; at least one cooling device thermally coupled to the at least one semiconductor module; at least one energy store electrically coupled to the at least one semiconductor module; connection contacts for connection of the electric machine; a d.c. link terminal for connecting the energy converter to a d.c. link; and a control unit of claim 31 electrically coupled to the at least one semiconductor module for controlling the at least one semiconductor module in a predefinable switching mode, in order to electrically couple the d.c. link and the electric machine to one another.

Description

[0049] Further features, advantages and effects emerge from the following exemplary embodiment on the basis of the figures. In the figures the same reference characters designate the same features and functions, wherein:

[0050] FIG. 1 shows a schematic circuit diagram of a drive device with an asynchronous motor connected to a power inverter,

[0051] FIG. 2 shows a schematic sectional representation of an IBGT module arranged on a heat sink in a schematic sectional view, and

[0052] FIG. 3 shows a schematic diagrammatic representation for a predefined electrical load of the IGBT module in accordance with FIG. 2 and of corresponding temperatures, and

[0053] FIG. 4 shows a schematic flowchart for an inventive procedure.

[0054] FIG. 1 shows a schematic circuit diagram of a drive device 10 having a power inverter 14 as an energy converter, which comprises three terminal contacts 46 for connecting a three-phase asynchronous machine 12. The asynchronous machine 12 comprises the phases U, V, W. The power inverter 14 further comprises terminal contacts 48, via which it is connected to a d.c. link 16 which has an intermediate circuit capacitor 18. The terminal contacts 48 form a d.c. link terminal.

[0055] The power inverter 14 has IGBT modules 24 as semiconductor modules or switching elements, which in a known manner are connected in pairs in series circuits, the central terminals 50 of which are connected to the corresponding terminal contacts 46.

[0056] The power inverter 14 further comprises a control unit 22 which provides switching signals for the IGBT modules 24, so that this is operated in switching mode. This means the asynchronous machine 12 can be coupled to the d.c. link 16 in a predefinable manner.

[0057] Also connected to the control unit 22 is a display unit 30, via which operating parameters and current operating data of the drive device 10, in particular of the power inverter 14, can be displayed.

[0058] FIG. 2 shows a schematic mechanical structure of one of the IGBT modules 24, as is used in the power inverter 14 in accordance with FIG. 1. The representation in FIG. 2 is a sectional representation. It can be seen that the IGBT module 24 has a housing 52 which comprises a mounting plate 26. The mounting plate 26 is in this case connected to a connection surface 54 of a heat sink 20, which provides a cooling device. A predefined cooling is achieved by the heat sink 20.

[0059] To achieve as good heat dissipation as possible in respect of the IGBT module 24, the mounting plate 26 and the connection surface 54 are embodied as adapted to one another. This means a particularly favorable or small thermal transfer resistance can be achieved. The mounting plate 26 thus provides a cooling surface.

[0060] A semiconductor element 28 is attached to the inside of the housing on the mounting plate 26 above a layer structure not shown in greater detail. The layer structure serves for the thermal and mechanical connection of the semiconductor element 28 to the mounting plate 26.

[0061] The semiconductor element 28 provides the actual IGBT. A predefined thermal transfer resistance is provided in respect of the semiconductor element 28 and the mounting plate 26.

[0062] It can further be seen that the semiconductor element 28 has, opposite the mounting plate 26, contact surfaces 32 which by means of a known bonding are connected to corresponding connection contacts (not shown) of the IGBT module 24. In this way a mechanical connection and a corresponding electrical connection can be achieved.

[0063] In order now to be able to determine the remaining usability of the IGBT module 24 in normal use, both the cooling by the heat sink 20 and the electrical load of the IGBT modules 24 are monitored. If a predefined electrical load in accordance with the graph 34 (FIG. 3) is determined, at the same time the corresponding temperatures of the semiconductor elements 28 of the semiconductor modules 24 are sensed in accordance with graph 36 (FIG. 3). A comparison temperature in accordance with the graph 40 was previously already determined for the predefined electrical load in accordance with the graph 34.

[0064] In a comparison carried out by the control unit 22, the sensed temperature in accordance with the graph 36 is compared to the comparison temperature in accordance with the graph 40. As a function of the comparison, prediction data (FIG. 4) is then determined, which is processed by the display unit 30, such that the display unit 30 indicates the remaining usability as a remaining usability period.

[0065] In the present case for the IGBT modules 24 the temperature is determined by measuring the threshold voltage of the IGBT modules 24. As is known, this voltage is a function of the temperature of the respective semiconductor chips, such that the actual temperatures of the semiconductor elements 28 can be determined from the determined values of said voltage. In the present case the prediction data 44 (FIG. 4) is thus a function of a difference between the sensed temperature in accordance with the graph 36 and the comparison temperature in accordance with the graph 40. The comparison temperature can be determined using models, statistical evaluation methods and laboratory trials.

[0066] It can further be seen in FIG. 3 how the sensed temperature behaves if the cooling by the cooling device, here the heat sink 20, is disrupted, because for example an air filter is clogged or the like. This is illustrated on the basis of the graph 38. It can be seen that in this case a rate of increase is smaller than represented with the graph 36. This means the control unit 22 can recognize whether cooling by the heat sink 20 is still sufficient or has even been disrupted. The control unit 22 can thus distinguish this from the prediction data 44 attributable to aging.

[0067] FIG. 3 shows a schematic diagrammatic representation in which the abscissa is assigned to the time in seconds. A left-hand ordinate is assigned to the temperature in degrees Celsius and a right-hand ordinate to the power in watts. A graph 34 represents the predefined electrical load of a respective one of the IGBT modules 24. It can be seen that the predefined electrical load primarily comprises two square-wave pulses, wherein the chronologically first square-wave pulse is a comparatively chronologically short-duration square-wave pulse with a power of approximately 300 watts. This is followed after a brief power break by a second square-wave pulse which extends over a period of approximately 160 s and provides a power of approximately 500 W. This predefined electrical load results in a temperature of the semiconductor element 28 of the IGBT module 24 in accordance with the graph 36.

[0068] The corresponding comparison temperature for such a load for an IGBT module 24 which is in mint condition emerges on the basis of the graph 40. It can be seen that as aging increases the interval between the graphs 36 and 40 becomes larger. If a predefined maximum interval between the graphs 36 and 40 is achieved or exceeded, this is determined as an end of usability. The remaining normal usability can thus be inferred or predicted from the difference or the interval between the graphs 36 and 40. For this purpose the control unit 22 comprises an evaluation unit (not shown in greater detail), which uses statistical methods to determine the remaining normal usability and provides a corresponding message as a signal for the display unit 30. This evaluates the signal provided and provides a corresponding output of information for a user.

[0069] FIG. 4 shows a schematic flowchart for the process of the inventive method. The method starts at step 56. A predefined electrical load is sensed in the corresponding step 34. In step 36 the temperature of the IGBT modules 24 is then sensed at the same time. The sensed temperature is then compared in a comparison step 42 with the comparison temperature 40. In the following step 44 the prediction data is then determined as a function of the comparison. The method ends in step 58.

[0070] With the invention a system operator of the drive device 10 can be more reliably warned that a power semiconductor, here of one of the IGBT modules 24, may fail in the near future. Thus corresponding maintenance can be planned in good time, such that extensive damage and lengthy downtimes of the power inverter 14 can be avoided. Because the failure of one of the IGBT modules 24 can be identified in good time, more extensive further damage to the drive device 10, in particular at the power inverter 14, can be largely avoided.

[0071] The present exemplary embodiment serves solely to explain the invention and should not limit said invention.