Method for detecting a fault in a cooling system of a power semiconductor module and power electronics

Abstract

The invention relates to a method for detecting a fault in a cooling system (2) of a power semiconductor module (1), in particular for a vehicle traction motor, wherein a time course of a module temperature (T) is recorded with a temperature sensor (3) arranged inside the power semiconductor module (1), where a module temperature gradient is determined based on the time course, where the module temperature gradient is compared with a predetermined critical module temperature gradient and a fault is detected as soon as the specified module temperature gradient reaches or exceeds the predetermined critical module temperature gradient. Furthermore, the invention relates to power electronics.

Description

[0001] The invention relates to a method for detecting a fault in a cooling system of a power semiconductor module, in particular for a vehicle traction motor. Furthermore, the invention relates to power electronics, in particular for a vehicle traction motor.

[0002] Traction motors in modern vehicles incorporate power electronics to effectively and situation-specifically convert electrical voltages and currents from an energy source. Depending on the operating state of the traction motor, the power electronics can be subject to significant thermal stress. Therefore, in addition to a power semiconductor module, the traction motor also features a cooling system for efficient heat dissipation from the power semiconductor module. If the coolant pump fails or loses performance, or if coolant is lost in the cooling system, for example, due to a leak, the coolant flow rate may be insufficient. As a result, too little heat can be dissipated from the power electronics.In extreme cases, heat dissipation performance can approach zero, resulting in a rapid increase in the junction temperature and thus irreversible damage or even total failure of the power electronics. Therefore, providing a sufficient coolant flow rate to cool the power electronics is essential.

[0003] In the prior art, the speed of the coolant pump is usually monitored to ensure a sufficiently large coolant flow rate. However, this prior art has the disadvantage that in the event of a malfunction in the cooling system, particularly a leak, the speed of the coolant pump remains unchanged, thus creating the impression that sufficient coolant is being supplied to the power electronics for cooling.

[0004] Against this background, the task arises to provide an optimized method for detecting a fault in the cooling system of a power electronics system.

[0005] The object is achieved by a method for detecting a fault in a cooling system of a power semiconductor module, in particular for a vehicle traction machine, wherein a temporal progression of a module temperature is recorded by a temperature sensor arranged within the power semiconductor module, where a module temperature gradient is determined based on the time course, wherein the module temperature gradient is compared with a predetermined critical module temperature gradient and a fault is detected as soon as the determined module temperature gradient reaches or exceeds the predetermined critical module temperature gradient.

[0006] According to the invention, a temporal profile of a module temperature is recorded by a temperature sensor arranged within the power semiconductor module. Using a temperature sensor arranged within the power semiconductor module, the module temperature at the location of heat generation can be determined and any overheating can be detected. From this, direct conclusions can be drawn about a possibly insufficient coolant volume flow. Furthermore, a module temperature gradient is determined based on the temporal profile. Gradient in the sense of the invention can refer to a temporal derivative / change. The module temperature gradient is compared with a predetermined critical module temperature gradient, and a fault is detected as soon as the determined module temperature gradient reaches or exceeds the predetermined critical module temperature gradient.In particular, the critical module temperature gradient has a value that is smaller than the value of a gradient determined by means of a temporal progression of a junction temperature of the power electronics.

[0007] With a temperature sensor located within the power semiconductor module, in the event of a complete failure or a significantly reduced coolant flow rate, for example, due to a leak in the cooling system, the advantage can be achieved that a module temperature increase and thus an increase in the module temperature gradient can be detected much more quickly, particularly due to the proximity of the temperature sensor to the heat-generating power semiconductor module. Furthermore, the advantage extends to the fact that an increase in the module temperature or the module temperature gradient occurs directly through temperature measurement rather than indirectly via monitoring the speed of the coolant pump. This eliminates the need to draw conclusions.

[0008] According to a preferred embodiment of the invention, after the fault is detected, a safety mechanism is triggered, in particular the power semiconductor module is operated at reduced power, in particular depending on the module temperature determined by the temperature sensor, or the power semiconductor module is shut down. By triggering a safety mechanism, the power electronics can be protected from damage, in particular by preventing overheating of the power semiconductor module.

[0009] In an advantageous embodiment of the invention, the power semiconductor module has a coolant channel through which a coolant of the cooling system flows. A coolant channel can have one or more bent or kinked sections to increase the flow or residence time of the coolant. The power semiconductor module can, in particular, have multiple coolant channels. Furthermore, the power semiconductor module can be flowed through unidirectionally or, in particular with multiple coolant channels, bidirectionally or multidirectionally, in particular in two opposite directions in the sense of a counterflow heat exchanger.

[0010] A preferred embodiment of the invention provides that the coolant is water or a mixture comprising water and glycol. The advantages of water or water-glycol mixtures are their easy availability, non-toxic properties, and a sufficiently high specific heat capacity of water, combined with cost-effective procurement.

[0011] In a further preferred embodiment of the invention, the predetermined critical module temperature gradient is determined in advance experimentally or derived from a model. To increase safety, particularly against overheating of the power semiconductor module, a critical module temperature gradient derived from a model can be confirmed experimentally / empirically. A value for the critical module temperature gradient is, for example, 4 K / s, 6 K / s, 8 K / s, or 10 K / s.

[0012] A further subject of the invention is a power electronics system, in particular for a vehicle traction machine, comprising a power semiconductor module and a cooling system for cooling the power semiconductor module, where a temperature sensor is arranged within the power semiconductor module to detect a temporal progression of a module temperature, wherein the power electronics comprises an evaluation unit which is configured to to determine a module temperature gradient based on the time course, to compare the determined module temperature gradient with a given critical module temperature gradient and to detect a fault as soon as the specific module temperature gradient reaches or exceeds the specified critical module temperature gradient.

[0013] The advantages and technical effects explained in the context of the method according to the invention and its embodiments also apply individually or in combination to the power electronics according to the invention.

[0014] According to a preferred embodiment of the invention, the temperature sensor is arranged on a carrier substrate of the power semiconductor module, in particular on a direct bonded copper (DBC) carrier substrate. The temperature sensor can be arranged directly on the carrier substrate. Furthermore, the temperature sensor can be arranged on a copper track formed on the carrier substrate and thus indirectly on the carrier substrate. The advantage of a DBC carrier substrate is faster detection of a temperature increase, in particular due to the good / high thermal conductivity of copper. By quickly detecting a temperature increase, a safety mechanism can be quickly initiated or triggered. Thus, a reduced coolant volume flow or a total failure of the coolant volume flow can be quickly detected, and overheating of the power semiconductor module or the power electronics can be effectively prevented.

[0015] In an advantageous embodiment of the invention, it is provided that the power semiconductor module has a coolant channel through which a coolant of the cooling system flows.

[0016] Further details and advantages of the invention will be explained below with reference to the exemplary embodiment illustrated in the drawings. Herein: Fig. 1 shows a temporal progression of a module temperature recorded by a temperature sensor arranged within a power semiconductor module within the scope of a method according to the invention; Fig. 2a schematically shows an embodiment of a power semiconductor module of a power electronics system according to the invention in a regular operation of a cooling system of the power electronics; and Fig. 2b schematically shows the power semiconductor module from the Fig. 2a in operation of the cooling system with reduced coolant volume flow.

[0017] In Fig. 1 shows a temporal profile of a module temperature T recorded within the scope of a method according to the invention using a temperature sensor 3 arranged within a power semiconductor module 1. The method according to the invention for detecting a fault in a cooling system 2 of the power semiconductor module 1, in particular for a vehicle traction machine, first records the temporal profile of the module temperature T using the temperature sensor 3 arranged within the power semiconductor module 1. A module temperature gradient is then determined based on the temporal profile. Furthermore, the module temperature gradient is compared with a predetermined critical module temperature gradient, and a fault is detected as soon as the determined module temperature gradient reaches or exceeds the predetermined critical module temperature gradient.

[0018] In the Fig. 1, the temporal progression of the module temperature T is a monotonically rising curve, i.e., the module temperature T either rises or remains constant over time as time progresses. At time zero, the module temperature gradient calculated from the module temperature T at time zero, i.e., for T(t = 0s), has a value of approximately 3.75 K / s. In this initial section, which can be regarded as the start-up section of the power semiconductor module 1 and thus of the vehicle traction machine, the module temperature T rises steadily for approximately 15 seconds. For a further 25 seconds, the power semiconductor module 1 is in a steady state, i.e., the module temperature T does not change. Therefore, the time period t = 15s to t = 40s can be described as a regular operating state of the power semiconductor module 1, which will be discussed further in Fig. 2a is entered. After forty seconds, Fig. 1 leads to a malfunction in the cooling system 2, whereupon the coolant volume flow V for cooling the power semiconductor module 1 decreases from approximately 10 L / min to approximately 0.5 L / min. As a result, the module temperature T and the module temperature gradient increase, with the module temperature gradient at time t = 40 s amounting to a value of approximately 8 K / s.

[0019] In the Fig. 2a schematically shows an embodiment of a power semiconductor module 1 of a power electronics 10 according to the invention in a regular operation of a cooling system 2 of the power electronics 10. The power electronics 10, in particular for a vehicle traction machine, comprises the power semiconductor module 1 and the cooling system 2. Within the power semiconductor module 1, a temperature sensor 3 is provided for detecting the - in the Fig. 1 - temporal course of a module temperature T. The power electronics 10 also has a Fig. 2a, which is configured to determine a module temperature gradient based on the time course, to compare the determined module temperature gradient with a predetermined critical module temperature gradient and to detect a fault as soon as the determined module temperature gradient reaches or exceeds the predetermined critical module temperature gradient.

[0020] The power semiconductor module 1 according to the Fig. The embodiment shown in Figure 2a comprises three semiconductor components 5 arranged on a DBC (direct bonded copper) carrier substrate 8, which generate heat during operation. During normal operation, a large part of the heat is dissipated from the power semiconductor module 1 by means of the cooling system 2, which comprises a heat sink 6 and a cooling structure 7. To provide a cooling power Q, the cooling structure 7 can be Fig. 2a have invisible coolant channels. A smaller portion of the generated heat can be dissipated via the DBC carrier substrate 8. Furthermore, the power semiconductor module 1 has a lead frame 9 for electronically contacting the semiconductor components 5.

[0021] In Fig. 2b is a schematic view of the power semiconductor module 1 from the Fig. 2a in an operation of the cooling system 2 with reduced coolant volume flow V. Due to the reduced coolant volume flow V, which can occur, for example, as a result of a leak in the cooling system 2, there is a reduced cooling capacity Q via the cooling structure 7 and thus via the cooling system 2. Compared to the regular operation from the Fig.2a, increased heat is dissipated via the DBC carrier substrate 8, resulting in an increase in the module temperature T. The temperature sensor 3, which is arranged on the DBC carrier substrate 8, records the increase and thus detects a fault. As a result, a safety mechanism is triggered to prevent damage to the power semiconductor module 1 or the power electronics 10. For example, the power semiconductor module can be operated according to a derating strategy with reduced switching activity and / or reduced power. List of reference symbols 1 power semiconductor module 2 Cooling system 3 Temperature sensor 5 Semiconductor component 6 heat sinks 7 Cooling structure 8 Carrier substrate 9 connection frame 10 Power electronics T module temperature Q̇ cooling capacity V coolant volume flow

Claims

[1] Method for detecting a fault in a cooling system (2) of a power semiconductor module (1), in particular for a vehicle traction machine, wherein a temporal progression of a module temperature (T) is recorded by a temperature sensor (3) arranged within the power semiconductor module (1), where a module temperature gradient is determined based on the time course, wherein the module temperature gradient is compared with a predetermined critical module temperature gradient and a fault is detected as soon as the determined module temperature gradient reaches or exceeds the predetermined critical module temperature gradient. [2] Method according to claim 1, characterized bythat after the fault is detected, a safety mechanism is triggered, in particular the power semiconductor module (1) is operated with reduced power, in particular depending on the module temperature (T) determined by the temperature sensor (3), or the power semiconductor module (1) is switched off. [3] Method according to one of the preceding claims, characterized by that the power semiconductor module (1) has a coolant channel through which a coolant of the cooling system (2) flows. [4] Method according to one of the preceding claims, characterized by that the coolant is water or a mixture comprising water and glycol. [5] Method according to one of the preceding claims, characterized by that the specified critical module temperature gradient is determined in advance experimentally or derived from a model. [6] Power electronics (10), in particular for a vehicle traction machine, comprising a power semiconductor module (1) and a cooling system (2) for cooling the power semiconductor module (1), characterized by that a temperature sensor (3) for detecting a temporal progression of a module temperature (T) is arranged within the power semiconductor module (1), wherein the power electronics (10) comprises an evaluation unit which is designed to to determine a module temperature gradient based on the time course, to compare the determined module temperature gradient with a given critical module temperature gradient and to detect a fault as soon as the specific module temperature gradient reaches or exceeds the specified critical module temperature gradient. [7] Power electronics (10) according to claim 6, characterized bythat the temperature sensor (3) is arranged on a carrier substrate (8) of the power semiconductor module, in particular on a direct bonded copper carrier substrate, DBC carrier substrate. [8] Power electronics (10) according to one of claims 6 or 7, characterized by that the power semiconductor module (1) has a coolant channel through which a coolant of the cooling system (2) flows.

Images