A method for evaluating at least one part of an electric vehicle component, and a system for evaluating at least one part of an electric vehicle component

Abstract

A method (200) and a system (400) for evaluating at least one part (404) of an electric vehicle component (401) are presented.The method comprises:- applying (210) a physical vibration to the electric vehicle component (401), wherein the physical vibration is provided by a vibration arrangement (410);- running (230) an electric current (l) through at least one part (404) of the electric vehicle component (401), wherein the electric current (l) is provided by a power supply (430) and is controlled to vary over time in at least one cycle (lcycl), each cycle (lcycl) comprising a lower current value (liow) and a higher current value (lhigh); and - evaluating (240) the at least one part (404) of the electric vehicle component (401) after the at least one cycle (lcycl) of the electric current (l) has run (230) through the at least one part (404) of the electric vehicle component (401).

Description

The present invention relates to evaluation of at least one part of an electric vehicle component, and more specifically to a method for identifying an irregularity caused by a mechanical stress, a thermal stress, an electric stress and / or an insulation problem for the at least one part of the electric vehicle component.BackgroundThe following background description constitutes a description of the background to the present invention, which does not, however, necessarily have to constitute prior art.Vehicle components are generally exposed to hostile environments in use in the vehicle. Mechanical stress in form of vibrations often influence the vehicle components in use. Thermal stress in form of temperature variations also often affect the vehicle components in use. Temperature fluctuations often cause material contractions and expansions of parts of the components.Therefore, to be sure that the vehicle components will function in the hostile environments predicted to be experienced in use, the vehicle components go through testing when they are developed and / or manufactured, i.e. before the vehicle components are mounted / assembled in a vehicle.Typically, mechanical stress may in such tests be caused by exposing the vehicle component to vibrations. Such vibrations of the vehicle component may be caused by a vibration arrangement configured to physically shake the vehicle component, i.e. to cause small and fast movements in for example three dimensions of the vehicle component.Thermal stress may in such tests be caused by exposing the vehicle component to more or less extreme temperature variations. Such temperature variations of the vehicle component may be caused by placing the vehicle component in a temperature variation chamber configured to provide different temperatures.The conventional component testing procedures are developed for testing the whole component. It is not possible to efficiently and accurately perform specific testing of smaller parts of a vehicle component by utilization of such conventional tests. For example, it is not possible to efficiently and accurately determine a quality of a connection inside of a vehicle component by utilization of conventional component testing procedures.It is therefore an objective of the present invention to provide an evaluation of at least one part of an electric vehicle component such that these problems are at least partly solved.According to a first aspect of the present invention, this objective is achieved through the above-mentioned method for evaluating at least one part of an electric vehicle component;the method comprising:- applying a physical vibration to the electric vehicle component, wherein the physical vibration is provided by a vibration arrangement;- running an electric current through at least one part of the electric vehicle component, wherein the electric current is provided by a power supply and is controlled to vary over time in at least one cycle, each cycle comprising a lower current value and a higher current value; and- evaluating the at least one part of the electric vehicle component after the at least one cycle of the electric current has run through the at least one part of the electric vehicle component.Thus, in addition to the conventional vibration test, a varying electric current is run through the at least one part of the electric vehicle component. Hereby, the at least one part of the electric vehicle component is heated up and cooled down locally inside of the electric vehicle component. Temperature fluctuations may generally cause the at least one part of the electric vehicle component to contract and expand with the temperature, and will thus cause mechanical stress on the at least one part of the electric vehicle component.This heating and cooling results in a thermal stress on exactly that at least one part of the electric vehicle component through which the electric current is configured to run. The quality and / or condition of the at least one part of the electric vehicle component, being for example a connection and / or a coupling between different sections of the component, is hereby specifically tested.The presented evaluation method makes it possible to locally run current through a specific and limited part / spot / section / portion of the electric vehicle component, i.e. through the at least one part of the electric vehicle component. The varying current through the at least one part of the electric vehicle component causes a temperature cycling of the at least one part of the electric vehicle component. Thus, the local at least one part of the electric vehicle component may hereby efficiently and accurately be exposed to both vibrations and temperature cycling.Thus, the locally applied current makes it possible to apply thermal stress on one or more chosen parts of a component, since the place where the thermal stress is applied may be chosen more or less freely. In other words, the thermal stress may here be applied exactly to the one or more parts of the electric vehicle component that should be evaluated, and does not have to be applied to the whole electric vehicle component. A more focused, efficient, reliable and accurate evaluation of that at least one part of the electric vehicle component is hereby provided.Furthermore, the quality of connections and / or couplings inside of the electric component may be evaluated in terms of its electrical aspects as well by the presented testing. Thus, the presented evaluation method does not only test how the electric vehicle component copes with the mechanical and thermal stress, but also performs electrical testing, such as resistance testing and / or short circuit testing. Since the automotive industry is moving towards electrification, components are in use not only exposed to natural environments, such as temperature and vibrations, but are also exposed to electrical environments. Therefore, to add a varying current to the component testing stress the component in a more realistic way in relation to its real-world application, as compared to conventional component testing.According to an embodiment of the present invention, the evaluation of the at least one part of the electric vehicle component is utilized to identify one or more in the group of:- an irregularity caused by a mechanical stress on the at least one part of the electric vehicle component;- an irregularity caused by a thermal stress on the at least one part of the electric vehicle component;- an irregularity caused by an electric stress on the at least one part of the electric vehicle component; and- an insulation problem of the at least one part of the electric vehicle component.Thus, various types of irregularities / abnormalities / flaws / faults / deviations / malfunctions caused by various stress and / or problems of the at least one part of an electric vehicle component may be identified / detected by utilization of the presented evaluation method. It may for example be identified / detected that the at least one part is damaged somehow, for example by one or more cracks, or has come loose, for example if its fastening arrangement, such as a screw or a rivet, is at least partially broken, loose, or lost. For example, a broken, loose, or lost internal fastening arrangement within the electric component may hereby be detected externally by analysis of the electric current running through at least one part of the electric vehicle component. If the current is oscillating with high amplitude, this may indicate that e.g. a screw inside the component is broken, loose, or lost. Hereby, a more complete testing of the at least one part of an electric vehicle component is provided, as compared to for example conventional vibration tests.According to an embodiment of the present invention, the method further comprises: - applying a surrounding temperature to the electric vehicle component, wherein the surrounding temperature is provided by a temperature variation arrangement and is controlled to vary over time in at least one cycle, each cycle comprising a lower temperature value and a higher temperature value; and- evaluating the at least one part of the electric vehicle component after the at least one cycle of the surrounding temperature has been applied to the electric vehicle component.Thus, the surrounding temperature of the at least one part of an electric vehicle component, for example in a test chamber, is here varied according to a well-defined temperature cycle. To control the surrounding temperature to interchangeably reach its lower temperature value and its higher temperature value results in a test having a well-defined temperature swing / amplitude for the varying surrounding temperature. This increases the accuracy and reliability of the evaluation, as well as improves the repeatability and thus possibility to compare subsequent tests with each other, since they are all performed with the same variation of the surrounding temperature.According to an embodiment of the present invention,- the lower temperature value is in an interval of -50 °C to -40 °C; and- the higher temperature value is in an interval of 80 °C to 120 °C.Hereby, the electric vehicle component is tested for temperature variations the vehicle and the component is likely to, or may at least possibly, experience in real use.According to an embodiment of the present invention, the surrounding temperature is controlled to:- decrease to the lower temperature value when the electric current is controlled to have the lower current value; and- increase to the higher temperature value when the electric current is controlled to have the higher current value.Hereby, the whole electric vehicle component is exposed to the varying surrounding temperature, in addition to the locally applied thermal stress caused by the varying current through the at least one part of the electric vehicle component. Hereby, a component temperature of the at least one part of the electric vehicle component is caused to also change. The speed of cyclic temperature increases and decreases of the component temperature, i.e. the component temperature change rate becomes greater. Thus, the component temperature of the at least one part of the electric vehicle component changes quicker when both the temperature cycle of the surrounding temperature and the current cycle are applied to the electric vehicle component and the at least one part of the electric vehicle component, respectively.Hereby, the mechanical movements and stress in the at least one part of the electric vehicle component caused by the varying temperature are also increased.According to an embodiment of the present invention, the evaluation of the at least one part of the electric vehicle component after the at least one cycle of the surrounding temperature has been applied to the electric vehicle component is utilized to identify one or more in the group of:- an irregularity caused by a mechanical stress on the at least one part of the electric vehicle component; and- an irregularity caused by a thermal stress on the at least one part of the electric vehicle component.The varying surrounding temperature being applied to the electric vehicle component in combination with the varying electric current run through the at least one part of the electric vehicle component may be used for reliably and accurately detecting irregularities / irregularities / abnormalities / flaws / faults / deviations / malfunctions caused by mechanical and / or thermal stress on the at least one part of the electric vehicle component. It may for example be identified / detected that the at least one part is damaged somehow, for example by one or more cracks, or has come loose, for example if its fastening arrangement is at least partly broken.According to an embodiment of the present invention, the electric current is provided by:- applying an electric voltage over the at least one part of the electric vehicle component, wherein the electric voltage is provided by the power supply and is controlled to vary over time in at least one cycle, each cycle comprising a lower voltage value and a higher voltage value.By applying a voltage over the at least one part of the electric vehicle component, the electric current is specifically controlled to run through exactly that at least one part of the electric vehicle component, such that the at least one part of the electric vehicle component may specifically be tested / measured / evaluated.Also, by applying the voltage over the at least one part of the electric vehicle component, the insulation of the at least one part of the electric vehicle component may be tested simultaneously with the thermal and / or mechanical stress testing.According to an embodiment of the present invention,- the lower voltage value is 0 Volt; and- the higher voltage value depends on a resistance of the at least one part of the electric vehicle component, such that the higher current value is provided.Hereby, a well-defined and varying voltage over the at least one part of the electric vehicle component is provided, such that the at least one part of the electric vehicle component may specifically be tested / measured / evaluated.According to an embodiment of the present invention, the electric voltage is controlled to:- decrease to the lower voltage value to cause the electric current to decrease to the lower current value; and- increase to the higher voltage value to cause the electric current to increase to the higher current value.Hereby, a well-defined and varying electric current through the at least one part of the electric vehicle component is provided, such that the at least one part of the electric vehicle component may be specifically and accurately tested / measured / evaluated with high accuracy and reliability.According to an embodiment of the present invention, the physical vibration is controlled to have:- a frequency in an interval of 8 to 2000 Hertz; and- an acceleration in an interval of 5 to 30 g.Hereby, the electric vehicle component is tested over a broad range of frequencies and accelerations, covering realistic vibrations and mechanical stress that the component may possibly experience in real use.According to an embodiment of the present invention,- the lower current value is 0 Ampere; and- the higher current value is in an interval of 600 to 1000 Ampere.Hereby, it is tested how the at least one part of the electric vehicle component copes with changing component temperatures caused by the varying electric current through the at least one part of the electric vehicle component. The at least one part of the electric vehicle component has a certain resistance. Heat is thus created by resistive losses caused by the electric current running through the at least one part of the electric vehicle component. The varying electric current running through the at least one part of the electric vehicle component causes changing component temperatures. Such component temperature variations are likely to be even more extreme than temperature variations the component may realistically experience in real use.According to an embodiment of the present invention, the evaluation of the at least one part of the electric vehicle component comprises one or more in the group of: - at least one resistance measurement;- at least one short circuit measurement;- at least one temperature measurement; and- at least one mechanical measurement.The varying component temperatures being achieved by the varying current being applied to the at least one part of the electric vehicle component in combination with the applied physical vibrations of the electric vehicle component and possibly also with the varying surrounding temperature may be used for causing irregularities due to mechanical, electrical and / or thermal stress on the at least one part of the electric vehicle component. These irregularities then be reliably and accurately identified / detected by these measurements.According to an embodiment of the present invention, the electrical vehicle component is one in the group of:- an inverter;- a converter;- a control unit; and- an entity transforming electric power to movement.Thus, the herein presented evaluation method is generally applicable to various electrical vehicle component, which makes the method useful in various phases of development of vehicles and / or vehicle components.According to an embodiment of the present invention, each current cycle comprises: - a cold sustaining time period, during which the electric current has the lower current value;- a transition to warm time period, during which the electric current has the higher current value;- a warm sustaining time period, during which the electric current has the higher current value; and- a transition to cold time period, during which the electric current has the lower current value.Thus, the current cycle comprises four different time periods / phases, of which two are temperature transition time periods / phases and two are temperature sustaining time periods / phases. Hereby, the current cycle is well defined, such that an accurate heating and cooling of the at least one part of the electric vehicle component is provided. The lengths of the different time periods / phases may be chosen to result in a high-quality testing, which does not unnecessarily delay the component development process.According to an embodiment of the present invention, each cycle of the electric current has a duration in an interval of 100 to 300 minutes, or has a duration of 200 minutes.The test cycles have a length which results in a high-quality testing, i.e. the length is long enough to secure a reliable test result of high accuracy, at the same time as providing a quick testing which not unnecessarily delays the development of the electric vehicle component.According to an embodiment of the present invention, the power supply is one in the group of:- a direct current power supply; and- an alternating current power supply.Thus, the applied electric current and / or electric voltage may be provided by either a direct current power supply or an alternating current power supply, which makes the evaluation method flexible, and applicable to many types of electric vehicle components. An alternating current having a root mean square (RMS) current value corresponding to a direct current value results in corresponding resistive losses, and thus results in a corresponding evaluation of the at least one part of the electric vehicle component.According to a second aspect of the present invention, the objective is achieved by a system for evaluating at least one part of an electric vehicle component;the system comprising:- a vibration arrangement configured to apply a physical vibration to the electric vehicle component;- a power supply configured to run an electric current through at least one part of the electric vehicle component, wherein the electric current is controlled to vary over time in at least one cycle, each cycle comprising a lower current value and a higher current value; and- an evaluation entity configured to evaluate the at least one part of the electric vehicle component after the at least one cycle of the electric current has run through the at least one part of the electric vehicle component.The system has corresponding advantages as mentioned for the method according to the first aspect.According to an embodiment of the present invention, the evaluation entity comprises one or more in the group of:- a resistance measurement arrangement;- a short circuit measurement arrangement;- a temperature measurement arrangement; and- a mechanical measurement arrangement.Hereby, the test comprises an evaluation including possible detection of a resistance associated problem / fault, a short circuit associated problem / fault, and / or a mechanical stress associated problem / fault of the at least one part of an electric vehicle component.According to a third aspect, the invention relates to a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the herein described method aspect and embodiments.The computer program has corresponding advantages as mentioned for the method according to the first aspect.According to a fourth aspect, the invention relates to a computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the herein described method aspect and embodiments.The computer-readable medium has corresponding advantages as mentioned for the method according to the first aspect.It will be appreciated that all the embodiments described for the method aspect of the invention are applicable also to the system aspect, the computer program aspect and the computer-readable medium aspect of the invention. Thus, all the embodiments described for the method aspect of the invention may be performed / implemented by the herein described system, computer program and / or the computer-readable medium. The system may also comprise a processing device, i.e. a device. The system aspect, the computer program aspect and the computer-readable medium aspect, and their embodiments, have advantages corresponding to the advantages mentioned above for the method aspect and embodiments.Embodiments of the invention will be illustrated in more detail below, along with the enclosed drawings, where similar references are used for similar parts, and where:Figure 1 schematically illustrates an example system according to some aspects and embodiments of the present invention,Figure 2 schematically illustrates an example electric vehicle component,Figure 3 shows a flow chart diagram for a method for evaluation of at least one part of an electric vehicle component according to some aspects and / or embodiments of the present the invention,Figure 4 shows a flow chart diagram for an example evaluation of at least one part of an electric vehicle component according to some embodiments of the present the invention,Figures 5a-d schematically illustrates current, voltage, surrounding temperature and component temperature curves for an example evaluation of at least one part of an electric vehicle component according to some embodiments of the present the invention,Figures 6a-b schematically illustrates current and voltage curves for an example evaluation of at least one part of an electric vehicle component according to some embodiments of the present the invention,Figure 7 schematically illustrates a control unit comprised in a system according to various embodiments of the present invention.Description of preferred embodimentsFigure 1 schematically shows a non-limiting example of a system 400 for evaluation of at least one part of an electric vehicle component 401 according to some herein described aspects and embodiments.The system 400 may, but does not have to, comprise a test chamber 500, in which the electric vehicle component 401 is inserted during the test / evaluation procedure.The system 400 comprises a vibration arrangement 410, which may be arranged in the test chamber 500. The vibration arrangement 410 is configured to apply a physical vibration to the electric vehicle component 104. Mechanical stress, and durability against mechanical stress, may be tested by physically shaking the vehicle component 401, for example by causing small and fast movements of the vehicle component in three dimensions X, Y, Z of the vehicle component. Practically, this may for example be achieved by fastening the vehicle component 401 to the vibration arrangement 410, e.g. by screws or other fastening arrangements, and then vibrating the vibration arrangement 410, and thus also vibrating the vehicle component 401 together with the vibration arrangement 410. The vibration arrangement 410 may for example be or comprise a table / bench / platform configured to vibrate when being controlled to do so.The system 400 comprises a power supply 430, which is configured to run an electric current I through at least one part 404 of the electric vehicle component 401. The electric current I is here controlled to vary over time in at least one cycle lcycl, where each cycle lcycl comprises a lower current value how and a higher current value Ihigh. For example, the power supply 430 may be connected to the electric vehicle component 401 , or to the at least one part 404 of the electric vehicle component 401 , by a first power cable 431 and a second power cable 432.According to various embodiments, the system 400 may also comprise a temperature variation arrangement 420, for example including one or more heating elements, which may be arranged within a test chamber 500 to vary the surrounding temperature Tsurround around the vehicle component 401 within the test chamber 500.The system 400 may further comprise an evaluation entity 450, which is connected to, and is configured to control, the power supply 430. The evaluation entity 450 may also be connected to, and may be configured to control, the vibration arrangement 410. The evaluation entity 450 may also be connected to, and is configured to control, the temperature variation arrangement 420. Thus, the evaluation entity 450 may be configured to control the herein described performed tests / evaluations. The evaluation entity 450 may comprise a below described control unit 600 configured for implementing the herein described aspects and embodiment of the evaluation method.In figure 2, the at least one part 404 of the electric vehicle component 401 is exemplified as a connection / coupling 404 between a first section / circuitry / subcomponent 402 and a second section / circuitry / subcomponent 403 of the electric vehicle component 401. The at least one part 404 may for example be a fastening arrangement comprising e.g. one or more screws, one or more rivets, one or more welds, one or more solders, or one or more other suitable fastening devices or arrangements. The at least one part 404 may also be an electric connection comprising for example one or more connection bars, one or more busbars, one or more connectors, one or more connection joints, or one or more other suitable electric connection devices or arrangements.The at least one part 404 of the electric vehicle component 401 may become damaged or broken, for example may have one or more cracks in it. The at least one part 404 of the electric vehicle component 401 may also have come loose, for example may have lost its grip or connection to the first section 402 and / or second section 403. Hereby, the electric connection between the first section 402 and the second section 403 may be affected and / or broken / damaged.The power supply 430 may be connected to the first section 402 of the electric vehicle component 401 by a first power cable 431 , and may be connected to the second section 403 of the electric vehicle component 401 by a second power cable 432. The connections of the first power cable 431 to the to the first section 402 and of the second power cable 432 to the second section 403 may comprise essentially any suitable and robust connection, comprising e.g. one or more screws and / or one or more robust connectors.The first power cable 431 and / or the second power cable 432 may be properly fixed within the electric vehicle component 401 and / or within the test chamber 500, such that the first power cable 431 and / or the second power cable 432 do not affect, hit or interfere with the other circuitry of the electric vehicle component 401 and / or are not damaged themselves when the vibrations are applied to the electric vehicle component 401. It is hereby also prevented that the insulation on these cables is damaged or impaired, which could possibly lead to electrification of the test environment, e.g. electrification of one or more parts of the test chamber 500.The system 400 further comprises an evaluation entity 450 being configured to evaluate the at least one part 404 of the electric vehicle component 401 after the at least one cycle lcycl of the electric current I has run through the at least one part 404 of the electric vehicle component 401. Thus, when the electric current I running through the at least one part 404 of the electric vehicle component 401 has been applied for a time period allowing it to fluctuate according to at least one current cycle Icy ci, the at least one part 404 of the electric vehicle component 401 is evaluated during that testing time period by the evaluation entity 450.The evaluation entity 450 may comprise one or more connections 453 to the at least one part 404 of the electric vehicle component 401 , and possibly to one or more temperature sensors configured to sense a component temperature T∞mp of the at least one part 404 of the electric vehicle component 401. The evaluation entity 450 may base the applied varying electric current I on the sensed component temperature Tcomp to avoid overheating.Figure 3 shows a flow chart diagram for a method 200 for evaluation of at least one part 404 of an electric vehicle component 401. The electrical vehicle component 401 may comprise various electrical circuitry of essentially any kind. For example, the electrical vehicle component 401 may be an inverter of some kind. The electrical vehicle component 401 may also be a converter / transformer of some kind, for example an electric converter configured perform conversions / transformations between direct current power and alternating current power, between different voltage levels, and / or between different frequencies. As non-limiting examples of such converters / transformers, propulsion inverters and direct current to direct current (DC-to-DC) converters can be mentioned. The electrical vehicle component 401 may also be a control unit of some kind. A vehicle of today normally comprises multiple control units configured for controlling various components / systems / functions of the vehicle. Such control units may be tested / evaluated by the herein disclosed aspects and embodiments. The electrical vehicle component 401 may also be an entity of some kind configured for transforming electric power to movement,In a step 210 of the method 200, a physical vibration is applied to the electric vehicle component 401. The physical vibration is provided by a vibration arrangement 410, for example a vibration arrangement 410 of a test chamber 500 as the one schematically illustrated in figure 1. The vibration arrangement 410 may for example comprise a vibration table or bed onto which the electric vehicle component 401 is temporarily fastened. The vibration table or bed is configured to vibrate in small and fast movements hereby conveyed to the fastened vehicle component. These small movements may for example be performed in three dimensions X, Y, Z of the vehicle component.In a further step 230 of the method 200, an electric current l is run through at least one part 404 of the electric vehicle component 401. The electric current I is schematically illustrated in figure 2, to the left of the at least one part 404. The electric current I may here be a direct current (DC) current provided by a direct current power supply 430, or may be an alternating current (AC) current provided by an alternating current power supply 430. An alternating current having a root mean square (RMS) current value corresponding to a direct current value results in corresponding resistive losses, and thus results in a corresponding heat development and evaluation of the at least one part of the electric vehicle component. As a non-limiting example, the resistive losses, and thus the created heat, for an alternating current having 100 Ampere RMS through the vehicle component 401 are essentially the same as the resistive losses for a direct current having 100 Ampere.The applied current l is controlled to vary over time in one or more cycles lcycl, where each cycle lcycl comprises a lower current value how and a higher current value Ihigh.In a further step 240 of the method 200, the at least one part 404 of the electric vehicle component 401 is evaluated after at least one cycle lcycl of the electric current I has run 230 through the at least one part 404 of the electric vehicle component 401 , as is explained more in detail below.Hereby, i.e. by the evaluation 240 performed after at least one cycle lcycl of the electric current I has run 230 through the at least one part 404 of the electric vehicle component 401, an irregularity caused by a mechanical stress on the at least one part 404 of the electric vehicle component 401 may be identified / detected due to the applied vibrations. Also, an irregularity caused by a thermal stress on the at least one part 404 of the electric vehicle component 401 due to component temperature Tcomp variations caused by the applied varying current I may be identified / detected. Further, an irregularity caused by an electric stress on the at least one part 404 of the electric vehicle component 401 due to the applied varying current I may be identified / detected. Also, an insulation problem of the at least one part 404 of the electric vehicle component 401 due to the applied varying current I may be identified / detected.By running the varying electric current I through a specific at least one part 404 of the electric vehicle component 401 , the component temperature Tcomp of that specific at least one part 404 of the electric vehicle component 401 is varied. Thus, the applied varying electric current I causes a varying / fluctuating component temperature Tcomp of that specific at least one part 404 of the electric vehicle component 401. Hereby, a local component temperature Tcomp variation is created, which makes it possible to concentrate the thermal stress to the at least one part 404 of the electric vehicle component 401. Also, the applied varying electric current I causes an increased and quicker component temperature Tcomp variation than conventional surrounding temperature variations provided in the whole test chamber 500.The method steps of figure 3 may be performed in another order than illustrated in figure 3, as long as the information needed for performing a method step is available when the step is to be performed.According to an embodiment, the physical vibrations being applied to the electric vehicle component 401 are controlled to have a frequency f in an interval of 8 to 2000 Hertz, and to have an acceleration in an interval of 5 to 30 g root mean square (RMS). Thus, the acceleration levels are varied within the frequency interval. Each level of acceleration then causes mechanical movements dependent on the mechanical features of the electric vehicle component 401 and within the frequency interval.According to an embodiment, the lower current value how of the current cycle lcycl is 0 Ampere, and the higher current value Ihigh of the current cycle lcycl is in an interval of 600 to 1000 Ampere.According to an embodiment, each cycle lcycl of the electric current I has a duration in an interval of 100 to 300 minutes, or has a duration of 200 minutes. The current cycle lcycl is explained more in detail in connection with figures 4 and 5a-c below.According to an embodiment, the method 200 further comprises a step 220 of applying a surrounding temperature Tsurround to the electric vehicle component 401. The surrounding temperature Tsurround is provided by a temperature variation arrangement 420, which may be arranged in the test chamber 500, as schematically illustrated in figure 1. The surrounding temperature Tsurround is controlled to vary over time in cycles Tcycl, each cycle Tcycl comprising a lower temperature value Tlow and a higher temperature value Thigh. Thus, the surrounding temperature Tsurround applied to the electric vehicle component 401 in the test chamber 500 is varied by the temperature variation arrangement 420.The evaluation 240 of the at least one part 404 of the electric vehicle component 401 is then performed after at least one cycle Tcycl of the surrounding temperature Tsurround has been applied to the electric vehicle component 401.According to an embodiment, the lower temperature value Tiow of the temperature cycle Tcycl is in an interval of -50 °C to -40 °C, and the higher temperature value Thigh of the temperature cycle Tcycl is in an interval of 80 °C to 120 °C. Hereby, the temperature cycle Tcycl covers essentially any realistic temperature variations the electric vehicle component may be exposed to in use in a vehicle.According to an embodiment, the temperature cycle Tcycl and the electric current cycle lcycl are controlled to be synchronized. Thus, the temperature variation arrangement 420 and the power supply 430 are connected to the evaluation entity 450, and are controlled by the evaluation entity 450 such that the varying surrounding temperature Tsurround and the varying electric current I are synchronously varied.More in detail, the surrounding temperature Tsurround is by the evaluation entity 450 controlled to decrease towards and to the lower temperature value Tiow when the electric current I is controlled to have the lower current value liow. In other words are both the temperature T and the electric current I controlled to simultaneously have or become the lower temperature value Tiow and the lower current value liow, respectively.Conversely, the surrounding temperature Tsurround is by the evaluation entity 450 controlled to increase towards and to the higher temperature value Thigh when the electric current I is controlled to have the higher current value Ihigh. Thus, both the surrounding temperature Tsurround and the electric current I are controlled to simultaneously have or become the higher temperature value Thigh and the higher current value Ihigh, respectively.Hereby, well-defined and synchronized intervals / variations of the both the surrounding temperature Tsurround and the electric current I are provided. Since both the surrounding temperature Tsurround and the electric current I are controlled to simultaneously have or become their higher values Thigh, Ihigh, the component temperature Tcomp of the at least one part 404 of the electric vehicle component 401 increases quickly. Thus, the applied surrounding temperature Tsurround and the applied electric current I work together to quickly increase the component temperature Tcomp of the at least one part 404 of the electric vehicle component 401 in a transition to warm phase. Conversely, the applied surrounding temperature Tsurround and the applied electric current I work together to quickly decrease the component temperature Tcomp of the at least one part 404 of the electric vehicle component 401 in a transition to cold phase.The evaluation 240 of the at least one part 404 of the electric vehicle component 401 after the at least one such cycle Tcycl of the surrounding temperature Tsurround has been applied to the electric vehicle component 401 may then be utilized to identify an irregularity caused by a mechanical stress and / or a thermal stress on the at least one part 404 of the electric vehicle component 401.According to an embodiment, the electric current I is provided by applying 231 an electric voltage V over the at least one part 404 of the electric vehicle component 401. The electric voltage V is schematically illustrated in figure 2 to the left of the at least one part 404. The electric voltage V is provided by the power supply 430 and is controlled to vary over time in at least one cycle Vcycl, where each cycle Vcycl comprises a lower voltage value Vlow and a higher voltage value Vhigh.According to an embodiment, the lower voltage value Vlow is 0 Volt, and the higher voltage value Vhigh has a value depending on a resistance R of the at least one part 404 of the electric vehicle component 401 , such that the higher current value Ihigh mentioned above is provided.According to an embodiment, the electric voltage V is controlled to be decreased to the lower voltage value Vlow to cause the current I to decrease to the lower current value llow. Conversely, the electric voltage V is controlled to be increased to the higher voltage value Vhigh to cause the current I to increase to the higher currentValue lhigh.According to some embodiments, the higher current value Ihigh mentioned in this document is an absolute value, i.e. is an absolute higher current value | lhigh|, and / or the higher voltage value Vhigh mentioned in this document is an absolute value, i.e. is an absolute higher voltage value |Vhigh| . It should be noted that corresponding temperature variations, and also corresponding evaluations, for the at least one part of the vehicle component 401 would be provided if a negative higher current / voltage value -| lhigh | / -|Vhigh | of a certain amplitude would be applied to the at least one part of the vehicle component 401 as if a positive higher current value | lhigh| / +|Vhigh| having the same amplitude would be applied to it.According to an embodiment, the temperature cycle Tcycl and the electric voltage cycle Vcycl are controlled to be synchronized. Thus, the temperature variation arrangement 420 and the power supply 430 are connected to the evaluation entity 450, and are controlled by the evaluation entity 450 such that the varying surrounding temperature Tsurround and the varying electric voltage V are synchronously varied.Thus, the surrounding temperature Tsurround is then controlled by the evaluation entity 450 to decrease towards and to the lower temperature value Tlow when the electric current I, and thus also the electric voltage V, are controlled to have the lower current value I low and the lower voltage value Vlow, respectively. All of the surrounding temperature Tsurround, the electric current I and the electric voltage V are thus controlled to simultaneously have or become the lower temperature value Tlow, the lower current value how, and the lower voltage value Vlow, respectively.Conversely, the surrounding temperature Tsurround is by the evaluation entity 450 controlled to increase towards and to the higher temperature value Thigh when the electric current I, and thus also the electric voltage V, are controlled to have the higher current value Ihigh and the higher voltage value Vhigh, respectively. Thus, all of the surrounding temperature Tsurround, the electric current I, and the electric voltage V are controlled to simultaneously have or become the higher temperature value Thigh, the higher current value Ihigh, and the higher voltage value Vhigh, respectively. Hereby, well-defined and synchronized intervals / variations / fluctuations of the surrounding temperature Tsurround, the electric current I, and the electric voltage V are provided.The evaluation 240 of the at least one part 404 of the electric vehicle component 401 after the at least one such cycle Vcycl of the voltage V has been applied to the electric vehicle component 401 may be utilized to identify / detect an irregularity caused by a mechanical stress, a thermal stress and / or an electric stress on the at least one part 404 of the electric vehicle component 401 , and / or to identify / detect an insulation problem of the at least one part 404 of the electric vehicle component 401.According to an embodiment, the evaluation 240 of the at least one part 404 of the electric vehicle component 401 comprises at least one resistance measurement. For example, the resistance over the at least one part 404 of the electric vehicle component 401 schematically shown in figure 2 is determined and evaluated by the evaluation entity 450 utilizing and / or comprising a resistance measurement arrangement. It may hereby be identified / detected that the at least one part 404 is damaged or has come loose if the resistance is increased during the test, in relation to the resistance before the test.According to an embodiment, the evaluation 240 of the at least one part 404 of the electric vehicle component 401 comprises at least one short circuit measurement. For example, it is determined and evaluated by the evaluation entity 450 utilizing and / or comprising a short circuit measurement arrangement if there is a short circuit between the first section 402 and the second section 403 of the electric vehicle component 401 schematically illustrated in figure 2.According to an embodiment, the evaluation 240 of the at least one part 404 of the electric vehicle component 401 comprises at least one temperature measurement. For example, it is determined and evaluated by the evaluation entity 450 utilizing and / or comprising a temperature measurement arrangement how the component temperature and / or the temperature of its at least one part 404 vary when the current and / or surrounding temperature vary.According to an embodiment, the evaluation 240 of the at least one part 404 of the electric vehicle component 401 comprises at least one mechanical measurement. For example, it is determined and evaluated by the evaluation entity 450 comprising a mechanical measurement arrangement if there are any cracks and / or other damages on the at least one part 404 of the electric vehicle component 401. The evaluation entity 450 may here comprise or control one or more arrangements, such as e.g. optical sensors, x-ray devices or other optical measurement devices, configured for visual and / or optical inspection of the at least one part 404 of the electric vehicle component 401. Also, manual inspection may at least partially be utilized for the mechanical measurements.Figure 4 shows a flow chart diagram for a testing method 900 according to some embodiments. Figure 5a shows a non-limiting example diagram for the electric current I run through the at least one part 404 of the electric vehicle component 401. Figure 5b shows a non-limiting example diagram for the electric voltage V applied over the at least one part 404 of the electric vehicle component 401. Figure 5c shows a non-limiting example diagram for the surrounding temperature Tsurround applied to the electric vehicle component 401. Figure 5d shows a non-limiting example diagram for the component temperature Tcomp of the at least one part 404 of the electric vehicle component 401.In a first step 901, the method 90 is initiated. The applied surrounding temperature Tsurround is reduced towards -40 °C and the physical vibrations, having a frequency f in an interval of 8 to 2000 Hertz and an acceleration in an interval of 5 to 30 g RMS, for example at around 6 g RMS, are applied to the electric vehicle component 401. The physical vibrations are thereafter applied to the electric vehicle component 401 until the test ends in the seventh step 907. The electric current I running through the at least one part 404 of the electric vehicle component 401 is initially zero; I = 0 Ampere. The electric voltage V applied over the at least one part 404 of the electric vehicle component 401 is also zero; V = 0 Volt.In a second step 902, the test cycle is started with a cold sustaining phase, in which the surrounding temperature Tsurround is maintained at or around -40 °C for a cold sustaining time period tcold_sustain of 60 minutes; tcoid_sustain = 60 minutes. The electric current I applied through the at least one part 404 of the electric vehicle component401 has its lower current value llow, being zero; how = 0 Ampere. The electric voltage V applied over the at least one part 404 of the electric vehicle component 401 has its lower voltage value Vlow, being zero; Vlow = 0 Volt. The component temperature decreases to or around -40 °C during the cold sustaining time period tcold_sustain.In a third step 903, the test cycle enters into a transition to warm phase, in which the surrounding temperature Tsurround is increased from -40 °C towards 110 °C for a transition to warm time period twarm_transition of 40 minutes; twarm_transition — 40 minutes. The electric current I running through the at least one part 404 of the electric vehicle component 401 has its higher current value lhigh, being in an interval of 600 to 1000 Ampere, for example 620 Ampere; lhigh = 620 Ampere. The electric voltage V over the at least one part 404 of the electric vehicle component 401 corresponding to the higher current value Ihigh also has its higher voltage value Vhigh, in the non-limiting example of figured 5a-c being a value Vhigh of 1 to 2 Volt. The component temperature increases from -40 °C towards 110°C during the transition to warm time period twarm_transition.In a fourth step 904, the test cycle enters a warm sustaining phase, in which the surrounding temperature Tsurround is maintained at or around 110 °C for a warm sustaining time period twarm_sustain of 60 minutes; twarm_sustain = 60 minutes. The electric current I applied through the at least one part 404 of the electric vehicle component 401 has its higher current value lhigh. The electric voltage V over the at least one part 404 of the electric vehicle component 401 corresponding to the higher current value Ihigh also has its higher voltage value Vhigh. The component temperature increases to or around 110°C during the warm sustaining time period twarm_sustain.In a fifth step 905, the test cycle enters into a transition to cold phase, in which the surrounding temperature Tsurround is reduced from 110 °C towards -40 °C again during a transition to cold time period tcold_transition of 40 minutes; tcold_transition = 40 minutes. The electric current I run through the at least one part 404 of the electric vehicle component 401 has its lower current value llow; i.e. how = 0 Ampere. The electric voltage V applied over the at least one part 404 of the electric vehicle component 401 also has its lower voltage value Vlow; i.e. Vlow = 0 Volt. The component temperature decreases from 110°C towards - 40 °C during the transition to cold time periodtcold_transition.In a sixth step 906, it is determined if the test is finished or not. If the test is determined to be finished, the method 900 proceeds to the seventh step 907, in which the test is ended. If the test is determined not to be finished, the method 900 proceeds to the second step 902, in which a subsequent cold sustaining phase is started, and so on.In the non-limiting example illustrated in figures 4 and 5a-c, each current cycle lcycl, voltage cycle Vcycl, and temperature cycle Tcycl has a duration of 200 minutes.In figures 5a-c, some non-limiting examples of a number of test cycles are illustrated. The cold sustain time period tcold_sustain, the transition to warm time period twarm_transition, the warm sustain time period twarm_sustain, and the transition to cold time period tcold_transition for the first test cycle are schematically illustrated. Such corresponding time periods are then repeated over time for each subsequent test cycle.Figure 6a shows a non-limiting example diagram for the electric current I run through the at least one part 404 of the electric vehicle component 401. Figure 6b shows a non-limiting example diagram for the electric voltage V applied over the at least one part 404 of the electric vehicle component 401.As seen in figures 6a-b, the electric current I through the at least one part 404 of the electric vehicle component 401 is controlled to vary over time in cycles lcycl between its lower current value how and its higher current value Ihigh. Also, the electric voltage V over the at least one part 404 of the electric vehicle component 401 is controlled to vary over time in cycles Vcycl between its lower voltage value Viow and its higher voltage value Vhigh.After approximately one test cycle, the electric current I and the electric voltage V start oscillating quickly and with high amplitude. These oscillations may be seen as indications that there is a fault / irregularity in the at least one part 404 of the electric vehicle component 401.For example, if a connection screw within the electric vehicle component 401 is broken, the physical vibrations being applied 210 to the electric vehicle component 401 by the vibration arrangement 410 may cause the screw to jump up and down in its hole. Thus, the screw will sometimes be in physical contact with its original contact point, and will at other times be out of physical contact with its original contact point. The screw may therefore interchangeably conduct and not conduct current, which may cause the oscillations mentioned above.Thus, based on the measured oscillations of the electric current I and the electric voltage V, the evaluation 240 of the at least one part 404 of the electric vehicle component 401 after at least one cycle lcycl of the electric current I has run 230 through the at least one part 404 of the electric vehicle component 401 detects / identifies that there is an irregularity caused by a mechanical stress, a thermal stress and / or an electric stress on the at least one part 404 of the electric vehicle component 401. For example, a connection / coupling of the at least one part 404 of the electric vehicle component 401 has been damaged or broken, or has come loose, such that the electric contact is poor.Figure 7 shows in schematic representation a control unit 800. The control unit 800 comprises a computing unit 801 , which can be constituted by essentially any suitable type of processor or microcomputer, for example a circuit for digital signal processing (Digital Signal Processor, DSP), or a circuit having a predetermined specific function (Application Specific Integrated Circuit, ASIC). The computing unit 801 is connected to a memory unit 802 arranged in the control unit 800, which memory unit provides the computing unit 801 with, for example, the stored program code and / or the stored data which the computing unit 801 requires to be able to perform computations. The computing unit 801 is also arranged to store partial or final results of computations in the memory unit 802.In addition, the control unit 800 is provided with devices 811, 812, 813, 814 for receiving and transmitting input and output signals. These input and output signals can contain waveforms, impulses, or other attributes which, by the devices 811 , 813 for the reception of input signals, can be detected as information and can be converted into signals which can be processed by the computing unit 801. These signals are then made available to the computing unit 801. The devices 812, 814 for the transmission of output signals are arranged to convert signals received from the computing unit 801 in order to create output signals by, for example, modulating the signals, which can be transmitted to other parts of and / or systems in the vehicle.Each of the connections to the devices for receiving and transmitting input and output signals can be constituted by one or more of a cable; a data bus, such as a CAN bus (Controller Area Network bus), a MOST bus (Media Orientated Systems Transport bus), or some other bus configuration; an ethernet connection; or by a suitable wireless connection. A person skilled in the art will appreciate that the above-stated computer can be constituted by the computing unit 801 and that the above- stated memory can be constituted by the memory unit 802.Control systems in modern vehicles commonly comprise communication bus systems consisting of one or more communication buses for linking a number of electronic control units (ECU's), or controllers, and various components located on the vehicle. Such a control system can comprise a large number of control units and the responsibility for a specific function can be divided amongst more than one control unit. Vehicles of the shown type thus often comprise significantly more control units than are shown in figures 1 and 7, which is well known to the person skilled in the art within this technical field.In a shown embodiment, the present invention may be implemented by the one or more herein mentioned control units or processing arrangements 800. The invention can also, however, be implemented wholly or partially in one or more other control units already present in the vehicle, or in some control unit dedicated to the present invention.Here and in this document, control units, control entities or processing arrangements are sometimes described as being arranged for performing the methods and / or steps 210, 220, 230, 240 according to the invention. This also includes that the units, entities or processing arrangements are designed to and / or configured to perform these method steps.One or more control entities 610, 620, 630, 640 may be arranged for performing the methods and / or steps. Such entities 610, 620, 630, 640 may be arranged as separate entities, or may be logically separated but physically implemented in the same unit, or may be both logically and physically arranged together. These control entities 610, 620, 630, 640 may for example correspond to groups of instructions, which can be in the form of programming code, that are input into, and are utilized by a processor / computing unit 801 when the entities are active and / or are utilized for performing its method steps, respectively.The present invention is not limited to the above described embodiments. Instead, the present invention relates to, and encompasses all different embodiments being included within the scope of the independent claims.

Claims

1. A method (200) for evaluating at least one part (404) of an electric vehicle component (401);the method (200) being characterized by:- applying (210) a physical vibration in three dimensions X, Y, Z to the electric vehicle component (401), wherein the physical vibration of the electric vehicle component (401) is provided by vibrating the electric vehicle component (401) together with a vibration arrangement (410) to which the electric vehicle component (401) is temporarily fastened;- running (230) an electric current (l) through at least one part (404) of the electric vehicle component (401), wherein the electric current (l) is provided by a power supply (430) and is controlled to vary overtime in at least one cycle (lcycl), each cycle (lcycl) comprising a lower current value (llow) and a higher current value (hhigh); and - evaluating (240), by utilization of an evaluation entity (450), the at least one part (404) of the electric vehicle component (401) after the at least one cycle (lcycl) of the electric current (l) has run (230) through the at least one part (404) of the electric vehicle component (401).

2. The method (200) as claimed in claim 1, wherein the evaluation (240) of the at least one part (404) of the electric vehicle component (401) is utilized to identify one or more in the group of:- an irregularity caused by a mechanical stress on the at least one part (404) of the electric vehicle component (401);- an irregularity caused by a thermal stress on the at least one part (404) of the electric vehicle component (401);- an irregularity caused by an electric stress on the at least one part (404) of the electric vehicle component (401); and- an insulation problem of the at least one part (404) of the electric vehicle component (401).

3. The method (200) as claimed in any one of claims 1-2, wherein the method (200) further comprises:- applying (220) a surrounding temperature (Tsurround) to the electric vehicle component (401), wherein the surrounding temperature (Tsurround) is provided by a temperature variation arrangement (420) and is controlled to vary over time in at least one cycle (Tcycl), each cycle (Tcycl) comprising a lower temperature value (Tlow) and a higher temperature value (Thigh); and- evaluating (240), by utilization of the evaluation entity (450), the at least one part(404) of the electric vehicle component (401) after the at least one cycle (Tcycl) of the surrounding temperature (Tsurround) has been applied to the electric vehicle component (401).

4. The method (200) as claimed in claim 3, wherein- the lower temperature value (Tlow) is in an interval of -50 °C to -40 °C; and- the higher temperature value (Thigh) is in an interval of 80 °C to 120 °C.

5. The method (200) as claimed in any one of claims 3-4, wherein the surrounding temperature (Tsurround) is controlled to:- decrease to the lower temperature value (Tlow) when the electric current (L) is controlled to have the lower current value (llow); and- increase to the higher temperature value (Thigh) when the electric current (L) is controlled to have the higher current value (lhigh).

6. The method (200) as claimed in any one of claims 3-5, wherein the evaluation (240) of the at least one part (404) of the electric vehicle component (401) after the at least one cycle (Tcycl) of the surrounding temperature (Tsurround) has been applied to the electric vehicle component (401) is utilized to identify one or more in the group of:- an irregularity caused by a mechanical stress on the at least one part (404) of the electric vehicle component (401); and- an irregularity caused by a thermal stress on the at least one part (404) of the electric vehicle component (401).

7. The method (200) as claimed in any one of claims 1-6, wherein the electric current (I) is provided by:- applying (231) an electric voltage (V) over the at least one part (404) of the electric vehicle component (401), wherein the electric voltage (V) is provided by the power supply (430) and is controlled to vary over time in at least one cycle (VcycL), each cycle (Vcycl) comprising a lower voltage value (Vlow) and a higher voltage value (Vhigh).

8. The method (200) as claimed in claim 7, wherein- the lower voltage value (Vlow) is 0 Volt; and- the higher voltage value (Vhigh) depends on a resistance (R) of the at least one part (404) of the electric vehicle component (401), such that the higher current value (lhigh) is provided.

9. The method (200) as claimed in any one of claims 7-8, wherein the electric voltage (V) is controlled to:- decrease to the lower voltage value (Vlow) to cause the electric current (l) to decrease to the lower current value (llow); and- increase to the higher voltage value (Vhigh) to cause the electric current (l) to increase to the higher current value (lhigh).

10. The method (200) as claimed in any one of claims 1-9, wherein the physical vibration is controlled to have:- a frequency (f) in an interval of 8 to 2000 Hertz; and- an acceleration in an interval of 5 to 30 g.

11. The method (200) as claimed in any one of claims 1-10, wherein- the lower current value (llow) is 0 Ampere; and- the higher current value (lhigh) is in an interval of 600 to 1000 Ampere.

12. The method (200) as claimed in any one of claims 1-11 , wherein the evaluation (240) of the at least one part (404) of the electric vehicle component (401) comprises one or more in the group of:- at least one resistance measurement;- at least one short circuit measurement;- at least one temperature measurement; and- at least one mechanical measurement.

13. The method (200) as claimed in any one of claims 1-12, wherein the electrical vehicle component (401) is one in the group of:- an inverter;- a converter;- a control unit; and- an entity transforming electric power to movement.

14. The method (200) as claimed in any one of claims 1-13, wherein each current cycle (lcycl) comprises:- a cold sustaining time period (tcold_sustain), during which the electric current (l) has the lower current value (llow);- a transition to warm time period (twarm_transition), during which the electric current (l) has the higher current value (lhigh);- a warm sustaining time period (twarm_sustain), during which the electric current (l) has the higher current value (lhigh); and- a transition to cold time period (tcold_transition), during which the electric current (l) has the lower current value (llow).

15. The method (200) as claimed in any one of claims 1-14, wherein each cycle (lcycl) of the electric current (I) has a duration in an interval of 100 to 300 minutes, or has a duration of 200 minutes.

16. The method (200) as claimed in any one of claims 1-15, wherein the power supply (430) is one in the group of:- a direct current power supply; and- an alternating current power supply.

17. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method (200) according to any one of claims 1-16.

18. A computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the method (200) according to any one of claims 1-16.

19. A system (400) for evaluating at least one part (404) of an electric vehicle component (401);the system (400) being characterized by:- a vibration arrangement (410) configured to apply (210) a physical vibration in three dimensions X, Y, Z to the electric vehicle component (401), wherein the vibration arrangement (410) is configured to be temporarily fastened to the electric vehicle component (401) and to vibrate the electric vehicle component (401) together with the vibration arrangement (410);- a power supply (430) configured to run (230) an electric current (I) through at least one part (404) of the electric vehicle component (401), wherein the electric current (l) is controlled to vary over time in at least one cycle (lcycl), each cycle (lcycl) comprising a lower current value (llow) and a higher current value (lhigh); and- an evaluation entity (450) configured to evaluate (240) the at least one part (404) of the electric vehicle component (401) after the at least one cycle (lcycl) of the electric current (l) has run (230) through the at least one part (404) of the electric vehicle component (401).

20. The system (400) as claimed in claim 19, wherein the evaluation entity (450) comprises one or more in the group of:- a resistance measurement arrangement;- a short circuit measurement arrangement;- a temperature measurement arrangement; and- a mechanical measurement arrangement.