Method for determining a quality parameter of an electrical machine

Abstract

The invention relates to a method for determining a quality parameter (Q) of an electrical machine (2) having a rotor (6) and a stator (8), wherein the stator (8) has two subsystems (12, 14) each with three phase windings (U1, V1, W1, U2, V2, W2), wherein a phase winding (U2, V2, W2) of the second subsystem (14) is in phase with each phase winding (U1, V1, W1) of the first subsystem (12). According to the method, in-phase phase windings (U1, V1, W1, U2, V2, W2) of the first subsystem (12) and of the second subsystem (14) are electrically connected to one another using a contacting device (20). The rotor (6) is externally driven, and a current (IU, IV, IW) is measured between the electrically connected phase windings (U1, V1, W1, U2, V2, W2). For each of the flows (IU, IV, IW) a characteristic quantity (GU, GV, GW) is determined and the quality parameter (Q) is determined based on at least one of the quantities (GU, GV, GW).Furthermore, the invention relates to a device (4) by means of which the method can be carried out.

Description

[0001] The invention relates to a method for determining a quality parameter of an electrical machine having a rotor and a stator, wherein the stator comprises two three-phase subsystems each having three phase windings, and wherein the two subsystems have no phase offset from one another.

[0002] An electric machine comprises a stator and a rotor, with a so-called air gap formed between the rotor and the stator. Particularly in an electric machine designed as a synchronous motor, the air gap between the rotor and the stator is designed to be comparatively small to achieve a high power density.

[0003] If the rotor deviates from a specified position relative to the stator, particularly by forming an asymmetrical air gap, there is a risk of undesirable side effects during operation of the electric machine. Such a deviation can occur, for example, due to (rotor) shaft misalignment, bearing shield misalignment, and / or excessive component deviations, and can adversely result in vibration, increased noise, increased wear, and / or a magnetic force with a radial component.

[0004] In the final assembly state of the electrical machine, it is not possible or only possible with comparatively great effort to measure the air gap.

[0005] The invention is based on the object of enabling and / or facilitating an assessment of the quality of such an electrical machine.

[0006] This object is achieved according to the invention by a method having the features of claim 1. Furthermore, the object is achieved according to the invention by a method having the features of claim 6 and by means of a device having the features of claim 7.

[0007] The (first) method serves to determine a quality parameter (quality value) of an electrical machine. The electrical machine is, in particular, a synchronous motor, in particular a brushless synchronous motor. The electrical machine comprises, at most, a rotor and a stator, between which an air gap is formed. The stator has two subsystems, each of which in turn comprises three phase windings. The stator therefore has a total of six phase windings. Each of the subsystems is thus formed by its phase windings, wherein in each of the subsystems, its phase windings are electrically connected to one another, for example, in a star connection or alternatively in a delta connection.

[0008] The two subsystems form mutually redundant systems, so that in the event of a failure or defect in one of the subsystems, the electrical machine can continue to operate using the other subsystem.

[0009] The determination of the quality parameter described below is conveniently carried out directly after the assembly of the rotor and stator. In other words, this determination is conveniently carried out "end of line." Suitable for this purpose, the stator's phase connections, i.e., the electrical connections of the phase windings, are not connected to the electronics for electronics, especially for a bridge circuit.

[0010] The electrical machine, in particular its rotor and stator, is designed such that there is no phase offset between the two subsystems, particularly during the intended operation of the electrical machine. Thus, each phase winding of the first subsystem is assigned a phase winding of the second subsystem, which are in phase with one another. Accordingly, the electrical machine is designed such that when the rotor is driven externally, in other words when the rotor is driven in rotation by a drive separate from the electrical machine, i.e. when the rotor is driven in rotation without being energized by the stator, the same voltage is induced in the in-phase phase windings if the air gap is symmetrical. In the case of an asymmetrical air gap, however, the voltages induced in the in-phase phase windings of the two subsystems can differ from one another.

[0011] According to the method, phase windings in phase are first electrically connected to one another, i.e., interconnected, using a contacting device. In other words, the phase winding of the first subsystem is electrically contacted with the phase winding of the second subsystem between which no phase offset is intended during operation of the electrical machine, in particular when the stator is energized.

[0012] The rotor is then externally driven.

[0013] In this process, a current is measured between the phase windings that are electrically connected to each other via the contacting device and are therefore in phase with each other. A characteristic current value is determined for each of the currents, particularly their temporal profiles. The quality parameter is then determined based on at least one of the characteristic values determined in this way.

[0014] In particular, the more symmetrical the air gap is, the smaller the respective current is. Therefore, a statement about the air gap can be made based on the current and / or the corresponding quality parameter. In particular, the quality parameter correlates with the air gap. In summary, this allows a statement about the quality of the assembled electrical machine to be made using a relatively simple current measurement.

[0015] If the rotor comprises two further subsystems, i.e. if the stator comprises four subsystems with three phase windings each, the method described above can and / or is carried out in an analogous manner with the other two subsystems.

[0016] According to a suitable embodiment of the method, the amplitude or effective value, i.e., the RMS (root mean square) value, of the respective current is determined as the characteristic quantity. Thus, the amplitude or effective value is determined for each measured current and used as the characteristic quantity for the respective current.

[0017] For example, each of the measured electrical currents is evaluated separately. For this purpose, the characteristic quantity is determined for each of the electrical currents, and a quality parameter is derived from these quantities. In this example, the characteristic quantity is used as the respective quality parameter.

[0018] Alternatively, the corresponding characteristic quantity is determined for each of the measured electrical currents. Only one of these quantities, for example, the one with the largest magnitude, is chosen as the quality parameter.

[0019] Alternatively and preferably, according to a preferred embodiment of the method, the mean value, in particular the arithmetic mean, of the characteristic quantities and / or their absolute values is determined as the quality parameter. In this way, all measured currents are used in a comparatively simple manner in determining the quality parameter and thus in evaluating the electrical machine.

[0020] According to a suitable embodiment of the method, a first threshold value is specified for the quality parameter, whereby the electrical machine is marked as a non-conforming part, i.e., as scrap, if the quality parameter exceeds the first threshold value. Appropriately, if the first threshold value is exceeded, corresponding information is output to a user.

[0021] According to an expedient development of the method, a second threshold value is specified for the quality parameter. Expediently, the second threshold value is lower than the first threshold value. A warning is issued, in particular to the user, if the quality parameter exceeds the second threshold value. The second threshold value serves as a type of early warning. If this threshold value is exceeded, it is possible to readjust an assembly device for producing the electrical machine accordingly or to replace a defective batch of one of the components of the electrical machine for further assembly processes. In this way, assembly rejects are advantageously reduced or even prevented.

[0022] The first and / or second threshold values may differ for different variants of the electrical machine, i.e., for variants of the electrical machine with different designs and / or with differently configured components. The first threshold value and / or the second threshold value are therefore expediently determined in advance based on an empirical test, a quality requirement for the electrical machine, or a simulation of the electrical machine's operation.

[0023] A further aspect of the invention relates to a further method (second method). This method serves to control the manufacturing process of electrical machines, in particular the assembly process of the rotor and the stator. These electrical machines each comprise—as described in connection with the first method—a rotor and a stator, between which an air gap is formed. The stator comprises two subsystems, each with three phase windings, and the two subsystems have no phase offset from one another.

[0024] According to the second method, for several electrical machines which were manufactured successively and preferably using the same assembly device, a quality parameter is determined in each case according to the first method in one of the variants described above.

[0025] Subsequently, a quality parameter change rate is determined based on the quality parameters determined for the electrical machines.

[0026] For example, one or more threshold values are specified for the quality parameter change rate. Each of these threshold values depends, for example, on the variant of the electrical machine to be manufactured and / or on the assembly device. Therefore, the respective threshold value is expediently determined empirically.

[0027] In the case of a comparatively high quality parameter change rate corresponding to an exceedance of one of these threshold values (third threshold value), which represents a sudden change in the quality parameter, this indicates, for example, a batch change of one of the components of the electrical machine, a defect in the assembly device or an adjustment of the assembly device due to an event (in particular a single one), for example due to an impact on the assembly device.

[0028] For example, if the quality parameter change rate is comparatively low and a fourth threshold is exceeded which is smaller than the third threshold, this indicates a gradual change in the assembly facility.

[0029] In summary, the manufacturing process of electrical machines is controlled based on the quality parameter change rate and / or a number of possible error sources are reduced based on the quality parameter change rate, thus facilitating the elimination of a corresponding error.

[0030] A further aspect of the invention relates to a device for determining a quality parameter of an electrical machine according to the first method. The device is thus intended to determine the quality parameter for an electrical machine comprising a rotor and a stator, wherein the stator has two subsystems, each with three phase windings, wherein one phase winding of the second subsystem is in phase with each phase winding of the first subsystem.

[0031] The device comprises a contacting device which is provided and configured to electrically connect in-phase phase windings of the first subsystem and the second subsystem.

[0032] Furthermore, the device comprises a drive for rotating the rotor, i.e. for externally driving the rotor, as well as current sensors for measuring the currents between the phase windings electrically connected to one another by means of the contacting device.

[0033] The device further comprises means for implementing the first method in one of the variants described above. The means comprise, in particular, a control device (control unit) by means of which the drive can be controlled and an evaluation unit, for example, integrated into the control device, which is connected to the current sensors via signal and / or data transmission. Optionally, the means additionally comprise an output device for outputting the warning and / or the early warning.

[0034] In the following, exemplary embodiments of the invention are explained in more detail with reference to a drawing. In the drawings: Fig. 1 schematically shows in a flow chart a method for determining a quality characteristic of an electrical machine, Fig. 2 schematically shows in a flow diagram a method for controlling the manufacturing process of electrical machines Fig. 3 schematically shows an electrical machine with a rotor and a stator, the stator having two subsystems, each formed by three interconnected phase windings, Fig. 4 schematically shows a device for determining the quality parameter of an electrical machine according to the method according to claim 1, Fig. 5a schematically shows the connection of the stator according to a first variant, wherein the phase windings of each subsystem are interconnected according to a star connection, Fig. 5b schematically shows the connection of the stator according to a second variant, wherein the phase windings of each subsystem are interconnected according to a delta connection, Fig. 6 shows in a diagram the quality parameters for electrical machines manufactured consecutively.

[0035] Corresponding parts and sizes are always provided with the same reference symbols in all figures.

[0036] In the Fig. 1 shows a flowchart representing a method for determining a quality parameter Q of an electrical machine 2. This method is also referred to here and below as the "first method". A device 4, by means of which the method is carried out, is shown in the Fig. 4 is shown schematically. The electrical machine 2, for which the quality parameter Q is determined, comprises a rotor 6 and a stator 8, between which an air gap 10 is formed. The electrical machine 2 is in particular a brushless synchronous electric motor. The rotor 6 comprises, in a manner not shown in detail, permanent magnets for generating a magnetic field. The stator 8 comprises two subsystems 12, 14, each having three phase windings U1, V1, W1, U2, V2, W2. The stator 8 therefore comprises a total of six phase windings U1, V1, W1, U2, V2, W2. Each of the subsystems 12, 14 is formed on the basis of the corresponding electrically interconnected phase windings.

[0037] The electrical machine 2 is designed such that, particularly during the intended operation of the electrical machine 2, there is no phase offset between the two subsystems 12 and 14. In-phase phase windings are designated here with the same letter, i.e., there is no phase offset between the phase winding U1 and the phase winding U2. Accordingly, there is no phase offset between the phase winding V1 and the phase winding V2, and there is no phase offset between the phase winding W1 and the phase winding W2. In summary, for each phase winding U1, V1, W1 of the first subsystem 12, one of the phase windings U2, V2, W2 of the second subsystem 14 is in phase.

[0038] An exemplary design of such an electrical machine is shown schematically in the Fig. 3. In the Fig. 5a, Fig. 5b shows equivalent circuit diagrams of the stator 8, whereby in the variant according to the Fig. 5a, the phase windings U1, V1, W1 are interconnected in a star configuration to form the first subsystem 12. The phase windings U2, V2, W2 are also interconnected in a star configuration to form the second subsystem 14, wherein the first subsystem 12 and the second subsystem 14 comprise separate star points.

[0039] In the alternative design of the stator 8 according to the Fig. 5b, the phase windings U1, V1, and W1 are interconnected in a delta circuit to form the first subsystem 12. The phase windings U2, V2, and W2 are interconnected in a separate delta circuit to form the second subsystem 14.

[0040] The quality parameter Q is preferably determined "end of line." Suitably, the stator phase connections, i.e., the electrical connections 16 of the phase windings, are not yet connected to the electronics for an electronic circuit, especially for a bridge circuit.

[0041] According to the method, in a first step 1a, phase windings U1, V1, W1, U2, V2, W2 of the first subsystem 12 and the second subsystem 14 are electrically connected to one another using a contacting device 20 of the device 4. In the design of the electrical machine 2 according to the Fig. 5a, terminal 16 of phase winding U1 is connected to terminal 16 of phase winding U2. Similarly, terminal 16 of phase winding V1 is electrically connected to terminal 16 of phase winding V2, and terminal 16 of phase winding W1 is electrically connected to terminal 16 of phase winding W2. In the design of the electrical machine 2 according to Fig. 5b, the terminal 16 of the first subsystem 12 that is connected to the phase windings U1 and V1 is electrically connected to the terminal 16 of the second subsystem 14 that is connected to the phase windings U2 and V2. Analogously, the terminal 16 of the first subsystem 12 that is connected to the phase windings V1 and W1 is electrically connected to the terminal 16 of the second subsystem 14 that is connected to the phase windings V2 and W2. Furthermore, the terminal 16 of the first subsystem 12 that is connected to the phase windings W1 and U1 is electrically connected to the terminal 16 of the second subsystem 14 that is connected to the phase windings W2 and U2.

[0042] In the Fig. 5a and Fig. In Figure 5b, for the purpose of better visibility, the conductors 18 of the contacting device 20, by means of which the phase windings U1, V1, W1, U2, V2, W2 are electrically connected to one another, are shown in dashed lines.

[0043] In a subsequent second step IIa, the rotor 6 is externally driven. For this purpose, the rotor 6 is caused to rotate by a drive 22 of the device 4.

[0044] Furthermore, in a step IIIa, between the electrical currents I U , I V , I W measured between the electrically connected phase windings U1, V1, W1, U2, V2, W2.

[0045] For this purpose, the device 4 comprises a current sensor 24. The current sensors 24 are preferably part of the contacting device 20. In this case, the current sensors 24 measure the current in the respective conductor LT between terminals 32 for the phase terminals 16 arranged at the end of the respective conductor 18.

[0046] The device 4 comprises a control device 26, which is connected to the drive 22 via signal and / or data transmission for operating the drive 22. Furthermore, the device 4 comprises an evaluation unit 28, which is integrated into the control device 26, for example. The current sensors are connected to the evaluation unit 28 via signal and / or data transmission, so that corresponding measurement data or measurement signals can be transmitted to the evaluation unit 28.

[0047] In a step IVa, for each of the currents I U , I V , I W a quantity G characterizing this current U , G V G W For example, an amplitude or an effective value is defined as the respective quantity G U , G V G W certainly.

[0048] For example, (in an alternative not shown in detail) the sizes G U , G V G W used as a respective quality parameter.

[0049] Alternatively, in step Va, the, in particular arithmetic, mean value M of the quantities G U , G V , G W and this is used as the quality parameter Q.

[0050] In summary, at least one of the variables G U , G V , G W the quality parameter Q is determined.

[0051] In a subsequent step IVa, a first threshold value S1 (see also Fig. 6) and a second threshold S2 (see also Fig. 6) for the quality parameter Q. The second threshold value S2 is smaller than the first threshold value S1. The quality parameter Q is compared with the two threshold values.

[0052] If the quality parameter Q exceeds the second threshold S2, but preferably not the first threshold S1, a warning is issued to a user. For this purpose, the device 4 comprises an output device 30, which is controlled accordingly by the control device 26.

[0053] If the quality parameter Q also exceeds the first threshold value, the electrical machine 2 is marked as a non-conforming part. For example, corresponding information is output to the user of the device 4 via the output device 30.

[0054] The control device 26, the evaluation device 28, the drive 22, and the output device 30 thus form means for carrying out the method.

[0055] In the Fig. Figure 2 shows a second method using a flowchart. This second method is used to control the manufacturing process of electrical machines 2, as shown above.

[0056] In a first step Ib of the second method, the quality parameter Q i determined according to the first method. The electrical machines 2 were tested consecutively at the time of manufacture t i and in particular manufactured using the same assembly equipment.

[0057] In a second step Ilb, the quality parameters Q i a quality parameter change rate R is determined.

[0058] For this purpose, for example, as in the Fig. 6, first a diagram is created in which the quality parameters Q iare plotted one after the other according to the chronological order of production of the respective electrical machine 2. Thus, the quality parameters Q i The later the respective electrical machine was manufactured, the further to the right it is plotted. The abscissa thus corresponds to the time of manufacture t.

[0059] For example, a best-fit curve or, in sections, a best-fit line is plotted for the data points (Q i , t i ). The slope of the best-fit curve or best-fit line is then determined as the quality parameter change rate R.

[0060] Alternatively, the quality parameter change rate R is determined as: R=(Qi−Qi−1) / (ti−ti−1)

[0061] The quality parameter change rate R is then compared with a third threshold S3 in step IIIb. If this threshold is exceeded, a corresponding message is displayed to the user. Examples of this are shown in the Fig. 6 second areas B1 and B2 are marked in which the third threshold value S3 is exceeded. The value of the quality parameter change rate R is expediently used to identify a possible source of error in the manufacture of the electrical machines 2, i.e., to monitor the manufacturing process. If the value of the quality parameter change rate R is comparatively high, as in area B1, for example, this indicates a batch change or an abrupt change in the assembly device. If the value of the quality parameter change rate R is greater than the third threshold value S3, but comparatively low, this indicates a gradual change in the assembly device.

[0062] The invention is not limited to the exemplary embodiments described above. Rather, other variants of the invention can be derived from them by those skilled in the art within the scope of the claims without departing from the subject matter of the invention. In particular, all individual features described in connection with the exemplary embodiments and / or in the claims can also be combined with one another in other ways without departing from the subject matter of the invention. List of reference symbols 2 electric motor 4 Device 6 Rotor 8 Stator 10 12 first subsystem 14 second subsystem 16 Connection of the phase winding 18 conductors 20 Contacting device 22 Drive 24 Current sensor 26 Control device 28 Evaluation unit 30 Output device 32 Connection of the contact device B1,B2 area I U , I V , I W Current through the electrically connected phase windings G U , G V G W quantity characterizing the current M mean U1, V1, W1, U2, V2, W2 phase winding Q Quality parameters R rate of change S1 first threshold S2 second threshold S3 third threshold

Claims

[1] Method for determining a quality parameter (Q) of an electrical machine (2) having a rotor (6) and a stator (8), wherein the stator (8) has two subsystems (12, 14) each having three phase windings (U1, V1, W1, U2, V2, W2), wherein a phase winding (U2, V2, W2) of the second subsystem (14) is in phase with each phase winding (U1, V1, W1) of the first subsystem (12), - wherein phase windings (U1, V1, W1, U2, V2, W2) of the first subsystem (12) and the second subsystem (14) in phase are electrically connected to one another by means of a contacting device (20), - wherein the rotor (6) is externally driven, - where a current (I U , I V , I W ) is measured between the electrically connected phase windings (U1, V1, W1, U2, V2, W2), and - where for the currents (I U , I V , I W) each have a characteristic size (G U , G V G W ) and based on at least one of the quantities (G U , G V , G W ) of the quality parameter (Q). [2] Method according to claim 1, characterized by that the characteristic quantity (G) is an amplitude or the effective value of the respective current (I U , I V , I W ) is determined. [3] Method according to claim 1 or 2, characterized by that the mean value (M) of the quantities (G U , G V , G W ) as the quality parameter (Q). [4] Method according to one of claims 1 to 3, characterized by that a first threshold value (S1) is specified for the quality parameter (Q), wherein the electrical machine (2) is marked as a non-correct part if the quality parameter (Q) exceeds the first threshold value (S1). [5] Method according to one of claims 1 to 4, characterized by that a second threshold value (S2) is specified for the quality parameter (Q), wherein a warning is issued if the quality parameter (Q) exceeds the second threshold value (S2). [6] Method for controlling the manufacturing process of electrical machines (2), - wherein for several electrical machines (2) which were manufactured consecutively, a quality parameter (Q i ) is determined according to the method according to any one of claims 1 to 5, and - whereby, based on the determined quality parameters (Q i ) a quality parameter change rate (R) is determined. [7] Device (4) for determining a quality parameter (Q) of an electrical machine (2) which has a rotor (6) and a stator (8), wherein the stator (8) has two subsystems (12, 14) each with three phase windings (U1, V1, W1, U2, V2, W2), wherein a phase winding (U2, V2, W2) of the second subsystem (14) is in phase with each phase winding (U1, V1, W1) of the first subsystem (12), comprising - a contacting device (20) for electrically connecting in-phase phase windings (V1, W1, U2, V2, W2) of the first subsystem (12) and the second subsystem (14), - a drive (22) for rotating the rotor (6), - Current sensors (24) for measuring the (respective) currents (I U ,I V ,I W ) between the phase windings (V1, W1, U2, V2, W2) electrically connected to one another by means of the contacting device (20) - means (26,16,30) for carrying out the method according to one of claims 1 to 5.

Images