MEASURING ARRANGEMENT

Description

[0001] The invention relates to a measuring arrangement for an electric machine, in particular an electric motor. In exemplary embodiments, a brushless DC motor (BLDC) or a synchronous machine can be used as the electric motor. However, the invention is also fundamentally suitable for other electric machines. The electric machine is controlled by a control unit. The control unit can, for example, include an inverter or converter to set a phase current and / or a phase voltage for each phase.

[0002] DE 10 2016 106 431 A1 describes a measuring arrangement comprising several two-terminal networks, each with a capacitance and a temperature-dependent impedance. The two-terminal networks are connected in parallel to the motor windings of an electric machine. The electric motor is controlled by a frequency converter. No additional wires are required to connect the two-terminal networks. The current response when current is switched on through one of the motor windings is influenced by the temperature-dependent impedance of the two-terminal network connected in parallel to the motor winding and can be evaluated to determine the temperature at the installation location of the two-terminal network.

[0003] From DE 10 2017 108 112 A1, a measurement method for determining the winding temperature of a motor winding of an electric motor is known. For this purpose, the motor winding is excited by means of high-frequency oscillation and a resonant oscillation is generated. The resulting resonant frequency is determined and the winding temperature is calculated from the resonant frequency.

[0004] From EP 2 211 455 A2, a single-phase induction motor is known in which the number of turns of a main or auxiliary winding can be varied by means of a variable resistance element to enable the induction motor to start. The resistance element can be a PTC element which, after the induction motor has started, exhibits an increased resistance with rising temperature, so that a part of the main winding short-circuited by the PTC element for starting is activated.

[0005] A motor with an inverter is described in DE 10 2007 043 872 A1. The inverter controls the motor depending on a speed and a temperature. Temperature sensors are provided to measure the temperature; their sensor signals are forwarded to the inverter via a multiplexer in the motor.

[0006] WO 2019 / 154801 A1 concerns a control unit for controlling an electric motor with an interface for connecting a measuring resistor. The resistance value of the measuring resistor is evaluated for temperature monitoring of the electric motor.

[0007] Based on the state of the art, a measuring arrangement for determining a parameter to be defined is to be created, which enables the transmission of measured values ​​to a control unit without additional transmission lines.

[0008] This problem is solved by a measuring arrangement with the features of claim 1.

[0009] The measuring arrangement serves to detect a parameter to be measured, for example, temperature, humidity of an surrounding atmosphere, acceleration in at least one spatial direction, another physical parameter, or any combination of several of the aforementioned parameters, on or in an electric machine. In one embodiment, the electric machine can be an electric motor. Brushless DC motors (BLDC) or synchronous motors, for example, are used as electric motors. The electric machine is preferably controlled by a control unit, which may, for example, include an inverter or converter or another suitable control circuit. In particular, the control unit is configured to generate a rotating stator magnetic field.The control unit can have a control output for each existing phase train of the electric machine, with the control output being electrically connected to the respective assigned phase train of the electric machine via a control line.

[0010] Each phase of the electric machine has at least one, preferably at least two, windings connected in series. Each winding is arranged, in particular, around a tooth of the stator and configured to generate a substantially radially oriented magnetic field, in particular a stator magnetic field.

[0011] The measuring arrangement includes a measuring circuit. The measuring circuit has a coupling branch and a sensor coupled to the coupling branch. The sensor is configured to change a sensor value depending on the parameter being measured. This sensor value is thus available to the measuring circuit, which is configured to influence the coupling branch impedance depending on the sensor value and therefore depending on the parameter being measured. For example, the coupling branch impedance can be changed between two or more states, such as between a conducting and a blocking state, or more generally between states with differing coupling branch impedances. The coupling branch is coupled to at least one or exactly one of the windings of one of the existing phase strands without a galvanic connection (e.g., inductively).The coupling branch is implemented without a galvanic connection to at least one winding and therefore without a galvanic connection to the electrical machine.

[0012] Regardless of the type of coupling or connection, the coupling branch impedance, which can be influenced by the parameter being measured, affects the overall impedance of the phase train. This allows at least temporary changes in electrical quantities to be generated, which in turn can be detected at the electrical terminals of the phase train. An evaluation unit can detect and evaluate the at least one variable electrical quantity at the existing electrical terminals of the phase train. The measuring circuit can modify the relevant electrical quantity, at least temporarily, in such a way that data or information, describing in particular the sensor value, is transmitted to the evaluation unit. Thus, a sensor value or the value of the parameter to be measured can be transmitted. The phase train is therefore also used for data transmission via the measuring arrangement according to the invention, in addition to generating a magnetic field in the electric machine.

[0013] The at least one variable electrical quantity can, for example, have one or more of the following properties: a phase angle of the phase current in relation to the phase voltage for the phase string and / or a gradient of the phase current when switching on and / or off the phase current and / or an magnitude of the phase current and / or an magnitude of the phase voltage of the phase string in question and / or a total impedance of the phase string or a related electrical quantity. Changing the overall impedance of the phase train can trigger several effects, which in turn can be measured. For example, the rotational speed can be changed (e.g., reducing the rotational speed by decreasing the overall impedance), the inductance of the phase train can be altered, and / or the symmetry relationships between the existing phase trains can be changed.

[0014] The measuring circuit can also modulate its state or coupling branch impedance between two or more values ​​or magnitudes, so that, for example, multiple sensor values ​​or more complex data or information about the phase train from the electric machine can be easily transmitted to the outside.

[0015] The measuring setup can also include multiple measuring circuits. These can be assigned to different phase strands or different windings.

[0016] It is advantageous if the sensor of the measuring circuit is arranged in the coupling branch, so that a simple change in the coupling branch impedance is possible due to the sensor value. The sensor can, for example, be a resistor that varies depending on the parameter being measured, or it can have such a resistance. The sensor can also be designed as a switching sensor that establishes a conductive connection when the parameter being measured exceeds a threshold value and blocks the electrical path through the coupling branch when the parameter being measured falls below the same or a different threshold value (switching sensor with or without hysteresis). In these configurations, the sensor is, for example, connected in series or parallel with the coupling branch impedance, or is part of the coupling branch impedance.

[0017] Preferably, the coupling branch impedance has a resistive component and / or an inductive component. It is preferred if the coupling branch impedance has no capacitive component. This ensures that the phase current does not lead the phase voltage. In a preferred embodiment, the resistive component of the coupling branch impedance predominates. For example, both the capacitive and the inductive components can each represent a maximum of 10% or a maximum of 5% of the total coupling branch impedance. In particular, both the capacitive and the inductive components can be negligibly small.

[0018] The measuring circuit can maintain the coupling branch in a state where the branch current through the coupling branch is less than the winding current through the at least one winding coupled to the coupling branch, as long as the parameter to be measured is within a non-critical range. For example, the branch current can be a maximum of 10% or a maximum of 5% of the winding current, as long as the parameter to be measured is within a non-critical range. A non-critical value range for the parameter to be measured can be predefined or set.

[0019] In one embodiment, the measuring circuit can include a switch that can be toggled between a conducting state and a blocking state by means of a control signal. The switch is preferably arranged in the coupling branch. The switch can be a controllable semiconductor switch, for example, a field-effect transistor or a bipolar transistor.

[0020] The measuring circuit can be configured to generate the control signal for the switch depending on the sensor value or the parameter being measured. For example, the control signal can cause the switch to toggle when a threshold value for the sensor value or the parameter being measured is reached (with or without hysteresis between switching to the conducting and blocking states). The control signal can also transmit more complex information, such as multiple sensor values, and toggle the switch between the conducting and blocking states, for example, for encoding purposes. In this way, information can be transmitted through modulation or encoding.

[0021] In one embodiment, the coupling branch can have an additional winding around at least one, and preferably exactly one, tooth of the electric machine. This allows inductive coupling between the additional winding of the coupling branch and the at least one winding of the phase strand of the electric machine that is arranged on the tooth. The tooth is, for example, a component of the stator of the electric machine. A separate tooth can be provided for each winding of a phase strand. The additional winding can have a single turn or several turns. Preferably, the number of turns of the additional winding is significantly smaller (e.g., at least two to three times smaller) than the number of turns of the parallel-connected winding of the phase strand.

[0022] The measuring circuit can thus be an integral part of the electric machine, but without a galvanic connection to it. Apart from the additional winding, other components of the measuring circuit can be arranged on a common substrate, for example, a common printed circuit board, which is located adjacent to the tooth or winding of the phase strand on or in the electric machine.

[0023] Advantageous embodiments of the invention will become apparent from the dependent claims, the description, and the drawings. Preferred embodiments of the invention are explained in detail below with reference to the accompanying drawings. The drawings show: Figure 1 a block diagram of an electric machine controlled by a control unit showing a measuring circuit, Figures 2 and 3each an electrical block diagram or equivalent circuit diagram of an electrical phase train of the electric machine from Figure 1 each with an exemplary embodiment of a measuring circuit, Figure 4 a schematic representation of an embodiment of an electric machine viewed along an axis of rotation, wherein a measuring circuit is arranged on one tooth and Figure 5 A phasor diagram to illustrate the phase shift between a phase voltage and a phase current through a phase strand of the electrical machine.

[0024] Figure 1 Figure 1 shows a block diagram of an electrical machine 10 having several phase strands 11, for example a first phase strand 11u, a second phase strand 11v and a third phase strand 11w. If the reference symbol 11 is used for the phase strand without an additional letter designation, the statements apply to several or all phase strands 11u, 11v, 11w.

[0025] The electric machine 10 can, for example, be an electric motor, such as a brushless DC motor or a synchronous machine. In Figure 4 The figure shown is merely an exemplary and schematic embodiment of a brushless DC motor. Permanent magnets 13 are arranged circumferentially on a rotor 12 that rotates about an axis D. These magnets can, for example, be magnetized circumferentially around the axis D. A stator 14 of the electric machine 10 has teeth 15 arranged circumferentially around the axis D. In this exemplary embodiment, six teeth 15 are shown. The number of teeth 15 can also be greater, for example, 12. The number of teeth 15 is preferably even.

[0026] At least one or exactly one winding 16 is arranged on each tooth 15. In the illustrated embodiment, each phase strand 11 has two windings 16, whereby the number of windings 16 in each phase strand 11 can also be smaller or larger. The windings 16 opposite each other with respect to the axis of rotation D belong to a common phase strand 11. The windings 16 are connected in series with each other. In the equivalent circuit diagram, each winding 16 can be formed by a series connection of a winding resistance RW and a winding inductance LW. The winding resistance RW is an ohmic resistance. The following applies to the winding impedance ZW of each winding 16: ZW = RW + jωLW where ω is the angular frequency and j denotes the imaginary part.

[0027] The electric machine 10 is controlled by a control unit 20. The control unit 20 is configured to individually adjust a phase voltage US and / or a phase current IS for the respective first phase 11u, second phase 11v, and third phase 11w. This allows, in particular, the generation of a stator magnetic field rotating around the axis of rotation D, in order to rotate the rotor 12, which is equipped with permanent magnets 13, around the axis of rotation D. The control unit 20 can, for example, incorporate an inverter circuit for this purpose.

[0028] The electric machine 10 is equipped with a measuring arrangement 21. The measuring arrangement 21 has at least one measuring circuit 22, which is assigned to one of the phase strands 11 and, for example, to the first phase strand 11u. The measuring circuit 22 could also be assigned to one of the other phase strands 11v, 11w. The measuring circuit 22 is in the Figure 1 and 4only presented in a highly schematic way.

[0029] As is particularly evident in the Figures 2 and 3 As can be seen, the measuring circuit 22 has a coupling branch 23 coupled to one of the windings 16. For example, the coupling branch 23 is coupled to at least one winding 16 without a galvanic connection. The coupling branch 23 thus allows the overall impedance ZG of the relevant phase strand 11 (for example, the first phase strand 11u) to be influenced. The coupling branch 23 has a coupling branch impedance ZK, which is variable. The following generally applies to the overall impedance ZG of the phase strand 11: ZG = ZW + ZW ⋅ ZK ZW + ZK

[0030] The total impedance ZG or an electrical quantity influenced by the total impedance ZG, for example the phase current IS and / or the phase voltage US, can be detected by an evaluation unit 24 of the control unit 20. In the exemplary embodiment, the evaluation unit 24 of the control unit 20 is thus part of the measuring arrangement 21. In a modified embodiment, the evaluation unit 24 could also be arranged as a separate component outside the control unit 20 and connected to the control lines leading to the phase strands 11.

[0031] The measuring circuit 22 also has a sensor 25 whose sensor value varies depending on a parameter P to be measured. For example, the sensor 25 can be a variable resistor whose resistance value changes depending on the parameter P. The sensor can, for example, be a temperature-dependent resistor if the temperature is to be measured as parameter P. The sensor 25 can also have a switching characteristic, according to which its resistance value or conductance changes in steps between two or more states depending on the parameter P, for example, between a low-resistance conducting state and a blocking state. For this purpose, the sensor 25 can, for example, have a semiconductor that can assume at least two different states, such as a diode, a transistor, or a thyristor, or alternatively another switch, such as a bimetallic switch.

[0032] In addition to or as an alternative to temperature T, another physical quantity can also be measured as parameter P, for example, the humidity in the surrounding atmosphere or an acceleration in at least one spatial direction. Sensor 25 can also detect any combination of different parameters P.

[0033] At the in Figure 2 In the illustrated embodiment, the sensor 25 is arranged in the coupling branch 23. The sensor 25 is configured to change its resistance value depending on the parameter P, either in steps between at least two levels or according to a continuous characteristic. This changes the coupling branch impedance ZK, which in this embodiment is essentially or exclusively formed by the impedance of the sensor 25, depending on the parameter P being measured. Consequently, the total impedance ZG also changes depending on the parameter being measured. P.This change can be determined by the evaluation unit 24. Therefore, it is possible to transmit the parameter P to be measured to the evaluation unit 24 or the control unit 20 via the electrical connections of the phase train 11 (here: first phase train 11u).

[0034] An additional impedance of 30 can optionally also be added in the embodiment shown below. Figure 2 to be connected in series with sensor 25.

[0035] The design of the measuring circuit 22 can vary. Another embodiment is shown in Figure 3The measuring circuit 22 is shown in the figure. It includes a switch 29 that can be controlled by a control signal S. Depending on the control signal S, the switch 29 can be in a conducting or a blocking state. The switch 29 can be, for example, a semiconductor switch, in particular a bipolar transistor or a field-effect transistor. Thus, the parallel current path through the coupling branch 23 can be enabled or completely blocked depending on the switching state of the switch 29. Optionally, an ohmic resistor and / or an inductor with an additional impedance 30 can be connected in series with the switch 29, which then essentially defines the coupling branch impedance ZK in the conducting state of the switch 29.

[0036] The measuring circuit 22 is located in the Figure 3The illustrated embodiment is configured to generate the control signal S depending on the sensor value of sensor 25 and thus depending on the parameter P to be measured. In a simple case, switching the switch 29 using the control signal S can indicate, for example, that a predefined threshold value has been exceeded by the sensor value or the parameter P. Alternatively, the control signal S can also switch the switch 29 between the conducting and blocking states according to a predefined modulation or code, so that more complex information, such as arbitrary sensor values ​​or values ​​for the parameter P to be measured, can be transmitted to the evaluation unit 24 via binary encoding or modulation. The value for the parameter P to be measured can then be retrieved in the evaluation unit 24 by demodulation or decoding.In this way, for example, a serial transmission of a bit sequence to the evaluation unit 24 can take place.

[0037] As it is in Figure 3 As can be seen, in this embodiment the sensor 25 can be arranged outside the coupling branch 23 and be indirectly connected to the coupling branch and, for example, to the controllable switch 29.

[0038] By changing the total impedance ZG depending on the parameter P, one or more of the following electrical quantities can be influenced, which can be detected by the evaluation unit 24 in order to obtain the transmitted value for the parameter P to be measured: the magnitude of the phase current IS and / or the phase voltage US; the total impedance ZG or the inductance of the phase phase 11 to which the measuring circuit 22 is coupled; the gradient of the phase current IS when a phase voltage US is applied to the phase phase 11 in question; a phase shift φ between the phase voltage US and the phase current IS ( Figure 5 ); the behavior of the electrical machine 10 when an alternating voltage is applied as phase voltage US, in particular a high-frequency alternating voltage. In addition to or as an alternative to at least one electrical quantity, other physical quantities can also be recorded by the evaluation unit, for example the rotational speed of the electric machine, which can change depending on the total impedance ZG.

[0039] As it is in Figure 4As schematically illustrated, the coupling branch 23 of the measuring circuit 22 can have an additional winding 31 or be formed by an additional winding 31 arranged on the tooth 15, which carries the winding 16 of the associated phase strand 11, for example the first phase strand 11u, coupled to the coupling branch 23. The additional winding 31 can have one or more turns. A carrier 32 can be arranged on the additional winding 31 and mechanically and electrically connected to it. The carrier 32 can, for example, be designed as a printed circuit board. Further components, and preferably all other components of the measuring circuit 22, can be arranged on the carrier 32 (see Figure 1). Figures 3 and 4 ).

[0040] The invention relates to a measuring arrangement 21 comprising a measuring circuit 22 arranged on or in an electric machine 10, and an evaluation unit 24 arranged outside the electric machine 10 and connected to one of the phase strands 11 of the electric machine 10. The existing electrical connections of the phase strand 11 are used for this purpose. The measuring circuit 22 has a sensor 25 which can continuously or stepwise change its sensor value depending on a parameter P to be measured. The sensor 25 is coupled to a coupling branch 23 of the measuring circuit 22, which in turn is coupled to at least one of the windings 16, preferably of a single phase strand 11, without a galvanic connection to the winding 16, for example, inductively.The measuring circuit 22 is configured to influence a coupling branch impedance ZK of the coupling branch 23, at least temporarily, depending on the sensor value and thus the parameter P, thereby changing the overall impedance ZG of the phase train 11. The influence on the overall impedance ZG can be detected by the evaluation unit 24. In this way, a signal describing the parameter P can be transmitted to the evaluation unit 24 via the electrical connections of the phase train 11. Reference symbol list:

[0041] 10 electric machine 11 phase strand 11 first phase strand 11 second phase strand 11 third phase strand 12 rotor 13 permanent magnet 14 stator 15 tooth 16 winding 20 Control unit 21 Measuring arrangement 22 Measuring circuit 23 Coupling branch 24 Evaluation unit 25 Sensor 29 Switch 30 Additional impedance 31 Additional winding 32 Carrier φPhase shift D Rotation axis ISS phase current LW winding inductance P Parameter RW winding resistance S Control signal US Phase voltage ZG total impedance of phase phase ZK coupling branch impedance ZW winding impedance

Claims

1. Measuring assembly (21) of an electrical machine (10) comprising: - at least one phase (11) of the electrical machine (10) comprising at least one winding (16), - a measuring circuit (22) comprising a coupling branch (23) coupled with at least one of the windings (16) and a sensor (25) coupled with the coupling branch (23), wherein the measuring circuit (22) is configured to influence a coupling branch impedance (ZK) of the coupling branch (23) depending on a parameter (P) to be measured by means of the sensor (25), characterized in that the coupling branch (23) is coupled with the at least one winding (26) in a galvanically isolated manner.

2. Measuring assembly according to claim 1, wherein each phase (11) of the electrical machine (10) comprises a series connection of at least two windings (16).

3. Measuring assembly according to claim 1 or 2, wherein the sensor (25) is arranged in the coupling branch (23).

4. Measuring assembly according to any of the preceding claims, wherein the sensor (25) comprises a resistance depending on the parameter (P) to be measured.

5. Measuring assembly according to any of the preceding claims, wherein the coupling branch (23) comprises a coupling branch impedance (ZK) having an ohmic component and / or an inductive component.

6. Measuring assembly according to claim 4, wherein the coupling branch impedance (ZK) does not comprise a capacitive component.

7. Measuring assembly according to any of the preceding claims, wherein the measuring circuit (22) comprises a switch (29) that can be switched by means of a control signal (S) between a conductive and a blocking condition.

8. Measuring assembly according to claim 6, wherein the measuring circuit (22) is configured to create the control signal (S) depending on the parameter (P) to be measured by means of the sensor (25).

9. Measuring assembly according to any of the preceding claims, wherein the coupling branch (23) comprises an additional winding (31) by means of which the coupling branch (23) is inductively coupled with the at least one winding (16).

10. Measuring assembly according to claim 9, wherein the additional winding (31) is arranged around a tooth (15) of the electrical machine (10) on which the winding (16) is arranged that is coupled to the coupling branch (23).

11. Measuring assembly according to any of the preceding claims, comprising in addition a control device (20), which is configured to control the phase current (IS) and / or the phase voltage (US) for the at least one phase (11) of the electrical machine (10).

12. Measuring assembly according to any of the preceding claims, comprising in addition an evaluation unit (24) that is configured to determine the total impedance (ZG), which is formed by the coupling branch impedance (ZK) of the coupling branch (23) and the winding impedance (ZW) of the winding (16) connected in parallel thereto.

13. Measuring assembly according to claim 11 and according to claim 12, wherein the evaluation unit (24) is part of the control device (20).