MEASUREMENT ASSEMBLY FOR A TRANSDUCER, AND TRANSDUCER ASSEMBLY - Patent application

Abstract

A measuring assembly for determining bridge currents of a switched electrical converter unit (2), in which at least two electronic half-bridges (3, 3') are switched by a control unit (4) by means of control signals offset in time in a modulated manner, comprising a measuring unit (1) connected to current sensors (6, 6'), the current sensors (6, 6') being arranged to measure the bridge currents in the output lines or input lines of the half-bridges (3, 3'), the measuring unit (1) being connected to the control unit (4) for time synchronization, and the measuring unit (1) being configured to define measurement instants (8, 8') of the current sensors (6, 6') that are synchronized in time with the control signals of the half-bridges (3, 3'), as well as a converter assembly having such a measuring assembly.

Description

[Technical Field]

[0001] The present invention relates to a measurement assembly for a transducer, as well as to a transducer assembly having a measurement assembly of such kind. [Background technology]

[0002] The prior art has known measuring assemblies for determining the power delivered by an electrical converter. Typically, current and voltage are measured on the AC or DC side of the converter, and the power delivered is determined based on these. This is possible with high accuracy in the case of undisturbed harmonic signals.

[0003] However, in converter assemblies with high-frequency switching converter units, such measurement assemblies can lead to inaccurate results. Such high-frequency switching converter units comprise multiple electronically controlled half-bridges, which are switched on and off by an electronic control unit using time-offset control signals, e.g., pulse-width modulation (PWM). In a PWM inverter, for example, the semiconductor switches of the half-bridges switch the input voltage on and off at a high, time-variably controlled switching frequency. The resulting AC voltage is therefore made up of a combination of small pulses of different widths, which are passed through a throttle, resulting in an approximately sinusoidal output current. The switching frequency of the half-bridges is significantly higher than the frequency of the useful signal.

[0004] These high switching frequencies are reflected in the generated output signal, which is therefore accompanied by harmonics. The switched electrical output and other electrical characteristics are difficult to determine in these types of converters, since harmonics cause losses. For example, determining the working point and efficiency is difficult if electrical parameters are measured at the machine input, because such measurements must be performed in a specific frequency range and do not take into account harmonic output. This results in large uncertainties in the characteristics and machine parameters required for controlling the electrical machine. It is virtually impossible to determine nonlinear effects related to current or switching frequency. Summary of the Invention [Problem to be solved by the invention]

[0005] For these and other reasons, there exists a need for a measurement assembly for accurately determining the electrical output and other characteristic quantities switched in a switching transducer. This and other problems are solved according to the present invention by the measurement assembly set forth in claim 1. [Means for solving the problem]

[0006] The measuring assembly according to the invention is configured to determine the electrical output of a switched electrical converter unit, in which at least two electronic half-bridges are switched by a control unit using time-offset control signals in a modulated manner. Each half-bridge can have two semiconductor switches, in particular SiC or GaN semiconductor switches. Such semiconductor switches can be composed of multiple components, in particular including freewheeling diodes arranged in a parallel circuit.

[0007] The conversion unit converts, for example, DC voltage V dc AC voltage V acThe conversion unit may be a switched inverter assembly for converting an AC voltage V ac DC voltage V dc Further, the conversion unit may be a switching DC voltage converter for converting a first DC voltage V1 into a second DC voltage V2.

[0008] The measurement assembly according to the present invention includes a measurement unit connected to a current sensor configured to measure the bridge current in the output or input line of the half bridge of the converter unit. For this purpose, an interface of the converter unit can be used. The current sensor can be a high-dynamic sensor whose measurement frequency is at least as high as or higher than the switching frequency of the PWM method. The current sensor can be arranged in the output or input line of the half bridge of the converter unit.

[0009] The control unit and the measurement unit may be configured as an electronic data processing unit. The control unit and the measurement unit may be configured as separate, independent units, so that an existing transducer assembly with a control unit can be complemented by a compatible measurement unit for output measurement. Alternatively, the control unit and the measurement unit may be integrated into a common unit.

[0010] The measurement unit is connected to the control unit for time synchronization, so that the time points of the PWM control signals defined by the control unit can be transmitted to the measurement unit.

[0011] The measuring unit is configured to define measurement times of the current sensors that are synchronized in time with the control signals of the half bridges. This ensures that the measured values ​​of the current sensors are taken into account when the corresponding half bridges are activated, i.e., when they are energized. In this way, the current supplied or drawn by the half bridges can be measured with each pulse of the PWM method. Therefore, when calculating the electrical output, the current of each individual half bridge of the converter unit can be taken into account, which results in a more accurate output measurement than if only the resulting total current were taken into account. This, in particular, allows the dead time between each bridge switch to also be taken into account.

[0012] The measurement unit may be configured to query the current sensor at a measurement frequency that corresponds approximately to the frequency of the control signal. In this case, the control unit or the measurement unit predefines a measurement instant that is located in time substantially in the middle of the turn-on time of the control signal. Alternatively, the measurement unit may be configured to query the current sensor at a measurement frequency that is higher than the frequency of the control signal. In this case, the measurement unit obtains multiple measurement values ​​during one PWM pulse and predefines a measurement instant that is located in time substantially in the middle of the turn-on time t of the control signal. on The measuring unit subsequently selects a measuring time point that is located in the middle of the PWM pulse. In this case, the measuring unit may be configured to query the sensor current at multiple measuring time points during the turn-on time of the control signal and average the resulting measured values ​​over one PWM pulse, thereby allowing a particularly accurate measurement of the average current value of the PWM pulse.

[0013] According to the present invention, the measuring unit may be connected to at least one DC voltage sensor arranged on the DC voltage side of the converter unit. The measuring unit may be configured to determine the switched electrical power from the measured bridge current and the DC voltage measured on the DC voltage side. In principle, the direction of the power flow is irrelevant; the converter unit may be configured as a converter or inverter. The total electrical power transmitted during one period of the useful signal can be calculated as the sum of the individual current values ​​measured at the PWM pulses multiplied by the measured DC voltage, with respect to the duration of each PWM pulse relative to the duration of the useful signal period. In the case of a multiphase converter unit, such a calculation can also be performed for each phase of the converter unit to determine the electrical power supplied or procured per phase.

[0014] Furthermore, the measuring unit may be configured to take into account the electrical internal resistance of the semiconductor switch and other electronic components of the half-ridge, for example a freewheeling diode connected in parallel, when calculating the electrical output of the conversion unit.

[0015] Furthermore, according to the invention, it may be provided that the measuring unit is also connected to a DC voltage sensor arranged on the DC voltage side of the converter unit, so that the measuring unit can calculate the electrical power supplied or delivered on the DC side, which can be compared with the electrical power calculated from the individual bridge currents on the AC side to calculate the electrical efficiency of the converter unit.

[0016] The invention further relates to a converter assembly comprising a measuring assembly according to the invention, wherein the conversion unit can be a switching converter assembly, a switching inverter assembly or a switching DC voltage converter, in which case the measuring unit is preferably integrated together with the control unit into a common data processing unit.

[0017] The conversion unit may be connected to an electric machine, for example an electric motor, a generator, etc. The measurement unit may likewise be connected to the electric machine.

[0018] In particular, the measuring unit may be configured to receive mechanical measured values ​​such as rotation speed, torque, acceleration, etc. and to calculate the mechanical power of the electric machine from these mechanical measured values. For this purpose, the measuring unit may be configured for connection to sensors external to the machine.

[0019] The measurement unit may be configured to receive thermal measurements such as the temperature of a motor winding of the electric machine, waste heat of a cooling medium, or a temperature difference, and the measurement unit may be configured to determine a mechanical power output of the electric machine from these thermal measurements.

[0020] The measurement unit may be configured to determine parameters of components of an electrical and / or mechanical equivalent circuit of the electric machine from the electrical or mechanical measurements.

[0021] Furthermore, the measurement unit may be configured to determine the efficiency of the electric machine from the calculated electrical output of the conversion unit and the calculated mechanical output of the electric machine, i.e. to determine the efficiency of the conversion from electrical output to mechanical output and vice versa.

[0022] The measurement unit may be configured to determine characteristic quantities, such as the active power, reactive power or power coefficient of the electric machine, which are derived from the electrical and mechanical measurements.

[0023] In particular, the converter assembly may be intended for application in industrial applications, on vehicle test stands or in vehicles. It is particularly preferred that the converter units of the converter assembly can also source or supply DC voltage from a DC voltage intermediate circuit of the test stand. In the case of test stand applications, a DC voltage sensor can preferably be arranged in a central DC voltage intermediate circuit in order to allow easy calculation of the electrical power sourced or supplied by the converter units.

[0024] Other features of the invention will become apparent from the claims, the drawings and the following description.The invention will now be described with reference to non-exclusive embodiments. [Brief explanation of the drawings]

[0025] [Figure 1a] FIG. 1a shows an example of an embodiment of a measurement assembly according to the invention as a schematic block diagram including an electric machine. [Figure 1b] FIG. 1b shows an example of an embodiment of a measurement assembly according to the invention as a schematic circuit diagram. [Figure 1c] FIG. 1c shows as a schematic circuit diagram another example of an embodiment of a measurement assembly according to the invention. [Figure 2a] FIG. 2a shows diagrammatically the course of the control signal and the resulting current in the output line of the half-bridge in an embodiment of the measurement assembly according to the invention. [Figure 2b] FIG. 2b shows diagrammatically the course of the control signal and the resulting current in the output line of the half-bridge in another embodiment of the measurement assembly according to the invention. [Figure 3] FIG. 3 shows, as a schematic circuit diagram, an example of another embodiment of a measurement assembly according to the invention. [Figure 4] FIG. 4 shows, as a schematic block diagram, an example of an embodiment of a transducer assembly according to the present invention. [Figure 5]FIG. 5 shows an example of an embodiment of a measurement assembly according to the present invention as a schematic block diagram including an inverter assembly. [Figure 6] FIG. 6 shows an example of an embodiment of a measurement assembly according to the invention as a schematic block diagram including a switched DC voltage converter. DETAILED DESCRIPTION OF THE INVENTION

[0026] 1a shows an example of an embodiment of a measurement assembly according to the invention as a schematic block diagram. The measurement assembly comprises an electronic measurement unit 1 interfaced with current sensors 6, 6′ (not shown) in an electrical conversion unit 2.

[0027] Furthermore, the measuring unit 1 is interfaced with sensors for measuring mechanical quantities of the electric machine 7, i.e. the speed, acceleration, torque, waste heat etc. of the electric machine.

[0028] In this embodiment, the conversion unit 2 converts the DC voltage V1 provided by the battery into an AC voltage V for operating the electric machine 7. ac The converter unit 2 includes two electronic half-bridges 3, 3' which are switched by an electronic control unit 4 with control signals offset in time in a modulated manner. In this embodiment, the control unit 4 and the measurement unit 1 are configured as separate units. The control unit 4 calculates trigger times for controlling the electronic half-bridges 3, 3' of the converter unit 2 and provides these to the converter unit 2. Current sensors 6, 6' are arranged to measure the bridge currents in the output or input lines of the half-bridges 3, 3' of the converter unit 2.

[0029] The measuring unit 1 is connected to the control unit 4 for time synchronization and is configured to define measuring instants 8, 8' of the current sensors 6, 6' that are time-synchronized with the control signals of the half-bridges 3, 3', so that the measuring unit 1 can detect the current values ​​exactly when the PWM control signals activate the respective half-bridges.

[0030] 1b shows an example of an embodiment of a measuring assembly according to the invention as a schematic circuit diagram. The circuit diagram shows the internal structure of a converter unit 2, which operates as an inverter. The half-bridges 3, 3' each contain two electronic semiconductor switches, i.e., SiC or GaN transistors Q1, Q2, Q1', Q2', in parallel with a freewheeling diode (not shown for reasons of clarity). The semiconductor switches are connected to a control unit 4 via control lines.

[0031] On the input side, i.e., on the side of the DC voltage V1, a DC voltage sensor 10 is arranged. On the output side, i.e., on the side of the AC voltage V ac On the other side, highly dynamic current sensors 6, 6' are arranged in both output lines of the half-bridges 3, 3'. The DC voltage sensor 10 and the current sensors 6, 6' are connected via data lines to the measurement unit 1. The control unit 4 provides trigger signals to the measurement unit 1, allowing the synchronization of the PWM control signals and the current measurements.

[0032] Figure 1c shows as a schematic circuit diagram another example of an embodiment of a measurement assembly according to the invention, which substantially corresponds to that of Figure 1b, but in which the control unit 4 includes the measurement unit 1, in other words the functions of the measurement unit 1 are taken over by the control unit 4 in this example.

[0033] FIG. 2a shows a schematic diagram of the curve of the control signal for the switches Q1, Q2' or Q2, Q1' and the resulting curve of the current I3 in the output line of the left half-bridge 3 of the circuit of FIG. 1b. The PWM control signals of the switches are shown here as solid lines. The control unit 4 controls the semiconductor switches with PWM modulation signals to generate an approximately sinusoidal current curve in the output line. The dashed lines indicate the measurement times 8, 8' of the current sensors 6, 6'. In this example, the measurement unit 1 queries the current sensors at a frequency that corresponds approximately to the frequency of the control signals, so that a current measurement is performed for each PWM control signal. The current values ​​measured per period T are shown as dots. The period duration of the PWM control signal is designated by the symbol T.

[0034] The measuring unit 1 is now configured such that the expected course of the control signal is known and the turn-on time t on Therefore, in this embodiment, the current sensors 6, 6' must be designed for a frequency that corresponds to the frequency of the PWM control signal.

[0035] The electrical output of the transmitted output signal is determined by the number of half-bridges M and the output signal T out The average bridge current I measured per half-bridge as a sum over the number of PWM pulses N per period of i,j and the DC voltage V measured at the current pulse on the DC voltage side of the converter unit. 1,j and the DC voltage V measured at the current pulse. 1,j can sometimes be assumed to be constant.

number

[0036] The calculated transmitted electrical power can subsequently be compared with the mechanical power calculated from the mechanical quantities of the electric machine 7 .

[0037] From the ratio of the mechanical power to the electrical power, the efficiency of the electric machine 7 can be calculated. The mechanical power of the electric machine 7 can also be determined from the measured waste heat.

[0038] 2b shows the course of the control signal and the resulting course of the current in the output line of the half-bridge in a further embodiment of the measuring assembly according to the invention. In this example, the measuring unit 1 queries the current sensors 6, 6' at a measurement frequency that is significantly higher than the frequency of the control signal, as evidenced by the numerous dashed lines. Only later, i.e. in a post-processing step, is the current sensor 6, 6' interrogated at a measurement frequency that is substantially equal to the turn-on time t of the control signal. on The measuring unit 1 selects the measuring instant 8, 8' which is located in the center of the output signal. The transmitted electrical power of the output signal is again calculated according to the above formula. This allows for flexible adaptation of the power measurement to the PWM method; however, this requires the use of a highly dynamic current sensor.

[0039] FIG. 3 shows a schematic circuit diagram of another embodiment of a measuring assembly according to the invention. In this example, the conversion unit 2 is configured as a three-phase inverter that converts a DC voltage V1 into a three-phase AC voltage having three phases L1, L2, and L3 using six parallel-arranged half-bridges 3, 3', 3a, 3a', 3b, and 3b', electronically controlled by a control unit 4. Two half-bridges are connected via current-compensated interleaving throttles 9, 9', 9a, 9a', 9b, and 9b', ensuring smooth current flow between the half-bridges. Current sensors 6, 6', 6a, 6a', 6b, and 6b' are arranged in the output lines of each half-bridge; the input DC voltage is measured via a DC voltage sensor 10. In this embodiment, the measuring unit 1 is again integrated into the control unit 4. The measurement unit 1 is configured to calculate the electrical output of each phase L1, L2, L3 from the synchronized measurements of the current sensors 6, 6', 6a, 6a', 6b, 6b' and the DC voltage sensor 10.

[0040] 4 shows a schematic block diagram of an example embodiment of a converter assembly according to the invention. 1. The converter assembly comprises a measurement assembly and two conversion units 2, 2', which act as an inverter and a subsequent converter. In this embodiment, the measurement unit 1 is also integrated into the control unit 4. In each conversion unit 2, 2', two electronic half-bridges 3, 3' are switched by the control unit 4 with control signals that are offset in time in a modulated manner. The two conversion units 2, 2' thus jointly form a DC voltage converter, which converts a DC voltage V1 into a DC voltage V2.

[0041] In each of the two converter units 2, 2', the input or output current of the half-bridge is measured synchronously with the control signal via current sensors 6, 6'; the DC voltages V1 and V2 are also measured. This allows the electrical outputs of the two converter units 2, 2' to be measured separately from each other, and the efficiency of each converter unit 2, 2' to be determined. Furthermore, in this embodiment, DC voltage sensors 5, 5' are provided on the input and output sides. These are used to calibrate the dynamic current sensors 6, 6' arranged in the converter units 2, 2'; for this purpose, a predefined load is connected to the output side.

[0042] The present invention is not limited to the present embodiment, but includes any apparatus and method that falls within the scope of the following claims. In particular, the present invention is not limited to the application of pulse width modulation with a fixed switching frequency, but also includes the application of pulse width modulation with a variable switching frequency.

[0043] The terms used herein should not be construed in a narrow sense: the specific circuit technology implementation of the inverter or converter assembly is not part of the invention.

[0044] The conversion units in the form of inverter assemblies or converter assemblies or DC voltage converters contemplated according to the present invention may always be intended for internal electrical isolation and may be intended for medium to high electrical power outputs, for example in the range of 10 kW to 100 kW under DC voltages of 12 V, 24 V, 48 V, 230 V or 850 V, or for AC voltage outputs of up to 300 kVA.

[0045] Figure 5 shows as a schematic block diagram an example of an embodiment of a measuring assembly according to the invention. This example differs from that described in Figure 1a in that an inverter assembly 11 is tested instead of an electric machine 7. The measuring assembly comprises an electronic measuring unit 1 interfaced with current sensors 6, 6' (not shown) in an electrical conversion unit 2.

[0046] Furthermore, the measuring unit 1 measures the electrical quantity of the inverter assembly 11 to be tested, i.e., the direct current I dc and DC voltage V dc The sensor is connected via an interface to measure the temperature.

[0047] In this embodiment, the conversion unit 2 converts a DC voltage V1 provided from a battery into an AC voltage V2 for operating the inverter assembly 11 to be tested. ac The converter unit 2 includes two electronic half-bridges 3, 3' which are switched by an electronic control unit 4 with control signals offset in time in a modulated manner. In this embodiment, the control unit 4 and the measurement unit 1 are configured as separate units. The control unit 4 calculates trigger times for controlling the electronic half-bridges 3, 3' of the converter unit 2 and provides these to the converter unit 2. Current sensors 6, 6' are arranged to measure the bridge currents in the output or input lines of the half-bridges 3, 3' of the converter unit 2.

[0048] The measuring unit 1 is connected to the control unit 4 for time synchronization and is configured to define measuring instants 8, 8' of the current sensors 6, 6' that are time-synchronized with the control signals of the half-bridges 3, 3', so that the measuring unit 1 can detect the current values ​​exactly when the PWM control signals activate the respective half-bridges.

[0049] The inverter assembly 11 to be tested is in particular a converter attached to an electric machine.

[0050] 6 shows as a schematic block diagram an example of an embodiment of a measuring assembly according to the invention, in which a switching DC voltage converter 12 is tested. The measuring assembly comprises an electronic measuring unit 1, which is interfaced with current sensors 6, 6′ (not shown) in an electrical conversion unit 2.

[0051] Furthermore, the measuring unit 1 measures the electrical quantity, i.e., the DC current I of the switching DC voltage converter 12 to be tested. dc2 and DC voltage U dc2 The sensor is connected via an interface to measure the temperature.

[0052] The converter unit 2 also converts the DC voltage V1 provided by the battery into a DC voltage V2 for operating the switching DC voltage converter 12 to be tested. dc The converter unit 2 comprises two electronic half-bridges 3, 3' which are switched by an electronic control unit 4 with control signals offset in time in a modulated manner. In this embodiment, the control unit 4 and the measurement unit 1 are configured as separate units. The control unit 4 calculates trigger times for controlling the electronic half-bridges 3, 3' of the converter unit 2 and provides these to the converter unit 2. Current sensors 6, 6' are arranged to measure the bridge currents in the output or input lines of the half-bridges 3, 3' of the converter unit 2.

[0053] The measuring unit 1 is connected to the control unit 4 for time synchronization and is configured to define measuring instants 8, 8' of the current sensors 6, 6' that are time-synchronized with the control signals of the half-bridges 3, 3', so that the measuring unit 1 can detect the current values ​​exactly when the PWM control signals activate the respective half-bridges.

[0054] The DC voltage converter 12 to be tested is in particular a DC voltage converter which is downstream of a fuel cell of a vehicle or a DC voltage converter of a DC voltage charging infrastructure. [Explanation of symbols]

[0055] 1 measuring unit 2,2' conversion unit 3,3',3a,3a',3b,3b' Half Bridge 4. Control Unit 5,5' DC current sensor 6,6',6a,6a',6b,6b' Current sensor 7 Electrical Machinery 8,8' Measurement time 9,9',9a,9a',9b,9b' Interleaving throttle 10,10' DC voltage sensor 11 Inverter Assembly 12 DC voltage converter

Claims

1. 1. A measuring assembly for determining the electrical output of a switched electrical converter unit, in which at least two electronic half-bridges are switched by a control unit by control signals offset in time in a modulated manner, the measuring assembly comprising a measuring unit connected to a current sensor, a. the current sensor is configured to measure a bridge current in an output line or an input line of the half bridge of the converter unit; b) the measurement unit is connected to the control unit for time synchronization; c) the measurement unit is configured to define measurement instants of the current sensor synchronized in time with the control signals of the half-bridge; A measurement assembly, wherein the measurement unit is configured to query the current sensor at a measurement frequency that corresponds approximately to the frequency of the control signal and to predefine a measurement instant that is located in time substantially in the center of a turn-on time t on of the control signal.

2. The measurement unit queries the current sensor at a measurement frequency that is higher than the frequency of the control signal and is timed substantially at the turn-on time t ｏｎ 10. The measurement assembly of claim 1, configured for ex post selection of a measurement point in time that is centrally located.

3. The measurement unit measures the turn-on time t ｏｎ 3. A measurement assembly according to claim 1 or 2, configured to query the current sensor at multiple measurement times during a measurement and average the resulting measurements.

4. The measuring unit a) connected to at least one DC voltage sensor located on the DC voltage side of the converter unit; and 4. A measurement assembly according to claim 1, configured to calculate the switched electrical output of the converter unit or of an individual phase of the converter unit from a measured bridge current and a measured DC voltage.

5. 5. The measurement assembly of claim 4, wherein the measurement unit is configured to take into account electrical internal resistances of semiconductor switches and of other electronic components of the half-bridge when calculating the electrical output of the conversion unit.

6. The measuring unit a) connected to at least one DC current sensor located on the DC voltage side of the converter unit; and b) configured to calculate the electrical output on the DC voltage side of the conversion unit; 3. A measurement assembly according to claim 1, configured to calculate the electrical efficiency of the conversion unit.

7. 7. A converter assembly comprising a measuring assembly according to any one of claims 1 to 6 and a conversion unit in which at least two electronic half-bridges are switched by a control unit with control signals offset in time in a modulated manner, said conversion unit being adapted to convert a DC voltage V ｄｃ AC voltage V ａｃ a converter assembly, which is a switched inverter assembly for converting

8. 7. A converter assembly comprising a measuring assembly according to any one of claims 1 to 6 and a conversion unit in which at least two electronic half-bridges are switched by a control unit with control signals offset in time in a modulated manner, said conversion unit being adapted to convert an AC voltage V ａｃ DC voltage V ｄｃ a converter assembly for converting a current from a current to a voltage;

9. 7. A converter assembly comprising a measuring assembly according to any one of claims 1 to 6 and a conversion unit in which at least two electronic half-bridges are switched by a control unit with control signals offset in time in a modulated manner, said conversion unit being adapted to convert a first DC voltage V １ to the second DC voltage V ２ a converter assembly, the converter assembly being a switched DC voltage converter for converting

10. 10. A transducer assembly according to any one of claims 7 to 9, wherein the conversion unit is connected to an electric machine and the measurement unit is connected to the electric machine.

11. The transducer assembly of claim 10 , wherein the measurement unit is configured to receive mechanical measurements and to calculate a mechanical output of the electric machine.

12. 12. The transducer assembly of claim 10 or 11, wherein the measurement unit is configured to receive thermal measurements.

13. 13. A transducer assembly according to any one of claims 10 to 12, wherein the measurement unit is configured to determine parameters of components of an electrical and / or mechanical equivalent circuit of the electric machine from electrical or mechanical measurements.

14. 14. A transducer assembly according to any one of claims 10 to 13, wherein the measurement unit is configured to determine the efficiency of the electric machine from a switched electrical output of the conversion unit and from a mechanical output of the electric machine.

15. A converter assembly as described in claim 14, wherein the measurement unit is configured to determine the mechanical output of the electric machine from a measurement of the waste heat of the electric machine.

16. 16. A transducer assembly according to any one of claims 7 to 15, wherein the control unit and the measurement unit are integrated into a common unit.

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