Voltage Converter Test Method and Device

Abstract

The present invention relates to a device (50) for testing a voltage converter (10, 20) having a frequency response analyzer (60) and an impedance converter (70). The frequency response analyzer (60) is configured to measure an electrical transfer function over a predetermined frequency range. The frequency response analyzer (60) has a test signal output unit (61) for outputting a test signal for the voltage converter (10, 20), a reference signal input unit (64) for receiving a reference signal applied to the voltage converter (10, 20) for testing the voltage converter (10, 20), and a response signal input unit (67) having a predetermined input impedance (68) for receiving a response signal from the voltage converter (10, 20). The impedance converter (70) includes an impedance converter input section (71) having a variable input impedance (72) that can be adjusted to the impedance of the voltage converter (10, 20), and an impedance converter output section (75) coupled to the response signal input section (67) and having an output impedance (74) that matches the input impedance (68) of the response signal input section (67).

Description

Technology Field

[0001] The present invention relates to a device for testing a voltage converter, for example, an inductive voltage converter or a low power voltage transformer (LPVT), and a corresponding method for testing the voltage converter. Background Technology

[0002] As the topologies of distribution and transmission networks shift toward the decentralization of power generation, the number of electronic components is increasing significantly. So-called "green" energy (wind farms, solar parks, and other alternative energy sources) is growing rapidly. Electrical energy generated in this manner is frequently supplied to distribution and transmission networks using semiconductor technologies. Since the energy from these sources frequently varies with environmental changes, arbitrary changes in the time of day or weather directly affect the various switching operations required to control transmission network stability. Furthermore, an increase in the number of loads based on electronic control technologies, such as power electronic devices or variable frequency drives, impacts the transmission network. These effects can lead to an increase in transient voltage pulses, harmonics, sub-harmonics, or offset voltages at voltages ranging from DC up to several kHz. These phenomena can only be detected or monitored through high-voltage measurements with corresponding high accuracy, particularly in the DC range up to frequencies of up to several kHz.

[0003] To this end, voltage converters can be used as measuring converters for measuring alternating current voltages in the field of electrical energy engineering. The function of a voltage converter is to proportionally transfer a high voltage to be measured into low voltage values. For example, these low voltages, with values ​​around 100V, are transmitted to voltmeters, energy meters, and similar devices for measurement or protection purposes. Voltage converters can be implemented as inductive (so-called conventional) voltage converters or low-power voltage converters (so-called LPVT, low-power voltage transformers or LPIT, low-power instrument transformers).

[0004] LPVTs can take various forms. In addition to resistive and capacitive voltage dividers (undamped and damped), resistive-capacitive voltage dividers can be found in a wide range of variations in this field. Resistive-capacitive voltage converters consist of two voltage dividers connected in parallel, one being a capacitive voltage divider and the other a resistive voltage divider. Both capacitive and resistive voltage dividers generally consist of at least two elements connected in series. The parallel connection of these two voltage dividers is also known as an RC divider. One end of the RC divider is connected to the high voltage to be measured, and the other end is connected to ground. A lower voltage, proportional to the high voltage to be measured and capable of supplying a voltmeter, is applied to the tap between the RC dividers. Faults in resistive-capacitive voltage converters can be caused by faults in the resistive-capacitive voltage dividers. There are various reasons for the capacitors in the capacitive voltage dividers, such as moisture entering the insulator.

[0005] Induction voltage converters are, in principle, structured like transformers. They consist of a primary coil electrically connected to the high voltage to be measured and a secondary coil that is electrically insulated but, for safety reasons, is typically connected with one end grounded to the connected devices. Defects in induction voltage converters can occur, for example, due to defects in the coil insulation, displacement of the coil windings, or defects in the iron core that magnetically couples the primary and secondary coils.

[0006] Globally, while conventional voltage converter technologies are mainly used, the number of LPVTs is increasing significantly because they are more suitable for measuring transmission network quality.

[0007] Voltage converters (both conventional voltage converters and LPVTs) exhibit significant frequency-dependent transmission behavior by design. Information regarding this frequency-dependent transmission behavior is required in applications intended to document the aforementioned phenomena and, accordingly, monitor transmission network quality. Appropriate measurement and evaluation methods are defined regarding the determination and evaluation of transmission characteristics, and the suitability of LPVTs and conventional voltage converters for measuring transmission network quality. Since these measurement methods require a wide range of electrical equipment, they are practically performed at the manufacturer's facility or in the field, incurring correspondingly higher costs. In principle, a reference design capable of measuring frequencies up to 9 kHz is selected. To determine the frequency behavior of conventional voltage converters, a so-called dual-frequency method is used to achieve core pre-linearization via a 50 Hz fundamental frequency. High-frequency components are modulated to this fundamental frequency.

[0008] In particular, there is a need for enhanced possibilities to test both conventional voltage converters and LPVTs using methods and devices that can be easily applied in the field.

[0009] According to the present invention, a device for testing a voltage converter as defined in the independent claims and a method for testing a voltage converter are provided. The dependent claims define embodiments of the present invention.

[0010] A device according to the present invention for testing a voltage converter includes a frequency response analyzer and an impedance converter. The frequency response analyzer is configured to measure an electrical transfer function over a predetermined frequency range. The frequency response analyzer has a test signal output section, a reference signal input section, and a response signal input section.

[0011] In the test signal output section, the frequency response analyzer may output a test signal for the voltage converter to be tested. The test signal may include, for example, a voltage signal having a predetermined voltage and a variable frequency. The frequency may be varied in the range of 1 Hz to 30 MHz, particularly in the range of 20 Hz to 2 MHz. The voltage may be in the range of several volts, for example, in the range of 5 V to 300 V. The voltage may be, for example, 10 V. The voltage may be, for example, 10 V PP It may include an alternating voltage having a voltage. The test signal output section may include a terminal for a coaxial line, thereby outputting the test signal over the inner conductor of the coaxial line and coupling the outer conductor of the coaxial cable to ground. On the voltage converter to be tested, the inner conductor is connected to the terminal of the voltage converter, for example, the primary side of the voltage converter, and the outer conductor is coupled to the ground of the voltage converter. As a result, interference signals from the environment can be reduced or prevented from being transmitted to the test signal.

[0012] The frequency response analyzer can receive a reference signal through a reference signal input. For example, the reference signal input can be coupled to the same terminal of a voltage converter to which the test signal is supplied. The reference signal input may include a terminal for a coaxial cable, where the reference signal is received through the inner conductor of the coaxial cable and the outer conductor is coupled to ground. In the voltage converter, the inner conductor is coupled to the same terminal to which the test signal is supplied, and the outer conductor is coupled to the ground of the voltage converter. The test signal supplied to the voltage converter can be accurately determined through the reference signal input and used as a reference signal. The transfer function of the voltage converter can be accurately determined based on this reference signal.

[0013] At the response signal input section, the frequency response analyzer can receive a response signal generated by the voltage converter to be tested in response to the test signal output section. The response signal input section has a predefined input impedance, for example, 50 ohms.

[0014] A frequency response analyzer may be a device used to inspect power transformers, for example, through sweep frequency response analysis (SFRA). Such a frequency response analyzer may be configured to be carried by an operator, for example, as a portable device contained in a portable case.

[0015] The impedance converter has an impedance converter input and an impedance converter output. The impedance converter input has an adjustable input impedance. The impedance converter output is coupled to the response signal input of a frequency response analyzer and has an output impedance that matches the input impedance of the response signal input. The impedance converter input may be coupled, for example, to an additional terminal of a voltage converter, for example, to a secondary terminal of the voltage converter. The impedance converter input may include a terminal for a coaxial cable, so that the secondary terminal of the voltage converter is coupled to the inner conductor of the coaxial cable and the outer conductor of the coaxial cable is coupled to ground in both the voltage converter and the impedance converter. Thus, the impedance converter receives an output signal from the voltage converter output by the latter in response to a test signal and transmits this output signal as a response signal to the response signal input of the frequency response analyzer, thereby matching the impedance accordingly.

[0016] In summary, this device is based on the SFRA method approach and, for example, uses an SFRA measurement device as a frequency response analyzer. Both conventional voltage converters and LPVT voltage converters can inherently have arbitrary impedances that generally do not correspond to the input impedance of the response signal input section of the SFRA measurement device. For example, the response signal input section of an SFRA measurement device, i.e., a frequency response analyzer, may have a predefined input impedance of 50 ohms, whereas conventional voltage converters may have impedances in the range of up to several hundred ohms, and LPVTs may even have impedances of up to several megaohms. The output impedance of the test signal output section of the frequency response analyzer may be 50 ohms, and the input impedance of the reference signal input section of the frequency response analyzer may be 50 ohms. However, the response signal input section is an important path when determining the frequency-dependent transmission characteristics of conventional voltage converters and LPVTs. This means that the frequency-dependent transmission characteristics of the voltage converter are inaccurately determined due to the deviation between the input impedance of the SFRA measurement device and the secondary impedance of the voltage converter. To prevent this, an impedance converter is connected between the voltage converter and the response signal input. The output impedance of the impedance converter output matches the input impedance of the response signal input. The input impedance of the impedance converter input can be adjusted to the output impedance of the voltage converter. The input impedance of the impedance converter input can be adjusted, for example, in the range of 30 ohms to 100 megaohms, preferably in the range of 50 ohms to 100 megaohms. Since the output impedance of the impedance converter matches the input impedance of the response signal input, there is impedance matching on both sides of the impedance converter. Therefore, the frequency-dependent transmission operation of the voltage converter can be measured under optimal conditions (e.g., the nominal load of the voltage converter).

[0017] According to one embodiment, a device comprising a frequency response analyzer and an impedance converter may be configured as a mobile portable device. In this context, mobile and portable means that the device can be carried by one person and can be placed, for example, in a portable case or pocket. The device may have a weight of, for example, several kilograms, for example, 1 kg to 10 kg.

[0018] According to one embodiment, the device includes at least one battery configured to provide power for the purpose of operating a frequency response analyzer and / or an impedance converter. For example, a rechargeable battery may be provided for the frequency response analyzer, and another rechargeable battery may be provided for the impedance converter. A general (rechargeable) battery for supplying the frequency response analyzer and the impedance converter may also be provided. For example, the battery may be housed together with the frequency response analyzer and the impedance converter in the aforementioned portable case or bag, so that the entire device, including the battery and any corresponding terminal wires, is portable and carryable. Consequently, this device can be used quickly and easily to test voltage converters at various locations extending across most or the entire power supply network.

[0019] In another embodiment, the impedance converter has an amplifier having adjustable amplification. Consequently, response signals from the voltage converter to be tested can be adjusted and matched to the measurement range of the frequency response analyzer. Additionally, it is possible to test multiple different voltage converters that can have a wide range of different conversion ratios between the primary and secondary sides.

[0020] The present invention also relates to a method for testing a voltage converter. In this method, a frequency response analyzer configured to measure an electrical transfer function over a predetermined frequency range is provided. The frequency response analyzer includes a test signal output section for outputting a test signal for the voltage converter, a reference signal input section for receiving a reference signal applied to the voltage converter for testing the voltage converter, and a response signal input section having a predetermined input impedance for receiving a response signal from the voltage converter. Additionally, an impedance converter is provided having an impedance converter input section having a variablely adjustable input impedance and an impedance converter output section. The impedance converter output section has an output impedance that matches the input impedance of the response signal input section of the frequency response analyzer. That is, the impedance converter output section of the impedance converter has substantially the same impedance as the response signal input section of the frequency response analyzer, i.e., there is impedance matching. The impedance converter output section of the impedance converter is coupled to the response signal input section of the frequency response analyzer. Finally, the input impedance of the impedance converter input is adjusted to the impedance of the voltage converter to be tested, which implies that there is impedance matching between the voltage converter to be tested and the impedance converter input. Through impedance matching not only between the voltage converter to be tested and the impedance converter input, but also between the impedance converter output and the response signal input, the transfer function of the voltage converter can be accurately identified.

[0021] According to one embodiment, this method may consider calibrating a frequency response analyzer, an impedance converter, and the measurement lines used. For example, this method includes the step of connecting the test signal output to the reference signal input and the impedance converter input through measurement lines connected to the test signal output, the reference signal input, and the impedance converter input, respectively. For example, the first end of the first measurement line may be connected to the test signal output, the first end of the second measurement line may be connected to the reference signal input, and the first end of the third measurement line may be connected to the impedance converter input. The second ends of the three measurement lines are connected to each other. If the measurement lines are coaxial lines, the inner conductors of the second ends of the three measurement lines are connected to each other, and the outer conductors of the second ends of the three measurement lines are connected to each other. The impedance converter output of the impedance converter is connected to the response signal input of the frequency response analyzer as described above.

[0022] Multiple test signals of different frequencies are output through the test signal output section. Corresponding multiple calibration values ​​are obtained from the reference signal input section and the response signal input section. The test signal output through the test signal output section is obtained at the response signal input section through an impedance converter, that is, through a third measurement line connected to the impedance converter input section and through the coupling between the impedance converter output section and the response signal input section. Each calibration value of the multiple calibration values ​​is assigned to the corresponding test signal of the multiple test signals, or rather, is assigned to the corresponding frequency of the corresponding test signal.

[0023] Each of the multiple calibration values ​​may include, for example, the amplitude of the voltage signal of the reference signal input section, the amplitude of the voltage signal of the response signal input section, the ratio between the amplitude of the voltage signal of the reference signal input section and the amplitude of the voltage signal of the response signal input section, and / or the phase difference between the voltage signal of the reference signal input section and the voltage signal of the response signal input section.

[0024] Based on calibration values, for example, by adjusting the amplifier amplification of the impedance converter, it is possible to account for voltage drops in the measurement lines in subsequent measurements, for example, for the voltage converter. Phase differences caused by the measurement lines can likewise be accounted for in subsequent measurements of the voltage converter.

[0025] After calibration, the connections between the second ends of the measurement lines are disconnected again.

[0026] For example, to test a voltage converter, the transfer function of the voltage converter may be determined at different frequencies. The transfer function may include, for example, the voltage ratio between the input voltage and the output voltage of the voltage converter over a predetermined frequency range. Alternatively or additionally, the transfer function may include, for example, the phase shift between the input voltage and the output voltage of the voltage converter over a predetermined frequency range.

[0027] According to one embodiment, a test signal output section and a reference signal input section may be connected to a first terminal of a voltage converter, for example, through corresponding measurement lines. The first terminal of the voltage converter may be, for example, a terminal on the input side of the voltage converter, for example, on the primary side. Additionally, an impedance converter input section may be connected to a second terminal of the voltage converter through measurement lines. The second terminal of the voltage converter may be, for example, an output side terminal, for example, a secondary side terminal of the voltage converter. Various test signals are output through test signal output sections of different frequencies and supplied to the voltage converter. For example, the signal may be output as a specific voltage whose frequency changes over time. For example, an alternating voltage of constant amplitude may be output, and its frequency continuously passes through a predetermined range, for example, a range from several Hertz to several Megahertz, for example, a range from 20 Hz to 2 MHz. These signals are also known as sweeps or chirps.

[0028] While test signals are output through the test signal output section, multiple measurement values ​​are obtained from the reference signal input section and the response signal input section. To obtain measurement values ​​from the response signal input section, it is evident that signals are received from a voltage converter through an impedance converter input section, an impedance converter including an amplifier, an impedance converter output section, and a coupling between the impedance converter output section and the response signal input section. Each measurement value of the multiple measurement values ​​is assigned to a corresponding test signal of the multiple test signals. Each measurement value of the multiple measurement values ​​may include, for example, the amplitude of the voltage signal of the reference signal input section, the amplitude of the voltage signal of the response signal input section, the ratio between the amplitude of the voltage signal of the reference signal input section and the amplitude of the voltage signal of the response signal input section, and the phase difference between the voltage signal of the reference signal input section and the voltage signal of the response signal input section.

[0029] The measurement lines used and the terminals to which the measurement lines are coupled to the voltage converter and the device generally have frequency-dependent impedances. To determine the transfer function of the voltage converter as accurately as possible, it is desirable to consider the effects of these (frequency-dependent) impedances and exclude them from the calculation. Accurate information regarding the corresponding impedances may sometimes be unavailable or variable, for example, due to different shapes of the terminals or different cable routings of the measurement lines. As described above, if calibration values ​​are identified, these calibration values ​​are used to correct the acquired measurement values, making it possible to consider the effect of the (frequency-dependent) impedances of the measurement lines on the measurement values. According to one embodiment, one of a plurality of measurement values ​​is corrected using a corresponding calibration value, and the measurement value and the corresponding calibration value are assigned to each test signal having the same frequency. For example, at each frequency, the corresponding calibration value assigned to that frequency can be subtracted from the measurement value assigned to that frequency.

[0030] Where the correction of the measured values ​​is performed by calibration values, the measured values ​​of the following embodiments are preferably related to the measured values ​​corrected by the calibration values.

[0031] According to one embodiment, the voltage ratio error between the expected voltage signal and the measured voltage signal is determined at different frequencies based on a plurality of measured values. For example, the expected voltage signal can be determined based on the voltage signal of the reference signal input and the conversion ratio of the voltage converter. For example, considering the conversion ratio of the voltage converter, the respective voltage ratio error for various frequencies can be determined based on the amplitude of the voltage signal of the response signal input and the amplitude of the voltage signal of the reference signal input. Additionally, the phase shift at different frequencies can be determined based on the measured values. For example, the phase shift between the voltage signal of the response signal input and the voltage signal of the reference signal input can be determined for different frequencies.

[0032] Voltage ratio errors or phase shifts at different frequencies can be displayed, for example, on a display device coupled to a frequency response analyzer. The display device may be, for example, a display device on a laptop, tablet PC, or smartphone coupled to the frequency response analyzer.

[0033] In addition, characteristic values ​​of the voltage converter can be determined based on multiple identified measurements. The characteristic values ​​of the voltage converter include, for example, a frequency at which the voltage ratio error is 2%, a frequency at which the voltage ratio error is 5%, a frequency at which the voltage ratio error is 10%, a resonant frequency, and / or a voltage ratio error at a frequency of 50 Hz.

[0034] The characteristic values ​​of the voltage converter can likewise be displayed on a display device coupled to the frequency response analyzer and can be stored for long-term monitoring, for example, on a laptop, tablet PC, or smartphone.

[0035] The state of the voltage converter can be determined by using voltage ratio errors, phase shifts, and characteristic values, for example, by comparing them with corresponding target values ​​or values ​​at the start of operation, or by observing changes in these values ​​over a relatively long period. This makes it possible to verify whether the voltage converter is in the correct state.

[0036] The method described above can be performed, for example, by the device described above. Brief explanation of the drawing

[0037] The present invention will be described in more detail below using preferred embodiments with reference to the drawings. In the drawings, like reference numerals indicate like elements. FIG. 1 schematically illustrates a device for testing a voltage converter according to one embodiment of the present invention in relation to an existing voltage converter to be tested. FIG. 2 schematically illustrates a device for testing the voltage converter of FIG. 1 connected to an LPVT (e.g., a resistive-capacitive voltage divider) to be tested. FIG. 3 illustrates method steps for testing a voltage converter according to one embodiment. Specific details for implementing the invention

[0038] The present invention will be described in more detail below using preferred embodiments with reference to the drawings. In the drawings, like reference numerals indicate like or similar elements. The drawings are schematic diagrams of various embodiments of the present invention. The elements depicted in the drawings are not necessarily depicted in actual size. Rather, the various elements depicted in the drawings are reproduced so that a person skilled in the art can understand their function and purpose.

[0039] The connections and combinations between the functional units and elements illustrated in the drawings may be implemented as direct or indirect connections or combinations. The connections or combinations may be implemented via wired or wireless methods.

[0040] Methods and devices for testing voltage converters are described in detail below. The condition of conventional voltage converters (i.e., inductive voltage converters) can be compromised by defects in the coils (e.g., insulation errors or coil displacements). The condition of LPVTs can be compromised by defects in the capacitors or ohmic components of RC voltage dividers. These defects can be caused by various factors, such as moisture entering the insulators. Inspecting voltage converters can help prevent the transmission grid from being miscontrolled due to inaccurate voltage converter measurements or prevent the complete failure of the voltage converter. A complete failure can endanger other device components or personnel.

[0041] FIG. 1 schematically illustrates a conventional inductive voltage converter (10). The voltage converter (10) includes a transformer (11) disposed within a housing (12). The transformer (11) includes a primary coil (13) and a secondary coil (14). The primary coil (13) and the secondary coil (14) are the conversion ratio of the transformer (11). Determines. One end of the primary coil (13) is connected to terminal (15), and the other end of the primary coil (13) is connected to terminal (19) connected to ground. The secondary coil (14) is connected to two terminals (17 and 18). Reference number (16) indicates the ground connection of the housing (12). The output impedance of the voltage converter (10) that can be measured at terminals (17 and 18) is substantially determined, for example, by the secondary coil (14) and may be in the range of several ohms to several hundred ohms or several kilohms.

[0042] FIG. 1 further illustrates a device (50) for testing a voltage converter (10). The device (50) includes a frequency response analyzer (60) and an impedance converter (70). Although the frequency response analyzer (60) and the impedance converter (70) are shown as two separate units in FIG. 1, they may be configured as a single unit or at least integrated into a common housing.

[0043] The frequency response analyzer (60) includes a signal-generating device (63) having an output impedance (62) configured to output a test signal having a variable frequency and a predetermined voltage at a test signal output section (61). For example, the test signal may be a low-voltage signal, for example, with a voltage of 10V. The signal-generating device (63) may output a sinusoidal voltage, for example, at a continuously increasing frequency, for example, in a frequency range of 10Hz to 10MHz, or for example, in a range of 20Hz to 2MHz.

[0044] The frequency response analyzer (60) further includes a reference signal acquisition device (66) having an input impedance (65) coupled to a reference signal input section (64).

[0045] Furthermore, the frequency response analyzer (60) includes a measurement signal acquisition device (69) having an input impedance (68) coupled to a response signal input section (67).

[0046] The frequency response analyzer (60) may be a device that can be used for Sweep Frequency Response Analysis (SFRA) measurements of power transformers. For example, the output impedance (62) and the input impedances (65, 68) may each be 50 ohms.

[0047] While the frequency response analyzer (60) outputs a sinusoidal test voltage with the frequency continuously increasing, for example, at the test signal output section (61), the frequency response analyzer (60) can receive a reference signal at the reference signal input section (64) and receive a response signal at the response signal input section (64), and can associate the response signal with the reference signal.

[0048] The frequency response analyzer (60) can be powered, for example, from a battery (90) to operate the frequency response analyzer (60).

[0049] The device (50) further includes an impedance converter (70). The impedance converter (70) has an impedance converter input (71) having an adjustable input impedance (72). The input impedance (72) can be adjusted, for example, in a range of several ohms to several megaohms. For example, the input impedance can be adjusted in a range of 1 ohm to 10 megaohms. The impedance converter (70) further includes an amplifier (73), for example, an operational amplifier, having adjustable amplification. The amplification can be adjusted in a range of 1 to several thousand seconds, for example, up to 2,000 or 10,000. The output of the amplifier (73) is connected to an impedance converter output (75) through an output impedance (74). The output impedance (74) may be equal to, for example, the input impedance (68) of the frequency response analyzer (60), for example, 50 ohms. The impedance converter (70) may be powered, for example, from a battery (91) to operate the impedance converter (70). The batteries (90, 91) may be provided as separate batteries or as a common battery. The batteries (90, 91) may be rechargeable batteries. Alternatively or additionally, the frequency response analyzer (60) and the impedance converter (70) may be powered by electrical energy through a power supply unit.

[0050] To test the voltage converter (10), the primary side of the transformer (11) is coupled to a test signal output section (61) and a reference signal input section (64). Corresponding lines (81, 82), also generally referred to as measurement lines, may be composed, for example, of coaxial lines. The outer conductors of the coaxial lines (81, 82) are each connected to the ground of the frequency response analyzer (60), for example, through the housing of the frequency response analyzer (60). In the voltage converter (10), the outer conductors of the coaxial lines (81, 82) are each connected to the housing ground (16). The inner conductor of the coaxial lines (81) is connected to the test signal output section (61) in the frequency response analyzer (60) and to a terminal (15) coupled to the primary coil (13) of the transformer (11) in the voltage converter (10). The inner conductors of the coaxial lines (82) are connected to the reference signal input (64) in the frequency response analyzer (60) and to the terminal (15) in the voltage converter (10). Through the reference signal input (64), the reference signal recording device (66) obtains a test signal from the signal generating device (63), taking into account any interruptions or losses when supplied to the voltage converter (10), that is, through transmission via the coaxial line (81). It is evident that the lines (81, 82) can be implemented in any other way, for example in the form of twisted lines or as individual lines that transmit only the test signal or reference signal and do not establish any ground connection. In this case, the corresponding ground connection can be established through a separate connection between the device (50) and the voltage converter (10).

[0051] An additional line (83), particularly a measurement line, for example, a coaxial line, connects the secondary side of the voltage converter (10) to the impedance converter input (71). For example, in the voltage converter (10), the inner conductor of the coaxial line (83) can be connected to one side of the secondary coil (14) of the transformer (11) through terminal (17), and the outer conductor of the coaxial line (83) can be connected to the other side of the secondary coil (14) through terminal (18). Additionally, terminal (18) can be connected to ground. In the impedance converter (70), the inner conductor of the coaxial line (83) can be connected to the impedance converter input (71), and the outer conductor of the coaxial line (83) can be connected to ground, for example, through the housing of the impedance converter (70).

[0052] The impedance converter output (75) is connected to the response signal input (67) via line (84), particularly an additional measurement line, for example, a coaxial line. For example, in the impedance converter (70), the inner conductor of the coaxial line (84) can be connected to the impedance converter output (75), and the outer conductor of the coaxial line (84) can be connected to ground, for example, through the housing of the impedance converter (70). In the frequency response analyzer (60), the inner conductor of the coaxial line (84) can be connected to the response signal input (67), and the outer conductor of the coaxial line (84) can be connected to ground, for example, through the housing of the frequency response analyzer (60).

[0053] The lines (83, 84) may be implemented in any other way, for example as twisted lines or individual lines, which each transmit only a response signal from the voltage converter (10) to the impedance converter (70) and only an impedance-matching response signal from the impedance converter (70) to the frequency response analyzer (60), but do not create a ground connection. A proper ground connection may be created through a separate connection between the voltage converter (10), the impedance converter (70), and the frequency response analyzer (60).

[0054] FIG. 2 schematically illustrates a voltage converter (20) of the resistive-capacitive LPVT type. The voltage converter (20) comprises a series connection of two capacitors (21 and 22) that function as a capacitive voltage divider. The series connection is connected to terminals (15 and 19). A resistive resistor divider (23 and 24) is connected here in parallel. Thus, the output impedance of the voltage converter (20), which can be measured at terminals (17 and 18), is substantially determined by the capacitor (22) and the resistor (24). In contrast to the output impedance of the voltage converter (10) illustrated in FIG. 1, which may be in the range of several ohms to several kilohms, the output impedance of the voltage converter (20) may be in the range of several hundred kilohms to several megaohms. The conversion ratio of the resistive-capacitive voltage converter (20) is determined by the capacitances (C1 and C2) of the capacitors (21 and 22) and the resistance values ​​(R1 and R2) of the resistors (23 and 24). Complex voltage between terminals (15 and 16) There is a complex voltage between the terminals (17 and 18). complex transfer function with It is as follows:

[0055]

[0056] The resistive-capacitive voltage converter (20) shown in FIG. 2 is connected to the device (50) using measurement lines (81 to 83) in the same way as the inductive voltage converter (10) shown in FIG. 1.

[0057] A method (300) for testing a voltage converter using the device (50) illustrated in FIGS. 1 and 2 will be described in detail below with reference to FIG. 3.

[0058] In step (301), the frequency response analyzer (60) and the impedance converter (70) are provided near the voltage converter to be tested. The voltage converter may include, for example, the inductive voltage converter (10) shown in FIG. 1 or the resistive-capacitive voltage converter (20) shown in FIG. 2. In step (302), the impedance converter output (75) of the impedance converter (70) is coupled to the response signal input (67) of the frequency response analyzer (60) via line (84). As described above, the output impedance (74) of the impedance converter (70) at the impedance converter output (75) substantially corresponds to the input impedance (68) of the frequency response analyzer (60) at the response signal input (67).

[0059] Depending on the voltage converter (10, 20) to be tested, the input impedance (72) of the impedance converter (70) is adjusted in step (303). The output impedance of the voltage converter (10, 20) can be obtained by measurement, or can be adopted or determined from the rated plate of the voltage converter, for example, from a load specified on the rated plate of the voltage converter.

[0060] Optionally, calibration of the device (50) can be performed in steps (304 to 306) with respect to the measurement lines (81 to 83). To this end, a calibration configuration can be set up in step (304). Line (81) is connected to the test signal output section (61), line (82) is connected to the reference signal input section (64), and line (83) is connected to the impedance converter input section (71). The three free ends of the lines (81, 82 and 83) are directly connected to each other. If the lines (81, 82 and 83) are coaxial lines, the inner conductors of the lines (81, 82 and 83) are directly connected to each other, and separately, the outer conductors of the lines (81, 82 and 83) are directly connected to each other. In step (305), test signals are generated by a signal-generating device (63) and output through a test signal output unit (61). The test signals may include, for example, so-called chirp signals, i.e., signals whose frequency changes over time. The test signals may include so-called sweep signals, i.e., alternating voltages of constant amplitude, the frequency of which periodically and continuously passes through a predetermined range. For example, the test signals may include voltage signals having an amplitude of several volts, for example, 10V.

[0061] While test signals are output in step (305), in step (306), corresponding calibration values, e.g., voltage signals, are obtained at the reference signal input (64) and at the test signal input (67) (via the impedance converter (50)). The transmission characteristics of line (82), line (83), the impedance converter (70), and line (84) can be identified by analyzing the calibration values ​​and subsequently used to correct the measured values ​​when tested with the voltage converter (10, 20). The calibration values ​​may include, for example, the voltage signal of the reference signal input, and other calibration values ​​may include, for example, the voltage signal of the response signal input. Additional calibration values ​​may be determined from the obtained calibration values. For example, the amplitude ratio between the amplitude of the voltage signal of the reference signal input and the amplitude of the voltage signal of the response signal input may be determined as an additional calibration value. For example, the phase difference between the voltage signal of the reference signal input and the voltage signal of the response signal input may be determined as an additional calibration value. The calibration values ​​obtained and additionally determined may be obtained at different frequencies or determined for different frequencies and assigned to different frequencies. For example, corresponding amplitude ratios and phase differences may be assigned to some or all of the multiple different frequencies at which the test signal is output.

[0062] When the correction is finished, the ends of the directly connected lines (81, 82 and 83) are separated from each other.

[0063] Next, the amplification of the amplifier (73) of the impedance converter (70) is adjusted in step (307). When adjusting the amplification, results from previous calibrations may be taken into account, for example. For example, the amplitude ratio at a specific frequency or the average value of the amplitude ratios over a specific frequency range may be identified to adjust the amplification of the amplifier (73) in such a way that the amplitude ratios become substantially the same. Additionally, when adjusting the amplification of the amplifier (73), the input sensitivity of the response signal input section as well as the conversion ratio of the voltage converter are taken into account so that the voltage range expected at the output of the voltage converter (10) due to the test signal is within the measurement range of the measurement signal acquisition device (69) and this range is utilized to the fullest extent.

[0064] In step (308), the test configuration is set up in relation to the voltage converter (10 or 20). As illustrated in FIGS. 1 and 2, the test signal output (61) is connected to the terminal (15) of the voltage converter (10 or 20) via line (81). If line (81) also performs a ground connection, it is connected to the ground (16) of the housing (12) of the voltage converter (10, 20). The reference signal input (64) is also connected to the terminal (15) of the voltage converter (10, 20) via line (82), and if line (82) performs a ground connection, it is connected to the terminal (16) (ground) of the housing (12) of the voltage converter (10, 20). The impedance converter (71) is connected to the terminal (17) of the voltage converter (10, 20) via line (83), and if line (83) performs a ground connection, it is connected to the terminal (18) of the housing (12) of the voltage converter (10, 20). It should be noted that line (84) still connects the impedance converter output (75) to the response signal input (67) of the frequency response analyzer (60).

[0065] In step (309), test signals are generated by a signal-generating device (63) and output through a test signal output unit (61), and line (81) is supplied to the primary side of a voltage converter (10, 20). The test signals may include, for example, so-called chirp signals, i.e., signals whose frequency changes over time. The test signals may include, for example, so-called sweep signals, i.e., alternating voltages of constant amplitude, the frequency of which passes through a predetermined range periodically and continuously. The test signals may include, for example, voltage signals having an amplitude of several volts, e.g. 10V. Other test signals, such as signals having a constant frequency and variable amplitude, pulse signals, etc., are also possible.

[0066] While test signals are output in step (309), in step (310), corresponding measurement values, e.g., voltage signals, are acquired by the reference signal acquisition device (66) and the measurement signal acquisition device (69), respectively, at the reference signal input (64) and at the test signal input (67) (via the impedance converter (50). The transmission characteristics of the voltage converters (10, 20) can be identified by analyzing these measurement values ​​by, for example, a processing device (not shown) of the frequency response analyzer (60) (e.g., a memory-allocated microprocessor). If the above-described correction is performed, the acquired measurement values ​​can be corrected in step (311) with the help of the correction values. Consequently, it is possible to correct the influence of line (82), line (83), impedance converter (70), and line (84) on the acquired measurement values ​​in particular.

[0067] The measured values ​​may include, for example, the voltage signal of the reference signal input and the voltage signal of the response signal input. Additional values ​​may be determined through the acquired measured values. For example, the amplitude ratio between the amplitude of the voltage signal of the reference signal input and the amplitude of the voltage signal of the response signal input may be determined. Additionally, the phase difference between the voltage signal of the reference signal input and the voltage signal of the response signal input may be determined. The acquired measured values ​​and additionally determined values ​​may be acquired at different frequencies, or determined for different frequencies and assigned to different frequencies. For example, corresponding amplitude ratios and phase differences may be assigned to some or all of the multiple different frequencies at which the test signal is output.

[0068] The amplitude ratio and / or phase difference can be corrected through corresponding values ​​from the calibration. Correction can be performed for the relevant frequencies to which the amplitude ratio and phase difference are assigned.

[0069] Based on the measured values ​​identified in this manner and additionally determined values, the transfer function of the voltage converter can be determined. For example, the voltage ratio error of the voltage converter can be identified in step (312), and in particular, the voltage ratio errors can be determined for various frequencies at which a test signal is supplied to the voltage converter. Additionally, the phase shift of the voltage converter for various frequencies can be determined in step (312). In step (313), the voltage ratio error and / or phase shift can be displayed on a display device, for example, in the form of a diagram over the frequency. The display device may be, for example, a display device of a laptop, tablet PC, or smartphone connected to the device (50).

[0070] Additionally, in step (314), characteristic values ​​of the voltage converter (10, 20) may be calculated and displayed based on the identified measured values ​​and additionally determined values. The characteristic value of the voltage converter (10, 20) may be, for example, a frequency with a voltage ratio error of 2%. For example, it is possible to determine higher frequencies with a voltage ratio error of less than 2%, starting from a nominal frequency of 50 Hz. A frequency with a voltage ratio error of 2% or more may be displayed as a corresponding characteristic value. For example, the corresponding characteristic value may be determined in the direction of lower frequencies, starting from a nominal frequency of 50 Hz. Other characteristic values ​​of the voltage converter may be, for example, frequencies with a voltage ratio error of 5% or 10%. Other characteristic values ​​of the voltage converter may be the resonant frequency of the voltage converter (10, 20), for example, a frequency at which the largest output amplitude is achieved at a constant input amplitude or the output signal has a phase angle of 90° with respect to the input signal. The voltage ratio error at a nominal frequency, for example 50Hz, can be determined as an additional characteristic value.

[0071] In summary, the combination of the frequency response analyzer (60) and the impedance converter (70) provides the possibility to test both the conventional inductive voltage converter (10) and the LPVT voltage converters (20). Additionally, in relation to the impedance converter (70), this frequency response analyzer (60) can be configured as a small device that can be carried by a worker so that these tests can be easily performed in the field.

[0072] The described method is suitable for field measurements, so that integrity and transmission operation can be checked in the installed state (e.g., during field inspection or routine measurement), and critical frequencies (e.g., voltage ratio error of 2%, 5%, 10%) can be checked or displayed over time. Additionally, this method is also suitable for manufacturers in production processes because the device (50) used is compact and lightweight and can be simply integrated into the production process. Furthermore, the voltage levels used are low, which can reduce the risk to operators. In particular, the measurement itself is very accurate through impedance matching and, if necessary, calibration.

[0073] The impedance converter (70) not only has the characteristic of matching the impedance to the nominal load of the voltage converter (10, 20), but rather has the characteristic of amplifying the signal applied to the secondary side of the voltage converter (10, 20). In addition, this measurement design has the advantage that the connection between the impedance converter (70) and the secondary side of the voltage converter (10, 20) can be kept short to avoid reflections. On the other side of the impedance converter, impedance matching (50Ω) is achieved. Also, using this measurement design, for example, measurement design calibration, amplification / phase calibration can be easily performed.

Claims

Claim 1 A device for testing a voltage converter: - a frequency response analyzer (60) configured to measure an electrical transfer function over a predetermined frequency range, comprising: a test signal output unit (61) for outputting a test signal for the voltage converter (10, 20); a reference signal input unit (64) for receiving a reference signal applied to the voltage converter (10, 20) for the purpose of testing the voltage converter (10, 20); and a response signal input unit (67) having a predetermined input impedance (68) for receiving a response signal from the voltage converter (10, 20); - An impedance converter (70) having an impedance converter input section (71) having a variable input impedance (72) that can be adjusted to the impedance of the voltage converter (10, 20), and an impedance converter output section (75) coupled to the response signal input section (67) and having an output impedance (74) that matches the input impedance (68) of the response signal input section (67); A voltage converter test device comprising a processing unit configured to connect the test signal output unit (61) and the reference signal input unit (64) to the first terminal (15) of the voltage converter (10, 20) through measurement lines (81, 82), connect the impedance converter input unit (71) to the second terminal (17) of the voltage converter (10, 20) through measurement line (83), output a plurality of test signals at different frequencies through the test signal output unit (61), and obtain a plurality of measurement values ​​from the reference signal input unit (64) and the response signal input unit (67) through the impedance converter (70) and the impedance converter input unit (71). Claim 2 A voltage converter test device according to claim 1, wherein the input impedance (72) of the impedance converter input section (71) can be adjusted in the range of 30 ohms to 100 megaohms. Claim 3 A voltage converter test device according to claim 1, wherein the predetermined input impedance (68) of the response signal input section (67) of the frequency response analyzer (60) is 50Ω. Claim 4 A voltage converter test device according to claim 1, wherein the output impedance (62) of the test signal output section (61) of the frequency response analyzer (60) is 50 ohms, and the input impedance (65) of the reference signal input section (64) of the frequency response analyzer (60) is 50 ohms. Claim 5 A voltage converter test device according to claim 1, wherein the device (50) comprises at least one battery (90, 91) configured to provide power for the purpose of operating the frequency response analyzer (60) and / or the impedance converter (70). Claim 6 In claim 1, the device (50) is a voltage converter test device configured as a mobile portable device. Claim 7 In claim 1, the impedance converter (70) comprises an amplifier (73) having adjustable amplification, a voltage converter test device. Claim 8 delete Claim 9 As a method for testing a voltage converter, the method (300) comprises: - a step (301) of providing a frequency response analyzer (60) configured to measure an electrical transfer function over a predetermined frequency range, wherein the frequency response analyzer (60) comprises a test signal output unit (61) for outputting a test signal for the voltage converter (10, 20), a reference signal input unit (64) for receiving a reference signal applied to the voltage converter (10, 20) for testing the voltage converter (10, 20), and a response signal input unit (67) having a predetermined input impedance (68) for receiving a response signal from the voltage converter (10, 20), the providing step (301), - an impedance converter input unit (71) having a variablely adjustable input impedance (72), and an impedance having an output impedance (72) that matches the input impedance (68) of the response signal input unit (67). The method comprises the steps of: providing an impedance converter (70) having a converter output section (75) (301); coupling the impedance converter output section (75) to the response signal input section (67) (302); and adjusting the input impedance (72) of the impedance converter (70) to the impedance of the voltage converter (10, 20) (303); connecting the test signal output section (61) to the reference signal input section (64) and the impedance converter input section (71) through measurement lines (81 to 83) respectively connected to the test signal output section (61), the reference signal input section (64), and the impedance converter input section (71) (304); outputting a plurality of test signals at different frequencies through the test signal output section (61) (305); and the impedance converter (70) and the impedance converter A step (306) of obtaining a plurality of correction values ​​from the reference signal input unit (64) and the response signal input unit (67) through the input unit (71),A voltage converter test method further comprising a step (306) of obtaining a plurality of correction values, wherein each of the plurality of correction values ​​is assigned to a corresponding test signal of the plurality of test signals. Claim 10 A voltage converter test method according to claim 9, wherein each of the plurality of correction values ​​comprises: at least one of the following values: the amplitude of the voltage signal of the reference signal input unit (64), the ratio between the amplitude of the voltage signal of the reference signal input unit (64) and the amplitude of the voltage signal of the response signal input unit (67), and the phase difference between the voltage signal of the reference signal input unit (64) and the voltage signal of the response signal input unit (67). Claim 11 A voltage converter test method according to claim 9, further comprising the step (307) of adjusting the amplification of the amplifier (73) of the impedance converter (70) according to at least one of the plurality of calibration values. Claim 12 As a method for testing a voltage converter, the method (300) comprises: - a step (301) of providing a frequency response analyzer (60) configured to measure an electrical transfer function over a predetermined frequency range, wherein the frequency response analyzer (60) comprises a test signal output unit (61) for outputting a test signal for the voltage converter (10, 20), a reference signal input unit (64) for receiving a reference signal applied to the voltage converter (10, 20) for testing the voltage converter (10, 20), and a response signal input unit (67) having a predetermined input impedance (68) for receiving a response signal from the voltage converter (10, 20), the providing step (301), - an impedance converter input unit (71) having a variablely adjustable input impedance (72), and an impedance having an output impedance (72) that matches the input impedance (68) of the response signal input unit (67). The method comprises the steps of: providing an impedance converter (70) having a converter output section (75) (301); coupling the impedance converter output section (75) to the response signal input section (67) (302); and adjusting the input impedance (72) of the impedance converter (70) to the impedance of the voltage converter (10, 20) (303); connecting the test signal output section (61) and the reference signal input section (64) to the first terminal (15) of the voltage converter (10, 20) through measurement lines (81, 82) (308); connecting the impedance converter input section (71) to the second terminal (17) of the voltage converter (10, 20) through a measurement line (83) (308); and outputting a plurality of test signals at different frequencies through the test signal output section (61). Step (309), and - Step (310) of obtaining a plurality of measurement values ​​from the reference signal input unit (64) and the response signal input unit (67) through the impedance converter (70) and the impedance converter input unit (71),A voltage converter test method further comprising a step (310) of acquiring a plurality of measurement values, wherein each of the plurality of measurement values ​​is assigned to a corresponding test signal of the plurality of test signals. Claim 13 A voltage converter test method according to claim 12, wherein each of the plurality of measurement values ​​comprises: at least one of the amplitude of the voltage signal of the reference signal input unit (64), the ratio between the amplitude of the voltage signal of the reference signal input unit (64) and the amplitude of the voltage signal of the response signal input unit (67), and the phase difference between the voltage signal of the reference signal input unit (64) and the voltage signal of the response signal input unit (67). Claim 14 A voltage converter test method according to claim 12, further comprising a step (311) of correcting one of the plurality of measurement values ​​using a correction value, wherein the measurement value and the correction value are assigned to each test signal having the same frequency. Claim 15 A voltage converter test method according to claim 12, further comprising: a step (312) of determining a voltage ratio error and / or phase shift at different frequencies based on the plurality of measured values; and a step (313) of depicting the voltage ratio error and / or phase shift at different frequencies on a display device coupled to the frequency response analyzer (60). Claim 16 A voltage converter test method according to claim 12, further comprising the step (314) of determining characteristic values ​​of the voltage converter (10, 20) based on the plurality of measurement values, wherein the characteristic values ​​include at least one value from the group comprising: a frequency at which the voltage ratio error is 1%, a frequency at which the voltage ratio error is 5%, a frequency at which the voltage ratio error is 10%, a resonant frequency, and a voltage ratio error at a frequency of 50 Hz.

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