METHOD, MEASURING DEVICE AND DATA CARRIER WITH MEASUREMENT DATA FOR DETERMINING THE INDUCTANCE OF AN ELECTRICAL COMPONENT

Abstract

Determining the inductance L of an electrical component includes a high current pulse being generated and conducted through the electrical component. The electronic component is arranged in an electrical resonant circuit, in series with a reference component and with at least one capacitor. The resonant circuit is excited to oscillate by the high current pulse. Electrical properties of the electrical component are measured for a measuring duration, and the inductance L of the electrical component is determined from the measured electrical properties. A voltage drop U across the electrical component and a reference voltage drop U.sub.R across the reference component having a known reference inductance L.sub.R is measured. The inductance L of the electrical component is calculated as a product of the reference inductance L.sub.R with a proportionality factor, which is dependent on the measured voltage drop U and the measured reference voltage drop U.sub.R.

Claims

1.-14. (canceled)

15. A method for determining the inductance (L) of an electrical component (2), comprising: connecting a reference component (9) having a known reference inductance (L.sub.R) in series with the electrical component (2); generating, in an excitation step, a high current pulse and conducting the high current pulse through the electrical component (2); measuring, in a measuring step, electrical properties of the electrical component (2) for a measuring duration; and determining, in an evaluation step, the inductance (L) of the electrical component (2) from the measured electrical properties, wherein, in the measuring step, a voltage drop (U) across the electrical component (2) and a reference voltage drop (U.sub.R) across the reference component (9) are measured, and wherein, in the evaluation step, the inductance (L) of the electrical component (2) is calculated as a product of the reference inductance (L.sub.R) with a proportionality factor, which is dependent on the measured voltage drop (U) and the measured reference voltage drop (U.sub.R).

16. The method according to claim 15, wherein, during the measuring step, a current flow (I) through the electrical component (2) is also measured.

17. The method according to claim 16, wherein, in the evaluation step, the proportionality factor is calculated as a quotient of, the difference between the measured voltage drop (U) and the product of the ohmic resistance (R) of the electrical component (2) and the measured current flow (I), and the measured reference voltage drop (U.sub.R).

18. The method according to claim 17, wherein the ohmic resistance is determined as the average of the quotients of the voltage drop (U) and the current flow (I) at a plurality of amplitude maxima of the current flow (I) through the electrical component (2) during the measuring step.

19. The method according to claim 15, wherein, during the excitation step, the high current pulse is triggered by a controller (7) which is galvanically isolated from a circuit comprising the electrical component (2).

20. The method according to claim 15, wherein an energy loss is determined as a product of the voltage and current progression, integrated over a half-wave between two successive amplitude maxima (U1 and U2) of the voltage drop across the electrical component.

21. A measuring device (1) for determining the inductance of an electrical component (2), wherein the electrical component (2) is arranged in a resonant circuit (3), wherein the measuring device comprises a current source which can be connected to the resonant circuit (3) and by means of which a high current pulse in the resonant circuit (3) can be generated, wherein a voltage drop (U) across the electrical component (2) can be measured using a voltmeter (31), wherein a reference component (9) having a reference inductance (L.sub.R) is arranged in series with the electrical component (2), in the resonant circuit (3), and wherein a reference voltage drop (U.sub.R) across the reference component (9) is measured using a reference voltmeter (32).

22. The measuring device (1) according to claim 21, wherein the reference component (9) is an air coil.

23. The measuring device (1) according to claim 21, wherein a current flow through the electrical component (2) is measured by an ammeter (33).

24. The measuring device (1) according to claim 21, wherein the measuring device (1) comprises a controller (7) and a capacitor (4) that is arranged in the resonant circuit (3), wherein the capacitor (4) is charged by a charging device (5) in a first control state of the controller (7), and wherein the capacitor (4) is discharged in the resonant circuit (3) in a second control state of the controller (7), and subsequently electrical oscillations are performed in the resonant circuit (3).

25. The measuring device (1) according to claim 24, wherein the controller (7) comprises a thyristor (28) which is arranged in the resonant circuit (3) and configured to be activated by the controller (7).

26. The measuring device (1) according to claim 24, wherein the controller (7) is galvanically isolated from the resonant circuit (3).

27. An electronically readable data medium comprising a data sequence stored therein, wherein the data sequence comprises at least one measuring data packet having an item of high current pulse information and having two measurement series of a temporal progression of a voltage drop (U(t)) and of a reference voltage drop (U.sub.R(t)) for an electrical resonant circuit, excited using the high current pulse, having an electrical component and having a reference component which was excited to a damped electrical oscillation by the high current pulse.

28. The electronically readable data medium according to claim 27, wherein a measuring data packet stored thereon further comprises a measurement series of a temporal progression of a current flow through the electrical component.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Exemplary embodiments of the inventive concept will be explained in greater detail in the following, said embodiments being shown in the drawings, in which:

[0037] FIG. 1 is a schematic illustration of a measuring device according to the invention which is suitable for carrying out the measurement method according to the invention,

[0038] FIG. 2 shows a measuring device in greater detail,

[0039] FIG. 3 is a schematic view of the temporal progression of the measured voltage drop U across the electrical component, of the measured reference voltage drop U.sub.R across the reference component, and of the measured current flow I during a damped oscillation which was excited by means of a high current pulse in an electrical resonant circuit, and

[0040] FIG. 4 is a schematic illustration of the inductance, determined for various amplitude maxima of the current flow, as a function of the current flow.

DETAILED DESCRIPTION

[0041] A measuring device 1, shown schematically in FIG. 1, for determining the inductance L of an electrical component 2, comprises an electrical resonant circuit 3 in which a capacitor 4 is arranged, in addition to the electrical component 2. The capacitor 4 can be charged using a suitable charging device 5. The charging device 5 is connected to a controller 7 by means of a fibre-optic waveguide 6. In a first control state of the controller 7, the capacitor 4 is charged by the charging device 5. If the controller 7 switches into a second control state, the electrical resonant circuit 3 is released and a high current pulse is generated in the electrical resonant circuit by the sudden discharge of the previously charged capacitor 4, which high current pulse excites a damped electrical oscillation in the electrical resonant circuit 3.

[0042] During the dying away electrical oscillation in the electrical resonant circuit 3, a voltage drop U(t) across the electrical component 2, the inductance L of which is intended to be determined, is measured using a digital oscilloscope 8.

[0043] In addition to the electrical component 2, a reference component 9 is arranged in the electrical resonant circuit 3. The reference component 9 also has an inductance L.sub.R which has been determined in advance by suitable measurements. A voltage drop U.sub.R(t) across the reference component can be measured via a further measuring channel, by means of the digital oscilloscope 8. If an ohmic resistance R in the electrical resonant circuit 3, or in particular in the electrical component 2, can be ignored, the sought inductance L of the electrical component 2 can be calculated approximately as a product of the known inductance L.sub.R of the reference component 9 and the quotient of the measured voltage drops U(t)/U.sub.R(t):

[00006]$L=L_R\frac{U\left(t\right)}{U_R\left(t\right)}$

[0044] In addition to the electrical component 2, an ammeter 10 designed for example as a Rogowski coil or Pearson coil is arranged in the electrical resonant circuit 3, the measured values of which ammeter can also be detected and evaluated using the digital oscilloscope 8. A current flow I(t) through the electrical component 2 is measured by the ammeter 10 during the electrical oscillations in the electrical resonant circuit 3. During the electrical oscillations, the ohmic resistance R of the electrical component 2 can be calculated, at the extreme points of the successive amplitude maxima I.sub.peak of the temporally variable current flow I(t), as a quotient of the voltage drop U(t=t(I.sub.peak)) at one extreme point I.sub.peak and the current flow I(t=t(I.sub.peak)) at the extreme point. Averaging for a plurality of successive extreme points or amplitude maxima of the current flow makes it possible for the ohmic resistance R, determined therefrom, to be further specified.

[0045] An evaluation of the measured values, measured over the measuring duration, for the two voltage drops U(t) and U.sub.R(t), and optionally for the current flow I(t), can be carried out by means of a suitable data processing facility 11 or an evaluation software executed thereon. In this case, the sought inductance L of the electrical component 2 can be determined as a product of the known inductance L.sub.R of the reference component 9 and a proportionality factor, wherein the proportionality factor results in the quotient of the difference between the measured voltage drop U across the electrical component 2 and the voltage drop R I across the ohmic resistance of the electrical component 2 on the one hand, and the measured voltage drop U.sub.R across the reference component 9 on the other hand. The calculation can be summarised by the formula set out in the following:

[00007]$\begin{array}{cc}L\left(I\right)=L_R\frac{\left(U\left(t\right)-\mathrm{RI}\left(t\right)\right)}{U_R\left(t\right)}& \end{array}$

[0046] In this case, the inductance L of the electrical component 2 is substantially dependent on the current flow I in question. Furthermore, in particular in the case of electrical components comprising soft magnetic materials, on account of the non-linear saturation behaviour, the inductance is also dependent on the relevant high current pulse or on a current flow brought about through the electrical component, directly prior thereto.

[0047] If the electrical component 2 comprises an inductive component having a soft magnetic material, it is expedient for the electrical resonant circuit 3 to be excited to electrical oscillation by a high current pulse of several kA.

[0048] The performance of a measurement for determining the inductance L of the electrical component 2 is explained on the basis of measuring device 1 shown in slightly more detail in FIG. 2. By means of a suitable software, the digital oscilloscope 8 receives, via an interface, a command from the data processing means 11 for generating an electrical control signal at one of the waveform outputs 12 thereof. Said control signal is forwarded to the controller 7 for high current pulse generation. Both the digital oscilloscope 8 and the controller 7 are connected to a voltage source 13 by suitable connections. A DC-to-DC converter 14 converts an output voltage of the voltage source 13 into an input voltage suitable for the digital oscilloscope 8. Depending on the duration of the control signal, a boost converter or a step-up converter (16, 17, 18, 19, 20, 21, 22) is actuated via a fibre-optic output 15 by means of pulse wave modulation generated by the controller 7, which converter charges the capacitor 4 to a voltage suitable for the high current pulse, via a charging resistor 23.

[0049] The boost converter preferably comprises an IGBT 16, a fibre-optic optocoupler 17, a charging capacitor 18, a diode 19, an inductive component 20, a capacitor 21, and a suitable voltage supply 22. Fibre-optic signal lines 24 and 25 ensure a galvanically isolated connection between a control and evaluation circuit 26 and an impulse and measuring circuit 27, and minimise the influence of electromagnetic interference signals which may arise in the impulse and measuring circuit 27. For reasons of operating safety, a common reference potential or a common earthing can be provided.

[0050] As soon as the control signal of the digital oscilloscope 8 is ended, the control signal transitions into a negative flank. Said negative flank deactivates the pulse wave modulation for the boost converter and activates a temporal sequence, stored in the controller 7, which activates a high current thyristor 28 via the galvanically isolated fibre-optic signal line 25. The control current for a thyristor 28 is generated by a fibre-optic signal processing means 29. Instead of a high current thyristor 28, another suitable control circuit can also be used, which circuit for example comprises an insulated-gate bipolar transistor (IGBT) or a metal-oxide-semiconductor field-effect transistor (MOSFET).

[0051] As a result, a high current pulse is generated and an electrical oscillation excited in the electrical resonant circuit 3. The electrical resonant circuit comprises the capacitor 4, the reference component 9, and the electrical component 2 to be measured. Both the maximally occurring peak amplitude of the current flow in the case of the high current pulse, and the rate of change of the current flow dI(t)/dt can be specified, and in particular limited, by means of suitable dimensioning of the reference component 9.

[0052] The voltage drop U across the electrical component 2 and the voltage drop U.sub.R across the reference component is detected via analogue inputs 30 of the digital oscilloscope 8, using suitable voltmeters 31, 32. The current flow I(t) through the electrical component is detected via a further analogue input 34 of the digital oscilloscope 8, using a suitable ammeter 10 which for example comprises a Pearson coil 33.

[0053] Since in most cases the resulting resonant circuit is undercritically damped, a flyback diode 35 allows for a current reversal and thus bipolar actuation of the electrical component, which is advantageous for numerous applications, such as for detecting the saturation behaviour of the electrical component.

[0054] The capacitor 4 can be discharged via a suitable resistor 36, by activating the thyristor 28. In this case, the resistor 36 should be dimensioned such that the impedance thereof is relatively large compared with the electrical component 2.

[0055] FIG. 3 shows, by way of example, the temporal progression, over a plurality of oscillations of the electrical resonant circuit 3, of the voltage U(t) 37 that drops across the electrical component 2, the reference voltage U.sub.R(t) 38 that drops across the reference component 9, and the current flow I(t) 39 flowing through the electrical component 2. The successive extreme points U.sub.1, U.sub.2, U.sub.3 etc. and I.sub.1, I.sub.2, I.sub.3 etc. of the individual temporal progressions can be determined by suitable mathematical methods. At the extreme points of the current flow, the ohmic resistance R of the electrical component 2 can in each case be determined, and averaged over a plurality of extreme points. Proceeding from two successive extreme values U.sub.1, U.sub.2, U.sub.3 etc., in each case, for the voltage drop U(t), the insertion loss a.sub.I(I.sub.puls) can be determined, the insertion loss a.sub.I(I.sub.puls) being dependent on the extreme value of the maximum current flow, proceeding from which the insertion loss a.sub.I(I.sub.puls) is determined.

[0056] For each half-wave following an extreme point of the current flow I.sub.1, I.sub.2, I.sub.3 etc., the inductance L(I.sub.puls=I.sub.1, I.sub.2, I.sub.3 etc.) that is dependent on the temporally changing progression of the current flow I(t) can be determined. For a plurality of successive extreme points of the temporal progression shown in FIG. 3, of the damped oscillation in the electrical resonant circuit 3, the relevant inductance L(I) is shown schematically, as a function of the current, in FIG. 4. In this case, the inductance L(I) is not the same for a specified current I, in particular at a comparatively low current flow of up to 150 A, but rather greatly dependent on the maximum value of the current flow at the preceding extreme point I.sub.1, I.sub.2, I.sub.3 etc. of the current flowing through the electrical component 2 during the damped oscillation. Using this information on the saturation behaviour of the electrical component 2, and the inductance or the energy losses EL of the electrical component 2 during a current flow, new electrical components can be designed such that they are adjusted as best as possible for the relevant intended purpose, in particular in terms of power electronics.