Measuring device and method for determining magnetic properties of a magnetizable test specimen

Abstract

A measuring device for determining magnetic properties of a magnetizable test specimen comprises a measuring coil winding which passes around a magnetizable measuring coil core. The measuring coil core comprises magnetic flux passage faces arranged at a distance from one another. The test specimen is arranged adjacently to the magnetic flux passage faces. A high-current pulse through the measuring coil winding causes a magnetic flux through the measuring coil core and the test specimen. A temporal profile of electrical characteristic variables of the measuring coil winding is detected using a sensor device. The electrical characteristic variables of the measuring coil winding detected by the sensor device are set in a ratio to additionally ascertained electrical characteristic variables of the measuring coil winding without the test specimen. A magnetic property of the test specimen is determined from the ratio of the electrical characteristic variables to one another.

Claims

1. A measuring device (2) for determining magnetic properties of a magnetizable test specimen (16), comprising: a measuring coil core (6) comprising magnetic flux passage faces (15) arranged at a distance from one another; a measuring coil winding (7) which passes around the measuring coil core (6); an energy supply device (3) configured to supply electrical energy to the measuring coil winding (7); a sensor device (8) configured to detect a characteristic variable for the magnetic properties of the magnetizable test specimen (16), wherein the energy supply device (3) is designed and set up in such a way that a high-current pulse can be generated by the energy supply device (3) and conducted through the measuring coil winding (7), wherein the magnetizable test specimen (16) can be arranged adjacently to the magnet flux passage faces (15) during a measurement process in such a way that the high-current pulse conductable through the measuring coil winding (7) can bring about a magnetic flux (14) through the measuring coil core (6) and the magnetizable test specimen (16), and wherein the sensor device is designed and set up in such a way that a temporal profile of electrical characteristic variables of the measuring coil winding (7) can be detected using the sensor device (8).

2. The measuring device (2) according to claim 1, wherein the measuring coil core (6) consists of a material with high magnetic permeability.

3. The measuring device (2) according to claim 1, wherein the magnetizable test specimen (16) is arranged movably at the magnetic flux passage faces (15).

4. The measuring device (2) according to claim 1, wherein the measuring coil core (6) is U-shaped.

5. The measuring device (2) according to claim 1, wherein the magnetic flux passage faces (15) of the measuring coil core (6) have a surface roughness with a mean roughness value of less than 0.5 μm.

6. The measuring device (2) according to claim 1, further comprising: a second magnetizable measuring coil core (6), comprising further magnetic flux passage faces (15) which are arranged opposite the magnetic flux passage faces (15) of the magnetizable measuring coil core (6) passed around by the measuring coil winding (7), wherein the magnetizable test specimen (16) can be arranged between the magnetic flux passage faces (15) and the further magnetic flux passage faces (15) in such a way that the magnetic flux (14) generated by the measuring coil winding (7) can be guided and can run through the measuring coil core (6) and the second magnetizable measuring coil core (6) and the magnetizable test specimen (16).

7. The measuring device (2) according to claim 1, wherein the measuring device (2) comprises a magneto-optical sensor device (18) configured to optically detect a magnetization of the magnetizable test specimen (16).

8. The measuring device (2) according to claim 1, wherein the measuring coil winding (7) consists of multicore lines, and wherein the multicore lines are electrically insulated with respect to one another.

9. A method (20) for ascertaining a magnetic property of a magnetizable test specimen (16), comprising: arranging, in a measurement step (23), the magnetizable test specimen in a measurement position relative to a measuring coil core with a measuring coil winding of a measuring device (2) passing around the measuring coil core; using an energy supply device (3), which is electrically conductively connected to the measuring device (2), to guide a high-current pulse created by the energy supply device (3) through the measuring coil winding (7) of the measuring device (2); detecting a temporal current and voltage profile through the measuring coil winding (7); ascertaining, in a subsequent ascertainment step (25), a characteristic value for a magnetic property of the test specimen (16) based on the detected current and voltage profile by comparing the current and voltage profile, detected with the magnetizable test specimen, for the magnetizable test specimen (16) and the measuring device (2) with a corresponding profile of a reference current profile and reference voltage profile; and ascertaining a characteristic variable for the magnetic property of the test specimen (16) from a difference between the measured current profile and voltage profile and the reference current profile and reference voltage profile.

10. The method (20) according to claim 9, wherein the high-current pulse generated by the energy supply device (3) and guided through the measuring coil winding (7) is predefined such that a magnetic flux generated in the magnetizable test specimen by the high- current pulse is adapted to a magnetic saturation of the magnetizable test specimen (16).

11. The method (20) according to claim 9, further comprising: moving, in a movement step (26), the magnetizable test specimen (16) relative to magnetic flux passage faces (15) of the measuring coil core (6).

12. The method (20) according to claim 9, further comprising: detecting, in a magnetic field detection step (24), a magnetic flux density of the magnetic field by a magneto-optical sensor device (18) at a surface of the test specimen (16).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Hereinafter, schematic representations show exemplary embodiments of the invention.

[0046] FIG. 1 shows a measuring system for measuring magnetic properties and characteristic variables of a magnetizable test specimen using a measuring device, an energy supply device and a measurement processing device.

[0047] FIG. 2 shows two U-shaped measuring coil cores with a measuring coil winding and a test specimen arranged between them.

[0048] FIG. 3 shows a magnetizable test specimen with a measuring coil winding, a measuring coil core and a magnetic field camera.

[0049] FIG. 4 shows a sequential flowchart of the method for detecting magnetic properties of a magnetizable test specimen.

[0050] FIG. 5 shows a characteristic diagram of the measuring coil winding calculated by a method for detecting magnetic properties of a magnetizable test specimen.

[0051] FIG. 6 shows an alternative embodiment of the measuring system with a converter as energy supply device.

DETAILED DESCRIPTION

[0052] FIG. 1 shows a measuring system 1 according to the invention with a measuring device 2 according to the invention and an energy supply device 3. The energy supply device 3 comprises an energy source 4, which can provide both direct and alternating voltages, and a pulse generator 5, which, supplied by the energy source 4, can generate the high-current pulse.

[0053] By contrast, the measuring device 2 comprises a U-shaped measuring coil core 6, which is passed around by a measuring coil winding 7, and a sensor device 8, which has a voltage measurement point 9 and a current measurement point 10, wherein the sensor device 8 is suitable for detecting the electrical characteristic variables of the measuring coil winding 7. The measuring device 2 and the energy supply device 3, specifically the pulse generator 5, are connected to one another via electrical lines 11, so that the high-current pulse generated by the pulse generator 5 can act on the measuring coil winding 7, while the sensor device 8 can detect the electrical characteristic variables.

[0054] Furthermore, the current measurement point 10 and voltage measurement point 9 are connected via signal lines 12 to a measurement processing device in the form of a computer 13, so that the current and voltage profiles at the measuring coil winding 7 can be reliably processed and saved.

[0055] If a high-current pulse is applied to the measuring coil winding 7, a magnetic flux 14 forms in the measuring coil core 6 and runs along the measuring coil core 6 and exits and enters again from two magnetic flux passage faces 15.

[0056] If a test specimen 16 is arranged in the vicinity of the magnetic flux passages faces 15, the magnetic flux 14 also runs through the test specimen 16. In a reference measurement, the magnetic losses of the measuring coil core 6 can be ascertained when there is no test specimen 16 arranged at the magnetic flux passage faces 15. Wherein in a subsequent measurement run, which is performed with the test specimen 16 bearing against the magnetic flux passage faces 15, the total power loss from the test specimen 16 and the measuring coil core 6 can be ascertained. With the aid of mathematical calculation, the two power losses, that is to say a power loss of the test specimen 16 and also of the measuring coil core 6, can then be separated, whereby the magnetic quality of the test specimen 16 can then be rated.

[0057] As shown in FIG. 1, the test specimen 16, which is much longer along a movement direction 17 than the measuring coil core 6, can be moved along the movement direction 17. The magnetic power loss of the longer test specimen 16 can thus be measured in some portions of the test specimen with a regional resolution in a length of the measuring coil core 6.

[0058] The indirect measurement of the magnetic flux 14 via the electrical characteristic variables detected using the sensor device 8 can usually be achieved more precisely, more reliably or more economically than a direct measurement of the magnetic flux 14 via magnetic field sensors or the like. Furthermore, more detailed and complex calculations and visualization can be performed in the computer 13, so that more than just the magnetic flux 14 can be directly measured and evaluated.

[0059] An alternative embodiment of a region around the test specimen 16 is shown in FIG. 2. In this schematic illustration, the test specimen 16 on the one hand is likewise arranged at the two magnetic flux passage faces 15 of the measuring coil core 6, and on the other hand the measuring device 2 has a second U-shaped measuring coil core 6, which is arranged on the left side of the test specimen 16. This can be advantageous because the magnetic flux 14 generated by the high-current pulse can thus distribute better and more uniformly in the test specimen 16, since the magnetic flux 14 can likewise flow through the second measuring coil core 6.

[0060] Furthermore, the second measuring coil core 6 can also have its own measuring coil winding 7, which could generate an additional component of the magnetic flux 14 in the test specimen 16, however this is not explicitly shown in this illustration.

[0061] FIG. 3 shows a further embodiment of the measuring device 2, in which the second measuring coil core 6 has been replaced by a magneto-optical sensor device 18. By means of the magneto-optical sensor device 18, for example a magnetic field camera, the measuring device 2 can detect a magnetic flux density on a surface 19 of the test specimen 16 resulting from the magnetic flux 14 within the test specimen.

[0062] The magneto-optical sensor device 18 can be used to determine a distribution, a uniformity and an intensity of the magnetic flux density on the detected surface 19, which can be advantageous for a continuous quality control.

[0063] A flowchart of the method 20 according to the invention is shown schematically in FIG. 4. Here, a measurement process of the method 20 starts with a reference measurement step 21, in which the current and voltage profiles are detected by means of a sensor device 8, without a test specimen 16 being arranged at the magnetic flux passage faces 15 of the measuring coil core 6. Wherein the reference measurement step 21 can also be performed more than once by means of a branching 22 in accordance with a pre-setting. The repeated performance of the reference measurement step 21 makes it possible to form a reliable mean value of the electrical characteristic variables detected by the sensor device 8.

[0064] A measurement step 23 and a magnetic field protection step 24 are then performed in parallel. In the measurement step 23, the measuring coil winding 7 of the measuring device 2 is acted on by the high-current pulse and the electrical characteristic variables are detected by means of the sensor device 8 and current measurement point 10 and voltage measurement point 9 thereof. At the same time, a magnetic field camera 18 in the magnetic field detection step 24 detects the magnetic flux density of the surface 19 of the test specimen 16.

[0065] In a following calculation step 25, the respective losses of the measuring coil 6 and of the test specimen 16 are calculated, merged and/or visualized on the basis of the detected measurement data and characteristic variables.

[0066] In a last, movement step 26, the test specimen is moved in automated fashion in the movement direction 17 by a pre-set value, so that a new portion of the test specimen 16 can be measured in accordance with the method 20 according to the invention.

[0067] A function graph 27 resulting from the high-current pulse and detected and calculated by the measuring device 2 is shown schematically in FIG. 5. A current intensity through the measuring coil winding 7 detected by the sensor device 8 and current measurement point 10 thereof is plotted in amperes [A] along an abscissa 28, wherein integrated voltage-time values in volt seconds [Vs] of the voltage at the measuring coil winding 7 detected by a sensor device 8 and voltage measurement point 9 thereof are plotted along an ordinate 29.

[0068] The profile of the function graph 27 starts at a coordinate origin 30 and increases linearly to a saturation current value 31, after which the profile of the function graph 27 levels off significantly, since the measuring coil winding 7 is saturated, until at a peak current value 32 the profile of the function graph 27 reverses, since the high-current pulse likewise subsides. The subsiding high-current pulse causes a profile of the function graph 27 that descends in a reverse sequence and makes a stop, once the high-current pulse has subsided, at a residual magnetization value 33.

[0069] An enclosed energy area 34 of the function graph 27 has the unit of an energy (VAs) so that the magnetic losses of the performed measurement process can be determined via the enclosed energy area 34. After a plurality of measurement processes, with and without the test specimen 16, the ascertained total power losses can be allocated proportionally in computer-generated fashion to the test specimen 16 and the measuring coil core 6.

[0070] FIG. 6 shows an alternative embodiment of the measuring system 1 according to the invention with the measuring device 2, the energy supply device 3 and the computer 13. The energy supply device 3, in contrast to the previous figures, does not have a separate energy source 4 and no separate pulse generator 5. Both are now integrated in a converter 35.

[0071] The high-current pulse is provided in the shown illustration by four power semiconductor switches 36 interconnected to form an H-bridge circuit, wherein the energy for the high-current pulse can be drawn from a DC link 37, which in turn should be charged by an external energy source (not shown) for example a battery or a rectifier.

[0072] The differently formed high-current pulses can be generated by corresponding switch positions of the power semiconductor switches 36. The power semiconductor switches 36 in this case can be thyristors IGBTs or also MOSFETs.

[0073] While the present invention has been described with reference to exemplary embodiments, it will be readily apparent to those skilled in the art that the invention is not limited to the disclosed or illustrated embodiments but, on the contrary, is intended to cover numerous other modifications, substitutions, variations and broad equivalent arrangements that are included within the spirit and scope of the following claims.

[0074] The words “example” and “exemplary” as used herein mean serving as an instance or illustration. Any embodiment or design described herein as “example” or “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or designs. Rather, use of the word example or exemplary is intended to present concepts in a concrete fashion. In addition, the articles “a” and “an” as used in this application and the appended claims should generally be construed to mean “one or more” unless specified otherwise or clear from context to be directed to a singular form.

LIST OF REFERENCE SIGNS

[0075] 1. measuring system

[0076] 2. measuring device

[0077] 3. energy supply device

[0078] 4. energy source

[0079] 5. pulse generator

[0080] 6. measuring coil core

[0081] 7. measuring coil winding

[0082] 8. sensor device

[0083] 9. voltage measurement point

[0084] 10. current measurement point

[0085] 11. electrical line

[0086] 12. signal lines

[0087] 13. measurement processing device/computer

[0088] 14. magnetic flux

[0089] 15. magnetic flux passage faces

[0090] 16. test specimen

[0091] 17. movement direction

[0092] 18. magneto-optical sensor device

[0093] 19. surface

[0094] 20. method

[0095] 21. reference measurement step

[0096] 22. branch

[0097] 23. measurement step

[0098] 24. magnetic field detection step

[0099] 25. calculation step

[0100] 26. movement step

[0101] 27. function graph

[0102] 28. abscissa

[0103] 29. ordinate

[0104] 30. coordinate origin

[0105] 31. saturation current value

[0106] 32. peak current value

[0107] 33. residual magnetization value

[0108] 34. enclosed energy area

[0109] 35. converter

[0110] 36. power semiconductor

[0111] 37. DC link