Device and method for measuring magnetic properties of ferromagnetic ring belt

Abstract

The invention discloses a device for determining the magnetic properties of a portion of a magnetizable endless belt and a corresponding method. The device comprises a primary coil for generating a magnetic field, a slotted yoke for guiding the magnetic flux and a plurality of coils for measuring.

Description

[0001] The present application relates to a device and a method for measuring a magnetizable endless strip, in particular a steel strip, the device comprising a coil for generating a magnetic field and a coil for measuring.

[0002] Transformer cores and stator cores as well as other cores consist of a large number of soft magnetic sheet metal layers (so-called iron sheets or steel sheets) which are electrically insulated from one another.

[0003] The single sheets of such a core made of laminated iron are usually made of punched or cut single sheets, which are punched from a steel strip or cut by longitudinal and transverse sections. The properties of the core therefore depend on the magnetic properties of the sheet, providing electrical insulation of the single sheets from each other. Therefore, the important magnetic parameter is the total power loss that occurs in the sheet when it is excited by an alternating magnetic field.

[0004] Such electrical steel strips are usually produced and supplied in the form of rolls (so-called coils, and also referred to as endless strips). The magnetic properties of the endless strips are different everywhere in the strip, but the areas between them may differ greatly.

[0005] Accordingly, it is desirable to measure the magnetic properties of such an endless belt made of ferromagnetic material in a non-destructive manner so as to know the magnetic properties of such an endless belt and to process areas of such an endless belt according to their respective magnetic properties.

[0006] Conventional devices for measuring the magnetic properties of such endless belts measure the measured values ​​of the magnetic properties of the endless belt collectively over the entire width of the belt.

[0007] US 3,281,678 describes a device through which an endless strip extends. The endless strip extends through an excitation coil and a measuring coil which measure over the entire width of the endless strip. Several measuring coils arranged adjacent to one another over the width of the endless strip, so-called field coils (field coil(s)) or H-coils, measure the magnetic properties of the endless strip together only over the entire width. In order to measure the magnetization losses of the endless strip, a measured magnetic flux density B can be generated in the endless strip by the excitation coil, the magnetic field H is measured using the H-coil, and the magnetic losses are determined in a known manner from the measured values ​​of B and H.

[0008] DE 24 11 565 C2 describes a device for continuously measuring the magnetism of a ring belt made of ferromagnetic material over the entire width of the ring belt. The device includes an excitation coil for generating a magnetic field, the winding of which extends over the entire width of the ring belt. The measuring coil is arranged inside the excitation coil and coaxial with the excitation coil, and is used to measure the magnetic flux induced in the ring belt when the ring belt is excited by the AC electromagnetic in the excitation coil. In addition, the device includes at least two yokes, which extend around the excitation coil and have an air gap for the ring belt to pass through and form a magnetic circuit. The at least two yokes are arranged at a certain distance from each other. Each yoke is composed of a large number of yoke strips that are insulated from each other and arranged side by side. The spaced arrangement of the two yokes and the subdivision of the yoke into respective yoke strips can subdivide the eddy current generated in the ring belt, thereby reducing the eddy current loss in the ring belt during the measurement process and improving the measurement accuracy when measuring the loss.

[0009] Based on this prior art, a device is needed for continuous measurement (ie inline measurement) of the annular strip, in particular in the case of alternating magnetic field excitation with the highest possible local resolution, which results in magnetic loss power over the entire width of the annular strip.

[0010] The device described below and its corresponding method allow the continuous measurement of the magnetic loss power of a ring belt with high local resolution over the entire width of the ring belt. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a perspective view of a device for determining the magnetic properties of a ferromagnetic ring band,

[0012] Figure 2 is a schematic diagram of a section through such an apparatus,

[0013] Figure 3 is a schematic diagram of a first arrangement of a measuring device for determining a magnetic field or a magnetic flux,

[0014] Figure 4a , 4b is a schematic diagram of another arrangement of a measuring device for determining a magnetic field or a magnetic flux.

[0015] In the figures described below, the same reference numerals refer to the same elements of the schematically illustrated device. The figures are neither drawn to scale nor do they show all the details. They serve only to illustrate various arrangements of the device. The figures show schematic diagrams of the device, essentially showing the arrangement of the excitation coil and the sensor or measuring coil. For the sake of clarity, the elements of the electrical and electronic device for triggering the excitation coil and the elements of the electronic device for evaluating the signals from the sensor or measuring coil are not shown, since for a person skilled in the art, the structure and the result of the triggering are determined by the following.

[0016] In the embodiments of the invention described below, the excitation coil is arranged above and below the annular band in order to be able to compensate for fluctuations in the distance between the coil and the annular band by averaging. In an alternative embodiment, the corresponding coil can only be arranged above or below the annular band if the distance between the annular band and the coil is known and constant. Similarly, in the embodiments described below, the probe coil is arranged above and below the annular band in order to detect the entire magnetic flux entering the yoke from the annular band. In an alternative embodiment, the probe coil can only be arranged above or below the annular band, provided that the corresponding magnetic flux can be determined with sufficient accuracy due to symmetry or other reasons.

[0017] Figure 1 A schematic perspective view of a device 1 for measuring the magnetism of an endless belt 2 is shown. The device comprises a housing 1a having an inlet side and an outlet side, on each of which a slot-shaped opening is arranged. During operation, the endless belt 2 enters the device at the inlet side and leaves the device at the outlet side, respectively, and the endless belt moves continuously through the device as shown by arrow 2a. The magnetism of the endless belt can be measured continuously while passing through the endless belt. In this way, the device can be used "inline" in a production line.

[0018] Figure 2 A schematic diagram of a section through the device in the direction of movement 2a of the endless belt 2 is shown, showing only the main coils or sensors of the device. The housing 1a is not shown in this figure.

[0019] A ferromagnetic endless strip 2, whose magnetic properties, in particular the losses during remagnetization, are to be measured, passes through the device and moves in the direction of arrow 2a.

[0020] The device comprises an excitation coil 3, also referred to in this system as a primary coil, in which its winding 3a and the current direction of the excitation current are drawn. It should be noted that the excitation current generally has a frequency of 50 Hz to 400 Hz, in particular 50 Hz or 60 Hz. Thus, this excitation coil 3 generates a magnetic field at the instant indicated by the arrow 4. The winding of the excitation coil 3 is guided around the annulus so that the width of the annulus lies in the magnetic field 4. The direction of the generated magnetic field 4 varies between parallel and antiparallel to the direction of movement of the annulus.

[0021] The device 1 comprises a slotted yoke 5 for guiding the magnetic field 4, the slots of the yoke 5 being arranged on the inlet side and the outlet side of the device and the annular band extending through the slots of the yoke 5. Figure 2 In the embodiment, a part of the yoke 5 is arranged below the annular belt 2 , and another part of the yoke 5 is arranged above the annular belt 2 .

[0022] The magnetic field 4 thus generated passes through the yoke 5 and between them through the endless belt 2 or parallel thereto through the air.

[0023] Furthermore, the device comprises a secondary coil 6, the winding of which extends coaxially with the winding of the excitation coil 3 and, like the excitation coil 3, extends around the entire width of the annular band 2, that is to say surrounds the annular band, and the secondary coil 6 is arranged inside the excitation coil 3. Furthermore, the secondary coil 6 is ideally arranged inside the excitation coil 3 so that the entire magnetic field passes through the secondary coil 6, so that the magnetic flux in the annular band can be measured with the secondary coil 6. In one embodiment, the secondary coil 6 is arranged inside the excitation coil 3 and has an insulating layer in the immediate vicinity of the winding of the coil 3. In this way, the secondary coil 6 allows the entire magnetic flux to be measured.

[0024] Furthermore, the device 1 has a plurality of so-called field coils 7 and a corresponding plurality of so-called probe coils 8 , so-called pick-up coil(s), a pair of field coils 7 being assigned to a correspondingly placed pair of probe coils 8 .

[0025] The device can measure the power losses during the magnetization process in different segments, which are placed adjacent to each other in the direction of movement of the endless belt, so that the magnetic properties are not measured over the entire width of the endless belt, but in narrower segments, the width of the endless belt being metrologically subdivided into a plurality of segments adjacent to each other, each having its own width. In this way, the endless belt can be metrologically divided into a plurality of segments, as described below, whose length is predetermined by the length of the measuring device and whose width is a fraction of the total width.

[0026] The total width of the endless belt, which is usually 0.9-2 m wide, is metrologically subdivided into width portions. The widths of the multiple portions can be identical to or different from one another. The width portions at the edges of the endless belt can be much narrower than the middle portion, for example in order to be able to better take into account edge effects.

[0027] The field coils 7 are arranged in pairs above and below the loop belt and are used to measure the magnetic field parallel to the surface of the loop belt. A pair of field coils for measuring the magnetic field is provided on the segment, that is, the width portion. The orientation of the field coils is parallel to the direction of the excitation coil 3. In this case, a plurality of field coils 7 are arranged adjacent to each other in the direction of the belt and are arranged so that the field strength of the magnetic field is measured over the entire width of the loop belt 2. The pairs of field coils 7 arranged above and below the loop belt detect the magnetic field strength with the same width, respectively, and the width of the field coil is the width of the segment, that is, the width portion of the segment. In a further description, the width of each field coil is equal to the measured width of the segment. In an optional embodiment, the magnetic field strength can be measured using other measuring devices, such as a Hall sensor or a magnetometer.

[0028] The device 1 further comprises a probe coil 8, also called a pick-up coil, for measuring the magnetic flux entering the yoke 5 from the loop 2 in a width portion. The probe coil 8 is arranged in an air gap or slot of the yoke 5. The probe coil 8 has a width for detecting the magnetic flux in such a width portion, which corresponds to the corresponding width of the field coil containing the magnetic field. In the following, the width of the probe coil is equal to the measurement width of the segment. Therefore, the probe coil 8 measures the magnetic flux of the width portion of the magnetic field strength that has been measured by a pair of field coils, so the coils or corresponding measuring devices each have the same width. For each width portion, the probe coil 8 is preferably arranged above the loop, and the probe coil 8 is arranged below the loop, wherein the magnetic flux of the same width as the loop 2 is detected in the width portion. The total magnetic flux of such a width portion or segment of the loop is the sum of the coils of the pair of probe coils placed above or below the loop.

[0029] In an alternative embodiment, the probe coil 8 and the field coil 7 may be replaced by another measuring device, for example by a Hall probe. The measuring device 8 for measuring the magnetic flux may be optionally placed at the inlet or outlet end of the device 1 .

[0030] The field coils 7 and the probe coils 8 are respectively allocated in pairs in the width of the loop 2, so that a pair of field coils 7 detects the magnetic field strength in the width portion of the loop 2, and the allocated pair of probe coils 8 measures the magnetic flux entering the yoke from the loop in the same width portion.

[0031] In this way, a pair of field coils 7 and a pair of probe coils 8 arranged in the same width portion of the loop detect the magnetic field strength parallel to the loop and the magnetic flux in the same width portion of the loop 2, i.e., in a section of the loop, thus allowing the calculation of the hysteresis and thus the loss value in the section.

[0032] The relevant power loss CPL of the annular belt section can be determined by the measured magnetic field strength H and magnetic flux density B. The magnetic field strength measurement consists of the upper field coil 7 and the lower field coil 7. In a section, the magnetic field strength measured above the annular belt is referred to as H in the following text. o , the magnetic field strength measured below the annulus is referred to as H in the following text u The measurement of the magnetic flux density of the sub-segment is carried out using the probe coil 8. The magnetic flux density measured in the sub-segment above the annulus is subsequently referred to as B o , and the magnetic flux density measured in the subsection below the annulus is called B u .

[0033] The magnetic field strength in a section is determined as follows:

[0034] First, the magnetic field strength in the sections above and below the annular band is determined using the field coils 7, wherein

[0035]

[0036] N: Number of windings

[0037] A: cross-sectional area through which magnetic flux passes

[0038] μ0: magnetic field constant

[0039] u Ho : The induced voltage in the upper field coil

[0040] u Hu : The induced voltage in the lower field coil

[0041] Then, assuming that the distances from the upper field coil and the lower field coil to the material surface are the same, calculate the magnetic field strength H u and H o Since the device meets this assumption, the average magnetic field strength H can be calculated 中

[0042]

[0043] The resulting magnetic field strength H averaged over each segment of the annulus is obtained by multiplying with the calibration factor k 区段 , which adapts the mean value of the field coil 7 to the magnetic field strength generated by the primary coil 3 .

[0044] H 区段 =k i *H 中

[0045] The magnetic flux density in a section is similarly determined. Since the magnetic flux of a section is generated by the sum of the partial magnetic fluxes or by the upper and lower probe coils, the voltages induced in the probe coils 8 are first added in pairs.

[0046] u B (t) = u Bo (t)+u Bu (t)

[0047] This results in a magnetic flux Φ B for

[0048]

[0049] Now, the measured magnetic flux Φ B It is section-dependent with the total magnetic flux density measured by the secondary coil 6. Correlation factor n i The magnetic flux density Φ B Adjusted to the measured magnetic flux density in a section so that

[0050]

[0051] have

[0052] N: The number of windings of the probe coil 8

[0053] A: The cross-sectional area through which the magnetic flux in the annular zone passes

[0054] Now we can measure a section of H 区段 and B 区段 Power loss determined by:

[0055]

[0056] f: frequency of exciting magnetic field

[0057] ρ: Average density of the annulus

[0058] T: Excitation period

[0059] Therefore, the power loss of a portion of the endless belt is determined from the measured magnetic flux density B and the measured field strength H of the width portion.

[0060] In order to carry out the calculation of the power loss in a section, the device comprises a suitable measuring transducer for converting the measured voltage / current into a digital signal and a digital signal processing device. The digitized measured values ​​are fed to the digital signal processing, wherein the power loss value of the corresponding section is determined based on the digitized measured values ​​and using a suitable computer program. The determined power loss value can be prepared and displayed in the form of a graphical representation.

[0061] Figure 3 A schematic arrangement of an excitation coil 7 or a corresponding measuring device for measuring the magnetic field and a probe coil 8 or a corresponding measuring device for measuring the magnetic flux in the endless band 2 entering the yoke 5 is shown. Figure 3 The annular strip 2, the primary coil 3 and the secondary coil 6 for measuring the entire magnetic field are not shown in the figure. The arrow 2a indicates the direction in which the annular strip extends through the first and second slots of the yoke 5.

[0062] The measuring device 7 for measuring the magnetic field above and below the annular belt has a width 7a, and the width of the measuring device 7 arranged above the annular belt (not shown) corresponds to the width of the measuring device arranged below the annular belt. Similarly, the measuring device 8 for measuring the magnetic flux entering the yoke 5 from the annular belt has a width 8a, and the width of the measuring device arranged above the annular belt also corresponds to the width of the measuring device arranged below the annular belt.

[0063] The width 7a or 8a of a portion of the endless belt (the magnetism of which is measured) is determined by the width of the measuring device 7 or the same width of the measuring device 8, that is, the width of the measuring device, so that the measuring device 7 and the measuring device 8 measure the magnetic field intensity or the magnetic flux of a width portion. Therefore, Figure 3 A design is shown in which, during measurement, the length section of the endless belt 2 in the device is subdivided metering-wise into three width sections arranged next to one another.

[0064] Figure 4a A schematic perspective view shows another arrangement of the measuring device 7 and the measuring device 8, which are arranged in the yoke 5 or in the air gap / slot of the yoke. Figure 3 As shown in FIG. 1 , the endless belt 2 and the primary excitation coil are not shown.

[0065] Figure 4b Schematic top view showing the arrangement of a measuring device 7 for measuring a magnetic field parallel to the annular band and a corresponding arrangement of the measuring device, a probe coil 8, for measuring the magnetic flux from the annular band into the yoke 5, Figure 4b The upper leg of the yoke 5 is not shown in order to illustrate the arrangement of the measuring device. As schematically shown here, the yoke 5 can consist of a plurality of partial yokes arranged side by side in the strip direction.

[0066] The direction of movement of the loop is again indicated by arrow 2a. The arrangement of the measuring devices shows that three measuring devices 7' are placed on the edge of the loop or one edge of the yoke 5, respectively, and their measuring width is smaller than the width of the eight measuring devices 7" arranged in the center. Similarly, the width of the probe coil 8' arranged at the edge of the loop or at the edge of the yoke 5 is correspondingly smaller than the width of the eight probe coils 8" arranged in the center. The measuring width of the measuring device 7 of the width portion corresponds to the measuring width of the measuring device 8 again, so that the magnetism of the width portion of the loop can be determined by means of a pair of measuring devices 7 and a pair of measuring devices 8. In this embodiment, a total of 14 pairs of measuring devices 7, such as field coils, and correspondingly 14 pairs of measuring devices 8, such as probe coils, are used to detect the magnetism of the length portion of the loop. The width of the three pairs of field coils 7' and the three pairs of probe coils 8' on each edge, respectively, has a width smaller than the width of the corresponding field coil pair 7" or probe coil 8", wherein the field coil pair 7" or probe coil 8" is further arranged in the center (i.e., in the center). This arrangement can therefore more finely determine the magnetism in the edge area of ​​the loop.

[0067] If a conventional device for determining the magnetic properties of a ferromagnetic ring belt has a yoke 5 and an excitation coil 3 and a secondary coil 6 for measuring the total magnetic field and spatial conditions in the device appropriately set, then a measuring device 7 for determining the magnetic field can be arranged parallel to the ring belt, that is, for example, a field coil 7, and a corresponding probe coil 8 can be arranged to measure the magnetic flux entering the yoke from the ring belt.

[0068] Reference Number List

[0069] 1Device for measuring magnetism

[0070] 1a Shell

[0071] 2 Ring belt

[0072] 2a Movement direction of the ring

[0073] 3 Excitation coil, primary coil

[0074] 4 Magnetic Field

[0075] 5. Yoke

[0076] 6 Secondary coil

[0077] 7 Field coils, measuring devices

[0078] 7a Width field coil measurement width

[0079] 7' field coil, measuring device in the edge area

[0080] 7” field coil, measuring device in the central area

[0081] 8Probe coil, measuring device

[0082] 8a Width Probe Coil 8 Measurement Width

[0083] 8' probe coil, measuring device in edge area

[0084] 8” probe coil, measuring device in the central area

Claims

1. A device (1) for determining the magnetic properties of a magnetizable endless band (2), characterized in that The device comprises: a primary coil (3) for generating a magnetic field (4), wherein the winding of the primary coil surrounds the annular band (2), wherein the magnetic field (4) generated by the primary coil (3) is parallel to the annular band (2), and - a secondary coil (6) for measuring the magnetic flux density, wherein the winding of the secondary coil (6) surrounds the annular band (2), and - a slotted yoke (5) for guiding the magnetic flux, wherein the annular band (2) extends through the slots in the yoke (5), and - a plurality of first measuring devices (7) for measuring the magnetic field (4) in various width sections parallel to the annular band (2), and - a plurality of second measuring devices (8) for measuring said magnetic flux in various width sections of the device annulus (2), The primary coil (3) is enclosed in the slotted magnetic yoke (5), and the secondary coil (6) and a plurality of the first measuring devices (7) for measuring the magnetic field (4) are enclosed in the primary coil (3).

2. The device according to claim 1, characterized in that The plurality of the first measuring devices and the plurality of the second measuring devices perform measurements in at least two width sections.

3. The device according to any one of the preceding claims 1 to 2, characterized in that The first measuring device (7) for measuring the magnetic field in the width section is arranged above and below the endless belt (2).

4. The device according to any one of the preceding claims 1 to 2, characterized in that The second measuring device (8) for measuring the magnetic flux density is arranged in the width portion above and below the endless belt.

5. The device according to claim 2, characterized in that The first measuring device (7) and the second measuring device (8) arranged at the edge of the endless belt (2) detect a smaller partial width than the first measuring device (7) and the second measuring device (8) arranged in the center.

6. A method for determining the magnetic properties of a width portion of a magnetizable endless band (2), characterized in that: The following steps are involved: - generating a magnetic field (4) parallel to the annular strip (2) and across the width of the annular strip (2), wherein the magnetic field is generated by a primary coil (3) whose windings surround the annular strip, and - determining the total magnetic field (4) generated by using a secondary coil (6) whose windings surround the annular band (2), and - measuring the magnetic field in a width portion (7a) parallel to the surface of the annular zone by means of a plurality of first measuring devices (7), and - measuring the magnetic flux entering the slotted yoke (5) from the width portion of the annular band (2) by means of a plurality of second measuring devices (8), and - determining the magnetic properties of the width portion of the endless belt based on the determined total magnetic field and the magnetic flux density in the width portion and the magnetic field of the width portion, The primary coil (3) is enclosed in the slotted magnetic yoke (5), and the secondary coil (6) and a plurality of the first measuring devices (7) for measuring the magnetic field (4) are enclosed in the primary coil (3).

7. The method according to claim 6, characterized in that The total width of the endless belt is divided metrologically into at least three width portions.

8. The method according to any one of the preceding claims 6-7, characterized in that The endless belt moves continuously.

9. The method according to any one of the preceding claims 6-7, characterized in that The magnetic field is measured in the width portions above and below the annulus.

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