A device for connecting a power source to an inductor

Abstract

A device (30) for connecting a power source (9) to an inductor (10), comprising at least three connection plates (11-14, 20) made of a conductive material and having any number of capacitors (7) electrically connected thereto, the connection plates enabling electrical connection between the power source and the inductor in a parallel, series, or series-parallel configuration, at least two connection plates bent substantially 90° to form two half plates (31-38) that are substantially perpendicular to each other, each half plate electrically connected to a different connection plate (11-14, 20).

Description

[Technical field]

[0001] The present invention relates to a device for locating a capacitor used in an oscillator circuit of an induction heating device. [Background technology]

[0002] (Technical problem addressed by the present invention) A device for placing a capacitor in an oscillator circuit comprises a connection plate made of a conductive material, typically copper, on which the capacitor is placed. A number of capacitors are usually placed on the plate, the number of which is related to its unit capacitance, the total capacitance desired, and the electrical characteristics (voltage, current, and frequency) of the oscillator circuit.

[0003] Current capacitor installation devices typically provide connection plates in parallel (in-line configuration), as shown diagrammatically in FIG. 1 for a series-parallel configuration. To facilitate understanding of the installation principle based on this figure, as well as on FIGS. 3, 7, 9 and 11, the dimensions are not to scale and the spacing between the plates is greatly emphasized. In this figure, four connection plates 1, 2, 3, 4 are arranged in parallel, including two outer plates and two central plates arranged in the same plane. The device therefore includes two insulating plates. In this example, and in this cross-sectional view, two capacitors 7 are fixed on the first outer plate 1 and one on the second outer plate 4. The two central connection plates 2, 3 are arranged between the two outer plates 1, 4. The insulating plates 5, 6 are, for example, made of Teflon and are arranged between the outer and central connection plates. In a longitudinal view of the device (not shown), a number of capacitors are connected over the height of the connection plates 1 and 4, the number of capacitors being related to the characteristics of the installation. The capacitor comprises means for fixing on the connection plate, for example a threaded hole for mounting with a screw, and an electrical connection rod 8, for example threaded. The connection plate comprises a hole along the electrical connection rod of the capacitor to allow said electrical connection rod to pass. The diameter of the hole of the connection plate is selected according to the diameter of the electrical connection rod so as to be large enough to prevent the passage of current between the rod of the capacitor and the plate to which it is fixed, thus ensuring the electrical insulation distance. The length of the electrical connection rod of the capacitor is such that it allows its connection to another connection plate. In this example, the capacitors of the outer plates 1, 4 are electrically connected to the central plates 2, 3 by nuts. The outer plates comprise a hole along the electrical connection rod of the capacitor to allow the passage of said nuts and the key for fixing the nuts. A power source 9 is electrically connected to plates 1 and 2, and an inductor 10 is electrically connected to plates 3 and 4. Figure 2 shows the electrical circuit diagram corresponding to this example of a series-parallel configuration from Figure 1.

[0004] In this type of in-line configuration, two outer plates 1,4 are separated by the presence of a central plate 2,3 and electrically insulating plates 5,6.

[0005] The disadvantages of this type of configuration are:

[0006] The large self-inductance caused by the wide spacing between the two externally connected plates (this self-inductance increases as the spacing between the plates increases).

[0007] This self-inductance creates electrical losses and therefore reduces efficiency, and current flow through the connections creates a magnetic field which heats up the connection plates, requiring greater cooling (image of electrical losses).

[0008] Giving operators access to the various components for installation and maintenance is often complicated. Summary of the Invention

[0009] According to a first aspect of the present invention, a device for connecting a power source to an inductor is proposed, comprising at least three connection plates made of a conductive material and to which any number of capacitors are electrically connected, the connection plates allowing an electrical connection between the power source and the inductor in a parallel, series or series-parallel configuration, characterized in that at least two connection plates are bent substantially by 90°, each forming two half-plates that are substantially perpendicular to each other, each half-plate being electrically connected to a different connection plate.

[0010] According to one possibility, one of the three connection plates may be substantially straight and may be electrically connected to two different connection plates.

[0011] According to another possibility, the device may comprise four connection plates bent substantially by 90°, each forming two half-plates substantially perpendicular to one another, each half-plate being electrically connected to a different connection plate, such that the assembly has a substantially cross-shape in cross-section.

[0012] Two connecting half-plates of the same connecting plate may be separated from two other connecting half-plates of another connecting plate by at least one plate made of insulating material and bent substantially by 90°.

[0013] Advantageously, the connection plate may comprise cooling channels through which a cooling fluid circulates.

[0014] According to a second aspect of the present invention, an induction heating apparatus is proposed, characterized in that it comprises a power supply and an inductor, the electrical connection between the power supply and the inductor being generated by at least one device according to the first aspect of the invention or one or more of its improvements.

[0015] The invention makes it possible to reduce the inductance in the connection to a negligible level and, as a consequence, to reduce the magnetic field generated by the currents circulating in the connection. [Brief description of the drawings]

[0016] Other features and advantages of the present invention will become apparent from the following detailed description, the understanding of which should be understood in conjunction with the accompanying drawings. [Figure 1] FIG. 1 is a schematic cross-sectional view of an in-line configuration of connection plates according to the prior art for a series-parallel configuration of capacitors. [Diagram 2] FIG. 2 is a schematic diagram of an electrical block diagram corresponding to the series-parallel configuration of FIG. [Diagram 3] 1 is a schematic cross-sectional view of a cross-shaped configuration of connection plates according to an embodiment of the present invention for a series-parallel configuration of capacitors. [Figure 4] FIG. 4 is a schematic diagram of an electrical block diagram corresponding to the series-parallel configuration of FIG. [Diagram 5] 1 is a schematic three-dimensional view from a first perspective of a cross-shaped configuration of connection plates according to an embodiment of the invention for a series-parallel configuration of capacitors. FIG. [Figure 6] FIG. 5 is a schematic three-dimensional view of the cross-shaped configuration from FIG. 4 from a second perspective. [Figure 7] 1 is a schematic cross-sectional view of a cross-shaped configuration of connection plates according to an embodiment of the present invention for a parallel configuration of capacitors. [Figure 8] FIG. 8 is a schematic diagram of an electrical block diagram corresponding to the parallel configuration of FIG. [Figure 9] 1 is a schematic cross-sectional view of a cross-shaped configuration of connection plates according to an embodiment of the present invention for a series configuration of capacitors. [Figure 10] FIG. 10 is a schematic diagram of an electrical block diagram corresponding to the parallel configuration of FIG. [Figure 11] 1 is a schematic cross-sectional view of a T-shaped configuration of connection plates according to an embodiment of the present invention for a series-parallel configuration of capacitors. [Figure 12] FIG. 12 is a schematic diagram of an electrical block diagram corresponding to the configuration of FIG. 11. [Figure 13] FIG. 12 is a schematic cross-sectional view of an alternative embodiment of the T-shaped configuration of the connecting plate from FIG. 11, shown here in a series-parallel configuration. [Figure 14] FIG. 14 is a schematic cross-sectional view of an alternative embodiment of the T-shaped configuration of the connecting plate according to FIG. 13, shown here in a side-by-side configuration. [Figure 15] FIG. 1 is a schematic longitudinal view of an exemplary application of the present invention;

[0017] Because the embodiments described below are not limiting in nature, it is specifically contemplated that variations of the invention may include only a selection of the described features, which selection of features is sufficient to provide a technical advantage or to distinguish the invention from the prior art. This selection includes at least one preferred functional feature that does not include structural details, or that includes only a portion of structural details, if this portion alone is sufficient to provide a technical advantage or to distinguish the invention from the prior art.

[0018] In the remainder of the description, elements having the same structure or similar function will be designated by the same references. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Figure 3 shows, in cross section, a schematic configuration of connection plates for a series-parallel configuration according to an embodiment of the present invention. The basic electrical circuit diagram for this, shown in Figure 4, is therefore similar to that shown in Figure 2. As can be seen from this figure, the four connection plates 11, 12, 13, 14 are bent at right angles, and the assembly essentially forms a cross in cross section. The connection plates are therefore spaced apart by the thickness of the insulating plates 15, 16, with no connection plates being located between the outer plates. The distance between the two connection plates is therefore reduced to a strict minimum value associated with the thickness of the insulating plates required to provide electrical insulation between the plates. Again, in a longitudinal view of the device (not shown), a number of capacitors are connected across the height of the connection plates 11 and 12, the number of capacitors being associated with the characteristics of the installation.

[0020] The advantages of this type of configuration are:

[0021] Negligible self-inductance due to optimal electrical compensation through reduced distance between the connecting plates, This creates very little electrical loss, resulting in very good efficiency.

[0022] The weak magnetic field generated by the current flowing through the connections results in little heating of the connection plate and therefore little cooling is required.

[0023] The various components are easily accessible to the operator for installation and maintenance.

[0024] Optimal electrical balance.

[0025] Advantageously, the insulating plates 15, 16 are also bent at right angles, thus preventing the risk of an electric arc in the centre of the cross, which would result from the use of a straight plate. Indeed, as shown in FIG. 3, the bent insulating plate ensures perfect continuity of the insulating material in the centre of the cross, while a straight plate would result in a discontinuity of the insulating material at the intersection of the centre of the cross, thus creating a point where the insulating material may be insufficient, i.e. the risk of a leakage path at the junction of the two plates. To facilitate the 90° bending of the insulating plate, it may be advantageous to use two plates of half the thickness instead of a single plate, which would be more difficult to bend. Thus, for example, instead of a plate with a thickness of 2 mm, it is possible to use two Teflon plates with a thickness of 1 mm.

[0026] Figures 5 and 6 show, in a longitudinal view and from two different viewing angles, another example of a capacitor installation device with a connecting plate in the shape of a cross and a series-parallel configuration according to the invention. In the three-dimensional drawings of these figures, the dimensional ratios of the components are closer to reality than in Figures 1 and 3. The assembly includes a set of eight capacitors. They are cooled by a flow of cooling water. For this purpose, each capacitor is provided with a first connection 17 for the cooling water supply and a second connection 18 for the water outlet. The capacitors can all be connected in series to the same cooling water circuit, or they can be connected individually or in groups of capacitors, each group being connected in parallel to the cooling circuit. The capacitors include a base made of a conductive material, for example copper, by means of which they are fixed to the connecting plate by four screws 19. This creates an electrical continuity between the connecting plate and the capacitors. The capacitors are provided with a threaded rod 8 for electrical connection with another connecting plate by means of a nut 21, on which the said capacitor is tightened. The connecting plate is provided with cooling channels 22, through which the cooling water circulates. Due to the limited heating of the connection plate, the cooling channels only cover part of the surface of the plate, i.e. the part where the current is strongest, as can be seen from figures 5 and 6. The capacitor also contributes to the cooling of the connection plate by its water-cooled base. This channel 22 comprises a first connection 23 for the cooling water supply and a second connection 24 for the water outlet. All the cooling channels 22 of the connection plate may be connected in series to the same cooling water circuit, or they may be connected in parallel. The cooling channels 22 of the connection plate may be connected in series on the same cooling water circuit as the capacitor, or on a separate circuit. The connection plates 11 and 12 are electrically connected through two compensators 7 and through a shunt ring 25 visible in figure 6. This cooled ring is fixed on the plate 11 by four screws, like the capacitor, and it also comprises a threaded rod 26 for its electrical connection with the plate 12 by a nut 27, on which it is tightened.The electrical connection between the connection plates via the capacitor 7 or the ring 25 allows easy transition from a series-parallel type configuration to a series or parallel configuration.

[0027] Figure 7 shows another embodiment of the invention including four connection plates arranged in the shape of a cross with a parallel configuration. In this cross-sectional view, this example includes a capacitor 7 and two shunt rings 25. Again, the total number of capacitors and rings arranged longitudinally depends on the desired characteristics. The equivalent electrical circuit diagram is shown in Figure 8.

[0028] Figure 9 shows another exemplary embodiment of the invention, including four connection plates arranged in the shape of a cross with a series configuration. In this cross-sectional view, this example includes two capacitors 7. Again, the total number of capacitors and rings arranged longitudinally depends on the desired characteristics. The equivalent electrical circuit diagram is shown in Figure 10.

[0029] Figure 11 shows another exemplary embodiment of the present invention in the shape of a "T" including three connecting plates. In this configuration, two of the connecting plates 11, 12 are bent by 90 degrees and the third 20 is straight. The equivalent electrical circuit diagram in series-parallel is shown in Figure 12. In particular, due to the distance between each pair of connecting plates being reduced to the minimum possible, all the advantages of the present invention are retained.

[0030] In an alternative embodiment shown in FIG. 13, the curved plates 11, 12 are formed in two parts, 11a, 11b, 12a, 12b. They are fixed to each other by screws and nuts. This setup allows the series capacitors to be easily removed, so that it is possible to move to a parallel configuration only. This is intended for applications where flexibility is required during use (changing the power supply-inductor-component match), which may be necessary when very diverse components are heated. For the transition from the series-parallel configuration to the parallel configuration, the parts 11a, 12a are removed. They are replaced by a connecting piece 28 fixed by screws and bolts, as shown in FIG. 14.

[0031] The invention applies in particular to the following conditions:

[0032] Frequency: Medium frequency (15kHz~2MHz) Input voltage: typically less than 1kV Output voltage: Maximum 8kV (voltage rise) Output current: Max. 50kA Power for installed devices:>100kW

[0033] 15 shows, in a front view, a schematic example of an exemplary application of the invention for connecting a power source to an inductor intended to heat a moving metal strip in a continuous annealing line. To transfer the required power to the device, the connection between the power source 9 and the inductor 10 is created by four devices 30 in a cross-shaped configuration according to the invention, the characteristics of which are as follows:

[0034] Series / parallel configuration Number of capacitors: 72 (4 modules of 18 capacitors) Supply voltage: 500V Output voltage: 2500-3000V Output current: 40kA Reactive power: 4MW

[0035] As can be seen from FIG. 15, the implementation of the present invention allows for a compact installation of the heating device, and thanks to the compactness of the capacitor installation device due to the elimination of straight connecting plates, the distance between the power source and the inductor is limited.

[0036] As will be readily understood, the present invention is not limited to the examples just described, and numerous modifications may be made to these examples without departing from the scope of the present invention. In addition, the various features, forms, variations, and embodiments of the present invention may be grouped together in various combinations, unless they are incompatible or mutually exclusive.

Claims

1. A device (30) for connecting a power source (9) to an inductor (10), comprising at least three connection plates (11-14, 20) made of an electrically conductive material and to which any number of capacitors (7) are electrically connected, said connection plates allowing an electrical connection between said power source and said inductor in a parallel, series or series-parallel configuration, characterized in that at least two connection plates are bent substantially by 90° to form two half-plates (31-38), each substantially perpendicular to one another, each half-plate being electrically connected to a different connection plate (11-14, 20).

2. The device (30) according to claim 1, characterized in that one (20) of the three connection plates (11-14, 20) is substantially straight and is electrically connected to two different connection plates (11-14).

3. 2. The device (30) according to claim 1, comprising four connection plates (11-14) bent substantially by 90°, each forming two half-plates (31-38) that are substantially perpendicular to each other, each half-plate being electrically connected to a different connection plate (11-14, 20), and having a substantially cross-shaped cross section.

4. 4. The device (30) according to claim 3, characterized in that two connecting half-plates (31-38) of the same connecting plate (11-14) are separated from two other connecting half-plates (31-38) of another connecting plate (11-14) by at least one plate made of insulating material and bent substantially by 90°.

5. The device (30) according to any one of claims 1 to 4, characterized in that the connecting plates (11-14) comprise cooling channels (22) through which a cooling liquid circulates.

6. 6. An induction heating apparatus comprising a power source (9) and an inductor (10), characterized in that the electrical connection between the power source and the inductor is generated by at least one device (30) according to any one of claims 1 to 5.

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