Braking resistor comprising individual sheets, and drive system having a braking resistor

Abstract

The invention relates to a braking resistor comprising individual sheets, wherein: each individual sheet has mutually spaced first and second transverse slits located one behind the other in the longitudinal direction; the first transverse slits extend into the individual sheet in question from the edge of the individual sheet in question which is at the right as seen in the longitudinal direction; the second transverse slits extend into the individual sheet in question from the edge of the individual sheet in question which is at the left as seen in the longitudinal direction; as seen in the longitudinal direction, the first and second transverse slits are located one behind the other in alternation.

Description

[0001] Braking resistor, comprising individual sheets and drive system with braking resistor

[0002] Description:

[0003] The invention relates to a braking resistor comprising individual sheets and a drive system with braking resistor.

[0004] It is known that braking resistors are used to convert generator energy into thermal energy.

[0005] From JP H08 - 78 201 A, a resistance element is known as the closest prior art.

[0006] A resistor arrangement is known from DE 10 2010 055 475 A1.

[0007] A braking resistor for a crane is known from KR 10 2009 123 072 A.

[0008] From DE 10 2016 004 062 A1 a drive comprising an electric motor fed by a converter is known.

[0009] A resistance element is known from JP 000S51161542 U.

[0010] A resistance element is also known from FR 1 479 622 A.

[0011] A resistor is known from US 4 588 976 A.

[0012] A resistance grid is known from US 2 665 358 A.

[0013] A method for operating a drive system is known from DE 10 2019 005 019 A1.

[0014] The invention is therefore based on the object of designing a braking resistor that is compact and cost-effective. According to the invention, this object is achieved with the braking resistor according to the features specified in claim 1.

[0015] Important features of the invention in the braking resistor are that the braking resistor, comprising individual sheets, in particular wherein each individual sheet has a length provided in the longitudinal direction which is greater than a width of the individual sheet, in particular as a width of the individual sheet measured in the transverse direction, i.e. perpendicular to the longitudinal direction, in particular wherein the width is greater than the sheet thickness of the individual sheet, wherein the respective individual sheet has first and second transverse slots arranged one behind the other in the longitudinal direction and spaced from one another, in particular wherein the first and second transverse slots are aligned parallel to one another and run in the transverse direction, i.e. perpendicular to the longitudinal direction, wherein the first transverse slots protrude into the individual sheet from the right edge of the respective individual sheet, as seen in the longitudinal direction,wherein the second transverse slots project from the left edge of the respective individual sheet, viewed in the longitudinal direction, into the individual sheet, wherein, viewed in the longitudinal direction, the first and the second transverse slots are arranged one behind the other, each alternating, in particular wherein the area covered by the first transverse slots in the transverse direction overlaps the area covered by the second transverse slots, wherein the transverse direction is oriented perpendicular to the longitudinal direction.

[0016] The advantage here is that the material is meandering, thus achieving the longest possible cable length while saving space. In an advantageous design, the individual sheet has a meandering section extending longitudinally by means of the transverse slots. This is advantageous because it enables efficient use of the space in a simple manner.

[0017] In an advantageous embodiment, the individual sheet is made of a flat steel sheet, particularly a rectangular flat steel sheet. The advantage here is that a chromium-alloyed steel can be used as the material. Although the rigidity of the simple steel is lower than that of stainless steel, the bent folds allow for stabilization of the individual sheet. This allows the braking resistor to be made of cost-effective steel and yet is less susceptible to vibration and therefore quieter during operation, especially when operated with an inverter-fed electric motor.

[0018] In an advantageous embodiment, the individual sheet metal part is manufactured as a stamped and bent part. This allows for simple production. Preferably, a full stamping is used, so that no waste is generated during the stamping and bending process, or a stamping with only minimal waste.

[0019] In an advantageous embodiment, an edge region of the individual sheet bordering the respective transverse slot in the longitudinal direction is bent by a first angular amount, in particular, and is formed as a fold. This is advantageous in that the rigidity of the individual sheet is increased, thus enabling quiet operation.

[0020] In an advantageous embodiment, an edge region of the individual sheet bordering the respective transverse slot at the rear in the longitudinal direction is bent by a second angle, in particular, and is formed as a fold. It is advantageous that the strut formed between two adjacent transverse slots has two spaced-apart folds with corresponding bending angles.

[0021] In an advantageous embodiment, the first angle is equal to the second angle, in particular so that the respective transverse slot is arranged centrally between the edge regions. It is advantageous that the strut formed between two adjacent transverse slots has two spaced-apart folds with corresponding bending angles. The equality of the two bending angles allows for particularly high rigidity. This shifts a mechanical resonance frequency of the strut to very high

[0022] Frequency values ​​indicate that the angle value does not disappear but increases.

[0023] In an alternative advantageous embodiment, the first angle differs from the second angle, in particular, it deviates by at least 20°. Advantageously, the strut formed between two adjacent transverse slots has two spaced-apart folds with corresponding bending angles. By selecting different angles, a first fold on the strut has a different bending angle than a second fold. This allows for increased stiffness of the strut.

[0024] In an advantageous embodiment, the first angle is at least 30° and at most 90°. This is advantageous because particularly high rigidity can be achieved, since the rigidity is only slightly increased below 30°.

[0025] In an advantageous embodiment, the second angle is at least 30° and at most 90°. This is advantageous because particularly high rigidity can be achieved, since the rigidity is only slightly increased below 30°.

[0026] In an advantageous embodiment, an edge area is bent, particularly as a fold, on only one side of the respective transverse slot. The advantage here is that the asymmetrical design of the strut with only one fold on one side allows for particularly high rigidity of the struts of the individual sheet.

[0027] In an advantageous embodiment, the individual sheet is made of a steel sheet, especially one that is not made of stainless steel. This allows for the use of a cost-effective material that is less rigid than stainless steel. This is because the folds provide stiffening. Furthermore, bending the folds requires less energy than with stainless steel. Sheets of varying hardness can be used.

[0028] In an advantageous embodiment, the individual sheet is made of a steel sheet that has a lower hardness than a stainless steel sheet, in particular a stainless steel sheet with a geometrically identical shape, and / or that has a higher magnetic permeability than a stainless steel sheet, in particular a stainless steel sheet with a geometrically identical shape. The advantage here is that such a material can be used despite the higher magnetic permeability. Magnetic fields from adjacent current-carrying struts induce a greater force, which could generate stronger vibrations; however, the folds prevent the vibrations from oscillating and thus reduce noise generation.

[0029] In an advantageous embodiment, each transverse slot opens into the environment with its first end, in particular the open end, and is closed at its second end, in particular the other end, wherein the transverse slot is rounded at this second end, in particular circularly rounded, in particular by punching out a circular segment from the individual sheet, in particular so that a respective edge region of the individual sheet bordering the respective transverse slot has a straight edge at its edge facing the second end of the transverse slot, in particular as a result of the punched out circular segment. The advantage here is that the stiffening of the individual sheet is further improved and thus noise generation is reduced. In addition, by punching out the circular segment, the fold is safely away from the rounded edge region of the individual sheet, even when bending.The punching out of the circular segment also changes the natural frequencies of the individual sheet, shifting them to higher values. This reduces structure-borne noise and thus also sound radiation.

[0030] Important features of the drive system with braking resistor are that the drive system comprises an electric motor, in particular a three-phase motor, fed by an inverter, and a rectifier. The DC voltage connection of the rectifier is arranged parallel to the DC voltage connection of the inverter and parallel to a series circuit comprising the braking resistor and, connected in series with it, a controllable semiconductor switch, in particular a braking chopper. The advantage here is that energy generated by a generator can be dissipated from the intermediate circuit via the braking resistor in order to prevent a critical increase in the intermediate circuit voltage of the converter. The controllable semiconductor switch, in particular the braking chopper, is controlled by a pulse-width modulated signal.

[0031] In an advantageous embodiment, the inverter comprises controllable semiconductor switches whose respective control signals are pulse-width modulated. The pulse-width modulation frequency of the control signal of the brake chopper is swept and / or modulated in a frequency band, in particular one having a first frequency value, in particular wherein the frequency band has a bandwidth of more than 10% of the frequency value, in particular of less than 50% of the frequency value. This is advantageous in that as little structure-borne noise as possible is generated in the brake resistor, especially at the individual metal sheet.

[0032] Further advantages emerge from the dependent claims. The invention is not limited to the combination of features in the claims. Further possible combinations of claims and / or individual claim features and / or features of the description and / or the figures will become apparent to those skilled in the art, particularly from the problem and / or the problem posed by comparison with the prior art.

[0033] The invention will now be explained in more detail using schematic illustrations:

[0034] In Figure 1, an individual sheet 3 of a braking resistor according to the invention is shown in an oblique view, wherein a fold 4 is provided on one side of each slot (1, 2).

[0035] Figure 2 shows a corresponding top view.

[0036] Figure 3 shows an area of ​​Figure 2.

[0037] In Figure 4, an individual sheet 3 of a second braking resistor according to the invention is shown in an oblique view, wherein folds (20, 21) with different bending angles are provided on both sides of a respective slot (1, 2).

[0038] Figure 5 shows a corresponding top view.

[0039] Figure 6 shows an area of ​​Figure 2.

[0040] As shown in Figures 1 to 3, the individual sheet 3 has a length which is more than three times the width of the individual sheet 3, in particular which in turn is more than ten times the sheet thickness of the individual sheet 3.

[0041] In the longitudinal direction, along which the length is measured, the individual sheet 3 has transverse slots which extend alternately from the right or left edge into the individual sheet 3, in particular do not extend continuously into the individual sheet 3.

[0042] The transverse slots, which are particularly straight, are spaced apart from one another and are particularly aligned parallel to one another.

[0043] With the exception of the first and last transverse slots (1, 2), each transverse slot extending from the right edge of the individual sheet 3 is assigned a transverse slot extending from the left edge of the individual sheet 3 in the longitudinal direction and, counter to the longitudinal direction, as the next adjacent slot. The individual sheet 3 is manufactured as a stamped and bent part, with the transverse slots being stamped and the region of the individual sheet 3 that is adjacent to the respective transverse slot (1, 2) in the longitudinal direction being bent, in particular bent upwards.

[0044] The bending angle in the embodiment according to Figure 1 is approximately 90°.

[0045] In this way, a longitudinally meandering course of the material of the individual sheet 3 is formed.

[0046] In the braking resistor, several of such aforementioned individual laminations 3, which are similar or identical to one another, are arranged parallel to one another in a stack, with electrical insulation means interposed between them. The individual laminations 3 are electrically connected in series. The current flowing meanderingly through the series connection of the individual laminations 3, in particular high current, is prevented from exciting mechanical vibrations of the individual laminations 3, since the bent, in particular upturned, folds 4 increase the rigidity of the individual laminations 3.

[0047] As shown in Figure 1, a fold 4 is formed and arranged on one side of each transverse slot.

[0048] Each transverse slot opens into the ambient air with its open end. At the other end, the respective transverse slot is closed, with the transverse slot being rounded, in particular circular, in this end region. The respective fold 4 preferably has a straight edge at the corresponding end because, during punching, a rounded area is punched out of the sheet metal to form the rounded end area of ​​the transverse slot. This area is preferably designed as a circular segment. Thus, after punching, the straight cut opens into the recess formed by removing the circular segment. The chord of the circular segment is aligned longitudinally, in particular before bending. The individual sheet 3 is then produced by bending the fold 4 during the punching and bending process.

[0049] In further embodiments according to the invention, the bending angle has a smaller value, in particular between 30° and 90°. In contrast to Figure 1, in the embodiment according to Figures 4, 5, and 6, a fold (21, 22) is bent, in particular bent upwards, on each slot on both sides, in particular in the longitudinal direction at the front and rear.

[0050] The longitudinally rear, i.e. first, fold 21 of the respective transverse slot 21 is bent in the same direction as the longitudinally front, i.e. second, fold 22.

[0051] In one embodiment, the bending angles are equal in magnitude for all first and second folds (21, 22), in particular at 90°. Alternatively, a bending angle between 30° and 90° can be used for all folds (21, 22), with the sheet thickness being adjusted accordingly.

[0052] In contrast to the design according to Figure 1, the cut ends in the recess designed as a circular segment in the middle, in particular symmetrically.

[0053] Since the folds 21 and 22 are narrower than the folds 4 of Figure 1, a high rigidity can be achieved with a corresponding sheet thickness and thus swinging can be suppressed.

[0054] In contrast to the embodiment according to Figure 4, the bending angles of the two folds 21 and 22 assigned to the respective transverse slot (1, 2) are different.

[0055] The front, i.e. first, fold 21 in the longitudinal direction is bent vertically in the embodiment according to Figure 4 and the rear, i.e. second, fold 22 in the longitudinal direction is designed and / or bent with a smaller bending angle.

[0056] In further embodiments according to the invention, the bending angle of the first fold 21 has an amount that is greater than the amount of the bending angle of the second fold 22.

[0057] In particular, the bending angle of the first fold 21 is between 60° and 90°, and the bending angle of the second fold 22 is between 30° and 60°. Alternatively, the bending angles of the front and rear folds (21, 22) are reversed, i.e., the bending angle of the first fold 21 is between 30° and 60°, and the bending angle of the second fold 22 is between 60° and 90°.

[0058] The braking resistor is preferably used in the intermediate circuit of a converter. The converter comprises a mains-powered rectifier whose DC voltage terminal is connected to the DC voltage terminal of an inverter, whose AC voltage terminal supplies an electric motor, particularly a three-phase motor.

[0059] To prevent a critical voltage value from being exceeded at the DC-side connection of the inverter during generator operation of the motor, a series circuit is provided parallel to the rectifier at the DC-side connection of the inverter. This series circuit includes at least the braking resistor and a controllable semiconductor switch connected in series with it.

[0060] Thus, electrical power from the intermediate circuit can be dissipated to the braking resistor.

[0061] The braking resistor is preferably used in the intermediate circuit of a converter that supplies an electric motor. The converter has a mains-fed rectifier that supplies an inverter. A series circuit containing the braking rectifier and a controllable semiconductor switch is connected in parallel to the DC voltage connection. The pulse-width modulated control of one or more semiconductor switches of the converter causes mechanical vibrations of the individual laminations.

[0062] In further embodiments of the invention, the individual sheets are not rectangular, but square.

[0063] 1 first cross slot 2 second cross slot

[0064] 3 single sheets

[0065] 4 fold

[0066] 21 first fold

[0067] 22 second fold

Claims

Patent claims:

1. Braking resistor comprising individual sheets, in particular wherein each individual sheet has a longitudinal length which is greater than a width of the individual sheet, in particular than a width of the individual sheet measured in the transverse direction, i.e. perpendicular to the longitudinal direction, in particular wherein the width is greater than the thickness of the individual sheet, characterized in that the respective individual sheet has first and second transverse slots arranged one behind the other in the longitudinal direction and spaced apart from each other, in particular wherein the first and second transverse slots are aligned parallel to each other and extend in the transverse direction, i.e. perpendicular to the longitudinal direction, wherein the first transverse slots project into the individual sheet from the right edge of the respective individual sheet as viewed in the longitudinal direction, wherein the second transverse slots project into the individual sheet from the left edge of the respective individual sheet as viewed in the longitudinal direction,wherein, viewed longitudinally, the first and second transverse slots are arranged one behind the other, alternating each other, in particular wherein the area covered in the transverse direction by the first transverse slots overlaps with the area covered by the second transverse slots, the transverse direction being perpendicular to the longitudinal direction.

2. Braking resistor according to claim 1, characterized in that the respective individual sheet has a longitudinally meandering area by means of the transverse slots.

3. Braking resistor according to one of the preceding claims, characterized in that the individual sheet is made of a flat steel sheet, in particular a rectangular flat steel sheet.

4. Braking resistor according to one of the preceding claims, characterized in that the individual sheet is manufactured as a stamped-bent part.

5. Braking resistor according to one of the preceding claims, characterized in that an edge region of the individual sheet metal bordering the respective transverse slot in the longitudinal direction at the front is bent by a first angle, in particular and is formed as a fold.

6. Braking resistor according to one of the preceding claims, characterized in that an edge region of the individual sheet metal which borders the respective transverse slot in the longitudinal direction at the rear is bent by a second angle amount, in particular and is formed as a fold.

7. Braking resistor according to one of the preceding claims, characterized in that the first angular magnitude is equal to the second angular magnitude, in particular such that the respective transverse slot is arranged centrally between the edge regions, or that the first angular magnitude differs from the second angular magnitude, in particular by at least 20°.

8. Braking resistor according to one of the preceding claims, characterized in that the first angle magnitude is at least 30° and at most 90°.

9. Braking resistor according to one of the preceding claims, characterized in that the second angle magnitude is at least 30° and at most 90°.

10. Braking resistor according to one of the preceding claims, characterized in that only on a single side of the respective transverse slot an edge area is bent, in particular as a fold.

11. Braking resistor according to one of the preceding claims, characterized in that the individual sheet is made of an iron material, cast iron material or sheet steel, in particular which is not a stainless steel sheet and / or that the individual sheet is made of an iron sheet or sheet steel which has a lower hardness than a stainless steel sheet, in particular geometrically uniform stainless steel sheet, and / or which has a greater magnetic permeability than a stainless steel sheet, in particular geometrically uniform stainless steel sheet.

12. Braking resistor according to one of the preceding claims, characterized in that each transverse slot opens into the environment at its first end, in particular open end, and is closed at its second end, in particular other end, wherein the transverse slot is rounded at this second end, in particular circularly rounded, in particular by punching out a circular segment from the single sheet, in particular such that a respective edge region of the single sheet bordering the respective transverse slot is bounded in a straight line at its edge facing the second end of the transverse slot, in particular as a result of the punched-out circular segment.

13. Drive system with braking resistor according to one of the preceding claims, characterized in that the drive system comprises an electric motor, in particular a three-phase motor, supplied by an inverter and a rectifier, wherein the DC-side connection of the rectifier is arranged in parallel to the DC-side connection of the inverter and in parallel to a series circuit which comprises the braking resistor and a controllable semiconductor switch, in particular a brake chopper, connected in series therewith.

14. Drive system according to one of the preceding claims, characterized in that the control signal of the controllable semiconductor switch, in particular brake chopper, is pulse width modulated, wherein the pulse width modulation frequency of the control signal is swept and / or modulated in a frequency band, in particular which has a first frequency value, in particular wherein the frequency band has a bandwidth of more than 10% of the frequency value, in particular and of less than 50% of the frequency value.

15. Drive system according to one of the preceding claims, characterized in that the inverter has controllable semiconductor switches, the respective control signal of which is pulse width modulated, wherein the pulse width modulation frequency of the respective control signal is swept and / or modulated in a frequency band, in particular which has a second frequency value, in particular wherein the frequency band has a bandwidth of more than 10% of the frequency value, in particular and of less than 50% of the frequency value.

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