LASTBANK

Description

[0001] The present invention relates to a load bank comprising a support frame and several load bank resistance modules attached to the support frame.

[0002] These types of load banks are also known as high-power resistors and typically feature heating elements in which electrical energy is converted into heat, which is then dissipated by natural or (fan-forced) convection to prevent overheating. Load banks have been around for many years and are used in a wide variety of applications, such as grounding resistors, railway resistors, braking resistors, or load banks for generator testing.

[0003] From the large body of disclosures, the document DE 10 2018 105 558 A1 is taken as an example, which describes a load bank of the type described at the beginning, in which tubular heating elements are grouped into modules, mounted standing on strips and contacted from below, in particular to minimize the heat load on the contact points.

[0004] CN 109 887 692 A describes a load bank with a large number of horizontally arranged, U-shaped tubular heating elements that can be individually mounted and replaced.

[0005] CN 102 446 610 A describes a load bank with tubular heating elements, each comprising a stainless steel tube, a resistance wire and an insulating filling.

[0006] Against this background, the present invention aims to provide a load bank with improved practicality, particularly with regard to efficiency, compactness, safety, durability, reliability and ease of maintenance.

[0007] This problem is solved by the load bank according to claim 1. The load bank comprises a support frame and several load bank resistance modules attached to the support frame, each load bank resistance module comprising an electrically non-conductive support plate and several heating resistors designed as tubular heating elements. The tubular heating elements each have two contact points, a heat dissipation tube, and a heating wire arranged in the heat dissipation tube, which is electrically insulated from the heat dissipation tube by an insulating material surrounding the heating wire and is electrically connected to the contact points. The heat dissipation tubes each have straight tube sections and at least one curved tube section. The tubular heating elements are each attached to one of the electrically non-conductive support plates.The support frame has a corresponding module opening for each load bank resistance module, dimensioned such that the heat dissipation tubes of a load bank resistance module can pass through the opening and the mounting plate of a load bank resistance module overlaps the corresponding module opening. The load bank resistance modules are attached to the support frame by means of their electrically non-conductive mounting plates, such that the support frame, together with the mounting plates, separates a heat dissipation zone from a contact zone. The contact points are located in the contact zone. The straight sections of the heat dissipation tubes are arranged horizontally within the heat dissipation zone, relative to their longitudinal extent.

[0008] Through the synergistic interplay of the features according to the invention, a load bank can be provided which has improved practical suitability in several respects.

[0009] Because each support plate overlaps its corresponding module opening in the support frame in both its longitudinal and / or transverse direction (so that the support plates cannot be passed through the module openings), the support plates, together with the support frame, form a continuous, wall-like barrier that separates the heat dissipation area from the contact area. In this way, the heat load emitted by the heat dissipation tubes can be focused in the heat dissipation area and, to a certain extent, shielded and kept away from the contact area. The temperature load in the contact area is therefore relatively low, which benefits the service life and reliability of the load bank.

[0010] By grouping several tubular heating elements into a single load bank resistance module (which shares a common support plate), faulty tubular heating elements can be easily and quickly removed and replaced (module-specifically), thus improving ease of maintenance. The fact that the straight sections of the heat dissipation pipes are arranged horizontally with respect to their longitudinal extent not only facilitates the insertion and removal of the heat dissipation pipes through the corresponding module opening during module installation and removal, but also promotes efficient heat dissipation. This horizontal arrangement of the straight sections of the heat dissipation pipes, perpendicular to the airflow direction, encourages the formation of turbulent flows, thereby improving heat dissipation.

[0011] The statement that the straight pipe sections of the heat dissipation pipes are arranged horizontally with respect to their longitudinal extent is to be understood in this context as meaning that the straight pipe sections are arranged perpendicular to the vertical airflow that develops in the waste heat area. Therefore, if the longitudinal extent of the straight pipe sections of the heat dissipation pipes forms an angle of less than 25° (in particular less than 20°) with the horizontal, this is to be understood as horizontal in the present sense.

[0012] The heat dissipation pipes each have straight (parallel) pipe sections and at least one curved (deflection) pipe section. This allows for a space-saving, meandering arrangement of the heat dissipation pipes. Advantageously, each meandering heat dissipation pipe extends in a plane, preferably horizontally oriented. Alternatively, the heat dissipation pipe can also extend in a vertical plane.

[0013] According to the invention, the heat dissipation tubes are not electrically connected to the (electrically grounded) support frame. This prevents a short circuit between the heating wire and the support frame, even if the insulation material loses its insulating properties and an electrical contact occurs between a heating wire and a heat dissipation tube. This improves operational reliability. The support frame can form part of the housing body.

[0014] Preferably, the load bank includes a fan suitable for generating a vertical airflow in the waste heat area of ​​the load bank. In this way, an airflow (preferably directed vertically upwards) with such a high flow velocity can be provided in the waste heat area that forced convection occurs, creating turbulent flow conditions at the surface of the heat dissipation pipes, which benefits heat dissipation and thus the efficiency of the load bank.

[0015] Furthermore, the load bank includes a heat shield plate, which is arranged parallel to the support plates in the heat dissipation area and has pipe openings through which the heat dissipation pipes can be routed. In this way, the contact area can be shielded even more effectively from heat stress.

[0016] According to a preferred embodiment of the load bank according to the invention, the support plates are made of mica, in particular micanite. Mica, and especially micanite, is an electrical insulator, relatively stable mechanically and thermally, easy to machine, and relatively inexpensive – and therefore particularly suitable as a support plate material.

[0017] Magnesium oxide can be used as an insulating material.

[0018] According to a further preferred embodiment, the tubular heating elements each have a flange and can be detachably fastened to one of the support plates by being able to insert the respective tubular heating element into at least one pipe opening in the support plate until it reaches the stop against the flange and detachably fasten it in this position. In this way, the tubular heating element can be easily attached to the support plate, and at the same time, it is ensured that—when the flange rests fully against the support plate—the straight pipe sections of the heat dissipation pipe of the associated tubular heating element have the desired horizontal orientation.

[0019] Particularly preferred are the tubular heating elements, which can be detachably fastened using at least one screwed nut. This type of fastening allows for both retightening of the connection (to compensate for settling effects that occur over time) and the easy replacement of individual faulty tubular heating elements. Both of these features contribute to the ease of maintenance of the load bank.

[0020] A seal, particularly a silicone seal, is preferably provided between the flanges and the support plates. This largely prevents ambient humidity from entering the insulating volume between the heating wire and the heat dissipation piping. The insulating material is typically highly hygroscopic and loses its electrically insulating properties as its moisture content increases. Therefore, effectively sealing the insulating material against ambient humidity enhances the reliability and longevity of the load bank.

[0021] Furthermore, the load bank includes electrically non-conductive guide plates, primarily made of micanite, with recesses through which the tubular heating elements can pass. These guide plates prevent long tubular heating elements from bending or sagging under their own weight and consequently contacting the load bank housing. This would adversely affect the housing, leading to unwanted heat transfer and, in the event of a short circuit between the heating wire and the heat dissipation tube, a ground fault between the heating wire and the housing. The guide plates thus improve the operational reliability and longevity of the load bank. They also allow the use of tubular heating elements with longer heat dissipation tubes.

[0022] Furthermore, the guide plates, which divide the waste heat area into several sub-chambers, support the formation of a homogeneous flow pattern within the waste heat area. This results in an airflow with even higher flow velocities in the vertical direction, which benefits heat transfer and thus the efficiency of the load bank.

[0023] An embodiment of the invention will now be explained in more detail with reference to the drawing. The drawing shows Fig. 1A - 1-leg load bench in a sectional view ( Fig. 1A ) and a front view ( Fig. 1B ), Fig. 2 the load bench according to the Figures 1A and 1B with mounting plate folded forward and a partially extended load resistance module in sectional view, Fig. 3A - 3C three load bank resistance modules together with a support plate in a top view ( Fig. 3A ), a side view ( Fig. 3B ) and a front view ( Fig. 3C), and Fig. 4A - 4B three load bank resistance modules together with a support plate in a perspective rear view ( Fig. 4A ) and a perspective front view ( Fig. 4B ).

[0024] First, with reference to the Figures 1A to 2 The general structure of the load bank will be explained before specific details are given with reference to the Figures 3A to 4B be carried out.

[0025] The Figures 1A and 1BFigure 1 shows a load bench 1 in a sectional view and a front view. The load bench 1 has a housing 3 resting on four feet 2, and a control cabinet 4 is attached to the front of the housing 3. This cabinet can be opened by means of two doors 5. A fan 7 mounted therein allows a vertically upward airflow (draft) to be created inside the housing 3 through an opening 6 on the underside. The housing 3 has a further opening 8 in its upper area through which the airflow can exit the housing 3.

[0026] The housing 3 contains several load bank resistance modules 9, each comprising a support plate 10 and several heating elements 11 attached to it, designed as tubular heating elements. When the heating elements of the load bank resistance modules 9 are energized during normal operation, the current is converted into heat, which is then dissipated from the load bank 1 by the airflow. For this purpose, the housing 3 includes an electrically conductive and grounded support frame 12, to which the load bank resistance modules 9 are attached via the non-conductive support plates 10.

[0027] The support plates 10 and the support frame 12 together form a barrier that separates a heat dissipation area 13 (which extends within the housing body 3) from a contacting area 14 (which extends within the control cabinet 4).

[0028] Inside the control cabinet 4 a mounting plate 15 is arranged, to which electrical and electronic components 16 are attached and which is rotatably mounted on the control cabinet base 18 by means of a joint 17.

[0029] As in Figure 2 As illustrated, the mounting plate 15 can be folded forward by rotating it around the hinge 17 when the control cabinet doors 5 are open. This makes the load resistor modules 9 accessible through the control cabinet 4 (i.e., from the front) and allows them to be removed from the housing 3 (towards the front), for example, for maintenance or repair purposes. Figure 2 The load module 9 shown is depicted in a state partially pulled out of the housing body 3.

[0030] The Figures 3A to 3C Figures 4A and 4B each show a section of the load bank 1 comprising three load bank resistance modules 9 together with the adjacent support frame 12, according to the Figures 1A to 2Each load bank resistance module 9 has an electrically non-conductive carrier plate 10 made of micanite and ten heating resistors designed as tubular heating elements 11. Each tubular heating element 11 has two contact points 19, a heat dissipation tube 20, and a heating wire arranged in the heat dissipation tube 20, which is electrically insulated from the heat dissipation tube 20 by an insulating material surrounding the heating wire and is electrically connected to the contact points 19. Each heat dissipation tube 20 has a meandering path formed by four straight tube sections 20a and three curved (semicircular) (deflection) tube sections 20b. As shown in the top view Figure 3A and the side view Figure 3B As can be seen, the meandering heat dissipation pipes 20 each extend in a horizontal plane.

[0031] Each tubular heating element 11 has two flanges 22 and is detachably attached to the support plate 10 by being inserted into pipe openings in the support plate 10 until it reaches the stop against the flanges 22 and screwed into place in this position using nuts 23 (which are located on the side of the support plate 10 opposite the flanges 22). A silicone seal is provided between each flange 22 and the support plate 10.

[0032] The support frame 12 has a corresponding module opening 24 for each load bank resistance module 9, dimensioned such that the heat dissipation pipes 20 of a load bank resistance module 9 can pass through the module opening 24 and the support plate 10 of a load bank resistance module 9 overlaps the corresponding module opening 24. The support plate 10 is larger in its longitudinal and transverse dimensions than the associated module opening 23. The load bank resistance modules 9 are attached to the support frame 12 by means of screws 25, which allow the electrically non-conductive support plates 10 of the load bank resistance modules 9 to be releasably fastened to the support frame 12.Also visible is a heat protection plate 26 arranged parallel to the support plates 10 with pipe openings 26a, as well as two electrically non-conductive guide plates 27 made of micanite with recesses 27a through which the tubular heating elements 11 can be passed. The straight pipe sections 20a of the heat dissipation pipes 20 are each arranged horizontally in their longitudinal direction (and form an angle of 0° with the horizontal).

[0033] The Figures 3A and 3B , 4A and 4B The figures show two load resistance modules 9 that are already screwed to the support frame 12, while in one load resistance module 9 the heat dissipation pipes 20 are being guided or threaded through the module opening 23, the heat shield plate 26 and the guide plates 27.

[0034] The support plates 10, which are screwed to the support frame 12, together form a barrier that separates a heat dissipation area 13 from a contacting area 14, with the contact points 19 being arranged in the contacting area 14.

Claims

1. Load bank (1) comprising a carrier frame (12) and a plurality of load bank resistor modules (9) fastened to the carrier frame (12), wherein - each load bank resistor module (9) comprises an electrically non-conductive carrier plate (10) and a plurality of heating resistors embodied as tubular heating elements (11), - the tubular heating elements (11) each have two contact points (19), a heat dissipation tube (20) and a heating wire arranged in the heat dissipation tube (20), which heating wire is electrically insulated from the heat dissipation tube (20) by an insulation material surrounding the heating wire and is electrically connected to the contact points (19), - the heat dissipation tubes (20) each have straight tube sections (20a) and at least one bent tube section (20b), - the tubular heating elements (11) are each fastened to one of the electrically non-conductive carrier plates (10), - the carrier frame (12) has, for each load bank resistance module (9), a corresponding module aperture (23), which is dimensioned in each case such that the heat dissipation tubes (20) of a load bank resistance module (9) can be guided through the module aperture (23) and the carrier plate (10) of a load bank resistance module (9) overlaps the corresponding module aperture (23), and - the load bank resistance modules (9) are each fastened to the carrier frame (12) by virtue of the electrically non-conductive carrier plates (10) of the load bank resistance modules (9) each being fastened to the carrier frame (12), such that - the carrier frame (12), together with the carrier plates (10), separates a waste heat region (13) from a contacting region (14), - the contact points (19) are arranged in the contacting region (14), - the straight tube sections (20a) of the heat dissipation tubes (20) are arranged lying in the waste heat region (13) with respect to their longitudinal extent, - the load bank (1) comprises a heat protection plate (26), which is arranged parallel to the carrier plates (10) in the waste heat region (13) and has tube apertures (26a), through which the heat dissipation tubes (20) can be guided, and - the load bank (1) comprises electrically non-conductive guide plates (27), in particular embodied from micanite, with recesses (27a), through which the tubular heating elements (11) can be guided.

2. Load bank (1) according to Claim 1, wherein the load bank (1) comprises a fan (7), which is suitable for generating a vertical air draft in the waste heat region (13) of the load bank (1).

3. Load bank (1) according to one of the preceding claims, wherein the carrier plates (10) are embodied from mica, in particular from micanite.

4. Load bank (1) according to one of the preceding claims, wherein the insulation material is magnesium oxide.

5. Load bank (1) according to one of the preceding claims, wherein the tube heating elements (11) each have a flange (22) and can be fastened releasably to one of the carrier plates (10) by virtue of the respective tube heating element (11) being able to be introduced into at least one tube aperture of the carrier plate (10) until it butts against the flange (22) and being able to be fastened releasably in this position.

6. Load bank (1) according to Claim 5, wherein the tube heating elements (11) can each be fastened releasably by means of at least one screwed nut.

7. Load bank (1) according to either of Claims 5 and 6, wherein a seal, in particular a silicone seal, is provided in each case between the flanges (22) and the carrier plates (10).