EP4289235A1

EP4289235A1 - Explosion-proof housing

Info

Publication number: EP4289235A1
Application number: EP21839125.8A
Authority: EP
Inventors: Steffen Mueller
Original assignee: SMA Solar Technology AG
Current assignee: SMA Solar Technology AG
Priority date: 2021-02-03
Filing date: 2021-12-14
Publication date: 2023-12-13
Also published as: DE102021102511A1; WO2022167132A1; DE102021102511B4; US20230380088A1

Abstract

An explosion-proof housing (1) for a power electronics unit comprises a housing pan (2) and a cover (3) that closes the housing pan (2) via a seal, wherein the cover (3) and the housing pan (2) are pressed against each other only at two opposing sides, formed by edge regions of the cover (3) and the housing pan (2), via a plurality of fasteners (4) which can be released by rotation and engage in latching structures. The plurality of fasteners (4) are arranged in a central third (6.2) of the respective sides (6). The explosion-proof housing can be used in particular for a photovoltaic inverter.

Description

Explosion-proof housing

description

The invention relates to an explosion-proof housing and a photovoltaic inverter with such a housing.

In the case of power electronic devices, for example inverters for converting input power provided as direct current into output power provided as alternating current, components such as capacitors or switching modules can explode inside the housings of these devices, the potential explosion pressure of which increases continuously due to technological advances increasing power density. The danger that emanates from this was underestimated in the past. As a result, there are currently insufficient safety regulations for the design of casings for such devices, and incidents have been reported in which people who have been in the vicinity of the device have been injured by flying casing parts that have become detached from an explosion .

Depending on the area of application, a housing for such an electrical device must meet various normative requirements. In particular, the housing can shield the interior of the device from the environment and, for example, close it in a dustproof and watertight manner, so that the housing has an IP degree of protection in accordance with DIN EN 60529 and/or corresponds to one of the NEMA degrees of protection in accordance with NEMA Standard 250-2003. In addition, a housing must be able to pass further mechanical tests according to DIN and/or UL standards, for example with regard to compression, impact testing, external influences such as bird impact and/or special water jets.

The handling of high electrical power with an electrical device means that very high energy concentrations can accumulate in the housing of the device in a very short time. This can be desired, for example, to use capacitances or inductances for temporarily storing electrical energy as part of the dynamic conversion from one current form to another. However, undesirable energy concentrations can also occur, particularly in the event of a fault, incorrect operation, thermal overload or after aging processes. Electrical energy can be converted to a considerable extent into thermal and/or mechanical energy, for example by components heating up and bursting, or by flammable substances accumulating in a housing, for example due to (Electro-) chemical conversion processes, and are ignited by harmless electrical flashovers.

A considerable overpressure can therefore build up in the housing of the electrical device, which is closed per se. In the case of a power electronic converter which, for example, has one of the usual protection classes IP44 or IP65, the overpressure can also build up very quickly under unfavorable circumstances, for example within a few milliseconds. However, this must not result in the housing being destroyed in an unforeseeable manner, for example by it breaking in an uncontrolled manner and parts possibly being thrown out of the interior. In order to alleviate this problem, there are solutions for designing the housing in such a way that no housing parts come loose even in the event of an explosion. In order not to have to produce unnecessarily stable and thus material-intensive housing shapes, it seems advantageous to design the housing in such a way that a cover as the first housing component can detach in a controlled manner from a tray as the second housing component, forming an outlet gap, so that the explosion pressure can flow through the outlet gap can escape. The gaps that form in this way are often too small, so that, particularly in the case of strong explosions, the pressure cannot be reduced sufficiently quickly, and fastening elements, which are actually intended to keep the housing components connected to one another, fail.

Document DE 202020 101 874 U1 therefore proposes fastening the cover to the trough in the edge area with a large number of screws. Along one side, the edge area of the lid has a reinforcement that ensures that the lid is always held by the screws on the tray in this area, while on the other sides the screws are dimensioned so that they can be loosened in the event of an explosion can be loosened so that the lid can be opened like a hinge thanks to the reinforcement, but remains connected to the tub.

As an alternative, document DE 102019 122 812 A1 proposes fastening a housing cover with only a single, centrally arranged screw and exerting a sufficient sealing force on a circumferential seal arranged in the edge region of the cover. This central screw is dimensioned in such a way that it reliably holds the cover even in the event of an explosion. However, the lid can deform in the edge area in such a way that it lifts off the tray and thus forms an outlet gap for the explosion pressure. The disadvantage of this solution, however, is that the trough must have a centrally arranged, sufficiently mechanically stable abutment for the screw, which conflicts with the desire for a compact design with low weight and easy assembly. Document DE 766456 C discloses an explosion-proof housing with sealing flanges for electrical devices, with spring-loaded, rigid sealing means being provided between the housing and the cover in the sealing flanges.

The object of the present invention is therefore to provide a housing with a cover and a trough that allows a compact, lightweight design with easy access and in which housing components are reliably prevented from becoming detached inside the housing in the event of an explosion.

This object is achieved by a housing having the features of claim 1. Further features of preferred embodiments are indicated in the dependent claims.

According to one embodiment of the invention, an explosion-proof housing for a power electronic device comprises a housing trough and a cover closing the housing trough via a seal. The cover and the housing pan are pressed against each other exclusively on two opposite sides formed by the edge regions of the cover and the housing pan via a plurality of fasteners that can be released by rotation and engage in locking structures. The plurality of fixtures are located in a central third of the respective sides.

This creates two outer areas of the cover adjacent to the central third, which are not pressed against the seal by other fastening elements. Due to this arrangement of the fastenings, an explosion pressure can act effectively on these outer areas and there - to put it graphically - lever open the cover so that, compared to a conventional arrangement of fastenings, an outlet gap for the explosion pressure through a bending of the lid. The term central third is to be understood in such a way that the extent of this area along the opposite sides comprises a maximum of one third of the side length and is smaller than or equal to the extent of the two adjacent outer areas in order to achieve the leverage effect described and thus reliable bending of the cover in the event of an explosion to achieve the desired level.

A peripheral seal can be arranged between the edges of the side walls of the housing pan and the cover. A compressive force is applied to the seal by the fasteners via the cover. The compression force that can be achieved depends on the rigidity of the cover, which must be designed in such a way that the compression force is sufficient to make the housing lockable over the entire course of the seal in accordance with a specified protection class. As a result, a protection class of the Interior of the housing of at least IP45, preferably at least IP65 and / or Nema Type 4X are guaranteed. Due to the rigidity of the cover, it is possible and, in the context of the present invention, desirable to provide outer areas of the cover that are free of fasteners, in order to enable reliable formation of an outlet gap in the event of an explosion by deformation of the cover in these outer areas without that fastenings counteract this deformation.

In a preferred embodiment, exactly one fastening is arranged in the middle of each side, so that two outer areas of the same size are created. As a result, an outlet gap can form even at a particularly low explosion pressure. Alternatively, two attachments can be arranged on at least one side. In this way, an improved distribution of the contact pressure of the cover on the seal arranged between the cover and the housing trough can be achieved. A particularly advantageous compromise between an even distribution of the contact pressure between the cover and the housing trough on the one hand and the lowest possible limit value of the explosion pressure, from which an outlet gap can form between the cover and the housing trough, is achieved if exactly two fastenings are provided on both sides, each are located at approximately one-third and two-thirds of the side length, that is, at opposite ends of the central third of the respective sides.

The fastenings are preferably located on those sides of the housing which are longer than the sides on which there are no fastenings, in order to achieve a reduction in the limit value of the explosion pressure above which an outlet gap for the explosion pressure can form between the cover and the housing pan.

So that the fastenings are invisible from the front side of the housing, the fastenings can be arranged so that they are accessible from the housing pan side and engage in the locking structures arranged in or on the cover and preferably invisible when viewed from the side of the cover facing away from the housing pan.

In one embodiment, the fastenings are in the form of screws and the locking structures are in the form of threads, with the screws engaging through openings in the housing pan into the threads arranged in or on the cover. The threads can be designed directly as an integral part of the cover, or be part of a fixing bracket, which in turn is firmly connected to the cover, for example screwed. By using a fixing bracket, it can be achieved that the fixing bracket is deformed when the pressure inside the housing increases in such a way that In one area of the fastenings, a gap is formed between the housing pan and the cover through which the internal pressure can escape.

In a particularly advantageous embodiment, the fasteners are each designed as a quarter-turn fastener. Such a closure can be released in a particularly simple manner simply by rotating it by 90° using a suitable tool, but alternatively also by hand and without a tool, and includes a locking pin which engages in a locking structure designed as a retaining cam and by rotating it 90° a locked position to a free position in which the locking pin can be removed from the retaining cam. The retaining cam is preferably formed as part of a locating bracket attached to the lid at opposite ends and shaped at a central portion such that the retaining cam is spaced from the lid. The quarter-turn lock should be captively attached. The quarter-turn closure preferably has an optically recognizable indicator that indicates a locked state of the quarter-turn closure. The indicator can be formed, for example, by different colors or different symbols on the side faces of the quarter-turn fastener and indicate whether the quarter-turn fastener is in a locked position or in a free position.

The locking structure can be designed as a spring-loaded holding cam or as a stiff holding cam without springs, in which case a spring-loaded locking pin is used, which has a plate spring, for example, which provides a holding force in the locked position of the locking pin in the holding cam. Alternatively, the spring force can also be provided by the fixing bracket itself, without using a plate spring or another additional spring element.

In order to set the limit value of the explosion pressure above which an outlet gap can form between the cover and the housing trough, the cover can have structural elements which reduce the forces required for bending the cover along a bending line running between the fastenings. In particular, notches on the edge of the lid in the area of the fastenings, folds in the lid or a reduced thickness of the lid in the area of the bending line can be used to achieve this purpose. This makes it easier for the cover to bend or buckle along the bending line, so that in the event of an explosion an outlet gap is formed more quickly and to a greater extent.

In an advantageous embodiment of the invention, a photovoltaic inverter is equipped with an explosion-proof housing as described above, whereby an inverter is formed in which even in the event of an explosion inside the inverter, do not loosen any parts of the housing or at least loose parts of the housing remain in the interior and are not thrown into the environment.

The invention is illustrated below with the aid of figures, of which

1 shows a front view of a first embodiment of an explosion-proof housing according to the invention,

2 shows a rear view of a second embodiment of an explosion-proof housing according to the invention,

3 two detailed views of a fastening of a housing, and

Figure 4 shows a lid with structural elements to reduce the forces required to form an outlet gap.

1 shows a first embodiment according to the invention of an explosion-proof housing 1 of a power electronic device. The housing has a housing trough 2 inside which the device components are contained and which is closed by a cover 3 . A seal arranged between the cover 3 and the housing trough 2 prevents dirt and/or liquid from penetrating into the interior of the housing.

The lid 3 is pressed against the housing tray 2 by two fasteners 4, the fasteners 4 being centrally located on opposite sides 6 of the rectangular housing 1. Further fastening elements with which the cover 2 is held on the housing trough 3 are not provided in the embodiment shown in FIG. The sides on which the fasteners 4 are arranged are longer than the sides without fasteners.

The fastenings 4 can be formed by screws that are accessible from the cover side and engage in a thread of the housing trough 2 . However, the screws can also be accessible from the side of the housing trough 2 and can engage in threads arranged on or in the cover 3 . The latter variant also allows the fastening 4 to be designed so that it is invisible from the cover side.

2 shows a second embodiment according to the invention of an explosion-proof housing 1 of a power electronic device. Here, two fastenings 4 are arranged on at least one side 6 of the housing 1, which are located in the central third 6.2 of the length of the side 6. The adjacent two outer thirds 6.1 and 6.3 have no attachments 4. Along the face down opposite side 6 As shown side, a single, central attachment or also two attachments can be arranged at positions corresponding to the positions along the side 6.

As shown in the enlarged section of FIG. 2 , the fastening 4 is designed here as a quarter-turn fastener 8 which is accessible from the side of the housing trough 2 . This enables the cover 3 to be detached from the housing trough 2 with little effort, so that the interior of the housing is easily accessible, for example for repair purposes.

FIG. 3 shows a possible design of the individual attachments as a quarter-turn fastener in two perspective views. The upper representation of FIG. 3 shows a fixing bracket 7 which is screwed to the cover 3 at opposite ends. A retaining cam 5 for a quarter-turn fastener to be inserted therein is arranged in a central area of the fixing clip 7, which is designed at a distance from the cover 3 by appropriate embossing. The fixing bracket 7 is screwed to the cover 3 via elongated holes, which allow the distance between the central area of the fixing bracket 7 and the cover 3 to increase when there is a high tensile force on the retaining cams 5 . Furthermore, the cover 3 has a notch 10 directly next to the retaining cam 5, the effect of which will be discussed later.

In the lower representation of FIG. 3 , a quarter-turn fastener 8 arranged on the housing trough 2 is inserted into the retaining cam 5 of the fixing bracket 7 fastened to the cover 3 . The cover 3 is fastened to the housing trough 2 by locking the quarter-turn lock 8 in the retaining cam 5 .

4 shows an embodiment of a cover 2 of an explosion-proof housing according to the invention. The cover 3 has an embossing 11 along a direct connecting line between the two single fastenings 4, which can be introduced into the cover 3 as part of the shaping process. This embossing 11 as a structural element represents a targeted weakening of the cover 3 against a compressive force acting on the outer areas of the cover 3 from the inside of the housing when the cover 3 is in the installed state on the housing tray 2, whereby the cover under such a force action along a bending line essentially corresponding to the connecting line bends or buckles, and as a result an outlet gap between the cover 3 and the housing trough 2 forms even at a reduced explosion pressure.

Alternatively or additionally, a notch 10 in the lid edge in the area of intersection with the bending line and/or a reduced lid thickness in the area of the bending line can also be used as a structural element for a targeted weakening of the lid 3 against bending along the bending line. In the event that two fastenings are arranged on both opposite sides of the housing, and this results in two bending lines, each between the two fastenings assigned to the same outer area, structural elements can be provided for each bending line to weaken the cover against bending. The structural elements mentioned can be the same or different.

Reference List

1 housing

2 housing tray

3 lids

4 attachment

5 holding cams

6 page

6.1, 6.3 outer third

6.2 central third

7 fixing brackets

8 quarter turn clasp

9 indicator

10 notch

11 embossing

Claims

Patent Claims:

1. Explosion-proof housing (1) for a power electronic device, comprising a housing trough (2) and a cover (3) closing the housing trough (2) via a seal, the cover (3) and housing trough (2) each being exclusively on two opposite, sides formed by the edge areas of the cover (3) and the housing trough (2) are pressed against one another via a plurality of fasteners (4) which can be released by rotation and engage in locking structures, the plurality of fasteners (4) being in a central third (6.2) of the respective Pages (6) are arranged.

2. Housing (1) according to claim 1, wherein on each side (6) exactly one attachment (4) is arranged in the middle of the page.

3. Housing (1) according to claim 1, wherein on at least one side (6) two fasteners (4) are arranged.

4. Housing (1) according to one of the preceding claims, wherein the fastenings (4) are arranged detachably from the housing pan side, and in each case arranged in or on the cover (3) and facing away from the housing pan (2) side of the cover (3) Seen preferably engage invisible locking structure.

5. Housing (1) according to claim 4, wherein the locking structures are each arranged on a fixing bracket (7) attached to the cover (3), which deforms when the pressure inside the housing increases in such a way that even in a region of the attachments (4 ) a gap is created between the housing trough (2) and the cover (3) through which the increasing pressure can escape.

6. Housing (1) according to one of the preceding claims, wherein the fastenings (4) are designed as screws and the locking structures as threads, the screws through openings in the housing trough (2) and into the threads arranged in or on the cover (3). intervention.

7. Housing (1) according to any one of claims 1 to 5, wherein the fasteners (4) are each designed as a quarter turn lock (8).

8. Housing (1) according to claim 7, wherein the locking structure comprises a fixing bracket (7), the fixing bracket (7) being attached to the cover (3) at opposite ends is fastened and has a retaining cam (5) in a central area for arresting accommodation of the quarter-turn fastener (8). Housing (1) according to Claim 7 or 8, in which the quarter-turn lock (8) has an optically recognizable indicator (9) which indicates a locking state of the quarter-turn lock (8). A housing (1) as claimed in any preceding claim, wherein the housing (1) has two further sides which are shorter than the sides (6) in which the fasteners (4) are located. Housing (1) according to one of the preceding claims, wherein the cover (3) has a structural element which reduces a force required for bending the cover (3) along a bending line running between the fastenings (4), in particular a notch (10) at the edge of the lid, an embossing (11) on the lid or a reduced thickness of the lid in the area of the bending line. Photovoltaic inverter with a housing (1) according to one of the preceding claims.