Grounding element and electrical installation component having a grounding element

Abstract

The invention relates to a grounding element (10) for electrically grounding an electrical installation component, wherein the grounding element has a sheet steel component provided with a coating. According to the invention, the coating comprises an alloy.

Description

[0001] The invention relates to a grounding element according to the preamble of claim 1 and to an electrical installation component having such a grounding element according to claim 11 .

[0002] Electrical installation components, such as terminal boxes, lights, switches, distribution systems, control devices, etc., must be provided with grounding. The term "grounding" refers to the totality of all means and measures for grounding, i.e. for discharging electric current into the earth. "Grounding" is a conductive connection that facilitates potential equalization and thus minimizes potential differences. In electrical systems, such potential equalization or such grounding is required according to various standards in order to protect users from electric shock. The requirements for potential equalization in explosion-proof electrical systems are even more comprehensive. This ensures that no dangerous potential differences occur, which could lead to ignitable sparks, which in turn could trigger an explosion.

[0003] Known electrical installation components, such as junction boxes, terminal boxes, lamps, switch distribution systems, control devices, etc., have an insulating outer housing which serves on the one hand to protect the enclosed components and on the other hand to insulate the enclosed components towards the outside and thus prevent the user from touching the voltage components and receiving an electric shock. In order to achieve the required grounding, a grounding element is provided in the known systems and is electrically connected to a ground connection arranged outside the housing.

[0004] Known grounding elements are formed as grounding plates, which are arranged inside an insulating housing. Such grounding plates may be formed of brass, which offers the advantage that even after prolonged use in a corrosive environment, the corresponding grounding plate (due to being formed of brass) still has a sufficiently low contact resistance. Thus, even under the conditions of: four weeks at a temperature of 95° C. in an environment with 90% relative humidity and then two weeks at a temperature of 80° C., the contact resistance is still in the range below 5 megohms.

[0005] A disadvantage of such ground plates made of brass is the high costs, especially in the case of larger components, due to the expensive raw material.

[0006] Alternatively, galvanized steel sheets are therefore used as starting material, in particular using a galvanized surface. This offers the advantages of reduced production costs as well as a certain degree of corrosion resistance.

[0007] However, a disadvantage of using a zinc coating on steel sheets is that such a coating develops an unacceptable contact resistance over time in a corrosive environment. This is due to the partial conversion of zinc into zinc oxide, which is a semiconductor and therefore has a relatively low electrical conductivity.

[0008] The object of the present invention is to create a grounding element for electrically grounding an electrical installation component, wherein the grounding element has a sheet steel component provided with a coating which overcomes these disadvantages.

[0009] This object is achieved by a grounding element according to the characterizing portion of claim 1 and by an electrical installation component having such a grounding element according to claim 11 .

[0010] According to the invention, the coating of the grounding element consists of an alloy. This offers the advantage that the properties of the coating both with respect to corrosion resistance and with respect to electrical conductivity can be optimized. While in known grounding elements parts made entirely of brass or sheet steel parts coated with zinc are used, sheet steel parts are used in the grounding element according to the invention (and thus a cost reduction is achieved compared to brass parts). By choosing an alloy instead of using pure zinc, corrosion problems can be reduced.

[0011] Further preferred embodiments of the invention result from the dependent claims.

[0012] In a particularly preferred embodiment of the invention, the alloy comprises zinc and aluminum. The provision of zinc in the alloy exploits the good properties of this element as a corrosion protection for the base steel. The addition of aluminum leads to a significant increase in the electrical conductivity of zinc oxide, which can be formed in particular in corrosive environments. In this case, the electrical conductivity of zinc oxide is increased by a factor of up to 1000. This effect is caused by the properties of aluminum as a dopant for the semiconducting zinc oxide. This doping of zinc oxide with aluminum therefore substantially improves the electrical conductivity of zinc oxide. When coating steel sheet parts with such an alloy, the addition of aluminum to zinc also leads to an improvement in process stability.

[0013] Particular preference is given to coating grounding elements with alloys by hot-dip methods. Hot-dip is a coating method in which an electrical installation component or a corresponding semi-finished product for producing such an electrical installation component is immersed in a molten bath ("hot bath") of a zinc-aluminium alloy, so that after the workpiece has been removed from the molten bath, the liquid alloy forms a solid metal coating on the workpiece after cooling. The use of the hot-dip method represents a simple and cost-effective method for coating the particular alloy, since the two components (zinc and aluminium) only have to be contained in the melt in corresponding ratios.

[0014] Alternatively, the alloy may be applied by electroplating.

[0015] Due to the different surface structures of coatings applied by hot-dip or electroplating, it is possible to infer which method was used based on the finished grounding element. For example, coatings applied by hot-dip have a typical surface structure ("flowers"). In the case of electroplated coatings, these do not appear.

[0016] In a further grounding element according to the invention, the alloy has zinc as a basis, aluminum in a proportion of 40% to 70% by weight, and silicon in a proportion of 0% to 5% by weight. The term "basic" is understood to mean that apart from the components aluminum and silicon in the stated weight percentages and impurities (preferably in a proportion of less than 1% by weight, particularly preferably less than 0.1% or below 0.01%), the alloy consists essentially only of zinc.

[0017] As already explained, the addition of 40 to 70 wt. % aluminum serves to increase the conductivity of the zinc oxide. The addition of 0 to 5 wt. % silicon serves to further improve the corrosion resistance of the alloy.

[0018] In a further preferred embodiment of such an alloy with zinc as the basis, the alloy has a proportion of 50% by weight to 60% by weight of aluminum and a proportion of 1% by weight to 2% by weight of silicon.

[0019] Alternatively, according to the invention, an alloy can be used in which zinc is likewise provided as the basis, but in which aluminum is provided in a proportion of only 1% by weight to 10% by weight and in which magnesium (instead of silicon) is provided in a proportion of 1% by weight to 10% by weight. The low weight proportion of aluminum is sufficient to provide the desired doping of the zinc oxide. The addition of 1% by weight to 10% by weight of magnesium improves the corrosion resistance of the coating.

[0020] In addition to alloys based on zinc, alloys having 3% to 4% by weight of aluminum, in particular 3.5%, and 2% to 4% by weight of magnesium, in particular 3% by weight, are particularly preferred.

[0021] In a further preferred embodiment of the invention, the layer thickness of the coating is 2 to 25 µm, in particular 5 to 10 µm. The minimum layer thickness is 5 to 10 µm, which on the one hand offers the advantage that these minimum layer thicknesses permanently provide good corrosion protection for the steel sheet components when the alloy according to the invention is used, and on the other hand represents a cost-effective solution with regard to the material consumption of the coating.

[0022] In a particularly preferred embodiment of the invention, the contact resistance of the grounding element is less than 6 megohms. This provides the advantage that good grounding properties can be achieved and corresponding specifications and standards for use in potentially explosive environments can be maintained.

[0023] In the case of the electrical installation component according to the invention, it is designed in particular as a junction box, a terminal box, a lamp, a switch, a switch distribution system or a control device and has a housing and a grounding element according to one of the preceding embodiments.

[0024] By using the grounding element according to the invention, the electrical installation component is specifically designed for use in potentially explosive areas. This can be achieved by corresponding seals, which ensure airtight, waterproof, pressure-proof and / or dust-proof sealing of the housing.

[0025] In a preferred embodiment of the corresponding electrical installation component, the housing is designed as an external insulating housing. This provides the advantage that the housing protects the electrical components arranged inside the housing on the one hand. On the other hand, people are protected from contact with live parts and the live parts are shielded from potentially explosive environments. In this case, the grounding element is arranged inside the housing, but has an electrical connection to the ground connection of the electrical installation component arranged outside the housing. This advantageously ensures that the grounding element can be grounded for potential equalization.

[0026] Preferably, the connection between the grounding element and the external ground connection is designed so that the corresponding IP protection level of the insulating housing is maintained. This can be achieved by a corresponding seal, which ensures an airtight, waterproof, pressure-resistant and / or dust-proof seal for the conductive leads through the housing.

[0027] In a further preferred embodiment of the electrical installation component according to the invention, the insulating housing is electrostatically dissipative. This means that the housing can reduce any electrical charge in a controlled manner. For this purpose, it forms a resistor connected to ground.

[0028] To this end, the surface or shunt resistance of the housing is preferably higher than the surface or shunt resistance of a conductive housing, but lower than the shunt resistance of a completely insulating housing. 6 Ohm and 10 9 Surface or shunt resistors between ohms are particularly preferred.

[0029] The present invention is explained in more detail below by way of example with reference to the accompanying drawings.

[0030] As shown below:

[0031] Figure 1 The grounding element according to the present invention, and

[0032] Figure 2 Terminal box with such grounding element.

[0033] Figure 1 A perspective view of a ground element 10 is shown having sides 12, 14, 16 and 18 arranged at right angles on a base 20 of the ground element 10. The base 20 is substantially square or rectangular and the sides 12, 14, 16 and 18 extend away from the base 20 substantially all in the same direction.

[0034] According to the invention, the grounding element 10 formed as a steel sheet component has a coating containing an alloy. In this case, the coating of the grounding element 10 is an alloy with zinc as the main component (i.e. as the basis). The other components of the alloy are aluminum and silicon. The proportion of aluminum in the alloy is 55% by weight. At a proportion of 1.6% by weight of silicon, the remaining proportion of zinc (except for possibly smaller amounts (less than 1% by weight, preferably less than 0.1% or particularly preferably less than 0.01%) of impurities) is 43.4% by weight.

[0035] Alternatively, in addition to zinc as a basis in the alloy, a significantly smaller proportion of aluminum (eg 3.5% by weight) and a proportion of 3% by weight of magnesium (instead of silicon) may be provided, resulting in a zinc proportion of 93.5%.

[0036] In the alloy according to the invention, aluminum is used to dope the semiconducting zinc oxide which is formed after coating the grounding element 10 with the alloy, in particular under corrosive conditions, in order to thereby increase the conductivity of the zinc oxide. Silicon or magnesium is also added to improve the process stability and corrosion resistance of the alloy.

[0037] Figure 2 A terminal box 22 having a housing 24 is shown, in which a Figure 1 The housing 24 is designed as a synthetic material or plastic housing. In this case, the housing 24 preferably has a discharge capacity that prevents or at least reduces electrostatic charges.

[0038] Figure 2 The terminal box 22 is used for electrical connection of various components of the system and can accommodate, for example, a terminal strip (not shown in detail). The insulating housing 24 ensures that the live parts arranged in the interior of the housing 24 are not accessible or can only be accessed with tools. The components in the interior of the housing 24 are shielded from dust, water and explosive gases or environmental substances. Therefore, even if the terminal box 22 is used in a potentially explosive environment, sparks generated inside the housing 24 will not cause an explosion.

[0039] In order to be able to connect the grounding element 10 to an electrical ground or a corresponding potential outside the housing 24, a grounding connection 26 is arranged on the outside of the housing 24 and is electrically conductively connected to the grounding element 10 via a passage. In this case, the connection between the grounding element 10 arranged inside the insulating housing 24 and the grounding connection 26 arranged on the outside is designed such that a corresponding IP protection level of the insulating housing 24 is maintained. For example, in the case of a housing 24 that is protected against water according to a specific IP code, a corresponding watertight seal is provided. In potentially explosive atmospheres due to explosive gases or dust, a corresponding airtight or dustproof seal is provided.

[0040] The use according to the invention of a grounding element 10 in the form of a sheet steel component coated with an alloy of zinc and aluminum ensures that the grounding element 10 permanently meets the conductivity requirements even in aggressive and corrosive environments. On the other hand, the production costs can be kept low.

[0041] In this case, grounding elements 10 are particularly preferred in which the corresponding alloy is applied by hot-dip method or hot bath.

[0042] Reference numerals list

[0043] 10 Grounding element 12 side 14 side 16 side 18 side 20 Base Plate 22 Terminal box 24 case 26 Ground connection

Claims

1. An electrical installation component comprising a housing (24) and a grounding element (10), wherein the grounding element (10) comprises a steel sheet component provided with a coating, It is characterized in that The coating is an alloy; The alloy comprises one of the following: (1) Zinc as a base, 40 to 70 wt. % aluminum, 0 to 5 wt% silicon; as well as (2) Zinc as a base, 1 to 10 wt. % of aluminum, 1 to 10 wt % magnesium.

2. The electrical installation component according to claim 1, characterized in that: The alloy was applied by hot dipping.

3. The electrical installation component according to claim 1, characterized in that: The alloy is applied by electroplating.

4. The electrical installation component according to claim 1, characterized in that: The alloys include the following: Zinc as a base, 50 to 60 wt. % aluminum, 1 to 2 wt% silicon.

5. The electrical installation component according to claim 1, characterized in that: The alloys include the following: Zinc as a base, 3 to 4 wt. % of aluminum, 2 to 4 wt % magnesium.

6. Electrical installation component according to any one of the preceding claims, characterized in that The layer thickness of the coating is 2 µm to 25 µm.

7. The electrical installation component according to claim 6, characterized in that The layer thickness of the coating is 5 µm to 10 µm.

8. The electrical installation component according to any one of claims 1 to 5, characterized in that: The contact resistance of the grounding element (10) is less than 6 megohms.

9. The electrical installation component according to any one of claims 1 to 5, being a junction box, a terminal box (22), a lamp, a switch distribution system or a control device.

10. The electrical installation component according to claim 1, characterized in that The housing (24) is designed as an outer insulating housing (24) and the grounding element (10) is arranged inside the housing (24), wherein the grounding element (10) is electrically connected to a ground connection (26) of the electrical installation component and the ground connection (26) is arranged outside the housing (24).

11. Electrical installation component according to claim 10, wherein the connection between the grounding element (10) located inside the insulating housing (24) and the ground connection (26) located on the outside is designed such that the IP protection level of the insulating housing (24) is maintained.

12. The electrical installation component according to any one of claims 10 to 11, characterized in that The insulating housing (24) has static dissipative properties.

13. The electrical installation component according to claim 12, characterized in that The surface resistance of the insulating housing (24) is <10 9 ohm.

14. The electrical installation component according to claim 13, characterized in that The surface resistance of the insulating housing (24) is <10 9 Ohm and >10 6 ohm.

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