GB2326767A - Electric energy control device comprising a protection cover - Google Patents

Description

ELECTRIC ENERGY CONTROL DEVICE COMPRISING A PROTECTION COVER The present invention relates to an electric energy control device comprising a protection cover presenting at least one front side, two lateral walls, two longitudinal walls and two fixing lugs designed to slot into hooks of matching shape provided on said device.

For low-voltage electrical installations (380 V for example), electric energy control devices such as switches, fuse combination switches, changeover switches, the ratings of which range from a few dozen to several thousand amps, are mounted in electrical distribution cabinets.

One traditional embodiment, termed "wall mounting", involves mounting the devices side by side in a row, so that the incoming electric current passes through the connection lugs or terminals located on the devices in the upper part of the switch cabinet and the feeder current passes through the connection lugs or terminals located at the base of the devices in the lower part of the switch cabinet.

In this case, the main electric supply bars or cables, of which there are three for a three-phase distribution or four for a four-phase distribution, are arranged horizontally above the control devices to be supplied.

Another less common but technically advantageous embodiment involves mounting the devices one above the other in a column. In this case, the main electric supply bars or cables are arranged vertically in the switch cabinet and the control devices are arranged on the right and/or the left of these bars one above the other. The advantage of this configuration is that it is possible to connect another switch cabinet from above or from below. This configuration is common in some countries, particularly in Britain.

Nevertheless, and whatever the mounting arrangement, the current passing through the electric conductors and the control devices brings about a heat build-up due to the Joule effect. This heat build-up leads to a temperature rise in the whole switch cabinet and this thermal energy is removed either by natural heat convection by means of holes provided in the sides or on the top of the cabinet, or by forced air cooling by means of ventilation or air conditioning.

This heat build-up is particularly a drawback in the column configuration given that the lower device transmits calories to the one located above it and so on and so forth, thus causing sizeable temperature differences between the bottom and top of the switch cabinet. Furthermore, inside an electric energy control device, this temperature difference can reach 30 C between the lower pole and the upper pole.

This temperature difference is generally limited by a powerful forced ventilation which generates additional expense and is limited from a technical point of view primarily due to the laminar or turbulent flow which it generates and the space required by the fans.

In the case of fuse combination switches, this temperature difference prevents the fuses from operating properly. Indeed, given that a fuse is designed to blow at a certain temperature due to an energy surge brought about either by an electric short-circuit, or by a prolonged overcurrent in the downstream electric circuit, it is possible for the upper pole's fuse to blow before the lower pole's. The solution used so far by fuse combination switch manufacturers and switch cabinet designers is to mount the switching and control gear without any protection covers at the front. The advantage of this solution is that it allows excellent ventilation of the fuse cartridges mounted on the fuse combination switches. The major drawback with this solution is that there is no longer any protection on the devices which means that the live metallic parts might be touched when opening the cabinet and even when carrying out routine maintenance work. Furthermore, it is necessary for the safety of the personnel faced with an electric hazard, to fully shut off the switch cabinet when making changes inside the cabinet in order to ensure that all the metallic parts able to be touched are at zero potential. However, having to fully switch off the switch cabinet is detrimental to the service continuity of the equipment downstream controlled by this cabinet.

Another solution used to date by distribution switchboard designers is to downgrade the devices, i.e. to use for example a fuse combination switch which is overrated in relation to the nominal current of the circuit it is protecting. It goes without saying that that represents considerable additional expense.

The object of the present invention is to overcome these drawbacks by proposing an electric energy control device equipped with a protection cover which ensures efficient ventilation of said device to remove the calories and reduce as much as possible the temperature differences both inside the device and inside the switch cabinet, whilst meeting the standards on the protection of people (IP2) and the space and cost constraints.

This object is achieved by a device as described in the introduction and characterised in that the protection cover comprises openings provided at least in its front side and in that these openings form vents arranged to create an air circulation inside said cover by natural convection from bottom to top, when the device is positioned in a column.

In a preferred form of embodiment of the invention, the protection cover also comprises openings provided in its lateral walls, these openings forming vents arranged to create an air circulation inside said cover by natural convection from bottom to top, when the device is positioned in a row.

Preferably, the front side of the cover comprises at least two lateral openings located in its lower part and a central opening located in its upper part.

The front side of the cover offers the advantage of having a projecting central part, the central opening being located in this projecting central part.

The central opening can be made up of several channels delimited by inside partitions.

Preferably, the cover furthermore comprises openings provided in the lateral walls of the projecting central part.

In the preferred embodiment of the invention, the openings present dimensions designed to prevent fingers from being inserted in order to meet the current standards on the protection of people.

The device can have a single cover or, preferably, an assembly of juxtaposed unitary covers.

In this case, each unitary cover comprises locking means designed to lock the unitary cover located just below it in position. These locking means can comprise at least one retaining collar provided at the base and extending from the projecting central part, designed to slot into the lower unitary cover.

It is an advantage if the retaining collar is arranged to be placed in front of the edge of the upper longitudinal wall of said lower unitary cover.

The protection cover is preferably made by moulding or injecting a dielectric and shock resistant synthetic material.

The present invention and its advantages shall be disclosed in more detail in the following description of an example of embodiment, with reference to the attached drawings, in which - Figure 1 shows an electrical device with its protection cover according to the invention, in a column configuration, - Figure 2 shows the cover in Figure 1, with an illustration of the air circulation.

- Figure 3 shows the cover in Figure 2 rotated 90 , in the case of a row configuration, - Figure 4 shows the assembly of three unitary covers to form the cover in Figure 1, - Figure 5 is a cross section of two unitary covers assembled together, and - Figure 6 is a longitudinal section of a unitary cover.

With reference to Figure 1, the electric energy control device 1 illustrated corresponds to a front operated three-pole fuse combination switch whose operating lever has been removed, this device being oriented vertically to be mounted in a switch cabinet according to a column configuration. It comprises three identical disconnection modules 2, one for each phase conductor and one control module 3.

This device is connected electrically by means of connection lugs or terminals (not shown) provided on each disconnection module 2, upstream from the mains distribution busbar and downstream from the electrical equipment controlled (not shown).

This device also comprises a protection cover 10 arranged to cover all the disconnection modules 2 protecting the fuse cartridges and their base plate provided with clamps for fixing the cartridge, along with all the other live metallic parts, which are not visible, from being touched. This protection cover 10 is made by moulding or injecting a thermoplastic or duroplastic synthetic material, fulfilling electrical and mechanical requirements (insulation, flame resistant, shock resistance, etc.), like a polycarbonate for example. This cover 10 can either be made in a single piece or in unitary and identical pieces 11 for each disconnection module 2 or pole, these unitary pieces 11 being stacked and assembled to form said cover 10. The advantage of having individual unitary pieces lies in the standardisation of these pieces and the possibility of making covers simply and at a lower cost for various types of devices with a different number of poles by assembling an equivalent number of unitary pieces.

With reference to Figures 2 to 6 also, the unitary protection cover 11 presents a substantially rectangular shape and comprises a front side 12, two lateral walls 13 and two longitudinal walls 14. The lateral walls 13 are extended by a fastening lug 15 designed to slot into a hook 16 of matching shape provided on the lateral walls of the disconnection modules 2. The front side 12 comprises a projecting and slanting central part 17, this projecting part being closed laterally by two lateral walls 19.

This unitary cover 11 comprises several openings 1 8a to 1 8d forming vents designed to create an air circulation from bottom to top as Figure 2 and 3 show according to the assembly configuration of said devices. These openings are spread out over the front side 12, the lateral walls 13 and the projecting central part 17.

With reference in particular to Figure 2, the front side 12 comprises two lower lateral openings 18a arranged on either side of the projecting central part 17 forming the fresh air inlets along with an upper central opening 18b arranged in the projecting central part 17 forming the hot air outlet. The air inlets and outlet are symbolised by the arrows I and 0 respectively. The two lower lateral openings 18a are arranged level with the clamps for fixing the fuse cartridge which corresponds to the coldest areas on said fuse cartridge and the upper central opening 1 8b is arranged above the fuse cartridge corresponding to the hottest area in the module.

The air therefore circulates naturally by convection from bottom to top and individually for the purpose of cooling each disconnection module. The fresh air enters via the lower lateral openings 1 8a on each side of the fuse cartridge, circulates towards the middle and all around the fuse cartridge and is then evacuated naturally by the upper central opening 18b. The lateral walls 19 of the projecting central part 17 extend inside the cover to force the air circulation towards the clamps for fixing the fuse cartridge.

With reference in particular to Figure 3, the unitary cover 11 also comprises several parallel openings 18c, 18d, for example three of each, each time, in its lateral walls 13 and in the sides 19 of the projecting central part 17. Of course, this number is not limited. The cover 11 illustrated in this Figure corresponding to a row configuration, is rotated 90" in relation to the one in Figure 2. The openings 1 8c located in the lower part of the cover form the fresh air inlets and the openings 18d located in the upper part of the cover form the hot air outlets. The air inlets and outlets are symbolised by the arrows I and 0 respectively. The air also circulates naturally by convection from bottom to top and individually for the purpose of cooling each disconnection module. The fresh air enters via the lower openings 18c first of all, level with the lower clamp for fixing the fuse cartridge and afterwards, level with the base of the fuse cartridge, it circulates along and all around the fuse cartridge and is then evacuated naturally via the upper openings 18d, first of all, level with the top of the fuse cartridge and afterwards level with the upper clamp for fixing said fuse cartridge.

All the openings 18a to 18d are made by vents provided in the cover 11 with, for the upper central opening 18b, internal parallel partitions 20 forming air circulation channels. The size of all these openings 18a to 18d is determined to prevent fingers from being inserted so that no live metallic parts are accessible and can be touched without using a tool, in accordance with current standards on the protection of people providing for a protection index of 2 (IP2).

With reference now in particular to Figures 4 to 6, a protection cover 10 for a device with n disconnection modules or n poles is made by juxtaposing or assembling n identical unitary covers 11 on said device. The A arrows illustrate the direction in which these covers are mounted. The unitary covers 11 are designed to lock onto one another in order to achieve a rigid assembly. At the base of its projecting central part 17, each cover 11 comprises a retaining collar 21 which is obtained by the extension of the front wall. When the unitary covers 11 are superposed, the retaining collar 21 of the upper cover 11 is designed to be placed in front of the edge of the upper longitudinal wall 14 of the lower cover 11 located just underneath as shown in Figure 5. In this way, when the cover 11 is mounted on the upper disconnection module, it automatically locks the cover 11 already mounted on the lower disconnection module. It is obvious that it is necessary to follow the order for mounting the covers starting with the lowest disconnection module up to the highest, in a column configuration, or from left to right, or viceversa, in a row configuration. The last unitary cover 11 mounted on its disconnection module can be locked by means of a fitting which prevents the accidental disassembly of the unitary covers 11 forming the protection cover 10 of the electric energy control device 1 in said device's locked-in position.

The above description shows that the invention achieves all the intended objects, in particular with regard to: . protecting people in accordance with the protection index IP2, eliminating any danger when opening the switch cabinet, the possibility of carrying out work on just a part of the cabinet's electric circuits, good ventilation of the fuses and therefore proper operation of these fuses for the same short-circuit current or the same overcurrent whatever their position in the switch cabinet, restoring a homogenous temperature in the cabinet, removing oversized ventilation . locking the covers for each pole using a single lock located on the highest cover in the cabinet, doing away with downgrading the devices.

The present invention is not restricted to the example of embodiment described but can be extended to include any modification or alternative which is obvious for the expert.

The number and the shape of the openings are not limited to the example illustrated.

Furthermore, the overall shape of the protection cover may also vary according to the electrical device to be protected and ventilated.

Claims (13)

Claims

1. Electric energy control device (1) comprising a protection cover (10, 11) presenting at least one front side (12), two lateral walls (13), two longitudinal walls (14) and two fastening lugs (15) designed to slot into matching hooks (16) provided on said device, characterised in that the protection cover (10, 11) comprises openings (18a, 18b) provided at least in its front side (12) and in that these openings form vents designed to create an air circulation inside said cover by means of natural convection from bottom to top, when the device is positioned in a column.

2. Device according to claim 1, characterised in that the protection cover (10, 11) also comprises openings (18c, 18d) provided in its lateral walls (13) and in that these openings form vents designed to create an air circulation inside said cover by means of natural convection from bottom to top, when the device is positioned in a row.

3. Device according to claim 1, characterised in that the front side (12) of the cover comprises at least two lateral openings (18a) located in its lower part and one central opening (18b) located in its upper part.

4. Device according to claim 3, characterised in that the front side (12) of the cover comprises a projecting central part (17), the central opening (18b) being located in this projecting central part.

5. Device according to claim 4, characterised in that the central opening (18b) is formed by several channels delimited by internal partitions (20).

6. Device according to claims 2 and 4, characterised in that the cover (10, 11) further comprises openings (18c, 18d) provided in the lateral walls (19) of the projecting central part (17).

7. Device according to any of the previous claims, characterised in that the openings (18a-18d) present dimensions designed to prevent fingers from being inserted in order to meet the current standards on the protection of people.

8. Device according to any of the previous claims, characterised in that it comprises a single cover (10).

9. Device according to any of the claims from 1 to 7, characterised in that it comprises an assembly of juxtaposed unitary covers (11).

10. Device according to claim 9, characterised in that each unitary cover (11) comprises locking means (21, 14) designed to lock the unitary cover located just below it in position.

11. Device according to claim 10, characterised in that the locking means comprise at least one retaining collar (21) provided at the base of and extending from the projecting central part (17), designed to slot into the lower unitary cover (11).

12. Device according to claim 10, characterised in that the retaining collar (21) is designed to be placed in front of the edge of the upper longitudinal wall (14) of said lower unitary cover (11).

13. Device according to any of the previous claims, characterised in that the protection cover (10, 11) is made by moulding or injecting a dielectric, shock resistant synthetic material.