EP0782757B1 - Power limiting device for electric installation - Google Patents

Abstract

The power limiting device for an electric installation comprises, mounted in series in a common casing (16) between two terminals (20, 22) or connecting said casing (16) to an installation, first current limiting means (12) which are self-resetable and adapted to function when the intensity of the power current of this installation reaches a first threshold value corresponding to the maximum value of the current intensity authorized to circulate in said installation and second current switch-off means (14), which are not self-resetable, and having a response time shorter than that of the first current limiting means (12) and adapted to function when the instantaneous value of the power current reaches a second threshold value higher than the first threshold value.

Description

The present invention relates to a device of power limitation as defined in the preamble of claim 1, intended to limit the power delivered to an electrical installation.

Such a device, see for example EP-A-0 306 544, makes it possible to disconnect the installation. located downstream of it as soon as a predetermined intensity threshold is reached.

There are various prior art types of devices suitable for limiting power supplied to an electrical installation.

Such devices allow for example to offer a client an alternative solution to a suspension of electric power supply in case of non-payment of energy bills, by limiting its consumption.

For this purpose, a circuit breaker for limiting power set at low intensity can be installed in a home instead of a conventional circuit breaker. Such a power limiting circuit breaker is of a easy to use because it can be reset by the customer after tripping, but has the disadvantage to require complex assembly.

You can also use a fuse with a normal intensity determined according to the limitation chosen and placed in a location not accessible by the customer. Such a fuse is very easy to mount but has the disadvantage of causing a final cut of the power supply if the threshold is exceeded intensity.

The present invention aims to overcome the drawbacks cited by proposing a device for limiting power according to claim 1 making it possible to limit the consumption of a electrical installation and protect that installation against large and sudden increases in current.

It therefore relates to a limitation device power for electrical installation, which includes, mounted in series in a housing common between two connection terminals of this box to said installation, first means of limiting current, automatically resettable, suitable for intervene when the intensity of the supply current of said installation reaches a first value of threshold corresponding to the maximum value of the intensity of the current authorized to circulate in said installation and second non-resettable power cut means, having a lower response time than first means of current limitation and suitable for intervene when the instantaneous value of the current supply reaches a second upper threshold value at said first threshold value.

According to another characteristic of the invention, the first current limiting means include a thermal resistance switch.

Advantageously, the switch comprises, in an envelope of insulating material, a movable contact, a fixed contact and a related actuator heat exchange with thermal resistance and cooperating with the movable contact so as to move it between a closed current flow position in which the moving contact is based on the fixed contact and an open current limiting position.

According to another characteristic of the invention, the movable contact and the fixed contact respectively comprise a conductive strip and a contact tab, each fixed by one of their ends on a support and leaning on each other in the closed position by their free end, and the actuator comprises a snap action bimetal attached to its area median on a lug formed on the support.

Preferably, the switch includes first and second pins of conductive material passing through one end of the envelope and being respectively extended inside the envelope by the blade conductive and through the contact tab, the second pin being folded from said end towards a opposite end of the envelope and comprising a member mechanical connection and electrical connection with second power cut means, the first pin passing through an opening in a connection terminal of the housing with the installation.

Advantageously, the second cutting means current have a fuse fitted with two end caps connection, one of its end pieces being connected to the mechanical connection and electrical connection of the switch, the other end piece passing through an orifice made in a connection terminal of the box with the installation.

• la figure 1 est une vue en perspective éclatée d'un dispositif de limitation de puissance selon l'invention ;
• la figure 2 est une vue en coupe des premiers moyens de limitation de courant du dispositif représenté sur la figure 1, en position fermée de passage de courant; et
• la figure 3 représente une vue en coupe des premiers moyens de limitation de courant du dispositif représenté sur la figure 1, en position ouverte de limitation de courant.

Other characteristics and advantages of the invention will emerge from the following description, given by way of example, with reference to the appended drawings in which:

• Figure 1 is an exploded perspective view of a power limiting device according to the invention;
• Figure 2 is a sectional view of the first current limiting means of the device shown in Figure 1, in the closed current flow position; and
• 3 shows a sectional view of the first current limiting means of the device shown in Figure 1, in the open current limiting position.

In the figure, 1 a device has been represented. power limitation according to the invention, designated by the general reference 10.

The power limiting device 10 is intended to be installed on the power supply network upstream of an electrical installation, such as an installation house, so as to limit the power supplied to it.

This device 10 comprises first means of current limitation 12 and second breaking means current 14.

The first means 12 of current limitation and the second means 14 for cutting the current are arranged in series and placed in a common box 16, fictitiously broken in this figure 1, preferably having dimensions identical to those of a conventional fuse.

The housing 16 comprises a cylindrical body 18, in ceramic, surrounding the first limiting means 12 current and the second means 14 for cutting off current. The cylindrical body 18 is provided at each of its ends of two connection terminals 20 and 22 of the housing 16 with the installation, connected respectively to the first current limiting means 12 and to the second means 14 for cutting the current. Preferably, the terminals 20 and 22 are crimped hot on the body 18 of the case 16.

Advantageously, each connection terminal 20 and 22 of the housing 16 is provided with an axial orifice, respectively 24 and 26, formed in its end wall.

The first means 12 of current limitation have a substantially parallelepipedic envelope 28 in insulating material, such as a plastic material, in which is arranged a switch, which will be described with reference to Figures 2 and 3. The casing 28 is provided on one of its ends 30 of a first and a second pin 32.34 made of through conductive material the casing 28 and each connected to the switch.

The free end of the first pin 32 of the first means 12 for limiting current through the orifice 24 of the connection terminal 20 of the housing 16, and is soldered to the external face 36 of this terminal 20 so to make an electrical connection between this terminal 20 and the switch.

The free end of the second pin 34 is folded over and extends from the end 30 of the casing 28 towards an opposite end 38, shown dotted, at which this pin 34 includes a mechanical connection and connection member electric consisting of a cylindrical socket 40 intended to cooperate with the second cutting means 14 current.

The second means 14 of power cut have a fuse constituted in a known manner by a wire of alloy, not shown, enclosed in a cartridge 42 cylindrical ceramic and whose ends are connected to two connection end pieces 44 and 46, made of material conductor, closing each end of the cartridge 42.

Preferably, the fuse constituting the second means of cutting the current is a fuse of which the breaking capacity is above 20,000 amperes and whose nominal intensity is between 5 and 20 amps, preferably 10 amps.

The connection end piece 44 passes through the orifice 26, of the connection terminal 22 of the housing 16 so as to make an electrical connection between this terminal 22 of the box 16 and the fuse.

With reference to Figures 2 and 3, the first current limiting means 12 include a switch, with the general reference 48. The switch 48 has a movable contact, consisting of a conductive blade 50, a fixed contact, consisting of a lug contact 52 and an actuator constituted by a snap action bimetal 54, fixed on a support 56. This switch 48 is disposed in the casing 28, such so that the conductive strip 50 and the bimetallic strip 54 are in heat exchange relationship.

The conductive strip 50, of substantially shaped straight, is formed by a thermal resistance. It is fixed by one of its ends on the first pin 32 and on the support 56 via a copper rivet 58. The other end of the conductive strip 50 carries a contact pad and cooperates with a free end of the contact lug 52, the other of which end is fixed on the second pin 34 and on the support 56 via a second copper rivet 60.

In addition, the second pin 34 has a folded part 62 extending by a straight part 64 and by the socket 40 for receiving the end piece connection 46 of fuse 14.

Furthermore, the support 56 includes a lug 66 on which the bimetallic strip 54 is fixed by means of its middle part.

Bimetal 54 has an elongated profile shape substantially concave, whose concavity is turned towards the support 56 in the closed position for passage of current (figure 2), and whose concavity is turned towards the conductive strip 50 in the open limiting position current (Figure 3), in which both ends 68 and 70 of bimetallic strip 54 cooperate respectively with two projections 72 and 74 provided on the face of the conductive strip 50 placed opposite the bimetallic strip 54 so as to spread the free end of this blade 50 from the tab of contact 52 by deformation of the blade 50.

Preferably, the thermal resistance constituting the conductive strip 50 and the material of which the bimetal 54 are chosen so that the intensity switch 48 is located substantially between 3.5 and 8 amps, preferably 5 amps, so to limit the power supplied to approximately 1000 watts.

The power limiting device 10 described above is arranged upstream of the installation electric home instead of a fuse classic, preferably in an inaccessible location by the customer.

The current supplied by the network therefore flows in the first means 12 of current limitation and in the second means 14 for cutting the current.

Current flows through switch 48 and particular in the conductive strip 50, constituted by the thermal resistance, which heats up. Because of the heat exchange relationship between the blade 50 and the bimetallic strip 54, the heat energy emitted by the thermal resistance is transmitted to bimetal 54.

When the value of the intensity traversing the conductive strip 50 reaches a first threshold value, fixed for example as was mentioned above at 5 amps, after a response time due to the time lapse necessary for thermal resistance and bimetal 54 heats up, the switch 48 suddenly goes from its closed current flow position to its position open current interruption due to change abrupt concavity of the bimetallic strip 54. In position open, the concavity of the bimetallic strip 54 is turned towards the blade 50 and the ends 68 and 70 of the bimetallic strip 54 repel the projections 72 and 74 of the blade 50. Therefore, the blade 50 is deformed and its free end deviates from the tab contact 52 which causes a power outage.

The conductive strip 50 is no longer traversed by a current, the thermal resistance and the bimetallic strip 54 cool.

After a second response time due to the lapse of time required for thermal resistance and bimetallic strip 54 cool, bimetallic strip 54 returns to its initial position and its ends 68 and 70 deviate from the blade 50 which then returns to its initial position. The current therefore flows back into the device and the power supply to the electrical installation is again assured, the free end of the conductive strip 50 resting on the contact tab 52.

Of course, the response times required respectively for the transition from the closed position to the open position and open position to position closed are determined by choosing appropriately the materials constituting the thermal resistance and of the bimetallic strip.

For example, opening response times and at closing are equal and are approximately 1 min.

The fuse constituting the second means 14 of power cut known in a known way a time of very weak response and less than that of the switch 48.

So when a sudden rise in the instantaneous value of the current flowing in the device, above the intervention threshold of the first means of limitation and likely to damage the installation electric connected downstream, the alloy wire contained in the cartridge 42, is broken before opening of switch 48 due to the response time of this one, which causes a power cut, and protects the installation connected downstream and upstream of the device.

The device which has been described therefore makes it possible to limit the power supplied to an electrical installation at a predetermined threshold value, while allowing a exceeding this threshold for a very short time, but by protecting this installation against short-circuits.

In addition, this device is of a very mounting easy and can therefore easily be installed at a customer's, in the event that he has not paid his invoices energy, replacing a conventional fuse, or be easily replaced with a conventional fuse after the customer has paid their debts.

This is how the case in which are locked up the first current limiting means and the second power cut means may include a body in the shape of a rectangular parallelepiped provided at the level of each of its end faces with a knife electric contact.

This is also how the threshold values can be modified according to the power limitation and the desired protection.

Claims (4)

1. Power limiting device for electrical apparatus comprising, mounted in series in a common housing (16) between two terminals (20, 22) for connecting said housing (16) to said apparatus, first current limiting means (12) which can be reset automatically, which comprise a thermal resistor switch (48) and are adapted to cut in when the intensity of the supply current to said apparatus reaches a first threshold value corresponding to the maximum value of current intensity permitted to circulate in said apparatus, and second current cut-off means (14), which are not resettable, having a response time which is shorter than that of the first current limiting means (12) and which are adapted to cut in when the instantaneous value of the supply current reaches a second threshold value higher than said first threshold value, the switch (48) comprising, in a casing (28) of insulating material, a substantially rectilinear movable contact (50), a fixed contact lug (52) and a substantially concave, snap-action bimetallic strip (54) in heat exchange with the thermal resistor and cooperating with the movable contact (50) so as to move it between a closed position allowing current to pass, in which the movable contact (50) bears on the contact lug (52), and an open, current limiting position, characterised in that the switch (48) comprises first (32) and second (34) pins of conductive material passing through one end (30) of the casing (28) and being extended inside the casing (28) by the conductive strip (50) and by the contact lug (52), respectively, the second pin (34) being bent back from said end towards an opposite end of the casing (28) and comprising a means of mechanical linking and electrical connection (40) to said second current cut-off means (14), the first pin (32) passing through an opening (24) provided in a terminal (20) for connecting the housing (16) to the apparatus.
2. Power limiting device according to claim 1, characterised in that the second current cut-off means comprise a fuse (14) provided with two connectors (44, 46), one (46) of these connectors being connected to the mechanical linking and electrical connecting means (40) of the switch (48), the other connector (44) passing through an opening (26) provided in a terminal (22) for connecting the housing (16) to the apparatus.
3. Power limiting device according to claim 2, characterised in that the mechanical linking and electrical connecting means of the switch (48) comprises a socket (40) for receiving a connector (46) of the fuse (14).
4. Power limiting device according to any one of claims 1 to 3, characterised in that the first threshold value is between 3.5 ampères and 8 ampères, preferably 5 ampères, and the second threshold value is between 5 ampères and 20 amperes, preferably 10 ampères.

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