DE102012018456A1 - Bimetallic arrangement for e.g. main circuit breaker, has thermal bimetallic strip including strip portions that are controlled depending upon incident by overload current or residual current, for selective behavior of switching device - Google Patents

Abstract

The bimetallic arrangement has a thermal bimetallic strip (5) that includes different strip portions of different resistance values. The strip portions are controlled depending upon incident either by overload current or by residual current, for selective behavior of switching device. The ratio of tripping time for bimetallic strip with incident short circuit overload is 1:150.

Description

The invention relates to a bimetal arrangement for selective protective switching devices according to the preamble of claim 1.

Such bimetallic arrangements in generic protection switching devices are for example from the DE 10 2008 017 472 A1 or the EP 2330 611 A1 known.

These switchgear protect electrical lines against thermal overload and also ensure selective behavior to downstream circuit breakers in the event of a short circuit. The switching functions required for this purpose are controlled by two thermo-bimetals acting independently of one another on the switching mechanism, the bimetal arranged in the main circuit ensuring the overload protection, whereas the bypass circuit prescribing the selective behavior of the switching device.

Both bimetals differ fundamentally in their geometric dimensions and electrical values due to the different demands placed on them.

To meet these requirements was z. In DE 10 2011 008 078 A1 proposed to accomplish the overload protection by means of indirect heating, the selective behavior, however, by direct flow through the bimetallic strip. These known bimetallic arrangements are complicated both by the space required and by the production costs.

In addition, the thermostatic bimetals or their indirectly acting heating conductors, arranged in the main circuit in these versions are always flowed through by the operating current, so that the protective switching device quasi in stand-by mode permanently power loss produced by its own consumption.

This undesirable behavior leads to critical temperature increases in the distribution box and false shutdowns of the electrical systems.

To avoid this was in DE 10 2011 008 078 A1 proposed to equip the magnet system with two anchors, wherein an armature initiates the overload protection and only then, ie in disturbed operation, the bimetallic switch in the main circuit.

A disadvantage of this arrangement that the current must flow because of the required double break even in undisturbed operation on the additional contact and thereby generates unwanted power loss.

The invention is therefore an object of the invention to provide a bimetallic arrangement for selective circuit protection devices, which lowers the manufacturing costs in mass production by their simple structure and in combination with their training own consumption, the so-called power loss, the protection device against the specified requirements in the relevant regulations significantly reduced.

To solve this problem, the invention forms a bimetallic arrangement for selective protection switching devices according to the preamble of claim 1. Accordingly, according to the invention a bimetallic bimetal is used, which due to its geometrical dimensions ensures both different functions, namely the overload protection and the selective behavior of the protective switching device combined with a one-part triggering element. For this purpose, a bimetallic strip is required, which has a low electrical internal resistance in case of failure with flow through the thermal tripping current, however, has a significantly higher impedance in the event of a short circuit when flowing through with the limited by the selective resistance residual current.

These properties of the bimetallic strip are necessary to ensure the tripping function in the various types of accidents in the prescribed manner. In order to realize this, a ratio of the tripping times for the bimetal arrangement in the case of faults Short circuit: Overload in the order of magnitude of 1: 150 is a prerequisite. This is achieved by different dimensioning of both the flow-through lengths and the flow cross-sections in the sub-regions of the bimetallic strip.

According to the invention, therefore, a bimetallic strip is used which, with the same material thickness, offers greatly different resistance values for the throughflow with the different triggering currents depending on the malfunction due to the cutting of its area in the subregions.

The invention will be explained in more detail below with reference to its mode of operation in the circuit diagrams and the schematic representation of an embodiment, wherein components which are for the understanding of the inventive concept of minor importance and known, has been omitted.

The 1 shows the bimetallic strip with its fixed Fußpunktbefestigung and his via contact conductors galvanically connected to the associated switching contacts sections and his Influence on the latch of the switch lock in the event of a fault.

In 2 the different flow-through lengths and the associated flow cross-sections are shown simplified by the blank of the bimetallic surface.

The 3 shows the bimetallic arrangement in a selective circuit breaker conventional design.

In 4 is the development of the bimetallic arrangement in a selective circuit breaker with double anchor magnet system, as z. In DE 10 2011 008 078 A1 has been described.

As in 3 and 2 In the switched-on, operational state of the selective protective switching device, the current flows during normal operation of the terminal ( 1 ) over the connection ( 2 ) through the bimetallic base ( 3 ) along the line of action ( 4 ) through the low-resistance portion of the bimetal ( 5 ) over the connection ( 6 ) and contact ( 7 ) through the magnetic coil ( 8th ) to the terminal ( 9 ).

In the event of a fault in the event of overcurrent, the bimetal bends ( 5 ), as in 1 shown in the direction of the arrow and thereby releases by means of the pawl ( 10 ) the switch lock ( 11 ), which in turn causes the contacts ( 7 ) and ( 12 ) are opened, so that the faulty circuit is interrupted.

In the event of a fault in the event of a short circuit, the armature in the solenoid coil opens ( 8th ) via a ram along the line of action ( 13 ) suddenly the contact ( 7 ) and keeps this open, wherein the short-circuit current through the resulting arc in the quenching chamber ( 14 ) is severely limited.

The remaining, through the selective resistance ( 15 ) reduced residual current now flows along the line of action ( 16 ) by the higher-resistance portion of the bimetal ( 5 ) over the connection ( 17 ), the contact ( 12 ) by the selective resistance ( 15 ) and the magnetic coil ( 8th ) to the terminal ( 9 ).

The bimetal bends ( 5 ) very fast in the direction of the arrow and it would break as described above, the circuit, if not a downstream, the error source closer lying even faster switching circuit breaker would have taken over this task in the meantime. The protective switching device therefore operates selectively according to the specifications of the relevant regulations and remains switched on ready for operation.

In practice, it has been found that selective protective switching devices in which the operating current flows through the bimetal in the main circuit, are associated with deficiencies, which are due to this bimetallic arrangement. To z. For example, in continuous operation to keep the terminal heating of the switching device within limits, the working temperature of the bimetallic strip must be low, with the result that changing ambient temperatures at the installation - after all, the ambient temperature according to the relevant regulations between -25 ° C and + 55 ° C fluctuate - have a strong influence on the protective behavior of the switching device and thus on the safety of the electrical system.

By a development of the invention, as the combination of the bimetallic arrangement for selective protection switching devices with a double anchor magnet system in 4 shows, these disadvantages are avoided.

When switched on, during normal operation the current flows from the terminal ( 1 ) over the connection ( 22 ) and contact ( 18 ) through the magnetic coil ( 8th ) of the double anchor magnet system to the terminal ( 9 ).

In this case, the bimetallic arrangement is bridged low resistance, so that the power loss of the switching device is reduced in normal operation by more than half compared to the known designs.

In the event of a fault in the event of overload, the first armature of the magnet system is replaced by the overcurrent in the magnet coil ( 8th ), it opens via a ram along the line of action ( 13 ) the contact ( 18 ) and keeps it open.

The now over the Bimetallfußpunkt ( 3 ) and along the line of action ( 4 ) through the low-resistance portion of the bimetal ( 5 ) flowing conventional tripping current bends the bimetal ( 5 ) in the direction of the arrow and thereby releases by means of the pawl ( 10 ) the switch lock ( 11 ), whereby the contacts ( 7 ) 12 ) and ( 18 ) are opened and the faulty circuit is interrupted.

During this process, the contact opening first ( 18 ) Virtually de-energized, so that its contact resistance during the life of the switching device by burning does not change adversely.

In the event of a short circuit, the short-circuit current additionally causes the second armature to abruptly enter the magnet coil ( 8th ), it opens over the same ram along the line of action ( 13 ) first the contact ( 18 ) and immediately thereafter ( 7 ), while the current flowing through the resulting arc short-circuit current in the Extinguishing chamber ( 14 ) and strongly limited there. The remaining, through the selective resistance ( 15 ) reduced residual current now flows over the Bimetallfußpunkt ( 8th ) along the line of action ( 16 ) by the higher-resistance portion of the bimetal ( 5 ), via the connection ( 17 ), the contact ( 12 ) by the selective resistance ( 15 ) and the magnetic coil ( 8th ) to the terminal ( 9 ).

The mode of action of the short-delay cut-off initiated by this process has already become apparent in the description 3 it should be noted, however, that in an arrangement according to 3 the contact ( 7 ) must have both low contact resistance in normal operation, and high erosion resistance in case of short circuit, which is experience difficulties.

In the development according to the invention, as in 4 described, contact ( 7 ), however, only needed for the short circuit shutdown, it can therefore be designed for high erosion resistance, without having to take good conductivity into account.

The low-loss power line assumes in the innovation exclusively the normally-off switching contact ( 18 ).

With the bimetal arrangement for selective protection switching devices in combination with a double anchor magnet system as in DE 10 2011 008 78 A1 was disclosed, it is due to the advantages described also possible to produce generic low-loss switching devices with rated currents ≥ 100 A according to the requirements of the relevant regulations in a compact design with small external dimensions.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102008017472 A1 [0002]
• EP 2330611 A1 [0002]
• DE 102011008078 A1 [0005, 0008, 0018]
• DE 10201100878 A1 [0035]

Claims (3)

Bimetallic arrangement for selective protection switching devices, in particular main circuit breaker in generic, compact slim design, with the required different switch-off functions of the switching device, depending on which incident occurs independently of other influences on the switching mechanism interrupting the faulty circuit controlled characterized indicates that the triggering element of the switching device in the event of a fault, consisting of only one one-piece thermostatic bimetal ( 5 ), whose different sub-ranges with different resistance values depending on the incident are traversed by either the overload current or the limited residual current, which is decisive for the selective behavior of the switching device, so that tripping times for the bimetallic arrangement at the fault short circuit: overload in the ratio 1: 150 come about. Bimetal arrangement for selective protective switching devices according to claim 1, characterized in that both the bimetallic strip ( 5 ) with its partial areas as well as the quenching chamber ( 14 ) and the contacts ( 7 ) 12 ) as well as the selective resistance ( 15 ) are arranged in shunt, and that these components only in case of failure by interrupting the connection ( 22 ) by the over the line of action ( 13 ) from the plunger of the armature of the magnetic coil ( 8th ) open contact ( 18 ) are switched into the circuit, and that in addition to short-circuit the contact ( 7 ) from the second armature of the magnetic coil ( 8th ) over the line of action ( 13 ) is suddenly opened by the same pestle. Bimetal arrangement for selective protective switching devices according to the preceding claims, characterized in that by the blank of the bimetal ( 5 ) with the same material thickness in its individual subregions different flow cross-sections and flow-through lengths for the tripping current along its lines of action ( 4 ) and ( 16 ), whereby between the bimetallic base ( 3 ) and the compound ( 6 ) as well as the bimetallic base ( 3 ) and the compound ( 17 ) prevail in the cases of overload and short circuit very different bimetallic resistances.

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