DE3013016A1 - RELEASE SYSTEM OF A SELF-SWITCH TO INTERRUPT A CIRCUIT - Google Patents

Abstract

1. Tripping system of an automatic circuit breaker for interrupting a current circuit, having at least one thermo-mechanical transducer (21; 31; 41; 51; 61) of an alloy with form memory, a short-circuit trip (12; 22) and a switching mechanism comprising a release gear which, in the event of an overcurrent, is tripped by the thermo-mechanical transducer (21; 31; 41; 51; 61) or short-circuit trip (12; 22) and interrupts the current circuit, characterised in that the thermo-mechanical transducer (21; 31; 41; 51; 61) is in thermal contact with a heat source, which is located in the current path of the automatic circuit breaker, for example the coil or the yoke of a magnetic short-circuit trip (12; 22), the arm of a dynamic tripping loop (17) or the section of a current-conducting path (20).

Description

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BROWN ₁ BOVERi & CIE AKTIENGESELLSCHAFT Mannheim April 2, 1980

ZFE / P4-La / Ht Mp.-No '. 532/80

"Release system of a self-switch to interrupt a circuit" . ^:

The invention relates to the release system of a circuit breaker to interrupt a circuit with at least one thermomechanical Converter, a short-circuit release and a switching mechanism with a latch, which is from the thermomechanical Converter or short-circuit release in the event of an overcurrent (overload or short-circuit current) is triggered and the circuit interrupts.

Trip systems of this type have become widespread and essentially serve to protect electrical lines and to these connected devices. In the course of the ongoing reinforcement of the networks, it is inevitable that due to the ever decreasing impedance in the supply network, possibly occurring short-circuit currents reach ever larger values.

1 300A1 / 0589

With automatic switches, especially with miniature circuit breakers that are intended for switching high short-circuit currents, is the realization of a sufficient short-circuit resistance of the thermomechanical converter, which occurs when the temperature increases experiences a mechanical deflection and creates a force that triggers the switch lock, difficult, because unfortunately the thermomechanical converter was usually in the circuit and destroyed by the high short-circuit currents could be.

In the German Offenlegungsschrift 15 88 513 was therefore suggested that the heating of the thermal overcurrent release (thermomechanical converter) connected to the coil of the Short-circuit release is connected in series and carries the full current, is short-circuited as soon as the switching contact is open and the arc has reached the quenching plates. With this solution, the short-circuit strength of the thermomechanical converter improved, but this solution has the disadvantage that with short-circuiting the thermomechanical Converter, the switch impedance decreases, thereby reducing the short-circuit current increases and thus the load on the stack of extinguishing sheets increases.

In order to create sufficient short-circuit strength, Tried often in the past to find a release element for the overload area that would perform the release function can take over without being dependent on the direct application of current, i.e. an element that is not in the circuit but is heated indirectly. 30th

There are already thermal bimetallic triggers with a heating conductor are wrapped, and are indirectly heated by this. These triggers are on the one hand only limited short-circuit proof and on the other hand have the disadvantage that by the Heating conductor an additional impedance is switched into the circuit.

130041/05 **

. The invention is therefore based on the object of a release system to interrupt a circuit of the type mentioned above; that has a high short-circuit strength has, avoids additional impedances in the release system and is as simple as possible.

According to the invention, this object is achieved in that the thermomechanical converter of the release system is in thermal contact with a heat source lying in the circuit of the circuit breaker

-JO mequelle is standing. Such a heat source lying in the current path can e.g. B. the coil or the yoke of a magnetic short-circuit release be. A leg of a dynamic release loop, which serves as a short-circuit release, can also be used as a heat source. or a section of a current path. The advantage against

■ J5 over known solutions results from the fact that for heating of the thermomechanical transducer no additional heating element is required because the heating of one in the trip system contained heat source can be exploited.

Advantageously, a thermomechanical converter can be used Find thermal bimetal or a shape memory alloy use. There are both shape memory alloys with disposable as also suitable with two-way effect. Care must be taken when using a shape memory alloy with a one-way effect that after the switching function has been triggered and the thermomechanical converter has cooled down again, it is reset the trigger is plastically deformed again. When heated again, the alloy then regains its original shape back and triggers the switching function again.

It is advantageous to clamp the thermomechanical transducer on one side so that its free end is exposed when the temperature increases deflect and trigger the switching function.

130041/0569

-: ν 3013018

According to the invention, the thermomechanical transducers preloaded by an applied force will. If the thermomechanical transducer is made of a shape memory alloy, the preload can reduce the trigger temperature, at which the recovery of the plastically deformed alloy begins.

It is an advantage to take care that the thermomechanical Converter until a specified temperature is reached

remains in its starting position in order to avoid that at before-10

early deflection of the thermomechanical converter, which is about can be proportional to the temperature increase (especially when using thermal bimetals), the thermal contact between Heat source and thermomechanical converter decreases, which increases the time constant for tripping and an unde--

can result in a defined heat transfer function.

An essential feature of the invention is the result thermomechanical transducer at its free end by a force that can be triggered by the inherent force of the thermomechanical transducer

memory held in its original position until the temperature-related deflecting force of the thermomechanical Converter exceeds the retention force of the energy store. the Fixation of the thermomechanical converter to its original position and the sudden release after reaching a temperature

threshold, ensures proper triggering of the switching process. It is thereby z. B. the "rattling" of the plunger release avoided.

According to the invention, the energy storage device can be a permanent magnet or

■ "

be a spring accumulator, in particular the free. End of one-sided clamped thermomechanical transducer prevents its deflection until the thermally induced deflecting force of the thermomechanical converter, the retention force of the Energy accumulator exceeds.

130041/0569

The thermomechanical converter can advantageously be designed as a strip-shaped part which, in order to achieve good thermal contact with the heat source in the current path of the circuit breaker (e.g. coil or yoke of a magnetic short-circuit release, the leg of a dynamic release loop or the section of a Scfcrom track ) hugs. For example, the strip-shaped part can be designed as a leaf spring in order to load the energy storage device or the release mechanism with a pretension to determine the release force. When using a shape memory alloy as a thermomechanical converter, the design as a leaf spring can also be used to determine the transition temperature between the martensitic and austenitic phases, i.e. to determine the temperature,

in which the alloy deflects abruptly, serve. 15th

As a result of a further refinement, the thermomechanical Form the transducer as a spiral, which is preferably arranged coaxially to the heat source. The special advantage can be seen here in the fact that the spiral is

Increase and the resulting deflection does not stand out from the heat source, as can happen with a strip-shaped part. Thus ^one is fully made in designing a spiral of thermal contact even with successful deflection. The spiral can be designed as a pretensioned spring, the pretensioning being able to take place axially or radially. It can be designed so that the temperature-related deflecting force acts either in the direction of the spiral axis or radially (torsional force). If the magnetic short-circuit release is used as the heat source, the spiral can either be externally via the magnetic

trip coil or the yoke can be placed, or in some cases also be placed inside the magnetic trip coil.

Another feature of the invention results in adjustment of a given tripping current the size and shape the heat-exchanging surfaces of the heat source fz. B. Coil or yoke of a magnetic short-circuit release, leg of a

130041/0589

- _w - ·

■ Al

dynamic tripping loop or section of a current path) and the thermomechanical converter designed so that a tripping current assigned heat transfer between short-circuit tripping. water and thermomechanical converter.

According to the invention, to set a predetermined tripping current an intermediate layer of selected ones between the heat-exchanging surfaces of the heat source and the thermomechanical transducer Thermal conductivity, thickness and contact area inserted will. Such an intermediate layer can influence both the tripping current and the tripping time constant. Is z. Legs; Intermediate layer of plastic film inserted between the short-circuit release and the thermomechanical converter, so speaks the release system only comes on after a larger time constant and with a larger current load. When choosing an intermediate copper layer both values decrease '. It is therefore possible to vary the characteristics of a release system within certain limits simply by exchanging the intermediate layer. It can be for different Circuit breaker ratings a single thermomechanical converter can be used when the trip coil is on a certain power is dimensioned and the same heat transfer is ensured through the intermediate layer.

A major advantage of the invention is to be seen in the fact that the thermomechanical converter through the in the current path the heat source lying on the circuit breaker can only be heated indirectly. This has unlimited short-circuit strength of the thermomechanical converter.

However, it is also possible where this is appropriate for the design Tripping characteristic is necessary to switch the thermomechanical converter at least partially into the circuit. Here, the thermomechanical converter z. B. arranged both in parallel and in series with the short-circuit release will. When connected in series, the short-circuit strength is increased of the thermomechanical converter, this is preferably bridged by a parallel resistor.

130041/0580

'■ Hl ·

With the aid of the drawing, in which several exemplary embodiments of the invention are shown, the invention and other advantageous ones are intended Refinements and improvements and further advantages are explained and described in more detail.

Show it

Figures 1 to 10 each show a basic circuit of the release system,

11, 13, 15 each show a schematic representation of the

Au & löseelemen.ts,

12, 14, 16 each a graphical representation of the deflection of the temperature-sensitive

Element as a function of temperature,

FIG. 1 shows the basic circuit of a release system according to the prior art. Such a release system is for example ^ _n in the auto switch, which is described in the German Offenlegungsschrift 15 88 513, respectively. In the release system, the following components are connected in series between terminals 14 and 15: A thermomechanical converter 11, which according to the prior art usually consists of a thermal

bimetal, a magnetic short-circuit release 12 and 25

a switching contact point 13, which in a known manner from a stationary contact piece 28 and a movable contact piece 27 exists. The switching contact point 13, which is shown in the open state, is, as indicated by the dashed lines of action. _. interpret, if a short-circuit or overload current occurs,

opened neither by the magnetic short-circuit release 12 or by a switch lock 16, the switch lock 16 in turn is triggered either by the thermomechanical converter 11 or by the magnetic short-circuit release 12.

1 30 04 1/0 569

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Figure 2 differs from Figure 1 only in that that here the thermomechanical converter 11 is not in series with the magnetic short-circuit release 12, as in the figure, but is connected in parallel.

In the basic circuit diagram of a release system shown in FIG. 3 According to the invention, only the magnetic short-circuit release 12 and 12 is located between the connection terminals 14 and 15 the switching contact point 13. The strip-shaped thermomechanical converter 21 clamped on one side is in direct heat • contact with the magnetic short-circuit release 12. Current does not flow through it, but when the temperature rises of the magnetic short-circuit release 12 through which the electric current flows, is heated by this. As soon as there is a short-circuit or overload current the temperature of the thermomechanical converter 21 has a response value exceeds, the thermomechanical converter 21 deflects and acts on a switch lock 16, which in turn the switch contact point 13 opens and interrupts the flow of current. It is also here, as provided in Figures 1 and 2, that the magnetic short-circuit release 12 both directly and via the switch lock 16 to the switch contact point 13 acts.

FIG. 4 and FIG. 5 represent basic circuits of the release system corresponding to Figure 3, except that here the heat source for heating the thermomechanical converter clamped on one side 21 is not, as in Figure 3, a magnetic short-circuit release coil, but, as shown in Figure 4, a dynamic release 17 or, as shown in FIG. 5, a section of a current path 20. The dynamic triggering loop shown in FIG 17 consists of a fixed leg 18 and a free leg 19, which repel each other in the event of high current surges. As a result of the repulsive forces, the free leg 19 deflected and causes the switch contact point 13 to open either via the switch lock 16 or directly.

130041/056 «

The basic circuit diagram of a release system shown in FIG According to the invention, it differs only in the design of the thermomechanical transducer 31 clamped in on one side Figure 4. The thermomechanical ^ converter 31 is not strip-shaped here, but as a coil spring made from a shape memory alloy which is placed coaxially around the fixed leg of the dynamic trigger 17. The free end of the thermomechanical transducer 31 is heated depending on the current flowing through the dynamic trigger 17 and ■ jQ is deflected when a trigger temperature is exceeded and acts on a switch lock 16. The deflection of the thermomechanical converter 31 takes place depending on its design in axial or radial direction.

In the basic circuit diagrams shown in FIGS. 7, 8 and 9 of a release system according to the invention, a thermomechanical transducer 41, 51, 61 clamped on one side is spiral-shaped wound around the coil of a magnetic short-circuit release 12. The deflection when a release temperature is exceeded

2Q door takes place axially in Figure 7, in which the spiral contracts, in Figure 8 also axially, in which the spiral stretches and in Figure 9 radially, in which the. ¹ spiral twisted (torsion). By applying a bias, the thermomechanical transducers of Figures 7 to 9 can be used as a compression spring 41, tension

"G spring 51 and can be designed as a torsion spring 61. The arrows A, B and C indicate in which direction the thermomechanical Transducers 31, 41, 51 deformed when the response temperature is exceeded in order to then act on the switching mechanism 16.

OQ In the indirect heating of the thermomechanical converter, as shown in the switching arrangement of the release system in Figure 3 to Figure 9, the thermomechanical converter is not flowed through by the current. On the one hand, this results in unlimited short-circuit strength of the thermomechanical

gg converter, on the other hand, the tripping system is not activated by the Resistance of a series-connected thermomechanical transducer, as shown in Figure 1, loaded.

130041/0589

-AH

When designing a release system in which the heating e.g. the magnetic short-circuit release by the flowing through If the current is insufficient to trigger the thermomechanical converter, a circuit arrangement can be used as shown in FIG. The thermomechanical converter 21 is here parallel to the magnetic short-circuit release 12 arranged. The clamped end of the thermomechanical transducer 21 is connected to the terminal 14 and the The free end of the thermomechanical converter 21 is connected to the movable contact piece 2 7 via a flexible line 33 Switching contact point 13 connected. Part of the current entering the trip system flows through the Ln thermal contact to the magnetic short-circuit release 12 standing thermomechanical converter 21, the other part flows through the magnetic short-circuit release 12th

FIG. 11 shows a schematic section through a magnetic short-circuit release 22 which has a magnetic core 23, a magnet armature 24, to which a release pin 25 is attached and a magnetic trip coil 26 contains. In the event of an overload or short-circuit current, the trigger pin 25 can be Lift movable contact piece 2 7 from a fixed contact piece 28, which leads to an interruption of the current flow. on a rectangular thermomechanical transducer 21 is attached to the end face of the magnetic short-circuit release 22, whose legs, which run parallel to the axis of the short-circuit release, bend freely when the temperature increases able (dashed line), where he has a pawl 29 and a switch lock, not shown, which on the movable = Contact piece 27 acts, causing a power interruption.

In FIG. 11, the thermomechanical converter 21 is a thermal bimetallic strip clamped on one side, which is according to FIG. 12 up to a trigger temperature T approximately

el proportional to its heating, which depends on the current load of the Short-circuit release 22 depends, deflects. At the release temperature

130041/0569

T, the deflection S reaches a tripping stroke S which, via the pawl 29, triggers the switch lock 16 and thus opens the contact point 13.

Due to the proportionality between the deflection S and the temperature T of the thermomechanical converter 21 in the lower region of the The curve takes with increasing temperature the thermal contact between the magnetic short-circuit release 22 and the thermomechanical Converter 21. This can have a detrimental effect on the functioning of the release system.

A release system is therefore shown in FIG. 13 which is similar to that of FIG. In Figure 13, however, the free end engages of the thermomechanical converter 21 clamped on one side in the groove of a shaft 30. The shaft 30 is at its rotation Hindered in the direction of the arrow by an energy storage device, not shown, until the deflection force of the thermomechanical Converter 21 exceeds a value corresponding to the tripping current. In this case, the shaft 30 is the deflection of the thermomechanical converter 21 free, which triggered the switch lock 16 via the pawl 29 and interrupted the flow of current will.

FIG. 14 shows the release characteristics for a release system shown in FIG. 13. The deflection S of the thermomechanical Converter 21, e.g. B. Thermobimetalls takes place at a Release temperature T jump. This ensures that

that good thermal contact between the magnetic Short-circuit release 22 and the thermomechanical converter 21 is given until it is triggered.

Another exemplary embodiment is shown in FIG. It is similar to the one described in FIG. 11, only that here the Thermal bimetallic strip was replaced by a strip made of a shape memory alloy. The shape memory alloy strip has the advantage over a thermal bimetallic strip

130041/0569

that it deflects abruptly at a certain temperature even if the free end is not tied. A corresponding The deflection characteristic was shown in FIG.

In a further embodiment, which is not shown, in a column S between the magnetic short-circuit release 22 and the thermomechanical converter 21 an intermediate layer for setting a specific heat transfer value inserted. This intermediate layer can, for. B. a copper interlayer (small time constant for the release system because of the high conductivity of the intermediate layer) or a plastic film (large time constant for the release system because of low conductivity of the intermediate layer)

130041/058 $

Claims (19)

Expectations 1.1 Trigger system of a self-switch to interrupt a circuit with at least one thermomechanical converter, a short-circuit release and a switching mechanism with a latch, which is triggered by the thermomechanical converter or short-circuit release in the event of an overcurrent (overload or short-circuit current) and interrupts the circuit, characterized in this way that the thermomechanical converter (21, 31, 41, 51, 61) is in thermal contact with a in the current path of the. Self-switch lying heat source z. B. the coil or the yoke of a magnetic short-circuit release (12, 22), the leg of a dynamic release loop (17) or the section of a current path (20). 2. Trigger system according to claim 1, characterized in that the thermomechanical converter (21, 31, 41, 51, 61) from Thermobimetal is made. 3. Trip system according to claim 1, characterized in that the thermomechanical converter (21, 31, 41, 51, 61) consists of a Shape memory alloy is made. 4. Trigger system according to one of claims 1 to 3, characterized in that the thermomechanical converter (21, 31, 41, 51, 61) is clamped on one side. 1 3 "0 0 4 1/0 5 e 0 5. Trigger system according to one of claims 1 to 4, characterized characterized in that the thermo-mechanical converter (21, 31, 41, 51, 61) is biased. 6. Trigger system according to one of claims 1 to 5, characterized characterized in that the thermomechanical converter (21, 31, 41, 51, 61) remains in its starting position until a specified temperature is reached. 7. Trip system according to one of claims 5 or 6, characterized in that the thermomechanical converter (21, 31, 41, 51, 61) at its free end by one triggered by the inherent force of the thermomechanical transducer (21, 31, 41, 51, 61) Energy storage is held in its original position until the temperature-related deflecting force of the thermomechanical Converter (21, 31, 41, 51, 61) exceeds the retaining force of the energy store. 8. Release system according to claim 7, characterized in that the energy storage device is a permanent magnet. 9. Release system according to claim 7, characterized in that the energy store is a spring accumulator. 10. Aulösesystem according to one of claims 1 to 9, characterized in that the thermomechanical transducer (21) as a strip-shaped Part, e.g. B. is designed as a leaf spring. 11. Trigger system according to one of claims 1 to 9, characterized characterized in that the thermomechanical converter (31, 41, 51, 61) is designed as a spiral, which is preferably coaxial with the Heat source, e.g. B. to the coil or the yoke of the magnetic short-circuit release (12, 2 2,), to the leg of a dynamic release loop (17) or to the section of a current path (20) is arranged. . 130041/0589 12. Release system according to claim 11, characterized in that that the spiral deflects axially when the temperature increases. 13. Trigger system according to claim 11, characterized in that the spiral deforms radially when the temperature increases (Torsion). 14. Trigger system according to one of claims 1 to 13, characterized in that for setting a predetermined Tripping current the size and shape of the heat-exchanging surfaces of the heat source and the thermomechanical transducer (21, 31, 41, 51, 61) are designed so that a heat transfer associated with the tripping current between the heat source and the thermomechanical . Converter (21, 31, 41, 51, 61) consists. 15. Release system according to one of claims 1 to 14, characterized in that zuar · setting a predetermined Tripping current between the heat exchanging surfaces of the heat source and the thermomechanical converter (21, 31, 41, 51, 61) an intermediate layer of selected thermal conductivity, thickness and contact surface is inserted. 16. Tripping system according to one of claims 1 to 15, characterized in that the thermomechanical converter (21, 31, 41, 51, 61) is only heated indirectly. 17. Trigger system according to one of claims 1 to 15, characterized in that the thermomechanical converter (21, 31, 41, 51, 61) both indirectly heated and also flowed through and through by part of the current flowing through the release system Joule heat is heated. 18. Release system according to claim 17, characterized in that that the thermomechanical converter (21, 31, 41, 51, 61) is electrically parallel to the magnetic short-circuit release (12, 22) is arranged. 130041/0589 19. Trigger system according to claim 17, characterized in that that the thermo-mechanical converter (21, 31, 41, 51, 61) is electrical is arranged in series with the magnetic short-circuit release (12, 22) and preferably through a parallel resistor 6 is bridged. ' 041/0503