EP0655760B1 - Electrical switch device - Google Patents

Description

The invention relates to an electrical switching device according to the preamble of the claim 1.

Switching devices with which in particular in the medium voltage and high voltage range Overcurrents, preferably short-circuit currents, are switched off trained as a circuit breaker, for. B. for high voltage as SF6 circuit breaker or for medium voltage as vacuum switch or low oil switch as well as also SF6 circuit breaker.

A switching device of the type mentioned at the outset is known from EP 0 363 746 A1 Principle became known. After that is a thermistor that has a positive temperature coefficient has, connected in series with a contact arrangement and parallel to The thermistor is a varistor and parallel to the thermistor can also be Be switched coil with which the contact device can be opened.

EP 0 363 746 A1 does not state which type of switching device is used. It can be seen that the thermistor has a thermal delay device is provided, so that the arrangement only for the motor protection or for the Short-circuit protection can be used in low-voltage switchgear, which conventional fuses as well as automatic fuses replaced can be.

It also does not show how the thermistor works with the coil to to open the switching device.

WO 93/07667 describes the series connection of a thermistor with a trigger element described and there is an impedance parallel to the thermistor; only with the 10 and 11, a varistor is controlled in parallel with the thermistor. A miniature circuit breaker is to be provided for the switching device his.

The object of the invention is to provide a switching device for medium or high voltage to create the type mentioned, which is cheaper with the same switching capacity can be produced.

This object is achieved by the characterizing features of the Claim 1.

The invention takes advantage of certain materials and certain compositions of materials, such as those in the DE 42 21 309 A1 are described, with increasing current their temperature and thus their Increase resistance. If you connect such a non-linear resistor in series with a switching device, then when a short-circuit current occurs or in general an overcurrent limits this current so that the prospective short circuit or Overcurrent is not reached. This has the consequence that a specifically for short-circuit shutdowns designed circuit breaker does not have to be used, but that a disconnector or switch disconnector can be used that is only capable must be to switch off the residual or nominal current in a certain time. The usage of such a non-linear resistor in connection with such a separation or switch disconnector leads to a significant reduction in the cost of one Short-circuit switching device. The disconnector or switch disconnector can be used for certain Purposes as a quick disconnect switch; it’s also possible, when the non-linear resistor holds the voltage for a relatively long time can use an inexpensive, if not to say cheap, slow disconnector, which in the off position is only able to maintain the voltage. An impedance is connected in parallel with the non-linear resistor. This Impedance can be linear or non-linear, i.e. H. voltage-dependent. You can as Capacitor can be formed, which can charge, so as to reduce voltage spikes. Instead of a capacitor, a varistor or a resistor can also preferably be used be provided. The impedance can be integrated with the nonlinear resistor or be discreet. The Non-linear resistance is a means of detecting the change in properties the resistance associated with a change in current in the network conductor, which means when it occurs of the determined overcurrent generate a signal that an actuator is supplied for the disconnector or switch disconnector.

With this arrangement, instead of a circuit breaker, for example instead a vacuum chamber or an SF6 circuit breaker a simple disconnector or Load switches are used, the disconnector being such a switch, which in the switches essentially in the de-energized state, whereas the load switch under the Has to switch nominal power.

One takes advantage of the fact that when the overcurrent occurs change certain properties of the non-linear resistor. For one thing changes the voltage to be tapped at it, since the non-linear resistance has its resistance value elevated; this change in voltage can be detected and processed become.

The non-linear resistance changes when an overcurrent occurs and the Temperature on the other hand its geometric dimensions; the change in dimensions, in particular the change in volume or length can be used for this to effect a shutdown.

Of course, a temperature measuring element can also be attached to the resistor become; the increase in temperature then generates the signal in question.

Furthermore, according to claim 5, an actuator, for. B. in the form of a piezo element, which is switched when the increased voltage drop occurs this voltage is applied to the resistor and thereby also a voltage Changes in length or a deflection. This change in length or deflection can then to actuate the actuator to turn off the Switch disconnector can be used.

A particularly advantageous embodiment of the invention can go according to claim 6 go that the non-linear resistor or resistance element is a switching mechanism is associated with a latching point that actuates the switching device. According to claim 7, the switching mechanism can be a sliding element be assigned, which is preferably designed as a pin or sleeve and controls the actuator for the switch or directly actuates the switch. The non-linear resistor can of course also be one according to claim 8 or 9 be assigned an electromagnetic trigger that actuates the switching mechanism, d. H. unlatched.

A conductor can be connected to an electrode of the non-linear resistor be part of the electromagnetic trigger.

In a particularly advantageous manner, the non-linear resistor with the switching mechanism and / or the trigger and / or the conductor and / or the Interlocking held together by a support arrangement made of insulating material his; the carrier arrangement can be according to one of claims 12 and 13 be formed or comprise according to claim 14 a sleeve made of insulating material, which at least encloses the non-linear resistor, the non-linear Resistance can be immediately and tightly enclosed by the shell and the trigger and / or switching mechanism are housed in a free interior of the sleeve.

The sleeve can be tubular, preferably cylindrical be and have caps at their ends, at which an electrical supply or Discharge is connected.

In a particularly preferred manner, the insulating material for the carrier arrangement, in particular the shell is a material with a preferably voltage-dependent Resistance value, preferably varistor ceramic, can be achieved, whereby that local overvoltages can be derived. Of course, that can be done accordingly the claim 12 or 13 formed carrier assembly from the same Material.

The sliding element can preferably be designed as a pin be and are under the pressure of a spring assembly, so that it is unlatched the latch changes its position, e.g. B. jumps out of the shell.

There is a possibility according to claim 21, the switching mechanism with a Lock formed by a spring element, which has a pin which of the Force is exerted by a spring, holds at nominal current and releases at overcurrent. The spring element can according to claim 22 made of bimetal or one Shape memory alloy to be made and formed.

A fuse wire can also be used as a lock, which holds the sliding element against the force of a spring. As soon as the overcurrent occurs, the fuse wire will melt and release the force of the spring. Of course there is also the possibility that the sliding element in a sleeve is held at one end in which a compression spring and the Fusible wire is added and that the sleeve at the other end has a contact protrusion with one with the non-linear Resistance electrically connected mating contact is contactable. If the fuse wire melts and the sliding element has jumped outwards, causing the Trigger for the switch-disconnector is only needed a new sleeve with the sliding element, the compression spring and the fuse wire can be used, so that the exchange very is simple.

Further advantageous embodiments of the invention are the others See subclaims.

Using the drawing, in which some embodiments of the invention are shown, the invention and others advantageous refinements and improvements and other advantages Invention will be explained and described in more detail.

Fig. 1

eine Schaltungsanordnung eines Netzes mit eingesetzten, nicht linearen Widerständen,

Fig. 2

eine Schaltungsanordnung für nur einen Netzleiter,

Fig. 3

eine Anordnung eines nicht linearen Widerstandes,

Fig. 4

eine der Fig. 2 ähnliche Schaltungsanordnung mit einem nicht linearen Widerstand,

Fig. 5

eine Schaltungsanordnung mit nicht linearem Widerstand und einer Sicherung,

Fig. 6

eine Vorrichtung zur Betätigung einer Auslöseeinrichtung, mit integriertem, nicht linearen Widerstand,

Fig. 7

eine weitere Ausführungsform ähnlich der der Fig. 6,

Fig. 8

eine vergrößerte Darstellung eines Teilbereiches der Fig. 7,

Fig. 9

eine weitere Ausführungsform der Erfindung mit einem nicht linearem Widerstand und

Fig. 10

eine vergrößerte Darstellung eines Teilbereiches der Vorrichtung gemäß Fig. 9.

Show it:

Fig. 1

a circuit arrangement of a network with inserted, non-linear resistors,

Fig. 2

a circuit arrangement for only one network conductor,

Fig. 3

an arrangement of a non-linear resistor,

Fig. 4

2 similar circuit arrangement with a non-linear resistor,

Fig. 5

a circuit arrangement with a non-linear resistor and a fuse,

Fig. 6

a device for actuating a triggering device with an integrated, non-linear resistor,

Fig. 7

another embodiment similar to that of FIG. 6,

Fig. 8

7 shows an enlarged representation of a partial area of FIG. 7,

Fig. 9

a further embodiment of the invention with a non-linear resistor and

Fig. 10

9 shows an enlarged illustration of a partial area of the device according to FIG. 9.

1, there are three network conductors R, S, T in the outlet from a transformer station 10, in which the high voltage originating from the high-voltage network R ₁ , S ₁ , T _{1 is} transformed into medium voltage.

The three conductors R, S, T each contain one that is not linear Resistor serving PTC resistor 11, 12 and 13, the a non-linear impedance 11a, 12a, 13a, preferably a varistor is assigned, as well as a dashed line Disconnector 14 with contact points 15, 16 and 17 in the conductors R, S, T. The disconnector 14 also includes a switch actuator 18, which via feed lines 19, 20, 21, which are connected to a common line 22 with Tripping elements 23, 24 and 25 are connected. The trigger elements 23, 24 and 25 are assigned to the PTC resistors 11, 12 and 13 and detect changes in the properties of the PTC resistors 11, 12 and 13, being due to the detected Send changes via lines 19, 20, 21, 22 signals, with which the actuating mechanism 18 is controlled so that contacts 15, 16 and 17 are opened. The PTC resistors 11, 12 and 13 change when increasing the R, S, T conductors flowing current values their temperature and thus their electrical Resistance, so that the contact points 15, 16 and 17 of the circuit breaker 14 flowing current is limited. As elements to detect the change in the properties of the PTC resistors 11, 12 and 13 can do a variety of means to be used.

2 is parallel to a PTC resistor 30 a device 31 for detecting the change in Voltage switched across the PTC resistor, its output signal via a line 32 to the triggering or actuating mechanism 18 is supplied.

The triggers 23, 24, 25 can also be omitted and the PTC resistors 11, 12, 13 accommodate the actuator. So located 3 PTC material 34 in the embodiment according to FIG inside a shell 35 made by a lower lid 36 electrically conductive material is closed. Between the upper end of the PTC material 34 and an upper end cover 37 there is a free space 38 and this is free space provided that the PTC material 34 when a Overcurrent and with a subsequent temperature increase its length changes. To detect this change in length a plate 39 on the upper, free end of the PTC material electrically conductive material on which an articulated lever arrangement 40 connects the mechanically the actuator 18 controls. The sleeve 35 is made of electrically insulating Material and on the lid 36 and the plate 39 is a feed conductor 41 or discharge conductor 42 connected to the 3 in the course of, for example, the Mains conductor R can be used. The lever mechanism 40 is preferably made of insulating material. The one on plate 39 connected conductor 42 is through an opening 43 from the room 18 led out; the lever linkage 40 stands over a hole 44 in connection with the plate 39. Instead of a shell, too Handrails are used, with a handrail in the middle PTC resistance can penetrate. The material from which the Cover or the handrails is or are insulating Material, possibly with non-linear voltage-dependent resistance value, e.g. B. varistor ceramic.

In the embodiment according to FIG. 3, the element is, for example 23, with the changes in the properties of the PTC material 11 are detected, quasi integrated with the PTC resistor, and the lever linkage 40 corresponds in its operation to that Cable run 19/22.

4 is, for example, the power line R a PTC resistor 50 is used; is in parallel a voltage measuring device 51 connected via a line 52 an actuator 53 in the form of a piezo element, a voltage signal feeds. This tension causes a change in length of the piezo element 53, the actuating mechanism via a linkage 54 18 can be fed so that the contact point 11, for example can be opened. Instead of a piezo element 53, whose change in length can be used, could also be a piezo element be used, the deflection of which are exploited can; corresponding piezo materials are, for example, from the Siemens font "Vibrit" piezoceramic from Siemens, order no. N-281/5053, 190 163 PA 2818.

Another solution is shown in FIG. 5. In a ladder R is a PTC resistor 60 inserted and in parallel a fuse 61. This fuse 61 is known per se and has a sleeve 62, one end of which has a contact cap 63 and the other end closed with a contact cap 64 is. A guide stub 65 is crimped into the contact cap 64, in which a pin 66 is guided. Between the spigot 66 and the lower cap 63 there is a fuse wire 67 and by means of a spring not shown in FIG. 5 the pin 66 is acted on in the direction of arrow A. About Zu and Discharge lines 67 and 68 are the cover caps 63 and 64 connected to the line conductor R so that the fuse 61 in parallel is connected to the PTC resistor. If there is an overcurrent occurs, the resistance of the PTC material will increase sharply, so the current is essentially through the fuse flows. As a result, the fuse wire 67 is melted and the pin 66 in the direction of arrow A in the dashed position 66a spent. This movement of the pin 66 becomes the operating mechanism 18 fed so that the load break switch 14th can be operated.

A relatively simple fuse can be used as a fuse that can only withstand the voltage, but no nominal current must lead. It only needs for a small nominal current to be designed.

Another embodiment of the invention is shown in FIG. 6. Located within a sheath 70 of insulating material there is a PTC resistor 71. In FIG. 6 at the lower end the cover 70 is closed with an electrically conductive cap 72, which cap has a cup shape with an L-shaped cross section has flanged edge 73 with which it the lower Encloses the end of the sheath 70. There is an electric on the cap 72 Conductor connected, for example a conductor 41 the upper end of the PTC material ends at a distance from the upper End of the sheath 70, which there is the same as the cap 72 Cap 74 is complete. On the top end of the PTC material there is an electrically conductive layer 75 on the a conductor rod 76 is connected which is an electromagnetic system 77 reaches through. The upper end of the conductor track 76 is with the cap 74 electrically connected. Inside the free Space between the cover 75 and the cap 74 is a switching mechanism 78 with a trigger lever 79, which with a Pawl projection 80 cooperates on a pin 81. If the electromagnet system responds with a magnet armature 82 within the switching mechanism 78, the trigger lever 79 clockwise pivoted and under the pressure of no closer shown spring is after the release of the latch 80 of the Pin 81 moves in the direction of arrow A, whereby as in the arrangement 5, the operating mechanism 18 is operated to to open the switch. The actuation mechanism is then not necessarily trained as a switch lock.

7 shows a similar shape. Within a shell 85 made of electrically insulating material, which according to closed at the bottom and top by a cap 86 and 87 the PTC material is 88. The PTC material has a central opening 89 which surrounds a conductor element 90, which connects the PTC resistor 88 to one in the drawing slightly higher than the upper end. At the other, lower end is one Plate 89a screwed to the conductor element 90, which also with the PTC material 88 is in electrically conductive connection. To the (in the drawing above) free end of the conductor element 90 there is a U-shaped contact element 91, into which a contact pin 92 engages. Reference is now made 8, this area in an enlarged view shows.

The contact element 91 has two contact legs 93 and 94, in which the pin 92 engages. The pin 92 is on a rotating part 95 molded, which inside a sleeve 96 made of insulating Material attached to the end facing the conductor element 90 and is crimped into it; protrudes through an opening 97 the pin 92 out of the sleeve 96. The top end of the sleeve 96 is on a retracted shelf 98 of the pot base 99 of the cap 87 fixed with a flange 91a. Inside the sleeve 96 telescopically engages an inner sleeve 100 made of metallic Material into it that is open to the bottom part of the sleeve 96 and completed in the area of the bottom part 99 of the cap 87 is. It ends at a distance from the rotating part 95 so as not to be electrical to have a conductive connection to the turned part. The one made of insulating material existing outer sleeve 96 has in the area of the flange 91a lateral openings (not shown) through which on the Inner sleeve molded contact springs (not shown) to the outside reach for the shelf 98 of the pot base 99. The inner sleeve 10 is a sliding element and encloses a compression spring 101, one of which End at the rotating part 95 and the other end at the supports the upper closed end of the inner sleeve 100. The Compression spring 101 is surrounded with insulating material, so that a Current flow through the compression spring 101 is prevented. Between the upper end of the inner sleeve or a contact plate arranged there 102 and the rotating part 95, a fuse wire 103 is provided. There is thus an electrically conductive connection from the contact element 91 partly 92/95 and one attached to it End of the fuse wire 103; the other end of which is about the Contact plate 102, the inner sleeve 100 and its radially outward through the outer sleeve through spring contact springs Board 98 contacted. If the fuse wire 103 is at an overcurrent melts through, then the inner sleeve 100 under the Pressure of spring 101 driven outwards in the direction of arrow A, similar to the pin 81 in the arrangement of FIG. 5. If the fuse wire 103 is melted, is only that Take sleeve 96 out and with a new sleeve assembly To replace sleeve 96 and inner sleeve 100. Possibly. can on the sleeve 96 a handle can be attached to pull out and replace to facilitate.

In the embodiment according to FIG. 10, the fuse wire is not available. On a conductor element screwed into the PTC material 88 110 is a lead screw 111 made of insulating material screwed down the top end of the PTC resistor 88 towers. The lead screw 111 is in the area of the upper one Cap 87 provided with a guide bottom 112, in which the lower end of an outer sleeve 113 is pressed, which in the Inside the guide 112 located inner end 114 a crimp having. One is supported on this flanging 114 Compression spring 115, the other end of which flanged on the inward supports the upper end 116 of an inner sleeve 117. Means this flanging 116 is the inner sleeve with a rod 118 firmly connected. This rod 118 extends through the guide area 112 up to the vicinity of the free end of the conductor piece 110, on which a spring element 119 is fastened, which has a U-shape with two legs 120 and 121, which on their free ends are bent approximately V-shaped inwards and thus form a constriction 122. This engages in this narrowing 122 mushroom-shaped inner end 123 of the rod 118 and is supported by the spring element 119 held against the pressure of the spring 115. With an increased current flow and thus also at an elevated temperature deforms the spring element 119, in which the two Legs 120 and 121 are spread, thus giving the rod 118 clear the way so that this is in the direction of arrow A under the Pressure of the spring 115 can move outwards. This movement in Arrow direction A then actuates the actuating mechanism 18 of the Switch. The material from which the spring element 119 is made can either be a bimetallic or shape memory alloy consist.

The casing 70 or 85 of the embodiments according to FIGS. 6 to 10 is made of insulating material. Particularly preferred This insulating material can be varistor ceramic. The The reason for using the varistor ceramic is from the above mentioned German patent application can be seen.

7 to 10 is an electrical conductive connection from lower cap 86 to PTC material 88 provided via a stranded wire 130; from the top of the PTC material up to cover cap 87 is another stranded wire 131 provided; some of the current is now flowing via the conductor element 90 and the fuse wire 103 or the conductor element 110 and the sleeve 111 or the spring element 119 and the rod 118 towards the cap 87. This makes a parallel connection of PTC material 88 and fuse wire 103 or spring element 119 reached.

In the arrangements according to FIGS. 7 and 8 or 9 and 10 need the fuse wire and the U-shaped spring element 119 with to conduct only part of the current to conductor 118. At 9 and 10, only the conductor 118 be pushed in again, either manually or by a Remote control can be done. In the embodiment according to FIG. 7 and 8 is only the securing element with the sleeve 96, the Inner sleeve 100 to the fuse wire 103 and the compression spring 101 to be replace. Because these components are only minor Have to carry current share, since the main current share over the PTC resistor and leads 130 and 131 leads can this fuse element can be designed quite inexpensively. If the arrangement according to FIGS. 7 and 8 has responded, needs just replaced the fuse element with a new one become.

The inner sleeves can be used as a sliding element for actuating the Switching device or for unlatching one as a switch lock trained actuator.

Claims (26)

1. An electric switch device which is insertable in a line conductor (R, S, T) of an electric medium-voltage or high-voltage system and interrupts at least one line conductor (R, S, T) during the occurrence of a short-circuit current, with a switch device (15, 16, 17) with a non-linear resistor (11, 12, 13) whose resistance value increases non-linearly with rising current value, preferably a non-linear resistor with a positive temperature coefficient, being connected in series, characterised in that the switch device (15, 16, 17) is an electric disconnector or load interrupter switch, a non-linear or linear impedor (lla, 12a, 13a), preferably a varistor, is switched parallel to the non-linear resistor (11, 12, 13), means (23, 24, 25) are provided for detecting the change of the properties of the non-linear resistor (11, 12, 13) during the change of current in the line conductor (R, S, T), which means (23, 24, 25) produce a signal during the occurrence of a specific excess current, which signal can be supplied to an actuating device (18) for the switch device and the actuating device (18) actuates the switch device (15, 16, 17; 18) during the occurrence of the signal.
2. A switch device as claimed in claim 1, characterised in that the means (31) detect the change of voltage on the non-linear resistor (30).
3. A switch device as claimed in claim 1 or 2, characterised in that the means (39, 40) detect the changes in the geometric dimensions of the non-linear resistor (34).
4. A switch device as claimed in claim 1 or 2, characterised in that the means detect the change in temperature of the non-linear resistor.
5. A switch device as claimed in one of the claims 1 to 4, characterised in that the means (51) for detecting the change of voltage of the non-linear resistor (50) occurs by an actuator (53) which is connected parallel to the same, preferably formed by a piezoelectric element, whose change on its geometry actuates the actuating device for the switch device (15, 16, 17).
6. A switch device as claimed in one of the claims 1 to 5, characterised in that the non-linear resistor is associated with a switching mechanism (78) with a latching place (80) with which the disconnector or load interrupter (15, 16, 17) can be actuated on the occurrence of an excess current and unlatching of the latching place (80).
7. A switch device as claimed in claim 6, characterised in that the switching mechanism (78) is assigned a slide element (81) which actuates an actuating device (18) for the disconnector or load interrupter on the unlatching of the latching place (80) of the switching mechanism (78).
8. A switch device as claimed in claim 6 or 7, characterised in that the non-linear resistor (71) is associated with a tripping device (77) which actuates the switching mechanism.
9. A switch device as claimed in claim 8, characterised in that the tripping device is an electromagnetic trip element (77) with an armature (82) which actuates the latching place (80) of the switching mechanism.
10. A switch device as claimed in one of the claims 8 and 9, characterised in that a conductor (76) is connected to an electrode (75) of the non-linear resistor (71) which is a part of the electromagnetic trip element (77).
11. A switch device as claimed in one of the claims 6 to 10, characterised in that the non-linear resistor (71) is held together with the switching mechanism (78) and/or the trip element (77) and/or the conductor (76) by means of a carrier arrangement (70) made of insulating material.
12. A switch device as claimed in claim 11, characterised in that the carrier arrangement is provided with at least one support pole made of insulating material and that the linear resistor forms a unit in combination with the switching mechanism and/or the trip element and/or the conductor.
13. A switch device as claimed in claim 12, characterised in that the support pole centrally penetrates the non-linear resistor in the centre.
14. A switch device as claimed in claim 11, characterised in that the carrier arrangement is arranged as a housing (85) or a sleeve which encloses at least the non-linear resistor (88).
15. A switch device as claimed in claim 14, characterised in that the trip element and/or the switch mechanism are arranged in a free interior space of the sleeve (85).
16. A switch device as claimed in claim 15, characterised in that the sleeve (85) is tubular, preferably cylindrical, and is provided at its ends with blanking caps (86, 87) to which electric lead or output wires (130, 131) are connected and that the non-linear resistor (88) is connected in an electrically conductive manner with the blanking caps (86, 87).
17. A switch device as claimed in one of the claims 11 to 16, characterised in that the insulating material is provided with a non-linear resistance value in such a way that on the occurrence of an excess current the resistance value drops.
18. A switch device as claimed in one of the claims 10 to 12, characterised in that the insulating material is made of varistor ceramics.
19. A switch device as claimed in one of the claims 7 to 18, characterised in that the slide element is arranged as a tappet (118) and jumps out from the carrier arrangement, preferably the sleeve, under the pressure of a spring arrangement (115).
20. A switch device as claimed in one of the claims 15 to 19, characterised in that the non-linear resistor (88) fills the sleeve (85) only partially and that the switching mechanism and/or the conductor and/or the electromagnetic system provided with the armature are housed between the non-linear resistor (88) and the adjacent electrically conductive free end.
21. A switch device as claimed in one of the preceding claims, characterised in that the switching mechanism is formed with a locking means by a catch spring element (122, 123) which fixes the slide element (118) which is preferably arranged as a tappet and is under the pressure of a spring arrangement and releases the same during the occurrence of an excess current.
22. A switch device as claimed in claim 16, characterised in that the catch spring element (119) is provided with a U-shape with throats (122) formed by its legs (120, 121) which consist of material which change their form at a temperature (thermostatic bimetal or shape memory alloy) and that the engaging behind a mushroom-like extension on the interior end of the tappet (118) and thus fixing the same.
23. A switch device as claimed in one of the claims 1 to 20, characterised in that a fusible wire (103) is provided as a lock which fixes the slide element (100) against the pressure of a spring (101) and melts through on the occurrence of an excess current, so that the spring (101) presses the slide element (100) outwardly.
24. A switch device as claimed in claim 23, characterised in that the slide element (100) with pressure spring (101) and fusible wire is arranged within a sleeve (96) which is provided at its interior end with a contact projection can be brought into contact with a counter-contact which is electrically conductively connected with the non-linear resistor.
25. A switch device as claimed in claim 23 and 24, characterised in that the slide element (100) is formed by an inner sleeve (100) which is outwardly enclosed, inwardly open and is guided in the sleeve (96) and that the inner sleeve (100) encloses the fusible wire (103) and the pressure spring (101).
26. A switch device as claimed in one of the preceding claims, characterised in that the non-linear resistor (90) is disposed in a main current path and the fusible wire (103) or the U-shaped spring (119) in a current path extend parallel thereto.

Images