DE2720736A1 - HIGH CURRENT LIMITER FOR AN ELECTRICAL SWITCHGEAR - Google Patents

Description

Merlin Gerin, 38 Grenoble (France)

Maximum current limiter for an electrical switchgear

The invention relates to a maximum current limiter for an electrical switchgear with an automatic Switch with overcurrent protection and with one normally the movable contact held in the closed position by a fast-acting displacement device In the event of a sudden increase in current, it can be moved into the open position quickly, but as a result when the upper current disappears Becoming inactive, the displacement device can be automatically returned to the closed position.

In DT-OS 2 326 117 and the associated additional applications according to DT-OS 25 30 161 and DT-OS 25 30, a device for maximum current limitation of the aforementioned type is already described, which is part of an electrical disconnector for suddenly bringing the moving contact in the open position can be independent of the overload protection or in connection with an automatic circuit breaker. This can be in series

Hefneraplatz 3 8600 Nuremberg 11

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Telephone (08 11) 20 40 81 -83

telex 06/22 327

Telegrams "Patwetzel"

Nbg. 6311

StadtaparkaaM Poetacheckkonto Nbg 1 528.364 NOmbcrg 111 51 - R

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be connected to the circuit to be protected, where the maximum current limiter only limits the short-circuit current and the actual disconnection is triggered by the circuit breaker. In such a limiting device the moving contact is moved very quickly and could even come back into the closed position before the circuit breaker has even had time to function and release. In order to To prevent early closing during a short circuit, it has already been proposed to put the moving contact in To lock the open position or at least to delay the closing of the contact. The lock requires a Manual intervention in order to reach the closed position again at the end, which results in a relatively long failure of the Energy supply. The known delay devices have similar disadvantages; It is with it is not possible for them to adapt the duration of the interruption to the level of the short-circuit current. The absence of Voltage in a single circuit over a long period of time greatly affects proper power supply of facilities in parts of the plant that are not affected by the fault. Switching on again is also possible different relays required. This disadvantage naturally narrows the possible applications of the known maximum current limiters a.

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Accordingly, it is the object of the invention to achieve one while avoiding the disadvantages observed in the prior art To create or further develop maximum current limiters, without any disadvantage for unaffected parts of the system the duration of the overcurrent shutdown largely independent of the level of the overcurrent can be limited in such a way that normal operation takes place as soon as possible after the overcurrent has subsided.

The solution to this problem is given in a maximum current limiter of the type described in that one which interacts with the movable contact and is essentially independent of the size of the overcurrent same opening duration of the movable contact causing delay means is installed and that this Delay means is designed for an opening period that is greater than the response time of the overcurrent release.

Essential for the maximum current limiter according to the invention is therefore the delay means with the movable Contact cooperates and is designed so that a substantially equal opening duration of the movable contact is reached regardless of the level of the overcurrent. The opening time is always longer than the response time the actual release device.

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Advantageously, the delay element has a weight that is limited in relation to the movable contact Has the possibility of movement and is arranged in the opening path of the movable contact. The weight will set in motion by impact across the moving contact after the moving contact has passed a piece of its Has covered the opening path. The duration of the movement of the weight depends largely on its mass and, if applicable on the characteristics of the return springs arranged here. The strength of the impact that occurs is in itself a function of the level of the short-circuit current, theoretically does not affect this duration of movement and thus also not the time until the contact returns to the closed position. You choose the time for that renewed closing of the contact long enough with regard to the response time of the overcurrent switch and sufficient briefly, so that voltage drops in a selected circuit do not cause the electromagnetic relay to drop out cause.

Furthermore, the task of limiting and separating can advantageously be combined in a single apparatus as the rapidly moving contact is held in the open position by the release device can. On the other hand, the maximum current limiter can also be used independently of the main switch and in series with the

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sem be switched to advantageously the usual Avoid safety devices. Each pole of the high-current switch has its own actuation means as well as its own delay means.

Further advantages and details of the subject matter of the invention emerge from the following description of a preferred embodiment and the accompanying schematic drawing; in this show:

Fig. 1 shows the circuit diagram of an electrical system with a maximum current limiter according to the invention Is provided,

2 shows a graph of the change in the current intensity plotted over time,

3 shows the maximum current limiter in a schematic representation as an axial section,

4 shows the maximum current limiter according to FIG. 3, sectioned according to IV-IV according to FIG. 3,

FIG. 5 shows a section analogous to FIG. 3, but with a movable contact in an intermediate position,

FIG. 6 shows a section analogous to FIG. 5, but with the movable contact fully open, and FIG

Fig. 7-9 the various displacement paths of the movable contact and the associated weight

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for different strengths of short-circuit currents, each plotted against time in a graph .

According to FIG. 1, a two-stage electrical system with system parts A and B consists of a network transformer 10 and a maximum current switch 12 connected in series with the transformer and an automatic main switch 14, which in turn is connected to a distribution rail 16. The distribution rail feeds two branch circuits 18, 20. A circuit breaker 22 at the input of the branch circuit 20 protects a consumer fed by this circuit 24. The branch circuit 18 feeds an electric motor protected by a control contactor 28 and a protective fuse 30 26. The system can of course have a large number of branch circuits with different connection values and can, as usual, be equipped with selective overload protection devices to ensure that the supply is not affected Plant parts to maintain in the event that in a branch circuit, for example the branch circuit 20, a malfunction occurs as indicated in FIG. 1. The overcurrent contactor of the automatic main switch 14 ensures this selectivity by a suitable means, for example by quantitative measurement and the maximum current switch 12 limits the current strength of the short-circuit current in the entire system. From the occurrence of a fault

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on the contacts of the maximum current switch 12 open immediately in order to limit the short-circuit current. Of course must close again in a selective circuit of the high current switch 12 to the power supply in the unaffected circuits from the moment the fault occurs Turning off the circuit breaker 22 has been eliminated. Closing the maximum current switch 12 too quickly Elimination of the fault generates reopening and successive disconnections as a result of the short-circuit currents. Switching on again too slowly interrupts the power supply for so long that the electromagnetic Relay drop out. This ensures continuous power supply in the unaffected branch circuits adversely affected.

The diagram according to FIG. 2 explains the mode of operation of the device. The one drawn with a dashed line Curve indicates an oscillation of a short-circuit current, the curve drawn with a full line the maximum current limit by the activation of the maximum current switch 12. The respective response time is indicated by points T1 and T2 the circuit breaker (s) 22 and the electromagnetic devices in the event that they become effective of the control contactor 28 specified. Obviously introduces one The contacts of the maximum current switch 12 drop out before the

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the time T1, which is the opening time of the circuit breaker 22 corresponds, in which the fault occurs, to a renewed response of the high current switch 12. On Closing this switch after a period longer than T2 causes the electromagnetic relays to drop out and an interruption of the power supply in the case of the motor 26. The time T for switching on the maximum current switch again 12 is therefore between T1 and T2; there is a time difference of a few milliseconds.

3-6 show one pole (corresponding to a phase) of the maximum current switch 12 with a movable contact, which is arranged on a contact bridge 32 and which cooperates with a pair of fixed contacts 34,36, which are connected to intersecting lines 38, 40 with a rectangular cross section. These cross a annular magnet winding 42, which is in the form of an elongated Slit has a gap 44. The underside of the contact bridge 32 in the form of a tongue protrudes in the closed position the contact bridge 32 into the gap 44. A spring 46 presses the contact bridge 32 into the closed position. After a sudden change in the current flowing through the lines 38, 40 causes the magnetic field in the gap 44 in the contact bridge 32 induction currents and (according to DT-OS 25 30 162) a sudden opening of the contact bridge 32 by pushing into the open position.

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According to the invention, the contact bridge has a weight 48 coupled, in the direction of the open position of the contact bridge is displaceable, and the bottom has a groove 50, in which the upper part of the contact bridge with play 32 fits. The path of the contact bridge 32 with respect to the weight 48 is on the one hand by ribs 52, which a Prevent jamming of the contact bridge with the groove 50, and on the other hand limited by stops 54. A preload spring 56 between the contact bridge 32 and the weight 48 presses these parts into one through the rib 52 certain mutual distance. The whole thing can be moved relative to one another around the limited path 1. The spring 46 causes the contact pressure and the biasing spring 56 with a slightly lower spring force holds the weight 48 in its somewhat removed from the contact bridge 32 position in order to open the free path 1 in the direction of the contact bridge of contact.

The device is housed in a housing 58 made of insulating material. This housing carries the weight 48 and also has a planar stop 60.

The maximum current limiter according to the invention works as follows:

In Fig. 3, the closed position of the maximum current switch is 709848/0857

12 shown. Here, the contact bridge 32 is held in the closed position by the spring 46. When occurring a fault current drive the electromagnetic generated in the lines 38, 40 as a result of this current Forces the movable contact bridge 32 out of the gap 44 in the direction of the open position of the contacts 32,34,36. As a result the low mass of the contact bridge 32, it moves very quickly against the force of the springs 46,56 by the Game 1, the weight 48 being practically immobile in a first stage due to its considerable mass remain. According to FIG. 5, the contact bridge 32 is at a sufficient distance after passing through the free play 1 of the fixed contacts 34,36 to switch off the current «during this first phase of opening the contacts the weight 48 neither hampers nor retards the movement of the contact bridge. During their further movement the contact bridge 32 strikes the weight 48 in that it strikes the stop surfaces 54. This increases the weight 48 moves and prevents the contact bridge from closing, as described below with reference to FIGS. 7-9 will.

The diagram according to FIG. 7 shows, in full line, the displacement of the contact bridge 32 as a function currently; in the dashed line is the displacement of the weight 48 under the condition of a proportional

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moderately weak short-circuit current shown. At the time ti the contact bridge 32 hits the weight 48, which maintains a substantially uniform movement, while the contact bridge is pushed back by the impact in the direction of the closed position. The contact bridge and the weight move away from each other in opposite directions. At time t2 or at a Distance 1, which is limited by the ribs 52, is opposed to the direction of displacement of the weight by an impact directed. Another shock that reverses the direction of movement occurs at time t3. Finally, the contact bridge 32 and the weight 48 move in the same direction of movement at the point in time t4 to return to the original closed position, which can be seen from FIG. The contact bridge 32 is reached not the stop position shown in FIG. 6; the weight 48 performs a reciprocating motion with successive Impact effects, the number of which depends on the strength of the impact exerted on the weight 48.

The diagram according to Fig. 8 explains the mode of operation of the maximum current switch under a slightly larger short-circuit current, which, however, is not so large that the contact bridge 32 rests against the stop. The time it takes to close again the contact bridge 32 up to the time t4 is in the w

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essentially the same as the mode of operation represented by FIG. When an even larger short-circuit current occurs according to the diagram shown in FIG opening of the contact bridge 32 is limited by the stop 60 at time t3. After repeated jerky striking, the frequency of the strike depends on the size of the short-circuit current, the contact bridge closes 32 again. From the diagrams according to FIGS. 7-9 it can be seen that this closing is caused by the mass of the weight 4 8 is braked. This results in an essentially constant, independent of the size of the short-circuit current The opening time of the contacts of the maximum current switch has been reached. The length of the opening period is through Selecting the mass of the weight 48 can be determined.

In the embodiment shown in the drawing, the piston-shaped weight 48 covers the Contact bridge 32. Obviously, it acts as a result of the heat created by arcing between the contacts 32,34,36 resulting gas pressure in the direction of opening of the contacts and thus influences the movement of the weight 48 and the contact bridge 32.

The subject matter of the present invention is particularly advantageous in connection with that known from DT-OS 23 26 117 Device for quickly moving a loaded

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Removable circuit breaker contact due to the repulsion effect, but also generally applicable to circuit breakers, in which contacts can be moved by an electrodynamic effect. The mechanical coupling between the contact bridge 32 and the weight 48 take place in a different manner known per se. Furthermore, the contact bridge 32 with the release device described in FR application 2 237 302 be equipped.

Another alternative is to design the previously described weight 48 in several parts, the partial weights can perform limited mutual relative movements.

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Claims (9)

TERGAU & POHL ι «. ■» * <* -. · * ». B / 45 (77247) PATENT LAWYERS ' Nuremberg, the ™ May 6, 197 " 27 * 0736 Merlin Gerin, 38 Grenoble (France) Claims Λ.High-current limiter for an electrical switchgear with an automatic switch with overcurrent contactor and with a movable contact normally held in the closed position, which can be brought into the open position by a fast-acting sliding device in the event of a sudden increase in current, but automatically returned to the closed position when the overcurrent disappears as the sliding device becomes inactive is, characterized in that a delay means cooperating with the movable contact (32) and independently of the magnitude of the overcurrent causing an essentially equal opening duration of the movable contact (32) is built in and that this delay means is designed for an opening duration which is greater than the response time of the overcurrent release (12,22). 2. Maximum current limiter according to claim 1, characterized in that the delay means is movable by a fixed game (1) with respect to the movable contact. 7 09848/0857 Hefnersplatz 3 Telephone (09 11) telex Telegram" Bayer. Association bank StadtaparkaiM Postal checking account 8500 Nuremberg 11 20 * 0 81-83 06/22 327 "Patwetzel" Nbg. 6 311606 Nbg. 1,528,354 Nuremberg 111 51 -K ORIGINAL INSPECTED Ches and with the movable contact mechanically coupled weight (48) includes of a predetermined mass and that the duration of the opening of the movable contact (32) essentially depends on the duration of the movement of the weight can be controlled independently of the opening force acting on the movable contact. 3. High current limiter according to claim 1 or 2 with part of an electrical circuit forming, electromagnetically controlled breakers, characterized in that the opening duration (T) of the movable contact (32) determined by the weight (48) is so shorter than the response time of the electromagnetically controlled Interrupter (14, 28) that undesired opening of the interrupter is avoided. 4. High current limiter according to claim 2 or 3, characterized in that the weight (48) with the movable contact (32) with limited free play (1) is mechanically coupled that one of the movable contact (32) of the weight to the coupling means (48) pushing away, however, an opening of the movable contact (32) within the free play (1) allowing spring (56). 5. Maximum current limiter according to claim 4, characterized in that - 709848/0857 shows that a spring (46) pressing the movable contact (32) in the closed position is also installed. 6. High current limiter according to one of the preceding claims, characterized in that the fast-acting displacement device includes a magnetic circuit (42) which includes at least one conductor (38, 40) through which the current flows, and which has a small air gap (44) in which protrudes in the closed position of the movable contact a lamella belonging to this contact, which is also repelled in a manner known per se by a suddenly increased current flow in such a way that the movable contact (32) moves quickly into the open position. 7. Maximum current limiter according to claim 6, characterized in that each of the poles of the device has both a means for rapidly moving the movable contact (32) as an independent opening or closing of the Moving contacts of the individual poles enabling delay means (including weight 48) carries. 8. Maximum current limiter according to one of the preceding claims, characterized in that the opening path of the movable contact (32) and the oscillation of the movable contact (32) or the weight (48) according to a 709848/0857 very strong increase in the current limiting stop
(60) is installed. 9. Maximum current limiter according to one of the preceding claims, characterized in that the weight (48) covering the movable contact (32) and is designed like a piston in such a way that the weight (48) is caused by gas pressure in the direction caused by the arc produced after opening the movable contact Contact opening is movable. 709848/0857