EP2461341A1 - Error-proof switching module and method for operating same - Google Patents

Abstract

The module has switching units including switching contacts that are arranged between connecting terminals in a series circuit for closing a load circuit by controlling the switching units. The switching units are arranged between controlling lines, where one of the switching units is arranged in series circuit with a release unit between the controlling lines. The release unit delays the control of the switching unit, and is connected with a delay circuit, and another release unit is connected with another delay circuit. A buffer condensator is arranged between controlling lines. An independent claim is also included for a method for operating a failure-safe switching module.

Description

The invention relates to a fail-safe switching module for switching a load having a first switching means having a first switching contact, a second switching means having a second switching contact, wherein between a first terminal and a second terminal of the first switching contact and the second switching contact in a series circuit are arranged to close a load circuit by driving the switching means, wherein the switching means are arranged between a first drive line and a second drive line.

Furthermore, the invention relates to a method for operating the fail-safe switching module for switching a load.

When a switching means, such as a relay, closes a switching contact, an arc can be produced at the contact. But even with an opening process of a switching contact, an arc can occur. Accordingly, it can be said of a Einschaltlichtbogen and a Ausschaltlichtbogen. Due to these arcs during the switching operations, after frequent opening and closing of the switching contact, wear of the contact surfaces may occur and, in the worst case, welding of the contact may occur. A welding of the contact means that the contact is permanently closed. Especially with fail-safe assemblies, such as a relay assembly for switching loads, it must be absolutely avoided that a switching contact can not be turned off or open. For this reason, preferably two switch contacts of two relays are connected in series in fail-safe relay modules, so that in the case of welding a switch contact the load can still be switched off by the switch contact of the respective other relay or a short circuit can be interrupted. To weld at a short circuit of the load To prevent two series-connected contacts, a fuse is prescribed to protect the contacts in a load circuit.

A switching module according to the preamble of claim 1 is known from Manual "SIMATIC, Distributed I / O F-Technology, ET 200S Distributed I / O System" Edition 08/2008, order number A5E00103684-07, known. In the manual the well-known switching module is described in chapter 7.8, pages 187-197 described.

The invention has the task of further developing the known switching module such that welding of the two switching contacts is avoided.

The object is achieved in that the first switching means is arranged in a series circuit with a first release means between the drive lines for the above-mentioned fail-safe switching module, wherein the first release means is configured to delay the driving of the first switching means. In this case, the first switching means is for example a relay. According to the invention, an additional release means is arranged in a circuit for driving the relay, which can interrupt a current flow through the relay and thus can cause a switch-on delay. The additional release agent may, for example, be configured as an additional mechanical contact, as a power semiconductor, as a transistor, etc. The delay of the activation of the first switching means has the consequence that the first switching means responds later than the second switching means, but so that the first switching contact is closed later than the second switching contact. Only when the second switching contact is completely closed, the first switching contact is closed. This chronological sequence of switching ensures that an arc preferably occurs at the first switching contact during a switch-on process or a switch-off process. This means, due to a load current and the resulting wear on the first switch contact would always fail first, the first switching means. The first switching means is referred to in this context as a load relay. The second switching contact of the second switching means, which corresponds to a second relay, is also referred to as load-free contact. The second switching contact of the load-free relay is thus spared.

In an advantageous embodiment, the first release means is connected to a first delay circuit. With the delay circuit, the duration of the time delay can be influenced.

In a further optimized embodiment, the second switching means is arranged in a series circuit with a second release means between the drive lines, wherein the second release means is configured to extend the driving of the second switching means. Since, as already mentioned, an arc occurs both during a switch-on and during a switch-off and thus damage the contacts, such as a relay, a second release means and an extension of a driving time of the second switching means is realized. Using the example of a relay for the second switching means can thus be maintained for a certain time by the second release means a holding current for the relay, which has the consequence that the corresponding second switching contact opens later. Since the first switching contact has already opened before the opening of the second switching contact and has drawn the arc, the second switching contact is spared even during an opening process.

Advantageously, in a further embodiment, the second release means is also connected to a further delay circuit.

Furthermore, it is advantageous if an energy store, in particular a buffer capacitor, between the drive lines, is arranged to extend the control of the second switching means.

In a further development of the switching module, it is advantageous if the first switching means has a third switching contact and the second switching means has a fourth switching contact, wherein the first and the second switching contact are designed as a closer and the third and the fourth switching contact as an opener. With the switching contacts, which are designed as opener, a monitoring circuit can be formed, whereby a fault of the affected relay can be detected.

For error detection, it is useful if the third switching contact and the fourth switching contact is arranged in a series circuit to a readback input of an evaluation, wherein the read-back input is designed as an inverting input. Since the said third and fourth switching contacts are configured as normally closed contacts, and switch simultaneously with the first or the second switching contact during a switching operation, a defect, for example a relay, can be detected. If the opener remains permanently open and does not return to its closed position, there is wear. Then, via the inverting input at the readback input, a on signal would be permanently present, which can be evaluated in connection with the instantaneous activation situation and from this a possible error situation can be determined.

In a further improved embodiment, the switching module has a backplane bus, which is designed for the modular construction of a juxtaposed from several electronic modules decentralized automation system. Such a modularly constructed automation system can be used, for example, for fail-safe automation systems (F systems) in systems with increased safety requirements. The F-systems are used to control processes with a safe which can be achieved directly by switching off Status. The fail-safe modules used differ essentially from the standard modules in that they have an internal two-channel design.

The above object is also achieved by a method for operating a fail-safe switching module according to claims 1 to 8, wherein for switching the load to the first drive line and to the second drive line, a switching voltage is applied, that closing the load circuit is prepared by the second switching contact is closed by driving the second switching means with the switching voltage and after completion of a closing operation of the second switching contact, the first release means is operated such that it is also driven by the switching voltage and then closes the first switching contact.

In a further development, the method is also supplemented with a switch-off process, wherein the switching voltage is disconnected from the drive lines to switch off the load, the opening of the load circuit is achieved by operating the first release means such that it separates the first switching means from the drive line and upon completion of an opening operation of the first switching contact, the second release means is operated to maintain a current flow through the second switching means due to the energy storage.

To obtain a diagnostic option, the method is supplemented in that simultaneously with the closing of the first switching contact, a third switching contact is opened and simultaneously with the closing of the second switching contact, a fourth switching contact is opened, wherein by means of the series connection of the third and fourth switching contact, a readback signal is generated for a read-back input.

As a result of the thus controlled switching processes, the method can advantageously be used for switching and switching off the load circuit, which has the load, a voltage source and a fuse, are used in such a way that a circuit breaker is used instead of a fuse. Due to the duration of the time offset of the switching of the switching contacts, for example, the two relays, can be dispensed with a prescribed according to the safety regulations fuse advantageously because it is no longer possible, the two switch contacts welded and thus permanently closed. Even if a switch-over to an existing short circuit, the second switching contact would have closed first and thus did not cause an arc, the subsequent first switching contact would pull an arc on itself and probably merge when switching to a short circuit. At the time of merging of the first switching contact but already triggered the circuit breaker. The second switching contact is still in tact, as prescribed by the safety regulations for fail-safe switching modules.

FIG 1

eine Prinzipschaltung eines fehlersicheren Schaltmoduls und

FIG 2

ein Diagramm zum Schaltverhalten.

The invention will be explained in more detail with reference to the drawing. Show it:

FIG. 1

a basic circuit of a fail-safe switching module and

FIG. 2

a diagram of the switching behavior.

According to FIG. 1 a fail-safe switching module 1 for switching a load 50 is shown. In order to close a load circuit 51, a first switching contact 11 and a second switching contact 21 are arranged in a series connection between a first connecting terminal 2 and a second connecting terminal 3. By driving a first switching means 10 and a second switching means 20 with a switching voltage U, the switching means 10,20 can be made to switch. The first switching contact 11 belongs to the first switching means 10, which is indicated by a dashed line of action.

The second switching contact 21 belongs to the second switching means 20, which is also indicated by a dashed line of action. For this purpose, the switching means 10,20 are arranged between the first control line 4 and the second control line 5. In a series connection to the first switching means 10, a first release means 31 is arranged between the drive lines 4, 5. The first release means 31 is configured to delay the activation of the first switching means 10. In order to support the delay, the first release means 31 is connected to a first delay circuit 31a.

Also in a series connection to the second switching means 20, a second release means 32 is arranged between the drive lines 4,5. Here, the second release means 32 is configured to extend the driving of the second switching means 20. The second release means 32 is connected to a second delay circuit 32a. To switch on the load 50, the switching voltage U is applied to the first drive line 4 and to the second drive line 5. The closing of the load circuit 51 is prepared by the second switching contact 21 is closed by driving the second switching means 20 with the switching voltage U and after completion of a closing operation of the second switching contact 21, the first release means 31 is operated such that the first switching means 10 also with the switching voltage U is driven and then the first switching contact 11 closes. Since now only the load circuit 51 is fully closed, the first switching contact 11 draws an arc, which arises for example by switching of inductive or capacitive loads on it.

To switch off the load 50, the switching voltage U is disconnected from the drive lines 4, 5, that the opening of the load circuit 51 is achieved by operating the first release means 31 such that it disconnects the first switching means 10 from the drive line 5 and during an opening process the first switching contact 11, the second release means 32 is operated such that it maintains a current flow through the second switching means 20 due to an energy storage C. Thus, the opening of the second switching contact 21 is delayed, wherein in the opening operation of the second switching contact 21 in the load circuit 51, no current flows and thus no arc can occur at the second switching contact 21.

Furthermore, the fail-safe switching module 1 has a third switching contact 13 and a fourth switching contact 24, which are arranged in a series connection to a read-back input 6 of an evaluation means 7. The evaluation means 7 is provided with a read-back function, which makes it possible to detect whether the first switching contact 11 or the second switching contact 21 is welded. For if a welding of the switching contacts 11,21 have taken place, then the respectively associated opening contact no longer open, since the example of the first switching means 10, the first switching contact 11 with the third switching contact 13 is in a mechanical operative connection. The same applies to the second switching means 20 and its switching contacts.

If the error case of "welding of the contacts" has occurred, switching on of the switching means 10, 20 can be prevented either by a higher-order control system (F-CPU) or by a corresponding monitoring system in the switching module 1. The higher-level control system would in this case be connected to a backplane bus 8, while the backplane bus 8 is connected to the evaluation means 7 and can forward the error signal to the higher-level automation system. For an error signaling on site, ie directly to the switching module, a light emitting diode LED is connected via an inversion circuit to the series circuit of the third switching contact and the fourth switching contact.

When switching the load circuit 51, wherein the load circuit 51, the load 50 has a voltage source 52 and a fuse 53, can be dispensed with a fuse as a fuse 53 using the switching module 1 according to the invention and a circuit breaker can be used instead of the fuse.

The switching module has a redundant output and is capable of switching a second load circuit 51 ', with a second load 50', a second voltage source 52 'and a second fuse 53'.

With the FIG. 2 a diagram 60 is shown to the switching behavior, which illustrates the delay of the driving of the first switching means 10 and the extension of the control of the second switching means 20 graphically. A drive behavior 63 symbolizes the switching on and off of the switching voltage U between the first drive line 4 and the second drive line 5. A first switching behavior 61 indicates the switching states of the switching means 10 again. A second switching behavior 62 indicates the switching states of the second switching means 20 again.

The two circled areas 64 each indicate the arcing. At a first time T1, the switching voltage U, see control behavior 62, is turned on. In this case, the second release means 32 is operated via the second delay circuit 32a so that a current flow through the second switching means 20 without delay is immediately possible and thus the second switching contact 21 closes. In the course of the second switching behavior 62, this is characterized by a rising edge. During the switching on of the switching voltage U, the first release means 31 is operated via the first delay circuit 31a in such a way that it interrupts a possible current flow through the first switching means 10 for a time period ΔT to a second time T2. At the second time T2, the first release means 31 is operated so that a current flow through the first switching means 10 is possible, so that the first switching contact 11 close. Since now the load circuit 51 is completely closed, the first switching contact 11 is an arc, which is characterized in the diagram by the arc region 64.

In a shutdown at a third time T3, the switching voltage U is turned off, which can be seen in the control behavior 63 as a falling edge. Here, the first release means 31 is operated such that it immediately interrupts a possible current flow between the first drive line 4 and the second drive line 5 via the first switching means 10 and the first release means 31. This opens the first switching contact 11 and in turn attracts an arc, which in turn is characterized as an arc region 64.

As according to FIG. 1 between the first drive line 4 and the second drive line 5, an energy store C is arranged as a buffer capacitor, this energy store C maintains a current flow through the second switching means 20 and the second release means 32 for a time .DELTA.T up to a fourth time T4. In this case, the second release means 32 is operated via the second delay circuit 32a such that the current can flow from the energy store C for the time ΔT.

The period ΔT is preferably in the millisecond range, preferably it lasts 10 ms. By means of a corresponding configuration of the first and second delay circuits 31a, 32a, the time ranges ΔT, which in FIG. 2 are uniformly presented, also be adapted differently.

Claims (12)

Fail-safe switching module (1) for switching a load (50) to a first switching means (10) having a first switching contact (11),
a second switching means (20) having a second switching contact (21),
wherein between a first terminal (2) and a second terminal (3), the first switching contact (11) and the second switching contact (21) are arranged in a series connection to a load circuit (51) by driving the switching means (10, 20) close, wherein the switching means (10, 20) between a first drive line (4) and a second drive line (5) are arranged,
characterized in that the first switching means (10) is arranged in series with a first release means (31) between the drive lines (4,5), wherein the first release means (31) is arranged to delay the driving of the first switching means (10) , Fail-safe switching module (1) according to claim 1, wherein the first release means (31) is connected to a first delay circuit (31a). Fail-safe switching module (1) according to claim 1 or 2, wherein the second switching means (20) in a series circuit with a second release means (32) between the drive lines (4,5) is arranged, wherein the second release means (32) is configured, the Driving the second switching means (20) to extend. Fail-safe switching module (1) according to one of claims 2 or 3, wherein the second release means (32) is connected to a second delay circuit (32a). Fail-safe switching module (1) according to one of claims 1 to 4, wherein between the drive lines (4,5) an energy storage (C), in particular a buffer capacitor, arranged to extend the driving of the second switching means (20). Fail-safe switching module (1) according to one of claims 1 to 5, wherein the first switching means (10) has a third switching contact (13) and the second switching means (20) has a fourth switching contact (24), wherein the first and the second switching contact (11 , 21) as a make and the third and the fourth switching contact (13,24) are designed as an opener. Fail-safe switching module (1) according to claim 6, wherein the third switching contact (13) and the fourth switching contact (24) in a series circuit to a readback input (6) of an evaluation means (7) are arranged, wherein the read-back input (6) as an inverting input is designed. Fail-safe switching module (1) according to one of claims 1 to 7, comprising a backplane bus (8) designed for the modular construction of a plurality of electronic modules juxtaposed decentralized automation system. Method for operating a fail-safe switching module (1) according to one of the preceding claims, wherein for switching the load (50) to the first drive line (4) and to the second drive line (5) a switching voltage is applied, closing the load circuit (51) is prepared by the second switching contact (21) by driving the second switching means (20) with the switching voltage (U) is closed and after completion of a closing operation of the second switching contact (21) the first release means (31) is operated such that the first switching means (10) also with the switching voltage (U) is driven and then the first switching contact (11) closes. The method of claim 9, wherein for switching off the load (50), the switching voltage (U) from the Ansteuerleitungen (4,5) is opened, the opening of the load circuit (51) is achieved in that the first release means (31) is operated such that it separates the first switching means (10) from the drive line (5) and after completion of an opening operation of the first switching contact (11 ) the second release means (32) is operated such that it maintains a current flow through the second switching means (20) due to the energy storage (C). The method of claim 9 or 10, wherein simultaneously with the closing of the first switching contact (11), a third switching contact (13) is opened and simultaneously with the closing of the second switching contact (12), a fourth switching contact (24) is opened, wherein by means of the series circuit the third and fourth switching contact (13,24) a readback signal for a readback input (6) is generated. Method according to one of claims 9 to 11, wherein when switching and switching off the load circuit (51), which the load (50), a voltage source (52) and a fuse (53), a circuit breaker is used instead of a fuse.

Images