GB2111751A

GB2111751A - Switching device with solenoid-operated main and auxiliary switch gear in parallel

Info

Publication number: GB2111751A
Application number: GB08230913A
Authority: GB
Inventors: Hubert Laurenz Naimer
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-11-03
Filing date: 1982-10-28
Publication date: 1983-07-06
Also published as: DK482482A; JPH0354406B2; FR2515867A1; FI823709A0; SE446676B; AU559258B2; FR2515867B1; NL8204140A; ATA471181A; FI73100B; FI73100C; DE3240053C2; AT374618B; DE3240053A1; DK158176B; GB2111751B; AU9003882A; SE8206154L; CA1190310A; CH661148A5

Abstract

Each contact of the auxiliary switchgear is in series with an electronic switch which closes the parallel path after closure of the auxiliary contacts. When the main contacts have closed the electronic switch and thereafter the auxiliary contacts are opened. The switching sequence is controlled in response to ON and OFF buttons 10 and 11 through memory 15 by selection circuits 16 for the auxiliary switchgear, 17 for the electronic switch, and 18 for the main switchgear. A test circuit 19 has inputs from sensors 20, 7, 21, 22, 23 monitoring respectively current flow in the main switchgear solenoid, position of the main contacts, state of the electronic switch, current flow in the auxiliary switchgear solenoid and position of the auxiliary contacts. Resettable tuners 25, 26, 27 delay operation of 16, 17 and 18 to allow time for tested conditions to settle down but if a fault is detected on test this is shown by warning circuit 24. <IMAGE>

Description

SPECIFICATION Switching device The invention relates to a switching device for opening and closing electrical circuits, in which, parallel to each contact, located in the main circuit to be switched, of a magnet-controlled switchgear, an electronic switch and a contact, serving as an isolator, of a further magnet-controlled auxiliary switchgear are connected in series, and there is a central control device which connects through the electronic switch before each change in switching state of the magnet-controlled switchgear located in the main circuit and which then blocks it again, the contacts of the auxiliary switchgear which are in series with the electronic switch being closed.

A switching device of this type became known, for example, from U.S. Patent Specification 4,251,845. In this known device, the three switching elements are selected via a series of auxiliary relays, the switching sequence of which is predetermined by contacts inserted in their selection circuits. Here, this selection is influenced, apart from by a switching-on or switching-off command, solely by an auxiliary contact of the magnet-controlled switchgear located in the main circuit, this auxiliary contact allowing the further progress of the switching sequence during both switching-on and switching-off.

The disadvantage of this device is that the switching-on time of the electronic switch has to be made relatively long because of the tolerances of the operating and releasing times of the auxiliary relays, with the result that the electronic switch has to absorb a correspondingly large power loss and has to be chosen accordingly. Moreover, in the known case, when the main circuit is opened the switching sequence depends on releasing delays produced by capacitors connected in parallel to the coils of auxiliary relays, with the result that because of changes in capacitance of the capacitors during the operating time there can arise faulty switching operations which can iead to destruction, especially of the electronic switch.

The object of the invention is to propose a switching device of the type mentioned in the introduction, in which faulty selection of the three switching elements is safely prevented.

This is achieved, according to the invention, due to the fact that there is a central control unit which has for each of the switching elements a separate selection circuit, and these selection circuits comprise test loops connected to sensors monitoring the switching state of the switching elements and/or their selection and are linked to one another preferably in dependence on the command transmitted from the central control unit.

It is thereby possible to proceed further in the switching sequence only as soon as the preceding switching command has been made. This also makes it possible, however, to do away with safety intervals between the individual switching steps, such as are required in the known case, with the result that despite increased safety a reduction in the switching-on time of the electronic switch is achieved.

It is especially appropriate if, in order to monitor the position of the contacts of the magnet-controlled switchgear which are located in the main circuit, there is an auxiliary contact which ensures that the switching sequence is continued only when the contacts located in the main circuit are actually closed.

According to a further feature of the invention,the switching state of the electronic switch is monitored by a sensor responding to its control current, and the selection of the electronic switch is preferably linked to that of the magnet-controlled auxiliary switchgear, and when the selection ofthe electronic switchgear has ended a signal is triggered, this signal triggering via a delay element a command to open the contacts of the auxiliary switchgear. This ensures that, as distinct from the known solution according to U.S. Patent Specification 4,251,845, the electronic switch is isolated from the main circuit at the mains.In this way, the electronic switch is very largely protected on the load side against the effect of surges or short-circuits which can result in the contacts being torn open because of the current forces in the region of the contractions of the current paths caused by the contact points, and under certain circumstances the arcs which are formed may be extinguished and high induction voltages may consequently arise.

The invention is explained in more detail with reference to the drawing. In this, Figures 1 and 2 show diagrammatically two different embodiments of a switching device according to the invention for connecting a load to or disconnecting from a network with a phase sequence which is always the same, Figure 3 shows a switching device for connecting or disconnecting a load with a selective phase sequence, Figure 4 shows a block diagram of a control unit for a switching device according to Figures 1 or 2, and Figure 5 shows a block diagram of a control unit for a switching device according the Figure 3.

The magnetically controlled switchgear 1,1' has contacts 4which are located in the main circuit and which control the connection of the mains terminals L1, L2, L3 to the load 5. Connected in parallel to each of the contacts 4, 4' is a series connection consisting of a contact 6, 6', acting as an isolator, of an auxiliary switchgear 2, 2', and an electronic switch 3.

According to Figures 2 and 3, there are, for monitoring the switching function of the switchgears 1, 1' or auxiliary switchgears 2, 2' auxiliary contacts 7, 7' and 8, 8' respectively, which, like the switchgear 1, 1' and the auxiliary switchgears 2, 2' and the electronic switch 3, are connected to a central control unit 9.

This control unit 9 is supplied from the mains via a phase L1 and the neutral conductor and is wired to the conventional on-and-off buttons 10, 10' and 11 respectively. A fault-warning device 12 is likewise connected to the central control 9.

In the embodiment according to Figure 1, current transformers 13, 14 are provided for monitoring the switching function of the switchgear 1 or the auxiliary switchgear 2 and the electronic switch 3, and of course current transformers can also be arranged in each phase to achieve more precise monitoring.

When, in the switching device according to Figures 1 or 2, a switching-on command is transmitted to the central control unit 9 by pressing the ON button 10, then after the checking of a test loop the selection circuit for the auxiliary switchgear 2 is activated and the contacts 6 of the latter are closed.

After the return signal has arrived via the closing of the contacts 6 by means of the auxiliary contact 8, the selection circuit of the electronic switch 3 is activated and the latter is connected through. In this way, the load 5 is connected to the mains L1, L2, L3 via the parallel current path. After that, the selection circuit of the magnet-controlled switchgear 1 is activated, so that the latter closes its contacts 4.

After the return signal has arrived via the closing of the contacts 4 of the switchgear 1 by means of the auxiliary contact 7 or the current-transformer 13, the electronic switch 3 is blocked, and thereafter the selection circuit of the auxiliary switchgear 2 is reset again so as to open the contacts 6 of the auxiliary switchgear 2 again. Of course, instead of only one phase, all three phases can be monitored by currenttransformers 14.

When the OFF button connected in front of the ON button 10 is pressed, with the result that a switchingoff command triggered by pressing the OFF button has priority over a switching-on command, then the selection circuit of the auxiliary switchgear 2 is activated and the contacts 6 are closed. After the return signal has been transmitted via the closure of the contacts 6, but at the latest after the expiry of a specific time, the selection circuit of the electronic switch 3 is activated so that the latter passes into its conductive state.

As soon as the return signal arrives via the through-connection of the electronic switch 3, but at the latest at the expiry of a specific time, the selection circuit of the switchgear 1 is reset so as to open the contacts 4. When this has taken place, the selection circuit of the electronic switch 3 is reset, and the electronic switch 3 passes into its blocked state, the selection circuit of the electronic switch 3 being reset at the latest after the expiry of a specific time.

After the selection circuit of the electronic switch 3 has been reset, the selection circuit of the auxiliary switchgear 2 is then reset, so that its contacts 6 open and the switching-off cycle is completed.

In the embodiment according to Figure 3, the switching-on and switching-off cycle takes place in the same way. Here, depending on whether the ON button 10 or 10' is pressed, the auxiliary switchgear 2 or 2' is selected, as a further sequence of the switchgear 1 or 1', with closure of the contacts 6 or 6' and 4' or 4' respectively.

Before the appropriate selection of the auxiliary switchgear 2 or 2', however, a test is conducted in the test circuit as to whether none of the coils of the switchgears 1, 1' and auxiliary switchgears 2, 2' is energised and none of the contacts 4, 4' and 6', 6' is closed. Moreover, the selection circuits of the auxiliary switchgears 2, 2' and the switchgears 1, 1' are mutually locked, so that as soon as a switching-on signal arrives at the selection circuit of, for example, the auxiliary switchgear 2 a blocking signal is transmitted to the selection circuits of the auxiliary switchgear 2' and the switchgear 1', with the result that these can be activated only after a switching-off command and a subsequent switching-on command triggered by pressing the ON button 10'.

By arranging the electronic switch 3 on the load side of the auxiliary switchgears 2, 2' connected in parallel, it is possible to make do with a single electronic switch 3 for both parallel circuits to the contacts 4, 4' of the switchgears 1, 1'.

A block diagram of a central control unit 9 for a switching device according to Figures 1 or 2 is shown in Figure 4, a representation of the voltage supply having been omitted.

The commands entered in the central control unit via the ON and OFF buttons 10,11 are stored in the memory 15, the output of which is connected to each of the selection circuits 16, 17, 18 which are each assigned to one of the switching elements of the switchgear, specifically to the auxiliary switchgear 2, the electronic switch 3 and the switchgear 1. Furthermore, the output of the memory 15 is also connected to a test circuit 19.

The test circuit 19 is also connected, moreover, to a sensor 20 responding to a current flow through the coil of the magnet-controlled switchgear 1, a sensor monitoring the position of the contacts 4 of the switchgear 1, for example a sensor 7, 13 connected to an auxiliary contact 7 our a current-transformer 13, and a sensor 21 which monitors the switching state of the electronic switch 3 and which responds, for example, to the supply of the ignition electrode of the electronic switch 3 and/or also to a current flow through the parallel circuit. The test circuit 19 also receives signals from the sensor 22 responding to the current flow through the coil of the auxiliary switchgear 2 and from a sensor 23 monitoring the switching state of the contacts 6.

When a switching-on command reaches the test circuit 19, the lattertransmits a switching command to the selection circuit 16 of the auxiliary switchgear 2, if no current flows through the coils of the switchgear 1 or the auxiliary switchgear 2 and their contacts 4 or 6 respectively are in the open position and the electronic switch 3 is also in its blocked state.

If this is not so, the switching-on command to the selection circuit 16 of the auxiliary switchgear 2 is discontinued, and a signal for activating the fault warning circuit 24 is transmitted.

The switching-on command to the selection circuit 16 is simultaneously applied to a resettable timing element 25 which is connected to a resetting input of the selection circuit 16 and which, after the end of its operating time, transmits a signal to the resetting input of the selection circuit 16 so as to reset this again. At the same time, this signal also activates the fault warning circuit 24 which controls, for example, the lamp 12.

However, operation of the timing element 25, which is also connected to the sensor 23 monitoring the contacts 6 of the auxiliary switchgear 2, is discontinued if the closing of the contacts 6 is signalled within the operating time of the timing element 25.

As soon as the closing of the contacts 6 of the auxiliary switchgear 2 is signalled to the selection circuit 16 connected to the sensor 23, this selection circuit transmits a switching-on command to the selection circuit 17 controlling the electronic switch 3, this switching-on command being delayed via a timing element 26 so as to prevent through connection of the electronic switch 3 during any rebound of the contacts 6. When the switching-on command from the selection circuit 16 arrives at the selection circuit 17 connected to the sensors 7, 13 and 21 as well as 23, this tests whether the contacts 4 are still open, but the contacts 6 are closed. If this is the case, the control electrode of the electronic switch 3 is subjected to ignition pulses or a continuous signal and is thus kept in the connectedthrough state.If the above conditions are not satisfied, the control electrodes of the electronic switch 3 cease to be so subjected, and the fault warning circuit 24 is activated. At the same time, a command to open the contacts 6 is given to the selection circuit 16 of the auxiliary switchgear 2.

The fault-warning circuit 24 is activated and the command to open the contacts 6 is transmitted to the selection circuit 16 even when signals do not arrive at the control electrode of the electronic switch 3 within a specific time after the arrival of the switching-on signal in the selection circuit 17 or even when no current flows in the parallel circuit, this being monitored by the sensor 21 connected to the selection circuit 17. In this case, resetting of the selection circuit 17 also takes place.

If, on the other hand, a signal corresponding to the proper through-connection of the electronic switch 3 arrives from the sensor 21, the selection circuit 17 transmits a switching signal to the selection circuit 18 which is assigned to the switchgear 1, the switchgear 1 being stressed towards closure of the contacts 4 as a rsult of the switching-on signal coming from the memory 15. At the same time, this signal arrives art a resetabletiming element 17, the output of which is connected to a resetting input of the selection circuit 18 and the fault-warning circuit 14.When a signal corresponding to the closed contacts 4 of the switchgear 1 reaches the timing element 27 within the operating time of the timing element 27, the latter is reset and there is no transmission of a resetting signal to the selection circuit 18 and a signal for activating the fault warning circuit 24.

In the opposite case, resetting of the selection circuit 18 and activation of the fault-warning circuit 24 take place and, via the timing element 28 which is connected to the output of the timing element 27 and to a resetting input of the selection circuit 17, resetting of the selection circuit 17, with the result that the electronic switch 3 passes into the blocked state.

If, however, a signal corresponding to the closed contacts 4 arrives at the timing element 27 and the selection circuit 18 in due time, the latter transmits to the selection circuit 17 a command to block the electronic switch 3.

As soon as the return signal from the sensor 21 arrives, via the blocking of the electronic switch 3, at the control circuit 17, the latter transmits to the selection circuit 16, via the timing element 26, a signal to open the contacts 6 of the auxiliary switchgear 2. If no return signal of this type arrives within a specific time, the fault-warning circuit 24 is activated and the signal for opening the contacts 6 is transmitted to the selection circuit 16.

The latter passes the command to open the contacts 6 on to the auxiliary switchgear 2 and checks whether a signal corresponding to the opened contacts 6 arrives from the sensor 23 within a specific time. If this does not happen, the selection circuit 16 transmits a signal activating the fault warning circuit 24, but the command to open the contacts 6 is maintained and is not reset.

When a switching-off command reaches the central control unit because the OFF button 11 has been pressed, this command is stored in the memory 15, and the latter transmits at its output a corresponding signal which reaches the test circuit 19 and the selection circuits 16, 17 and 18 again.

The test circuit 19 checks whether the contacts 4 of the switchgear 1 are closed and the electronic switch 3 is blocked. If this is not so or if this does not occur within a specific time, the fault-warning circuit 24 is activated. In either case, however, a command to close the contacts 6 of the auxiliary switchgear 2 is transmitted to the selection circuit 16, and the resetting input connected to the timing element 25 is inactivated by the swtiching-off signal coming from the memory 15. Furthermore, when there is a switching-off signal coming from the memory, after a specific time the transmission of a switching-on command to the selection circuit 17 is triggered, irrespective of whether the sensor 23 supplies or does not supply within a predetermined time a signal corresponding to the closed contacts 6.

However, should a signal of this type not arrive, the fault-warning circuit 24 is activated after the operating time ofthe timing element 25.

The switching-off signal coming from the memory 15 also ensures that, even when there is no signal corresponding to the closed contacts 6, at the arrival of the switching-on command from the selection circuit 16 the selection circuit 17 brings the electronic switch 3 into the connected-through state and transmits a switching signal to the selection circuit 18 which controls the switchgear 1 by opening the contacts 4 as a result of the switching-off signal coming from the memory.

When a signal correspnding to the open contacts 4 is supplied from the sensor 7, 13, the selection circuit 18 transmits to the selection circuit 17 of the electronic switch 3 a signal to block the latter.

However, if this signal does not appear, the timing element 27 operates, and the fault-warning circuit is activated and after the operating time of the timing element 28 a block signal arrives at the selection circuit 17.

The electronic switch 3 is consequently blocked, and after the arrival from the sensor 21 of a signal corresponding to the proper blocking of the eiectronic switch 3 or after the expiry of a predetermined time a signal to open the contacts 6 of the auxiliary switchgear 2 is transmitted from the selection circuit 17 to the selection circuit 16, in the latter case the faultwarning circuit 24 also being activated.

The selection circuit 16 controls the auxiliary switchgear 2 for opening of the contacts 6 and checks whether a signal corresponding to the open contacts 6 arrives from the sensor 23 within a specific time. If this is not so, the fault-warning circuit 24 which can be formed, for example, by an OR gate is activated, but control of the auxiliary switchgear 2 for opening of the contacts 6 is maintained.

This ensures that the switching-off command is executed in any case, even when faults arise in the switching operations.

In the block diagram according to Figure 5, there is a memory 15 with two outputs which are interlocked as regards a switching-on command and which are each assigned to one ofthetwo ON buttons 10,10', but both assume the same switching state when a switching-off command arrives. Thus, only one of the two outputs of the memory 15 can evertransmit a switching-on signal, and this signal is maintained until the OFF button 11 is pressed, irrespective of whether one or both ON buttons 10,10' are pressed.

The test circuit 19 is connected not only to the sensors 20,7,22 and 23 monitoring the switchgear 1 and the auxiliary switchgear 2 or their contacts 4 and 6, but also to the sensors 20', 7', 22' and 23' monitoring the switchgear 1' and the auxiliary switchgear 2' and to the sensor 21 monitoring the electronic switch 3. Furthermore, the test circuit is also connected to the two outputs of the memory 15 via an OR gate 30. When a switching-on command arrives at the test circuit 19 via this OR gate 30, it checks whether no current flows through any of the coils of the switchgears 1 and 1' and the auxiliary switchgears 2 and 2' and no contacts 4 or4' and 6 or 6' are closed and whether the electronic switch 3 is also in its locked state.If these conditions are satisfied,thetest circuit 19 transmits a switching command which is fed, via one of the two AND gates 31,32 each making a link with one of the two outputs ofthe memory 15, to one ofthetwo selection circuits 16, 16' which are assigned to the auxiliary switchgear 2 and 2' respectively. At the same time, the two selection circuits are interlocked, since the outputs of the AND gates 31 and 32 respectively are connected not only to the setting input of one selection circuit 16 and 16' respectively, but also, via an OR gate 33, 34 respectively, to the resetting input of the other selection circuit 16 and 16' respectively.The two inputs are connected to the output of the timing element 25 which is connected to the sensors 7 and 7' monitoring the positions of the contacts 6 and 6' of the auxiliary switchgears 2,2' and which can be reset during its operating time by signals from one of the two sensors which correspond to the closed position of these contacts.

In the embodiment according to Figure 5, the switching-on and switching-off operation basically takes place in exactly the same way as according to Figure 4, and the fault-warning circuit 24 is also activated accordingly under the same conditions.

Like the test circuit 19, the selection circuit 17 of the electronic switch 3 is connected to the two outputs of the memory 15 via the OR gate 30.

Furthermore, the selection circuit 17 is connected to sensors 7 and 7' monitoring the position of the contacts 4 and 4' and to sensors 23 and 23' monitoring the contacts 6 and 6'. When a switchingon command arrives from the selection circuit 16 or 16' via the timing element 26, the selection circuit 17 checks whether the contacts 4 and 4' are still open and whether the contacts 6 or 6', but not both contact groups 6 and 6', are closed and only then selects the control electrode of the electronic switch 23 so that the latter is connected through.

When a signal corresponding to the connectedthrough electronic switch 3 arrives from the sensor 21 at the selection circuit 17, the latter transmits a switching signal which is fed, via one of the AND gates 35,36 second inputs of which are connected to the outputs of the memory 15, to one of the two selection circuits 18,18' which are assigned to the switchgears 1 and 1 ' resepectively.Atthesametime, the timing element 27 which can be reset by a signal corresponding to the closed contacts 4 or 4' is also started.

The outputs of the AND gates 35,36 are connected not only to the setting inputs of the selection circuits 18, 18', but also to OR gates 38 and 37 respectively, outputs of which are connected to the resetting inputs of the selection circuits 18 and 18' respectively and seconds inputs of which are connected to the ouptutofthetiming element 27.

Interlocking of the selection circuits 18 and 18' is provided again as a result.

As soon as a signal corresponding to the closed contacts 4 and 4' respectively arrives from the corresponding sensor 7 and 7' respectively at the selection circuit 18 and 18' respectively, the latter transmits to the selection circuit 17 a command to block the electronic switch 3.

The further course of the switching-on cycle takes place as in the exemplary embodiment according to Figure 4, although signals causing the contacts 6 and 6' to open are fed to both selection circuits 16 and 16' respectively.

When the two outputs of the memory 15 supply the same signals, this represents a switching-off signal, and the test circuit 19 checks whether the contacts 4 or 4' of a switchgear are closed and whether the electronic switch is blocked. In any case, a switching command is transmitted from the test circuit 19 to the two AND gates 39,40, the negated input of which is connected to the output of the OR gate 30 and can therefore connect through only in the event of a switching off command. The third inputs of these gates 39,40 are connected to the sensors 7 and 7' respectively, so that only that of the two gates 39,40 can connect through which is connected to the sensors 7 or 7' respectively which supplies a signal corresponding to the closed contacts 4 or 4' respectively.

Up to the transmission of the switching signal from the selection circuit 17 to one of the selection circuits 18 and 18', the further course of the switching-off cycle is identical to the cycle described in the explanation of Figure 4.

When a switching-off command appears at the two outputs of the memory 15, the switching signal is transferred via the AND gate 41, the inverting input of which is connected to the output of the OR gate 30 and can therefore connect through only in the event of a switching off command. The output of this AND gate 41 is connected via decoupling elements 42, 43, for example diodes, to the setting inputs of the selection circuits 18, 18', so that both control the associated switchgears 1, 1' for opening of the contacts 4,4' as a result of the switching-off command which appears.

The further steps of the switching-off cycle are the same as those described in relation to Figure 4.

Claims

1. A switching device having main contacts and auxiliary contacts in parallel, each auxiliary contact being in series with an electronic switch, and a control device which closes the electronic switch with the auxiliary contacts closed before effecting any change in the state of the main contacts and thereafter re-opens the electronic switch characterized in that the control device has separate selection circuits for the main and auxiliary contacts and for the electronic switches and these selection circuits include test loops connected to sensors which monitor the switch state and/or the selection of the main and auxiliary contacts and the electronic switches.

2. A switching device as claimed in claim 1 in which an additional contact is coupled with the main contacts for monitoring the position of the main contacts.

3. A switching device as claimed in claim 1 or 2 in which the switching stae of the electronic switch is monitored by a sensor responding to its control current.

4. A switching device as claimed in any of the preceding claims in which the trailing edge of the control pulse for the electronic switch triggers via a delay element an opening command for the auxiliary contacts.