GB2053494A

GB2053494A - A Monitoring Device for Double- pole Electrical Command Lines

Info

Publication number: GB2053494A
Application number: GB8018434A
Authority: GB
Original assignee: Schoppe and Faeser GmbH
Current assignee: Schoppe and Faeser GmbH
Priority date: 1979-06-05
Filing date: 1980-06-05
Publication date: 1981-02-04
Also published as: IT8022569A0; DE2922782C2; DE2922782A1; IT1131272B; NL8002905A; GB2053494B

Abstract

The command lines (A, B) lead from the outputs (1a and 1b) of a double-pole switching control device (1) to a control element (3) to connect the control element (3) to a supply voltage source (2) and are monitored by means of an a.c. voltage source (7) connected to the supply voltage source (2) the other connection (7) of the a.c. voltage source (7) being connected to one output (1a) of the control device (1) via a first resistor (8a) when the control device (1) is not through connected, the first resistor (8a) being of higher resistance than the series connection of the two command lines (A, B) and the control element (3). The connection point to earth of the two voltage sources (2, 7) is connected to a second output (1b) of the control device (1) via a second resistor (8b) higher in resistance than the first resistor (8a). The a.c. voltage source is not sufficient to cause the control element (3) to respond and a circuit arrangement (6) is provided, the inputs of which are connected to the connection point of the two voltage sources (2, 7) and to the outputs (1a, 1b) of the control device (1) to monitor the voltages at the outputs (1a, 1b) of the control device while taking the switching condition of the control device (1) into account. <IMAGE>

Description

SPECIFICATION A Monitoring Device for Double-pole Electrical Command Lines The invention relates to a monitoring device for double-pole electrical command lines which lead from the outputs of a double-pole switching control device to a control element which, when connected, connects the control element to a supply voltage source.

This type of monitoring device is known from German Auslegeschrift No. 1,513,297. As Figure 1 of this Auslegeschrift shows in particular, an output amplifier is connected in each case after the two outputs of a control device. A single-pole line leads from each output amplifier to a control element via a diode. Antivalent output signals are present at the outputs of the output amplifiers connected after the control device in the through connected condition and these antivalent output signals allow current flow through the control element. A monitoring device is connected to the outputs of the output amplifier and carries out a antivalent check on the output signals of the output amplifiers.This monitoring device also responds when there are errors in antivalent which have occurred due to conductive connection between one of the two lines and the supply voltage.

The invention seeks to create a monitoring device of the type stated at the outset which monitors the command lines both for a break in the line and for conductive connection with respect to the supply voltage or earth potential if there is no control command present.

According to the invention, there is provided a monitoring device for double-pole electrical command lines which lead from the outputs of a double-pole switching control device to a control element which, when connected, connects the control element to a supply voltage source wherein one connection of an a.c. voltage source is connected to a connection of the supply voltage source the other connection of the a.c. voltage source is connected to a first output of the control device via a first resistor when the control device is not through connected, and the first output connection is associated with the other connection of the supply voltage source the first resistor is higher in resistance than the series connection formed from the two command lines and the control element the connection point (earth potential) of the two voltage sources is connected to a second output of the control device via a second resistor the second output being associated with the connection point (earth potential) of the two voltage sources the second resistor is higher in resistance than the first resistor the a.c. circuit is so dimensioned that it does not allow the control element to respond and a circuit arrangement, the inputs of which are connected to the connection point (earth potential) of the two voltage sources and to the outputs of the control device, links the voltages present at the outputs of the control device while taking the switching condition of the control device into account.

The invention will now be described in greater detail, by way of example, with reference to the drawings, in which Figure 1 is a general circuit diagram of an embodiment of the monitoring device in accordance with the invention; Figure 2 is a general circuit diagram of a logic circuit for the embodiment shown in Figure 1; Figure 3 is a general circuit diagram of a second embodiment of the monitoring device in accordance with the invention, and Figure 4 is a general circuit diagram of a logic circuit for the embodiment in accordance with Figure 3.

The monitoring device shown in Figure 1 serves to monitor a double-pole command line. A double-pole switching control device 1 connects a supply voltage source 2 to a coupling relay 3, which serves as a control element, via two command lines A and B in the through connected condition, the coupling relay 3 actuating a magnetic valve not shown here for example. By closing a switch 4, a circuit is closed via the supply voltage source 2 and a relay 5. Thus the contacts 5a and 5b are closed, these contacts being normally open. Furthermore, the contact 5c, which connects the positive connection 2+ of the supply voltage source 2 to inputs of a logic circuit 6, switches over and the contact 5d is opened.

Connection 7 of an a.c. voltage source 7 is also connected to earth potential as is connection 2 of the supply voltage source 2. The output terminal 1 a of the control device 1 is connected to connection 7+ of the a.c. voltage source 7 via the contact 5d and a resistor Ba when the relay 5 is not energised. The output terminal 1 b of the control device 1 is connected to earth potential via further resistor 8b.

Resistor 8a is of high value with respect to the series connection of the command line A, the coupling relay 3 and the command line B. The resistor 8b is of high value with respect to resistor 8a. The voltages which appear at the output terminals 1 a and 1 b of control device 1 are designated UA or UB and are supplied via lines 9 or 10 to further inputs of the logic circuit 6. The switching condition of the relay 5 is supplied to the logic circuit 6 via lines 11 and 12. The potential of the connection 7+ is supplied to the logic circuit 6 via a line 13.

The supply voltage source 2 supplies a d.c. voltage of +24 V. The a.c. voltage source supplies a square wave a.c. voltage which--with regard to earth potential-alternates between 0 V or +24 V. The logic circuit 6 links signals present in digital form while a voltage ....... +5 V is associated with the signal "L" and a voltage of > +12 V is associated with the signal "H". The inputs of the logic circuit 6 are connected to earth potential internally via high value resistors so that an open input corresponds to the signal "L".

If the switch 4 is open, then a current flows from connection 7+ of the a.c. voltage source 7 via resistor 8a, contact 5d output terminal 1 a, command line A, coupling relay 3, command line B, output terminal 1 b and resistor 8b and its level is dimensioned so that it does not cause the coupling relay 3 to respond. Since, as mentioned above, the resistor 8b is selected to be of high resistance as compared to resistor 8a and the latter is selected to be at high resistance as compared to the series connection formed from command line A, coupling relay 3 and command line B, the square-wave a.c. voltage emitted by the a.c. voltage source 7 is supplied to the logic circuit 6 via the line 9 and the line 10.

Moreover, a H-signal and, the square-wave a.c. voltage are supplied to the logic circuit 6 via the lines 11 and 13 respectives. Therefore no fault is indicated when the signals on lines 9 and 10 equal the signal on line 13 when the relay 5 is not energised. If the signals on lines 9 to 1 3 are designated S9 to S13 the following logic equation may be established for the relay 5 when it is not energised: "No fault" if (S11 8 S12 # S13 & S13 # S9 & 9 & 10)V (S11 #S12 # S13 # S9 # S10) If switch 4 is closed, then a current flows from the connection 2+ of the supply voltage source 2 via contact 5a, command line A, coupling relay 3, command line B and contact 5b this current causing coupling relay 3 to respond.The voltages +24 V or O V are applied to the output terminals 1 a and 1 b.

An H-signal or an L-signal is supplied to the logic circuit 6 via the lines 9 and 10. Moreover, an H-signal is supplied to the logic circuit 6 via the line 12. Therefore there is no fault-regardless of the signal on line 13-if, when relay 5 is excited, an H-signal is present on line 9 and an L-signal on line 10.Thus the following logic equation may be established for this condition: "No fault" if S11 # S12 # S9 #S10 If the logic equations for the two operating conditions considered are combined then the following logic equations is obtained: "No fault" if (S" # S12 S12 & # S13 & 81 & ,0) V(S # S12 # S13 # S9 # S10 V(S11 # S12 # S9 # S10 Figure 2 shows an embodiment of a logic circuit which implements the above logic equation. The inputs of the logic circuit 6 connected to lines 9 to 13 are connected to earth potential via high value resistors 14 to 18 so that an L-signal is supplied to the gates connected thereafter when an input is open.The AND-gate 19 forms the expression S" s S12 S S12 S 59 # S10, AND gates 20 and 21 form the expressions s # S10 S10 and OR-gate S links the links An 0 expressions S11 # S12 # S13 & S, 12 13 9 10 S11 # S12 # S13 # S9 # S10,An OR-gate 22 links the output signals of the AND-gates 1 9 to 21. A negate 23 negates the output signal of the OR-gate 22 so that an H-signal is supplied to a lamp 24 if there is a fault.

If when switch 4 is open, a break in the wire of the command line A occurs or of coupling relay 3 or command line B, then an L-signal is supplied to the logic circuit 6 via the line 10. Each time an Hsignal occurs on line 13 an L-signal is applied to the outputs of the three AND-gates 1 9 to 21. Each time an L-signal occurs on line 13 an H-signal is applied to the output of the AND-gate 21. The lamp 24 then flashes to the beat of the a.c. voltage source 7 and provides a signal indicating that a fault has occurred.

If with switch 4 open there is a conductive connection between earth potential and command line A, coupling relay 3 or command line B, then an L-signal is continually supplied to the logic circuit 6 via the lines 9 and 10. Each time an H-signal occurs on line 13, an L-signal is applied to the outputs of the three AND-gates 19 to 21. Each an L-signal occurs on line 13 an H-signal is applied to the output of the AND-gate 21. Lamp 24 therefore flashes to the beat of the a.c. voltage source 7 and signals to indicate that a fault has occurred.

If, with switch 4 open, there is conductive connection between the +24 V line and command line A, coupling relay 3 or command line B, then an H-signal is supplied continually to the logic circuit 6 via lines 9 and 10. Each time an L-signal occurs on line 1 3 an L-signal is supplied to the outputs of the three AND-gates 19 to 21. Each time an H-signal occurs on line 13 an H-signal is supplied to output of the AND-gate 20. The lamp 24 therefore flashes to the beat of the a.c. voltage source 7 and signals indicating that a fault has occurred.

Faults which occur while the switch 4 is actuated are indicated at the latest when the switch 4 is next opened-as described above. Connection between the command lines A and earth potential is indicated as is connection between command line B and the +24 V line even during actuation of switch 4. With connection between command line A and the +24 V line and with connection between command line B and earth potential occurring during actuation of the switch 4 "non dangerous errors" and this is indicated as switch 4 is opened. A break in the wire while the switch 4 is actuated is indicated either by a further safety device monitoring the functioning of the control element when the switch 4 is switched on or, at the latest, when the switch 4 is opened.A break in a current-carrying command line may be monitored by a current measuring device connected in series with the command line the output signal of which is supplied to the logic circuit as additional information.

A monitoring device is shown in Figure 3 which monitors command lines with double-pole switching leading to two coupling relays serving as control elements. If a motor, for example an adjustable valve drive is driven then a coupling relay is required for each direction of rotation. As in Figure 1 the command lines A and B lead to the coupling relay 3 which is associated with the opening process. The command lines B and C lead to the second coupling relay 25 which is associated with the closing process and command line B is the common return line of coupling relays 3 and 25 which are connected together. By closing a switch 26, a circuit is closed by means of the supply voltage source 2 and a relay 27. Thus the contacts 27a and 27b are closed; normally they are open.Furthermore, contact 27c which connects the positive connection 2+ of the supply voltage source 2 to two other inputs of the logic circuit 6 is switched over. The voltage present at the output terminal 1 c of the control device 1 is designated Uc and supplied to the logic circuit 6 via a line 28. The switching condition of the relay 27 is supplied to the logic circuit 6 via lines 29 and 30.

In the following explanation we have started from the situation in which switches 4 and 26 are locked with respect to each other so that the two switches cannot be actuated simultaneously.

If switches 4 and 26 are open then a current flows from connection 7+ of the a.c. voltage source 7 via resistor 8a, contact 5d output terminal 1 a command line A, coupling relay 3, command line B, output terminal 1 b and resistor 8b, and the level of this current is dimensioned so that it does not cause the coupling relay 3 to respond. The square-wave a.c. voltage emitted by the a.c. voltage source 7 is supplied to the logic circuit 6 via the lines 9, 10, 13 and 28. Furthermore, an H-signal is supplied to the logic circuit 6 via the lines 11 and 29. There is no fault if the signals on lines 9, 10 and 28 are equal to the signal on line 13 when relays 5 and 27 are at rest.If a distinction is made between the signals on the different lines by the reference symbols for the related lines then, for the rest condition of relays 5 and 27 the following logic equation is established: "Nofault" if (811 # S12 # S29 # S30 # S13 # S9 # S10 # S28) V(S11 # S12 # S29 # s30 # S13 # S9 # s10 # S28) If only switch 4 is closed, then a current flows from connection 2+ of the supply voltage source 2 via the contact 5a, command line A, coupling relay 3, command line B and contact 5b and causes the coupling relay 3 to respond. The voltages +24 V or O V are applied to the output terminals 1 a and 1 b.

An H-signal or an L-signal is supplied via lines 9 and 10 to the logic circuit 6. A current which does not cause coupling relay 25 to respond flows from connection 7+ of the a.c. voltage source 7 via resistor 8a, contact 5d, output terminal 1 c, command line C, coupling relay 25, command line B and switch 5b, which bypasses the resistor 8b. Since resistor 8a has a higher resistance than the series connection of command line B, coupling relay 25 and command line C, an L-signal is supplied to the logic circuit 6 via line 28.If switch 4 is closed and switch 26 is opened, then the following logic equation may be set up: "No fault" if S11 # S12 # S29 # S30 # S9 # S10 # S28 If only switch 26 is closed, then a current which causes coupling relay 25 to respond flows from connection 2+ of the supply voltage source 2 via contact 27a command line C, coupling relay 25, command line B and contact 27b. The voltage +24 V or O V are applied to the output terminals 1 c and 1 b. An H-signal or an L-signal is supplied to the logic circuit 6 via lines 28 and 10. A current which does not cause coupling relay 3 to respond flows from connection 7+ of the a. c. voltage source 7 via resistor 8a, contact 5d, output terminal 1 a, command lines A, coupling relay 3, command line B and contact 27b, which bypasses resistor 8b.Since resistor 8a has a higher resistance than the series connection of command line A, coupling relay 3 and command line B, an L-signal is supplied to the logic circuit 6 via the line 9. If the switch 26 is closed and switch 4 is open, then the following logic equation may be established: "No fault" if S11 # S12 # S29 # S30 # S9 # S10 # S28 If the logic equations for the three operating conditions considered are combined, then the following logic equation is provided:: "No fault" if (S11 # S12 # S29 # S30 # S13 # S9 # S10 # S28) V(S11 # S12 # S29 # S30 # S13 # S9 # S10 # S28) S30 ~13 ~10 '28' V\ t1 t2 29 30 8 S9 8 S1o 8 S28) V(S11 # S12 # S29 # S30 # S9 # Sg 8 Sto s S28) Figure 4 shows an embodiment of a logic circuit which implements the above-mentioned logic equation. The inputs of the logic circuit 6 connected to lines 9 to 13 or 28 to 30 are connected to earth potential via high value resistors 14 to 18 or 31 to 33 so that with an open input, an L-signal is supplied to the gates connected after the inputs. The signals are linked by four AND-gates 34 to 37, an OR-gate 38 and the negater 23.The AND-gate 34 forms the expression Sr & 812 s S29 s S30 8 & 813 8 Sg # S10 8 & 28 and the AND-gate 35 forms the expression S11 s 812 S S28 8 & 30 s S13 & 9 & 810 Er 839.

The AND-gates 36 and 37 form the expressions S, s S12 s 829 & 30# S30 # 89 1 S10 8 & 28 and S11 & 128 S12 S S,, 8 S,, Sg s S, W9 & & 828. The OR-gate 38 links the output signals of the AND-gates 34 to 37. The negater 23 negates the output signal of the OR-gate 38 so that an H-signal is supplied to the lamp 24 if there is a fault.

If in Figure 3 with switches 4 and 26 open there is a break in the wire of command lines A, B, C, or in the coupling relays 3, 25 then an L-signal is permanently continuously supplied to the logic circuit 6 via at least one of lines 10 and 28. In the case of a break in the wire between the output terminal 1 a and the connection point of the relays 3 and 25, lines 10 and 28 pass an L-signal. With a break in the wire between the output terminal 1 b and the connecting point of the coupling relays 3 and 25, the line 10 passes an L-signal and with a break in the wire between the output terminal 1 c and the connecting point of the coupling relays 3 and 25 the line 28 passes an L-signal. Each time an H-signal occurs on line 13, an L-signal is supplied to the output of the four AND-gates 34 to 37.Each time an L-signal occurs on line 13 an H-signal is applied to the output of the AND-gate 35. The lamp 24 therefore flashes to the beat of the a.c. voltage source 7, signalling that a fault has occurred.

If in Figure 3, with switches 4 and 26 open, there is a connection between earth potential and one of the command lines A, B, C or one of the coupling relays 3,25 then an L-signal is supplied continuously to the logic circuit 6 via lines 9, 10 and 28. Each time an H-signal occurs on line 13 an L signal is applied to the outputs of the four AND-gates 34 to 37. Each time an H-signal appears in line 13 an H-signal is applied to the output of the AND-gate 35. The lamp 24 therefore flashes to the beat of the a.c. voltage source 7, signalling that a fault has occurred.

If in Figure 3, with switches 4 and 26 open, there is a connection between the +24 V line and - one of the command lines A, B, C or one of the coupling relays 3,25, then an H-signal is supplied continuously to the logic circuit 6 via lines 9, 10 and 28. Each time an L-signal occurs on line 13, an L signal is applied to the outputs of the four AND-gates 34 to 37. Each time an H-signal occurs on line 13, an H-signal is applied to the output of the AND-gate 34. The lamps 24 therefore flashes to the beat of the a.c. voltage source 7, signalling that a fault has occurred.

Faults which arise during actuation of one of switches 4 or 26 are indicated by signalling, at the latest, during the next opening of the switch-as already described. A break in the wire of the command line B or of the command lines A or C which are not through connected and connection between the +24 V line and command line B or the command line A or C which are not through connected and connection between earth potential and the +24 V conducting command line A or C has already taken place during actuation of the switch 4 or 26. With connection between a command line A or C conducting +24 V and the +24 V line or connection between earth potential and command line B and the command line A or C which are not through connected there is a "non-dangerous error which is indicated by signalling when the switch opens. A break in the wire of a command line conducting +24 V is signalled either by a further safety device monitoring the functioning of the regulating unit when switched on or at the latest when the switch is opened.

The break in a current-carrying command line may be monitored by a current-measuring device connected in series with the command line and the output signal of this current-measuring device may be supplied to the logic circuit as additional information.

By converting the logic equations according to the calculation rules of algebra for switching technology a different construction of the logic circuit 6 is obtained. It is also possible to implement the logic circuit 6 by means of digital computers programmed in accordance with the logic equations.

Claims

1. A monitoring device for double-pole electrical command lines which lead from the outputs of a double-pole switching control device to a control element which, when connected, connects the control element to a supply voltage source, wherein one connection of an a.c. voltage source is connected to a connection of the supply voltage source the other connection of the a.c. voltage source is connected to a first output of the control device via a first resistor when the control device is not through connected, and the first output connection is associated with the other connection of the supply voltage source the first resistor is higher in resistance than the series connection formed from the two command lines and the control element the connection point (earth potential) of the two voltage sources is connected to a second output of the control device via a second resistor, the second output being associated with the connection point (earth potential) of the two voltage sources the second resistor is higher in resistance than the first resistor the a.c. circuit is so dimensioned that it does not allow the control element to respond: and a circuit arrangement the inputs of which are connected to the connection point (earth potential) of the two voltage sources and to the outputs of the control device, links the voltages present at the outputs of the control device while taking the switching condition of the control device into account.

2. A monitoring device according to Claim 1, wherein said other connection of the a.c. voltage source is connected to a further input of the circuit arrangement.

3. A monitoring device according to Claim 1 or Claim 2, wherein the common command line is connected to the output of the control device (1), which is associated with the connection point (earth potential) of the two voltage sources in order to monitor the electrical command lines which lead to more than one control element while a connection respectively of each control element is connected to the control device via a common command line; and the a.c. voltage is supplied to one command line respectively which is not acted upon by the supply voltage.

4. A monitoring device according to any one of the preceding claims, wherein the supply voltage is a d.c. voltage; and the a.c. voltage is a square-wave voltage the amplitude of which is equal to the amplitude of the d.c. voltage.

5. A monitoring device according to any one of the preceding claims wherein the inputs of the circuit arrangement are connected to earth potential via a resistor in each case.

6. A monitoring device for double-pole electrical command lines substantially as described herein with reference to the drawings. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~