EP2826052A1

EP2826052A1 - Safety relay circuit

Info

Publication number: EP2826052A1
Application number: EP13709093.2A
Authority: EP
Inventors: Fabian Zink
Original assignee: Phoenix Contact GmbH and Co KG
Current assignee: Phoenix Contact GmbH and Co KG
Priority date: 2012-03-13
Filing date: 2013-03-12
Publication date: 2015-01-21
Anticipated expiration: 2033-03-12
Also published as: US20150016007A1; WO2013135719A1; EP2826052B1; DE102012004843A1

Abstract

The invention relates to a safety relay circuit, in particular having two relay switches (k1, k2) connected in series or in parallel in a load circuit (LN). A switch-position indicating circuit (A1) is associated with the relay switch (k1). An evaluating circuit compares the command input to the relay (k1) with the indication of the indicating circuit (A1), whereby error states occurring at the relay switches can be detected.

Description

Safety relay circuit

description

The invention relates to a circuit arrangement for switching a load circuit in safety technology, with error states of the relay to be detected. In particular, the power switch of the

Load circuit ("switch-off safety relay circuit") or switch-on ("switch-on

Safety relay circuit ") of the load circuit

to be sure. In order to safely comply with the open position of a load circuit, electromagnetic relays are preferably used. In safety technology, the

Checked switching position of mechanical switching contacts, where it is known (EP 1 202 313 AI), a high-frequency signal to the control circuit with the switch to be tested

to apply and the switch position with a

Detect high-frequency detector. To increase the

Safety, it is also already known to arrange two relay switches in a row in the load circuit. The

Checking the switch position by means of a

However, high-frequency control circuit is complex and does not recognize certain error conditions. So can the

Relay switch take its open position, which is detectable, but if it is by a foreign body or by metal break a bridge between the

Make contact and the normally closed contact of the relay switch comes off, this error condition can not be determined with the known device. The invention has for its object to provide a safety relay circuit, in which

Error states can be reliably detected at the relay switch. In particular, the powerless circuit of a load circuit, or switching on the

Load circuit, can be brought about safely.

According to the invention, a monitoring circuit is provided which the command input to an electromechanical relay with a relay switch position or the

Relay switch state indicating circuit logically linked and from an error-error signal wins. To the electroless circuit of the load circuit

be ensured in the invention the

Relay switch of two relays connected in series in the load circuit. So if one of the switches his

Opening state not reached, but then causes the other relay switch that the current path has been switched to the load de-energized.

To ensure the switching on of the load circuit, the relay switch of two relays in the load circuit are connected in parallel with each other in the invention. Thus, if one of the switches does not reach its closed state, then the other relay switch causes the current path to close to the load. In terms of safety technology, it must be required that faults are detected, even if they do not immediately lead to a faulty circuit, because the fault in one of the relay switches is cured by the correct operation of the other relay switch. At each

Relay switch is a display circuit is provided, however, is able to detect disturbances due to erroneous bridging at the relevant relay switch by current detection means.

In the preferred embodiment, each has

Display circuit on a light emitting diode, which is operated via an associated auxiliary power source. In the

When the appropriate relay switch is open, the corresponding LED illuminates fully, signaling the correct state of the switch in the idle state

Circuit. In contrast, if the load circuit is active and there is no fault in the relay switches, then the LEDs are switched dark.

If in the turn-off safety relay circuit in the currentless circuit of the load circuit, one of the series-connected relay switch should not fall off, such as because the contacts are welded, then the

associated display circuit is not closed and the associated LED remains dark. This is detected as an error in the relay in question and it can be prevented that the load circuit is turned on again.

When in the switch-off safety relay circuit at

Activating the load circuit a fault occurs in one of the relays such that all three

Terminal contact points of the faulty relay switch are electrically connected to each other, then the associated LED lights up due to operation through the Auxiliary voltage source and it is possible to turn off the load circuit by switching the non-faulted relay. This can be done within one

Safety time happen.

A fault in the switch-off safety relay circuit can also when the load circuit is de-energized

occur, namely that in one of the display circuits, the current flow of the auxiliary power source is disturbed and the LED does not light properly. As a result, it can be recognized that the relevant relay is no longer safe. The switching on of the load circuit can be prevented. If in the switch-on safety relay circuit, one of the relay switches with the contact point of

Monitor circuit welded ("hanging contacts") should be or if one of the relay switch a "three-point contact bridging" sets, then this is when interrogating the display circuit due

Illumination of the LED detected. The safe one

Switch-on state of the load circuit is maintained via the undisturbed, parallel-connected relay. If in the switch-on safety relay circuit at one of the relay switches the switchless contacts

faulty bridged ("two-point contact bridging") then this is when switching on the

faulty relay detected. The load current can possibly lead to an overload of the current detection means, which can be averted by a fuse ("polyfuse"). Embodiments of the invention will be described with reference to FIGS

Drawing described. 1 shows a safety relay circuit in the idle state,

2 in the active state,

3 in error state I (suspended or welded contacts)

4 in fault state II (three-point contact bridging) FIG. 5 in fault state III (two-point contact bridging)

6 shows a switch-off safety relay circuit according to the invention,

Fig. 7 is a schematic representation of

Display circuits of the switch-off safety relay circuit in the idle state of

Load circuit,

8 shows the switch-off safety relay circuit in the active state of the load circuit,

9 shows the switch-off safety relay circuit in an error state I,

Fig. 10, the switch-off safety relay circuit in a Fault condition II,

11 shows the switch-off safety relay circuit in a fault state III,

Fig. 12 is a schematic representation of

Monitoring circuits of the switch-on safety relay circuit in the idle state of

Load circuit,

13 shows the switch-on safety relay circuit in the active state of the load circuit,

Reference is made to FIGS. 1 to 5, which is a

Security circuit in different correct and faulty states show. The safety circuit comprises a load circuit LN between the terminals L and N, which can be switched on and off by a relay Kl, a display circuit AI, the

Switch position of the relay indicates, and a

Evaluation circuit, which shows the display state of

Display circuit AI logically linked with the command input to the relay Kl and from this the state of

Circuit arrangement as a whole rated as "error-free" or as "faulty". One can the display circuit together with the evaluation circuit as a

Designate monitoring circuit.

The relay Kl has as electromechanical relay a switch tongue kl, which switches between a closing point Sl and a Öffnerpunkt oil and is connected to a common point Gl. The display circuit AI comprises an auxiliary power source Hl and current detection means in the form of a light emitting diode LED1 and is connected to the switching points Gl and oil. Depending on the position of the switch kl, the light emitting diode LED1 is in operation or out of operation. The switched-on state of the light-emitting diode is indicated by arrows, while in the switched-off state the arrows are omitted.

The evaluation circuit comprises an integrated circuit IC1 which can make logic operations in such a way that two similar input signals give an output signal "error-free", which is represented here by a "0", and two dissimilar input signals to the

Output of an error signal leads, which is symbolized here by a "1." As input signal to the integrated circuit IC1 on the one hand the command input to the relay Kl and on the other hand the signal of an opto-coupler is used, the signal of the LED LED1 in a

corresponding input signal to the integrated circuit IC1 converts. The optocoupler consists of a circuit with switching transistor Ql, by the light of the

LED LED1 is switched on and otherwise switched off. In the circuit of the optocoupler is a resistor in series with the transistor Ql and a tap leads the signal of the optocoupler to the integrated circuit IC1 of the evaluation circuit.

Fig. 1 shows the error-free state of

Safety relay circuit in idle state. The relay Kl has switched off the load circuit LN and the

Display circuit AI turned on. The LED LED1 lights up and turns on the transistor Ql, so the opto-coupler outputs the signal "0", which corresponds to the command signal "0" to the relay K1. The

Integrated circuit ICl then outputs the error-free signal "0".

Fig. 2 shows the active state of

Safety relay circuit. With the signal "1" a switch-on command is given to the relay Kl, which the

Load circuit LN turns on and the display circuit AI turns off. The optocoupler receives no

Light signal more and gives the signal "1" to the

integrated circuit ICl on. Since both inputs of the integrated circuit ICl the evaluation circuit

are equivalent, the signal is "error-free", symbolized by "0" delivered.

Fig. 3 shows a fault condition I, which can be characterized by suspended or welded contacts. This fault condition I occurs when switching off the relay Kl and means that the relay is no longer safe. Because of the faulty position of the switching edge kl the diode LED1 does not light in the display circuit AI, so that the optocoupler outputs the signal "1" to the integrated circuit ICl, which detects the inconsistency between the command input to the relay Kl and the reaction of the display circuit AI and as error signal "1" outputs.

Fig. 4 shows a fault condition II, which may be referred to as "three-point contact bridging", because the

Switching points Sl, Gl and oil have contact with each other. In error state II, the diode LED lights up. When the relay Kl is switched on with the command signal "1", it should turn the display circuit AI open, but because of the

Three-point contact override not happening. This leads to a mismatch between the input signals of the integrated circuit IC1 and thus to a delivery of an error signal "1".

With Fig. 5, a fault condition III is outlined, which consists in a kind of two-point contact bridging. During operation, when the display circuit AI should be off, the LED LED1 receives an overcurrent, which by a (not shown)

Protective resistance is mitigated. The resulting light causes the optocoupler to emit the signal "0", which is detected by the integrated circuit IC 1. There is a discrepancy between the input signal "1" to the relay K1 and the signal "0" of the indication circuit AI, which leads to the error message As an error message, the change between short-time lighting of the LED and the extinction of the LED in the

Evaluation circuit be exploited, as with

Destruction of the LED would occur.

The circuit arrangement shown in Fig. 6 may be referred to as a safety relay with optical diagnosis. The circuit comprises two electromagnetic relays K1 and K2 of a simpler, conventional design, connected in parallel to a control source, not shown, so that the relay coils are energized or de-energized. It is also possible to control the relays K1 and K2 through separate control circuits. The relays K1 and K2 each have associated switches kl and k2, which have a

Rest position, as shown in Fig. 7, and a Working position (FIG. 8) as a function of

Excitation state of the relay coils can take. In their working position, the relay switches kl and k2 close a load circuit extending between the terminals L and N. Each relay switch kl, k2 is associated with a display circuit AI or A2, which the

Display position of the switch kl or k2 and each contain a light emitting diode LED1 or LED2 as a current detection means and in each case an auxiliary voltage source Hl, H2 for operating the respective associated light emitting diode. Of the

Relay switch kl in the illustrated rest position (Fig. 7) bridges the otherwise open display circuit AI to two (Gl, oil) of the three terminal contact points (Sl, Gl, oil) of the relay Kl and in the same way connects the switch k2 the corresponding terminal -Contact points (S2, G2, 02) of the relay K2 to close the second display circuit Ü2. When the relay switches kl and k2 are switched from their illustrated rest position (Fig. 7) to the operative position (Fig. 8), the display circuits AI and A2 are opened and the load circuit LN is closed.

As an auxiliary voltage source Hl, H2 can be any kind of

Power source can be used with the

Current detection means and especially light emitting diodes operate. In the case of the circuit of Fig. 6 is a

Transformer with a primary winding and two

Secondary windings as auxiliary voltage sources Hl, H2

used. The transformer forms a first transformer Tl as a first auxiliary voltage source Hl and a second transformer T2 as a second auxiliary voltage source H2. The

Primary winding is subjected to voltage pulses to the respective auxiliary voltage sources Hl, H2 intermittently to be effective and to query the respective state of the display circuits AI, A2.

Fig. 7 shows a schematic diagram of the switch-off safety relay circuit in the idle state. The

Auxiliary voltage sources Hl, H2 are simplified as

DC voltage sources shown. The

Connection contact points are indicated with Sl, Gl and oil resp. S2, G2 and 02. The first relay switch kl closes the first display circuit AI between the contact points G1 and oil and the second relay switch S2 closes the second display circuit A2 between the contact points G2 and 02. Arrows in the LEDs LED1 and LED2 indicate the light state of these diodes. If both diodes are fully lit, there is no fault condition in the currentless circuit of the load circuit, as has been explained with Fig. 1.

Fig. 8 shows the turn-off safety relay circuit in its active state in which the load circuit LN is turned on. The switch kl connects the

Contact points Sl with Gl and the switch k2 the

Contact points S2 with G2. The display circuits AI and A2 are open and the LEDs LED1 and LED2 are not lit. As explained with FIG. 2, the error-free active state is thus present.

An error state I ("hanging contacts") at the switch kl is explained with reference to Fig. 9. While the switch k2 has gone to rest when the load circuit is switched off, the switch kl is connected to the contact point S1

remained (eg because of welded contacts). Accordingly, the first display circuit AI is left open and the LED LED1 does not light up. This error state I can be detected, as explained in detail with FIG. 3. In addition, the discrepancy between the lighting states of LED1 and LED2 can be detected as an error. The renewed restart of the load circuit can be prevented.

Fig. 10 outlines another error condition II

("Three-point contact override") that can trip when the load circuit LN is energized The fault occurs due to a short circuit between the contact points Sl, Gl and oil, such as when a spring in the relay is broken How this error condition II can be detected

be exploited that the light emitting diode LED1 of

Display circuit AI in this fault is lit while LED2 of indicator circuit A2 goes out. When this error occurs, the load circuit should be de-energized immediately. immediate

Shutdown is possible via the relay K2.

Fig. 11 shows a fault state III ("two-point contact override") in which by breaking a

Metal part, the contact points Sl and oil get in touch with each other. This can be done before connecting the

Load circuit can be detected because in the idle state of the circuit (Fig. 7) both LEDs LED1 and LED2

should light up, but in fault state III LED1 goes out. Then the load circuit should not be turned on. When the fault condition III occurs during the running operation, this fault is determined according to the

Procedure according to FIG. 5 detected. The described circuit arrangement thus comprises a monitoring circuit having display circuits AI, A2 and evaluation circuits according to FIGS. 1 to 5. In this case, the evaluation circuits AI, A2 associated with integrated circuits can be combined with each other and additionally contain a further logic circuit integrated with the positions of the relay switch kl, k2 and the response states of the LEDs LED1, LED2

and evaluate them by logical linkage and, if necessary, safety interlocking measures

perform.

In order to realize the switch-on safety relay circuit, FIG. 6 is modified in such a way that the switches k1, k2 lie parallel to one another in the load circuit LN, as is also apparent from FIGS. 12 and 13. Therefore, if one of the switches kl or k2 should fail, the other switch can make sure that the

Load circuit is safely turned on or stays.

In contrast to the switch-off safety relay circuit according to FIGS. 7-11, the switch-on safety relay circuit shown in FIGS.

Safety relay circuit preferred, the relay Kl, K2 in the fallen state of the switch kl, k2 for the

Switching on the load circuit LN to operate. However, this is not mandatory and in Figs. 12, 13 are

Connection contact points provided with the same reference numerals, as they are based on the embodiment of FIGS. 6 to 11. Fig. 12 shows the sleep state of the turn-on safety relay circuit, and Fig. 13 shows the active state thereof. At rest, both LEDs light up LEDl and LED 2 of the two display circuits AI and A2, and in the active state of the switch-on

Safety relay circuit, the LEDs LEDl and LED2 are dark.

As in Fig. 3, the error state I at the relay Kl in snagging the switch kl at a contact point (here oil). This can be determined according to the monitoring method as described in FIG. Alternatively or additionally, the error state I ("Hanging

Contact ") when interrogating the display circuits AI and A2 are determined by the fact that the light states of the LEDs LED1 and LED2 do not match, while the on state of the load circuit LN is ensured by the switch S2.

In the fault state II ("three-point contact override"), all three terminal contact points Sl, Gl, oil of the relay K1 have electrical contact with each other, which can be detected as described in Fig. 4. In addition, the fault condition II can be detected when the relay K1 is energized , because the light states of the light-emitting diodes LED1 and LED2 differ, and in error state III ("two-point contact override") there is a bridging between the two

Connection contact points Sl and oil. The can be determined according to the method of FIG. 5. In addition, there is an error checking option based on

different luminous intensities of the diodes LEDl and LED2. As long as the switch k2 of the relay K2 closes the current path of the load circuit LN, the current has little Reason to flow over the fault location at the relay Kl. When the switch k2 is opened, however, the applied voltage could lead to an excessive current across the diode LED1, which is why the light-emitting diodes are expediently protected by a fuse ("polyfuse")

different light levels of the diodes LED1 and LED2, which detects that the relay Kl is no longer safe.

The two described methods of fault detection are suitably combined with each other in the monitoring circuit, the control positions of the relay switches kl and k2 and the response states of the diodes LED1 and LED2 are logically linked together to detect the fault conditions at the respective relay switches kl, k2. The used for this

Monitoring circuit, the two display circuits AI, A2 and associated evaluation circuits and

contain additional logic circuits to the

to perform the described logical operations.

Appropriately, the evaluation circuits and the additional logic circuits in a common

integrated circuit summarized.

Claims

claims

1. Circuit arrangement for switching a

Load circuit in safety technology, comprising:

- At least one electromagnetic relay (Kl) with a controlled switch (kl), in the active state of the

Relay assumes its closed working position while it is in the load circuit (LN), while in the idle state of the relay, the switch (kl) in terms of

Load circuit (LN) assumes an open rest position,

at least one monitoring circuit, comprising:

a switch position indication circuit (AI) which contains an auxiliary voltage source (HI) and current detection means and, in the quiescent state of the relay (K1), makes the current detection means responsive,

an evaluation circuit which determines the response of the

Current detection means with the command input "on" or "off" to the relay (Kl) compares and the comparison of the state of the circuit arrangement "error-free" or

Derives "incorrectly",

- In the error-free idle state, the relay (Kl) turns off the load circuit (LN) and turns on the indicator circuit (AI),

in the fault-free active state, the relay (Kl) switches the load circuit (LN) on and switches off the indicator circuit (AI),

- where a fault condition "hanging contacts" when

Switching off the load circuit (LN) by inconsistency of the command input to the relay with the response state of the current detection means is recognizable,

- Wherein a fault state "three-point contact override" when connecting the load circuit (LN) by Inconsistency of the command input to the relay with the partially persistent response of the

Strombestweismittel makes noticeable, and

- wherein a fault condition "two-point contact override" during operation by inconsistency of the command input to the relay with an incorrect response state of

Current detection means is recognizable.

2. Circuit arrangement according to claim 1,

where the switch-on command of the relay is a logical

Command signal "1" and the switch-off command a logical command signal "0" are delivered to the evaluation circuit,

wherein the positive response state of

Strombestweismittel a logic state signal "0" and the negative response state, a status signal "1" is generated, and

wherein the evaluation circuit in accordance with the

Indicates condition signal with the command signal error-free and indicates incongruity in case of mismatch.

3. Circuit arrangement according to claim 1 or 2,

wherein the power-down circuit of the load circuit (LN) is to be ensured, comprising:

a first electromagnetic relay (Kl) with a first switch (kl),

a second electromagnetic relay (K2) with a second switch (k2),

a first switch position indicating circuit (AI),

- A second switch position display circuit (A2), and - An evaluation circuit which the command inputs to the relay (Kl, K2) with the current states of

Display circuits (AI, A2) compares and derives therefrom the state of the circuit arrangement as "error-free" or as "faulty".

4. Circuit arrangement according to claim 3,

wherein the monitoring circuit integrated

Contains circuits which the respective

Evaluation circuits (AI, A2) are assigned, and

additionally contains other logic circuits to the

To evaluate the positions of the relay switches (kl, k2) among each other for agreement,

- In the error-free active state, the first and second switches (kl, k2) close the load circuit (LN) and the respective associated display circuit (AI, A2) open, which is characterized by non-response of the

Current detection means manifested,

- Wherein a state "hanging contacts" on one of the relays the associated display circuit (AI, A2) in its state before Stromlosschalten the load circuit (LN) remain, which is a fault condition of the

relevant relay is evaluable,

- Where a fault condition "three-point contact override" makes itself felt by partial response of the current detection means of the faulty relay when the load circuit (LN) is switched on and

- Where a fault condition "two-point contact override" at one of the relays the

Current detection means of the associated display circuit does not respond, or weakly, respond when the relay be switched on.

5. Circuit arrangement according to claim 1 or 2, wherein the switching on of the load circuit is to ensure, comprising:

a first electromagnetic relay (Kl) with a first switch (kl),

a second electromagnetic relay (K2) with a second switch (k2),

a first display circuit (AI),

a second display circuit (A2), and an evaluation circuit, which the

Command inputs to the relays (Kl, K2) with the

Current states of the display circuits (AI, A2) and compares the state of the circuit arrangement as

"Error-free" or as "incorrect" derived.

6. Circuit arrangement according to claim 5,

wherein the monitoring circuit integrated

Contains circuits which the respective

Evaluation circuits (AI, A2) are assigned, and

additionally contains other logic circuits to the

- In the error-free active state, both the first and the second switch (kl, k2) the

Close the load circuit (LN) and the respective

associated display circuit (AI, A2), which manifests itself by not responding the current detection means, - wherein a state "hanging contacts" on one of the relays the associated display circuit in its state before switching the load circuit (LN) remain leaves what can be evaluated as a fault condition of the relevant relay,

wherein a fault condition "three-point contact override" is manifested by partially responding the current detection means of the faulty relay when the load circuit (LN) is turned on, and wherein a fault condition "two-point contact override" in one of the relays

Make current detection means of the associated display circuit violently respond when the other relay is switched to the idle state.

7. Circuit arrangement according to one of claims 1 to 6, wherein the current detection means as light emitting diodes (LED1, LED2) are formed, which in series with a respective auxiliary voltage source (Hl, H2) and with two (Gl, oil; G2, 02) of the three contact points (Sl, Gl, Oil, S2, G2, 02) of a

respective relays (Kl, K2) are located.

8. Circuit arrangement according to one of claims 3 to 7, wherein a first auxiliary voltage source (Hl) of the first

Display circuit (AI) includes a first transformer (Tl), which is acted upon by a clock pulse with a current-voltage pulse, and

wherein a second auxiliary voltage source (H2) of the second display circuit (A2) includes a second transformer (T2), which is cyclically acted upon by a current-voltage pulse.

9. Circuit arrangement according to claim 8,

wherein the first and the second transformer (Tl, T2) are structurally combined and a transformer with a common Form primary winding and with two secondary windings.

10. Circuit arrangement according to one of claims 3 to 9, wherein the first and the second electromechanical relay (Kl, K2) are connected to a control circuit.

11. Circuit arrangement according to one of claims 1 to 10, wherein an optocoupler circuit the respective

Display circuit (AI) connects to the respective evaluation circuit.