JPS61160101A - Triple sequence circuit - Google Patents

Abstract

PURPOSE:To avoid the influence of a single failure generated in any one sequence of a triple self-holding circuit by constituting the self-holding signal of each self-holding circuit of a 2/3 logical signal between the output signals of corresponding other two self-holding circuits and the output signal of the self-holding circuit concerned. CONSTITUTION:When it is supposed that an optional one power source, e.g. 11a, out of power sources 11a-11c is braked during the excitement of all relays 11a-11c, relays 14a, 15a are unexcited, but the states of other relays and an output signal to a controlled system 30 are not changed. When the power source 11a is restored, relay contacts 14b, 14c are continuously closed, so that the relay 15a is excited and a sequence circuit 10a is restored to the original state simultaneously with the restoration of the power source 11a without the execution of any operation. When the power source 11b or 11c is braked, the same rule is applied.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention triplexes sequence circuits, and adopts majority logic of the output signal of each sequence circuit, that is, 2 out, of 3 logic (hereinafter referred to as 2/3 logic). The present invention relates to an improvement of a triplex sequence circuit configured to output to a controlled object.

[Technical background of the invention and its problems] In sequence control systems that require high reliability and high availability, the sequence circuits are often triplexed.
We are trying to meet that demand.

In this case, it is common to take the logic of 2/3 of the output signal of each sequence circuit and use it as the final output signal to the controlled object. Since the 2/3 logic determines the output signal by a majority vote of three logic inputs, even if any one series of sequence circuits fails, the output signal to the controlled object will not be affected.

By the way, a self-holding circuit is often used in such a sequence circuit. If the power to one of the I series is turned off while the self-holding circuit is operating, all the relays in that series become de-energized, the self-holding of that series is released, and even after the power is turned on again, the original excitation remains. The self-holding circuit does not return to the state, i.e. once the self-holding circuit is reset,
In order to get it to stay reset and work again.

An operation is required for this purpose.

Therefore, in a triplex sequence circuit, when the self-holding circuit of any one series is in a non-excited state even after the power is restored for this reason, if the power of any other series is cut off in the same way, The output of the corresponding 2/3 logic circuit changes under the influence, giving an erroneous signal to the controlled object. This contradicts the purpose of the triplex sequence circuit, which aims to withstand a single failure.

This will now be explained using a simple example shown in FIG. Third
In the figure, sequence circuits 10a, 10b, 10c constitute the simplest self-holding circuit, and power supplies 11a, llb.

11c and is triplexed. Contact points 12a, 12b
, 12c are three interlocking momentary contacts of the push button switch 12 (not shown), and relays 14a, 14b,
14c, respectively. Further, contacts f3a, 13b, and 13c are three interlocking momentary contacts of a push button switch 13 (not shown), and a relay 14a.

This is for making each of 14b and 14c non-excited.

If, for example, the power supply 11a is temporarily cut off while the relays 14a, 14b, and 14c are being energized and then restored, the relay 14a will be in a non-excited state, but the logic output of the 2/3 logic circuit 40, that is, the control target The control signal applied to 30 does not change. However, if either the power supply 11b or llc is cut off in this state, the logic output of the 2/3 logic circuit 40 changes from on to off. In other words, the sequence circuit is
Although the power source 11b or llc
A single failure will cause an erroneous control signal to be sent to the controlled object 30.

To prevent such a situation, it is necessary to press the push button switch 12 and re-energize the relay 14a when the power supply 11a is restored. However, relying on a human system for this operation poses a problem in terms of reliability, and is not suitable for systems that require high reliability. Sequence circuits applied to actual systems are more complex and have a variety of possible failure modes, so they must be monitored by one person.

There is a need for a triplex sequence circuit that does not require intervention and has the ability to automatically avoid or recover from events caused by failures.

[Object of the Invention] An object of the present invention is to provide a triplex sequence circuit that can avoid the influence of a single failure occurring in one series of triplex self-holding circuits.

[Summary of the Invention] In order to achieve the above object, the present invention divides the self-holding signal of each self-holding circuit into the output signal of the corresponding two series of self-holding circuits and the own output signal. It is characterized by being composed of three logic signals. That is, the self-holding signal is given not only as its own logic output, but also as a ⅔ logic signal of the corresponding three series of logic outputs including itself. As a result, even if a failure occurs in any one series, as long as the other two series are normal, the self-holding signals of each series can remain in a normal state, so the self-holding circuit is not affected by the failure.

If the failure is recovered, automatic return to the original state becomes possible.

[Embodiment of the Invention] FIG. 1 shows a configuration diagram of a triplex sequence circuit according to an embodiment of the present invention.
This is because relays 15a, 15b, and 15c are provided that operate with 2/3 logic of the contacts of relays 14a, 14b, and 14c.

Furthermore, the contacts are used as self-holding contacts in the circuits of relays 14a, 14b, and 14c, respectively.

In addition, relays 15 a + 15 b r 15 c are power supplies 11 a and llb, respectively.

ie is used as an excitation power source.

Assume that in the above configuration, one arbitrary series of power supplies 11a, llb, and llc is disconnected while relays 11a, llb, and lie are all energized. For example, if this is the power source 11a, the relays 14a and 15a will be de-energized, but the states of the other relays and the output signals to the controlled object 30 will not change.

After that, when the power supply 11a is restored, the relay contact 14b is activated.

Since relay 14c remains closed, relay 15a is energized. As a result, the relay 14a is also energized again, and the sequence circuit 10a does not require any external operation when the power supply 11a returns.

Return to original state. The same applies when the power supply 11b or llc is cut off.

As mentioned above, with the triplex sequence circuit, any one sequence of ft! Even if the power is cut off, the self-holding circuit has the ability to automatically recover to the state immediately before the power was cut off when the power is restored, so even if a similar failure occurs thereafter, it will not be affected. .

By the way, power outages are only caused by accidents that occur in corners.

It's not something that comes. In such a control device, it is possible to maintain one series online, so it is possible that the power of that series may be intentionally turned off. Even in this case, the same effect can be obtained by turning the power back on after maintenance is completed.

Furthermore, although the explanation up to now has focused on problems with the power supply, the present embodiment is effective even when a problem occurs in the components of the self-holding circuit.

For example, by pressing the switch 12, the relays 14a, 14b,
If one of the contacts 12a has a contact failure when attempting to energize relay 14c, relay 14a will not be energized in the conventional configuration shown in FIG.
Since relay 5a is excited, relay 14a also
It is excited in the same way as b and 14c, and is not affected by the switch contact 12a. Conversely, when the switch 13 is pressed to de-energize the relays 14a, 14b, and 14c.

If the switch contact 13a does not operate, the relay 14a remains energized in FIG. 3, but is de-energized in this embodiment. Switch contacts 12b, 12c.

The same applies to 13b and 13c.

FIG. 2 shows another embodiment of the invention.

This is an example where the control system has another power source 41. The power source 41 is an excitation power source for the 273 logic circuit 40, and the contacts of the relay 42 are commonly used as an output to the controlled object 30 and as a self-holding signal for the sequence circuits 10a, 10b, and 10c. Even when the triplex sequence circuit is configured in this way, the same effects as those of the above-mentioned embodiments can be obtained.6Furthermore, in the case of this embodiment, by having the power supply 41, compared to the embodiment of FIG. , the circuit configuration becomes simple, but in this case, failure of the power supply 41 must not be considered.

It should be noted that the present invention is limited only by the scope of the claims, and is of course not limited to the logic circuits shown in the embodiments. In addition, in the above embodiment, a logic circuit using a relay was described for ease of explanation, but it may also be applied to a static similar device using a digital IC, or a computer or sequence controller that executes logic operations using software. It is clear that it can be easily applied.

[Effects of the Invention] As described above, the present invention provides a highly reliable triplex sequence circuit that can avoid the influence of a single failure on various failure modes of a triplex self-holding circuit. is obtained.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a triplex sequence circuit showing one embodiment of the present invention, Fig. 2 is a block diagram of a triplex sequence circuit showing another applied example of the present invention, and Fig. 3 is a block diagram of a conventional triplex sequence circuit. FIG. 2 is a configuration diagram showing an example of a triplex sequence circuit. 15a, 15b, 15c, 42- relay, 40-2
/3 logic circuit. (7317) Agent: Patent Attorney Noriyuki Chika (
Figure 1 Figure 2 Figure 1 ==----J Figure 3

Claims (1)

[Claims] Triple the same sequence circuit including self-holding circuit,
In a triplex sequence circuit that takes the majority logic of each output signal and outputs it as an output signal to the controlled object, each of the three corresponding self-holding circuits has its own output signal and the corresponding output signal of the other two systems. A triplex sequence circuit characterized in that it performs majority logic with an output signal and further uses this majority logic signal as a self-holding signal for its own self-holding circuit.