JP2864942B2 - Method for detecting conduction failure of parallel contacts - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting conduction failure of contacts provided in parallel.

[0002]

2. Description of the Related Art Conventionally, a technique of connecting contacts in parallel has been used for the purpose of improving the reliability of contact opening / closing or reducing the current capacity per contact. Thereby, even if a contact other than at least one of these contacts causes a conduction failure due to destruction or an increase in contact resistance, current flows through the remaining healthy contacts,
External effects are unlikely to appear. However, in this case,
The current that has flowed from the contact that has failed to conduct until now flows to the remaining healthy contact, which increases the load on the healthy contact in terms of current capacity. As a result, the life of the healthy contact may be shortened, or in the worst case, the contact may be broken, and power may not be supplied to the load. In addition, even when only healthy contacts are sufficient in terms of current capacity, the operation is performed in a state where reliability is reduced because the number of parallel contacts is reduced, which is inconvenient. To avoid these problems, there is a method of treating auxiliary contacts that operate simultaneously with the main contacts for supplying power to the load as pseudo main contact information, and using this information to detect abnormalities early. However, since the main contact and the auxiliary contact are separate contacts, there is a drawback that the contact states of both do not always match.

[0003]

SUMMARY OF THE INVENTION In the prior art,
A contact having no conduction failure cannot be manufactured, and there is always a risk that the problems as described in the above-mentioned prior art may occur. Accordingly, an object of the present invention is to provide a method for detecting conduction failure of parallel contacts in order to prevent the development of a serious failure due to the above-mentioned problem.

[0004]

According to the present invention, in a circuit in which a plurality of contacts are arranged in parallel and a current flows through these contacts simultaneously, a current sensor for detecting a current flowing through each contact, Means for comparing the detected values and means for issuing an alarm output in accordance with the result of the comparison are used.

[0005]

According to the present invention having the above-described structure, when even one of the parallel contacts has a conduction failure, it can be detected.

[0006]

FIG. 1 is a diagram showing an example of a method for detecting conduction failure of parallel contacts according to the present invention. It is assumed that the number of parallel contacts in FIG. 1 is two for simplification of the description. In FIG. 1, the power supply unit 1
Two contacts 3 operating simultaneously in the path from
The power supply to the load 2 is controlled by opening and closing these components a and 3b in parallel. Also, the contacts 3a,
In the parallel circuit part with 3b, current sensors 4a, 4b
And detects the current flowing through the contacts 3a and 3b. All the detected values proportional to the current are collected by the comparison judging unit 5, and the values are compared between each other. Now, the contacts 3a, 3
b is sound and in the ON state, the contact resistances of the two are almost equal, and the resistivity of the circuit is uniform. Since the current flowing from the power supply unit 1 to the load 2 is almost equally divided, the current sensors 4a, The values detected in 4b are also equal, and the comparison determination unit 5 determines that the value is normal as a result of the comparison. However, for example, if a conduction failure occurs at the contact 3a, the current flowing to the contact 3a decreases and the current flowing to the contact 3b increases, so that the values detected by the current sensors 4a and 4b differ. . As a result of the comparison, the comparing and judging unit 5 which receives these values judges that the conduction failure of the contact has occurred and activates the alarm output unit 6. The activated alarm output unit 6 outputs a signal indicating that the contact is defective in a required output form. As described above, when the current values flowing through the respective contacts are compared with each other, the present invention can be applied not only to the two parallel contacts as shown in FIG. 1 but also to the detection of conduction failure of three or more parallel contacts. It is. FIG. 2 is a diagram showing an example in which the method for detecting conduction failure of parallel contacts according to the present invention is used. The path from the power supply unit 1 to the load 2 is opened and closed by the contacts 3a and 3b of the relay 3 controlled by the control circuit 3c.
Is controlled. Contact 3
The currents a and 3b are arranged in parallel, and the current flowing through each contact is input to the A / D conversion circuit 5a by the current sensors 4a and 4b as a detection value proportional to the current. Each of the detected values is converted from an analog amount to a digital amount by an A / D conversion circuit 5a, and then passed to a CPU circuit 5b for comparison.
Will be judged. As mentioned in the previous section,
If both the contacts 3a and 3b are in a healthy state, the current sensor 4a,
The detection values of 4b are almost equal, and the CPU circuit 5b does not output to the drive circuit 6a because the result of the comparison determines that it is normal. However, if any one of the contacts 3a, 3b has a conduction failure, the detection values of the current sensors 4a, 4b are different, and the CPU circuit 5b determines from the comparison result that the conduction of the contact is defective. At this time, the CPU circuit 5b is driven by the drive circuit 6a.
Is activated, and the indicator lamp 6b is turned on. According to the above-described embodiment, it is possible to detect the conduction failure of the parallelized contacts and report the fact to the outside. FIG. 3 is a diagram showing another example using the present invention. The output of the CPU circuit 5b in FIG.
The power supply output stop circuit 1a is operated and the power supply from the power supply unit 1 is stopped in the event of a contact failure such as the example shown in FIG. is there. The example shown in FIG. 3 is particularly effective when a larger load current is controlled by using contacts having a small current capacity in parallel. This can be avoided by stopping, and thus, heating, burning and the like due to overcurrent can be prevented beforehand.
In these implementations, it is easier to use the comparison and determination unit by allowing the circuit resistance, the operating time error, the current sensor error, and the like between the contacts.

[0007]

According to the present invention, as described above, there is an effect that it is possible to prevent a decrease in device reliability or a serious problem due to the conduction failure of the contacts. In addition, since it is easy to take preventive measures from early detection of an abnormality according to the present invention beforehand, heating caused by poor contact, and those having a large current capacity contact in parallel with concern for a burnout accident,
It is possible to replace the contact with a smaller current capacity,
It can contribute to downsizing and cost reduction.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a method for detecting conduction failure of parallelized contacts according to the present invention.

FIG. 2 is a diagram showing an example using the detection method of the present invention.

FIG. 3 is a diagram showing another example using the detection method of the present invention.

[Explanation of symbols]

 Reference Signs List 1 power supply section 1a power supply output stop circuit 2 load 3 relay 3a, 3b contact 3c control circuit 4a, 4b current sensor 5 comparison / determination section 5a A / D conversion circuit 5b CPU circuit 6 alarm output section 6a drive circuit 6b indicator light

Claims (1)

(57) [Claims] In a circuit in which a plurality of contacts are arranged in parallel and a current flows through these contacts at the same time, a current flowing through each contact is detected by a current sensor, and each detected value is compared. As a result, when at least one of the detected values is significantly different from the others, an alarm output is issued, thereby detecting a conduction failure of the parallelized contacts.