JPH0387672A - Diagnostic device for contact - Google Patents

Abstract

PURPOSE:To exactly diagnose the contact state of a contact by measuring a voltage drop caused by a current flowing between the contacts and comparing a contact resistance derived from this voltage and a current which always flows with a contact resistance measured in the beginning. CONSTITUTION:Between both ends of a contact A, a lead wire 1 for measuring a voltage of the contact is connected, and led to a scanner 2. In this state, by a command from a computer 4, the scanner 2 is operated, and a terminal voltage of the contact A is measured. When the contact A is in a short circuit state, as for a flowing current, a current determined by a load flows, therefore, a contact resistance is derived from the terminal voltage, and also, since the load is constant, a variation of the contact resistance can be perceived from a variation of the terminal voltage. Subsequently, it is compared with a contact resistance in the beginning stored in a memory of a CPU, and a contact state of the contact can be diagnosed exactly from a variation of the contact resistance. Also, with regard to contacts B - G, as well, by connecting them to the scanner 2 by a lead wire and executing the scanning by a command of the computer 4 in the same way as the contact A, all the contacts or a specific contact only can be diagnosed.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention is directed to wA electrical appliances, contactors, etc. used in control panels used for controlling electrical equipment, etc. This invention relates to a diagnostic device for contacts that turn electricity on and off.

(Prior Art) Devices having contacts such as relays and contactors are indispensable for controlling electrical devices. For example, it is not uncommon for relays used in steel, 11 paper, power plants, substations, etc. to have as many as 10,000 relays, even in places where there are only a few relays, and where there are many relays on the slave side or above. The reliability of the contacts of these devices has been thoroughly evaluated since they can cause major problems to the plant. but.

Even with this, it is still difficult to completely prevent contact failures, so consideration has been given to the combined use of multiple circuits and redundant circuits to prevent such accidents.

(Problem to be Solved by the Invention) The contact resistance of a contact changes depending on the contact position of the contact, and therefore, the contact resistance also changes depending on the voltage applied to the contact and the current flowing. Generally, it is estimated that each contact resistance is normally distributed when ON and 0FFL are repeated, so failures are estimated from statistical probabilities, and multiple lq paths or redundant circuits are used in combination.

However, when combined with multiple circuits or redundancy, all equipment connected to this, including relays.

Also, multiple units of equipment are required. Therefore, the space and equipment costs will be enormous in proportion to this 7.Moreover!
Even if it is a redundant circuit that makes the rjl path, this only works in 1
This only occurs when the contacts of a relay used in a circuit malfunction, and although countermeasures can be taken immediately after a malfunction occurs, no countermeasures have been taken to prevent the malfunction from occurring.

Therefore, the present invention has been made in view of the above circumstances, and
Accidents can be prevented by constantly or periodically measuring the contact resistance of the contacts2, detecting malfunctions in advance, generating a signal that could lead to an accident, and recommending replacement2. . Moreover, it eliminates the need for multiple circuits and redundant circuits.

[Inventive configuration] (Tanu's means of solving the problem) The present invention measures the voltage drop due to the current flowing between the contacts,
Calculate the contact resistance from this voltage and the current that flows normally. 1. Then, compare this contact resistance with the initially measured contact resistance. Based on b and y-, check whether there is a change in contact resistance σ).
There is something to investigate.

It is generally known that the contact resistance of new contacts follows a normal distribution. Therefore, the contact resistance of a new contact can be adequately controlled by ordinary statistical processing, that is, standard NF average and standard side difference. Therefore, a reliable contact can be made by pressing the standard side difference sufficiently small. However, according to my experience, the contact resistance of contacts changes over time regardless of the presence or absence of a load.The degree of change in points 1 and 2 is normal distribution for new products, but some The only thing that increases is the contact resistance. In other words, the population of contact resistance of each new contact may be thought to be one, but as time passes, the population may be divided into at least two, or even more.

In other words, as with a new product, normal statistical processing is insufficient and processing using extreme value distribution is required. In addition, since contact resistance changes depending on the voltage applied to the contact and the current flowing, it was found that it is impossible to know in advance if there is a problem with the contact by simply measuring the contact resistance with an ohmmeter, etc. .

Therefore, in the present invention, contact failures are monitored by constantly measuring the contact resistance of each contact point.In other words, in the present invention, a lead for electric HE measurement is used to measure the voltage between each contact point and the contact point. Pull the wire 1.'' and connect it to a scanner so that multiple voltages, or contact resistances, can be measured sequentially.

The contact resistance value measured here is sent to the computer via the ink face so that it can be compared with the initial contact resistance. Note that since contact resistance also depends on temperature, accuracy is ensured by multiplying it by a 1,000-degree temperature correction coefficient. In addition, for contacts through which alternating current flows, measure the alternating voltage and compare the impedance.

C) Since the structure is as described above, the contact resistance between the contacts can be constantly or periodically monitored. By constantly or periodically monitoring contact resistance, it is possible to know in advance of changes and abnormalities in contact resistance, and it is possible to prevent accidents due to contact failure7. Since resistance is the contact resistance due to the voltage applied to the load and the current flowing through the contacts, the truly necessary value of contact resistance can be found.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

The first diagram is a configuration diagram in which the contact diagnosis device of the present invention is applied to a generator 0 control circuit. Here, it is assumed that contact A is operated by an auxiliary relay RYb, and a wire Iti%1 for measuring the voltage of the contact is connected between both terminals of contact A, and is guided to scanner 2. Contacts 8 to G are connected in the same way. Here, the scanner 2 is connected to a computer 4 via an interface 3, and can perform scanning under the command of the computer.

In the sequence of operations, the computer 4 first sends a command to the scanner 2 to measure, for example, the terminal voltage of contact A. A voltage signal is received via the interface 3, and the initially measured voltage signal is received from the CPU and compared. If the voltage differs, an alarm signal is immediately issued to prompt the replacement of the auxiliary relay (7) having this contact at an early stage. if,
If the abnormality is 4, it will be a long time to go to black 13 and the same at Tsuji.
73 Measure the temperature with a thermocouple placed near the contact (omitted in this figure) for the comparative signal called from CP l:, J, and add the temperature coefficient to ensure accuracy. The period L f'L , and the flowing current is ℃ depending on the terminal r and voltage.
Changes in the measured voltage were calculated by taking into account fluctuations in the main voltage of the control circuit. The fluctuation of main type C: can be easily obtained by measuring the voltage of an open circuit, for example, the voltage of contact B to be scanned next.

Next, the operation of the present invention will be described in section X).

The scanner is operated by the computer controller and measures the terminal voltage between the contacts. If the contacts are short-circuited, the current flowing is determined by the load, and the contact resistance can be determined by measuring the terminal voltage. Since the voltage is constant, it can be seen that the contact resistance changes with changes in f and voltage. By comparing the contact resistance with the initial contact resistance stored in the CPU's memory, changes in the contact resistance can be detected. Incidentally, since the scanning is carried out at the 11th table in the convenience store, it is possible to change the situation as desired, and it is also possible to measure only a specific contact point.

An example of the contact resistance measured by carrying out the present invention is also shown in the normal probability graph in Fig. S2. The contact resistance of 111 is on the normal probability graph, and it is a straight line with S,
It definitely follows a normal distribution. Only Schiff.

Due to changes over time, the straight line becomes 7 less and ε is divided into 2 or more 3t, that is, the contact resistance population is divided into low and high contact resistance populations. By employing the present invention, such abnormalities in contact resistance can be detected in advance, and accidents caused by malfunctioning contacts can be completely eliminated. Furthermore, it is no longer necessary to operate multiple circuits, redundant circuits, etc., which have been used in the past. In addition, @2
In the figure, it shows that it has been used up to 10 times the original Q, but in reality, it was replaced with a new one with a value of more than 5 times.In Figure 7, I reconnected it to another auxiliary circuit and tracked the progress with the l-value. be.

In the above explanation, the control circuit of electrical equipment) 1. Examples of the contacts of the auxiliary relay that are used have been described, but the invention is not limited to these, and it goes without saying that it can be used for any contact that can turn the electric circuit ON or 0FFi. [Effects of the Invention] Since the present invention compares the voltage information of the contact with the initial information and makes an accurate diagnosis, multiple circuits and redundant 10" circuits are not required, and the IJ resistance of the contact is improved. ”, a diagnostic device can be obtained.

[Brief explanation of drawings]

Fig. i is a configuration diagram showing the contact diagnosis device of the present invention, and Fig. 2 is a graph of 1'11 contact resistance peak and characteristic change peak measured in an embodiment of the present invention. 1... Connection lead wire 2... Scanner 3 - Interface 4... Combi coater A-G - Contacts 1'tYa, RYb... Auxiliary relay RYE, RY2... Magnetic contactor PL-R. PL-G-=pilot lamp

Claims (2)

[Claims] (1) Compare the contact resistance calculated from the measured value of the voltage drop between the contacts with the current flowing between the contacts and the current flowing during the steady state with the stored contact resistance at the initial stage, and determine if the contact is abnormal. A contact diagnostic device characterized by determining the presence or absence of. (2) The contact diagnostic device according to claim 1, characterized in that it determines the presence or absence of an abnormality and outputs an alarm when an abnormality occurs.