JPH01292267A - Apparatus for detecting life of contact - Google Patents

Abstract

PURPOSE:To detect the life of a contact, by mounting a contact-bonded terminal having a temp. sensor embedded therein to the terminal plate bonded to a contact stand having the contact mounted thereto in a freely detachable manner and performing alarming/display in accordance with the output of the temp. sensor. CONSTITUTION:In an electromagnetic contact device, the temp. sensor 14 of a contact life detector is constituted, for example, by embedding a PTC thermistor in the cylindrical part 22a of a contact-bonded terminal 22 by an insulating substance 22b such as an epoxy resin and a lead wire 15 is led out from the thermistor to the outside. This temp. sensor 14 is tightened to a terminal plate 3 in a freely detachable manner by a terminal screw 3a and connected to the relay unit 16 mounted to the lower part of the electromagnetic contact device by the lead wire 15. When a fixed contact 1 and a movable contact are consumed and the temps. of both contacts rises during the supply of a current to load, the resistance of the thermistor 14a increases and a current is decreased and, therefore, the relay unit 16 is operated to cut off the current of an electromagnetic coil 10 and an alarm/display apparatus is actuated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a contact life detection device for detecting the life of a contact in an electromagnetic contactor or the like while the contact is energized.

Mechanical contacts, such as electromagnetic contactors, that switch on and off the load current wear out as they are used due to arcs that occur between the contacts, and eventually become unusable, so we can detect this and prevent accidents before they occur. Needs to be replaced.

[Conventional technology]

An example of an electromagnetic contactor is shown in FIG. Here, the fixed contact l is attached to one end of the fixed contact block 2, and the other end is attached to the terminal screw 3.
A is attached. There is also a device in which a terminal plate is coupled to the fixed contact block 2 and a terminal screw 3a is attached to this terminal plate. The movable contact 4 facing the fixed contact 1 is a movable contact 5
This movable contact 5 is attached to a movable contact support 6, and this movable contact support 6 is attached to a movable iron core 7.
is attached to. The movable core 7 is attracted by an electromagnet formed by a fixed core 9 and an electromagnetic coil 10 installed at the bottom of a case 8 housing the electromagnetic contactor, and is released by a return spring 11. 12 is a contact spring, and 13 is an indicator rod provided on the upper part of the movable contact support 6 and protruding from the upper part of the case 8 for detecting the life of the contact.

To open and close this electromagnetic contactor, an electromagnetic coil 10 is connected in series with a power source. When the push button switch is closed and the electromagnetic coil 10 is energized, the fixed iron core 9 is magnetized and attracts the movable iron core 7. Therefore, the movable contact support 6 is lowered, the movable contact 4 comes into contact with the fixed contact 1, and this electromagnetic contactor is closed. At this time, the contact spring 12 is pressed by the movable contact support 6 to press the movable contact 5 and press the movable contact 4 to the fixed contact 1. When the electromagnetic coil 10 is de-energized, the movable core 7 is pushed up by the repulsive force of the return spring 11, so that the fixed contact 1 and the movable contact 4 are separated. Here, even if both contacts 1.4 are in contact when both contacts 1.4 are not worn out, the display bar 13 protrudes outward from the hole in the case 8 as shown in FIG. However, when both contacts 1 and 4 are worn out, the display bar 1
The protrusion of contact 1.3 gradually decreases until it no longer protrudes from the hole of case 8 as shown in FIG. can.

The amount of consumption is mechanically displayed. Therefore, there is a problem of poor accuracy since most of the work is done visually, and there is also the problem that when installing an electromagnetic contactor, it cannot be confirmed unless the position is approached.

SUMMARY OF THE INVENTION An object of the present invention is to provide a contact life detection device that can easily monitor the life of a contact from a distance without relying on human judgment while the contact is energized.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention combines a fixed contact block to which a fixed contact is attached and a terminal board to which a terminal screw is screwed, and conducts electricity between the fixed contact and a movable contact facing the fixed contact. A contact life detection device that detects the life of both middle contacts includes a temperature sensor that is embedded with an insulator in the cylindrical part of the crimp terminal and removably attached to the terminal board with a terminal screw, and the output of this temperature sensor is used to open and close the terminal. and an alarm/display device connected to the output end of this output circuit, and in the case where the movable contact is driven by an electromagnetic coil, the normally closed contact of the output circuit is connected to the electromagnetic coil. may be connected in series.

[Effect]

As the contacts wear out, the contact resistance between the fixed contacts and the movable contacts increases. When the contact resistance between the two contacts increases in this way, the temperature of the contact increases when current is applied between the two contacts, and the temperature of the contact base and the terminal board coupled to the contact base also increases. Figure 7 shows the relationship between the operating time t and the temperature T of the contact. The time t on the horizontal axis is approximately 1 hour per 2 scales, and approximately 1200 openings and closings were performed in 1 hour (as shown in the figure). The number of RBIs is less than this). t,, j2+ t3 is the time during which the current supply is stopped, Co is the ambient temperature, C1 is the temperature of the contact that is relatively worn out, and C2 is the temperature of the contact that is less worn out. According to the figure, the temperature rise of contacts with little wear is relatively low and stable, but the temperature rise of contacts with advanced wear is very high and unstable. The present invention focuses on the rise in temperature of such contacts and conductors near the contacts, and uses crimp terminals with temperature sensors embedded in them to be detachably attached using terminal screws on the terminal board connected to the contact block to which the contacts are attached. The output of this temperature sensor is used to issue an alarm/display via an output circuit using an alarm/display device. In addition, in devices such as electromagnetic contactors that use an electromagnetic coil to drive a movable contact, the contact of this output circuit interrupts the energization of the electromagnetic coil.
The idea is to free up electromagnetic contactors. Note that the crimp terminal with the temperature sensor embedded in it is tightened with a terminal screw together with the crimp terminal attached to the end of the electric wire drawn in from the outside, so if this tightening is loose and the contact resistance is high, the temperature sensor will detect the temperature rise in this part. It is also possible to operate the output circuit by

〔Example〕

1 to 6 show embodiments of the present invention, and FIGS. 8 to 6 show embodiments of the present invention.
Components that are the same as in FIG. 10 are given the same reference numerals as in FIGS. 8 to 1O. FIG. 1 shows an embodiment in which a contact life detection device according to the present invention is provided in an electromagnetic contactor, and since the electromagnetic contactor itself is completely the same as a conventional one, a description thereof will be omitted. In the temperature sensor 14 of the contact life detection device according to the present invention, as shown in FIGS. 2 to 4, for example, a PTC thermistor 14a is embedded in a cylindrical portion 22a of a crimp terminal 22 with an insulator 22b such as epoxy resin, and a lead wire 15 is led out. This temperature sensor 14 is detachably fastened to the terminal plate 3 with a terminal screw 3a. Of course, a thermocouple may be used instead of the thermistor 14a. The temperature sensor 14 embedded in the cylindrical portion of the crimp terminal 22 is attached to the lower part of the electromagnetic contactor or connected to the relay unit [6] by a lead wire 15.

The electromagnetic contactor equipped with such a temperature sensor 14 and relay unit 16 is connected to the three-phase power supply R3T and the load 17 is connected to the three-phase power supply R3T.
Connection diagrams for controlling opening and closing are shown in FIGS. 5 and 6.

First, the wiring of the main electric circuit is shown in Figure 5.

In both Figure 6, the load 17 is the thermal relay 18, the main contact (
The fixed contact 1 and movable contact 4) 1, 4, fuse or breaker pot, and disconnector 21 are connected in series to create a power supply R3T.
It is connected to the. The thermal relay 18 includes a thermal element 18a and a thermal contact 18b that operates when the element 18a overheats. Further, the movable contact 4 operates together with an auxiliary contact 19a driven by the electromagnetic coil 10 and attached to the movable contact support 6.

The operation circuit of this electromagnetic contactor uses a push button switch 20, and the switching contact 16a of the relay unit 16, which is connected to the power source R3 and driven, is always closed to the switched contact 16b side, and this switched contact 16b is pressed. The normally closed contact 20a1 of the button switch 20, the normally open contact 20b, the electromagnetic coil 10, and the thermal contact 18b are connected in series, and the auxiliary normally closed contact 19a of the magnetic contactor is connected in parallel with the normally closed contact 20b, and the power supply R3 is connected. It is connected.

In FIG. 5, as shown in FIG. 1, the temperature sensor 14 composed of each thermistor 14a attached to the terminal board 3 is connected in series and connected to the input end of the relay unit 16 by a lead wire 15, and is energized. ing.

When the contact 20b of the pushbutton switch 20 is closed, a current flows through the electromagnetic coil 10, and the main contact 1.4 as well as the auxiliary contact 1.
Since contact 9a is closed, main contacts 1 and 4 are closed even if contact 20b is opened.
is retained. When the contact 20a is opened, the current to the electromagnetic coil 10 is cut off, and the electromagnetic contactor is released.

The main contacts 1 and 4 are worn out and the load 17 is energized.
．． When the temperature of 4 increases, the resistance of the thermistor 14a increases and the current decreases, so the relay unit 6 operates,
The switching contact 16a is switched to the switched contact 16C side. Therefore, the current in the electromagnetic coil 10 causes the buzzer to sound.

FIG. 6 shows a case where the temperature sensor 14 is a thermocouple 14b, although a description thereof will be omitted since the wiring is almost the same as that in FIG. 5. In other words, one ends of two different metals are connected, this connection point is attached to the vicinity of each fixed contact l or to the terminal board, and the metal wire forming the thermocouple 14b is directly connected to the input end of the relay unit 16. The thermocouples 14b are connected in parallel. When the main contacts 1 and 4 are worn out and the temperature of the main contacts 1 and 4 rises due to energization, due to the temperature difference with the relay unit 16 side,
The relay unit 16 operates, and the switching contact 16a is switched to the switched contact 16C. The main contact 1.4 opens and the alarm/display device 22 operates in the same manner as described in connection with FIG. 5 below. Note that only one of the switches shown in FIGS. 5 and 6 may be operated, and instead of the relay unit 16, a non-contact switch that is opened and closed by an electronic circuit may be used. When the contact block 2 and the terminal board 3 are connected, both the contact block 2 and the terminal board 3 have good heat conduction, so the temperature rise of the main contact 1.4 is immediately transmitted to the terminal board 3. The terminal screw 3 contacts 1.4 can be opened to connect the external power supply. Furthermore, it can also be applied to switches other than electromagnetic contactors.

[Effects of the Invention] According to the present invention, a temperature sensor embedded in the cylindrical portion of a crimp terminal is attached to a terminal plate connected to a contact block to which a contact is attached, and the output circuit is operated by this temperature sensor. When the contact wears out and reaches its lifespan limit, and its contact resistance increases, the temperature of the contact, its vicinity, or the terminal board connected to the contact block increases, and this is detected.
It can issue or display an alarm, and in the case of an electromagnetic contactor, it can be released. Furthermore, if a temperature sensor is connected in parallel to the relay unit, it is also possible to detect the lifespan of a specific contact among the multi-pole contacts. Furthermore, since the temperature sensor is tightened with a terminal screw on the terminal board along with the crimp terminal of the electric wire that connects to the external circuit, this tightening can detect not only the life of the contact but also the temperature rise due to loosening of the part.

Furthermore, since the temperature sensor is detachable, it is also possible to remove the temperature sensor when performing maintenance or inspection of the electromagnetic contactor.

[Brief explanation of the drawing]

1 to 6 show an embodiment of the contact life detection device according to the present invention, FIG. 1 is a longitudinal sectional view showing one embodiment, and FIG.
4 to 4 show an embodiment of the temperature sensor, FIG. 2 is a perspective view, FIG. 3 is a partially sectional plan view, and FIG. 4 is a side view.
Figures 5 and 6 are wiring diagrams showing two examples installed in electromagnetic contactors, respectively, and Figure 7 is a characteristic diagram showing a time-temperature curve showing the relationship between contact usage time (number of times of opening and closing) and temperature rise. ,
Figures 8 to 10 show an example of a conventional contact life detection device, in which Figure 8 is a vertical cross-sectional view of an electromagnetic contactor, and Figures 9 and 10 are horizontal views showing the operation of the contact life detection device, respectively. It is. ■ Fixed contact, 2 Fixed contact block, 3 Terminal board, 3a Terminal screw, 4 Movable contact, IO electromagnetic coil, 14 Temperature sensor, 14a Thermistor, 14b Thermocouple, 22
・Alarm/display device. Figure 1 Figure 3 Figure 4 Figure 5 Figure 6-cIJO L)L)Q

Claims (1)

[Claims] 1) A fixed contact block to which a fixed contact is attached and a terminal board to which a terminal screw is screwed are combined, and the lifespan of both contacts is detected while current is being applied between the fixed contact and a movable contact facing the fixed contact. A contact life detection device that includes a temperature sensor embedded in a cylindrical portion of a crimp terminal with an insulator and removably attached to the terminal board with a terminal screw, an output circuit that is opened and closed by the output of this temperature sensor, and this output. A contact life detection device comprising an alarm/display device connected to an output end of a circuit.