JPH04218230A - Contact deterioration detector - Google Patents

Abstract

PURPOSE:To facilitate decision of deterioration of a contact portion and the time of replacement thereof by installing such means that detects a current of the contact portion, makes a short circuit with a switch interlocking to the contact portion so that the contact portion is opened and thereupon, the switch is opened to detect k arc current. CONSTITUTION:A current detection means 2 can detect a current when a contact portion 1 is closed, but as a means 2 is shorted because a switch 3 is closed, there are no inputs in a deterioration detecting circuit 4. On the other hand, if the contact portion 1 is deteriorated, the time of continuance of arc at the breaking time extends corresponding to the degree of advance of determination and resultantly, the breaking time extends so that a current is detected by the means 2 even after the contact portion 1 is opened. In this case, the switch 5 is opened as it interlocks to the open of the contact portion 1 and there is an input in the circuit 4 in the continuance time of arc so that deterioration of the contact portion 1 is detected. It is thereby possible to facilitate decision making of determination on deterioration of the contact portion 1 and a replacement time thereof.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact deterioration detection device applied to circuit breakers and other current switches.

0002

2. Description of the Related Art Deterioration of a current switch and the timing of its replacement have been determined by checking the amount of wear on the contacts or measuring insulation.

0003

[Problems to be Solved by the Invention] However, there is a drawback that it is not easy to judge deterioration and replacement timing. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a contact deterioration detection device that can easily determine the deterioration of a contact and when it should be replaced, and that has a simple configuration.

0004

[Means for Solving the Problems] The present invention provides a contact portion, a current detection means connected in series to the contact portion, and a current detection means connected in parallel to the current detection means and interlocked with the opening/closing operation of the contact portion. A deterioration detection circuit is provided, which is connected in parallel to the switch and detects the output current of the current detection means when the switch is open.

[0005]

According to the structure of the present invention, when the contact portion is closed, the current detection means can detect current, but since the switch is closed and the current detection means is short-circuited, there is no input to the deterioration detection circuit. On the other hand, if the contact portion is deteriorated, the arc duration at the time of interruption increases depending on the degree of deterioration, and the interruption time becomes longer. Therefore, the current is detected by the current detection means even after the contact portion is opened. In this case, since the switch is opened in conjunction with the opening of the contact portion, the arc duration time is input to the deterioration detection circuit, and deterioration is detected. Therefore, the deterioration of the contact portion and the time for replacement can be easily determined, and this can be achieved with a simple configuration.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be explained with reference to FIGS. 1 to 3. That is, this contact deterioration detection device includes a contact portion 1, a current detection means 2, a switch 3, and a deterioration detection circuit 4. The contact portion 1 is an example of a contact portion of a circuit breaker (not shown) connected to the electric line 5. That is, the contact portion 1 is opened and closed by the on/off operation of the circuit breaker, and when an abnormal current flows through the electric line 5, a trip operation is performed and the contact portion 1 is opened.

The current detecting means 2 is connected in series to the contact portion 1, and is exemplified by a current transformer. This current transformer provides an output proportional to the current in the electric line 5. switch 3
is connected in parallel to the current detection means 2 and opens and closes in conjunction with the opening and closing operations of the contact section 1. Embodiments use microswitches, for example, which are incorporated into a circuit breaker and arranged to interlock with a movable contact or latch link of the circuit breaker.

The deterioration detection circuit 4 is connected in parallel to the switch 3 and detects the output current of the current detection means 2 when the switch 3 is open. On the input side of the deterioration detection circuit 4, a high resistance 6 is connected in parallel to the switch 3, a diode bridge 7 is connected in parallel to the high resistance 6, a capacitor 8 is connected in parallel to the diode bridge 7, and a high resistance 6 is connected in parallel to the high resistance 6. A deterioration detection circuit 4 is connected to. That is, by passing the output current of the current detection means 2 through the diode bridge 7, a DC voltage of approximately 0.6V is obtained and inputted to the deterioration detection circuit 4. Capacitor 8 is for removing ripple components. Further, the high resistance 6 is for removing the induced voltage generated across the diode when there is no output from the current detection means 2. The deterioration detection circuit 4 has a time detection means for detecting the output time (t4 to t6 in FIG. 3c) of the current detection means 2, and a comparison means for comparing the output time with a preset time. When the set time has elapsed, it is determined that the contact portion 1 has deteriorated and a signal is output to issue an alarm for replacement of the contact portion 1, etc.

FIG. 2 is a time chart when the contact section 1 is healthy and when it is deteriorated, and a in the figure shows the operating state of the switch 3, which is closed in conjunction with the contact section 1 being closed at time t1. , and is opened in conjunction with the opening of the contact portion 1 at time t2. Figure b shows the output of the current detecting means 2 when the contact section 1 is healthy and open; the current is detected immediately upon closing of the contact section 1, and becomes zero when the contact section 1 is opened. In this case, the current detection means 2 is connected in parallel with the switch 3, and the switch 3 is closed in conjunction with the contact portion 1, so that the input to the deterioration detection circuit 4 is zero. Figure c shows the output when the current detection means 2 is open when the contact part 1 has deteriorated, and the current starts to be detected a little later than the contact part 1 is closed, and even after the contact part 1 is opened, the current is detected at time t3. Output due to arc current appears until . In other words, as the deterioration of the contact part 1 progresses, the duration of the arc during interruption increases and the interruption time becomes longer, but this is because the recovery of the insulation around the contact deteriorates, causing the arc time to increase and continue for several cycles. It is. Figure d shows the deterioration detection circuit 4.
is the signal input to the point t when the switch 3 is opened.
2 until time t3 when the arc current disappears, and this becomes the output time of the current detection means 2. Further, FIG. 3 shows a waveform diagram, and figure a shows the current I1 flowing through the contact part 1 when the contact part 1 is healthy, and the arc voltage V1 and recovery voltage V2 after the contact part 1 is opened at time t4. There is. Figure b
is the arc voltage V1 after the contact part 1 is opened when the contact part 1 is deteriorated.
', indicating that it continues for several cycles from time t4 to time t6. This is because, as described above, the arc duration time becomes longer due to deterioration of the contact portion 1. Figure c shows the voltage appearing at the input terminal of the deterioration detection circuit 4 after the switch 3 is opened, and the input voltage is generated while the arc voltage in figure b appears, that is, the output time of the current detection means 2. It shows.

According to this embodiment, when the contact section 1 is closed, the current detection means 2 can detect the current, but the switch 3
Since the current detection means 2 is short-circuited because the current detection means 2 is closed, there is no input to the deterioration detection circuit 4. On the other hand, if the contact part 1 has deteriorated, the arc duration at the time of interruption will increase depending on the degree of deterioration, and the interruption time will become longer. To detect. In this case, contact part 1
Since the switch 3 is opened in conjunction with the opening of the switch 3, the arc duration time is input to the deterioration detection circuit 4, and the deterioration is detected. Therefore, the deterioration of the contact portion 1 and the time to replace it can be easily determined, and this can be achieved with a simple configuration. As a result, the arc duration can be extracted as a signal with a simple configuration, and when this embodiment is used for preventive maintenance, a deterioration warning can be issued based on the length of the arc duration, and it can also be used for protection coordination. In this case, for example, it is possible to determine whether interruption is possible based on the length of the arc duration and activate a higher-level protection function.

Although a microswitch is used as the switch 3, a relay may also be used. Alternatively, a DC voltage may be obtained by connecting another diode in the forward direction to the output end of the diode bridge 7 and passing current through it.

0012

Effects of the Invention The contact deterioration detection device of the present invention short-circuits the current detection means for detecting the current in the contact portion with a switch that is linked to the contact portion, and when the contact portion is opened, the switch is opened to prevent arcing. Since the current is detected by the current detection means, there is an effect that the deterioration of the contact portion and the time for replacement can be easily determined with a simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the present invention.

FIG. 2 is a time chart of each part when the contact part is healthy and when it is deteriorated.

FIG. 3 is a waveform diagram of each part when the contact part is healthy and when it is deteriorated.

[Explanation of symbols]

1 Contact part 2 Current detection means 3 Switch 4 Deterioration detection circuit

Claims (1)

[Claims] 1. A contact section, a current detection means connected in series to the contact section, a switch connected in parallel to the current detection means and opened/closed in conjunction with the opening/closing operation of the contact section; A contact deterioration detection device comprising: a deterioration detection circuit connected in parallel to a switch to detect an output current of the current detection means when the switch is open.