JPH03148071A - Operating-state monitoring apparatus for electromagnetic contactor - Google Patents

Abstract

PURPOSE:To make it possible to detect the chattering phenomenon generated in an electromagnetic contactor and to improve reliability by processing the waveform of a current flowing through the operating coil of the electromagnetic contactor. CONSTITUTION:When an operating coil 5b of an electromagnetic contactor 5 is conducted, each cycle of the AC has the oscillating waveform having the approximately same amplitudes on the positive side and the negative side in the steady state. When chattering is generated on the contrary, the oscillating waveform, wherein the magnitudes of the amplitude parts are different on the positive side and the negative side at the second cycle in the cycles of the AC flowing through the coil 5b, is obtained. The current waveform is divided in a waveform dividing circuit 20. The waveform on the positive half wave side on the advancing phase side is delayed in delay circuit 21 by a half cycle. The current waveforms on the positive and negative half-cycle sides are added in an adder 22. When a current value IP indicated by the current waveform is larger than a reference current IS which is set larger than IP in a setting part 18, a warning signal Sa is outputted through an output circuit 24 from a comparator 23. In this way, the causes of generating chattering is removed at the early period, and the state wherein the entire unit does not function can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an operating state monitoring device for an electromagnetic contactor that detects chattering in an electromagnetic contactor incorporated in a control center or the like.

(Prior art) For example, in a control center equipped with control and protection functions for electric motors, resistive loads, etc., main circuit devices such as electromagnetic contactors, molded circuit breakers, and current converters are grouped together for each unit circuit. The units are stored in multiple stages, and each unit is equipped with a start/stop indicator lamp, a start operation switch,
It is constructed by providing a display operation panel equipped with a stop operation switch and the like. In addition, in recent years,
In order to be able to adapt to changes in the specifications of the unit, by adopting electronic applied technology, we have created a configuration that allows necessary functions to be set, added, and changed as appropriate among multiple control and protection functions. An example is shown in Figure 8.

That is, FIG. 8 schematically shows the circuit configuration for one unit of the control center, and the main circuit 3 between the three-phase power supply bus 1, which is an AC line, and the motor 2 is equipped with a molded circuit breaker 4. ．． Magnetic contactor 5. Current converter 6 for main circuit current detection
A zero-phase current transformer 7 for ground fault current detection is also provided.

The load side of the molded circuit breaker 4 is connected to the primary side of an operating transformer 8, and the secondary side of this transformer 8 is connected to control buses 9a and 9b.

The control unit 10, which is supplied with power from the control buses 9a and 9b via a DC power supply circuit (not shown), is mainly composed of a logic operation circuit 11 composed of a microcomputer. This logic operation circuit 11 includes a starting operation switch 12 .
It receives each ON signal from the stop operation switch 13 and the normally open auxiliary contact 5a of the electromagnetic contactor 5 via the input circuit 14, and receives each signal from the current converter 6 and zero-phase current transformer 7. The power is received via the A-D conversion circuit 15, and the operating coils b of the electromagnetic contactor 5 are controlled to be energized or disconnected via the output circuit 16. In the memory circuit 17,
It stores control programs and functional data for executing protective operations such as overcurrent, phase loss, undercurrent, and ground fault, as well as control operations such as instantaneous power failure restart and timed restart.
The logic control circuit 11 executes protection operations and control operations based on the control program, functional data, and input signals. The setting unit 18 is composed of a large number of selection switches (not shown) so that the function data to be stored in the storage circuit 17 can be selected as desired at the installation site of the control center.

(Problem to be solved by the invention@) By the way, in such a control center, if a situation arises in which the chattering phenomenon of the electromagnetic contactor 5 occurs, the contacts may be welded.

The entire unit including the electromagnetic contactor 5 may become malfunctioning due to contact dropout or the like.

Therefore, in order to prevent such malfunctions and increase the reliability of the control center,
It is necessary to discover the chattering phenomenon of electromagnetic contactors at an early stage. However, conventionally, there is no device that can detect the chattering phenomenon of an electromagnetic contactor with high reliability, and this point has been an unresolved problem.

The present invention has been made in view of the above circumstances, and its object is to provide an electromagnetic contactor that can accurately detect the chattering phenomenon occurring in the electromagnetic contactor based on the current flowing through its operating coil. The present invention provides an operating condition monitoring device.

[Structure of the Invention (Means for Solving the Problem)] In order to achieve the above object, the present invention provides a waveform detection means for detecting a current waveform flowing in an operating coil of an electromagnetic contactor interposed in an AC line, Waveform processing means for dividing the detected current waveform into positive and negative waves; delay means for delaying the leading phase of each of the divided current waveforms by half a cycle; The configuration includes an adding means for adding the values on the side, and a comparing means for outputting an alarm signal when the current value indicated by the added current waveform is equal to or higher than a set reference level.

(Function) When the operating coil of the electromagnetic contactor is energized, a relatively large inrush current flows for about one cycle at the beginning of the energization, and thereafter a relatively small holding current flows periodically. In this state where the holding current begins to flow, that is, in a state where the attraction operation of the contact section in response to the excitation of the operating coil has been completed, chattering may occur where the attraction operation as described above is performed again. If such chattering occurs, a rush current of about half a cycle will flow through the operating coil with a delay of about half a cycle after the completion of the suction operation.

Therefore, in this case, the alternating current flowing through the operating coil has an oscillating waveform with amplitude portions having different amplitudes on the positive side and negative side in the cycle when chattering occurs.

On the other hand, when chattering does not occur in the magnetic contactor, that is, when the inrush current flows for only about one cycle when the operating coil is first energized, the alternating current flowing through the operating coil is on the positive side in each cycle. The vibration waveform has approximately the same amplitude as the negative side.

The current waveform of the operating coil detected by the waveform detection means is divided into positive and negative waves by the waveform processing means, and the leading phase of the positive and negative current waveforms is delayed by half a cycle by the delay means. , the delayed current waveform and the one on the delayed phase side among the positive and negative current waveforms are added by an adding means. Therefore, the current value indicated by the current waveform added in this way is such that the current flowing through the operating coil has an oscillating waveform with an amplitude equal to that between the positive side and the negative side in each cycle. When the current flowing through the operating coil has vibration waveforms of different magnitudes on the positive side and negative side in the chattering generation cycle, it becomes a relatively large value.

In other words, when chattering occurs in the electromagnetic contactor, the current value indicated by the current waveform added by the addition means as described above becomes relatively large and exceeds the reference level set in the comparison means. An alarm signal is output from the comparison means.

(Embodiment) An embodiment in which the present invention is applied to a control center will be described below with reference to FIGS. 1 to 7. However, in FIG. 1, the parts designated by the same reference numerals as those in FIG. 8 have the same structure and function, and therefore the description thereof will be omitted.

That is, in FIG. 1 showing the circuit configuration of one unit of the control center, the logic operation circuit 11 and the output circuit 16
A detection circuit 19 serving as a waveform detection means interposed between
The current waveform flowing through the operating coil 5b of the electromagnetic contactor 5 is detected through an output circuit 16, and the detected output is given to a waveform dividing circuit 20 as a waveform processing means. This waveform dividing circuit 20 divides a manually input current waveform into positive and negative waves, and supplies each divided current waveform to a delay circuit 21 serving as a delay means. This delay circuit 21 delays the leading phase side of each current waveform divided as described above by half a cycle, and supplies the delayed current waveform and non-delayed current waveform to an adder 22 serving as an adding means.

The adder 22 receives the input current waveform, that is, the delay circuit 2
The delayed current waveform according to 1 and the non-delayed current waveform (the one on the delayed phase side among the current waveforms divided by the waveform dividing circuit 20) are added, and the added current waveform is sent to the comparator 23, which is a comparing means. give. And this comparator 23
compares the current value 1p indicated by the current waveform added by the adder 22 with the reference level current value Is set in advance in the setting unit 18, and when the relationship Ip≧Is is established, the current value (not shown) is determined. An alarm signal Sa is outputted to an external device through the output circuit 24. Note that the comparator 23 is configured to perform the above comparison operation only when the main circuit 3 is powered on.

Now, in the following, only the portions related to the gist of the present invention among the functions of the above configuration will be explained.

That is, when the operating coil 5b of the electromagnetic contactor 5 is energized, in a steady state where no chattering occurs in the electromagnetic contactor 5, a relatively large inrush current is generated at the beginning of the energization, as shown in FIG. The current flows for about one cycle, and after that, a relatively small holding current begins to flow periodically. Therefore, in this case, in each cycle of the alternating current flowing through the operating coil 5b, the positive side and the negative side thereof form an oscillating waveform with one amplitude between the paths.

On the other hand, the state in which the holding current starts to flow after energization to the operating coil 5b as described above, that is, the operating coil 5
If the suction operation of the contact part in response to the excitation of b is once completed, and chattering occurs where the suction operation is performed again, as shown in FIG. This inrush current flows with a delay of about half a cycle after the completion of the suction operation. Therefore, in this case, the alternating current flowing through the operating coil 5b has an oscillating waveform having amplitude portions of different magnitudes on the positive side and the negative side in the second cycle of each cycle.

Now, let us describe the case where chattering occurs in the electromagnetic contactor 5 and a current with a waveform as shown in FIG. 3 flows through the operating coil 5b. As shown in the figure, the current waveform is divided into positive and negative parts, and in the delay circuit 21, the current waveform on the positive half wave side, which is on the leading phase side, is delayed by half a cycle, as shown in FIG. Then, the adder 22 adds the current waveform on the positive half-wave side as shown in FIG. 5 and the current waveform on the negative half-wave side, so that the current waveform as shown in FIG. A current waveform with a relatively large peak value is obtained.

Therefore, as shown in FIG. 6, the reference current Is set in the setting unit 18 is set from the current value Ip shown by the current waveform obtained as a result of addition in the adder 22 when chattering occurs in the electromagnetic contactor 5. If you set it to a large value,
When chattering occurs and the relationship Ip≧Is is established, the comparator 23 outputs the alarm signal Sa through the output circuit 24. As a result, it is possible to know from the above-mentioned alarm signal Sa that chattering has occurred in the electromagnetic contactor 5. This makes it possible to eliminate the cause of chattering at an early stage, and to prevent the occurrence of chattering in the electromagnetic contactor 5 as in the conventional It becomes possible to prevent the entire unit including the electromagnetic contactor 5 from falling into a malfunctioning state due to contact welding, contact falling out, or the like.

In addition, if the chattering does not occur when the electromagnetic contactor 5 is powered on, in other words, the current flowing through the operating coil 5b changes between the positive side and the negative side in each cycle as shown in FIG. If the current waveform has a vibration waveform with an amplitude of 0.05 to 1.0, the current waveform obtained as a result of the addition by the adder 22 becomes approximately zero as shown in FIG. Sa is never output.

[Effects of the Invention] According to the present invention, as is clear from the above description, the chattering phenomenon occurring in a magnetic contactor can be detected with high accuracy by processing the current waveform flowing through the operating coil of the magnetic contactor. At the same time, it has the excellent effect of being able to generate an alarm signal based on the detection result.

[Brief explanation of the drawing]

Figures 1 to 7 show one embodiment of the present invention. Figure 1 is a schematic electrical circuit configuration diagram, and Figures 2 to 7 are current waveform diagrams shown for explaining the operation. be. Moreover, FIG. 8 is a diagram corresponding to FIG. 1 showing a conventional example. 2 In the figure, 1 is the power bus (AC line), 2 is the motor, 3 is the main circuit, 4 is the circuit breaker, 5 is the electromagnetic contactor, 5a is the auxiliary contact, 5b is the operating coil, and 6 is the current converter. 7 is a zero-phase current transformer, 10 is a control circuit, 11 is a logic operation circuit, 17 is a storage circuit, 18 is a setting section, 19 is a detection circuit (waveform detection means), 20 is a waveform division circuit (waveform processing means) ), 21 is a delay circuit (delay means), 22 is an adder (addition means), 23
indicates a comparator (comparison means).

Claims (1)

[Claims] 1. Waveform detection means for detecting the current waveform flowing in the operating coil of the electromagnetic contactor interposed in the AC line, waveform processing means for dividing the detected current waveform into positive and negative, and a waveform processing means for dividing the detected current waveform into positive and negative parts, and a delay means for delaying one on the phase side by half a cycle; an addition means for adding the delayed current waveform and the one on the delayed phase side among the divided current waveforms; 1. An operating state monitoring device for an electromagnetic contactor, comprising: comparison means for outputting an alarm signal when a current value exceeds a set reference level.