JP2004080930A - Disconnection spark detection circuit and breaker using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a disconnection spark detection circuit that detects spark discharge occurring in the coating of a wire, and a breaker that prevents the firing or the like of the coating of the wire from occurring by blocking a cable way in detecting spark discharges. <P>SOLUTION: A current detection means 5 detects a current flowing to the wires L, L that connect a load 1 and an AC power supply AC by using a current transformer 3, and outputs a voltage signal of a level, corresponding to the magnitude of the detected current from an I/V conversion circuit 4. If the time the output voltage of the current detecting means 5 drops to a prescribed value or below is within a fixed time interval, a microcomputer 6 determines the time as being a non-current block, and if a next block exists where no current flows within a prescribed time, after the determination of the former non-current block, the microcomputer determines that non-current blocks exist successively generated. When the number of the successive generations of the non-current blocks reaches a prescribed number, the microcomputer determines that disconnection has occurred in the cores of the wires L, L, and generates a spark detection signal. A breaker mechanism 8 blocks the cable way, receiving the spark detection signal. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a disconnection spark detection circuit that detects the occurrence of spark discharge in an electric wire caused by a partial disconnection or a disconnection of a core wire of an electric wire, and a circuit breaker that disconnects an electric circuit when a disconnection spark is detected.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there has been provided a circuit breaker that detects a discharge short circuit that occurs when insulation between a core wire of a wire connecting a load and a power supply (for example, an AC power supply) is broken down due to tracking or the like and cuts off the circuit. See JP-A-10-14086).
[0003]
[Problems to be solved by the invention]
The circuit breaker described above detects a discharge short-circuit caused by insulation breakdown of an electric wire, and cannot detect a disconnection or a partial disconnection that occurs in a sheath of a core wire of the electric wire due to use progress.
[0004]
In other words, in a wire to which a load with a relatively large current is connected, if the core wire is deteriorated and approaches a disconnected state (semi-disconnected state) during use, the core wire is intermittently disconnected due to vibration applied from the outside. Sometimes. In this case, a spark discharge occurs due to the disconnection, and the coating (eg, vinyl chloride) of the electric wire abnormally generates heat, and the heat generated from the coating accumulates inside, and eventually the electric wire coating explosively ruptures and burns. Then, there was a problem of causing a fire.
[0005]
There is a need for a disconnection spark detection circuit that can detect a spark discharge caused by a disconnection or a partial disconnection of a core of an electric wire that cannot be seen from the outside, and a disconnection device that disconnects an electric circuit.
[0006]
The present invention has been made in view of the above points, and an object of the first and second aspects of the present invention is to detect the occurrence of spark discharge caused by a broken or partially broken core of an electric wire. Another object of the present invention is to provide a disconnection spark detection circuit capable of detecting a spark discharge using the disconnection spark detection circuit according to the first and second aspects of the present invention. An object of the present invention is to provide a shutoff device that can shut off and prevent burning of a coating of an electric wire beforehand.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a disconnection spark detection circuit according to the first aspect of the present invention detects a current flowing through an electric wire forming an electric path connecting a load and an AC power supply, and corresponds to the magnitude of the detected current. A current detecting means for outputting a voltage signal of a level, and if the time during which the output voltage of the current detecting means is equal to or less than a predetermined time is within a predetermined time, it is determined that there is no current section; If there is a next section where it is determined that there is no current within the time, it is determined that there is a continuous discharge. If the number of continuous occurrences of the section that is determined to be no current reaches a predetermined number, it is determined that there is a spark discharge in the electric wire and a spark detection signal is generated. And determination means for outputting
[0008]
In the spark spark detection circuit according to a second aspect of the present invention, in the first aspect of the present invention, the determining means A / D converting means for A / D converting a voltage signal from the current detecting means, and A / D converting means. It is determined that there is no change when the voltage value to be converted and output is within the predetermined voltage range, and the difference from the voltage value at the time of the previous sampling is within the certain voltage range, and when this non-change state continues for a predetermined time, A judgment function of judging a current-free section and outputting the judgment result, and counting up each time the judgment result is output, and outputting the next judgment result of no current within a predetermined time from the previous count-up. A counter function for clearing the count value if not present, and outputting the spark detection signal when the count number of the counter function reaches a predetermined number.
[0009]
According to a third aspect of the present invention, the disconnection spark detection circuit according to the first or second aspect is used, and when a spark detection signal of the disconnection spark detection circuit is input, the circuit is inserted into an electric circuit connecting the load and the AC power supply. It is characterized in that it is provided with blocking means for opening the switch means.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described with reference to embodiments.
[0011]
FIG. 1 shows an example of a breaking device using a breaking spark detection circuit 2 for detecting a half-break or break of a core wire of an electric wire L, which connects between a load 1 and an AC power supply AC, and a breaking mechanism 8 as breaking means. 1 shows a schematic configuration of an embodiment.
[0012]
The disconnection spark detection circuit 2 includes a current transformer 3 for generating a secondary output corresponding to the magnitude of a load current flowing through the electric wire L, and an I / V conversion circuit for converting a secondary output current of the current transformer 3 into a voltage. And a determination means for taking in a voltage signal corresponding to the magnitude of the load current output from the current detection means 5 and determining the presence / absence of a disconnection described later from the voltage signal. It comprises a microcomputer (hereinafter abbreviated as a microcomputer) 6 and a power supply circuit 7 which takes in AC power from an AC power supply AC, converts the AC power into a predetermined DC, and supplies the DC as a power supply + V to the microcomputer 6.
[0013]
As shown in FIG. 2, the shut-off mechanism 8 includes an electromagnetic switch 9 and a thyristor 10 for turning on / off the energization of an exciting coil 9a of the electromagnetic switch 9, and a normally closed switching contact of the electromagnetic switch 9 S and S are respectively inserted in series in a pair of electric paths as switch means. The gate of the thyristor 10 is connected to an output port of the microcomputer 6 from which a spark detection signal is output.
[0014]
The output port of the microcomputer 6 is normally at "L" level, so that the thyristor 10 is in the off state, and shuts off the exciting current to the exciting coil 9a of the electromagnetic switch 9. When a spark detection signal of “H” level is output from the output port at the time of disconnection determination, which will be described later, the thyristor 10 is triggered and turned on, and an exciting current flows through the exciting coil 9 a of the electromagnetic switch 9. Is opened.
[0015]
The connection point of the power input terminal of the power supply circuit 7 of the disconnection spark detection circuit 2 to the electric circuit is between the switching contacts S, S of the breaking mechanism 8 and the AC power supply AC. From the power supply to the microcomputer 6 can be maintained.
[0016]
The microcomputer 6 incorporates an A / D converter 60 for A / D converting the output voltage of the I / V conversion circuit 4 of the current detecting means 5 as shown in FIG. It has an arithmetic processing unit 61 that samples and takes in digitized voltage values at predetermined intervals, and realizes a determination function and a counter function for performing disconnection determination based on the voltage values by executing a program. .
[0017]
Next, the operation of the present embodiment will be described.
[0018]
First, in the circuit of FIG. 2, when the load 1 to be connected is a resistive load, the load voltage waveform (almost the waveform of the AC power supply AC) shown when the electric wires L, L are normal (the normal section in FIG. 3A). 3), a current having a sine waveform corresponding to a change in the load voltage flows as shown in FIG. In this case, it is assumed that a load current of, for example, ± 10 A (an example for explanation, not a limited value) flows. Correspondingly, for example, the output of the I / V converter 4 input to the A / D converter 60 is, for example, a voltage having a waveform that rises and falls to ± 2.5 V around 2.5 V ( It is an illustrative example and not a limiting value).
[0019]
If a break (semi-break) occurs in the core wires of the electric wires L, L (the abnormal time section in FIG. 3A), the disconnection X shown in FIG. Although a current will flow due to spark discharge between the opposing core wires at the point X, the load current waveform is substantially zero in a section where the load voltage has dropped below a predetermined voltage (for example, near the zero crossing of the AC power supply voltage). As shown in FIG. 3B, the waveform is different from the change in the load voltage waveform.
[0020]
The arithmetic processing unit 61 of the microcomputer 6 detects a non-current section in which the current caused by the spark discharge stops flowing from the conversion output of the A / D converter 60 and makes a disconnection determination. The determination operation will be described based on the flowchart shown in FIG.
[0021]
First, when the power is turned on (step S1), the microcomputer 6 performs an initialization process (step S2). After this initialization, the A / D converter 60 in the microcomputer 6 samples the input voltage at a constant cycle (for example, 200 μs cycle) and performs A / D conversion processing (step S3). On the other hand, the arithmetic processing unit 61 takes in the A / D-converted voltage value output from the A / D converter 60, and determines the non-change processing in step S6 or the change processing in step S7 according to the voltage value. Is performed (step S5).
[0022]
In this determination processing, if the A / D-converted voltage value is in the range of, for example, 2.3 V or more and 2.7 V or less, the non-change processing is selected. In this non-change processing, the fetched voltage value is compared with the voltage value at the previous sampling that is temporarily held, and the voltage value at the previous sampling is, for example, ± 0.04 V (use (2 bits of A / D conversion to be performed), it is determined that the voltage value is the same as the voltage value at the time of the immediately preceding sampling, that is, that the voltage value does not change. If it is not determined that there is no change in the previous sampling value, the process goes through step S8 of the next output process, returns to step S3, passes through the A / D conversion process in step S4, and returns to step S5. Is performed again, and if it is determined again in this determination process that there is no change processing in step S6, the change processing is performed on the voltage value A / D converted in the current sampling. Thereafter, the non-change processing of step S6 is repeatedly performed through the determination processing of step S5, and if the determination that there is no change is continuously performed within 1 ms to 50 ms, this section is determined as a currentless section. Here, the upper limit is set to 50 ms in consideration of the case where a mechanical force is applied to the electric wire L and a continuous disconnection state is continued. Of course, the upper limit may be 50 ms or more or less, but the electric circuit is interrupted. An upper limit is always set in order to eliminate the case where the unchanged state continues continuously as in the case. On the other hand, the lower limit of 1 ms is set to eliminate transient phenomena such as instantaneous interruption.
[0023]
When the determination result of the no-current section is output in the no-change processing, the count value of the counter function of the arithmetic processing unit 61 is counted up as the number of times the determination result is output in the next output processing of step S8. Is set to 1.
[0024]
Then, the process returns to step S3 to repeat the above-described processing. However, if the determination result of the next no-current section is not output within 10 ms (corresponding to a half cycle of the AC power supply AC of 50 Hz), the process proceeds to step S8. In the output processing, the count value of the counter function is cleared. On the other hand, if the determination result of the no-current section is output again within 10 ms, the count value of the counter function is counted up in the output processing in step S8, and the count value reaches a predetermined number (for example, three times). It is determined whether or not the processing has been performed. If the predetermined number has not been reached, the process returns to step S3 and the above-described processing is repeated. When the count value of the counter function in the output processing of step S8 becomes "3", the arithmetic processing unit 61 outputs a spark detection signal to the gate of the thyristor 10 by the end processing of step 9, and turns on the thyristor 10. As a result, an exciting current flows to the exciting coil 9a of the electromagnetic switch 9 via the thyristor 10, and the electromagnetic switch 9 opens the switching contacts S, S, and cuts off the electric circuit between the load 1 and the AC power supply AC. . By this interruption, it is possible to prevent ignition of the coating caused by spark discharge caused by half-break or break of the electric wires L, L.
[0025]
By the way, if the A / D conversion output voltage is determined to be less than 2.3V or more than 2.7V in the determination processing in step S5, the change processing in step S7 is selected. In this change process, the peak value of the load current is checked from the A / D conversion output voltage, and when the load current value drops sharply, the operation of the spark discharge detection processing is stopped.
[0026]
In the above embodiment, signal processing is performed using the microcomputer 6, but discrimination of the detected current is performed using a comparator, and a circuit that does not depend on the microcomputer 6 such as setting a non-current section using a timer or the like. Even if it is configured, the disconnection spark detection circuit 2 can be configured.
[0027]
In the above-described embodiment, the disconnection spark detection circuit 2 is configured. However, the disconnection spark detection circuit 2 can of course be applied to a device that performs disconnection occurrence notification and the like. It is not particularly limited to the embodiment.
[0028]
【The invention's effect】
The invention according to claim 1, wherein current detection means for detecting a current flowing through an electric wire forming an electric circuit connecting a load and an AC power supply, and outputting a voltage signal having a level corresponding to the magnitude of the detected current, If the time during which the output voltage of the detecting means becomes equal to or less than a predetermined time is within a predetermined time, it is determined that there is no current section, and there is a section where the next no current is determined within the predetermined time after determining that there is no current section. When the number of consecutive occurrences of the section determined to be no current reaches a predetermined number, the electric wire is determined to have a spark discharge and a spark detection signal is output. Disconnection or semi-disconnection of the core wire can be reliably detected, thereby preventing the ignition of the coating of the wire caused by spark discharge caused by the disconnection or semi-disconnection of the core wire. Sensors for It can be used in.
[0029]
According to a second aspect of the present invention, in the first aspect, the determining means A / D converting means for A / D converting a voltage signal from the current detecting means, and a voltage converted and output by the A / D converting means. If the value is within the predetermined voltage range, and the difference from the voltage value at the time of the immediately preceding sampling is within the constant voltage range, it is determined that there is no change. A judgment function for judging and outputting the judgment result, and counting up each time the judgment result is output, and if there is no output of the next no-current judgment result within a predetermined time from the previous count up, the count value is counted. A counter function for clearing, and when the count number of this counter function reaches a predetermined number, the above-mentioned spark detection signal is output, so that a circuit configuration for the judgment processing is realized using a microcomputer. Possible and it can reduce the size of the circuit.
[0030]
According to a third aspect of the present invention, when the disconnection detection output of the disconnection spark detection circuit is input using the disconnection spark detection circuit of the first or second aspect, the switch means inserted in the electric circuit connecting the load and the AC power supply is provided. Since the disconnection means for opening drive is provided, when spark discharge occurs due to disconnection or partial disconnection in the core wire of the electric wire, it is possible to automatically disconnect the electric circuit between the load and the AC power supply, It is possible to provide a shut-off device capable of preventing explosive rupture of a coating due to gas generated from the coating due to spark discharge in an electric wire and preventing fire from occurring due to ignition of the coating.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an embodiment of the present invention.
FIG. 2 is a configuration diagram showing a specific circuit of a main part of the above.
FIG. 3 is a waveform diagram of each part for explaining the operation of the above.
FIG. 4 is a flowchart for explaining the above operation.
[Brief description of reference numerals]
DESCRIPTION OF SYMBOLS 1 Load 2 Disconnection spark detection circuit 3 Current transformer 4 I / V conversion circuit 5 Current detection means 6 Microcomputer 7 Power supply circuit 8 Interruption mechanism AC AC power supply L Electric wire

Claims (3)

Current detecting means for detecting a current flowing through an electric wire forming an electric circuit connecting the load and the AC power supply, and outputting a voltage signal having a level corresponding to the magnitude of the detected current; If the following time is within a predetermined time, it is determined that there is no current section, and if there is a section that is determined to be the next no current within a predetermined time after the determination of no current section, it is determined that continuous occurrence occurs. A disconnection spark detection circuit, comprising: determination means for determining that the electric wire has spark discharge and outputting a spark detection signal when the number of consecutive occurrences of a section determined to be a current reaches a predetermined number. An A / D converter for A / D converting the voltage signal from the current detector; a voltage value converted and output by the A / D converter being within a predetermined voltage range; A determination function that determines that there is no change when the difference from the voltage value at the time of sampling is within a certain voltage range, and determines that the current state is a no-current section when the non-change state continues for a predetermined time, and outputs the determination result; It has a counter function that counts up each time a judgment result is output, and clears the count value if there is no output of the next no-current judgment result within a certain period of time from the previous count-up. 2. The disconnection spark detection circuit according to claim 1, wherein when the number reaches a predetermined number, the spark detection signal is output. A disconnection means is provided for using the disconnection spark detection circuit according to claim 1 or 2, wherein when a detection signal of the disconnection spark detection circuit is input, the switch means inserted into an electric circuit connecting the load and the AC power supply is opened. A blocking device.

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