JP2010021081A - Overcurrent circuit breaker, and interruption method of overcurrent - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an overcurrent circuit breaker and an interruption method of overcurrent, with sufficient consideration of operating characteristics depending on heat accumulation as being so-called an electronic type, and can surely carry out protection of electric wires from heat of overcurrent. <P>SOLUTION: The overcurrent circuit breaker and interruption method of overcurrent, is provided with a comparison means 12 comparing an electric current value detected by an electric current detection means 1g with an electric current value predetermined beforehand, a determination means 13 determining a magnitude of a detected current value to the predetermined current value based on the compared result from the comparison means 12, and a measuring means 14 increasing the current in case the detected electric current value is greater than the predetermined electric current value, and reducing the current in case the detected electric current value is less than the predetermined electric current value, based on an indication from the determination means 13. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an overcurrent circuit breaker and a method for interrupting an overcurrent provided to ensure safety when a current exceeding a specified value flows in an electrical wiring.

  Overcurrent may flow through the electrical wiring due to excessive use of electricity (overload) or short circuit. When the overcurrent flows, heat is applied to the electrical wiring. If this state is left unattended, a dangerous state such as a fire may occur. Therefore, there is provided a device (hereinafter referred to as “overcurrent breaker”) that automatically cuts off electricity when an overcurrent flows for the purpose of protecting the electrical wiring. As this overcurrent circuit breaker, for example, a current limiter, a circuit breaker (breaker), or an earth leakage circuit breaker with an overcurrent protection function can be cited.

  Regarding the operation principle of the overcurrent circuit breaker, there is a so-called “bimetal system” as a typical principle. In this “bimetal system”, a metal plate called “bimetal” is assembled by bonding two types of metal plates having different thermal expansion coefficients in an overcurrent circuit breaker. The bimetal heat when electricity flows, bends to either the thermal expansion coefficient of different metal plate.

  A current that can be supplied in advance is determined in advance in each electrical wiring in which an overcurrent circuit breaker is originally provided. When such a large current exceeding the rated current flows through the electric wire, the heat generation amount and the bending amount of the bimetal provided in the overcurrent circuit breaker increase in accordance with the magnitude of the flowing current. When the bimetal reaches a predetermined amount of bending, the bimetal contacts and pushes the operating plate, and when the joining piece is removed, the contact tripping device is operated to interrupt the circuit through which current flows.

  As described above, in the bimetal system, the opening of the contact is controlled based on the heat generated by the overcurrent and the curvature accompanying the heat generation by utilizing the above-described physical properties of the bimetal. Therefore, if a current close to the upper limit of the rated current flows frequently in a short time, the bimetal is not sufficiently cooled and the circuit is interrupted at a short interval. However, since the overcurrent circuit breaker is intended to protect the electrical wiring by heat, such an operating characteristic rather matches the nature of the overcurrent circuit breaker.

On the other hand, it is not a method of physically and mechanically interrupting the circuit using such bimetal, but it detects the value of the current flowing in the electrical wiring and operates the contact tripping device electrically when an overcurrent flows In other words, there is an electronic overcurrent circuit breaker (see Patent Document 1).
JP 2008-78002 A

  However, in the electronic overcurrent circuit breaker disclosed in Patent Document 1 described above, the following points are not considered.

  In other words, this electronic overcurrent circuit breaker is characterized in that it detects the current flowing through the electrical wiring, and when the current value is larger than the contract current value, it performs disconnection processing of the electric circuit based on a predetermined time limit characteristic. is there. The “time limit characteristic” here means that, for example, when the rated current is 60 A, the current operates at 6% at a current of 200% (120 A) of the rated current, and becomes 125% (75 A) of the rated current. In that case, it refers to the characteristic of operating within 120 minutes.

  By controlling according to this “time-limited characteristics”, it is not possible to take advantage of the operational characteristics due to the excellent heat accumulation in the bimetal system as described above, and the overcurrent circuit breaker is originally intended to protect the electrical wiring from the heat. It will diverge.

  The present invention has been made to solve the above problems, and the object of the present invention is a so-called electronic type, which sufficiently reflects the operation characteristics due to heat accumulation, and protects the electrical wiring from heat due to overcurrent. It is an object to provide an overcurrent circuit breaker and a method for interrupting an overcurrent that can be reliably performed.

  The first feature according to the embodiment of the present invention is that, in the overcurrent circuit breaker, a comparison means for comparing a current value detected by the current detection means with a predetermined current value, and a comparison result from the comparison means. Based on the determination means for determining the magnitude of the detected current value with respect to the specified current value, and based on an instruction from the determining means, if the detected current value is larger than the specified current value, the detection current value is increased. And a weighing means for reducing the weight when it is smaller.

  A second feature of the embodiment of the present invention is that, in the overcurrent interruption method, a step of detecting a current flowing by the current detection unit, a current value detected by the current detection unit, and a predetermined current value are provided. In the comparison means, a step in which the determination means determines the magnitude of the detected current value with respect to the specified current value based on a comparison result from the comparison means, and a detection current value greater than the specified current value by the determination means When it is determined, the measuring means increases according to the magnitude based on the instruction from the determining means. When the determining means determines that the detected current value is smaller than the specified current value, A step in which the weighing means reduces the fixed amount based on the instruction, and a step in which the main contact is opened when the total weighing stored in the weighing means becomes larger than a predetermined amount. And a flop.

  According to the present invention, an overcurrent circuit breaker and a method for interrupting an overcurrent, which are so-called electronic type, can sufficiently reflect the operation characteristics due to heat accumulation and can reliably protect the electric wiring from heat due to overcurrent. Can be provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing an overall configuration of an overcurrent circuit breaker 1 according to an embodiment of the present invention. The “overcurrent circuit breaker” mentioned here includes a current limiter, a circuit breaker (breaker), or a leakage breaker as described above.

  As shown in FIG. 1, an overcurrent circuit breaker 1 includes a CPU (Central Processing Unit) 1a, a ROM (Read Only Memory) 1b, a RAM (Random Access Memory) 1c, and an input / output interface 1d via a bus 1e. It is connected. The input / output interface 1d is connected with input means 1f, current detection means 1g, storage means 1h, and drive unit control means 1i. A signal is transmitted to a contact tripping device or the like that does not perform control of the operation such as opening the contact.

  The CPU 1a reads and executes a boot program for starting the overcurrent breaker 1 from the ROM 1b based on the input signal from the input means 1f, and reads various operating systems stored in the storage means 1h. The CPU 1a reads a program and data stored in the RAM 1c, the storage unit 1h, etc., loads the program and data into the RAM 1c, and performs a series of processing such as data calculation or processing based on a program command read from the RAM 1c. This is a processing device to be realized.

  The input means 1f is a switch for turning on or off the power supply of the overcurrent circuit breaker 1, for example. In addition, the switch is a switch for energizing the current limiter and the circuit breaker (breaker) again after an overcurrent or the like flows and the energization to the electric wiring is interrupted. When the input means 1f is operated, an input signal indicating that energization has been started based on the operation of the operator is created and transmitted to the CPU 1a via the bus 1e.

  The current detection unit 1g is a unit that detects a current flowing in the electrical wiring. The detection method is, for example, a method in which a current transformer (CT) in which a coil is wound around a magnetic core is used as a sensor, or a magnetoelectric conversion element is disposed in a gap portion of the magnetic core and the magnetic flux generated in the gap portion due to a current to be measured. Any method, such as a Hall element for measuring the density and detecting the flowing current, may be used. The current value detected by the current detecting means 1g (hereinafter, appropriately referred to as “detected current value”) is transmitted to the CPU 1a via the input / output interface 1d.

  The storage unit 1h is composed of a semiconductor or the like, and stores programs and data executed by the CPU 1a. The signal read from the storage unit 1h is transmitted / received to / from the CPU 1a via the input / output interface 1d and the bus 1e.

  In the overcurrent circuit breaker 1 according to the embodiment of the present invention, an overcurrent circuit breaker program is stored in the storage unit 1h, and is read and executed by the CPU 1a, whereby the overcurrent circuit breaker unit 10 is 1 will be implemented. In the following, a method for controlling the operation until the overcurrent is interrupted according to the flow prescribed in the overcurrent interruption program will be described. For example, an overcurrent interruption circuit is provided in the overcurrent breaker 1 to prevent overcurrent. It is good also as blocking.

  As shown in FIG. 2, the internal configuration of the overcurrent interrupting means 10 mounted on the overcurrent circuit breaker 1 includes a receiving means 11, a comparing means 12, a judging means 13, a weighing means 14, a transmitting means 15, Consists of. The operation of each means constituting these overcurrent interrupting means 10 will be described together with the following control method for interrupting when an overcurrent occurs using the flowchart shown in FIG.

  The current detection means 1g is connected to the electrical wiring and constantly detects the magnitude of the current flowing through the electrical wiring while the electrical wiring is energized (ST1). The detected current value detected by the current detection unit 1g is transmitted to the comparison unit 12 of the overcurrent cutoff unit 10 via the reception unit 11.

  The comparison means 12 is a current value of a rated current (hereinafter referred to as “specified current”) defined for the electrical wiring of the overcurrent circuit breaker 1 to which the current detection means 1g is attached from the storage means 1h. Information). Then, the detected current value transmitted from the current detecting means 1g is compared with this specified current value (ST2). It is assumed that the storage unit 1h stores in advance a specified current value for each electrical wiring to which the overcurrent circuit breaker 1 is attached. Further, by changing the value of the specified current value stored in the storage means 1h, the overcurrent circuit breaker 1 can be used at any place regardless of the contract.

  The comparison means 12 in the embodiment of the present invention checks whether or not the detected current value is larger than the specified current value. Therefore, whether the detected current value is larger than the specified current value (YES in ST2) or whether the detected current value is equal to or smaller than the specified current value (NO in ST2), from the determination unit 13 that has received the comparison result. The instructions to the weighing means 14 are different.

  First, when the detected current value is larger than the specified current value (YES in ST2), the determination unit 13 confirms the difference between the detected current value and the specified current value (ST3). This step has a law that the calorific value is proportional to the square of the current, and the overcurrent circuit breaker 1 according to the embodiment of the present invention is capable of performing an operation that sufficiently reflects the operation characteristics due to heat accumulation. This is done to make a current breaker.

  That is, according to the above-mentioned law, for example, when the difference between the detected current value and the specified current value is “1A”, the calorific value is “1 time”, but the difference between the detected current value and the specified current value is “3A”. ", The amount of generated heat is" 9 times "that when the specified current value is flowing in the electrical wiring. Therefore, in the case of an overcurrent circuit breaker using a bimetal as described above, the bimetal becomes more curved as the difference between the detected current value and the specified current value increases (proportional to the square of the difference). become). In order to realize this operating characteristic in an electronic overcurrent circuit breaker, it is necessary to reflect the amount of heat generated when opening the main contact after confirming the difference between the detected current value and the specified current value. For this purpose, the determination means 13 checks how much the difference between the detected current value and the specified current value is when the detected current value is larger than the specified current value.

  The judging means 13 confirms the difference between the detected current value and the specified current value, and instructs the measuring means 14 to increase the accumulation amount according to the difference (ST4). That is, when the determination unit 13 instructs the measuring unit 14 to increase the amount, the determination unit 13 gives an instruction so that it is clear that it is proportional to the square of the difference between the detected current value and the specified current value.

  Here, the term “measurement” is used. For example, a data amount corresponding to the square of the difference between the detected current value and the specified current value from the determination unit 13 is transmitted, and the data amount is referred to as “quantity”. ”Is assumed to be accumulated. However, in addition to such an example, a method may be used in which, for example, a counter is used as the weighing unit 14, and a numerical value corresponding to the square of the difference between the detected current value and the specified current value is accumulated. .

  On the other hand, when the detected current value is equal to or less than the specified current value (NO in ST2), the determining unit 13 instructs the measuring unit 14 to decrease the constant amount (ST5). In this case, unlike the case where the detected current value is larger than the specified current value, the amount of reduction is set to be a fixed amount regardless of the amount of difference between the detected current value and the specified current value. Yes.

  Thus, the instruction from the determination unit 13 to the measurement unit 14 differs depending on whether the detected current value is larger than the specified current value or whether the detected current value is less than the specified current value. In the former case, the amount corresponding to the square of the difference between the detected current value and the specified current value is accumulated in the measuring means 14 so that the difference in the heat generation amount can be accurately reflected in the overcurrent circuit breaker 1. Thus, the electrical wiring can be protected more reliably by heat.

  On the other hand, when the detected current value is less than or equal to the specified current value, only the predetermined amount is reduced and the amount corresponding to the square of the difference between the detected current value and the specified current value is not reduced. For the following reasons.

  That is, if the detected current value is less than the specified current value, it is considered that there is little influence of heat on the electrical wiring. In addition, when bimetal is used, once it is bent by receiving heat, even if the detected current value falls below the specified current value, the heat accumulated in the bimetal is not immediately dissipated, but the amount of bending so far Will not reset immediately. Therefore, in view of such bimetal properties, even in the overcurrent circuit breaker 1 according to the embodiment of the present invention, when the detected current value is equal to or less than the specified current value, the specified current value is larger than the detected current value. It is not appropriate to instruct the weighing means 14 to reduce the weight at a rate that matches the situation. Therefore, when the detected current value is equal to or less than the specified current value, only a predetermined amount is reduced. This makes it possible to more reliably protect the electrical wiring from heat.

  Furthermore, when the detected current value becomes equal to or greater than the specified current value again in a state where the detected current value is equal to or less than the specified current value and the amount accumulated in the measuring means 14 is reduced at a constant rate, The “amount” accumulated in the weighing means 14 is set so as not to be zero. This is an electronic system that does not use bimetal, so when the amount in the weighing means 14 starts to decrease, it is possible to reset the “amount” accumulated in the weighing means 14 so far to zero. However, as described above, such a setting is different from the actual bimetal property. If this setting is made, the accumulated amount becomes zero each time the detected current value becomes less than the specified current value, and when the detected current value exceeds the specified current value, the “amount” is accumulated again from zero. I have to go.

  Such an operating characteristic does not sufficiently reflect the operating characteristic due to heat accumulation unlike the operating characteristic of the overcurrent circuit breaker using the bimetal as described above. Therefore, when the detected current value becomes equal to or less than the specified current value after the detected current value becomes larger than the specified current value, the “amount” accumulated in the measuring means 14 is not set to zero immediately but is constant. When the detected current value becomes equal to or higher than the specified current value again, the setting is made so that the "amount" stored in the measuring means 14 is accumulated again at that time. .

  FIG. 4 is a chart showing an operating state of the overcurrent circuit breaker 1 employing the control method according to the embodiment of the present invention. In this chart, the vertical axis represents the “amount” accumulated in the measuring means 14, and the horizontal axis represents the state of the detected current. In particular, in this chart, a state where the detected current value is equal to or smaller than the specified current value is indicated by “A”, and a state where the detected current value is larger than the specified current value is indicated by “B”. A broken line drawn at a certain amount of position indicates a threshold value at which it is determined that the contact defined in advance in the measuring means 14 is opened. When the amount accumulated in the measuring means 14 reaches or exceeds the amount indicated by this threshold value, it can be determined that an overcurrent flows through the electrical wiring (YES in ST6). The drive unit control means 1i opens the contact via the transmission means 15 and issues an instruction to cut off the flow of electricity (ST7).

  By adopting such a control method, it is not a mechanical overcurrent circuit breaker using bimetal, but it is a so-called electronic type, but it fully reflects the operation characteristics due to heat accumulation, and electric wiring from heat due to overcurrent It is possible to provide an overcurrent circuit breaker and an overcurrent breaking method that can reliably protect the current.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment.

It is a block diagram which shows the whole structure of the overcurrent circuit breaker in embodiment of this invention. It is a block diagram which shows the internal structure of the overcurrent interruption | blocking means in embodiment of this invention. It is a flowchart which shows the flow of control of an overcurrent circuit breaker when an overcurrent flows. It is a chart which shows the operation state of overcurrent circuit breaker 1 in an embodiment of the invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Overcurrent circuit breaker, 10 ... Overcurrent interruption means, 11 ... Reception means, 12 ... Comparison means, 13 ... Judgment means, 14 ... Measurement means, 15 ... Transmission means

Claims (4)

Comparison means for comparing the current value detected by the current detection means with a predefined current value;
Determination means for determining the magnitude of the detected current value with respect to the specified current value based on a comparison result from the comparison means;
Based on an instruction from the determination means, a weighing means that increases when the detected current value is larger than the specified current value, and decreases when the detected current value is smaller than the specified current value;
An overcurrent circuit breaker comprising:   2. The determination unit according to claim 1, wherein when the detection current value is determined to be larger than the specified current value, the determination unit instructs the measurement unit to increase the amount according to the magnitude. Overcurrent circuit breaker.   3. The determination unit according to claim 1, wherein when the determination unit determines that the detected current value is equal to or less than the specified current value, the determination unit instructs the measurement unit to reduce a certain amount. Overcurrent circuit breaker. Detecting the current flowing by the current detection means;
Comparing the current value detected by the current detection means with a predetermined current value in a comparison means;
A step of determining a magnitude of the detected current value with respect to the specified current value based on a comparison result from the comparing means;
When the determination means determines that the detected current value is larger than the specified current value, the measurement means increases the amount according to the magnitude based on an instruction from the determination means, and the detection means detects the detection current value. When it is determined that the current value is equal to or less than the specified current value, the measuring unit reduces the amount by a predetermined amount based on an instruction from the determination unit;
When the total weighing stored in the weighing means becomes larger than a predetermined amount, the step of opening the contact;
A method for interrupting overcurrent, comprising:

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