JP2018014835A - Overcurrent protector and power supply unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an overcurrent protector capable of preventing an overcurrent from running through a secondary wiring path of a breaker with a power supply part connected.SOLUTION: The overcurrent protector includes a current detection part 10 for detecting an electric current running through a breaker 3 having a power supply part 7 connected with the secondary side; a current control part 11 for executing current limiting to decrease an output current of the power supply part 7 more as a detection current running through the breaker 3 detected by the current detection part 10 is larger.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an overcurrent prevention device and a power supply device that prevent an overcurrent from flowing through a secondary-side wiring path of a breaker to which a power supply unit is connected.

  In a facility such as a house, a main circuit breaker connected to the power system is provided in the distribution board, and power can be supplied via the main circuit breaker. In addition, in the facility, a plurality of branch breakers are connected in parallel to the secondary side of the main breaker as viewed from the main breaker, and various power consuming devices are connected to the secondary side of the branch breakers. Equipment is built.

  When installing a power supply unit such as a solar cell in a facility, as described in Patent Document 1, a dedicated breaker for the power supply unit is added to the secondary side of the main breaker in parallel with the branch breaker and the power supply unit is connected to the dedicated breaker Only being connected is done.

Japanese Patent No. 3531408

  There may be an installation form in which the power supply unit is connected to an existing branch breaker instead of the installation form in which the power supply unit is connected to the dedicated breaker as described above. For example, when the power supply unit is installed outdoors in a facility, the power supply unit can be connected to an outdoor outlet connected to an existing branch breaker.

  FIG. 1 is a diagram illustrating an example of electrical equipment in which the power supply unit 7 is connected to an outdoor outlet (electric outlet 4). As shown in the figure, this electrical equipment includes a main breaker 2 connected to the electric power system 1 and a plurality of branches provided in parallel on the wiring path 8 branched on the secondary side of the main breaker 2 when viewed from the main breaker 2. Breaker 3 (3A-3C). Various electrical devices E are connected to the secondary sides of the branch breakers 3A to 3C. The electric device E is a power consuming device 6 that consumes power, a power supply unit 7 or the like. In FIG. 1, the electrical plug 5A (5) of the power supply unit 7 and the power consuming device are connected to the electrical outlets 4A to 4C (4) connected to the secondary side wiring paths 8 of the branch breakers 3A to 3C. 6 shows an example in which an electric plug 5B (5) of a sprinkler 6A as an example of 6 and an electric plug 5C (5) of a nightlight 6B as an example of a power consuming device 6 are respectively connected.

4 and 5 are diagrams for explaining the current that can flow in the secondary-side wiring path 8 of the branch breaker 3C. In this example, the breaking current of the branch breaker 3C is set to 20A. And as for the secondary side wiring path 8 of the branch breaker 3C, the thing whose allowable current is about 20A is used.
As illustrated in FIG. 4, when an accident such as damage to the coating occurs at a location indicated by “x” on the secondary side of the branch breaker 3 </ b> C in the middle of the wiring path 8 to which the nightlight 6 </ b> B is connected, Can flow through the wiring path 8. In the example shown in FIG. 4, since the output current of the power supply unit 7 is zero and the current supplied to the sprinkler 6A is also zero, for example, when a current of 20A flows toward the nightlight 6B, the same applies to the branch breaker 3C. 20A flows. As a result, the branch breaker 3C is subsequently cut off and no current flows through the secondary side wiring path 8 of the branch breaker 3C. That is, when the branch breaker 3C is normally cut off, an overcurrent exceeding the allowable current (for example, 20A) of the wiring path 8 is prevented from flowing toward the night light 6B where the accident has occurred.

  FIG. 5 shows an example when the output current of the power supply unit 7 is 12A. Since the branch breaker 3C does not shut off when a current of at least 20A flows, the sum 32A of 20A flowing through the branch breaker 3C and 12A output from the power supply unit 7 is the wiring of the night light 6B where the accident occurred. There is a possibility of flowing to the road 8. That is, in an electrical installation in which a plurality of electrical devices E including at least one power supply unit 7 are connected to the secondary side wiring path 8 of the branch breaker 3C, the current output from the power supply unit 7 Depending on the size, there is a problem that even if there is no problem in the operation of the branch breaker 3C, an overcurrent exceeding the allowable current (for example, 20 A) may flow through the secondary side wiring path 8 of the branch breaker 3C.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an overcurrent prevention device and a power supply capable of preventing an overcurrent from flowing through a secondary-side wiring path of a breaker to which a power supply unit is connected. The point is to provide a device.

The characteristic configuration of the overcurrent prevention device according to the present invention for achieving the above object includes a current detection unit for detecting a current flowing through a breaker having a power supply unit connected to the secondary side,
A current control unit that performs a current limiting process for reducing the output current of the power supply unit as the detected current flowing through the breaker detected by the current detection unit increases.

According to the above characteristic configuration, the current control unit performs the current limiting process for reducing the output current of the power supply unit as the current flowing through the breaker detected by the current detection unit (that is, the detection current) increases. That is, the sum of the detection current flowing through the breaker and the output current of the power supply unit can flow through the secondary side of the breaker, but as the detection current flowing through the breaker increases, the current limiting process causes By reducing the output current, an increase in current flowing through the secondary-side wiring path of the breaker is suppressed. As a result, even when a current is output from the power supply unit, it is possible to prevent an overcurrent from flowing through the secondary-side wiring path of the breaker.
Even if no current is output from the power supply, even if a large current can flow to the breaker, if the breaker operates normally in response to the large current, the wiring on the secondary side of the breaker It is possible to prevent an overcurrent from flowing through the road.
Therefore, it is possible to provide an overcurrent prevention device that can prevent an overcurrent from flowing through the secondary side wiring path of the breaker to which the power supply unit is connected.

  Another characteristic configuration of the overcurrent prevention device according to the present invention is that the current control unit stops the output of the power supply unit when the detected current is larger than a predetermined first reference current in the current limiting process. is there.

  According to the above characteristic configuration, the current control unit stops the output of the power supply unit when the detection current detected by the current detection unit is larger than the first reference current. That is, when the output of the power supply unit is stopped, the current flowing through the secondary side wiring path of the breaker is only the detection current detected by the current detection unit, that is, the current flowing through the breaker. As a result, when the detected current detected by the current detection unit exceeds the breaking current at which the breaker is cut off, the breaker is turned off, so that overcurrent can be prevented from flowing through the secondary side of the breaker. .

  Still another characteristic configuration of the overcurrent prevention device according to the present invention is that the first reference current is a value obtained by subtracting the output current of the power supply unit from the breaking current of the breaker or an equivalent amount thereof. is there.

  According to the above characteristic configuration, the first reference current is set to a smaller value as the output current of the power supply unit is larger. Then, if the detected current flowing through the breaker is larger than the first reference current set to the small value, the current control unit stops the output of the power supply unit.

  Still another characteristic configuration of the overcurrent prevention device according to the present invention is that the current control unit is configured such that, in the current limiting process, the detected current is larger than a predetermined second reference current smaller than the first reference current, and When the detected current is less than or equal to the first reference current, the output current of the power supply unit is obtained by subtracting a predetermined margin current from the breaking current of the breaker or its equivalent and subtracting the detected current It is in the point to make it an electric current.

  According to the above characteristic configuration, the current control unit causes the output current of the power supply unit to be the current at the time of suppression when the detection current detected by the current detection unit is greater than the second reference current and equal to or less than the first reference current. Since the current at the time of suppression is a value obtained by subtracting a predetermined margin current from the breaking current of the breaker or its equivalent and subtracting the detection current, the output current of the power supply unit cannot be the current at the time of suppression. For example, the magnitude of the current flowing through the secondary-side wiring path of the breaker, that is, the sum of the output current of the power supply unit (current during suppression) and the current flowing through the breaker (detection current) is a predetermined amount up to the breaking current of the breaker. There is a margin for the surplus current. Therefore, it is possible to prevent an overcurrent from flowing through the secondary side wiring path of the breaker.

  Still another characteristic configuration of the overcurrent prevention device according to the present invention is that the second reference current is obtained by subtracting an output current of the power supply unit from the breaking current of the breaker or an equivalent amount thereof, and calculating the margin current. The value is obtained by subtraction.

  According to the above characteristic configuration, the first reference current and the second reference current are set to smaller values as the output current of the power supply unit is larger. As a result, the output current of the power supply unit is controlled to be suppressed as the output current of the power supply unit increases.

  A characteristic configuration of the power supply device according to the present invention is that the overcurrent prevention device and the power supply unit are provided.

  According to the above characteristic configuration, it is possible to provide a power supply device that can prevent an overcurrent from flowing in the wiring path on the secondary side of the breaker.

It is a figure which shows the example of the electrical equipment with which the power supply part was connected to the outdoor outlet. It is a figure which shows the installation form of an overcurrent prevention apparatus. It is a flowchart explaining the current limiting process which a current control part performs. It is a figure explaining the overcurrent which can flow into the wiring path of the secondary side of a branch breaker. It is a figure explaining the overcurrent which can flow into the wiring path of the secondary side of a branch breaker.

An overcurrent prevention device according to an embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram illustrating an example of electrical equipment in which the power supply unit 7 is connected to an outdoor outlet (electric outlet 4). As shown in the figure, in this example of electrical equipment, a plurality of main circuit breakers 2 connected to the power system 1 and a plurality of wiring paths 8 branched in parallel on the secondary side of the main circuit breaker 2 are provided in parallel when viewed from the main circuit breaker 2. Branch breaker 3 (3A-3C). Various electrical devices E are connected to the secondary sides of the branch breakers 3A to 3C. The electric device E is a power consuming device 6 that consumes power, a power supply unit 7 or the like. In FIG. 1, the electrical plug 5A (5) of the power supply unit 7 and the power consuming device are connected to the electrical outlets 4A to 4C (4) connected to the secondary side wiring paths 8 of the branch breakers 3A to 3C. 6 shows an example in which an electric plug 5B (5) of a sprinkler 6A as an example of 6 and an electric plug 5C (5) of a nightlight 6B as an example of a power consuming device 6 are respectively connected. These electrical outlets 4A to 4C are, for example, outdoor outlets installed outside the facility.

FIG. 2 is a diagram illustrating an installation form of the overcurrent prevention device.
As illustrated in FIG. 2, the overcurrent prevention device includes a current detection unit 10 that detects a current flowing through a breaker 3 connected to the secondary side of the power supply unit 7 and a detection that flows through the breaker 3 detected by the current detection unit 10. And a current control unit 11 that performs a current limiting process for reducing the output current of the power supply unit 7 as the current increases. In the present embodiment, an example will be described in which the current detection unit 10 detects a current flowing through a branch breaker 3C as the breaker 3 of the present invention. In other words, in the example of the power supply facility shown in FIG. 1, the current detection unit 10 is provided in parallel on the wiring path 8 branched on the secondary side of the main breaker 2 connected to the power system 1 as viewed from the main breaker 2. Among the plurality of branch breakers 3A to 3C, a current flowing through a specific branch breaker 3C capable of connecting a plurality of electrical devices E including at least one power supply unit 7 to the secondary side is detected. A current limiting process for reducing the output current of the power supply unit 7 is performed as the detection current flowing through the specific branch breaker 3C detected by the current detection unit 10 increases.

  The branch breaker 3 normally has a cut-off current for the cut-off operation, and operates so as to cut off the circuit when an overcurrent exceeding the cut-off current flows through the branch breaker 3 itself. For example, the breaking current of the branch breaker 3 is set to a value such as 20A. And if the electric current larger than the interruption | blocking current flows into the branch breaker 3, the branch breaker 3 will carry out interruption | blocking operation | movement. The secondary breaker 3C secondary wiring path 8 has a permissible current of about 20A, so that the breaking current of the branch breaker 3C and the permissible current of the wiring path 8 are related values. .

  The power supply unit 7 includes a power supply unit 7a realized by various devices such as a fuel cell, an engine and a generator driven by the engine, and a charge / discharge device capable of charging / discharging the power. It has a power conversion unit 7b that converts power generated in the power supply unit 7a into power of a desired voltage, frequency, and phase, and a control unit 7c that controls operations of the power supply unit 7a and the power conversion unit 7b. The control unit 7c determines a predetermined target output current and controls the operations of the power supply unit 7a and the power conversion unit 7b so that the target output current is output from the power conversion unit 7b to the electrical outlet 4. The power supply unit 7 has an electrical plug 5 connected to the power conversion unit 7b. The electrical plug 5 is connected to the electrical outlet 4 connected to the secondary side wiring path 8 of the specific branch breaker 3C. By being connected, the power supply unit 7 and the wiring path 8 are electrically connected. The output current from the power conversion unit 7b to the electric plug 5 (that is, the output current of the power supply unit 7) is adjusted by control by the control unit 7c.

  The current detection unit 10 can be realized using, for example, an instrument current transformer (current transformer). In this embodiment, the current detector 10 is provided on the secondary side of the branch breaker 3C. However, if the current flowing through the branch breaker 3C can be detected, the current detector 10 is provided on the primary side of the branch breaker 3C. Also good. The power supply unit 7, the sprinkler 6A, and the nightlight 6B are connected to the secondary-side wiring path 8 of the branch breaker 3C without passing through the other branch breaker 3. The current detection unit 10 detects the current flowing through the branch breaker 3C to which the power supply unit 7, the water sprinkler 6A, and the nightlight 6B are directly connected as described above. The detection result of the current detection unit 10 is transmitted to the current control unit 11.

  When a plurality of electrical devices E including at least one power supply unit 7 are connected to the secondary side of the branch breaker 3, as shown in FIG. 5, the flow flows from the primary side to the secondary side of the branch breaker 3C. Current (32 A) of the current (for example, 20 A) and the output current (for example, 12 A) of the power supply unit 7 may flow in the wiring line 8 on the secondary side of the branch breaker 3. That is, even if an overcurrent exceeding the allowable current of the wiring path 8 does not flow through the branch breaker 3C, an overcurrent exceeding the allowable current may flow through the secondary wiring path 8 of the branch breaker 3C. There is sex.

  The branch breaker 3C is not a dedicated breaker to which only the power supply unit 7 is connected, but is a breaker in which the power supply unit 7 and the power consuming device 6 are connected together, and the branch breaker 3C on the secondary side It can be said that such a problem may occur in the wiring path 8 because the total current of the current flowing through the branch breaker 3C and the output current of the power supply unit 7 can flow. Therefore, if it is desired to suppress the current flowing in the secondary side wiring path 8 of the branch breaker 3C to be equal to or less than the allowable current of the wiring path 8, the output current of the power supply unit 7 may be suppressed as necessary. The current limiting process shown in FIG. 3 is performed under such an idea. That is, the current control unit 11 performs a current limiting process for reducing the output current of the power supply unit 7 as the current (detection current) flowing through the specific branch breaker 3C detected by the current detection unit 10 increases.

  FIG. 3 is a flowchart for explaining the current limiting process performed by the current control unit 11. The outline of the current limiting process is as shown in Table 1 below. As shown in Table 1, a current limiting process for reducing the output current of the power supply unit 7 is performed as the current (detection current) flowing through the branch breaker 3C increases.

The contents of the current limiting process will be described in detail below.
In step # 1, the current control unit 11 determines whether or not the detection current (current flowing through the branch breaker 3C) detected by the current detection unit 10 is equal to or less than the second reference current. The second reference current is set for the purpose of suppressing the current flowing in the secondary side wiring path 8 of the branch breaker 3C to be equal to or less than the allowable current of the wiring path 8, and in order to achieve the purpose, This current is an index for determining whether or not the output current needs to be suppressed.
Then, when the detected current flowing through the branch breaker 3C is equal to or less than the second reference current (in the case of “Yes” in step # 1), the current control unit 11 proceeds to step # 2. On the other hand, when the detected current flowing through the branch breaker 3C is larger than the second reference current (in the case of “No” in step # 1), the current control unit 11 proceeds to step # 3.

  Specifically, the second reference current is a value obtained by subtracting the output current of the power supply unit 7 and subtracting a predetermined margin current from the cutoff current of the specific branch breaker 3C or its equivalent amount. The current control unit 11 can acquire information about the output current of the power supply unit 7 from the control unit 7 c of the power supply unit 7. The equivalent amount of the breaking current of the branch breaker 3C is, for example, the allowable current of the wiring path 8 connected to the secondary side of the branch breaker 3C. In other words, when the breaking current of the branch breaker 3C is set to 20A, the secondary breaker 3C secondary current wiring path 8 uses a current having an allowable current of about 20A. The allowable current of the wiring path 8 is a related value. The margin current is a value smaller than the cutoff current or its equivalent amount. For example, the breaking current of the branch breaker 3C is 20A, and the surplus current is 5A. Therefore, if the output current of the power supply unit 7 is 12A, the second reference current is 3A (= 20A-12A-5A).

  As described above, if the detected current flowing through the branch breaker 3C is equal to or smaller than the second reference current, even if the output current of the power supply unit 7 is added to the detected current, the total current (that is, the possibility of flowing through the wiring path 8). It is ensured that the current with no current significantly exceeds the allowable current of the wiring line 8. For example, when the second reference current is 3A, if the detected current flowing through the branch breaker 3C detected by the current detector 10 is 3A (that is, if the detected current is equal to or less than the second reference current), Even if the output current of the power supply unit 7 is 12 A, the current flowing in the secondary side wiring path 8 of the branch breaker 3 C is about 15 A, and may not exceed the allowable current (about 20 A) of the wiring path 8. Secured.

When the detected current flowing through the branch breaker 3C is equal to or lower than the second reference current (“Yes” in step # 1), the current control unit 11 proceeds to step # 2 and outputs the output current of the power supply unit 7 The operation is performed as it is without being suppressed. That is, the control unit 7c of the power supply unit 7 outputs the target output current determined by itself from the power conversion unit 7b to the electric outlet 4.
Thereafter, the current control unit 11 proceeds to step # 6 and waits for a predetermined period, and then returns to the beginning of the flowchart of the current limiting process.

  On the other hand, when the detected current flowing through the branch breaker 3C is larger than the second reference current (in the case of “No” in step # 1), the current control unit 11 proceeds to step # 3. For example, if the detected current detected by the current detection unit 10 is 5A and is larger than the second reference current (for example, 3A), the current control unit 11 proceeds to step # 3. In step # 3, the current control unit 11 determines whether the detected current detected by the current detection unit 10 is equal to or less than the first reference current. The first reference current is a value obtained by subtracting the output current of the power supply unit 7 from the cutoff current of the specific branch breaker 3C or its equivalent amount. For example, if the breaking current of the branch breaker 3C is 20A and the output current of the power supply unit 7 is 12A, the first reference current is 8A (= 20A-12A).

  If the current control unit 11 determines in step # 3 that the detected current is less than or equal to the first reference current, the current control unit 11 proceeds to step # 4 and controls the output current of the power supply unit 7 to a predetermined current during suppression. Let For example, if the detected current detected by the current detection unit 10 is 5A and is equal to or less than the first reference current (for example, 8A), the current control unit 11 proceeds to step # 4. And the control unit 7c of the power supply part 7 outputs the electric current at the time of suppression instruct | indicated from the current control part 11 to the direction of the electrical outlet 4 from the power conversion unit 7b as its own target output current.

This current at the time of suppression is a value obtained by subtracting a predetermined margin current from the cutoff current of the specific branch breaker 3 or its equivalent, and subtracting the detection current detected by the current detection unit 10. Therefore, if the output current of the power supply unit 7 becomes the current at the time of suppression, the magnitude of the current flowing through the secondary side wiring path 8 of the branch breaker 3C, that is, the output current of the power source unit 7 (current at the time of suppression) and the branching. The total of the current (detection current) flowing through the breaker 3C is in a state where there is a margin for a predetermined margin current until the breaking current of the branch breaker 3C. Then, the suppression current determined by the current control unit 11 is transmitted to the power supply unit 7, and the control unit 7 c of the power supply unit 7 uses the suppression current as its target output current from the power conversion unit 7 b to the electrical outlet 4. The operation of the power supply unit 7a and the power conversion unit 7b is controlled so as to output to For example, if the breaking current of the branch breaker 3C is 20A, the margin current is 5A, and the current detected by the current detection unit 10 is 5A, the current control unit 11 sets the suppression current to 10A (= 20A-5A). -5A). That is, the current control unit 11 changes the initial output current of the power supply unit 7 from, for example, 12A to 10A.
Thereafter, the current control unit 11 proceeds to step # 6.

  In contrast, if the current control unit 11 determines in step # 3 that the detected current is larger than the first reference current, the current control unit 11 proceeds to step # 5 and stops the output of the power supply unit 7. For example, if the detected current detected by the current detection unit 10 is 14A and is larger than the first reference current (for example, 8A), the current control unit 11 proceeds to step # 5 and outputs to the power supply unit 7 Command to stop. Thus, when the power supply unit 7 stops outputting, the current flowing through the secondary side wiring path 8 of the branch breaker 3C is only the detection current detected by the current detection unit 10, that is, the current flowing through the branch breaker 3C. become. As a result, when the detected current detected by the current detection unit 10 exceeds the breaking current at which the branch breaker 3C is cut off, the branch breaker 3C is cut off, so that the excess current is connected to the wiring line 8 on the secondary side of the branch breaker 3C. Current can be prevented from flowing.

Here, the method by which the power supply unit 7 stops the output can be set as appropriate. For example, the method of stopping the output of the power supply unit 7 by stopping the operation of the power supply unit 7a or the power generation device as the power supply unit 7a outputs the generated power to the electrical outlet 4 while continuing the operation. There is a technique to stop only.
Thereafter, the current control unit 11 proceeds to step # 6.

  As described above, the current control unit 11 performs the current limiting process for reducing the output current of the power supply unit 7 as the current flowing through the specific breaker 3 detected by the current detection unit 10 (that is, the detection current) increases. That is, the sum of the detection current flowing through the breaker 3 and the output current of the power supply unit 7 can flow through the secondary side wiring path 8 of the breaker 3, but the current limit increases as the detection current flowing through the breaker 3 increases. By reducing the output current of the power supply unit 7 by the processing, an increase in the current flowing through the wiring path 8 on the secondary side of the breaker 3 is suppressed. As a result, even when a current is output from the power supply unit 7, it is possible to prevent an overcurrent from flowing through the secondary side wiring path 8 of the breaker 3. In addition, even if no current is output from the power supply unit 7, even if a current can flow through the breaker 3, if the breaker 3 operates normally in response to the large current, the breaker 3 It is possible to prevent an overcurrent from flowing through the secondary wiring path 8.

  In the above description, the example in which the overcurrent prevention device includes the current detection unit 10 and the current control unit 11 has been described. However, the overcurrent prevention device (the current detection unit 10 and the current control unit 11), the power supply unit 7, You may construct | assemble a power supply device provided with.

<Another embodiment>
<1>
In the said embodiment, although the specific example was given and demonstrated about the structure of the overcurrent prevention apparatus and power supply device of this invention, the structure can be changed suitably. For example, the type and number of electrical devices E connected to the secondary side wiring path 8 of the branch breaker 3 can be changed as appropriate. Moreover, the connection example of the main breaker 2 and the branch breaker 3 is described for the purpose of illustration only, and their connection form can be changed as appropriate.
Furthermore, in the above-described embodiment, the current values have been described with specific numerical values. However, these numerical values are described for the purpose of illustration and can be appropriately changed.

<2>
The configurations disclosed in the above-described embodiments (including the other embodiments, the same applies hereinafter) can be applied in combination with the configurations disclosed in the other embodiments as long as no contradiction arises, and are disclosed in this specification. The embodiment is an exemplification, and the embodiment of the present invention is not limited to this, and can be appropriately modified without departing from the object of the present invention.

  INDUSTRIAL APPLICABILITY The overcurrent prevention device and the power supply device of the present invention can be used to prevent an overcurrent from flowing through the secondary wiring path of the breaker to which the power supply unit is connected.

1 Power System 2 Main Breaker 3 Branch Breaker 6 Power Consumption Device (Electrical Equipment)
6A sprinkler (power consumption device)
6B Nightlight (power consumption device)
7 Power supply (electric equipment)
8 Wiring path 10 Current detection unit 11 Current control unit E Electrical equipment

Claims (6)

A current detection unit for detecting a current flowing through a breaker connected to the secondary side of the power supply unit;
An overcurrent prevention apparatus comprising: a current control unit that performs a current limiting process for reducing an output current of the power supply unit as a detection current flowing through the breaker detected by the current detection unit increases.   The overcurrent prevention device according to claim 1, wherein the current control unit stops the output of the power supply unit when the detected current is larger than a predetermined first reference current in the current limiting process.   3. The overcurrent prevention device according to claim 2, wherein the first reference current is a value obtained by subtracting an output current of the power supply unit from a breaking current of the breaker or an equivalent amount thereof.   In the current limiting process, when the detected current is larger than a predetermined second reference current smaller than the first reference current and the detected current is equal to or less than the first reference current, the current control unit 4. The overcurrent prevention device according to claim 2, wherein the output current is reduced to a current at the time of suppression obtained by subtracting a predetermined margin current from the breaking current of the breaker or an equivalent amount thereof and subtracting the detection current. .   5. The overcurrent according to claim 4, wherein the second reference current is a value obtained by subtracting the output current of the power supply unit and subtracting the margin current from the breaking current of the breaker or an equivalent amount thereof. Prevention device.   A power supply apparatus provided with the overcurrent prevention apparatus as described in any one of Claims 1-5, and the said power supply part.

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