WO2019244292A1

WO2019244292A1 - Electronic circuit breaker

Info

Publication number: WO2019244292A1
Application number: PCT/JP2018/023544
Authority: WO
Inventors: 雄介瀧川; 野村　敏光; 幸樹原田; 聖崇近井
Original assignee: 三菱電機株式会社
Priority date: 2018-06-21
Filing date: 2018-06-21
Publication date: 2019-12-26
Also published as: CN112352363A; WO2019244467A1; JPWO2019244467A1; JP6930664B2; CN112352363B

Abstract

This electronic circuit breaker is provided with: a current transformer 3 for detecting current flowing through an AC electric path 1; a rectifier circuit 4 connected to the secondary side of the current transformer 3 and rectifying the detected current; a power supply circuit 5 connected to the output side of the rectifier circuit 4 and outputting a constant voltage; and a microcomputer 10 for detecting the detected current at a predetermined detection cycle, calculating an accumulated current value which is obtained by accumulating the product of the square value of the effective value of the detected current in a period during which the detected current exceeds a predetermined value corresponding to a rated current and the detection cycle, and opening a switching contact 2 on the basis of the accumulated current value. The electronic circuit breaker has an OFF-time measuring circuit 20 connected to the microcomputer 10 and measuring an OFF-time that is time during which the output voltage of the power supply circuit 5 has been less than the operable voltage of the microcomputer 10. The microcomputer 10 determines the initial value of the accumulated current value on the basis of the OFF-time read from the OFF-time measuring circuit 20 during startup, the ON-current corresponding to energization current in an intermittent load, and the ON-time corresponding to energization time in the intermittent load.

Description

Electronic circuit breaker

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic circuit breaker that performs a trip operation by calculating a trip operation time according to a current level flowing in an AC electric circuit by a microcomputer.

A conventional electronic circuit breaker includes a current detecting and converting means for detecting a fault current flowing in an electric circuit and converting it into a digital signal, a level determining means comprising a micro computer for determining the level of the digital signal, and a level determining means. A time generating means comprising a microcomputer which performs a predetermined time operation corresponding to the set level, an output means which responds to the time operation of the time generating means, and a heat energy generated by an accident current during the time operation of the time generating means. Generating means comprising a microcomputer for generating a pulse having a pulse width at predetermined intervals during the timed operation, a capacitor charged by the pulse, and discharging the charge stored in the capacitor in the form of a CR time constant circuit. And a reset resistor after resetting the microcomputer. During relapse start time or fault current and a, a charging and discharging circuit means for inputting to the microcomputer as an initial value for generating timed calculation timed generating means residual voltage of the capacitor.

JP-A-60-13617

In a conventional electronic circuit breaker, since the resistance value of the discharge resistor of the charging / discharging circuit means is a single value, the off time as a load current is long in the electric circuit (for example, 1 second flows and 12 seconds do not flow). Assuming a large overcurrent and increasing the resistance value of the discharging resistor, if an intermittent overcurrent with a short OFF time (for example, 0.5 seconds flows but not 0.5 seconds) flows, the capacitor is charged. Since the voltage cannot be completely discharged and the charging voltage continues to be added, there is a problem that a current value lower than the operation characteristic may malfunction as an overcurrent.
Conversely, assuming an overcurrent with a short OFF time and reducing the resistance value of the discharging resistor, if an overcurrent with a long OFF time flows, the charging voltage of the capacitor becomes 0 due to discharging during the OFF time. As a result, heat energy could not be stored, and there was a possibility that the device would not operate.

An object of the present invention is to provide an electronic circuit breaker in which a tripping characteristic is processed by a microcomputer, and to obtain an accurate tripping characteristic in consideration of the heat storage and heat radiation characteristics of an electric circuit even for intermittent load currents with various ON / OFF cycles. To provide an electronic circuit breaker.

An electronic circuit breaker according to the present invention is connected to a switching contact inserted in an AC circuit, a current transformer for detecting a current flowing in the AC circuit, and a secondary side of the current transformer, and rectifies the detected current. A rectifier circuit, a power supply circuit connected to an output side of the rectifier circuit and outputting a constant voltage, and a detection circuit that detects a detection current at a predetermined detection cycle and detects the detection current during a period when the detection current exceeds a predetermined value corresponding to the rated current. A control device for calculating an accumulated current value obtained by integrating and accumulating the current product of the square value of the effective value of the current and the detection cycle, and for opening and closing the switching contact based on the accumulated current value; And an OFF time measuring circuit for measuring an OFF time, which is a time during which the output voltage of the power supply circuit has become lower than the operable voltage of the control device, and the control device reads from the OFF time measuring circuit at startup. OFF time, off Based on the ON time corresponding to the conduction time in the ON current and intermittent loads which corresponds to the conduction current in the load is to determine the initial value of the cumulative current value.

According to the electronic circuit breaker according to the present invention, since the OFF time measuring circuit for measuring the OFF time during which the control device is inoperable is provided, an accurate tripping operation can be performed. It becomes possible.
Other objects, features, aspects and effects of the present invention will become more apparent from the following detailed description of the present invention which refers to the accompanying drawings.

FIG. 2 is a block diagram illustrating an electronic circuit breaker according to Embodiment 1 of the present invention. FIG. 5 is an explanatory diagram for describing a method of obtaining an effective value of a current by sampling of the electronic circuit breaker according to the first embodiment. 5 is a flowchart showing processing of the microcomputer according to the first embodiment. 4 is a flowchart of an overcurrent detection process shown in FIG. FIG. 4 is a block diagram showing an electronic circuit breaker according to Embodiment 2 of the present invention. 9 is a flowchart showing processing of the microcomputer according to the second embodiment. 7 is a flowchart of an overcurrent detection process shown in FIG. FIG. 9 is a block diagram showing an electronic circuit breaker according to Embodiment 3 of the present invention. 13 is a flowchart showing processing of the microcomputer according to the third embodiment. It is a flowchart of the overcurrent detection processing shown in FIG.

Hereinafter, embodiments of an electronic circuit breaker according to the present invention will be described with reference to the drawings. In each drawing, the same reference numerals indicate the same or corresponding parts.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing an electronic circuit breaker according to Embodiment 1 of the present invention, FIG. 2 is an explanatory diagram for explaining a method of obtaining an effective value of a current by sampling, and FIG. FIG. 4 is a flowchart showing details of the overcurrent detection processing shown in FIG.

As shown in FIG. 1, an electronic circuit breaker 100 according to the present embodiment includes a switching contact 2 inserted into an AC circuit 1 to open and close the AC circuit 1, and a load provided on the AC circuit 1 and flowing through the AC circuit 1. A current transformer 3 for outputting a detection current proportional to the current, a rectifier circuit 4 connected to the secondary side of the current transformer 3 for rectifying the detection current, and an electronic type using the current output from the rectifier circuit 4 A power supply circuit 5 for outputting a constant voltage used for the operation inside the circuit breaker; a waveform conversion circuit 6 connected to the output side of the rectifier circuit 4 for converting a detection current of the current transformer 3 into an analog voltage signal; A microcomputer 10 (hereinafter, referred to as a microcomputer 10) as a control device for performing a trip characteristic process based on an analog voltage signal of the waveform conversion circuit 6, and a trip device 8 driven by each trip signal from the microcomputer 10. A trip circuit 7 for opening the closed contact 2 and an OFF time for measuring a time during which the microcomputer 10 is not operating due to a decrease in load current flowing through the AC circuit 1 and a decrease in the output voltage of the power circuit 5. It comprises a measuring circuit 20 and a thermal energy storage circuit 30 that simulates thermal energy stored in the electric wire by a load current.

The microcomputer 10 includes a first A / D converter 11a for converting an analog voltage signal of the waveform conversion circuit 6 into a digital signal, and a current of the current flowing through the AC circuit 1 based on the digital signal output from the first A / D converter 11a. An effective value calculating section 12 for calculating an effective value; a time characteristic calculating section 13 for processing a time characteristic based on the effective value of the current calculated by the effective value calculating section 12 and opening the switching contact 2 when an overcurrent occurs; And a second output A for converting the trip output port 14 for driving the trip circuit 7 and the capacitor voltage V _TIME of the OFF time measuring circuit 20 to a digital signal based on the output of the trip signal from the time characteristic calculation unit 13. / D converter 11 b, a time measurement output port 15 for outputting a voltage to charge the time measurement capacitor 21 of the OFF time measurement circuit 20, and a heat energy storage circuit 30. A / D converter 11c for converting the capacitor voltage _VTM into a digital signal, a charging output port 16 for outputting power to charge the thermal energy storage capacitor 31 of the thermal energy storage circuit 30, An output port 17 for instantaneous discharge for outputting an instantaneous complete discharge of the capacitor 31 for storing heat energy, an output port 18 for outputting an output for discharging the capacitor 31 for storing heat energy to a predetermined voltage, It is composed of

The OFF time measurement circuit 20 has one end connected to the second A / D converter 11b and the other end connected to the ground, a cathode connected to one end of the time measurement capacitor 21, and a cathode connected to the anode. Are connected to a time measurement output port 15 via a resistor 22, and a discharge resistor 24 is connected at one end to one end of the time measurement capacitor 21 and the other end is connected to the ground. I have.

The thermal energy storage circuit 30 has one end connected to the third A / D converter 11c and the other end connected to the ground, and a cathode connected to one end of the thermal energy storage capacitor 31. A diode 33 having an anode connected to the charging output port 16 via the resistor 32, a collector connected to one end of the thermal energy storage capacitor 31, and a base connected to the immediate discharging output port 17 via the resistor 34. A transistor 35 having an emitter connected to ground, a resistor 36 having one end connected to the base of the transistor 35 and the other end connected to ground, and a resistor having one end connected to one end of the capacitor 31 for storing heat energy. 37, the collector is connected to the other end of the resistor 37, and the base is connected to the discharge output port 18 via the resistor 38. Is connected, a transistor 39 whose emitter is connected to ground, one end connected to the base of transistor 39, a resistor 310 whose other end is connected to ground, and a.

Next, the processing of the effective value calculation unit 12 and the time characteristic calculation unit 13 in the microcomputer 10 will be described.
First, the calculation method of the load current in the time characteristic calculator 13 will be described with reference to FIG. The detection current of the AC circuit 1 detected by the current transformer 3 is converted into an analog voltage signal based on the detection current by the waveform conversion circuit 6, and then converted from the analog voltage signal to a digital value by the first A / D converter 11a. Is converted. The detection cycle of this detection current, that is, the sampling cycle is Δt. Since it is necessary to obtain the effective value of the load current flowing through the AC circuit 1, the AC power supply frequency of the AC circuit 1 is sampled for 100 msec, which is equivalent to 5 cycles at 50 Hz and 6 cycles at 60 Hz. square moving average of the digital values, _{^{i.e., I 1 2 = (Σi 2}} ) which is calculated by dividing the square of the accumulated sampling number m of digital values Request ^/ m. I ₁ ² square root becomes the effective value _{I 1} of the load current.

Next, the processing of the time characteristic calculator 13 will be described with reference to FIGS.
As shown in FIG. 3, when the microcomputer 10 is started by the power supply from the power supply circuit 5, first, in step S101, initial settings of the microcomputer 10 such as a clock and an output port are performed, and the process proceeds to step S102. In step S102, the capacitor voltage V _TIME of the time measuring capacitor 21 is converted into a digital signal by the second A / D converter 11b, and the process proceeds to step S103.
In step S103, using the following equation (1), the load current is calculated OFF time _{t 2} in the period of the OFF, the process proceeds to step S104. Here, tau are pointing time constant determined by the capacitance value of the discharge resistor 24 and the time measurement capacitor 21, the maximum voltage value V ₁ was charged to the time measurement capacitor 21 (eg, 3.3V) .

In step S104, the capacitor voltage _{V TM} of the thermal energy storage capacitor 31 is converted into a digital signal _V TM AD by the third A / D converter 11c, the process proceeds to step S105. In step S105, the previous, the provisional cumulative current value LTD ₁ the load current corresponds to the thermal energy accumulated in the wire to supply power to the load during the period of ON is calculated by the equation (2), the flow proceeds to step S106.
LTD ₁ = trip threshold × V _TM AD / V _MAX AD (2)
Here, V _MAX AD is a digital value after A / D conversion corresponding to the maximum voltage value charged in the time measuring capacitor 21.

In step S106, it obtains the ON time _{t 1} of the previous cycle by the equation (3) from the effective value _{I 1} of the provisional cumulative current value LTD _1, and ON current calculated so far, the flow proceeds to step S107.
t ₁ = LTD ₁ / I ₁ ² (3)
In step S107, the effective value _{I 1} as so far ON time calculated _t 1, OFF time _t 2, ON current, the thermal equivalent current Ie determined by equation (4), the flow proceeds to step S107.

In step S108, it is determined whether or not the thermal equivalent current Ie is equal to or more than a predetermined threshold (for example, a rated current set value I ₀ ). , The process proceeds to step S110.
In step S109, it sets the provisional cumulative current value LTD ₁ to cumulative current value LTD with the time characteristics calculating unit 13, in step S110, after setting the accumulated current value LTD zero, the process proceeds to step S111.

In step S111, the time measurement output port 15 of the microcomputer 10 keeps outputting the output signal S0 at the H level while the overcurrent or the normal current flows in the AC circuit 1, and keeps the time measurement capacitor 21 at the maximum level. Is charged, and the process proceeds to the overcurrent detection process in step S200.

Overcurrent detection process is a loop process of the constant cycle, as shown in FIG. 4, in step S201, the effective value I ₁ of the secondary output current of the current transformer which is obtained by the effective value calculating section 12 as the ON current whether in the overcurrent state, i.e., it determines the effective value I ₁ is whether the rated current set value I ₀ or more. If the effective value _{I 1} is equal to or greater than the rated current set value _{I 0,} the process proceeds to step S202, if the effective value _{I 1} is less than the rated current set value _{I 0,} the process proceeds to step S203. Here, the rated current set value I _0, a predetermined value in claims.

In step S202, the effective value _{I 1} is a more rated current set value _{I 0,} according to the equation (5), performs addition processing of the accumulated current value LTD, the process proceeds to step S204.
LTD = Last LTD + (Δt × I ₁ ² ) (5)
In step S203, the effective value _{I 1} is less than the rated current set value _{I 0,} according to the equation (6), the subtraction processing of the accumulated current value LTD, the process proceeds to step S204.
LTD = Last time LTD−Δt × (I ₀ ² −I ₁ ² ) (6)
Note that Δt is the conversion period of the first A / D converter 11a, but is usually a fixed value, so that it may be processed as Δt = 1 to simplify the calculation.

In step S204, the scheduled charge value _Vref of the thermal energy storage capacitor 31 is calculated from the accumulated current value LTD obtained in step S202 or step S203 according to equation (7), and the process proceeds to step S205.
V _ref = V _MAX AD × LTD / trip threshold (7)
In step S205, the digital signal _V TM AD the capacitor voltage _{V TM} of the thermal energy storage capacitor 31 and converted by a third A / D conversion 11c is determined whether charging predetermined value _{V ref} or more. If the digital signal _V TM AD is not less than the planned charging value _{V ref,} the process proceeds to step S206, if the digital signal _V TM AD is less than the scheduled charging value _{V ref,} the process proceeds to step S207.

In step S206, since the digital signal _V TM AD such or planned charging value _{V ref,} by controlling the output signal S1 of the charging output port 16 at a given time H level, the thermal energy store through a resistor 32 and a diode 33 The capacitor 31 is charged to the scheduled charge value _Vref , and the process proceeds to step S208.
On the other hand, in step S207, since the digital signal _V TM AD is less than the planned charging value _{V ref,} the output signal S3 of the discharge output port 18 to control the predetermined time H level, the collector of the transistor 39 through the resistor 38 -Conducting between the emitters and discharging the thermal energy storage capacitor 31 to the expected charge value _Vref via the resistor 37, and the process proceeds to step S208.

In step S208, it is determined whether the accumulated current value LTD is equal to or greater than a trip threshold. If the accumulated current value LTD is equal to or greater than the trip threshold, the process proceeds to step S209. If the accumulated current value LTD is less than the trip threshold, the process returns to step S201 to perform the processes in step S201 and subsequent steps again.
In step S209, the output signal S2 of the immediate discharge output port 17 is controlled to the H level, and the collector and the emitter of the transistor 35 are made conductive through the resistor 34, thereby rapidly discharging the thermal energy storage capacitor 31. The process proceeds to step S210.

In step S210, by setting the voltage signal S4 of the trip output port 14 to the H level, the trip circuit 7 is driven and the trip device 8 is operated, so that the switching contact 2 is opened and the AC circuit 1 is opened.

When the intermittent load becomes an OFF cycle and the drive power supply of the microcomputer 10 is lost, the charging voltage of the time measuring capacitor 21 is gradually discharged with the time constant determined by the discharging resistor 24 connected in parallel with the capacitance value. Will be done. On the other hand, since the discharging resistor 37 connected to the heat energy storage capacitor 31 is connected to the transistor 39 and has no other discharging path, the leakage current of the heat energy storage capacitor 31 itself and the transistor 35, Since the discharge is performed very slowly in accordance with only the leakage current of 39, the heat storage energy of the electric wire to the load can be held for a long time.

In the present embodiment, an example of a circuit using the time measuring capacitor 21 and the discharging resistor 24 for discharging is shown as the OFF time measuring circuit 20, but power is supplied from a battery or a super capacitor or the like. A clock IC (Integrated @ Circuit) may be used.

According to the present embodiment, the switching contact 2 inserted into the AC circuit 1, the current transformer 3 for detecting the current flowing in the AC circuit 1, and the secondary side of the current transformer 3 are connected to A rectifier circuit 4 for rectifying, a power supply circuit 5 connected to an output side of the rectifier circuit 4 and outputting a constant voltage, and detecting a detected current at a predetermined detection cycle, and detecting the detected current at a predetermined value corresponding to the rated current. A microcomputer 10 for calculating an accumulated current value obtained by integrating and accumulating the current product of the square value of the effective value of the detected current and the detection period during the period of time exceeded, and for opening and closing the switching contact 2 based on the accumulated current value; The microcomputer 10 has an OFF time measuring circuit 20 for measuring an OFF time that is a time during which the output voltage of the power supply circuit 5 has become lower than the operable voltage of the microcomputer 10. OFF time read from _2, because it determines the initial value of the cumulative current value based on the ON time t ₁ corresponding to the energizing time of the ON current I _ON and intermittent loads which corresponds to the conduction current in the intermittent load, can be performed to correct tripping operation It becomes.

Also, a thermal energy storage capacitor 31 charged by the microcomputer 10 to a voltage corresponding to the accumulated current value, and a thermal energy storage circuit 30 connected to the microcomputer 10 so that the charge voltage of the thermal energy storage capacitor 31 can be read by the microcomputer 10 are included. includes, oN current I _oN is using the effective value I ₁ of the detected current from the current transformer 3 which is calculated at the start of the microcomputer 10, oN time t ₁ is at the start of the charging voltage and the microcomputer 10 of the thermal energy storage circuit 30 since calculated from the effective value I ₁ of the detected current from the calculated current transformer 3, it is possible to perform and accurate tripping operation.

The cumulative current value LTD calculated by the microcomputer 10 is obtained by accumulating the square value of the effective value of the detected current during a period in which the microcomputer 10 exceeds a predetermined value.

In addition, during the tripping operation, the energy of the thermal energy storage capacitor 31 is instantaneously discharged by setting the output signal S2 of the instantaneous discharge output port 17 to the H level. Without this, continuous power supply becomes possible.

Embodiment 2 FIG.
Next, an electronic circuit breaker 200 according to Embodiment 2 of the present invention will be described.
FIG. 5 is a block diagram of the electronic circuit breaker according to the second embodiment, FIG. 6 is a flowchart showing processing of the microcomputer, and FIG. 7 is a flowchart showing details of the overcurrent detection processing shown in FIG.
The difference between the first embodiment and the present embodiment is that, as shown in FIG. 5, a non-volatile memory 40 is provided in place of the thermal energy storage circuit 30 and the microcomputer 10 is used to acquire the data of the non-volatile memory 40 by communication. In some cases, a communication unit 19 is provided inside. Here, as the nonvolatile memory 40, use of a ferroelectric memory (Ferroelectric Random Access Memory), a resistance change type memory (Resistive Random Access Memory), or the like is assumed.

In the first embodiment, the third A / D converter 11c, the charging output port 16, the immediate discharging output port 17, and the discharging output port 18 provided inside the microcomputer 10 are eliminated. . Other configurations are the same as those in the first embodiment, and thus detailed description is omitted.
In the electronic circuit breaker 200 according to the present embodiment, the accumulated current value LTD and the ON time counter are always written in the non-volatile memory 40, and when the microcomputer 10 is restarted in an intermittent load environment, the time characteristic is not changed. The calculation unit 13 reads out the accumulated current value LTD and the ON time counter from the nonvolatile memory 40 via the communication unit 19, and performs processing.

To perform the calculation of the thermal equivalent current I _e with the electronic circuit breaker 100 according to the first embodiment, the effective value I ₁ of the secondary output current of the current transformer 3 in the current cycle as the ON current, intermittent load Is assumed to be always constant within the period. Therefore, when the current value of the intermittent load greatly differs depending on the cycle, it is impossible to accurately calculate the thermal equivalent current _Ie .
For example, an intermittent load having an effective value of current I ₁ = 100 A when the current cycle was ON, an effective value I ₁ ′ = 80 A of current when the current cycle is ON, ON time t ₁ = 1 sec, and OFF time t ₂ = 3 sec. Suppose. In the first embodiment, since the effective value I ₁ ′ = 80 A of the current immediately after the microcomputer 10 is restarted is used to calculate the thermal equivalent current _Ie using the equation (4), the thermal equivalent current _Ie is calculated. _e is calculated by the following equation (8) and becomes 40A.

On the other hand, when the calculation is performed using the effective value I ₁ = 100 A of the current at the time of the ON of the previous previous cycle, the thermal equivalent current _Ie is 50 A and does not match, so that it does not exceed the predetermined threshold. There is a possibility that the erroneous processing is performed, and the charging voltage of the thermal energy storage capacitor 31 is not reflected on the accumulated current value LTD and becomes inoperable.

Next, the processing of the time characteristic calculation unit 13 in the electronic circuit breaker 200 will be described with reference to FIGS.
As shown in FIG. 6, when the microcomputer 10 is started up by the power supply from the power supply circuit 5, the processing is first started from step S301, but steps S301 to S303 are the same as steps S101 to S103 shown in FIG. Description of the processing is omitted.
In step S304, the nonvolatile memory 40, reads out the accumulated electric current value LTD recorded when there is a previous power as a provisional cumulative current value LTD _1, after reading the value of the ON time counter as the ON time _{t 1,} step S305 Proceed to.

In step S305, using the provisional cumulative current value LTD ₁ and ON time _{t 1} is read out from the non-volatile memory 40, and calculates the ON current _{I ON} by equation (9), the flow proceeds to step S306.
I _ON = √ (LTD ₁ / t ₁ ) (9)
In step S306, ON current _{I ON} calculated in step S305, OFF time _{t 2} read in step S303, and ON from the time _{t 1} read out in step S304, the thermal equivalent current _{I e} by using the equation (10) The calculation is performed, and the process proceeds to step S307.

Steps S307 to S310 have the same processing contents as steps S108 to S111 shown in FIG. In step S310, after performing the same processing as step S111, the process proceeds to the overcurrent detection processing in step S400.

Overcurrent detection process is a loop process of the constant cycle, as shown in FIG. 7, in step S401, the effective value I ₁ of the secondary output current of the current transformer 3 which is obtained by the effective value computing unit 12 is overcurrent whether the state, i.e., determines the effective value I ₁ is whether the rated current set value I ₀ or more. If the effective value _{I 1} is equal to or greater than the rated current set value _{I 0,} the process proceeds to step S402, if the effective value _{I 1} is less than the rated current set value _{I 0,} the process proceeds to step S403. Here the rated current set value I ₀ at is the predetermined value in claims.

In step S402, the same process as step S202 shown in FIG. 3 is performed, and the process proceeds to step S404.
In step S403, the same process as in step S203 shown in FIG. 3 is performed, and the process proceeds to step S405.
In step S404, an ON time counter is added, and the process proceeds to step S406. When the overcurrent detection process is a fixed-cycle loop process performed every 1.25 msec, for example, the addition process of the ON time counter can be a process of simply adding the counter value by one. If the overcurrent detection process is not a fixed-cycle loop process, it is necessary to add a value proportional to the elapsed time from the previous process.

In step S405, a subtraction process of the ON time counter is performed, and the flow advances to step S406. When the overcurrent detection process is a fixed-cycle loop process performed every 1.25 msec, for example, the subtraction process of the ON time counter can be a process of simply subtracting one from the counter value. If the overcurrent detection process is not a fixed-cycle loop process, it is necessary to perform a process of subtracting a value proportional to the elapsed time from the previous process.

In step S406, the accumulated current value LTD calculated in step S402 or step S403 immediately before coming to step S406, similarly ON time counter value as the ON time _{t 1} calculated in step S404 or step S405 immediately before coming to step S406 Is written to the non-volatile memory 40, and the process proceeds to step S407.

In step S407, it is determined whether the accumulated current value LTD calculated in step S402 or step S403 is equal to or greater than a trip threshold immediately before step S407. If the accumulated current value LTD is equal to or larger than the trip threshold, the process proceeds to step S408, and if the accumulated current value LTD is smaller than the trip threshold, the process returns to step S401, and the process of step S401 is performed at regular intervals.

In step S408, a process of writing “0” as the value of the accumulated current value LTD of the nonvolatile memory 40 and the value of the ON time counter is performed, and the process proceeds to step S409.
In step S409, as in step S210, the tripping circuit 7 is driven by operating the tripping circuit 8 by setting the voltage signal S4 of the tripping output port 14 to the H level, thereby opening the on-off contact 2 to disconnect the AC circuit. Release 1.

In the example of the present embodiment, the process of writing the accumulated current value LTD and the value of the ON time counter to the non-volatile memory 40 is performed every time in step S406 of the overcurrent detection process. If the number of times of writing is limited, the process may proceed to step S408, that is, write to the non-volatile memory 40 before the on / off contact 2 is tripped.

According to the present embodiment, the switching contact 2 inserted into the AC circuit 1, the current transformer 3 for detecting the current flowing in the AC circuit 1, and the secondary side of the current transformer 3 are connected to A rectifier circuit 4 for rectifying, a power supply circuit 5 connected to an output side of the rectifier circuit 4 and outputting a constant voltage, and detecting a detected current at a predetermined detection cycle, and detecting the detected current at a predetermined value corresponding to the rated current. A microcomputer 10 for calculating an accumulated current value obtained by integrating and accumulating the current product of the square value of the effective value of the detected current and the detection period during the period of time exceeded, and for opening and closing the switching contact 2 based on the accumulated current value; The microcomputer 10 has an OFF time measuring circuit 20 for measuring an OFF time that is a time during which the output voltage of the power supply circuit 5 has become lower than the operable voltage of the microcomputer 10. OFF time read from _2, because it determines the initial value of the cumulative current value LTD based on the ON time t ₁ corresponding to the energizing time of the ON current I _ON and intermittent loads which corresponds to the conduction current in the intermittent load, be carried out by accurate tripping operation It becomes possible.

The microcomputer 10 further includes a non-volatile memory 40 connected to the microcomputer 10. When the effective value of the detected current is equal to or more than a predetermined value corresponding to the rated current, the microcomputer 10 adds the effective value, and the effective value of the detected current is less than the predetermined value. case calculates the oN time _{t 1} by subtracting reads and writes to the accumulated current value LTD and oN time nonvolatile memory 40 to _{t 1,} at the time of startup of the microcomputer 10, the oN time _{t 1} from the non-volatile memory 40 , ON current _ION is calculated from the accumulated current value LTD read from the non-volatile memory 40 and the ON time t ₁ read from the non-volatile memory, so that accurate ON time t ₁ and ON current _ION can be obtained. Become.

Embodiment 3 FIG.
FIG. 8 is a block diagram showing an electronic circuit breaker according to Embodiment 3 of the present invention, FIG. 9 is a flowchart showing processing of a microcomputer, and FIG. 10 is a flowchart of overcurrent detection processing shown in FIG.
In the second embodiment, an example in which the accumulated current value LTD and the value of the ON time counter are written to the nonvolatile memory has been described. However, in the present embodiment, only the value of the ON time counter is written to the nonvolatile memory, current is to use the effective value I ₁ of the secondary output current of the current transformer which is obtained by the effective value computing unit 12. Therefore, FIG. 8 showing the configuration of the electronic circuit breaker 300 of the present embodiment is the same as FIG. 5 described in the second embodiment, and a description thereof will be omitted.

The processing of the time characteristic calculating unit 13 in the electronic circuit breaker 300 according to the present embodiment will be described with reference to FIGS.
As shown in FIG. 9, when the microcomputer 10 is started by the power supply from the power supply circuit 5, the processing is first started from step S501, but steps S501 to S503 are the same as steps S301 to S303 shown in FIG. Description of the processing is omitted.
In step S504, the nonvolatile memory 40, reads the ON time _{t 1} that is recorded when a last energized, the process proceeds to step S505.

In step S505, it calculates an effective value _{I 1} as ON current than the detection current of the current transformer 3, the process proceeds to step S506. In step S506, ON time _{t 1} read in step S504, from the effective value _{I 1} of the ON current calculated in OFF time _{t 2} and the step S505 obtained in step S503, the thermal equivalent current _{I e} Equation (4) And the process proceeds to step S507.

In step S507, ON time _{t 1} read in step S504, the provisional cumulative current value LTD ₁ determined by the equation (11) from the thermal equivalent current _{I e} was OFF time _{t 2} and the step S506 calculating determined in step S503, step S508 Proceed to.
LTD ₁ = I _e ² (t ₁ + t ₂ ) (11)

Steps S508 to S511 have the same processing contents as steps S307 to S310 shown in FIG. In step S511, after performing the same processing as in step S310, the process proceeds to the overcurrent detection processing in step S600.

The overcurrent detection process is a loop process of periodic, as shown in FIG. 10, in step S601, the effective value I ₁ of the secondary output current of the current transformer 3 which is obtained by the effective value computing unit 12 is overcurrent whether the state, i.e., determines the effective value I ₁ is whether the rated current set value I ₀ or more. If the effective value _{I 1} is equal to or greater than the rated current set value _{I 0,} the process proceeds to step S602, if the effective value _{I 1} is less than the rated current set value _{I 0,} the process proceeds to step S603. Here the rated current set value I ₀ at is the predetermined value in claims.

Steps S602 to S605 are the same processing contents as steps S402 to S405 shown in FIG. After performing the processing of step S604 or step S605, the process proceeds to step S606.
In step S606, performs a process of writing the ON value of the time counter calculated in step S604 or step S605 immediately before coming to step S606 as the ON time _{t 1} to the nonvolatile memory 40, the process advances to step S607.

In step S607, it is determined whether the accumulated current value LTD calculated in step S602 or step S603 is equal to or larger than the trip threshold immediately before step S607. When the accumulated current value LTD is equal to or larger than the trip threshold, the process proceeds to step S608, and when the accumulated current value LTD is smaller than the trip threshold, the process returns to step S601, and the process of step S601 is performed at regular intervals.

At step S608, the performs processing to write "0" as the value of the ON time _{t 1} to the nonvolatile memory 40, the process proceeds to step S609.
In step S609, as in step S409, the voltage signal S4 of the trip output port 14 is set to the H level, thereby driving the trip circuit 7 and operating the trip device 8, thereby opening the on-off contact 2 to release the AC circuit. Release 1.

In the example of the present embodiment, the process of writing the value of the ON time counter to the non-volatile memory 40 in step S606 of the overcurrent detection process is performed every time. However, the number of times of writing to the non-volatile memory to be used is limited. In some cases, when the processing proceeds to step S608, that is, before the on / off contact 2 is tripped, the data may be written to the nonvolatile memory 40.

According to the present embodiment, the switching contact 2 inserted into the AC circuit 1, the current transformer 3 for detecting the current flowing in the AC circuit 1, and the secondary side of the current transformer 3 are connected to A rectifier circuit 4 for rectifying, a power supply circuit 5 connected to an output side of the rectifier circuit 4 and outputting a constant voltage, and detecting a detected current at a predetermined detection cycle, and detecting the detected current at a predetermined value corresponding to the rated current. A microcomputer 10 for calculating an accumulated current value obtained by integrating and accumulating the current product of the square value of the effective value of the detected current and the detection period during the period of time exceeded, and for opening and closing the switching contact 2 based on the accumulated current value; The microcomputer 10 has an OFF time measuring circuit 20 for measuring an OFF time that is a time during which the output voltage of the power supply circuit 5 has become lower than the operable voltage of the microcomputer 10. OFF time read from _2, because it determines the initial value of the cumulative current value LTD based on the ON time t ₁ corresponding to the current time in the ON current and intermittent loads which corresponds to the conduction current in the intermittent load, can be performed to correct tripping operation as Become.

Further, the ON time _{t 1} in the previous cycle stored in the nonvolatile memory 40, an OFF time _{t 2} is read from the OFF time measuring circuit 20, as ON current _{I ON} calculated from the secondary output current of the current transformer 3 the effective value I _1, to calculate the thermal equivalent current I _e provisional cumulative current value LTD ₁ from, it is possible to perform with accurate tripping operation.

{Circle around (2)} Since the cumulative current value calculated by the microcomputer 10 is obtained by accumulating the square value of the effective value of the detected current during the period exceeding the predetermined value, the calculation load of the cumulative current value by the microcomputer 10 can be reduced.

2 switching contacts, 3 current transformers, 4 rectifier circuits, 5 power supply circuits, 6 waveform conversion circuits,
7 trip circuit, 8 trip device, 10 microcomputer,
20 OFF time measurement circuit, 30 thermal energy storage circuit, 40 nonvolatile memory,
100 Electronic circuit breaker.

Claims

A switching contact inserted in the AC circuit,
A current transformer for detecting a current flowing in the AC circuit,
A rectifier circuit connected to the secondary side of the current transformer and rectifying the detection current;
A power supply circuit connected to the output side of the rectifier circuit and outputting a constant voltage;
A cumulative current which is obtained by detecting the detection current at a predetermined detection cycle and accumulating a product of a square value of an effective value of the detection current and a detection cycle during a period when the detection current exceeds a predetermined value corresponding to a rated current; Calculating a value, and a control device for opening the switching contact based on the accumulated current value,
An OFF time measurement circuit connected to the control device, for measuring an OFF time that is a time when the output voltage of the power supply circuit has been less than the operable voltage of the control device,
At the time of start-up, the control device initializes the cumulative current value based on the OFF time read from the OFF time measurement circuit, an ON current corresponding to an energizing current in the intermittent load, and an ON time corresponding to an energizing time in the intermittent load. An electronic circuit breaker for determining a value.
A nonvolatile memory connected to the control device,
The control device calculates the ON time by adding when the predetermined value is equal to or more than the predetermined value and subtracting when the effective value of the detected current is less than the predetermined value, and calculates the accumulated current value and the ON time. Into the nonvolatile memory,
When the control device is started, the ON time is read from the nonvolatile memory, and the ON current is calculated from the cumulative current value read from the nonvolatile memory and the ON time read from the nonvolatile memory. The electronic circuit breaker according to claim 1, wherein
A capacitor charged to a voltage corresponding to the accumulated current value from the control device, and a heat energy storage circuit connected to the control device so that the charged voltage of the capacitor can be read by the control device,
The ON current uses an effective value of the detected current calculated at the time of starting the control device, and the ON time is an effective value of the charging current of the thermal energy storage circuit and the effective value of the detected current calculated at the time of starting the control device. The electronic circuit breaker according to claim 1, wherein the electronic circuit breaker is calculated from:
A nonvolatile memory connected to the control device,
The control device calculates the ON time by adding when the effective value of the detected current is equal to or more than the predetermined value, and subtracts when the effective value of the detected current is less than the predetermined value, and calculates the ON time by using the nonvolatile memory. While writing to
2. The electronic circuit breaker according to claim 1, wherein the ON current uses an effective value of the detection current calculated when the control device is started, and the ON time is read from the nonvolatile memory. 3.
5. The method according to claim 1, wherein the cumulative current value calculated by the control device is obtained by accumulating a square value of an effective value of the detected current during a period exceeding the predetermined value. 6. The electronic circuit breaker according to claim 1.