JPH10271660A - Overcurrent detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To select a circuit breaker with a small current rating as a circuit breaker provided in a wiring route which allows a temporary overload state for a short time. SOLUTION: An overcurrent detector has a load current detecting means such as a current transformer 4 which detects a load current applied to a wiring route 1, an overcurrent detecting means such as a microcomputer 9 which outputs a tripping signal when the detected load current reaches predetermined counter-timing characteristics, an output device 10 which opens a switching contact 2 in accordance with the tripping signal and cuts off the load current applied to the wiring route, an alarm device 17 which outputs an alarm in accordance with the tripping signal and a lock input means 19 which, by a changeover switch 18, disconnects the overcurrent detecting means from the output device 10 and connects the overcurrent detecting means to the alarm device 17 at the time of an ON-operation and, further, outputs a characteristics substitution control signal to a control switch 16. The microcomputer substitutes the predetermined counter-timing characteristics with counter-timing characteristics corresponding to a current rating larger than an original current rating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overcurrent detecting device for a circuit breaker for detecting a fault current in a circuit to protect the circuit. The present invention relates to an overcurrent detection device that enables use of a circuit breaker for a current.

[0002]

2. Description of the Related Art A conventional overcurrent detecting device will be described with reference to FIGS. 10 and 11
FIG. 1 is a diagram showing a configuration and a time limit characteristic of a conventional overcurrent detection device disclosed in, for example, JP-A-60-32513.

In FIG. 10, 1 is a wiring circuit, 2 is a switching contact, and 3 is a load connected to the wiring circuit 1. Also,
4 is a current transformer for detecting a current flowing through the load 3, 5 is a rectifier circuit provided on the secondary side of the current transformer 4, 6 is a burden circuit for converting the output of the rectifier circuit 5 into a voltage signal, and 7 is a waveform. This is a conversion circuit for obtaining an effective value of an output signal induced in the burden circuit 6.

In FIG. 1, reference numeral 8 denotes an A / D conversion circuit, which receives an analog output of the waveform conversion circuit 7 from a first input terminal 8a, converts the analog output into a digital signal, and outputs the digital signal to the microcomputer 9. This microcomputer 9
In the ROM, the time limit characteristic shown in FIG. 11 is stored in the ROM, and the time limit of the detection current is compared with the time limit value, so that the output device 10 has a time limit corresponding to the magnitude of the overcurrent exceeding the time limit characteristic. The switching contact 2 is opened via the switch to cut off the load current of the wiring circuit 1.

Further, in the figure, 9a is an output port of the microcomputer 9, 11 is a capacitor,
When the load current of the wiring circuit 1 exceeds the rated value, the charge corresponding to the pulse output from the output port 9a is accumulated through the charging resistor 12 and the backflow preventing diode 13. Reference numeral 14 denotes a discharge resistor which discharges the charge of the capacitor 11 with a predetermined time constant. The potential of the capacitor 11 is input to a second input terminal 8b of the A / D conversion circuit 8.

Next, the operation of the conventional overcurrent detecting device will be described. When the current flowing through the wiring circuit 1 is equal to or greater than the rated value, the microcomputer 9 performs time counting, and when the time count reaches a value corresponding to the current shown in the inverse time characteristic of FIG. Output disconnect signal.

Further, in a current range exceeding the rated value even before the trip signal is output, the microcomputer 9 outputs a pulse corresponding to the current value flowing through the wiring circuit 1 to charge the capacitor 11. . The residual potential of the capacitor 11 varies depending on the frequency of charging and the discharge through the discharge resistor 14.

The microcomputer 9 constantly monitors the potential of the capacitor 11 via the A / D conversion circuit 8, and uses the potential of the capacitor 11 as an initial value of the next time count. In this way, by setting the residual potential of the capacitor 11 as the initial value of the time count, the operation characteristics of the circuit breaker are determined in consideration of the heat resistance of the distribution line of the wiring circuit 1.

[0009]

Generally, a circuit breaker having a rated current for protecting a wiring is selected based on a current flowing through a wiring circuit. For this reason, select a circuit breaker with a rated current value that is considerably larger than the actual capacity of the circuit breaker in terms of the heat capacity of the actual circuit breaker for the wiring circuit to which a load that requires a large current intermittently and temporarily is connected. And it is uneconomical.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem. In a wiring circuit that allows a temporary overcurrent, a temporary circuit breaker having a small rated current can be used within a thermal allowable range. It is an object of the present invention to obtain an overcurrent detection device that can flow a large overcurrent and protect the wiring.

[0011]

According to the present invention, there is provided an overcurrent detecting apparatus, comprising: a load current detecting means for detecting a load current flowing through a wiring circuit; and the detected load current reaching a predetermined first time limit characteristic. Then, an overcurrent detection unit that outputs a trip signal, and an output device that disconnects a switching contact based on the trip signal to cut off a load current flowing through the wiring circuit,
An alarm device that outputs an alarm based on the trip signal;
A lock input for disconnecting the overcurrent detection means from the output device by a changeover switch to connect the overcurrent detection means to the alarm device and for outputting a characteristic replacement signal to the overcurrent detection means when the switch is turned on; Means, wherein the overcurrent detection means replaces the predetermined first time limit characteristic with a second time limit characteristic corresponding to a rated current larger than the original rated current based on the characteristic replacement signal. When the loaded load current reaches the replaced second time limit characteristic, a trip signal is output.

Further, an overcurrent detection device according to the present invention comprises:
The overcurrent detecting means changes the discharge time constant of the capacitor based on the characteristic replacement signal, thereby changing the predetermined first time limit characteristic to a second time limit corresponding to a rated current larger than the original rated current. It is replaced with a characteristic.

Further, the overcurrent detecting device according to the present invention comprises:
The overcurrent detection means changes the number of pulses based on the characteristic replacement signal, thereby changing the predetermined first time limit characteristic to a second current corresponding to a rated current larger than the original rated current.
When the number of pulses corresponding to the detected load current reaches the replaced second time limit characteristic, a trip signal is output.

Further, the overcurrent detecting device according to the present invention comprises:
The overcurrent detection means includes an instantaneous characteristic detection unit, a short time characteristic detection unit, and a long time characteristic detection unit, and the instantaneous characteristic detection unit and the short time characteristic detection unit are directly connected to the output device. The long time characteristic detection unit and the output device are connected via the changeover switch, and the long time characteristic of the predetermined first reverse time characteristic is larger than the original rated current based on the characteristic replacement signal. A second time limit characteristic corresponding to the current is replaced, and a trip signal is output when the detected load current reaches the replaced second time limit characteristic.

Further, in the overcurrent detecting device according to the present invention, the alarm device and the lock input means are installed near a load connected to the wiring circuit.

An overcurrent detecting device according to the present invention includes a load current detecting means for detecting a load current flowing through a wiring circuit, and outputting a trip signal when the detected load current reaches a first predetermined time limit characteristic. An overcurrent detecting means, an output device for opening a switching contact based on the tripping signal to cut off a load current flowing through the wiring circuit, and outputting a characteristic replacement signal to the overcurrent detecting means when turned on. And a lock input unit that replaces the predetermined first time limit characteristic with a second time limit characteristic corresponding to a rated current larger than the original rated current based on the characteristic replacement signal. And outputting a trip signal when the detected load current reaches the replaced second time limit characteristic.

Further, an overcurrent detection device according to the present invention
The overcurrent detecting means changes the discharge time constant of the capacitor based on the characteristic replacement signal, thereby changing the predetermined first time limit characteristic to a second time limit corresponding to a rated current larger than the original rated current. It is replaced with a characteristic.

Further, the overcurrent detecting device according to the present invention comprises:
The overcurrent detection means changes the number of pulses based on the characteristic replacement signal, thereby changing the predetermined first time limit characteristic to a second current corresponding to a rated current larger than the original rated current.
When the number of pulses corresponding to the detected load current reaches the replaced second time limit characteristic, a trip signal is output.

Further, the overcurrent detecting device according to the present invention comprises:
The overcurrent detection means includes an instantaneous characteristic detection unit, a short time characteristic detection unit, and a long time characteristic detection unit, and detects a long time characteristic among the first predetermined time characteristic based on the characteristic replacement signal. The second corresponding to the rated current larger than the original rated current
And a trip signal is output when the detected load current reaches the replaced second time limit characteristic.

Further, in the overcurrent detection device according to the present invention, the lock input means is provided near a load connected to the wiring circuit.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. First Embodiment A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a configuration of the first embodiment of the present invention. FIG. 2 is a diagram showing the time limit characteristic of the first embodiment of the present invention. In the drawings, the same reference numerals indicate the same or corresponding parts.

In FIG. 1, 1 is a wiring circuit, 2 is a switching contact, 3 is a load, 4 is a current transformer, 5 is a rectifier circuit, 6 is a burden circuit, and 7 is a waveform conversion circuit.

In FIG. 1, reference numeral 8 denotes an A / D conversion circuit, which inputs an analog output of the waveform conversion circuit 7 from a first input terminal 8a, converts the analog output into a digital signal, and outputs the digital signal to the microcomputer 9. 9a is an output port of the microcomputer 9, 11 is a capacitor, 12 is a charging resistor,
Reference numeral 13 denotes a diode for preventing backflow, reference numeral 14 denotes a discharge resistor, and the potential of the capacitor 11 is input to a second input terminal 8b of the A / D conversion circuit 8.

Further, in FIG.
Is a shunt resistor connected in parallel to 16 is a shunt resistor 15
Is a control switch for controlling whether or not to connect, a reference numeral 17 is an alarm device, and 18 is a changeover switch, which switches a trip signal output from the microcomputer 9 to either the output device 10 or the alarm device 17.

Further, in the figure, reference numeral 19 denotes a lock input means such as a voltage input relay circuit. For example, when a large current is needed temporarily, the operator operates the lock input means 19 from outside the circuit breaker to perform a lock input, turns on the control switch 16 (ON), and turns on the shunt resistance. 15 and at the same time, the changeover switch 18 is switched to the alarm device 17 side. On the other hand, when the lock input means 19 is released, the control switch 16 is turned off (O
FF), the changeover switch 18 switches to the output device 10 side.

Next, the operation of the first embodiment will be described. By the lock input operation of the lock input means 19, discharge from the shunt resistor 15 is applied, and the capacitor 11
Discharge time becomes short, and the residual potential, which is the initial value of the timed count, falls quickly. Therefore, the time count in the microcomputer 9 is extended by the potential decreasing rate.

As shown in FIG. 2, the time characteristic (hot characteristic: solid line) in the current region exceeding the rated current of the circuit breaker is changed by the time characteristic (two-dot chain line) of the circuit breaker having a larger rated current. ). However, the inherent allowable current characteristic (cold characteristic: dotted line) with respect to the rated current of the circuit breaker does not exceed the range.

Then, the changeover switch 18 is set to the alarm device 17.
Side, the microcomputer 9
When the value of the timed count in () reaches the value of the replaced timed characteristic (two-dot chain line), an alarm is issued from the alarm device 17 instead of opening the switching contact 2. This alarm device 17
Is installed in the vicinity of the operator of the load 3 remote from the circuit breaker, so that the operator receives an alarm and cuts off or reduces the load 3. Further, it is possible to install the lock input means 19 near the operator of the load 3.

As described above, by replacing the time characteristic of the circuit breaker with the time characteristic of the circuit breaker having a larger rated current by the control switch 16, the rated current of 100 to 500% of the installed circuit breaker can be reduced. Can be used within thermal tolerances. In particular, when a current exceeding the rated current is intermittently passed, the residual potential of the capacitor 11 with the shunt resistor 15 connected is selected as a discharge time constant that simulates the heat radiation characteristics of the circuit breaker. The maximum thermal tolerance can be used.

In the first embodiment, a pulse signal having a pulse width corresponding to the heat energy determined based on the magnitude and duration of the current in the wiring circuit 1 during the timed operation is generated.
A capacitor 11 charged by the pulse signal;
A discharge resistor 14 for discharging the charge of the capacitor 11 in the form of a CR time constant, and a lock input means 19 for controlling the connection of a shunt resistor 15 for reducing the CR time constant are provided. This is input to the microcomputer 9 as an initial value. further,
The overcurrent detection device according to the first embodiment includes an alarm device 1
7 and a changeover switch 18, and the lock input means 1
The changeover switch 18 is switched from the output device 10 side to the alarm device 17 side in synchronization with the connection signal of the shunt resistor 15 from the switch 9. Note that the alarm device 17 and the changeover switch 18 are not required, and the microcomputer 9 and the output device 10 may be directly connected as in the related art.

Embodiment 2 In the first embodiment, when a short circuit accident occurs in the lock input state, the alarm device 17 is activated.
Therefore, it is impossible to protect the wiring circuit 1 only by issuing an alarm. Therefore, in the second embodiment, an overcurrent detection device that improves this point will be described.

Embodiment 2 of the present invention will be described with reference to FIGS. FIG. 3 is a diagram showing a configuration of the second embodiment of the present invention. FIG. 4 is a diagram showing the time limit characteristic of the second embodiment of the present invention.

In FIG. 3, wiring circuit 1 to lock input means 19 are the same as those described in the first embodiment.
The microcomputer 9 for detecting the time limit of the electronic overcurrent detecting device of the circuit breaker includes a long time characteristic detecting section 9b for detecting up to several times the rated current and a short time characteristic for detecting up to about 20 times the rated current. It comprises a detecting section 9c and an instantaneous characteristic detecting section 9d for detecting more than that.

This is divided because the relationship between the current value and the trip time is exponential and it is difficult for a single processing circuit to cope with it. In the second embodiment, using this configuration, the long time characteristic detecting section 9 b sends an output signal to the output device 10 or the alarm device 17 via the changeover switch 18. On the other hand, the short time period characteristic detecting section 9c and the instantaneous characteristic detecting section 9d directly send output signals to the output device 10 without passing through the changeover switch 18.

As shown in FIG. 4, when the lock input by the lock input means 19 is on, the long time characteristic detecting section 9b
The time characteristic of the circuit breaker is replaced by one with a large rated current (two-dot chain line), and a large amount of current such as a short-circuit accident during use of the circuit breaker is reduced by the instantaneous characteristic detecting unit 9d and the short time characteristic detecting unit. 9c is detectable, so that when an accident current flows, the switching contact 2 is opened to cut off this accident current, thereby protecting the wiring circuit 1.

In the second embodiment, the microcomputer 9 includes an instantaneous characteristic detecting section 9d and a short time characteristic detecting section 9c.
And a long time characteristic detecting section 9b.
d and the output signal of the short time characteristic detecting section 9c are directly input to the output device 10, and the output from the long time characteristic detecting section 9b is input to the output device 10 via the changeover switch 18. . Note that the alarm device 17 and the changeover switch 18 are not required, and the microcomputer 9 and the output device 10 may be directly connected as in the related art. In this case, the long time characteristic detection unit 9b is also directly connected to the output device 10. .

Embodiment 3 Embodiment 3 of the present invention will be described with reference to FIG. FIG. 5 is a diagram showing a configuration of the third embodiment of the present invention.

In FIG. 5, wiring circuit 1 to lock input means 19 are the same as those described in the first embodiment.
Reference numeral 20 denotes a circuit breaker main body, and reference numerals 20a and 20b denote relay terminals for drawing out the signal lines 17a and 19a from the circuit breaker main body 20. Reference numeral 21 denotes a control box, in which an alarm device 17 and a lock input means 19 such as a voltage input relay circuit are integrally incorporated and installed near the load 3.

The alarm device 17 is connected to one output terminal of the changeover switch 18 via a relay terminal 20a by a signal line 17a. Also, the lock input means 19
Is connected to control the control switch 16 and the changeover switch 18 via a relay terminal 20b by a signal line 19a, so that the circuit breaker body 20 and the control box 21 can be remotely operated.

As described above, the control box 21 incorporating the alarm device 17 and the lock input means 19 can be installed near the load 3 so that the circuit breaker main body 20 can be remotely operated. In the case of an unusual use in which a current larger than the rated current value of the circuit breaker body 20 is passed, the operator of the load 3 can directly input the lock input means 19 for setting the unusual use. The output of the alarm device 17 indicating that the thermal limit has been reached can be obtained at the operating location of the load 3. Note that the alarm device 17 and the changeover switch 18 are not required, and the microcomputer 9 and the output device 10 may be directly connected as in the related art.

Embodiment 4 FIG. Embodiment 4 of the present invention will be described with reference to FIGS. 6, 7, 8, and 9. FIG. FIG. 6 is a diagram showing a configuration of the fourth embodiment of the present invention. FIG. 7 is a block diagram showing a configuration of a long time characteristic detecting unit according to the fourth embodiment of the present invention. Further, FIG. 8 is a diagram showing the time limit characteristic of the fourth embodiment of the present invention. FIG. 9 is a flowchart showing the operation of the fourth embodiment of the present invention.

In FIG. 6, the wiring circuit 1 to the output device 1
0, the alarm device 17 to the lock input means 19 are the same as those described in the first embodiment.

In FIG. 7, a long time characteristic detecting section 9b in the microcomputer 9 includes an effective value converting circuit 91, a level discriminating circuit 92, a heating level signal generating circuit 93,
Heat radiation level signal generation circuit 94 and correction signal generation circuit 95
, An adder circuit 96, and a signal output circuit 97.

The effective value conversion circuit 91 sets the detected current value of the wiring circuit 1 to an effective value. Also, a level determination circuit 92
Determines the level of the current value converted to the effective value. Further, when the current of the wiring circuit 1 is equal to or larger than the rated current in the level determination circuit 92, the heat generation level signal generation circuit 93 outputs a number of positive pulse signals A corresponding to the magnitude and duration.

In FIG. 8, reference numeral 61 denotes a reference characteristic, 62 denotes a heat radiation characteristic, and 63 denotes a correction characteristic.

When the current of the wiring circuit 1 is less than the rated current, the level discriminating circuit 92 generates a number of negative heat radiation pulse signals B corresponding to the difference between the rated current and the duration thereof. Output.

Further, when the lock input means 19 is in the ON state, the correction signal generating circuit 95 outputs a negative pulse signal C having a constant period. Then, the adding circuit 96 adds the pulse signals A, B, and C at predetermined time intervals. When the number of pulses added within a predetermined time exceeds a predetermined value, the output is converted to an analog output by the signal output circuit 97 and the output device 10 or the alarm device 17 is operated.

Next, the operation of the fourth embodiment will be described. In step 70, the microcomputer 9 performs an initialization process.

Next, in steps 71 to 72, the instantaneous characteristic detecting section 9d and the short time characteristic detecting section 9c of the microcomputer 9 output signals to the output device 10 in the case of instantaneous trip and short time trip. .

Next, in steps 73-74, the long time characteristic detecting section 9b of the microcomputer 9 determines whether the level discriminating circuit 92 determines that the current value of the wiring circuit 1 is equal to or higher than the rated current. As a result, a heat generation level signal A according to the reference characteristic 61 shown in FIG. 8 is output.

On the other hand, in Steps 73 and 80, when the current value of the wiring circuit 1 is less than the rated current, the long time characteristic detecting section 9b uses the heat radiation level signal generation circuit 94 to output the rated current and the heat radiation shown in FIG. A heat radiation level signal (-B) corresponding to the difference between the characteristics 62 is output.

Next, in steps 75 to 76, when the lock input means 19 is ON, the long time characteristic detecting section 9b uses the correction signal generating circuit 95 to calculate the difference between the predetermined correction characteristic 63 and the reference characteristic 61. The corresponding correction signal (-C) is output.

Then, in steps 77 to 79, the long time characteristic detecting section 9b sums these signals at predetermined time intervals by the adding circuit 96, and outputs the totaled pulse signal D.
If {D = A + (-B) + (-C)} exceeds a predetermined value,
The signal output circuit 97 outputs a signal.

Here, when the current value of the wiring circuit 1 is less than the rated current, outputting the negative heat radiation level pulse signal B means that the thermal melting degree of the circuit breaker due to the current normally flowing through the circuit breaker Is reflected in the timed characteristic. When the lock input means 19 is turned on from a state in which the current flowing normally is almost zero and a temporary overload state occurs, a predetermined period of the initial pulse count does not occur. The negative value of the heat radiation level pulse signal B is large, and the result of addition with the pulse signal A due to overcurrent is reduced.

On the other hand, when the normal current is close to the rated current value, there is almost no heat radiation level pulse signal B, and the pulse signal A due to the overcurrent is counted without being reduced. This means that the thermal melting degree of the circuit breaker is reflected in the timed characteristics.

As described above, by turning on the lock input means 19 provided in the circuit breaker, it is possible to allow the current of the wiring circuit 1 to be several times the rated current value for a short time. And the alarm output can be obtained at the allowable thermal limit.
The circuit breaker to be installed in a small rated current value is possible.

In the fourth embodiment, when the current of the wiring circuit 1 is equal to or higher than the rated current, a heating level signal generating circuit 93 for generating a heating level signal corresponding to the level determination of the current.
And a heat radiation level signal generating circuit 94 for generating a negative heat radiation level signal corresponding to a level difference between the current and the rated current when the current of the wiring circuit 1 is less than the rated current, and generating a predetermined negative correction signal. Correction signal generation circuit 95
An addition circuit 96 for adding the heat generation level signal, the heat radiation level signal, and the correction signal, a microcomputer 9 for performing a predetermined time-limited operation at the added signal level, and the wiring circuit 1 in response to the time-limited operation. Output device 1 to cut off
0, lock input means 1 for prohibiting cut-off output by closing
9, and the correction signal is excluded from the addition by opening the lock input means 19. Note that the alarm device 17 and the changeover switch 18 are not required, and the microcomputer 9 and the output device 10 may be directly connected as in the related art. Further, the alarm device 17 and the lock input means 19 may be installed near the load 3.

In each of the above embodiments, as described above, the current flowing through the circuit breaker is detected by the input of the lock input means 19, and the timed operation characteristic for interruption is temporarily set to allow the heat capacity of the circuit breaker. By changing the circuit breaker upward, it is possible to select a circuit breaker to be installed in the wiring circuit 1 that allows a short-time temporary overload state with a small rated current value.

[0059]

As described above, the overcurrent detecting device according to the present invention comprises: a load current detecting means for detecting a load current flowing through a wiring circuit; An overcurrent detecting means for outputting a trip signal when it reaches, an output device for opening a switching contact based on the trip signal to cut off a load current flowing through the wiring circuit, and outputting an alarm based on the trip signal When the alarm device is turned on, the changeover switch disconnects the overcurrent detection means and the output device, connects the overcurrent detection means and the alarm device, and sends a characteristic replacement signal to the overcurrent detection means. A lock input means for outputting the predetermined first time limit characteristic based on the characteristic replacement signal, the overcurrent detection means having a rated current larger than an original rated current. The wiring is replaced with a corresponding second time limit characteristic, and a trip signal is output when the detected load current reaches the replaced second time limit characteristic, so that a short-time temporary overload state is allowed. There is an effect that the circuit breaker to be installed on the electric circuit can be selected to have a smaller rated current value.

The overcurrent detecting device according to the present invention
As described above, the overcurrent detection means changes the discharge time constant of the capacitor based on the characteristic replacement signal, so that the predetermined first time limit characteristic corresponds to a rated current larger than the original rated current. Since the second time limit characteristic is replaced, the circuit breaker to be installed on the wiring circuit that allows a short-time temporary overload state can be selected with a smaller rated current value.

Further, the overcurrent detecting device according to the present invention
As described above, the overcurrent detection means changes the number of pulses based on the characteristic replacement signal to change the predetermined first time limit characteristic to the second current corresponding to the rated current larger than the original rated current. The number of pulses corresponding to the detected load current is replaced by the second
The trip signal is output when the time limit characteristic of
There is an effect that a circuit breaker to be installed in a wiring circuit that allows a short-time temporary overload state can be selected to one having a small rated current value.

Further, the overcurrent detecting device according to the present invention
As described above, the overcurrent detection unit includes the instantaneous characteristic detection unit, the short time characteristic detection unit, and the long time characteristic detection unit, and the instantaneous characteristic detection unit, the short time characteristic detection unit, and the output device Is directly connected, the long time characteristic detection unit and the output device are connected via the changeover switch, and the long time characteristic of the first predetermined time characteristic is changed to the original one based on the characteristic replacement signal. It replaces with the second time limit characteristic corresponding to the rated current larger than the rated current, and outputs a trip signal when the detected load current reaches the replaced second time limit characteristic. There is an effect that the circuit breaker to be installed on the wiring circuit that allows the overload state can be selected to have a small rated current value.

Further, as described above, in the overcurrent detecting device according to the present invention, since the alarm device and the lock input means are installed near the load connected to the wiring circuit, the overcurrent detecting device is not stationary. There is an effect that the load operator can directly input the lock input means for setting the usage, and the output of the alarm device for notifying the reaching of the thermal limit of the circuit breaker body can be obtained at the operation site of the load.

As described above, the overcurrent detecting device according to the present invention comprises: a load current detecting means for detecting a load current flowing through the wiring circuit;
An overcurrent detection unit that outputs a trip signal when the time limit characteristic of the trip is reached, an output device that opens and closes a switching contact based on the trip signal to cut off a load current flowing through the wiring circuit, A lock input means for outputting a characteristic replacement signal to the overcurrent detection means, wherein the overcurrent detection means sets the predetermined first time limit characteristic on the basis of the characteristic replacement signal to a value larger than an original rated current. It is replaced with a second time limit characteristic corresponding to the current, and a trip signal is output when the detected load current reaches the replaced second time limit characteristic, so that a short-time temporary overload state is allowed. This has the effect that the circuit breaker to be installed in the wiring circuit to be installed can be selected to have a smaller rated current value.

Further, the overcurrent detecting device according to the present invention
As described above, the overcurrent detection means changes the discharge time constant of the capacitor based on the characteristic replacement signal, so that the predetermined first time limit characteristic corresponds to a rated current larger than the original rated current. Since the second time limit characteristic is replaced, the circuit breaker to be installed on the wiring circuit that allows a short-time temporary overload state can be selected with a smaller rated current value.

The overcurrent detection device according to the present invention
As described above, the overcurrent detection means changes the number of pulses based on the characteristic replacement signal to change the predetermined first time limit characteristic to the second current corresponding to the rated current larger than the original rated current. The number of pulses corresponding to the detected load current is replaced by the second
The trip signal is output when the time limit characteristic of
There is an effect that a circuit breaker to be installed in a wiring circuit that allows a short-time temporary overload state can be selected to one having a small rated current value.

Further, the overcurrent detecting device according to the present invention
As described above, the overcurrent detecting means includes the instantaneous characteristic detecting section, the short time characteristic detecting section, and the long time characteristic detecting section, and based on the characteristic replacing signal, the predetermined first reverse time characteristic. Of these, the long time characteristic is replaced with a second time limit characteristic corresponding to a rated current larger than the original rated current, and a trip signal is output when the detected load current reaches the replaced second time limit characteristic. In addition, it is possible to select a circuit breaker having a small rated current value for a circuit breaker to be installed in a wiring circuit that allows a short-time temporary overload state.

Further, in the overcurrent detecting device according to the present invention, as described above, since the lock input means is installed near the load connected to the wiring circuit, the lock input means is set in an unusual manner. This has the effect that the operator of the load can directly input the input means, and the output of the alarm device for notifying that the thermal limit of the circuit breaker body has reached the thermal limit can be obtained at the operation site of the load.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment of the present invention.

FIG. 2 is a diagram showing a time limit characteristic of the first embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a second embodiment of the present invention.

FIG. 4 is a diagram showing a time limit characteristic of a second embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of a third embodiment of the present invention.

FIG. 6 is a diagram showing a configuration of a fourth embodiment of the present invention.

FIG. 7 is a diagram illustrating a configuration of a long time characteristic detecting unit according to a fourth embodiment of the present invention;

FIG. 8 is a diagram showing a time limit characteristic of a fourth embodiment of the present invention.

FIG. 9 is a flowchart showing the operation of the fourth embodiment of the present invention.

FIG. 10 is a diagram showing a configuration of a conventional overcurrent detection device.

FIG. 11 is a diagram showing a time limit characteristic of a conventional overcurrent detection device.

[Explanation of symbols]

1 wiring circuit, 2 switching contacts, 3 load, 4 current transformer,
5 rectifier circuit, 6 burden circuit, 7 waveform conversion circuit, 8
A / D conversion circuit, 9 microcomputer, 9a output port, 9b long time characteristic detector, 9c short time characteristic detector, 9d instantaneous characteristic detector, 10 output device, 11
Capacitor, 12 charging resistor, 13 diode, 14
Discharge resistance, 15 shunt resistance, 16 control switch, 17
Alarm device, 18 changeover switch, 19 lock input means, 17a, 19a signal line, 20 circuit breaker body,
Reference Signs List 21 control box, 91 effective value conversion circuit, 92 level discrimination circuit, 93 heat generation level signal generation circuit, 94 heat release level signal generation circuit, 95 correction signal generation circuit, 96
Adder circuit, 97 signal output circuit.

Claims (10)

[Claims] A load current detecting means for detecting a load current flowing through a wiring circuit; an overcurrent detecting means for outputting a trip signal when the detected load current reaches a predetermined first time limit characteristic; An output device that opens a switching contact based on a trip signal to cut off a load current flowing through the wiring circuit; an alarm device that outputs an alarm based on the trip signal; The overcurrent detection unit is connected to the overcurrent detection unit and the alarm device by disconnecting the current detection unit and the output device, and includes a lock input unit that outputs a characteristic replacement signal to the overcurrent detection unit. Replacing the predetermined first time limit characteristic with a second time limit characteristic corresponding to a rated current larger than the original rated current based on the characteristic replacement signal, Overcurrent detection device load current is and outputs the the trip signal reaches the second inverse time characteristic replaced the. 2. The overcurrent detecting means changes the discharge time constant of a capacitor based on the characteristic replacement signal, so that the predetermined first time limit characteristic corresponds to a rated current larger than an original rated current. 2. The overcurrent detection device according to claim 1, wherein the overcurrent detection device is replaced with a second time limit characteristic. 3. The overcurrent detecting means changes the predetermined first time limit characteristic to a second current corresponding to a rated current larger than an original rated current by changing a pulse number based on the characteristic replacement signal. 2. The overcurrent detection device according to claim 1, wherein the overcurrent detection device is replaced with a time limit characteristic, and a trip signal is output when the number of pulses according to the detected load current reaches the replaced second time limit characteristic. 4. The overcurrent detection means includes an instantaneous characteristic detection unit, a short time characteristic detection unit, and a long time characteristic detection unit, wherein the instantaneous characteristic detection unit, the short time characteristic detection unit, and the output device Is directly connected, the long time characteristic detection unit and the output device are connected via the changeover switch, and the long time characteristic among the predetermined first inverse time characteristic based on the characteristic replacement signal 3. The method according to claim 2, further comprising: replacing the load current with a second time limit characteristic corresponding to a rated current larger than the rated current, and outputting a trip signal when the detected load current reaches the replaced second time limit characteristic. Or the overcurrent detection device according to 3. 5. The alarm device and the lock input means,
The overcurrent detection device according to claim 4, wherein the overcurrent detection device is installed near a load connected to the wiring circuit. 6. A load current detecting means for detecting a load current flowing through a wiring circuit, an overcurrent detecting means for outputting a trip signal when the detected load current reaches a predetermined first time limit characteristic, An output device for opening a switching contact based on a trip signal to interrupt a load current flowing through the wiring circuit, and a lock input unit that outputs a characteristic replacement signal to the overcurrent detection unit when the switch is turned on, The overcurrent detection means replaces the predetermined first time limit characteristic with a second time limit characteristic corresponding to a rated current larger than the original rated current based on the characteristic replacement signal, and the detected load current is An overcurrent detection device that outputs a trip signal when the replaced second time limit characteristic is reached. 7. The overcurrent detection means changes the discharge time constant of the capacitor based on the characteristic replacement signal, so that the predetermined first time limit characteristic corresponds to a rated current larger than an original rated current. 7. The overcurrent detection device according to claim 6, wherein the overcurrent detection device is replaced with a second time limit characteristic. 8. The overcurrent detection means changes the predetermined first time limit characteristic to a second current corresponding to a rated current larger than an original rated current by changing a pulse number based on the characteristic replacement signal. 7. The overcurrent detection device according to claim 6, wherein the overcurrent detection device outputs the trip signal when the pulse number corresponding to the detected load current reaches the replaced second time limit characteristic. 9. The overcurrent detection means includes an instantaneous characteristic detection unit, a short time characteristic detection unit, and a long time characteristic detection unit, and based on the characteristic replacement signal, And replacing the long time characteristic with a second time limit characteristic corresponding to a rated current larger than the original rated current, and outputting a trip signal when the detected load current reaches the replaced second time limit characteristic. The overcurrent detection device according to claim 7 or 8, wherein: 10. The overcurrent detection device according to claim 9, wherein said lock input means is installed near a load connected to said wiring circuit.