JP2008186592A - Circuit breaker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a circuit breaker capable of supplying power to an internal electronic circuit section by an output current from a current transformer installed in an AC electric circuit, and easily obtaining an AC signal waveform corresponding to an AC signal waveform flowing in the electric circuit as an eddy current detection signal waveform and a ground fault detection signal waveform. <P>SOLUTION: The circuit breaker comprises: the current transformer 3 for detecting current flowing in the AC electric circuit 1; a rectification means 4 for rectifying current detected by the current transformer 3; a power circuit 5 for generating a power supply for operation by current outputted from the rectification means; a voltage conversion means 6 for converting current rectified by the rectification means 4 to voltage; and a subtraction circuit 70 for converting to an AC signal waveform corresponding to the waveform of an AC signal flowing in the AC electric circuit 1 by subtracting the half-wave voltage signal of each rectifier detected by the voltage detection means 6. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a circuit breaker provided with a device for supplying power from an electric current flowing through an electric circuit to an internal electronic circuit via a current transformer and detecting an amount of electric current flowing through the electric circuit.

  Conventionally, as a circuit breaker, a current transformer that detects the current of each phase of the AC circuit, a rectifier circuit that full-wave rectifies the secondary output of this current transformer, and a negative voltage that is proportional to the current of each phase A phase current detection resistor for output as a phase current, a phase current detection resistor for detecting a composite phase current level for ground fault current detection, and a level conversion circuit for converting a negative voltage output detected in each phase into a positive voltage And an A / D conversion circuit for converting the output of the level conversion circuit into a digital signal, a microcomputer for determining a time period according to the magnitude of the detected current level, and a power supply circuit connected to the electric circuit There is a circuit breaker configured to detect a current flowing in each phase of an electric circuit, output an overcurrent trip signal according to the detected current level, and interrupt the electric circuit via an opening / closing means (for example, a patent Reference 1).

Japanese Patent No. 3712886 (FIG. 6)

  The conventional circuit breaker shown in Patent Document 1 converts a negative voltage half-wave waveform output signal into a positive voltage half-wave waveform signal by a level conversion circuit via a phase current detection resistor of each phase. Overcurrent detection and ground fault detection are performed by converting to a digital signal via the / D conversion circuit and performing calculation processing with a microcomputer, but each of the overcurrent detection signal and the ground fault current detection signal has a half-wave waveform. Therefore, when a short-time overcurrent or ground fault current flows in the electric circuit, there is a problem that the detection accuracy of the overcurrent tripping operation or the ground fault tripping operation is deteriorated depending on the detection timing.

  In addition, as other detection functions for overcurrent detection and ground fault current detection, processing of detection functions such as harmonic current measurement that requires Fourier transform processing, power measurement that multiplies the current value and voltage value of the circuit is performed. In this case, the current detection signal waveform to be taken into the microcomputer cannot be processed with the half-wave signal waveform obtained by the conventional configuration, and it is necessary to add another current detection current transformer. There has been a problem that becomes large.

  Further, since the operation power supply for the internal electronic circuit is supplied from the electric circuit via the power supply circuit, there is a problem that the size of the device increases.

  The present invention was made to solve the problems of the conventional circuit breaker as described above, and supplies power to the internal electronic circuit section by the output current from the current transformer installed in the electric circuit. As an overcurrent detection signal waveform and a ground fault detection signal waveform, it is possible to easily obtain an AC signal waveform corresponding to the AC signal waveform flowing in the electric circuit, and it flows in the electric circuit without adding another measurement current transformer. The object of the present invention is to obtain a circuit breaker capable of detecting various amounts of current.

  The circuit breaker according to the present invention is a circuit breaker that opens and closes an AC circuit composed of a plurality of unit circuits corresponding to each phase of the AC, and is disposed in each of the plurality of unit circuits and corresponds to the corresponding unit circuit. A plurality of current transformers for generating an output current corresponding to the flowing current, a rectifying means for rectifying the output current of the current transformer, and a current output by the rectifying means for positive or negative of the alternating current for each phase. A voltage converting means for converting into a corresponding pair of half-wave voltage signals, and a subtracting circuit for subtracting the pair of half-wave voltage signals converted by the voltage converting means into an alternating voltage signal corresponding to each phase; An arithmetic circuit for calculating a current value flowing through the plurality of unit electric circuits based on the AC voltage signal converted by the subtracting circuit, and a trip signal when the value calculated by the arithmetic circuit is equal to or greater than a predetermined value. Output A power supply circuit that generates power to be supplied to the subtracting circuit, the arithmetic circuit, and the tripping means based on an output current of the rectifying means, and a tripping signal output by the tripping means. An open / close contact for interrupting the AC electric circuit is provided.

  A circuit breaker according to the present invention includes a plurality of current transformers that are respectively provided in a plurality of unit electric circuits and generate an output current corresponding to a current flowing through the corresponding unit electric circuit, and a rectifier that rectifies the output current of the current transformer Means, voltage converting means for converting the current output by the rectifying means into a pair of half-wave voltage signals corresponding to the positive and negative of the alternating current for each phase of alternating current, and the pair of voltage converted by the voltage converting means A subtracting circuit that subtracts a half-wave voltage signal to convert it to an AC voltage signal corresponding to each phase, and calculates a current value that flows through the plurality of unit circuits based on the AC voltage signal converted by the subtracting circuit. An arithmetic circuit; tripping means for outputting a trip signal when a value calculated by the arithmetic circuit is equal to or greater than a predetermined value; and the subtracting circuit, the arithmetic circuit and the tripping circuit based on an output current of the rectifying means. Remover A power supply circuit for generating power to be supplied to the power supply circuit and an open / close contact for interrupting the AC circuit based on the trip signal output by the tripping means. It is possible to easily obtain an AC signal waveform corresponding to the AC signal waveform flowing in the electric circuit as the overcurrent detection signal waveform and the ground fault detection signal waveform while supplying power to the internal electronic circuit unit by the output current from the device. This makes it possible to improve the detection accuracy of the overcurrent tripping operation or the ground fault tripping operation even when a short overcurrent or ground fault current flows in the electric circuit. Furthermore, it is possible to easily detect various current amounts flowing in the electric circuit.

Embodiment 1 FIG.
1 is a block diagram showing a circuit breaker according to Embodiment 1 of the present invention. In FIG. 1, the switching contact 2 of the circuit breaker has a three-pole switching contact, and includes a first phase AC circuit 1a, a second phase AC circuit 1b, and a third phase AC circuit 1c, which are unit circuits. When the electromagnetic device 11 is energized, the circuit is opened and the AC circuit 1 is cut off. The current transformer 3 includes a first phase current transformer 3a, a second phase current transformer 3b, and a third phase provided in the first phase AC circuit 1a, the second phase AC circuit 1b, and the third phase AC circuit 1c, respectively. It consists of a current transformer 3c and outputs a current signal proportional to the current in the AC circuit 1.

  The rectifier circuit 4 as the rectifier means performs full-wave rectification on the current signal output from the current transformer 3 and inputs the current signal to the power supply circuit 5. The power supply circuit 5 generates an operation power supply used for an electronic circuit inside the circuit breaker based on the input from the rectifier circuit 4, and includes a subtractor circuit means 70, an adder circuit 12, an A / D converter circuit 8, and a microcomputer, which will be described later. Operating power is supplied to 9 (hereinafter referred to as CPU) 9, electromagnetic device 11 and the like.

  The current detection resistor 6 includes first phase current detection resistors 6a and 6b corresponding to the first phase current transformer 3a, second phase current detection resistors 6c and 6d corresponding to the second phase current transformer 3b, and a third phase. The first phase current detector 3e, the second phase current transformer 3b, and the third phase current transformer 3c detected by the third phase current detector resistors 6e and 6f corresponding to the current transformer 3c. Current signals corresponding to the currents of the phase AC circuit 1a, the second phase AC circuit 1b, and the third phase AC circuit 1c are converted into voltage signals, respectively. The voltage signal converted by the current detection resistor 6 is a negative voltage across each of the first phase current detection resistors 6a and 6b, the second phase current detection resistors 6c and 6d, and the third phase current detection resistors 6e and 6f. Output as a half-wave voltage waveform. In the present invention, the current detection resistor 6 constitutes voltage conversion means for converting the current output from the rectifier circuit into a pair of half-wave voltage signals corresponding to the positive and negative of the alternating current for each phase of the alternating current.

  The subtraction circuit 70 includes a first phase subtraction circuit 70a, a second phase subtraction circuit 70b, and a third phase subtraction circuit 70c corresponding to the first phase AC circuit 1a, the second phase AC circuit 1b, and the third phase AC circuit 1c, respectively. It is configured. FIG. 2 shows the configuration of the first phase subtraction circuit 70a. As shown in FIG. 2, the subtraction circuit 70a includes a differential amplifier circuit 7g. The differential amplifier circuit 7g includes an amplifier 7a for amplifying a negative half-wave voltage waveform generated at both ends of the first phase current detection resistors 6a and 6b as an input signal, and an amplification factor of the amplifier 7a. It comprises resistors 7b, 7c, 7d and 7e which are amplification factor setting means for determining, and DC reference voltage means 7f which determines the DC voltage output value of the output signal from the amplifier 7a.

  The resistors 7h and 7i and the Zener diodes 7j and 7k constitute an overvoltage protection means against the overvoltage input of the differential amplifier circuit 7g, and one ends of the resistors 7h and 7i are respectively connected to the first phase current detection resistors 6a and 6b. The other end is connected to the anode side of the Zener diodes 7j and 7k. The cathode sides of the Zener diodes 7j and 7i are grounded together with the other ends of the first phase current detection resistors 6a and 6b, respectively.

  The input sides of the second phase subtraction circuit 70b and the third phase subtraction circuit 70c are connected to one end of the corresponding second phase current detection resistors 6c and 6d and one end of the third phase current detection resistors 7e and 7f, respectively. Yes. Other configurations of the second phase subtracting circuit 70b and the third phase subtracting circuit 70c are the same as the configurations of the first phase subtracting circuit 70a.

Now, the output current of the first phase current transformer 3a is (a1), the voltages between both ends of the first phase current detection resistors 6a and 6b are (b1) and (c1), respectively, and the DC reference voltage of the DC reference voltage voltage means 7f. When the voltage is V1, the voltages (b1) and (c1) are applied to the input terminals of the first phase subtracting circuit 70a, and the output voltage (d1) shown in the following (Equation 1) is output.
(D1) = (b1)-(c1) + V1 (Formula 1)

3 shows the output current (a1) of the first phase current transformer 3a, the voltages (b1) and (c1) across the first phase current detection resistors 6a and 6b, and the output (d1) of the first phase subtraction circuit 70a. ) Respectively.
As shown in FIG. 3, the output voltage (d1) of the first phase subtraction circuit 70a has a waveform having a phase corresponding to the output current (a1) of the first phase current transformer 3a, and the value is a DC reference. The direct current is shifted to the positive side by the direct current reference voltage V1 of the voltage 7f. Similarly, the output (d2) of the second phase subtracting circuit 70b and the output of the third phase subtracting circuit 70c are AC component components having phases corresponding to the output currents (a2) and (a3) of the current transformers 3b and 3c, respectively. The waveform has a waveform and its value is a direct current shifted to the positive side by the value of the direct current reference power source V1. As a result, the output voltages (d1), (d2), and (d3) of the subtracting circuits 70a, 70b, and 70c can be directly input to the A / D conversion circuit 8 to be described later, which cannot input a negative voltage signal. It becomes possible. The adding circuit 12 receives the output voltages (d1), (d2), and (d3) of the first phase subtracting circuit 70a, the second phase subtracting circuit 70b, and the third phase subtracting circuit 70c, and adds these output voltages. Output voltage (e).

  FIG. 4 shows the relationship of the waveform of the output voltage output from the subtraction circuit 7 and the addition circuit 12 with respect to the waveform of the output current of the current transformer 3, and (a) of FIG. The output currents (a1), (a2), and (a3) of the current transformer 3a, the second phase current transformer 3b, and the third phase current transformer 3c are shown. FIG. 4 (d) shows the first phase subtraction circuit 70a. 4 shows the output voltages (d1), (d2), and (d3) of the second-phase subtracting circuit 70b and the third-phase subtracting circuit 70c, and (e) of FIG. 4 shows the output voltage (e) of the adding circuit 12. Yes. 4A, 4D, and 4E show the three-phase AC current of the AC circuit 1 when the three-phase steady load (A), the three-phase overload (B), and the AC circuit 1 Each of the poles is shown separately in the case of a single-pole ground fault (C) when a ground fault occurs.

  That is, in FIG. 4, in the case of three-phase steady load (A), the output of the adder circuit 12 obtained by adding the output voltages (d1), (d2), and (d3) of the subtractor circuits 70a, 70b, and 70c. The voltage (e) is a DC voltage having a constant value Ve as shown in FIG. In the case of three-phase overload (B), since overcurrent flows through the AC circuits 1a, 1b, and 1c of each phase of the AC circuit 1, the output currents (a1) and (a) of the respective current transformers 3a, 3b, and 3c ( The amplitudes of a2) and (a3) are large, and therefore the amplitudes of the AC components of the output voltages (d1), (d2), and (d3) of the subtracting circuits 70a, 70b, and 70c of the respective phases are overcurrent detection threshold values. It will exceed Ho. In the case of a single-pole ground fault (C) in the AC circuit 1, only the single-pole component appears as an AC component at the output (e) of the adder circuit 12 as shown in FIG. The amplitude value exceeds the ground fault detection threshold Hg.

  Returning to FIG. 1, the transformer 13 has an input terminal connected between the AC circuits 1 and an output terminal connected to the voltage signal input circuit 14. The voltage signal input circuit 14 receives the output signal from the transformer 13 and outputs a voltage signal corresponding to the voltage between the AC circuits 1 based on the output signal. The A / D conversion circuit 8 is an output voltage (d1), (d2), (d3) of the subtraction circuit 70, an output signal (e) of the addition circuit 12, and an output of the voltage signal input circuit 14, which are analog signals. A certain voltage signal is inputted, these signals are converted into digital signals, respectively, and inputted to the CPU 9. The CPU 9 detects the presence / absence of an overload of the AC circuit 1 and the presence / absence of a ground fault by digital processing based on each input digital signal. The CPU 9 calculates the voltage value and frequency of the AC circuit 1 based on the digital signal based on the output signal of the voltage signal input circuit 14, and the voltage value and frequency value, and the output current of the current transformer 3. The harmonic current, power value, power amount and the like of the AC circuit 1 are calculated using the digital signal based on the above.

  When the CPU 9 detects an overload of the AC circuit 1 or a ground fault, the trigger circuit 10 is given a trip signal from the CPU 9 and energizes the electromagnetic device 11. The energized electromagnetic device 11 opens the switching contact 2 by the electromagnetic force and interrupts the AC circuit 1. A display unit 15 constituted by a 7-segment LED or a liquid crystal display device displays the calculation result of the CPU 9.

  Next, the operation of the circuit breaker according to Embodiment 1 of the present invention will be described. In FIG. 1 to FIG. 4, when the switching contact 2 of the circuit breaker is turned on, it corresponds to the three-phase AC current flowing in the first-phase AC circuit 1a, the second-phase AC circuit 1b, and the third-phase AC circuit 1c. The output currents (a1), (a2), and (a3) are output from the first phase current transformer 3a, the second phase current transformer 3b, and the third phase current transformer 3c. Rectified and input to the power supply circuit 5. Based on this input, the power supply circuit 5 generates an operation power supply used for an electronic circuit in the circuit breaker, and subtracts the circuit means 70, the adder circuit 12, the A / D conversion circuit 8, and a microcomputer (hereinafter referred to as a CPU). 9, and operating power is supplied to the electromagnetic device 11 and the like.

  The output currents (a1), (a2), and (a3) from the current transformers 3a, 3b, and 3c are the first phase current detection resistors 6a and 6b and the second phase current that constitute the current detection resistor 6, respectively. The detection resistors 6c and 6d and the third phase current detection resistors 6e and 6f are converted into negative half-wave voltage outputs as described above, and the corresponding first phase subtraction circuit 70a, second phase subtraction circuit 70b, This is supplied to the three-phase subtracting circuit 70c. Each of the subtracting circuits 70a, 70b, and 70c subtracts the two input voltage signals, and outputs the output voltages (d1), (d2), and (d3) based on the above (Equation 1). This is given to the D conversion circuit 8. On the other hand, the adding circuit 12 adds the output voltages (d1), (d2), and (d3) of the respective subtracting circuits 70a, 70b, and 70c, and outputs an output voltage (e), which is output to the A / D conversion circuit. Give to 8. The A / D conversion circuit 8 converts these output voltages (d1), (d2), (d3), and (e) input in analog form into digital signals and inputs them to the CPU 9.

  Assuming that there is no abnormality in the AC circuit 1 and the three-phase load is in a steady state, as shown in (d) in FIG. 4A, the first phase subtraction circuit 70a, the second phase The output voltages (d1), (d2), and (d3) of the subtraction circuit 70b and the third phase subtraction circuit 70c do not exceed the overcurrent detection threshold value Ho. Therefore, the CPU 9 does not detect an overcurrent, the trigger circuit 10 does not energize the electromagnetic device 11, and the switching contact 2 is not opened.

  Further, the CPU 9 determines the voltage value, current value, frequency, harmonic current, power of the AC circuit 1 based on the input output voltages (d1), (d2), (d3), and (e). A value, electric energy, etc. are calculated and the display unit 15 displays the calculation result. As a result, the energization information of the AC circuit 1 can be measured with a simple configuration and displayed.

  Next, if an overcurrent due to overload or the like flows in the AC circuit 1, as shown in FIG. 4B, (a), the first phase current transformer 3a and the second phase current transformer 3b. The output currents (a1), (a2), and (a3) of the third phase current transformer 3c are larger than those in the steady state. Therefore, the A / D conversion circuit 8 and the CPU 9 are based on the output voltages (d1), (d2), and (d3) of the first phase subtraction circuit 70a, the second phase subtraction circuit 70b, and the third phase subtraction circuit 70c. The amount of current flowing through each phase calculated by the configured arithmetic circuit exceeds the overcurrent detection threshold Ho. Thus, the CPU 9 detects an overcurrent and gives a trip signal to the trigger circuit 10. The trigger circuit 10 receives the trigger signal, energizes the electromagnetic device 11, opens the switching contact 2, and interrupts the AC circuit 1. Thus, the rectified current supplied to the power supply circuit 5 is detected as a half-wave voltage signal by the current detection resistor 6 which is a voltage conversion means, and the detected half-wave voltage signal is converted into an AC voltage signal by the subtraction circuit 70. By calculating, it becomes possible to detect the overcurrent flowing through the electric circuit with high accuracy.

  Also, if a ground fault occurs in any phase of the AC circuit 1, for example, the first phase AC circuit 1a, as shown in (a) of FIG. The amplitude balance between the output current (a1) of the first phase current transformer 3a and the output currents (a2) and (a3) of the second phase current transformer 3b and the third phase current transformer 3c is lost. Accordingly, the output voltage (e) of the adder circuit 12 which is the added waveform of the output voltages (d1), (d2), and (d3) of the first phase subtractor circuit 70a, the second phase subtractor circuit 70b, and the third phase subtractor circuit 70c. The ground fault current amount calculated by the arithmetic circuit constituted by the A / D conversion circuit 8 and the CPU 9 exceeds the ground fault detection threshold value Hg. Thus, the CPU 9 detects a unipolar ground fault and provides a trip signal to the trigger circuit 10. The trigger circuit 10 receives the trigger signal, energizes the electromagnetic device 11, opens the switching contact 2, and interrupts the AC circuit 1. In addition, even if it is a ground fault other than the first phase AC circuit 1a, it is possible to detect the ground fault and block the AC circuit 1 in the same manner as described above.

  As described above, according to the circuit breaker according to the first embodiment of the present invention, the power supply circuit 5 supplies power to the internal electronic circuit via the current transformer 3 based on the current flowing in the AC circuit 1. The subtracting circuit 70 can easily obtain an AC signal waveform corresponding to an AC signal waveform flowing in the electric circuit as an overcurrent detection signal waveform and a ground fault detection signal waveform, and a short-time overcurrent or ground fault current flows. Even in such a case, the detection accuracy of the overcurrent tripping operation or the ground fault tripping operation can be improved. Further, it is possible to easily detect harmonic current measurement, power measurement, etc. as various current amounts flowing in the AC circuit 1.

It is a block diagram which shows the circuit breaker in Embodiment 1 of this invention. It is a block diagram which shows the structure of the subtraction circuit of FIG. It is a wave form diagram which shows the relationship of the input-output voltage of the subtraction circuit of FIG. It is a wave form diagram which shows the subtraction circuit of the circuit breaker in Embodiment 1 of this invention, and the input-output voltage of an addition circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC circuit 1a 1st phase AC circuit 1b 2nd phase AC circuit 1c 3rd phase AC circuit 2 Switching contact 3 Current transformer 3a 1st phase current transformer 3b 2nd phase current transformer 3c 3rd phase current transformer 4 Rectifier circuit 5 Power supply circuit 6 Current detection resistor 6a First phase current detection resistor 6b Second phase current detection resistor 6c Third phase current detection resistor 70 Subtraction circuit 70a First phase subtraction circuit 70b Second phase subtraction circuit 70c Third phase subtraction Circuit 8 A / D conversion circuit 9 Microcomputer 10 Trigger circuit 11 Electromagnetic device 12 Addition circuit 13 Transformer 14 Voltage signal input circuit 15 Display unit

Claims (4)

  A circuit breaker that opens and closes an AC circuit composed of a plurality of unit circuits corresponding to each phase of the AC, and generates an output current corresponding to a current that flows through the corresponding unit circuit that is disposed in each of the plurality of unit circuits. A plurality of current transformers, rectifying means for rectifying the output current of the current transformer, and a current output by the rectifying means into a pair of half-wave voltage signals corresponding to the positive and negative of the alternating current for each phase. Voltage converting means for converting, a subtracting circuit for subtracting the pair of half-wave voltage signals converted by the voltage converting means to convert to AC voltage signals corresponding to the respective phases, and the converted by the subtracting circuit An arithmetic circuit for calculating a current value flowing through the plurality of unit electric circuits based on an AC voltage signal, a trip means for outputting a trip signal when a value calculated by the arithmetic circuit is a predetermined value or more, and Of rectifying means A power supply circuit that generates power to be supplied to the subtraction circuit, the arithmetic circuit, and the tripping unit based on a force current; and an open / close contact that shuts off the AC circuit based on a trip signal output by the tripping unit A circuit breaker comprising:   The subtraction circuit includes a differential amplifier circuit that differentially amplifies a pair of half-wave voltage signals converted by the voltage converter, an amplification factor setting unit that sets an amplification factor that is amplified by the differential amplifier circuit, 2. An overvoltage protection unit that protects the differential amplifier circuit when a half-wave voltage signal is equal to or greater than a predetermined value, and a reference voltage unit that defines a reference of a voltage output from the subtraction circuit. Circuit breaker as described.   An adder circuit for adding an AC voltage signal corresponding to each phase output from the subtractor circuit, and calculating a ground fault current of the AC circuit by the arithmetic circuit based on an output signal of the adder circuit; The circuit breaker according to claim 1 or 2, wherein the trip means outputs a trip signal when the measured value is equal to or greater than a predetermined value.   Voltage detection means for detecting the voltage of the AC circuit, and based on the voltage of the AC circuit detected by the voltage detection means and the AC voltage signal output from the subtraction circuit, the voltage, current, and power of the AC circuit 4. The circuit interruption according to claim 1, wherein at least one of electric energy and harmonic current is calculated by the calculation means, and the calculation result is displayed on a display unit. vessel.

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