JP5461293B2 - Electronic breaker responsive to short circuit current in high impedance circuit - Google Patents

Description

  The present invention relates to an electronic breaker provided with an electronic overcurrent trip device that detects a short-circuit current flowing in a high impedance circuit and trips a main contact.

  Conventionally, an electronic breaker 51 as shown in FIG. 3 is known (Patent Document 1). In this breaker 51, when an overcurrent exceeding the rated current flows through the electric circuit 52, the electronic overcurrent trip device 53 trips the main contact 54. When a large short circuit current flows through the electric circuit 52 due to a short circuit accident of the load device 55 or the like, the mechanical overcurrent tripping device 56 instantaneously disconnects the main contact 54.

  The CPU 57 monitors the line current based on the output of the current sensor 59, performs an inverse time limit or a fixed time operation according to the magnitude of the overcurrent, and outputs a trip command to the electronic overcurrent trip device 53. The power supply circuit 58 converts the AC voltage extracted from the electric circuit 52 on the secondary side of the main contact 54 into a required DC voltage (for example, DC 5 V), and supplies it to the CPU 57 as an operating voltage.

JP 2009-163882 A

  By the way, as shown in FIG. 4, when the short-circuit current flows through the impedances Z1 and Z2 of the distribution line and the load device, the short-circuit current value Is is limited to a value obtained from Equation 1 in FIG. The current tripping device 56 becomes a halfway size that does not operate. Further, the electric circuit voltage Ve decreases to a value obtained from Equation 2, and becomes 50% of the standard voltage when Z1 = Z2, thereby reducing the supply voltage to the CPU 57 by half.

  Therefore, according to the conventional electronic breaker 51, when a short circuit accident occurs in the high impedance circuit, the mechanical overcurrent trip device 56 may not operate, and the electronic overcurrent is stopped by the CPU 57 being stopped. There is a possibility that the tripping device 53 may not operate. Accordingly, there is a problem that the electronic breaker 51 is in an unprotected state against a short-circuit accident, and the short-circuit current continues to flow through the electric circuit 52.

  Therefore, the object of the present invention is to ensure the safety of the electric circuit by replacing the mechanical overcurrent tripping device with the electronic overcurrent tripping device in the event of a short-circuit accident in a high impedance circuit, and by removing the main contact. It is to provide an electronic breaker that can be used.

  In order to solve the above-described problems, the present invention provides an electronic overcurrent trip device that trips the main contact in response to a trip command from the CPU when an overcurrent flows in the circuit, and a short-circuit current in the circuit. In an electronic breaker equipped with a mechanical overcurrent trip device that instantaneously trips the main contact when it flows, the power supply circuit that supplies the operating voltage to the CPU and the AC voltage extracted from the circuit are converted to DC voltage A rectifying element that supplies DC power to the power supply circuit after smoothing the DC voltage is provided, and when the circuit voltage drops due to a short circuit accident, the CPU operates with the discharge voltage of the capacitor and checks the short circuit current flowing in the circuit. When the short-circuit current exceeds a preset reference value smaller than the operating current value of the mechanical overcurrent trip device, the CPU outputs a trip command to the electronic overcurrent trip device. And features.

  The electronic breaker of the present invention is characterized in that the smoothing voltage of the capacitor is monitored by the CPU, and when the smoothing voltage drops to a predetermined threshold, the CPU starts checking the short circuit current.

  In the electronic breaker of the present invention, even when the circuit voltage drops due to a short circuit accident in the high impedance circuit, the CPU operates with the discharge voltage of the capacitor and checks the short circuit current flowing through the circuit. For this reason, when a short-circuit current with a halfway magnitude when the mechanical overcurrent tripping device does not operate flows, the electronic overcurrent tripping device immediately replaces the main contact with the mechanical overcurrent tripping device. This has the effect of ensuring the safety of the electric circuit.

It is a circuit diagram of the electronic breaker which shows one Embodiment of this invention. It is a time chart which shows operation | movement of an electronic breaker. It is a circuit diagram which shows the conventional electronic breaker. It is a circuit diagram which points out the problem in a high impedance circuit.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. An electronic breaker 1 shown in FIG. 1 is equipped with an electronic overcurrent trip device 2 and a mechanical overcurrent trip device 3. The electronic overcurrent trip device 2 includes a trip coil 9 that trips the main contact 5 on the electric circuit 4, its drive circuit 17, and a CPU 7. The mechanical overcurrent tripping device 3 is not particularly limited, and includes, for example, a fixed electromagnetic piece and a movable electromagnetic piece.

  A current sensor 6 is provided on each electric wire of the electric circuit 4, and a detection signal thereof is sent to the arithmetic control unit 13 via the A / D conversion unit 10 of the CPU 7. The arithmetic control unit 13 determines overcurrent and short circuit current separately according to the control program 11, and various parameters used for the determination are stored in the data storage unit 12. Then, the CPU 7 outputs a trip command from the input / output unit 14 to the trip coil drive circuit 17.

  A power circuit 8 is connected to the secondary electric circuit 4 with respect to the main contact 5 via a diode 15 and a capacitor 16. The diode 15 as a rectifier element rectifies the AC voltage taken out from the electric circuit 4 into a DC voltage, and the capacitor 16 smoothes the DC voltage and supplies it to the trip coil drive unit 17 and the power supply circuit 8. The power supply circuit 8 steps down the smoothed DC voltage to a required value (for example, DC 5 V) and supplies it to the CPU 7 as an operating voltage.

  Two resistors R1, R2 are provided between the capacitor 16 and the CPU 7, and the voltage smoothed by the capacitor 16 is divided at an appropriate ratio. The node 18 of the resistors R1 and R2 is connected to the A / D converter 10 of the CPU 7, and the arithmetic control unit 13 constantly monitors the smoothing voltage of the capacitor 16 based on the voltage at the node 18.

  Next, the operation of the electronic breaker 1 configured as described above will be described. When an overcurrent exceeding the rated current flows in the electric circuit 4, the CPU 7 performs an inverse time limit or a fixed time operation according to the magnitude of the overcurrent, outputs a trip command to the drive circuit 17, and drives the trip coil 9. Then, the main contact 5 is pulled off. When a large short-circuit current (for example, a large current exceeding 1000% of the rated current) flows in the electric circuit 4, the mechanical overcurrent trip device 3 instantaneously trips the main contact 5.

  On the other hand, when a short-circuit accident occurs in the high-impedance circuit (see FIG. 4), the circuit voltage between R and T decreases as shown in FIG. 2, the capacitor 16 starts discharging, and the voltage is supplied to the power supply circuit 8. To do. Since the discharge of the capacitor 16 proceeds slowly, the output voltage of the power supply circuit 8 maintains a high level for a relatively long time. For this reason, the electronic overcurrent tripping device 2 including the CPU 7 can operate normally for a while using the discharge voltage of the capacitor 16.

  When the voltage at the node 18 of the resistors R1 and R2 (smooth voltage of the capacitor 16) drops to a preset threshold value (see FIG. 2), the CPU 7 starts checking the short-circuit current based on the output of the current sensor 6. When the short-circuit current exceeds a reference value (for example, 800% of the rated current) set smaller than the operating current value (for example, 1000% of the rated current) of the mechanical overcurrent trip device 3, the CPU 7 Outputs a trip command to the drive circuit 17 and immediately trips the main contact 5 with the trip coil 9.

  Therefore, according to this electronic breaker 1, even when a short-circuit current having a halfway magnitude flows through the impedance of the distribution line or load device, the electronic overcurrent tripping device 2 is operated to Safety can be ensured. In addition, the CPU 7 has an advantage that the short-circuit current can be accurately detected by setting an appropriate check time (see FIG. 2) during the limited discharge period by monitoring the smoothing voltage of the capacitor 16.

  The electronic breaker of the present invention is not limited to the three-phase three-wire electric circuit 4 shown in FIG. 1, and can be applied to, for example, a single-phase two-wire electric circuit and a single-phase three-wire electric circuit. In addition, the present invention is not limited to the above embodiment, and can be implemented by appropriately changing the configuration of each part without departing from the spirit of the invention.

DESCRIPTION OF SYMBOLS 1 Electronic breaker 2 Electronic overcurrent tripping device 3 Mechanical overcurrent tripping device 4 Electric circuit 5 Main contact 6 Current sensor 7 CPU
15 diode 16 capacitor

Claims (2)

When an overcurrent flows in the path, the electronic overcurrent tripping device in response to the trip command is tripping the main contacts from CPU, when the short-circuit current flows in the path, instantaneously the main contact In an electronic breaker with a mechanical overcurrent trip device to trip,
A power supply circuit for supplying an operating voltage to the CPU, a rectifying element for converting an AC voltage taken out from the path into a DC voltage, a capacitor to be supplied to the power supply circuit to smooth the DC voltage provided,
When the path voltage drops by short circuit, the CPU is operated by the discharge voltage of the capacitor, the check the short-circuit current flowing through the path, the operating current value of the short-circuit current is the mechanical overcurrent tripping device when exceeding the predetermined reference value smaller than the electronic breaker wherein said CPU outputs a trip command to the above electronic overcurrent tripping device. The smoothed voltage of the capacitor is monitored by the CPU, when the smoothed voltage falls to a predetermined threshold value, the electronic circuit breaker according to claim 1, wherein the CPU initiates the checking of the short-circuit current.

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