JP2001177982A - Protection breaker for open-phase of neutral conductor of single-phase three-wire system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protection breaker that operate on an overvoltage caused by the open-phase of a neutral conductor and that will not activate by high-frequency noise. SOLUTION: A ferrite core bead 10 is inserted in a voltage detecting circuit, that transmits voltage information between voltage lines L1, L2 and a neutral conductor N to an abnormal voltage monitor circuit 6 that detects overvoltage by the open-phase of the neutral conductor and outputs operating signals of a tripping coil 3, that opens a contact point 4 of a main circuit 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-phase three-wire line having a function of protecting a load by interrupting a circuit against a high voltage generated when a neutral line of a single-phase three-wire line is lost. The present invention relates to a line break protection circuit breaker, and more particularly to a measure against high frequency noise.

[0002]

2. Description of the Related Art In recent years, with the spread of single-phase three-wire distribution circuits,
A circuit breaker with an AA neutral-phase-loss protection function for protecting connected equipment from abnormal voltage due to the neutral phase-loss is widely used. As shown in the circuit diagram of FIG. 3, such a conventional circuit breaker with AA neutral line open phase protection has the voltage lines L1, L2
And the neutral line N (hereinafter referred to as L1-N and L2-N) are rectified by the diodes D1 and D2, divided by the two resistors R1 and R2, and applied to the resistor R2. The voltage is monitored between a and c of the abnormal voltage detection circuit 6, and if an overvoltage is applied between L1 and N or between L2 and N due to the occurrence of a phase loss of the neutral line N, the voltage is applied across the resistor R2. The applied voltage rises,
When the voltage exceeds a certain level, the ON signal of the thyristor 9 is output from the terminal b of the abnormal voltage detecting circuit to turn on the thyristor 9, excite the trip coil 3 and perform the trip operation of the contact 4.

[0003]

On the other hand, as a load device, a large number of circuits that easily generate high-frequency noise, such as inverter control and fuzzy control, are used as control methods. If such high-frequency noise is present between the lines or between L2 and N2, a pulse-like high voltage generated by the noise is determined to be an overvoltage due to phase loss, and unnecessary operation may be performed. As the number of circuits increases, unnecessary operation of the AA neutral line open-phase protection circuit breaker tends to increase.

In view of the above problems, an object of the present invention is to provide an AA neutral line open-phase protection circuit breaker that performs an interrupting operation due to an overvoltage due to an open phase and does not perform an interrupting operation with high-frequency noise. .

[0005]

In order to solve the above-mentioned problems, the invention of claim 1 protects a circuit by shutting off a main circuit when a neutral line of a single-phase three-wire circuit is lost. AA neutral line open phase protection circuit breaker comprising an open phase detection circuit, wherein the open phase detection circuit detects a line voltage,
An abnormal voltage monitoring circuit that receives the voltage information of the voltage detection circuit, detects an abnormal voltage generated by a neutral line open phase, and outputs a cutoff signal of a main circuit, and includes a ferrite core bead in the voltage detection circuit. It is characterized by intervening.

[0006]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a circuit diagram showing an example of an AA neutral line open-phase protection circuit breaker according to the present invention. In FIG. 1, a main circuit 2 is provided with a contact 4 that is opened by the operation of a trip coil 3 and detects leakage. A current transformer 5 is provided, and an abnormal voltage monitoring circuit 6 detects leakage and abnormal voltage.

The open-phase detecting circuit includes an abnormal voltage monitoring circuit 6 formed as an IC (integrated circuit) and diodes D1 and D2 for rectifying voltages between L1 and N2 and between L2 and N, and resistors R1 and R2.
Is formed by a voltage detection circuit 7 connected between a and c of the abnormal voltage monitoring circuit 6 and a voltage applied to both ends of the resistor R2 is formed. When an overvoltage is applied between L2 and N2, the voltage applied across the resistor R2 rises, and when the voltage exceeds a certain level, the abnormal voltage monitoring circuit 6 determines that there is no phase and turns the thyristor 9 on. Is output from the terminal b, the thyristor 9 is turned on, the trip coil 3 is excited and operated, and the contact 4 is tripped.

As shown in the figure, a ferrite core bead 10 is mounted on a voltage detection line having a resistance R1. The ferrite core beads 10 exhibit a low resistance value at low frequencies such as commercial frequencies, but exhibit a large resistance value at high frequencies. Appears as normal, but the high-frequency noise appears to be greatly attenuated. Therefore, the abnormal voltage monitoring circuit 6 can be a phase loss detection circuit that performs a normal determination operation when an overvoltage is generated due to a phase loss and is hard to operate with a high frequency noise. By providing the ferrite core beads as described above, unnecessary operations due to high frequency noise can be reduced. In addition, as compared with the conventional open-phase detection circuit, a simple configuration in which the ferrite core beads are attached to the voltage detection circuit does not require much labor.

FIG. 2 is a circuit diagram showing another embodiment of the present invention.
The power supply circuit of the abnormal voltage monitoring circuit 6 is different from that of the above embodiment, and a diode bridge 11 is provided to perform full-wave rectification. Also in this case, by mounting the ferrite core beads 10 on the voltage detection circuit provided with the resistor R1 as in the above embodiment, the overvoltage due to the open phase appears at both ends of the resistor R2 as usual, but the high frequency noise is greatly attenuated. And unnecessary operation due to high frequency noise can be reduced.

[0010]

As described above in detail, according to the first aspect of the present invention, the shut-off operation is performed with respect to the occurrence of overvoltage due to open phase, but the shut-off operation is not performed with respect to the overvoltage due to high frequency noise. Therefore, there is no fear of unnecessary operation. Further, since the ferrite core beads are merely attached to the voltage detection circuit of the conventional open phase detection circuit, no labor is required.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an AA neutral line open phase protection circuit breaker showing an example of an embodiment of the present invention.

FIG. 2 is a circuit diagram of an AA neutral line open-phase protection circuit breaker showing another embodiment of the present invention.

FIG. 3 is a circuit diagram of a conventional AA neutral line open phase protection circuit breaker.

[Explanation of symbols]

2 ··· Main circuit, 3 ·· trip coil, 4 ·· contact, 5
・ ・ Current transformer, 6 ・ ・ Abnormal voltage monitoring circuit, 7 ・ ・ Voltage detection circuit, 10 ・ ・ Ferrite core beads.

Claims (1)

[Claims] An AA neutral line open phase protection circuit breaker having an open phase detection circuit for shutting off a main circuit and protecting a circuit when a neutral line of a single-phase three-wire circuit is lost. The phase loss detection circuit detects a line voltage, detects a line voltage, detects an abnormal voltage caused by a neutral line phase loss upon receiving the voltage information from the voltage detection circuit, and outputs a main circuit cutoff signal. An AA neutral-phase-loss protective circuit breaker, comprising: an abnormal voltage monitoring circuit that outputs an output; and a ferrite core bead interposed in the voltage detection circuit.