CN1855341A - Leakage circuit cutout - Google Patents

Abstract

[Problem] In order to obtain a highly reliable earth leakage circuit interrupter capable of reliably performing earth leakage tests even when an open phase or slight earth leakage current occurs in an AC circuit. [Proposal] An earth leakage circuit interrupter is provided by using a power supply circuit 5 having power from all phases of the polyphase alternating current circuit 1 and forming a predetermined output voltage. With the oscillation circuit 7c using the power supply circuit 5 as a power supply to oscillate at a frequency different from the AC power frequency applied to the alternating current circuit that can generate the analog leakage current, and for supplying the analog leakage current from the oscillation circuit 7c to the zero phase The circuit in the current transformer 3 performs an on/off operation of the test switch 7 b to set the test circuit 7 .

Description

Leakage Circuit Interrupter

technical field

The present invention relates to a leakage circuit interrupter for preventing accidents caused by expansion of leakage in advance by detecting leakage occurring in a power distribution system to which electric motors or other types of loads are connected, and more particularly to leakage circuit interrupters to which a test circuit is added. streamer improvements.

Background technique

Generally, in order to accurately perform a leakage operation test of a leakage circuit interrupter, various test circuits attached to the leakage circuit interrupter have been made. Figure 3 shows an example of the cutout. FIG. 3 shows a simplified configuration of a conventional leakage circuit interrupter described in Patent Document 1. As shown in FIG.

In Fig. 3, reference numeral 1 represents a three-phase alternating current circuit, reference numeral 2 represents a switch for turning on and off the alternating current circuit 1, and reference numeral 3 represents a zero-phase current transformer, which uses the alternating current circuit 1 as a primary coil to detect the alternating current circuit The leakage current in 1, and the reference numeral 6 represent a fault discrimination circuit, which distinguishes whether there is leakage in the detection current output from the leakage current detection coil 3a of the zero-phase current transformer 3, and is configured to output an indication of leakage when it is detected that the leakage exists signal of. Reference numeral 4 denotes a tripping device operated by the output signal of the leakage discrimination circuit 6, tripping the not-shown switching structure of the switch 2, opening the contacts, and interrupting the AC circuit 1. The two-phase circuit of the three-phase AC circuit 1 supplies power to the leakage identification circuit 6 . Reference numeral 7 denotes a test circuit that performs a leakage trip test and verifies whether the switch 2, the zero-phase current transformer 3, the tripping device 4, and the leakage discrimination circuit 6 are operating normally. The test circuit 7 is equipped with a resistor 7a for adjusting the test current supplied from the two-phase line of the AC circuit 1 to the test coil 3t of the zero-phase current transformer 3, and a push-button test switch 7b for turning on and off the test current. Reference numeral 8 denotes an AC power source connected to the AC circuit 1 , and reference numeral 9 denotes a load connected to the AC circuit 1 .

In the leakage circuit interrupter configured in this manner, when a leakage current occurs in the load or the like and a leakage current flows into the AC circuit 1, the leakage current is detected by the zero-phase circuit transformer 3, and is input from the detection coil 3a to the Leakage identification circuit 6. If the detected leakage current exceeds the preset distinguishing standard, the leakage discrimination circuit 6 generates an output signal indicating the occurrence of leakage, and sends the output signal to the tripping device 4 . The tripping device 4 immediately trips the connected switch structure, disconnects the switching contact of the switch, interrupts the AC circuit 1, and protects the load 9 etc. from leakage.

The leakage interruption operation test of the leakage current circuit breaker is performed by turning on the test switch 7b of the test circuit 7 and supplying a simulated leakage current of a predetermined magnitude to the test coil 3t provided in the zero-phase current transformer 3 via the resistor 7a. Therefore, the same detection output as when leakage current is detected from the leakage current detection coil 3a of the zero-phase current transformer 3 is obtained, and the leakage discrimination circuit 6 discriminates the detection output and outputs a signal indicating occurrence of leakage. The tripping device 4 is activated by this signal and trips and interrupts the switch 2 . With this test, it can be verified whether the zero-phase current transformer 3 , the leakage discrimination circuit 6 and the tripping device 4 are operating normally.

[Patent Document 1] JP-A-2003-45312

Contents of the invention

problem to be solved

In this conventional leakage circuit interrupter, a simulated leakage current for leakage testing is obtained from a two-phase line of alternating current. Therefore, there is a problem that if one of the phases connected to the test circuit that generates the simulated leakage current is open, the leakage test cannot be performed.

Meanwhile, when the leakage discrimination circuit is not operating, that is, when a minute leakage current equal to or smaller than the discrimination standard occurs in the AC circuit, the frequencies of the leakage current and the simulated leakage current are matched with each other. Therefore, there is also a problem that if the two phases are reversed and matched, the leakage current is canceled by the actual leakage current and the magnitude falls below the identification standard, so that the leakage test cannot be performed.

SUMMARY OF THE INVENTION The object of the present invention is to obtain a highly reliable leakage circuit interrupter which can solve these problems and reliably perform a leakage test even if an open phase or a slight leakage current occurs in an AC circuit.

means of solving problems

In order to solve the above problems, a leakage circuit interrupter provided by the present invention includes: a switch for turning on/off the multi-phase AC circuit; a zero-phase current transformer for detecting leakage current in the multi-phase AC circuit; Whether there is a leakage discrimination circuit in the output current of the leakage detection coil of the current transformer; use the output signal of the leakage discrimination circuit indicating that there is a leakage to make the switch trip and disconnect the tripping device; make the multi-phase AC circuit identify the leakage A circuit-powered power circuit, the test circuit configured to supply simulated leakage current to a zero-phase current transformer, wherein the power circuit has circuit power from all phases of the polyphase alternating current circuit, and the test circuit is configured to use the power circuit as A power supply to generate an oscillating circuit of a simulated leakage current, and a test switch to operate an open/closed test switch for supplying a simulated leakage current from the oscillating circuit to a circuit in a zero-phase current transformer.

In this invention, the oscillating circuit of the test circuit is preferably set to an oscillating frequency other than the industrial power frequency (50 or 60 Hz).

Meanwhile, in the present invention, the number of turns of the coil of the zero-phase current transformer is preferably set to be equal to or greater than two turns.

In this invention, since the power supply circuit supplying power to the leakage discrimination circuit is connected to all phases of the polyphase AC circuit that obtains power, the leakage test can be performed even if one phase of the polyphase AC circuit is open. At the same time, since the oscillating circuit of the test circuit is used to form a simulated leakage current having a frequency different from that of the AC circuit, even if the leakage current is not identified as being generated by leakage, the leakage test can be reliably performed without being affected by the leakage current. Influence.

Description of drawings

[Fig. 1] shows the block diagram of leakage circuit interrupter of the present invention;

[Fig. 2] is a circuit diagram showing in detail the power supply circuit and test circuit of the leakage circuit interrupter of the present invention; and

[ Fig. 3 ] shows a block diagram of a conventional earth leakage circuit interrupter.

Label description

10 leakage circuit interrupter

1 AC circuit

1A power connector

1B load connection terminal

2 switches

3 zero-phase current transformer

3a Leakage current detection coil

3t test coil

4 trip device

5 power circuit

51 three-phase full-wave rectifier circuit

52 constant voltage circuit

6 leakage identification circuit

7 Test circuit

7a adjustment resistor

7b Test switch

7c oscillator circuit

specific embodiment

The invention will be described with respect to the embodiments shown in the drawings.

Example

FIG. 1 is a block diagram illustrating an embodiment of the present invention.

In FIG. 1, reference numeral 10 denotes an earth leakage circuit interrupter. Usually, all these constituent elements are densely formed and housed in a molded case made of insulating resin. Leakage circuit interrupter 10 includes: a three-phase alternating current circuit 1 connected to power supply connection end 1A and load connection end 1B; a switch 2 for opening/closing alternating current circuit 1; And detect the zero-phase current transformer 3 that flows into the leakage current in the AC circuit 1; Distinguish whether there is a leakage discrimination circuit 6 that leakage current occurs by monitoring the detection current of the leakage current detection coil 3a of the zero-phase current transformer 3; The output signal of the leakage identification circuit 6 with leakage occurs to trip the switching structure of the switch 2 and to interrupt the tripping device 4 of the AC circuit 1 . The leakage circuit interrupter 10 also includes a leakage test circuit 7 for verifying that the switch 2, the zero-phase current transformer 3, the tripping device 4 and the leakage discrimination circuit 6 are operating normally, and supplies power to the leakage discrimination circuit 6 and the test circuit 7 The power circuit 5. The output of the test circuit 7 is electromagnetically connected to the zero-phase current transformer 3 via the test coil 3 placed in the zero-phase current transformer 3 . Furthermore, an AC power source 8 is connected to the power supply connection terminal 1A, and a load 9 is connected to the load terminal 1B.

Details shown in Figure 2, the power supply circuit 5 is configured as a three-phase full-wave rectification circuit 51, which rectifies the AC power supplied by the three phases from the AC circuit 1, and converts it into a DC power supply; there is also a constant The voltage circuit 52 controls the output voltage of the rectification circuit 51 to a predetermined voltage. A power supply circuit 5 as a power supply is added to the leakage discrimination circuit 6 and the test circuit 7.

The test circuit 7 includes a push-button test switch 7b that is operated at the time of the leakage test, an oscillation circuit 7 that generates an oscillation current of a predetermined frequency, and an adjustment resistor 7a that adjusts the test current. The test switch 7 b , the oscillation circuit 7 c , and the adjustment resistor 7 a of the test circuit 7 are connected in series to the power supply circuit 5 through the test coil 3 t of the zero-phase current transformer 3 .

The oscillation circuit 7c is configured by a NAND gate Q1, NOT gates Q2 and Q3, resistors R1 and R2, and a capacitor C1. The oscillation circuit 7c is configured such that when the test switch 7b is switched on, the Q1 output of the NAND gate becomes L level, and at a frequency approximated by the following expression made from the values of the capacitor C1 and the resistor R1 f oscillates.

f=1/(2.2·R1·C1)(Hz)

Since the size of the test current It supplied from the oscillation circuit 7c to the test coil 3t of the zero-phase current transformer 3 is determined by the output voltage V1 of the resistor 7a and the power supply 5, it can be set by adjusting the size of the resistor 7a. is the predetermined value.

In the test circuit 7, when the test switch 7b is switched on, the oscillation circuit 7c oscillates, and a predetermined test current (analog leakage current) oscillating at a frequency f is supplied to the test coil 3t of the zero-phase current transformer 3 . Therefore, the detection current corresponding to the test current It is obtained from the leakage current detection coil 3 a of the zero-phase current transformer 3 and applied to the leakage discrimination circuit 6 . Because the magnitude of the selected test current It exceeds the preset determination standard, the leakage discrimination circuit 6 immediately sends a signal indicating the occurrence of leakage to the tripping device 4 . Thus, in the event of normal operation, the not-shown tripping structure of the switch 2 trips, the switching contacts of the switch 2 are opened, and the alternating current circuit 1 is interrupted. Therefore, it can be verified that the operation is proceeding normally, and the test ends.

In this way, in the leakage circuit interrupter of the present invention, the three-phase full-wave rectification circuit 51 is placed in the power supply circuit 5, and the voltages of all phases of the three-phase AC circuit 1 are rectified by the rectification circuit 51, and obtained the DC voltage. Therefore, even if one of the phases of the three-phase AC circuit 1 is an open phase, a DC voltage can still be obtained. In addition, because the output voltage of the power supply circuit 5 is maintained at the constant of V1 by the constant voltage circuit 52, even if the input voltage of the power supply circuit 5 changes due to an open phase, a predetermined test current can still be provided to the zero-phase current transformer 3. Test coil 3t. Therefore, even if an open phase occurs in the AC circuit 1, the leakage test can still be performed.

When the leakage test is to be performed, it is conceivable that a leakage current which does not reach the determined standard of the leakage discrimination circuit 6 occurs in the leakage circuit interrupter. In this case, if the frequency of the test current (simulated leakage current) generated by the test circuit 7 and the actual leakage current are the same, and their phases are reversed and matched, even if the leakage circuit interrupter is normal, eventually The test current is offset by the leakage current, the signal indicating the occurrence of leakage will not be output from the leakage discrimination circuit 6, and the result of this test is an operational failure.

Therefore, in the present invention, since the frequency of the commercial power supply system is 50 or 60 Hz, the oscillation frequency f of the oscillation circuit 7c of the test circuit 7 can be set to 40 or 70 Hz which is different from 50 or 60 Hz. When the oscillation frequency f of the oscillating circuit 7c is set differently from the commercial power frequency in this way, the test current (simulated leakage current) will not be offset by the actual minute leakage current when the leakage test is performed. Therefore, the test can be accurately performed, and the reliability of the leakage test can also be improved.

At the same time, because the leakage identification standard of the leakage circuit interrupter is set at about 70% of the leakage induction current, when the induction current is set at 30mA, the leakage identification standard of the leakage identification circuit 6 is set at about 21mA. Therefore, when the test coil 3t of the zero-phase current transformer 3 has one turn, it is necessary to set the test current (simulated leakage current) from the test circuit 7 to at least 21 mA. Because the power supply circuit 5 that bears this current will have problems such as heating caused by the load current, the lower the power supply current, the better. For this reason, in the present invention, when allowable leeway occurs in the coil space of the zero-phase current transformer 3 , the test coil 3 t has a plurality (n) of turns equal to or greater than two turns. Therefore, since the test current It supplied to the test coil can be reduced to 1/n of the current required for one turn, the output current of the power supply circuit 5 can be kept low, and the power consumption of the power supply circuit 5 can be reduced.

Claims (3)

1. leakage circuit cutout comprises:

The switch of cut-off/close many phase alternating current circuit;

Detect the Zero-phase current transformer of the leakage current of described many phase alternating current circuit;

In the output current of the leakage current magnetic test coil of described Zero-phase current transformer, detect the electric leakage discriminator circuit that whether has electric leakage to occur;

With showing that the output signal that the described electric leakage discriminator circuit that electric leakage occurs being arranged makes described switch trip and the tripping operation device that disconnects;

The power circuit that described many phase alternating current circuit is powered to described electric leakage discriminator circuit; And

Be configured to the simulation leakage current is offered the test circuit of the test coil of described Zero-phase current transformer,

Wherein

Described power circuit possesses the electric energy of the circuit that all phases that come from described many phase alternating current circuit are arranged, and

Being configured to of described test circuit: described power circuit is used as the oscillating circuit of power supply with generation simulation leakage current, and the circuit that described simulation leakage current is provided to from described oscillating circuit in the described Zero-phase current transformer is carried out the Test Switchboard that cut-off/close is operated.

2. leakage circuit cutout as claimed in claim 1 is characterized in that, the oscillating circuit of described test circuit is set to the frequency of oscillation outside the commercial frequency (50 or 60Hz).

3. leakage circuit cutout as claimed in claim 1 or 2 is characterized in that the number of turn of the test coil of described Zero-phase current transformer is equal to or greater than two circles.

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