CN105990818A - Leakage circuit breaker - Google Patents

Abstract

The present invention provides an earth leakage circuit breaker capable of preventing failure of a built-in power supply circuit by shutting off the earth leakage circuit breaker even when an overvoltage is continuously applied to an AC circuit in a withstand voltage test or the like. Equipped with: a rectification circuit that converts the AC voltage supplied from the AC circuit (1) into a DC voltage; a second constant voltage circuit (53) that steps down the output voltage of the rectification circuit; a second Zener diode (54) , it detects the overvoltage according to the output voltage of the rectifier circuit; the second resistor (55), when the second Zener diode (54) detects the overvoltage, makes the output voltage of the second constant voltage circuit (53) Boost; the 3rd zener diode (56), when the output voltage of the 2nd constant voltage circuit (53) reaches the 1st specified value, it absorbs the surge current; It detects that the output voltage of the constant voltage circuit (53) has reached a predetermined value, and drives a tripping device.

Description

Leakage circuit breakers

technical field

The present invention relates to an earth leakage circuit breaker which disconnects a circuit when the leakage current of the circuit becomes greater than or equal to a predetermined value, and in particular relates to an operating power supply of the earth leakage circuit breaker.

Background technique

The power supply circuit built into this leakage circuit breaker converts the AC voltage (for example, AC100V) supplied from the AC circuit into a DC voltage by a rectification circuit, and then converts the rectified DC voltage to a lower voltage by a step-down circuit. A DC voltage (for example, DC24V) is supplied as a drive power supply to the leakage detection circuit and the tripping device.

In such a power supply circuit, when a surge voltage (surge voltage) is induced in the AC circuit due to lightning strike, arcing ground, etc., it is necessary to protect the leakage detection circuit and the tripping device from the surge voltage.

As this protection unit, there is known a power supply circuit (for example, refer to Patent Document 1), which is provided with: a voltage detection circuit which detects a surge voltage from the output voltage of a rectification circuit; When a surge voltage is detected, the output voltage of the step-down circuit is boosted; and a current sink circuit is provided on the output side of the step-down circuit and absorbs the surge current ( surge current).

Patent Document 1: Japanese Unexamined Patent Publication No. 2009-95125

In the power supply circuit of the existing earth leakage circuit breaker, when a surge voltage is induced, the output voltage of the step-down circuit is boosted by the step-up circuit, and the current is turned on when the output voltage of the step-down circuit reaches a specified value. It is clamped at a constant voltage by passing through a current sink circuit that absorbs a surge current, and prevents components constituting the leakage detection circuit from malfunctioning due to overvoltage. It is conceivable that the pulse width of the surge voltage is usually a few mseconds at most. Of course, there is a limit to the energy that can pass through the step-down circuit and the current sink circuit. Therefore, when an overvoltage is continuously applied, the limit is exceeded, causing failure of the step-down circuit and the current sink circuit.

It may be considered that, as the possibility of the above-mentioned continuous overvoltage application, in a control panel equipped with an earth leakage circuit breaker, etc., in order to check the phases of the AC circuit including the earth leakage circuit breaker, and the AC circuit and the earth (earth) ( ground (earth)) and perform a withstand voltage test (for example, 2000V for 1 minute).

In general, when an electronic circuit is connected to the circuit such as an earth leakage circuit breaker, it is prohibited to perform a withstand voltage test between phases, and the withstand voltage test is performed only between the AC circuit and the earth (earth). Therefore, there is no situation where an overvoltage is applied between the phases. However, as shown in Fig. 7, if a load circuit is connected to an earth leakage circuit breaker, there may be a device (for example, a capacitor for surge absorption, a noise filter (Noise filter), etc.) Overvoltage is accidentally continuously applied between phases due to ground static capacitance, and as a result, the power supply circuit of the earth leakage circuit breaker fails.

Contents of the invention

This invention was made in order to solve the above-mentioned subject, and it aims at obtaining the earth leakage circuit breaker which has a protection function against the application of continuous overvoltage.

The leakage circuit breaker of the present invention is equipped with: a switch contact, which makes the circuit on and off; a leakage current detector, which detects the leakage current of the circuit; a leakage detection circuit, which is connected to the leakage current detector, and detects the The detection signal of the device detects the leakage; the tripping device is driven by the leakage detection circuit to separate the open and close contacts; and the power supply circuit is composed of a step-down circuit, a voltage detection circuit and a boost circuit. The voltage circuit steps down the power supplied from the circuit to a constant voltage power, the voltage detection circuit detects an overvoltage from the circuit, and the boost circuit increases the output voltage of the step-down circuit when the voltage detection circuit detects an overvoltage. a voltage boost; a current absorbing circuit provided on the output side of the power supply circuit, which absorbs a surge current when the output voltage of the power supply circuit reaches a first predetermined value; and an overvoltage detection circuit provided on the output side of the power supply circuit, in the power supply The trip device is driven when the output voltage of the circuit exceeds a second predetermined value higher than the rated voltage of the power supply circuit and lower than the first predetermined value.

The effect of the invention

Since the present invention separates the switching contacts by the overvoltage detection circuit that detects the continuous overvoltage, it is possible to prevent failure of the earth leakage circuit breaker caused by the application of the continuous overvoltage.

Description of drawings

FIG. 1 is a circuit diagram showing an earth leakage circuit breaker using a power supply circuit according to Embodiment 1 of the present invention.

FIG. 2 is a circuit diagram showing an example of details of the integrating circuit shown in FIG. 1 .

3 is a circuit diagram showing an earth leakage circuit breaker using the power supply circuit according to Embodiment 2 of the present invention.

FIG. 4 is a block diagram showing an example of details of the leakage detection circuit shown in FIG. 3 .

5 is a circuit diagram showing a DC earth leakage circuit breaker using the power supply circuit according to Embodiment 3 of the present invention.

6 is a circuit diagram showing a DC earth leakage circuit breaker using the power supply circuit according to Embodiment 4 of the present invention.

It is explanatory drawing for demonstrating the subject of this invention using the circuit diagram at the time of mounting the conventional earth leakage circuit breaker in the control panel.

Explanation of labels

1 AC circuit, 2 Switching contacts, 3 Zero-phase sequence converter, 4 Trip device, 4a Trip coil, 4b Trip mechanism, 5 Power supply circuit, 51 Current limiting resistor, 52 Rectifier circuit, 53 The second constant voltage circuit, 53a field effect transistor (FET), 53b first zener diode, 53c first resistor, 54 second zener diode, 55 second resistor, 56 third zener diode, 6 leakage detection circuit, 7 first constant voltage circuit , 8 switch unit, 9 overvoltage detection circuit, 9a 4th Zener diode, 9b integral circuit, 9c comparison circuit, 100 leakage circuit breaker.

detailed description

Implementation mode 1.

1 is a circuit diagram showing a configuration of an earth leakage circuit breaker using a power supply circuit according to Embodiment 1 of the present invention, and FIG. 2 is a circuit diagram showing an example of details of an integrating circuit shown in FIG. 1 .

In FIG. 1 , the leakage circuit breaker 100 has: a switch contact 2, which makes the AC circuit 1 on and off; a leakage detection circuit 6, which is connected to the zero-phase sequence converter 3 inserted in the AC circuit 1, that is, leakage current detection The device is connected, and the leakage is detected based on the detection signal of the zero-phase-sequence converter 3; the tripping device 4 has a tripping coil 4a and a tripping mechanism 4b, wherein the tripping coil 4a is based on the output signal of the leakage detection circuit 6 , generates an electromotive force via a switching unit 8, and the tripping mechanism 4b separates and drives the switching contacts 2 when the tripping coil (trip coil) 4a is excited; Both sides of the device 4 supply power.

The power supply circuit 5 converts the AC voltage input from the AC circuit 1 into a predetermined DC voltage to supply an exciting current to the trip coil 4a, and converts it into a predetermined voltage lower than the output voltage of the power supply circuit 5 by the first constant voltage circuit 7, and supplies it to the trip coil 4a. Leakage detection circuit 6 supply.

Hereinafter, details of the power supply circuit 5 will be described.

The power supply circuit 5 is connected to the AC circuit 1 , and a rectifier circuit 52 , which is a rectifier circuit, which is a full diode bridge circuit, is connected to a subsequent stage of the current limiter circuit 51 , which limits current. The output side of this rectifier circuit 52 is connected with the 2nd constant voltage circuit 53 that makes its output voltage step-down, namely step-down circuit, and this 2nd constant voltage circuit 53 is made up of following parts: field effect transistor (field effect transistor) (hereinafter referred to as , denoted as FET) 53a, its drain (drain) is connected to the positive output side of the rectifier circuit 52; Between the output negative electrode side; and the first resistor 53c (with a resistance value of several hundred k to several MΩ) connected between the drain and gate of the FET 53a that supplies Zener current to the first Zener diode 53b.

On the first resistor 53c of the second constant voltage circuit 53, a second Zener diode 54 (Zener voltage>output voltage of the rectifier circuit 52), that is, a voltage detection circuit, is connected in parallel. The output voltage of the rectification circuit 52 detects the surge voltage. Between the gate of the FET 53a and the output negative side of the rectifier circuit 52, a second resistor 55 (with a resistance value of about tens to hundreds of Ω) connected in series with the first Zener diode 53b, that is, a booster circuit, is connected. When the second Zener diode 54 detects a surge voltage, the output voltage of the second constant voltage circuit 53 is raised by the second resistor 55 . Between the source of the FET 53a and the output negative side of the rectifier circuit 52, a third Zener diode 56, that is, a current sink circuit, is connected, and the output voltage of the second constant voltage circuit 53 reaches the Zener of the third Zener diode 56. When the voltage is the first predetermined value, the surge current is absorbed by the third Zener diode 56 .

In addition, an overvoltage detection circuit 9 is provided at the output terminal of the power supply circuit 5, and the overvoltage detection circuit 9 is connected in parallel with the third Zener diode 56. If the overvoltage is continuously input from the AC circuit 1 until a predetermined time is reached, the tripping circuit will be driven. device 4.

The overvoltage detection circuit 9 is made up of the following parts: the 4th Zener diode 9a (for example, Zener voltage is about 23V), its cathode is connected to the cathode of the 3rd Zener diode 56, and the output of the 2nd constant voltage circuit 53 When the voltage exceeds the second predetermined value, it is turned on; the input terminal of the integrating circuit 9b is connected to the anode of the 4th Zener diode 9a and the anode of the 3rd Zener diode 56; When the output exceeds a predetermined value, that is, the output voltage of the power supply circuit 5 reaches the second predetermined voltage and the time for the output voltage of the power supply circuit 5 to reach the second predetermined voltage exceeds a predetermined time (for example, 20msec), it is detected and the switch unit 8 is driven.

As shown in Figure 2, the integrating circuit 9b is composed of the following components: a resistor 9b1 (with a resistance value of about 1kΩ to 10kΩ), one end of which is connected to the anode of the fourth Zener diode 9a; a capacitor 9b2 (with a capacity of 0.1μF to several μF left and right), one end of which is connected to the other end of the resistor 9b1, and the other end of the capacitor 9b2 is connected to the anode of the third zener diode 56; They are connected in parallel, and both ends are connected to the comparison circuit 9c. Here, the resistor 9b3 is a part for discharging the charge of the capacitor 9b2 when the capacitor 9b2 is turned off.

Furthermore, the trip device 4 and the first constant voltage circuit 7 are also connected to the output end of the power supply circuit 5 .

In addition, the first Zener diode 53b is arranged on the gate side of the FET 53a, and the second resistor 55 is arranged on the output negative side of the rectifier circuit 52, but the second resistor 55 may be arranged on the gate side of the FET 53a, and the rectifier circuit 52 is provided with a first Zener diode 53b on the negative output side.

The operation will be described below.

In a normal state, when an AC voltage of approximately AC100V to 400V is supplied from the AC circuit 1 , the AC current Ia flows through the current limiting resistor 51 and is converted into a DC voltage Vb by the rectifier circuit 52 . The current Ic flows through the first Zener diode 53b and the second resistor 55 through the first resistor 53c by the current Ib output from the rectifier circuit 52 . On the other hand, since the Zener voltage of the second Zener diode 54 is higher than the output voltage Vb of the rectifier circuit 52, the second Zener diode 54 is not conducted, and the current does not flow to the first Zener diode 54 through the second Zener diode 54. Zener diode 53b and 2 resistors 55 flow.

At this time, the resistance value of the first resistor 53c is as large as hundreds of k to several MΩ, while the resistance value of the second resistor 55 is as small as tens to hundreds of Ω, so the current Ic flowing through the second resistor 55 is basically The upper limit is determined by the first resistor 53c, and is, for example, as small as tens of μA to several hundreds of μA. Therefore, the voltage drop of the second resistor 55 can be basically ignored. Therefore, if the voltage (the gate voltage of the FET 53a) applied to the second resistor 55 and the first Zener diode 53b is Vc, Vc≈(the Zener voltage of the first Zener diode 53b) .

In addition, the output voltage Vd of the second constant voltage circuit 53 is Vd=Vc-(the conduction voltage of the FET 53a), but as described above, Vc≈(the Zener voltage of the first Zener diode 53b), therefore, becomes Vd≈(Zener voltage of the first Zener diode 53 b )−(ON voltage of the FET 53 a ), which is the rated voltage of the power supply circuit 5 .

Here, if the ON voltage of the FET 53a is about 3V and the Zener voltage of the first Zener diode 53b is about 24V, the output voltage Vd of the second constant voltage circuit 53 becomes about Vd≈24V−3V=21V.

In addition, if the Zener voltage of the third Zener diode 56 is about 24V, the voltage Vd applied to the third Zener diode 56 is about 21V and does not exceed the Zener voltage of the third Zener diode 56 . Accordingly, the third Zener diode 56 is not turned on, and the current Id does not flow.

Also, if the second predetermined value of the Zener voltage of the fourth Zener diode 9a is about 23V, the voltage Vd applied to the fourth Zener diode 9a is about 21V, so the fourth Zener diode 9a is not turned on either. .

As a result, about DC 21V is supplied from the output terminal of the power supply circuit 5 to the trip coil 4a and the first constant voltage circuit 7, and the first constant voltage circuit 7 steps down the output voltage of the power supply circuit 5 to supply a predetermined voltage to the leakage detection circuit 6. A constant voltage (for example, DC 5V).

In such a power supply state, when a leakage occurs in the AC circuit 1, a signal is generated in the output of the zero-phase-sequence converter 3. If the output signal of the zero-phase-sequence converter 3 is discriminated by the leakage detection circuit 6 If the level exceeds a predetermined reference value, an earth leakage trip signal is output to the switch unit 8 . The switch unit 8 is turned on by this output, and an excitation current flows from the power supply circuit 5 to the trip coil 4 a via the switch unit 8 , and the trip mechanism 4 b operates, thereby opening the switch contact 2 .

In addition, the "first predetermined value" described in the claims refers to the Zener voltage of the above-mentioned third Zener diode 56, and similarly, the "second predetermined value" described in the claims refers to the above-mentioned Zener voltage of the fourth Zener diode 9a.

Next, a case where a momentary surge voltage is superimposed on the AC voltage in the AC circuit will be described.

If a surge voltage of several kV is superimposed on the AC voltage, the voltage applied to the series circuit of the second Zener diode 54 and the first Zener diode 53b exceeds that of the second Zener diode 54 and the first Zener diode. 53b Zener voltage total value, so the second Zener diode 54 is also turned on.

At this time, the current Ic flowing through the second resistor 55 becomes several tens of mA compared with the usual tens of μA to several hundreds of μA, and a voltage drop occurs across the second resistor 55, and the current Ic is applied between the second resistor 55 and the second resistor 55. The voltage Vc across the first Zener diode 53b rises. For example, if the resistance value of the second resistor 55 is about 100 ohms and the current Ic is about 40mA, the voltage drop across the second resistor 55 is about 4V, and the voltage applied to the second resistor 55 and the first Zener diode 53b Vc becomes about Vc=24V+4V=28V. The output voltage Vd of the second constant voltage circuit 53 increases to about 25V by adding about 4V, which is the voltage drop amount of the second resistor 55, to the normal rated voltage of about 21V. However, since the voltage of about 25V exceeds the Zener voltage (about 24V) of the third Zener diode 56, the third Zener diode 56 is turned on, and the output voltage Vd of the second constant voltage circuit 53 is suppressed to the third Zener voltage. The Zener voltage of the nanodiode 56 (about 24V).

In addition, at this time, the output voltage Vd of the second constant voltage circuit 53 exceeds the Zener voltage 23V of the fourth Zener diode 9a, but the fourth Zener diode 9a is connected in series with the resistor 91b, and the resistor 91b shares the voltage and limits the current. The voltage of the power supply circuit 5 is maintained at the Zener voltage (24V) of the third Zener diode 56 . As a result, the fourth Zener diode 9a is kept on, and charging of the capacitor 9b2 via the resistor 9b1 is started in the integrating circuit 9b. However, when an instantaneous surge voltage is generated, the time for the surge voltage to be superimposed on the AC voltage in the AC circuit 1 is very short (for example, about 1 to 2 msec). Therefore, the voltage of the capacitor 9b2 does not rise sufficiently, that is, since the time during which the output voltage of the power supply circuit 5 exceeds the second predetermined voltage is shorter than the predetermined time, the output of the comparison circuit 9c is not turned on, and the earth leakage circuit breaker 100 does not perform the breaking operation. .

In this way, the earth leakage circuit breaker 100 does not perform a breaking operation, and the output voltage of the power supply circuit 5 is suppressed to the Zener voltage of the third Zener diode 56, thereby protecting the leakage detection circuit 6 and the trip device 4 from surge voltage.

Next, a case where a continuous overvoltage is superimposed on an AC circuit will be described.

If an overvoltage of several kV is continuously applied to the AC circuit 1, the voltage applied to the series circuit of the second Zener diode 54 and the first Zener diode 53b exceeds that of the second Zener diode 54 and the first Zener diode. Since the sum of the Zener voltages of the diodes 53b is equal, the second Zener diode 54 is also turned on.

At this time, the current Ic flowing through the second resistor 55 becomes several tens of mA compared with the usual tens of μA to several hundreds of μA, and a voltage drop occurs across the second resistor 55, and a voltage drop is applied to the second resistor 55. and the voltage Vc across the first Zener diode 53b rises. For example, if the resistance value of the second resistor 55 is about 100 ohms and the current Ic is about 40mA, the voltage drop across the second resistor 55 is about 4V, and the voltage applied to the second resistor 55 and the first Zener diode 53b Vc becomes about Vc=24V+4V=28V. The output voltage Vd of the second constant voltage circuit 53 increases to about 25V by adding about 4V, which is the voltage drop amount of the second resistor 55, to the normal rated voltage of about 21V. However, since the voltage of about 25V exceeds the Zener voltage (about 24V) of the third Zener diode 56, the third Zener diode 56 is turned on, and the output voltage Vd of the second constant voltage circuit 53 is suppressed to the third Zener voltage. The Zener voltage of the nanodiode 56 (about 24V).

At this time, the output voltage Vd of the second constant voltage circuit 53 exceeds the zener voltage 23V of the fourth zener diode 9a, so the fourth zener diode 9a is also turned on, and in the integrating circuit 9b, the capacitor 9b2 is activated via the resistor 9b1. Charge. In the case of continuous overvoltage, the voltage of the capacitor 9b2 rises sufficiently, and the output voltage of the power supply circuit 5 exceeds the second predetermined value for a predetermined time, and the output of the comparison circuit 9c is turned on and output to the switch unit 8 . The switch unit 8 is also turned on by the output of the comparator circuit 9c, and an exciting current flows from the power supply circuit 5 to the trip coil 4a via the switch unit 8, and the trip mechanism 4b operates, thereby opening the switch contact 2. And, since the switching contact 2 is opened, the power supply to the power supply circuit 5 is stopped.

According to this embodiment, a power supply circuit 5 is provided, which is composed of a second constant voltage circuit 53, a second Zener diode 54, and a second resistor 55, wherein the second constant voltage circuit 53 controls the power supplied from the AC circuit 1 to The second Zener diode 54 detects the overvoltage according to the output voltage of the rectifier circuit 52, and the second resistor 55 turns the second constant voltage when the second Zener diode 54 detects the overvoltage. boosting the output voltage of voltage circuit 53; the third zener diode 56, which is arranged on the output side of the power supply circuit 5, absorbs the surge current when the output voltage of power supply circuit 5 reaches the first predetermined value; and an overvoltage detection circuit 9. It is installed on the output side of the power circuit 5, and drives the tripping device 4 when the output voltage of the power circuit 5 exceeds a second predetermined value, wherein the second predetermined value is higher than the rated voltage of the power circuit 5 and higher than the first The predetermined value is low, and since the above-mentioned components are included, even when an overvoltage is continuously applied to the AC circuit 1 in a withstand voltage test or the like, the earth leakage circuit breaker 100 can be disconnected to protect the earth leakage circuit breaker 100 from failure.

In addition, since the overvoltage detection circuit 9 includes the integrating circuit 9b, and drives the tripping device when the time for the output voltage of the power supply circuit 5 to reach the second predetermined value exceeds a predetermined time, the overvoltage detection circuit 9 will not be damaged due to an instantaneous surge voltage. The second predetermined value is higher than the rated voltage of the power supply circuit 5 and lower than the first predetermined value, thereby preventing unnecessary tripping by not operating under an overvoltage.

In addition, since a common leakage detection IC (Integrated Circuit) used in the leakage detection circuit 6 has a built-in comparator circuit 9c, the overvoltage detection circuit 9 can use a fourth Zener diode 9a, and a circuit composed of resistors 9b1, 9b3, and a capacitor 9b2. An integrating circuit 9b is constituted. Therefore, the earth leakage circuit breaker 100 can be protected at low cost from a failure caused by continuous application of overvoltage to the AC circuit 1 due to a withstand voltage test or the like.

In addition, if an overvoltage is applied to the power supply circuit 5, its output voltage rises, so the overvoltage detection circuit 9 can be provided on the output side of the power supply circuit 5, that is, on the low voltage side, and the components used can be miniaturized, and the earth leakage circuit breaker can be realized. miniaturization.

Implementation mode 2.

3 is a circuit diagram showing the configuration of an earth leakage circuit breaker using a power supply circuit according to Embodiment 2 of the present invention, and FIG. 4 is a block diagram showing an example of details of the leakage detection circuit shown in FIG. 3 .

The leakage circuit breaker 101 of this embodiment is provided with the leakage test circuit 10 including the overvoltage detection circuit instead of the overvoltage detection circuit 9 of the first embodiment, and achieves various effects similar to those of the first embodiment described above.

In Fig. 3, the leakage test circuit 10 of the earth leakage circuit breaker 101 is made up of the following parts: the 4th Zener diode 9a, its cathode is connected with the cathode of the 3rd Zener diode 56; The output of voltage circuit 7 is connected, and the other end is connected with the anode of the 4th Zener diode 9a; The test current generation circuit 10b, its input is connected with the anode of the 4th Zener diode 9a and the other end of test switch 10a; Resistor 10c, its One end is connected to the cathode of the fourth Zener diode 9a; and the base of the transistor 10d is connected to the output of the test current generating circuit 10b, and the collector is connected to the other end of the resistor 10c.

Moreover, the output of the leakage test circuit 10, that is, the emitter of the transistor 10d, is connected to one end of the test winding 11, and the other end of the test winding 11 passes through the zero-phase-sequence converter 3, and then is connected to the negative output side of the rectifier circuit 52.

The leakage test function for checking that the leakage circuit breaker is normal is constituted by the leakage test circuit 10 and the test winding 11 .

The details of the leakage detection circuit 6 will be described with reference to FIG. 4 . In Fig. 4, leakage detection circuit 6 is made up of the following parts: filter 6a, it is connected with zero-phase-sequence converter 3, the output signal from zero-phase-sequence converter 3 will be consistent with the power frequency of AC circuit 1 Higher high-frequency components are removed; the level determiner 6b, which is input to the output signal of the filter 6a, determines the output level of the output signal of the filter 6a; the signal amplitude discriminator 6c, which determines the level The time range of the output signal of the device 6b is discriminated; the counter 6d, if it has carried out the specified number of counts to the output signal of the signal range discriminator 6c, then output the pulse signal; The output signal resets the counter 6d after a predetermined time, and the flip-flop circuit 6f receives the pulse signal of the counter 6d to drive the switching element 8 .

The other configurations and operations are the same as those in Embodiment 1, and therefore description thereof will be omitted.

The operation will be described below.

In order to perform a normal leakage test operation, when the test switch 10a is turned on, power is supplied from the first constant voltage circuit 7 to the test current generating circuit 10b, and the transistor 10d is switched on and off to flow to the test winding 11 through the resistor 10c. Test current, ie leakage analog current. If the test current flows through the test winding 11 , a signal is generated at the output of the zero-phase-sequence converter 3 , and is output to the switch unit 8 if it is judged as leakage by the leakage detection circuit 6 . The switch unit 8 is turned on by this output, and an exciting current flows from the power supply circuit 5 to the trip coil 4a via the switch unit 8, and the trip mechanism 4b operates to open the switch contact 2 and shut off the earth leakage circuit breaker 101.

A case where a momentary surge voltage is superimposed on an AC voltage in an AC circuit will be described.

If a surge voltage of several kV is superimposed on the AC voltage, the voltage applied to the series circuit of the second Zener diode 54 and the first Zener diode 53b exceeds that of the second Zener diode 54 and the first Zener diode 53b. Therefore, the second Zener diode 54 is also turned on.

At this time, the current Ic flowing through the second resistor 55 becomes several tens of mA compared with the usual tens of μA to several hundreds of μA, and a voltage drop occurs across the second resistor 55, and the current Ic is applied between the second resistor 55 and the second resistor 55. The voltage Vc across the first Zener diode 53b rises. For example, if the resistance value of the second resistor 55 is about 100 ohms and the current Ic is about 40mA, the voltage drop across the second resistor 55 is about 4V, and the voltage applied to the second resistor 55 and the first Zener diode 53b Vc becomes about Vc=24V+4V=28V. The output voltage Vd of the second constant voltage circuit 53 increases to about 25V by adding about 4V, which is the voltage drop amount of the second resistor 55, to the normal rated voltage of about 21V. However, since the voltage of about 25V exceeds the Zener voltage (about 24V) of the third Zener diode 56, the third Zener diode 56 is turned on, and the output voltage Vd of the second constant voltage circuit 53 is suppressed to the third Zener voltage. The Zener voltage of the nanodiode 56 (about 24V).

In addition, at this time, the output voltage Vd of the second constant voltage circuit 53 exceeds the Zener voltage 23V of the fourth Zener diode 9a, so the fourth Zener diode 9a is turned on, and power is supplied to the test current generating circuit 10b, so that the transistor 10d switch, so that the test current flows in the test winding 11. If a test current flows through the test winding 11, a signal is generated at the output of the zero-phase-sequence converter 3, but as shown in FIG. The frequency component is input to the level determiner 6b to determine its level. If the leakage signal is greater than or equal to the prescribed level, then the signal amplitude discriminator 6c then discriminates the time amplitude of the signal. If the time width of the leakage signal is also greater than or equal to the determination value, the counter 6d is further used to count the repetitions of the leakage signal at a substantially commercial frequency until the timer 6e resets the counter 6d.

However, in the case of the surge voltage, the time for the surge voltage to be superimposed on the AC voltage in the AC circuit is very short (for example, about 1 to 2 msec). Therefore, even if the leakage signal caused by the surge voltage is input to the signal amplitude discriminator 6c, the signal amplitude will not be output from the signal amplitude discriminator 6c, or even if it is output from the signal amplitude discriminator 6c, it will be displayed on the counter 6d does not count continuously, and pulses cannot be output from the counter 6d. That is, since the time during which the output voltage of the power supply circuit 5 exceeds the second predetermined value is shorter than the predetermined time, the output of the flip-flop circuit 6f is not turned on, and the earth leakage circuit breaker 101 does not perform the breaking operation.

In this way, the earth leakage circuit breaker 101 does not perform an interruption operation, and the output voltage Vd of the second constant voltage circuit 53 is limited to the Zener voltage of the third Zener diode 56, thereby protecting the leakage detection circuit 6 and the tripping device 4 from surge voltage. influences.

Next, a case where a continuous overvoltage is superimposed on the AC circuit 1 will be described.

If an overvoltage of several kV is continuously applied to the AC circuit, as in Embodiment 1, the applied voltage to the series circuit of the second Zener diode 54 and the first Zener diode 53b exceeds that of the second Zener diode. 54 and the Zener voltage sum of the first Zener diode 53b, the second Zener diode 54 is also turned on.

At this time, the current Ic flowing through the second resistor 55 becomes several tens of mA compared with the usual tens of μA to several hundreds of μA, and a voltage drop occurs across the second resistor 55, and the current Ic is applied between the second resistor 55 and the second resistor 55. The voltage Vc across the first Zener diode 53b rises. For example, if the resistance value of the second resistor 55 is about 100 ohms and the current Ic is about 40mA, the voltage drop across the second resistor 55 is about 4V, and the voltage applied to the second resistor 55 and the first Zener diode 53b Vc becomes about Vc=24V+4V=28V. The output voltage Vd of the second constant voltage circuit 53 increases to about 25V by adding about 4V, which is the voltage drop amount of the second resistor 55, to the normal voltage of about 21V. However, since the voltage of about 25V exceeds the Zener voltage (about 24V) of the third Zener diode 56, the third Zener diode 56 is turned on, and the output voltage Vd of the second constant voltage circuit 53 is suppressed to the third Zener voltage. The Zener voltage of the nanodiode 56 (about 24V).

In addition, since the output voltage Vd of the second constant voltage circuit 53 exceeds the Zener voltage 23V of the fourth Zener diode 9a, the fourth Zener diode 9a is turned on, and power is supplied to the test current generating circuit 10b. A test current is passed through the test winding 11 . If the simulated leakage current flows through the test winding 11, a signal is generated in the output of the zero-phase-sequence converter 3, as shown in Figure 4, the high-frequency component is removed by the filter 6a, and input to the level determiner 6b, for Level is judged. In the case of continuous overvoltage, since it is equal to or greater than a predetermined level, it is output to the signal amplitude discriminator 6c. And, in the signal amplitude discriminator 6c, the time range of the signal is discriminated, because the time range of the leakage signal is also greater than or equal to the judgment value, therefore, the counter 6d is further utilized to reset the counter 6d during the period before the timer 6e The leakage signal is counted at a substantially commercial frequency, and is determined as a leakage, and is output to the switch unit 8 . The switch unit 8 is turned on by this output, and an excitation current flows from the power supply circuit 5 to the trip coil 4 a via the switch unit 8 , and the trip mechanism 4 b operates, thereby opening the switch contact 2 . The power supply to the power supply circuit 5 is stopped by opening the switch contact 2 .

In this way, if the overvoltage is continuously applied to the AC circuit 1, the output voltage of the power supply circuit 5 exceeds the second predetermined value, and the time exceeding the second predetermined value exceeds the predetermined time, so that the leakage tester 10 is driven, thereby reducing the leakage current. The circuit breaker 101 can protect the power supply circuit 5 from failure by performing an earth leakage interruption operation.

In addition, as mentioned above, in order to prevent unnecessary operation caused by the momentary surge, the leakage detection circuit 6 uses the function of counting and judging that the leakage signal repeats at a substantially commercial frequency, so that the leakage detection circuit 6 It does not operate under an overvoltage caused by a momentary surge, but only operates when a continuous overvoltage greater than or equal to a specified time is applied.

According to this embodiment, there is: a power supply circuit 5, which is composed of a rectifier circuit 52, a second constant voltage circuit 53, a second Zener diode 54, and a second resistor 55, wherein the rectifier circuit 52 is supplied from the AC circuit 1 The AC voltage is converted into a DC voltage, the second constant voltage circuit 53 steps down the output of the rectifier circuit 52, the second Zener diode 54 detects an overvoltage based on the output voltage of the rectifier circuit 52, and the second resistor 55 The 2nd Zener diode 54 makes the output voltage boost of the 2nd constant voltage circuit 53 when overvoltage is detected; absorbing the surge current when it reaches the first predetermined value; and the leakage test circuit 10, which is provided on the output side of the power supply circuit 5, and includes an overvoltage detection circuit that is configured when the rated voltage of the power supply circuit 5 reaches the second predetermined value When the trip device 4 is driven, the second predetermined value is higher than the rated voltage of the power supply circuit 5 and lower than the first predetermined value. Since the above-mentioned components are included, even if the voltage is continuously applied to the AC circuit 1 during a withstand voltage test, etc. Even in the case of an overvoltage, the earth leakage circuit breaker 101 can be protected from failure by shutting off the earth leakage circuit breaker 101 .

In addition, since the leakage detection circuit 6 counts and judges that the leakage signal repeats at a substantially commercial frequency, the leakage test circuit 10 drives the tripping device 4 when the output voltage of the power supply circuit 5 exceeds the second predetermined value for a predetermined time. , can not operate under the overvoltage caused by the instantaneous surge voltage, and prevent unnecessary cut-off.

In addition, the leakage test circuit 10 including the overvoltage detection circuit is only required to add the fourth Zener diode 9a as an overvoltage detection circuit in the leakage test circuit generally provided with an earth leakage circuit breaker as an essential function, so that it can be used at a relatively low cost. The low-cost protection earth leakage circuit breaker 101 does not generate a failure caused by continuous application of overvoltage to the AC circuit 1 due to a withstand voltage test or the like.

Implementation mode 3.

5 is a circuit diagram showing the configuration of a DC earth leakage circuit breaker using the power supply circuit according to Embodiment 3 of the present invention.

In FIG. 5 , the earth leakage circuit breaker 102 of the present embodiment applies the overvoltage detection circuit 9 of Embodiment 1 to an earth leakage circuit breaker for direct current. In the first embodiment, the zero-phase-sequence converter is used as the leakage current detector, but the fluxgate sensor 31 capable of detecting a direct current leakage current is used as the leakage current detector, and various functions similar to those in the above-mentioned first embodiment are realized. Effect.

As shown in FIG. 5 , the fluxgate sensor 31 has: an annular iron core 31a into which the DC circuit 11 is inserted; a coil 31b wound on the iron core 31a; The wave applies a voltage to the coil 31a so that the magnetic flux density of the coil 31b is saturated while reversing the direction; current is detected.

In addition, in order to prevent failures when the positive pole and the negative pole are reversely connected, the rectifier circuit 52 provided in Embodiment 1 can be provided, but it is not necessary when used in a DC circuit, so it is deleted, and the current limiting resistor 51 It is directly connected to the second constant voltage circuit 53 . Specifically, the drain of the FET 53a of the second constant voltage circuit 53 is connected to the positive side of the voltage supplied from the DC circuit 11, and the anode of the third Zener diode is connected to the negative side of the voltage supplied from the DC circuit 11. And the connection point of the second resistor 55. The operation of the power supply circuit 5 of the present embodiment is the same as that of the first embodiment after the voltage has been DC-converted by the rectifier circuit 52 , and thus description thereof will be omitted.

According to the present embodiment, a power supply circuit 5 is provided, which is composed of a second constant voltage circuit 53, a second Zener diode 54, and a second resistor 55, wherein the second constant voltage circuit 53 receives the power supplied from the DC circuit 11 The second Zener diode 54 detects the overvoltage from the DC circuit 11, and the second resistor 55 activates the second constant voltage circuit when the second Zener diode 54 detects the overvoltage. The output voltage of 53 is boosted; the third zener diode 56 is arranged on the output side of the power supply circuit 5, and absorbs the surge current when the output voltage of the power supply circuit 5 reaches the first predetermined value; and the overvoltage detection circuit 9, It is installed on the output side of the power supply circuit 5, and drives the trip device 4 when the output voltage of the power supply circuit 5 exceeds a second predetermined value, wherein the second predetermined value is higher than the rated voltage of the power supply circuit 5 and higher than the first predetermined value. The predetermined value is low, and since the above-mentioned components are included, even when an overvoltage is continuously applied to the DC circuit 11 in a withstand voltage test or the like, the earth leakage circuit breaker 102 can be disconnected to protect the earth leakage circuit breaker 102 from failure.

Implementation mode 4.

6 is a circuit diagram showing the configuration of a DC earth leakage circuit breaker according to Embodiment 4 of the present invention.

In FIG. 6 , an earth leakage circuit breaker 103 of the present embodiment has a structure in which an earth leakage test circuit 10 including an overvoltage detection circuit of the second embodiment is applied to an earth leakage circuit breaker for direct current shown in the third embodiment. Similar to Embodiment 3, a fluxgate sensor 31 capable of detecting a DC leakage current is used as a leakage current detector, and a leakage test including an overvoltage detection circuit is provided instead of the overvoltage detection circuit 9 of Embodiment 3. Circuit 10. In addition, various effects similar to those of Embodiment 2 and Embodiment 3 described above are achieved.

In addition, in this embodiment, in order to prevent failure when the positive electrode and the negative electrode are connected in reverse, a rectifier circuit 52 which is not provided in the third embodiment is provided.

The fluxgate sensor 31 has: an annular iron core 31a into which the DC circuit 11 is inserted; a coil 31b wound on the iron core 31a; and a drive circuit 31c that applies a voltage to the coil 31a with positive and negative symmetrical rectangular waves. , so that the magnetic flux density of the coil 31b is saturated while reversing the direction; and a detection circuit 31d that detects the leakage current based on a measurement voltage that changes according to the coil current flowing in the coil 31a.

Leakage test circuit 10 is made up of following parts: the 4th zener diode 9a, its cathode is connected with the cathode of the 3rd zener diode 56; Test switch 10a, its one end is connected with the output of the 1st constant voltage circuit 7, and the other end is connected with The anode of the 4th zener diode 9a is connected; the resistor 10c, one end is connected to the cathode of the 4th zener diode 9a; and the transistor 10d, the base is connected to the other end of the test switch 10a, and the collector is connected to the other end of the resistor 10c connect.

In addition, the emitter of the transistor 10d, which is the output of the leakage test circuit 10, is connected to one end of the test winding 11, and the other end of the test winding 11 is connected to the negative output side of the rectifier circuit 52 after passing through the coil 31a of the fluxgate sensor 31.

The leakage test function for checking whether the leakage circuit breaker is normal is constituted by the leakage test circuit 10 and the test winding 11 .

The other configurations and operations are the same as those in Embodiment 3, so descriptions thereof are omitted.

Next, the operation will be described.

In order to perform a normal leakage test operation, when the test switch 10a is turned on, power is supplied from the second constant voltage circuit 53, the transistor 10d is switched on and off, and a test current, that is, a leakage simulation current, flows to the test winding 11 through the resistor 10c. . When the test current flows through the test winding 11 , if it is judged by the detection circuit 31 d as leakage from the output of the iron core 31 a , it is output from the detection circuit 31 d to the switch unit 8 . The switch unit 8 is turned on by this output, and an exciting current flows from the power supply circuit 5 to the trip coil 4a via the switch unit 8, and the trip mechanism 4b operates, thereby opening the switching contact 2 and shutting off the earth leakage circuit breaker 103.

Next, a case where a continuous overvoltage is superimposed on the DC circuit 11 will be described.

If an overvoltage of several kV is continuously applied to the DC circuit 11, as in Embodiment 2, the applied voltage to the series circuit of the second Zener diode 54 and the first Zener diode 53b exceeds that of the second Zener diode. 54 and the Zener voltage sum of the first Zener diode 53b, the second Zener diode 54 is also turned on.

At this time, the current Ic flowing through the second resistor 55 becomes several tens of mA compared with the usual tens of μA to several hundreds of μA, and a voltage drop occurs across the second resistor 55, and the current Ic is applied between the second resistor 55 and the second resistor 55. The voltage Vc across the first Zener diode 53b rises. For example, if the resistance value of the second resistor 55 is about 100 ohms and the current Ic is about 40mA, the voltage drop across the second resistor 55 is about 4V, and the voltage applied to the second resistor 55 and the first Zener diode 53b Vc becomes about Vc=24V+4V=28V. The output voltage Vd of the second constant voltage circuit 53 increases to about 25V by adding about 4V, which is the voltage drop amount of the second resistor 55, to the normal rated voltage of about 21V. However, since the voltage of about 25V exceeds the Zener voltage (about 24V) of the third Zener diode 56, the third Zener diode 56 is turned on, and the output voltage Vd of the second constant voltage circuit 53 is suppressed to the third Zener voltage. The Zener voltage of the nanodiode 56 (about 24V).

In addition, since the output voltage Vd of the second constant voltage circuit 53 exceeds the Zener voltage 23V of the fourth Zener diode 9a, the fourth Zener diode 9a is turned on, and the transistor 10d is turned on, so that the analog voltage flows through the test winding 11. leakage current. When the simulated leakage current flows through the test winding 11 , the output of the core 31 a changes, and when the detection circuit 31 d determines that the change is leakage, the output is output from the detection circuit 31 d to the switch unit 8 . The switching means 8 is turned on by this output, and an exciting current flows from the power supply circuit 5 to the trip coil 4a via the switching means 8, and the trip mechanism 4b operates, thereby opening the switching contact 2. The switching contact 2 is opened, and the power supply to the power circuit 5 is stopped. In addition, the detection circuit 31d is configured to determine leakage when the change in the output from the core 31a exceeds a predetermined time.

In this way, when an overvoltage is continuously applied for a certain period of time, the leakage tester 10 is driven to perform a leakage interruption operation, thereby protecting the power supply circuit 5 from failure.

According to the present embodiment, there is provided a power supply circuit 5 composed of a second constant voltage circuit 53 , a second Zener diode 54 , and a second resistor 55 , wherein the second constant voltage circuit 53 converts the electric power supplied from the DC circuit 11 The second Zener diode 54 detects the overvoltage from the DC circuit 11, and the second resistor 55 activates the second constant voltage circuit when the second Zener diode 54 detects the overvoltage. The output voltage of 53 is boosted; the third zener diode 56 is arranged on the output side of the power circuit 5, and absorbs the surge current when the output voltage of the power circuit 5 reaches the first predetermined value; and the leakage test circuit 10, its It is provided on the output side of the power supply circuit 5 and includes an overvoltage detection circuit that drives the trip device 4 when the output voltage of the power supply circuit 5 exceeds a second predetermined value, wherein the second predetermined value is higher than the power supply The rated voltage of the circuit 5 is high and lower than the first predetermined value. Because of the above-mentioned components, even when an overvoltage is continuously applied to the AC circuit 1 in a withstand voltage test or the like, the leakage circuit breaker 103 can cut off the voltage. , and the protection leakage circuit breaker 103 does not fail.

Claims (5)

1. A leakage circuit breaker, which has: Open and close contacts, which make and break the circuit; a leakage current detector, which detects the leakage current of the circuit; A leakage detection circuit, which is connected to the leakage current detector, and detects the leakage based on the detection signal of the leakage current detector; a tripping device, which is driven by the leakage detection circuit to separate the opening and closing contacts; and A power supply circuit comprising a step-down circuit, a voltage detection circuit, and a step-up circuit, wherein the step-down circuit steps down the power supplied from the circuit to constant voltage power, and the voltage detection circuit detects the power from the circuit detects an overvoltage, and the boost circuit boosts the output voltage of the step-down circuit when the voltage detection circuit detects an overvoltage, The leakage circuit breaker is characterized in that it has: a current sink circuit, which is provided on the output side of the power circuit, and absorbs the surge current when the output voltage of the power circuit reaches a first predetermined value; and an overvoltage detection circuit provided on the output side of the power supply circuit, and drives the tripping device when the output voltage of the power supply circuit exceeds a second predetermined value, wherein the second predetermined value is higher than that of the power supply circuit The rated voltage is higher than the first predetermined value. 2. The earth leakage circuit breaker according to claim 1, characterized in that, The overvoltage detection circuit drives the trip device when the output voltage of the power supply circuit exceeds the second predetermined value for a predetermined time. 3. The earth leakage circuit breaker according to claim 2, characterized in that, The overvoltage detection circuit drives a switching element connected to the trip device. 4. The earth leakage circuit breaker according to claim 2, characterized in that, A secondary winding is provided, the secondary winding passes through the leakage current detector for passing a simulated leakage current, and the overvoltage detection circuit causes the leakage current to flow by passing the simulated leakage current through the secondary winding. The detection circuit operates to drive the tripping device. 5. The earth leakage circuit breaker according to any one of claims 1 to 4, characterized in that, The current sink circuit is the first zener diode, The step-down circuit is composed of a field effect transistor, a first resistor, and a first Zener diode, the drain of the field effect transistor is connected to the positive side of the voltage supplied from the circuit, and the first resistor is connected to the field effect transistor. between the drain and gate of the transistor, the first zener diode is connected between the gate of said field effect transistor and the negative side of said circuit, The voltage detection circuit is a second zener diode connected between the drain and the gate of the field effect transistor, The boost circuit is a second resistor connected in series with the first Zener diode between the gate of the field effect transistor and the negative side of the circuit, The overvoltage detection circuit is a third Zener diode.