Earth leakage tripping devices and earth leakage breakers

Abstract

To provide a leakage tripping device capable of coping with various power supply voltage without increasing size of a tripping coil.SOLUTION: A leakage tripping device 60 comprises: a tripping device 4 containing a tripping coil and a tripping mechanism 4c; and a leakage detection part that detects a leakage of an AC electric path 1, and energizes the tripping coil of the tripping device 4. The tripping coil comprises: a first coil 4a; and a second coil 4b that is serially connected to the first coil 4a, and of which a wire diameter is smaller than that of the first coil 4a. The leakage tripping device 60 comprises: a relay 56 that includes a contact point 56a; and a relay driving circuit. Therein, the relay driving circuit is configured to: detect a voltage of the AC electric path 1; when the voltage detected is larger than a first voltage, open a path of the contact point 56a so as to enable energizing the first coil 4a and the second coil 4b; when the voltage detected is smaller than the first voltage, close the path of the contact point 56a so as to enable energizing the first coil 4a.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an earth leakage tripping device and an earth leakage breaker having a tripping coil for opening a switching contact provided in an electric circuit. [Background technology]

[0002] An earth leakage breaker includes a switching contact provided in an AC circuit, a switching mechanism for switching the switching contact, a leakage detection circuit for detecting leakage in the AC circuit, and a tripping device for operating the switching mechanism to open the switching contact and trip the earth leakage breaker when leakage is detected. The tripping device has a tripping coil that constitutes an electromagnetic solenoid for operating the switching mechanism (see, for example, Patent Document 1). The voltage of the AC circuit is directly applied to the tripping coil. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-6201 A Summary of the Invention [Problem to be solved by the invention]

[0004] In earth leakage current circuit breakers, if the AC circuit voltage is applied directly to the trip coil, it becomes difficult to accommodate a wide range of power supply voltages. For example, even if the rated power supply voltage is 230V, product specifications may require operation at 50V, and damage must be prevented even at 440V to prevent misconnection of the AC circuit. Furthermore, when the power supply voltage is low, the electromagnetic force of the trip coil is weak, resulting in inactivity if the required tripping load is large. When the power supply voltage is high, the current increases, causing trip coil burnout and damage to electronic components. One solution to these problems is to increase the number of turns in the trip coil, but this increases the trip coil size, making it difficult to adopt. Changing the trip coil wire diameter creates a trade-off between the above issues, resulting in insufficient performance across a wide range of power supply voltages.

[0005] The present disclosure has been made in view of the above, and has an object to provide an earth leakage tripping device that can accommodate a wide range of power supply voltages without increasing the size of the tripping coil. [Means for solving the problem]

[0006] To solve the above-mentioned problems and achieve the object, the earth leakage tripping device disclosed herein trips an earth leakage breaker that drives switching contacts that open and close an AC electric circuit. The earth leakage tripping device includes a tripping device having a tripping coil connected to the AC electric circuit and a tripping mechanism that opens the switching contacts when the tripping coil is energized, and an earth leakage detection unit that detects an electric leakage in the AC electric circuit and energizes the tripping coil of the tripping device. The tripping coil includes a first coil and a second coil connected in series to the first coil and having a smaller wire diameter than the first coil. The earth leakage tripping device also includes a relay having contacts connected in parallel to the second coil, and a relay drive circuit that detects the voltage of the AC electric circuit and, when the detected voltage is greater than the first voltage, opens the contacts to allow the first coil and the second coil to be energized, and closes the contacts to allow the first coil to be energized when the detected voltage is less than the first voltage. [Effects of the Invention]

[0007] The earth leakage tripping device of the present disclosure has the advantage of being able to accommodate a wide range of power supply voltages without increasing the size of the tripping coil. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a circuit diagram showing a configuration example of an earth leakage breaker according to a first embodiment; [Figure 2] FIG. 1 is a circuit diagram showing a first configuration example of a step-down circuit used in an earth leakage breaker according to a first embodiment; [Figure 3] FIG. 1 is a circuit diagram showing a second configuration example of a step-down circuit used in the earth leakage breaker according to the first embodiment; [Figure 4]FIG. 1 is a circuit diagram showing a configuration example of a voltage detection circuit used in a ground fault circuit interrupter according to a first embodiment. [Figure 5] 1 is a circuit diagram showing a configuration example of an earth leakage breaker according to a first embodiment; [Figure 6] 1 is a circuit diagram showing a configuration example of an earth leakage breaker according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An earth leakage tripping device and an earth leakage breaker according to embodiments will be described in detail below with reference to the drawings.

[0010] Embodiment 1 Fig. 1 is a circuit diagram showing an example of the configuration of an earth leakage circuit breaker according to a first embodiment. In Fig. 1, an earth leakage circuit breaker 100 has a switching contact 2, a switching mechanism 70, and an earth leakage trip device 60. The switching contact 2 switches an AC current circuit 1 between a power supply device and a load device. The switching mechanism 70 has a mechanism for driving the switching contact 2 to switch.

[0011] The earth leakage trip device 60 has a zero-phase-sequence current transformer 3, an earth leakage detection circuit 6, a thyristor 8, a trip device 4, and a power supply circuit 5. The zero-phase-sequence current transformer 3 is inserted in the AC power circuit 1 and detects the zero-phase-sequence current flowing in the AC power circuit 1. The earth leakage detection circuit 6 detects an earth leakage based on the zero-phase-sequence current detected by the zero-phase-sequence current transformer 3. The thyristor 8 is driven by an output signal from the earth leakage detection circuit 6. The trip device 4 opens the switching contacts 2 when the thyristor 8 is driven. The power supply circuit 5 supplies power to the earth leakage detection circuit 6 and the trip device 4. The zero-phase-sequence current transformer 3, the earth leakage detection circuit 6, and the thyristor 8 constitute an earth leakage detection unit that detects an earth leakage in the AC power circuit 1 and energizes the trip coil of the trip device 4.

[0012] The tripping device 4 includes a first coil 4a and a second coil 4b as tripping coils and a tripping mechanism 4c. The first coil 4a and the second coil 4b are connected in series and connected to the AC current circuit 1. A thyristor 8 is connected in series to the first coil 4a, and the first coil 4a and the second coil 4b are energized via the thyristor 8. The first coil 4a has a larger wire diameter and a smaller resistance component than the second coil 4b. In other words, the second coil 4b has a smaller wire diameter and a larger resistance component than the first coil 4a. The tripping mechanism 4c includes a plunger, a movable iron core, a fixed iron core, and the like that together with the first coil 4a and the second coil 4b constitute an electromagnetic solenoid. When the first coil 4a and the second coil 4b are energized, the electromagnetic solenoid is activated, driving the switching mechanism 70 and opening the switching contacts 2.

[0013] The power supply circuit 5 includes a capacitor 51, which is a current limiting circuit, a rectifier circuit 52 consisting of a full diode bridge, a smoothing capacitor 53, a step-down circuit 54, a voltage detection circuit 55, and a relay 56. The capacitor 51 is connected to the AC current path 1 and limits the current input to the rectifier circuit 52. The rectifier circuit 52 is provided downstream of the capacitor 51 and rectifies the AC voltage and converts it into a DC voltage. The smoothing capacitor 53 is connected in parallel between the positive and negative buses of the output of the rectifier circuit 52 and smoothes the output voltage of the rectifier circuit 52. The step-down circuit 54 is provided downstream of the smoothing capacitor 53 and steps down the output voltage of the rectifier circuit 52 to output the stepped-down voltage. The voltage detection circuit 55 is provided downstream of the step-down circuit 54 and controls the opening and closing of the relay 56 in accordance with the voltage smoothed by the smoothing capacitor 53.

[0014] The relay 56 has a contact 56a and a coil 56b (see FIGS. 4 and 5). One end of the contact 56a is connected to the AC circuit 1, and the other end is connected to the connection point between the first coil 4a and the second coil 4b. The contact 56a of the relay 56 is connected in parallel to the second coil 4b. When the contact 56a is closed, it shorts both ends of the second coil 4b. When the contact 56a is closed, only the first coil 4a is energized, and when the contact 56a is open, both the first coil 4a and the second coil 4b are energized.

[0015] With this configuration, the power supply circuit 5 supplies the AC voltage input from the AC electric circuit 1 to the first coil 4a and the second coil 4b, and also converts the AC voltage input from the AC electric circuit 1 to a DC voltage, steps down the voltage, and supplies the stepped-down voltage to the leakage detection circuit 6. The power supply circuit 5 constitutes a relay drive circuit that detects the voltage of the AC electric circuit 1, and when the detected voltage is equal to or higher than a first voltage, opens the contact 56a of the relay 56 to allow current to flow through the first coil 4a and the second coil 4b, and closes the contact 56a of the relay 56 to allow current to flow only through the first coil 4a when the detected voltage is lower than the first voltage.

[0016] Fig. 2 is a circuit diagram showing a first configuration example of the step-down circuit 54 used in the earth leakage breaker 100 according to the first embodiment. Fig. 3 is a circuit diagram showing a second configuration example of the step-down circuit 54 used in the earth leakage breaker 100 according to the first embodiment. A step-down circuit 54a of the first configuration example shown in Fig. 2 uses a Zener diode. A step-down circuit 54b of the second configuration example shown in Fig. 3 uses a three-terminal regulator. Other configurations may be adopted for the step-down circuit 54, such as a well-known switching power supply.

[0017] 2 includes a resistor 54a1 and a Zener diode 54a2. In this step-down circuit 54a, the resistor 54a1 removes ripple components from the input voltage, and the stepped-down voltage is output from the cathode of the Zener diode 54a2, which is connected in series with the resistor 54a1.

[0018] 3 includes a three-terminal regulator 54b1 and a capacitor 54b2 connected between the output of the three-terminal regulator 54b1 and ground. The three-terminal regulator 54b1 reduces the input voltage and outputs the reduced voltage. The capacitor 54b2 prevents oscillation.

[0019] 4 is a circuit diagram showing a configuration example of a voltage detection circuit 55 used in the earth leakage breaker 100 according to the first embodiment. The voltage detection circuit 55 receives the voltage smoothed by the smoothing capacitor 53 and a constant voltage as input, and closes a contact 56a of a relay 56 if the potential difference therebetween is equal to or greater than a certain value.

[0020] The voltage detection circuit 55 shown in FIG. 4 includes resistors 55a and 55b, a field effect transistor (FET) 55c, and a resistor 55d. The resistors 55a and 55b are connected in series between the positive and negative buses of the output of the rectifier circuit 52. The gate of the FET 55c is connected to the connection point of the resistors 55a and 55b. The drain of the FET 55c is connected to the resistor 55d, and the source of the FET 55c is connected to ground. One end of the resistor 55d is connected to the output of the step-down circuit 54, and the other end is connected to the drain of the FET 55c. A coil 56b of a relay 56 is connected in parallel between the drain and source of the FET 55c.

[0021] In the voltage detection circuit 55, the DC voltage between the positive and negative buses smoothed by the smoothing capacitor 53 is divided by resistors 55a and 55b, and the divided voltage is input to the gate of the FET 55c. The output voltage of the step-down circuit 54 is applied between the drain and source of the FET 55c. The threshold voltage between the gate and source of the FET 55c is determined by the output voltage of the step-down circuit 54. In the voltage detection circuit 55, if the divided voltage input to the gate of the FET 55c is greater than the threshold voltage between the gate and source of the FET 55c, a current flows between the drain and source of the FET 55c, and the coil 56b of the relay 56 is not driven. When the coil 56b of the relay 56 is not driven, the contact 56a is open, and therefore the first coil 4a and the second coil 4b are energized. When the divided voltage is equal to or less than the gate-source threshold voltage of FET 55c, no current flows between the drain and source of FET 55c, but rather flows to coil 56b of relay 56. When current flows to coil 56b of relay 56, contact 56a is closed, so that only first coil 4a is energized. The gate-source threshold voltage corresponds to the first voltage.

[0022] Fig. 5 is a circuit diagram showing a configuration example of an earth leakage circuit breaker 101 according to the first embodiment. In the earth leakage circuit breaker 101 of Fig. 5, the step-down circuit 54 of the earth leakage circuit breaker 100 of Fig. 1 is replaced with the step-down circuit 54a shown in Fig. 2, and the voltage detection circuit 55 is replaced with the circuit configuration shown in Fig. 4. The operation of the earth leakage circuit breaker 101 will be described.

[0023] First, as an example of a case where the voltage of the AC electric circuit 1 is low, a case where the AC voltage of the AC electric circuit 1 is AC 50V at a frequency of 50 Hz will be described.

[0024] When an AC voltage of AC 50 V is supplied from the AC power circuit 1, an AC current flows through the capacitor 51. The AC current is rectified by the rectifier circuit 52 and converted into a DC voltage. The DC voltage output from the rectifier circuit 52 is smoothed by the smoothing capacitor 53. The smoothed DC voltage Va output by the smoothing capacitor 53 is stepped down to, for example, DC 5 V, which is a low-voltage DC voltage Vb with ripple removed by the step-down circuit 54 a, and is supplied to the leakage detection circuit 6.

[0025] When the current limiting capacitor 51 is 5 μF, the smoothing capacitor 53 is 1 μF, and the resistor 54 a 1 is 1.5 kΩ, the current Ia flowing through the capacitor 51 is Z=(Z1+1500) / Z2 Z1=1 / (2×π×50Hz×5×10 -6 ) Z2=1 / (2×π×50Hz×1×10 -6 ) In this case, Ia=50 / Z=30.2mA This becomes: Here, the current flowing to the resistor 54a1 side is shunted to the smoothing capacitor 53, so 30.2×Z2 / (1500+Z2)=20.5mA.

[0026] Therefore, the voltage across resistor 54a1 is 20.5×10 -3 ×1500=30.7V This becomes: The DC voltage Va across the smoothing capacitor 53 is 35.7V, which is the sum of the Zener voltage of the Zener diode 54a2 (5V) and the voltage across the resistor 54a1 (30.7V).

[0027] Here, when the resistor 55a constituting the voltage detection circuit 55 is 1 MΩ and the resistor 55b is 80 kΩ, the gate voltage of the FET 55c obtained by dividing the DC voltage Va by the resistors 55a and 55b is as follows: 35.7V x (80 x 10 3 / (80×10 3 +1000×10 3))=2.65V This becomes:

[0028] Here, if the gate-source threshold voltage of FET 55c is set to 3.5V, the gate voltage (2.65V) is lower than the threshold voltage (3.5V), so no current flows between the drain and source of FET 55c. Therefore, current flows from the output of step-down circuit 54a to coil 56b via resistor 55d. If resistor 55d is set to 200Ω, the current flowing to coil 56b will be 5 / 200=25mA because DC voltage Vb is 5V.

[0029] When a current flows through the coil 56b, an electromagnetic force is generated in the coil 56b, causing the contact 56a of the relay 56 to close the circuit, and the second coil 4b to be short-circuited.

[0030] In this state, if a leakage current occurs from the AC power line 1 to the ground, the zero-phase-sequence signal from the zero-phase-sequence current transformer 3 is sent to the leakage detection circuit 6 via a voltage conversion circuit (not shown). The leakage detection circuit 6 determines the peak voltage value or voltage width of the zero-phase-sequence signal sent, and if it exceeds a threshold, determines that a leakage current has occurred and supplies a gate signal to the thyristor 8, turning it on. This causes conduction between the anode and cathode of the thyristor 8. At this time, the second coil 4b is short-circuited, so the AC voltage of the AC power line 1 is applied only to the first coil 4a. The first coil 4a has a larger wire diameter than the second coil 4b, and therefore has a smaller resistance component than the second coil 4b. If the resistance component of the first coil 4a is set to 11 Ω, the current flowing through the first coil 4a will be AC50V / 11Ω=4.55A This becomes:

[0031] Therefore, even with a low voltage of about AC 50V, the first coil 4a can be excited and the tripping mechanism 4c can be driven. Driving the tripping mechanism 4c activates the switching mechanism 70, opening the switching contacts 2 and tripping the earth leakage breaker 101. This makes it possible to prevent accidents caused by leakage current.

[0032] The supply of the gate signal from the leakage detection circuit 6 formed by the integrated circuit to the thyristor 8 is reset when the leakage current disappears, regardless of whether the power supply side and load side of the earth leakage circuit breaker 101 are connected correctly (positive connection) or reverse connection (power supply side and load side of the earth leakage circuit breaker 101 are connected in reverse), and the anode-cathode of the thyristor 8 becomes non-conductive. Then, when the anode-cathode of the thyristor 8 becomes non-conductive, the excitation of the first coil 4a is stopped.

[0033] Next, as an example of a case where the AC voltage of the AC electric circuit 1 is a high voltage, a case where the AC voltage of the AC electric circuit 1 is AC 440V at a frequency of 50 Hz will be described.

[0034] When an AC voltage of 440 V AC is supplied from the AC power circuit 1, an AC current flows through the capacitor 51. The AC current is rectified by the rectifier circuit 52 and converted into a DC voltage. The DC voltage output from the rectifier circuit 52 is smoothed by the smoothing capacitor 53. The smoothed DC voltage Va output by the smoothing capacitor 53 is stepped down to, for example, DC 5 V, which is a low-voltage DC voltage Vb from which ripples have been removed, by the step-down circuit 54 a, and is then supplied to the leakage detection circuit 6.

[0035] As described above, when the capacitor 51 is 5 μF, the smoothing capacitor 53 is 1 μF, and the resistor 54a1 is 1.5 kΩ, the current Ia flowing through the capacitor 51 is Z=(Z1+1500) / Z2 Z1=1 / (2×π×50Hz×5×10 -6 ) Z2=1 / (2×π×50Hz×1×10 -6 ) In this case, Ia=440 / Z=265.7mA This becomes: Here, the current flowing to the resistor 54a1 side is shunted to the smoothing capacitor 53, so 265.7×Z2 / (1500+Z2)=180.6mA.

[0036] Therefore, the voltage across resistor 54a1 is 180.6×10 -3 ×1500=270.9V This becomes: The DC voltage Va across the smoothing capacitor 53 is 275.9V, which is the sum of the Zener voltage of the Zener diode 54a2 (5V) and the voltage across the resistor 54a1 (270.9V).

[0037] Here, when the resistor 55a constituting the voltage detection circuit 55 is 1 MΩ and the resistor 55b is 80 kΩ, the gate voltage of the FET 55c obtained by dividing the DC voltage Va by the resistors 55a and 55b is as follows: 275.9V x (80 x 10 3 / (80×10 3 +1000×10 3 ))=20.4V This becomes:

[0038] Here, if the threshold voltage between the gate and source of FET 55c is set to 3.5V, the gate voltage (20.4V) is higher than the threshold voltage (3.5V), so the drain and source of FET 55c are conductive. As a result, coil 56b is short-circuited, and no current flows through coil 56b. Because no electromagnetic force is generated in coil 56b, contact 56a of relay 56 is open-circuited.

[0039] In this state, if a leakage current occurs from the AC power line 1 to the ground, the zero-phase-sequence signal from the zero-phase-sequence current transformer 3 is sent to the leakage current detection circuit 6. The leakage current detection circuit 6 determines the peak voltage value or voltage width of the zero-phase-sequence signal sent, and if it exceeds a threshold, determines that a leakage current has occurred and supplies a gate signal to the thyristor 8, turning it on. This results in electrical continuity between the anode and cathode of the thyristor 8. At this time, the contact 56a of the relay 56 is open circuit, so the AC voltage of the AC power line 1 is applied to the series combination of the first coil 4a and the second coil 4b. The second coil 4b has a smaller wire diameter than the first coil 4a, and therefore has a larger resistance component than the first coil 4a. If the resistance component of the second coil 4b is assumed to be 51 Ω, the current flowing through the first coil 4a and the second coil 4b is AC440V / (11+51)Ω=7.1A This becomes:

[0040] Therefore, in the case of a high voltage of about AC 440V, the first coil 4a and the second coil 4b are excited, and the tripping mechanism 4c can be driven. Driving the tripping mechanism 4c activates the switching mechanism 70, opening the switching contacts 2 and tripping the earth leakage breaker 101. This makes it possible to prevent accidents caused by leakage current. Furthermore, even at a high voltage of AC 440V, a large current will not flow, causing the tripping coil to melt or damage electronic components, and the tripping mechanism 4c can be driven safely.

[0041] As described above, in the first embodiment, the tripping coil is formed by a series connection of the first coil 4a and the second coil 4b, which has a smaller wire diameter than the first coil 4a, and the relay 56 has a contact 56a connected in parallel to the second coil 4b, and detects the voltage of the AC current circuit 1, and when the detected voltage is greater than the first voltage, the contact 56a is opened to allow current to flow through the first coil 4a and the second coil 4b, and when the detected voltage is less than the first voltage, the contact 56a is closed to allow current to flow through only the first coil 4a. Therefore, it is possible to realize an earth leakage circuit breaker that can be used with a wide range of power supply voltages without increasing the size of the tripping coil.

[0042] Embodiment 2 Fig. 6 is a circuit diagram showing a configuration example of an earth leakage breaker 102 according to the second embodiment. In the second embodiment, the voltage detection circuit 55 of the first embodiment shown in Fig. 5 is replaced with a voltage detection circuit 65 with a Schmitt trigger circuit. The other configurations are the same as those of the first embodiment, and therefore, redundant explanations will be omitted.

[0043] In the configuration example of FIG. 5 shown in the first embodiment, if the voltage input to the gate of FET 55c, which is the voltage divided by resistors 55a and 55b, fluctuates due to fluctuations in the power supply voltage supplied from AC circuit 1, the operation of FET 55c may become unstable. In the second embodiment, a voltage detection circuit 65 with a Schmitt trigger circuit is employed, which provides hysteresis to the input of voltage detection circuit 65, thereby stabilizing the operation of voltage detection circuit 65 even when the voltage input to the gate of FET 55c fluctuates. Furthermore, in the second embodiment, contact 56a of relay 56 is a B contact, and when coil 56b is non-conductive, contact 56a is closed, and when coil 56b is conductive, contact 56a is open. Other configurations are the same as those in the first embodiment, and detailed description thereof will be omitted.

[0044] The voltage detection circuit 65 includes resistors 65a, 65b, 65d, 65e, 65g, and 65i, NPN transistors 65c and 65f, and a PNP transistor 65h. Resistors 65a and 65b are connected in series between the positive and negative buses of the output of the rectifier circuit 52. Resistors 65d, 65g, and 65e and NPN transistors 65c and 65f form a Schmitt trigger circuit. The base of NPN transistor 65c is connected to the junction of resistors 65a and 65b. The collector of NPN transistor 65c is connected to resistor 65d, and the emitter of NPN transistor 65c is connected to ground via resistor 65e. One end of resistor 65d is connected to the output of the step-down circuit 54a, and the other end is connected to the collector of NPN transistor 65c and the base of NPN transistor 65f. The collector of the NPN transistor 65f is connected to a resistor 65g, and the emitter of the NPN transistor 65f is connected to ground via a resistor 65e. One end of the resistor 65g is connected to the output of the step-down circuit 54a, and the other end is connected to the collector of the NPN transistor 65f and the base of the PNP transistor 65h. The emitter of the PNP transistor 65h is connected to a resistor 65i, and the collector of the PNP transistor 65h is connected to ground. One end of the resistor 65i is connected to the output of the step-down circuit 54a, and the other end is connected to the emitter of the PNP transistor 65h. A coil 56b of the relay 56 is connected in parallel between the emitter and collector of the PNP transistor 65h.

[0045] The smoothed DC voltage Va is divided by resistors 65a and 65b, and the divided voltage is input to the base of NPN transistor 65c. Here, let Ve be the voltage across resistor 65e. If the divided voltage is lower than 0.6 + Ve, which is the sum of Ve and the base-emitter potential of 0.6V, NPN transistor 65c does not turn on, and the collector potential of NPN transistor 65c becomes approximately 5V. Because the collector potential of NPN transistor 65c is at the same potential as the base of NPN transistor 65f, NPN transistor 65f turns on. When NPN transistor 65f turns on, the collector potential of NPN transistor 65f becomes the potential obtained by dividing the output voltage of voltage-step-down circuit 54a by resistors 65g and 65e. Because the collector of NPN transistor 65f has the same potential as the base of PNP transistor 65h, the potential divided by resistors 65g and 65e is set to a value that turns on PNP transistor 65h. When PNP transistor 65h turns on, no current flows through coil 56b of relay 56, and contact 56a of relay 56 (contact B) becomes a closed circuit, shorting second coil 4b. As a result, only first coil 4a functions as a tripping coil.

[0046] On the other hand, when the voltage divided by resistors 65a and 65b is higher than 0.6V+Ve, NPN transistor 65c turns on, causing conduction between the emitter and collector of NPN transistor 65c and between the base and emitter of NPN transistor 65f. This turns NPN transistor 65f off, and the collector potential of NPN transistor 65f becomes approximately 5V. Because the collector of NPN transistor 65f has the same potential as the base of PNP transistor 65h, PNP transistor 65h does not turn on, and current flows through coil 56b of relay 56. The electromagnetic force generated by the current flowing through coil 56b of relay 56 opens the B contact of relay 56. As a result, first coil 4a and second coil 4b function as tripping coils.

[0047] When NPN transistor 65f is off, no current flows through resistor 65e, and the threshold voltage at which NPN transistor 65c turns on drops to 0.6V. In other words, when NPN transistor 65f is on, the threshold base potential at which NPN transistor 65c turns on is 0.6V+Ve, and when NPN transistor 65f is off, the threshold base potential at which NPN transistor 65c turns off is 0.6V, resulting in hysteresis operation. Even if the voltage input to voltage detection circuit 65 fluctuates, PNP transistor 65h, which drives coil 56b of relay 56, can be operated stably.

[0048] As described above, according to the second embodiment, the voltage detection circuit 65 with a Schmitt trigger circuit is employed, so that even if the voltage input to the voltage detection circuit 65 fluctuates, the voltage detection circuit 65 that drives the coil 56b of the relay 56 can operate stably.

[0049] The configurations shown in the above embodiments are examples of the contents of the present disclosure, and may be combined with other known technologies, and parts of the configurations may be omitted or modified within the scope of the gist of the present disclosure. [Explanation of symbols]

[0050] 1 AC circuit, 2 switching contact, 3 zero-phase current transformer, 4 tripping device, 4a first coil, 4b second coil, 4c tripping mechanism, 5 power supply circuit, 6 earth leakage detection circuit, 8 thyristor, 51, 54b2 capacitor, 52 rectifier circuit, 53 smoothing capacitor, 54, 54a, 54b step-down circuit, 54a1, 55a, 55b, 55d, 65a, 65b, 65d, 65e, 65g, 65i resistor, 54a2 Zener diode, 54b1 three-terminal regulator, 55, 65 voltage detection circuit, 55c FET, 56 relay, 56a contact, 56b coil, 60 earth leakage tripping device, 65c, 65f NPN transistor, 65h PNP transistor, 70 switching mechanism, 100, 101, 102 Ground fault circuit interrupter.

Claims

1. An earth leakage tripping device that trips an earth leakage breaker that drives a switching contact that opens and closes an AC current circuit, a tripping device including a tripping coil connected to the AC current circuit and a tripping mechanism that opens the on-off contacts when current is applied to the tripping coil; a leakage current detection unit that detects a leakage current in the AC power line and energizes the trip coil of the trip device; Equipped with the tripping coil comprises a first coil and a second coil connected in series to the first coil and having a wire diameter smaller than that of the first coil; a relay having a contact connected in parallel with the second coil; a relay drive circuit that detects a voltage of the AC current circuit, and when the detected voltage is greater than a first voltage, opens the contacts to allow current to flow through the first coil and the second coil, and when the detected voltage is less than the first voltage, closes the contacts to allow current to flow through the first coil; An earth leakage tripping device comprising:

2. The relay drive circuit includes: a rectifier circuit that converts the AC voltage of the AC current circuit into a DC voltage; a smoothing circuit that smoothes the output voltage of the rectifier circuit; a step-down circuit that steps down the output voltage of the smoothing circuit; a voltage detection circuit that opens the contacts to allow current to flow through the first coil and the second coil when a divided voltage obtained by dividing the output voltage of the smoothing circuit is greater than the first voltage determined by the output voltage of the step-down circuit, and that closes the contacts to allow current to flow through the first coil when the divided voltage is smaller than the first voltage; 2. The earth leakage tripping device according to claim 1, further comprising:

3. The voltage detection circuit is a Schmitt trigger circuit.

3. The earth leakage tripping device according to claim 2, further comprising:

4. An earth leakage tripping device according to any one of claims 1 to 3; The switching contact; a switching mechanism that drives the switching contacts to open and close by the operation of the tripping mechanism; A ground fault circuit interrupter comprising:

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