JP5163473B2 - Earth leakage breaker - Google Patents

Description

  The present invention relates to a leakage breaker that detects a leakage current flowing in an AC circuit such as a power distribution system to interrupt the AC circuit and prevent a leakage accident.

  A conventional earth leakage breaker includes a control power supply circuit that steps down from the AC voltage of the AC circuit and supplies power to the earth leakage detection circuit, test circuit, and trip device, and an oscillation circuit that is a source of test current inside the earth leakage breaker And by supplying control power to the oscillation circuit via the test switch, the withstand voltage of the components constituting the test switch and the test circuit is reduced to achieve miniaturization (see, for example, Patent Document 1).

Japanese Patent Laying-Open No. 2006-302601 (stage 0015 to stage 0019, FIG. 2)

  However, the control power supply circuit of the conventional earth leakage breaker supplies power to both the oscillation circuit that generates the test current and the tripping device while the tripping device is driven by the test operation. There is a problem that it is necessary to increase the supply capacity of the circuit, and the control power supply circuit cannot be miniaturized.

  An object of the present invention is to obtain a leakage breaker that can perform a stable test operation without reducing the size of a test circuit and increasing the supply capability of a control power supply circuit.

  The leakage breaker according to the present invention includes a control power supply circuit that supplies a DC voltage obtained by stepping down an AC voltage of an AC circuit to a predetermined voltage to a leakage detection circuit, a trip device, and a test circuit. When the test switch closes, the test current flows, and when the leakage detection circuit does not output a signal, the test current is stopped after a predetermined time, and the leakage detection circuit outputs a signal. The test current is stopped before a predetermined time elapses.

  Since the earth leakage breaker according to the present invention controls the energization period of the test current and the drive current of the trip device, the test circuit can be downsized and a stable test operation can be performed without increasing the supply capability of the control power supply circuit. Can do.

Embodiment 1 FIG.
1 is a circuit diagram showing an earth leakage circuit breaker according to Embodiment 1 of the present invention. The earth leakage circuit breaker 1 has a power supply side connection terminal 2 and a load side connection terminal 3 corresponding to the power supply side connection terminal 2. In the earth leakage circuit breaker 1, an opening / closing part 5 for opening and closing an AC electric circuit 4 connecting the power supply side connection terminal 2 and the load side connection terminal 3 is provided. An external three-phase AC circuit (not shown) is connected to the power supply side connection terminal 2 and the load side connection terminal 3 of the earth leakage circuit breaker 1.

  The earth leakage breaker 1 includes a zero-phase current transformer 6 that detects an earth leakage or ground fault current (hereinafter simply referred to as an earth leakage current) flowing through the AC circuit 4 and outputs a detected current from the secondary winding 6a. doing. The conductors of all phases of the AC circuit 4 are linked through the annular iron core 6c, and a secondary winding 6a and a test winding 6b for a leakage breaker function test are wound around the iron core 6c.

  In addition, the leakage breaker 1 includes a leakage detection circuit 7 that monitors the detection current of the secondary winding 6a of the zero-phase current transformer 6 and determines whether there is a leakage or a ground fault (hereinafter simply referred to as a leakage). When the leakage occurs, the PNP transistor 8 that constitutes the drive switch 29 controlled by the output signal of the leakage detection circuit 7 and the transistor 8 become conductive, thereby tripping the opening / closing mechanism of the opening / closing portion 5 and alternating current circuit 4 A tripping device 9 that cuts off the current, a capacitor 10 that constitutes a current supply unit 34 that supplies and supplies the current of the control power supply VS at the start of operation of the tripping device 9, and a diode that prevents a reverse flow of the current in the capacitor 11, a rectifier circuit 12 that rectifies AC power applied to the AC circuit 4 to DC power, a control power supply circuit 13 that supplies stable power to internal circuits including the leakage detection circuit 7, a test circuit 14, The Eteiru. In the rectifier circuit 12, six diodes are bridge-connected in order to rectify from all phases of the AC circuit 4.

  The test circuit 14 mainly includes a test switch 15 that is closed during a test operation, a test current generation circuit 16 that supplies a test current to the test winding 6b of the zero-phase current transformer 6, and an operation of the test switch 15. And a plurality of components to be described later for controlling the test current generating circuit 16 in accordance with the output state of the transistor 8. The test current generation circuit 16 includes an oscillation circuit and generates a test current having a predetermined frequency.

  One end of the test switch 15 is connected to the control power supply VS supplied by the control power supply circuit 13, and the other end is connected to the resistor 17 and the capacitor 18. The other end of the resistor 17 is connected to GND which is the negative output of the control power circuit 13. The other end of the capacitor 18, one end of which is connected to the test switch 15, is connected to a resistor 20 that is a current detection unit 30 and an NPN transistor 21 through a resistor 19. The emitter of the NPN transistor 21 is connected to GND, the base is connected to the resistor 19, and the charging current of the capacitor 18 generated when the test switch 15 is closed becomes the base current of the transistor 21. The The resistor 20 is connected between the base and emitter of the transistor 21 and is a resistor for suppressing the leakage current of the transistor 21 and stabilizing the switching operation.

  The collector of the transistor 21 is connected through a resistor 22 to a resistor 23 and a PNP transistor 24 that constitute a power supply connection portion 32. The emitter of the PNP transistor 24 is connected to the control power supply VS, and the base is connected to the resistor 22. The collector of the transistor 24 is connected to the power supply input terminal of the test current generating circuit 16, and the control current VS is supplied to the test current generating circuit 16 by the conduction of the transistor 21 so that the test current generating circuit 16 generates a test current. Has been. The resistor 23 is connected between the base and emitter of the transistor 24 and is a resistor for suppressing the leakage current of the transistor 24 and stabilizing the switching operation.

  Further, the connection point between the capacitor 18 and the resistor 19 is connected to the cathode of the diode 25 and the anode of the diode 26 constituting the charging unit 33. The anode of the diode 25 is connected to GND, and the cathode of the diode 26 is connected to the collector of the transistor 8. Each is connected. The diode 25 and the resistor 17 constitute a discharge unit 31 that discharges the electric charge of the capacitor 18.

  In the earth leakage breaker 1 configured as described above, when a leakage occurs in the external three-phase AC circuit and a leakage current flows in the AC circuit 4, a detected current is received from the secondary winding 6a of the zero-phase current transformer 6. It is output and input to the leakage detection circuit 7. The leakage detection circuit 7 determines the occurrence of a leakage based on the input detection current, that is, determines that a leakage has occurred when the detection current exceeds a predetermined value, and causes the transistor 8 to be turned on by the control power supply circuit 13. The lowered control power supply VS is supplied to the trip device 9 and driven. The driven tripping device 9 trips the opening / closing mechanism of the opening / closing part 5 to open the opening / closing part 5 and interrupt the AC circuit 4.

  Next, the test circuit 14 that controls the test operation of the leakage detection function will be described. The operation of the earth leakage test is to perform an earth leakage trip by supplying a test current to a test winding 6b provided in the zero-phase current transformer 6, and by supplying power to the test current generating circuit 16, a predetermined current is supplied. Generate frequency test current.

  Next, the operation of the leakage test of the leakage breaker 1 will be described. FIG. 2 is a waveform diagram for explaining the operation of the test circuit 14 of the leakage breaker 1 shown in FIG. 1, where (a) shows the state of the test switch 15, (b) shows the voltage across the capacitor 18, (C) shows the current flowing through the capacitor 18, (d) shows the state of the transistor 21, and (e) shows the test current output from the test current generating circuit 16, respectively. In FIG. 2, even when the test switch 15 is kept closed, the operation until the test current stops after a predetermined time has elapsed will be described. This shows a case where a signal is output but this signal is not generated.

  The test operation of the earth leakage breaker 1 is started by the user closing the test switch 15. When the test switch 15 is closed (ON) at time t0, the potential at the connection point between the resistor 17 and the capacitor 18 becomes the potential of the control power supply VS, and the voltage across the capacitor 18 gradually increases as shown in FIG. As shown in FIG. 2C, the current of the capacitor 18 gradually decreases at the peak when the test switch 15 is closed. The current flowing through the capacitor 18 flows from the base of the resistor 20 and the transistor 21 through the resistor 19 to the emitter.

  Since the current flows from the base of the transistor 21 to the emitter, the transistor 21 becomes conductive (ON), but the current of the capacitor 18 also flows through the resistor 20 connected between the base and the emitter of the transistor 21. 2 (c) and FIG. 2 (d), a predetermined threshold value for conducting the transistor 21 is generated with respect to the current of the capacitor 18, and the period during which the current of the capacitor 18 exceeds the threshold value I1 (in the figure). The transistor 21 is turned on (ON) only (indicated by T1).

  When the transistor 21 becomes conductive, the base current of the transistor 24 flows through the resistor 22. The transistor 24 is turned on in synchronization with the conduction of the transistor 21, the control power supply VS is supplied to the test current generation circuit 16, and the test current is tested by the zero-phase current transformer 6 as shown in FIG. It is supplied to the winding 6b.

  As described above, even when the user continues closing the test switch 15, the test current flows only for a predetermined time T1. The predetermined time T1 depends on the time constant determined by the capacitance of the capacitor 18 and the resistor 19, the ON voltage determined by the base-emitter characteristics of the resistor 20 and the transistor 21, and the like. By selecting these time constants and ON voltage, the predetermined time T1 can be set to an arbitrary time.

  Next, an operation when the user opens the test switch 15 will be described. When the test switch 15 is opened, the electric charge stored in the capacitor 18 is discharged as follows. The positive charge on the test switch 15 side flows from the resistor 17 to GND, and the negative charge on the resistor 19 side flows as a current to the diode 25 to be discharged. Here, if the resistance value of the resistor 17 is set to a resistance value sufficiently lower than the resistance value of the resistor 20, the capacitor 18 is discharged in a short time, and the test circuit 14 can return to the initial state in a short time.

  Even if it is necessary to repeat the test operation in a short time, the test switch is returned to the initial state almost simultaneously when the test switch is opened, so there is no possibility that the test operation cannot be performed for a long time. Therefore, a reliable test operation can be performed.

  Next, the operation of the test circuit when the leakage detection circuit 7 outputs a signal due to the test current flowing will be described. FIG. 3 is a waveform diagram showing an original operation in which the leakage detection circuit 7 outputs a signal when a test current flows. 3, (a) is the state of the test switch 15, (b) is the output of the leakage detection circuit, (c) is the voltage across the capacitor 18, (d) is the current flowing through the capacitor 18, and (e) is the current flowing through the capacitor 18. The state of the transistor 21, (f) indicates the test current output from the test current generating circuit 16.

  First, the operation from when the test switch 15 is closed (ON) at time t0 to when a signal is output from the leakage detection circuit 7 is the same as that in FIG. When the leakage current detection circuit 7 determines that there is a leakage due to a test current generated by the test operation, the leakage detection circuit 7 generates a one-pulse signal (H pulse output period T2) as shown in FIG. Note that an H potential indicated by H in the figure is a potential for making the transistor 8 conductive, and an L potential indicated by L is a potential for making the transistor 8 nonconductive. A circuit for generating a one-pulse signal is well known and will not be described.

  When the leakage detection circuit 7 outputs a signal, the transistor 8 is turned on to drive the tripping device 9 and the diode 26 connected to the collector of the transistor 8 causes the resistor 19 side of the capacitor 18 to have a lower impedance than the resistor 19. Connect to GND to charge capacitor 18 rapidly. Therefore, the voltage across the capacitor 8 rises to a saturation voltage close to the voltage of the control power supply VS in a short time as shown in FIG. 3C and becomes constant, and the current of the capacitor 8 is pulled as shown in FIG. A large charging current flows at the moment when the driving of the detaching device 9 starts, and then the charging current becomes almost zero. As a result, as shown in FIGS. 3E and 3F, the transistor 21 becomes non-conductive (OFF) at the driving start timing of the tripping device 9, and the test current is almost simultaneously with the driving start of the tripping device 9. Stop.

  The state in which the test current is stopped is maintained as long as the test switch 15 is closed unless the natural discharge or leakage current of the capacitor 18 is extremely large, so that the test current does not flow again. When the test switch 15 is opened in this state, as in the case of FIG. 2, the charge of the capacitor 18 is discharged in a short time by the resistor 17 and the diode 25, and the test circuit 14 can return to the initial state in a short time. it can.

  Depending on the rated sensitivity current of the earth leakage breaker 1, the test current is consumed more than the driving current of the tripping device 9. However, in the earth leakage breaker 1 of the first embodiment, the test current stops at almost the same timing as the start of driving of the trip device 9, so that the test current and the drive current of the trip device 9 hardly flow at the same time. The maximum current consumption of the earth leakage breaker 1 can be reduced. Therefore, the capacity of the control power supply circuit 13, that is, the power supply capability can be lowered while maintaining a stable test operation. Further, since the capacitor 10 of the current supply unit 34 supplements the current of the control power supply VS and supplies it to the trip device 9 when the trip device 9 starts to operate, the trip device 9 can be reliably driven in a short time. Can do.

  Further, since all the components constituting the test circuit 14 are supplied with a voltage that is lower than the voltage of the control power supply VS and lower than the voltage of the AC circuit 4, it is possible not only to use small-signal general-purpose components but also to insulate each component. The distance can be greatly reduced. Therefore, the test circuit 14 can be miniaturized. Further, in order to prevent the test circuit 14 and the tripping device 9 from being damaged, it is not necessary to separately provide a mechanical burnout prevention switch that opens in conjunction with the opening / closing portion. Therefore, the earth leakage breaker 1 can be reduced in size, and the number of parts does not increase. That is, the cost of the earth leakage breaker 1 can be reduced.

  Consider a power load reverse connection state in which a load is connected to the power supply side connection terminal 2 of the earth leakage breaker 1 and an AC power supply is connected to the load side connection terminal 3. In this case, the control power supply circuit 13 continues to supply power to the internal circuit even when the opening / closing part 5 interrupts the AC power circuit 4. However, since the test circuit 14 allows the test current to flow only for a predetermined time even if the test switch 15 is kept closed, it is possible to prevent the test circuit 14, the trip device 9, and the control power circuit 13 from being burned out. . Therefore, since the earth leakage circuit breaker 1 is not deteriorated by the test operation, a stable test operation can be performed many times, and a stable trip operation can be maintained for a long time. That is, the life of the earth leakage breaker 1 can be extended.

  As described above, according to the ground fault circuit breaker of Embodiment 1 of the present invention, since the energization period of the test current and the drive current of the trip device 9 is controlled, it is necessary to increase the supply capability of the control power supply circuit 13. Unlike the conventional case where the control power supply circuit 13 cannot be reduced in size, the test circuit 14 can be reduced in size and a stable test operation can be performed without increasing the supply capability of the control power supply circuit 13.

  Although the transistors 21 and 24 have been described as NPN bipolar transistors and PNP bipolar transistors, respectively, the transistor 21 may be an N-type MOS transistor and the transistor 24 may be a P-type MOS transistor.

  Although the transistor 8 as the drive switch 29 has been described as an NPN bipolar transistor, it may be an N-type MOS transistor. Further, the drive switch 29 is a PNP bipolar transistor or P-type MOS transistor, and an L pulse obtained by inverting the H pulse of the leakage detection circuit 7, that is, the T2 period of FIG. It doesn't matter.

  Although the test current supply stop by the test current generation circuit 16 has been described in the case where the control power supply VS is disconnected by the transistor 24, the oscillation in the test current generation circuit 16 may be stopped.

It is a circuit diagram which shows the earth-leakage circuit breaker in Embodiment 1 of this invention. It is a wave form diagram of the earth-leakage circuit breaker of FIG. 1 when there is no output of an earth-leakage detection circuit. It is a wave form diagram of the earth-leakage circuit breaker of FIG. 1 in case there exists an output of an earth-leakage detection circuit.

Explanation of symbols

  4 AC circuit, 5 switching unit, 6 zero-phase current transformer, 6a secondary winding, 6b test winding, 7 leakage detection circuit, 9 trip device, 13 control power circuit, 14 test circuit, 15 test switch, 18 Capacitor, 19 resistor, 30 current detection unit, 31 discharge unit, 33 charging unit, 34 current supply unit.

Claims (5)

A zero-phase current transformer inserted in the AC circuit and having a secondary winding and a test winding;
A leakage detection circuit that outputs a signal based on the output current of the secondary winding of the zero-phase current transformer;
A tripping device that opens and closes the opening / closing part inserted into the AC circuit by a signal of the leakage detection circuit,
A test circuit configured to cause a test current to flow through the test winding of the zero-phase current transformer, and a DC voltage obtained by stepping down an AC voltage of the AC circuit to a predetermined voltage, the leakage detection circuit, the trip device, and the A control power supply circuit for supplying to the test circuit,
The test circuit causes the test current to flow when a test switch is closed. When the leakage detection circuit does not output the signal, the test circuit stops the test current after a predetermined time has elapsed, and the leakage detection circuit An earth leakage circuit breaker characterized by stopping the test current before the predetermined time elapses when a signal is output.   The test circuit includes a capacitor and a resistor connected in series and connected to the test switch, and a current detection unit that detects a charging current flowing through the capacitor, and a current detected by the current detection unit is a predetermined current value. The earth leakage circuit breaker according to claim 1, wherein the test current is supplied in the above case.   3. The earth leakage interrupter according to claim 2, wherein the test circuit includes a charging unit that charges the capacitor with an impedance lower than a resistance value of the resistor when the earth leakage detection circuit outputs the signal. vessel.   The earth leakage circuit breaker according to claim 2, wherein the test circuit includes a discharge unit that discharges the electric charge charged in the capacitor.   5. A current supply unit that is connected to one end of the trip device to which a DC voltage of the control power supply circuit is supplied and that supplies a current for driving the trip device. The earth-leakage circuit breaker of any one of Claims.

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