JPS61214717A - Leak breaker - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an earth leakage breaker in which a thyristor for energizing and disconnecting a tripping coil is provided with an erroneous ignition prevention circuit.

[Technical background of the invention and its problems] In general, an earth leakage breaker includes a control I power supply section, a tripping coil that trips the main circuit contact, a thyristor that disconnects the current from this tripping coil, and a gate of this thyristor. and an earth leakage detection means for controlling. A series circuit consisting of a resistor and a protective capacitor is connected in parallel with the thyristor as an erroneous ignition prevention circuit. This false ignition prevention circuit suppresses the rise rate of the voltage applied to the junction inside the element when the thyristor is turned off, so-called dv/dt (hereinafter referred to as forward blocking voltage rise rate), and absorbs surges to prevent false ignition. Established for the purpose of preventing In order to enhance the effect of suppressing the rate of increase in forward blocking voltage, the resistance may be set to a small value or the protective capacitor may be set to a large value.

However, this increases the rate of rise of the current passing through the junction when the thyristor is turned on, the so-called di,/dt (hereinafter simply referred to as the on-current rise rate).In other words, when the thyristor turns on, the protection capacitor is charged at this moment. Charges are discharged through the thyristor, and the larger the protective capacitor and the smaller the resistance, the larger the discharge current, so the rate of increase in current during on-state increases, and the thyristor is more likely to be destroyed.

[Object of the Invention] Therefore, the present invention provides a capacitor for suppressing the rate of increase in forward blocking voltage, which can effectively suppress the rate of increase in forward blocking voltage when turning on and off the circuit resistor, and can also prevent an increase in the rate of increase in current at the time of ON due to capacitor discharge. The purpose of this invention is to provide an earth leakage breaker that can also be expected to have a smoothing function for control power supplies.

[Summary of the Invention] In order to achieve the above object, the present invention connects a diode in series with a protective capacitor connected in parallel with a thyristor to prevent the charged electric charge from discharging through the thyristor, and to A resistor is provided so that the charged charge is discharged through the discharge resistor to the power source load side, and the discharge loop also serves as a smoothing function, and the series circuit of the diode and discharge resistor is tripped. It is arranged in parallel with the coil and has the effect of preventing an increase in the back electromotive force of the tripping coil due to an external surge.

[Embodiment of the Invention] A first embodiment of the invention will be described below with reference to FIG. A main circuit power supply 1 is connected to a motor 4 via main circuit contacts 2 and main circuit conductors 3. This main circuit conductor 3 has no control tI! In order to form the power supply section 5, the input side of the high frequency rectifier circuit 6 is connected via a control power transformer 7, and among the DC buses 8 and 9 connected to the output terminals P1 and Nl of the control N deep section 5, One end of a tripping coil 10 for tripping the main circuit contact 2 is connected to the positive DC bus 8 , and the other end is connected to the negative DC bus 6 via a thyristor 11 . Reference numeral 12 denotes an erroneous firing prevention circuit, which will be explained below. Seven nodes of the diode 13 are connected to the anode side of the thyristor 11, and the cathode is connected to the thyristor 11 via the current limiting resistor 14 and the protective capacitor 15.
Further, a discharge resistor 16 is connected between the cathode of the diode 13 and the positive DC bus 8.

Further, a series circuit of a smoothing capacitor 17 and a resistor 18 is connected between the DC buses 8 and 9. Reference numeral '19 denotes an earth leakage detection means, which is composed of a zero-phase current transformer 20 whose primary conductor is the main circuit conductor 3, and a control circuit 21 whose output is received at input terminals A and B, as is well known. The voltage between the terminals of the smoothing capacitor 17 is applied to the power input terminals Pz and N2 of this control circuit 21, and the voltage between the terminals of the thyristor 11 is applied to the control output terminal S.
gate is connected. In addition, 22 is a well-known test circuit consisting of a test switch 23, a resistor 24, and a conducting wire 25. When the test switch 23 is closed by suppression, a pseudo current leakage state is formed on the primary side of the zero-phase current transformer 20. It looks like this. Further, 26 is a surge absorbing element connected between the primary winding terminals of the transformer 7.

The general operation of this earth leakage breaker is as follows. That is, if a leakage fault occurs in the motor 4 during operation when power is being supplied from the main circuit power supply 1 to the motor 4 via the main circuit contacts 2, an unbalanced output is obtained at the zero-phase current transformer 20, which causes When the level exceeds a certain level, a trip command signal is output from the control output terminal S of the control circuit 21. This trip command signal is applied to the gate of thyristor 11 to turn it on. As a result, the tripping coil 10 is energized and the main circuit contact 2 is tripped. If an overcurrent accident occurs, a bimetal mechanism (not shown) is activated and its mechanical displacement trips the main circuit contact.

Next, to describe the function of the false ignition prevention circuit 12, the forward blocking voltage increase rate when the thyristor 11 is turned off is determined by dividing the DC voltage by the tripping coil 1o, the current limiting resistor 14, and the protective capacitor 15. This effect is suppressed to a lower value as the value of the protective capacitor 15 becomes larger. On the other hand, when the thyristor 11 is turned on, the charge in the protective capacitor 15 is transferred to the thyristor 1.
Even if an attempt is made to discharge through the thyristor 1, it is blocked by the diode 13, so that the rate of increase in the on-state current of the thyristor 11 due to the discharge current does not increase, and is suppressed to an increase only due to the load current. Therefore, by increasing the value of the protective capacitor 15, the rate of increase in forward blocking voltage can be effectively suppressed, and stable operation with less erroneous firing can be expected.

In this case, the charge in the protective capacitor 15 is discharged to the load side of the control power supply unit 5, such as the smoothing capacitor 17, via the current limiting resistor 14, the discharging resistor 16, and the resistor 18. On the other hand, in a steady state, the protective capacitor 15 is charged by the ripple voltage between the DC bus 8. 16 and resistor 18 to the smoothing capacitor 17, this protective capacitor 15 exhibits a smoothing effect that reduces ripples in the voltage between the terminals of the smoothing capacitor 17.

Furthermore, when a surge voltage is applied to the main circuit conductor 3 and the voltage value clipped by the surge absorbing element 26 is large, normally it is connected to the thyristor 11 through the control power supply section 5 and further through the tripping coil 10. The parallel protection capacitor 15 is charged.

Normally, when this charging current decreases, tripping coil 1
However, according to the configuration of the above embodiment, the back electromotive force generated in the tripping coil 10 is absorbed by the closed loop passing through the diode 13 and the M resistor 16, and its increase is prevented, so that the increase in the forward blocking voltage and the W ratio can be suppressed, and the occurrence of false ignition can be prevented.

It should be noted that the present invention is not limited to the above embodiments (
, as in the second embodiment shown in FIG. 2, in which the same parts as in FIG. At this time, the charging current flowing into the protective capacitor 15 via the tripping coil 1o becomes large, so that the tripping mechanism of the main circuit contact 2 can be applied except for the sensitive polar type.

[Effects of the Invention] As described above, according to the present invention, a diode is interposed in series with the protective capacitor connected in parallel with the thyristor for suppressing the rate of increase in forward blocking voltage, and the diode and the tripping coil are connected in series. The feature is that a discharge resistor is provided in parallel with the series circuit of the thyristor, and this configuration can effectively suppress the rate of increase in forward blocking voltage and the rate of increase in ON current of the thyristor, thereby preventing false firing of the thyristor. It is possible to provide an earth leakage breaker that can effectively prevent the occurrence of electrical surges, the protective capacitor also has a smoothing effect, and further prevent false ignition due to external surges.

[Brief explanation of the drawing]

FIG. 1 is a wiring diagram showing a first embodiment of the invention, and FIG. 2 is a wiring diagram showing main parts of a second embodiment of the invention. In the figure, 1 is the main circuit power supply, 2 is the main circuit contact, 4 is the motor,
5 is a control power supply section, 6 is a full-wave rectifier circuit, 7 is a transformer for control power supply, 8.9 is a DC bus, and 10 is a control power supply section. Tripping coil, 11 thyristor, 12 false ignition prevention circuit, 13 diode, 15 protective capacitor, 16
1 is a discharge resistor, and 19 is a leakage detection means. Figure 1

Claims (1)

[Claims] 1. A control power supply section consisting of a control power transformer and a rectifier circuit, a tripping coil connected via a thyristor between the DC bus bars of this control power supply section and tripping the main circuit contacts, and controlling the gate of the thyristor. An earth leakage detection means, an anode connected to the anode side of the thyristor, and a cathode branched into two, one of which is connected to the cathode side of the thyristor through a protective capacitor and the other connected to the positive side of the DC bus through a discharge resistor. and a discharge blocking diode connected to each of them to prevent leakage or disconnection.