JP4623560B2 - Earth leakage breaker - Google Patents

Description

  The present invention relates to a circuit for supplying power to a leakage detection circuit.

  As shown in FIG. 2, even when any one of the three-phase three-wire type electric circuits R, S, and T is open, the earth leakage breaker 21 that interrupts the electric circuit when the earth leakage is detected includes a diode bridge 22 for each phase. Are connected to the positive output terminal of the diode bridge 22, one end of the coil 23 is connected, and the other end is connected to the negative output terminal of the diode bridge 22 via the thyristor 24. The gate of the thyristor 24 is connected to the leakage detection circuit 25. The zero-phase current transformer 26 detects the current flowing through the three-phase three-wire circuits R, S, T, and the output current of the zero-phase current transformer 26 is When the predetermined value is exceeded, the leakage detection circuit 25 outputs a signal to turn on the thyristor 24, drive the trip coil 23 to turn off the main contact 27, and cut off the electric circuits R, S, and T. ing. The power supply used in the leakage detection circuit 25 of the leakage breaker 21 is a DC power supply of about 12V, and since it is a three-phase three-wire circuit, an AC power supply of about 50V to 400V is converted into a DC power supply of about 12V by the power supply circuit. It has been converted. The power circuit 28 includes a plurality of resistors 29 connected in series to the positive output terminal of the diode bridge 22, and a smoothing capacitor 31 and a constant voltage diode 32 connected in parallel between the output terminals of the diode bridge 22. . In the power supply circuit 28, the current value is reduced by a plurality of resistors 29. However, there is a problem that a large amount of heat is generated, and other electronic components are deteriorated, and the operable voltage is narrow. was there. Therefore, as a method for solving these problems and reducing the current value of the power supply, for example, there is a method described in Patent Document 1. In this earth leakage breaker, a smoothing capacitor (5) is connected in parallel between output terminals of a diode bridge (4) connected to an electric circuit, and a constant current diode (7) is connected to a positive output terminal of the diode bridge (4). A parallel circuit of voltage diodes (6) is connected to the leakage detection circuit (2) to supply power.

Japanese Patent Laid-Open No. 5-17497 (FIG. 1)

  However, the earth leakage circuit breaker using the constant current diode in the conventional power supply circuit has the disadvantages that since it uses the constant current diode, the reliability is low, the life may be short, and the cost is very high. .

The present invention connects the trip coil to the output of the diode bridge connected to each phase so that the trip coil for interrupting the circuit is driven even if any one of the three-phase three-wire circuit is lost. The zero-phase current transformer detects the leakage current flowing through the three-phase three-wire circuit, and when the output current of the zero-phase current transformer exceeds a predetermined value, the leakage detection circuit outputs a signal to In the earth leakage circuit breaker that turns on and drives the trip coil to cut off the electric circuit, the power supply circuit that supplies power to the electric leakage detection circuit has a resistor, a capacitor, and a resistor in each phase of the three-phase three-wire circuit. A current limiting circuit that is connected in series and restricts the discharge of the capacitor with front and rear resistors when the circuit is interrupted, a second diode bridge connected to the output terminal of the current limiting circuit, and an output of the second diode bridge Connected in parallel between terminals Characterized by being constituted by a smooth capacitor and a constant voltage diode.

  According to the present invention, it can be configured with inexpensive and highly reliable parts, and there is an effect that the product life can be extended and the cost can be reduced.

A power supply circuit that supplies power to the leakage detection circuit is connected in series to each phase of the three-phase three-wire circuit, and the capacitor discharge is limited by the front and rear resistors when the circuit is interrupted. A current limiting circuit, a second diode bridge connected to the output terminal of the current limiting circuit, and a smoothing capacitor and a constant voltage diode connected in parallel between the output terminals of the second diode bridge.

  First Embodiment An earth leakage circuit breaker according to a first embodiment of the present invention will be described with reference to the attached drawing of FIG.

  The earth leakage circuit breaker 1 attached to the three-phase three-wire electric circuit R, S, T has an input terminal of the diode bridge 2 connected to each phase R, S, T, and a tripping coil 3 connected to a positive output terminal of the diode bridge 2 Are connected to the negative output terminal of the diode bridge 2 via the thyristor 4, and the gate of the thyristor 4 is connected to the leakage detection circuit 5, and the three-phase three-wire circuit R, S, The zero-phase current transformer 6 detects the current flowing through T, and when the output current of the zero-phase current transformer 6 exceeds a predetermined value, the leakage detection circuit 5 outputs a signal to turn on the thyristor 4 and trip The coil 3 is driven to turn off the main contact 7, and the electric circuits R, S, T are cut off.

  In this leakage breaker 1, a power supply circuit 8 for supplying power to the leakage detection circuit 5 is constituted by a current limiting circuit 9, a second diode bridge 10, a smoothing capacitor 11, and a constant voltage diode 12. The current limiting circuit 9 is formed by connecting a resistor 13, a capacitor 14, and a resistor 15 in series in order, and the input terminal of the current limiting circuit 9 is connected to each phase of the three-phase three-wire circuit R, S, T, and the output The terminal is connected to the input terminal of the second diode bridge 10. A smoothing capacitor 11 and a constant voltage diode 12 are connected in parallel between the output terminals of the second diode bridge 10.

  The power supply circuit 8 configured in this manner steps down and outputs a wide input voltage of 50 V to 400 V by the current limiting circuit 9, full-wave rectifies the AC waveform by the second diode bridge 10, and DC by the smoothing capacitor 11. The waveform is converted into a drive voltage for the leakage detection circuit 5 by the constant voltage diode 12.

  Even if one of the three phases is lost, the remaining two phases are rectified by the second diode bridge 10 and a DC power is supplied to the leakage detection circuit 5 via the smoothing capacitor 11 and the constant voltage diode 12. Therefore, the leakage detection circuit 5 does not stop, and the tripping coil 3 can also be excited and interrupted by the current flowing from the remaining two phases by the diode bridge 2.

Since the current limiting circuit 9 is composed of two resistors and one capacitor for each phase, the current limiting circuit 9 is inexpensive and the discharge of the capacitor is limited by the front and rear resistors when the circuit is interrupted . Long life and almost no heat generation.

It is a circuit diagram of an earth-leakage circuit breaker according to the present invention. It is a circuit diagram of the conventional earth-leakage circuit breaker.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Leakage breaker 2 Diode bridge 3 Trip coil 4 Thyristor 5 Leakage detection circuit 6 Zero phase current transformer 7 Main contact 8 Power supply circuit 9 Current limiting circuit 10 2nd diode bridge 11 Smoothing capacitor 12 Constant voltage diode 13 Resistor 14 Capacitor 15 Resistor

Claims (1)

The trip coil is connected to the output of a diode bridge connected to each phase so that the trip coil for interrupting the circuit is driven even if any one of the three-phase three-wire circuit is lost. The zero-phase current transformer detects the leakage current that flows in the three-phase three-wire circuit, and when the output current of the zero-phase current transformer exceeds a predetermined value, the leakage detection circuit outputs a signal and turns on the switching element. In the earth leakage circuit breaker that cuts off the electric circuit by driving the tripping coil, a power supply circuit that supplies power to the electric leakage detection circuit includes a resistor, a capacitor, and a resistor for each phase of the three-phase three-wire electric circuit. a current limiting circuit formed by limiting the discharge of the capacitor when interrupting the electrical path in the resistor before and after said sequentially connected in series vessels, and a second diode bridge connected to the output terminal of the current limiting circuit, The second diode bridge Earth leakage breaker, characterized in that is constituted by a smoothing capacitor and zener diode are connected in parallel between di output terminal.

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