JPS6149890B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION An object of the present invention is to provide an earth leakage breaker that allows reverse connection of load side terminals and power supply side terminals.

In the conventional circuit shown in Fig. 1, thyristor 1
A DC voltage that has been double-wave rectified by a diode bridge B and smoothed by a capacitor _C1 is applied to both ends of the anode A and cathode K of the circuit. When a leakage occurs in the load 2 of the electrical circuit, a voltage is induced in the secondary winding of the zero-phase current transformer ZCT, which is amplified by the amplifying section 3, and the amplified voltage at the amplifying section 3 is It is applied to the gate G of the thyristor, and the thyristor 1 is triggered. When the thyristor turns on, a current flows from rectifier bridge B to trip coil TC to thyristor 1, opening contacts S ₁ and S ₂ and cutting off the electrical circuit. When the contacts S ₁ and S ₂ open, the voltage at the c and d terminals becomes zero, so the voltage across the anode A and cathode K of the thyristor becomes zero, and the thyristor loses its self-holding capacity, turning the thyristor into an OFF state.

However, in this conventional method, when the c and d terminals of the earth leakage breaker 4 are connected to the power supply 5 and the load 2 is connected to the a and b terminals, an earth leakage occurs in the load,
The thyristor turns on and the trip coil TC
Even if the contacts S ₁ and S ₂ open, the thyristor remains in the ON state because voltage is supplied to terminals c and d and voltage is applied to both anode A and cathode K of the thyristor. Keep doing it. Therefore, current continues to flow through thyristor 1, trip coil TC, and diode bridge B. For the above reasons, in the conventional circuit system, it is not possible to use the earth leakage breaker by connecting the terminals on the power supply side and the terminals on the load side in reverse. The present invention enables this reverse connection.

The present invention will be explained in detail below with reference to FIGS. 2 to 7.

First, as a method of using a thyristor without self-holding, the thyristor's A-
A method of applying a half-wave rectified voltage between K or the third method
There is a method of applying AC voltage as shown in the figure. In this way, even if a positive voltage is applied between A and K of the thyristor and the thyristor is turned on, the thyristor will be turned off in the next half cycle.
In other words, in the conventional circuit system (Fig. 1), once the thyristor was turned on, it remained in the ON state until contacts S ₁ S ₂ opened, but the When an alternating current or half-wave rectified voltage is applied, the thyristor remains on during the period when a positive voltage is applied between A and K, but then turns off during the negative half cycle.

However, when a half-wave rectified voltage or an alternating current voltage is applied between A and K of the thyristor in this manner, the following problem occurs.

Normally, the input voltage at the widening part of the earth leakage breaker
Since V ₁ or the induced voltage of ZCT is minute,
We perform B-class or C-class width expansion, which has high width expansion efficiency. In other words, the ZCT's secondary output voltage is amplified by half a wave. In the earth leakage breaker shown in Fig. 4,
lg: Electric circuit leakage current, V ₁ : ZCT induced voltage, V _1S : Amplifier threshold voltage, V ₂ : Amplifier output voltage, V ₄ : Thyristor gate voltage, V ₅ : Power supply voltage. The current and voltage waveforms are as shown in FIG. In FIG. 5, when the amplifier input voltage V ₁ exceeds the threshold voltage V _1S , an output voltage V ₂ is generated, and the output voltage V ₂ has a pulse-like voltage waveform synchronized with the leakage current. This amplifier output voltage V ₂ is waveform-shaped by an integrating circuit 6, and the waveform-shaped voltage V ₄ energizes the gate G of the thyristor. However, the phase of the current leakage current Ig with respect to the commercial power supply voltage V ₅ can have any phase relationship.
In the case of FIG. 5, the thyristor is conductive only during the t _S period shown at e. That is, current flows through the trip coil TC only during the period t _S shown in FIG. 5e. Here, V _GT is the gate trigger voltage of the thyristor. For this reason, the tripping electromagnet TC
cannot generate enough attractive force to trip the circuit contacts S ₁ and S ₂ . In this regard, in the conventional circuit, a DC voltage is applied between A and K of the thyristor, and once the thyristor is turned on, it remains in the ON state, so this kind of problem did not occur.

The present invention solves the above problems by applying an alternating current voltage or a half-wave rectified voltage between A and K of a thyristor.

FIG. 6 shows a circuit of an earth leakage breaker according to the present invention. In the figure, 7 is a comparator. The comparator 7 is a comparator circuit in which the output voltage V ₄ is zero if the output voltage V 3 of the integrating circuit is less than the threshold voltage value V _3S , and the output voltage _{V 4 becomes} a high level voltage when V ₃ <V _3S . be. Part a is a series circuit of a resistor _R3 and a diode D, and is connected to the output terminal of the integrating circuit 6 and the output terminal of the comparator 7. accordingly
When V ₃ < V _3S , part a is the resistance value of R ₃ only, and V ₃
>V _3S , the integrating circuit output voltage becomes a voltage value that inverts the comparator. When inverted, the potential at the comparator connection point becomes higher than that at the connection point of part a to the integrating circuit, so a reverse voltage is applied to diode D, resulting in impedance of part a becoming a high resistance close to infinity.

When the earth leakage breaker is not operating, that is, when the integrating circuit output voltage is V ₃ < V _3S , the impedance of section a is
R ₃ and becomes infinite when V ₃ >V _3S .

That is, when the integrating circuit output V ₃ reaches the threshold voltage value V _3S of the comparator 7, the V ₃ voltage suddenly becomes equal to or higher than the threshold voltage value of the comparator 7 because the portion a becomes an infinite resistance value. This relationship is shown in FIG.

In Fig. 7, when the integrator circuit output voltage reaches the threshold voltage V _3S at t ₁ , the impedance Z of part a becomes infinite as shown in e, so the integrator circuit output voltage V ₃ becomes as shown in d at t ₁ . As shown, the voltage is sufficiently larger than the threshold voltage V _3S of the comparator. Therefore, the output voltage V ₄ of the comparator shown in Fig. f has a flat voltage waveform as shown in Fig. F even though the output voltage V ₃ of the integrating circuit shown in Fig. d has a ripple. As a result, when the thyristor A and K are biased in the positive direction, the thyristor turns on without fail, so a half-wave current flows through the trip coil TC as shown in figure g. Trip coil TC even in phase relationship
It becomes possible to supply a current that reliably opens the circuit contacts S ₁ and S ₂ . Moreover, when the contacts S ₁ and S ₂ are opened, the current leakage current Ig in the circuit naturally becomes zero, and V ₁ ,
V ₂ , V ₃ , and V ₄ are zero volts.

Therefore, even if an AC voltage is applied between A and K of the thyristor, the G gate voltage of the thyristor V ₄ =0. Since the thyristor is surely turned off during the half cycle in which the voltage between the thyristors A and K is reverse biased, the thyristor is thereafter in the cut-off state. In other words, in Fig. 6, even if the c and d terminals are connected as the power supply side and the a and b terminals as the load side,
A leakage occurs in the electrical circuit and the thyristor turns on,
When the trip coil operates and opens the contacts S ₁ and S ₂ , the current leakage current Ig becomes zero and the thyristor is necessarily turned off, so there is no problem. The same applies when a half-wave rectified voltage is applied between A and K. As described above, according to the circuit of the present invention, in the earth leakage breaker, the power supply side terminal and the load side terminal can be used in reverse connection. Note that if you simply apply positive feedback from the output side to the input side of the comparator to provide hysteresis characteristics, the above diode D is not necessarily required, but in that case, surge voltages such as those caused by lightning or load disconnection may occur. A-
If even a small amount of this surge voltage is induced at the G terminal when applied between K and K, there is a risk that this will be positively fed back, turning on the thyristor, and causing the contacts S ₁ and S ₂ to malfunction. However, in the circuit of the present invention, the diode D prevents the surge voltage from flowing into the input side, and there is no possibility that the thyristor will be turned on by the surge voltage.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a conventional earth leakage breaker, Figure 2 is a circuit diagram of a conventional earth leakage breaker.
3 and 4 are circuit diagrams for explaining the establishment of the present invention, FIG. 5 is an explanatory diagram of the operation of the circuit in FIG. 4, and FIG. FIG. 7 is an explanatory diagram of the operation of the circuit shown in FIG. 1...Thyristor, 2...Load, 3...Width expansion part, 4...
Earth leakage breaker, 5...Power supply, 6...Integrator circuit, 7...Comparator, a...Series circuit of resistor and diode,
a, b...power side terminals, c, d...load side terminals,
ZCT...Zero-phase current transformer, A...Anode, K...Cathode, G...Gate, B...Rectifier bridge, TC...Trip coil, _S1 , _S2 ...Circuit switching contact, _R1 , _R2 ,
R ₃ , R ₄ ... Resistor, C ₁ , C ₂ ... Capacitor, V _{1 ... Zero-phase current transformer induced voltage, V 2 ...} Amplifier output voltage, V ₃ ... Integrating circuit output voltage, V ₄ ... Thyristor gate voltage ,
V ₅ ...power supply voltage, Ig...leakage current.

Claims (1)

[Claims] 1 A zero-phase current transformer that detects leakage current, an amplifying section that amplifies the output voltage of the zero-phase current transformer, an RC integrating circuit that waveforms the output of the amplifying section, and an output voltage of the integrating circuit that keeps the output voltage at a certain value. A series circuit of a resistor and a diode is connected between the output terminal of the integrator circuit and the output terminal of the comparator. An earth leakage breaker characterized in that a comparator output end is connected as a cathode side of a diode between the two.