JPH0421237Y2 - - Google Patents

Description

[Detailed explanation of the idea] Industrial applications This proposal concerns electrical leakage and disconnection.

BACKGROUND OF THE INVENTION FIG. 3 shows a basic circuit for a typical leakage or disconnection circuit for relatively low AC line voltages.

In a typical earth leakage or disconnection circuit, the leakage current is detected by the leakage current detection current transformer ZCT, and the amplification and waveform shaping is performed by the amplification and shaping circuit AMP.
Drives a thyristor SCR such as an SCR or a triax, and connects the anode A and cathode K of the thyristor SCR.
The trip coil TC is activated by the conduction between the AC line and the load, and the AC line and the load are separated by a mechanically linked disconnector S.

However, D is a power rectifier circuit that rectifies the AC line voltage and supplies power to the thyristor SCR and the amplifying shaping circuit AMP, and R is a dropper resistor that provides an appropriate voltage drop when the voltage supplied to the AMP is high. AC line voltage tends to increase from 200V to 400V, and thyristors and power rectifier circuits
The diode must also have a correspondingly high withstand voltage. Generally, it is said that thyristors and diodes are required to have a withstand voltage of 1000V or more for an AC voltage of 400V. Small thyristors capable of operating a trip coil TC are easily available with a withstand voltage of several hundred volts at most, and a circuit like the one shown in Figure 3, which rectifies the AC line voltage and applies it directly to the thyristor, cannot be used. In addition, for a 400VAC line, the conventional method is to lower the voltage applied to the thyristor SCR and rectifier circuit D using the transformer T, including the amplifying shaping circuit AMP, as shown in Figure 4.
The withstand voltage of the SCR is to be allowed. Alternatively, as shown in FIG. 5, there is a method of lowering the power supply voltage to the allowable withstand voltage of the thyristor SCR using a constant voltage drop circuit or element Z.

Problems that the invention attempts to solve However, the method using the transformer T in Figure 4 is
It has the advantage of being able to use the 200VAC line and 400VAC line without changing circuit constants or components.
It is difficult to secure space for the transformer T, and the cost is also high. In addition, the method shown in Figure 5 is inexpensive and requires a small installation space because it does not use a transformer, but it cannot be used for AC line voltages of 400V and 200V, and circuit constants, elements, and parts must be changed. There are manufacturing inconveniences, such as having to

In an attempt to solve the above inconvenient problem, as shown in FIG. 6, thyristors are replaced at each terminal point of the gate G, anode A, and cathode K of one thyristor SCR in FIG. SCR ₁ and
Connect in series with SCR ₂ and each resistor in parallel with these.
R ₁ and R ₂ are inserted between the anodes and cathodes of thyristors SCR ₁ and SCR ₂ .
In addition, the voltage between terminals AK during standby (thyristor SCR ₁
and when SCR ₂ is non-conducting), the second thyristor SCR ₂
The gate _G2 is divided by resistors _R3 and _R4 and set to a voltage lower than the potential at the cathode _K2 of the thyristor _SCR2 . In other words, if there is no driving voltage at the gate _G1 of the first thyristor _SCR1 and an AC or DC ripple voltage is applied across the terminals AK, the thyristor
Both SCR ₁ and SCR ₂ are held non-conductive.

In this circuit, when an output voltage is generated from the amplifying shaping circuit AMP and applied to the terminal G, the first thyristor
The gate G ₁ of SCR ₁ is triggered and conduction occurs between the anode A ₁ and the cathode K ₁ . The anode A ₁ point is also the cathode K ₂ of the second thyristor SCR ₂ , and the potential of the cathode K ₂ becomes low due to conduction between the anode A ₁ and the cathode K ₁ , so the gate of the second thyristor SCR ₂ is The potential of _G2 becomes higher than that of the cathode _K2 , a gate current flows, and the second thyristor _SCR2 also becomes conductive between the anode A _and cathode _K2 . Eventually, conduction is established between the anode A _and the cathode _K1 , that is, between the terminals AK, and the trip coil TC is activated, the breaker opens, and the AC line and load are immediately disconnected. This circuit can connect two or more thyristors in series, even if they have a low withstand voltage, and increase the withstand voltage by approximately the number of thyristors.
It can be used for AC400V line and 200V line voltage at the same time without changing circuit constants, elements, or parts, and it is inexpensive because it does not take up installation space like a transformer, making it useful for users as an industrial product. It has great utility value. However, in the circuit of Figure 6, the gate G ₂ of the second thyristor SCR ₂ is connected to the resistor R ₄
Since it is connected to the anode A ₂ through the power line, if abnormal voltage such as lightning surge or noise is applied to the power line, some of the energy will be transferred to the second thyristor.
Joining gate G ₂ of SCR ₂ , the second thyristor
SCR ₂ may malfunction or, in extreme cases, be damaged.

Measures to solve the problem Taking these points into consideration, the proposed method connects the anodes and cathodes of multiple thyristors that drive the trip coil in series, and inserts a diode to prevent reverse current in the gate circuit of the second thyristor. However, it is connected to the output circuit of the amplifying and shaping circuit for earth leakage detection together with the gate circuit of the first thyristor.

Function: Thus, in the circuit according to the present invention, even if thyristors with relatively low withstand voltage are used, multiple thyristors can be connected in series and used in a high power supply voltage circuit, and moreover, no circuit constants or element components can be changed for line voltages of 400V and 200V. This can be done without any changes. Furthermore, since a transformer is not used, the installation space is small and manufacturing is possible at low cost. It also has the advantage of being inexpensive and less prone to malfunctions against lightning surges and noise.

Embodiment Figure 1 is a circuit configuration diagram of an earth leakage and disconnection circuit that can handle high and low line voltages according to the present invention.
The figure is a wiring diagram of a high-voltage thyristor circuit in which a large number (three in the figure) of thyristors capable of handling a higher line voltage are connected in series. For convenience, Figure 3~
Assuming that the same symbols are used for the parts corresponding to FIG. 6, ZCT is a leakage current detection current transformer, AMP is an amplification shaping circuit, D is a power supply rectifier circuit, and TC is a trip coil. Furthermore, in this proposal, two thyristors SCR ₁ ,
Connect SCR ₂ in series and connect the anode side terminal to A.
The point cathode side terminal is the K point, and the width shaping circuit is
The output of AMP is sent from the G terminal through resistor _R5 on one side to the gate _G1 of the first thyristor _SCR1 on the other hand through resistor _R6.
are connected to the gate G ₂ of the second thyristor SCR ₂ via a diode D ₂ for preventing reverse current.
Other resistors are connected in parallel to thyristors SCR ₁ and SCR ₂ , respectively.
By connecting R ₁ and R ₂ and connecting the power supply rectifier circuit D to the amplifying shaping circuit AMP and the thyristor circuit SCR ₁ ,
Similar to FIG. 6, the power rectifying circuit D is applied to the amplifying shaping circuit AMP, which is used as the power supply for the SCR ₂ , via the dropper resistor R.

Next, the operation of the circuit shown in FIG. 1 will be explained. Now, when leakage current is detected by the leakage current detection current transformer ZCT, it is amplified and shaped by the amplification shaping circuit AMP to generate an output, which is applied to the gate G ₁ of the thyristor SCR ₁ through the resistor R ₅ . The gate current flows and the first
There is conduction between the anode A ₁ cathode K ₁ of thyristor SCR ₁ . Anode A ₁ of the first thyristor SCR ₁
is at the same potential as the cathode _K2 of the second thyristor _SCR2 , and if the anode _{A1 and} the cathode _K1 are in a conductive state, the cathode _K2 of the second thyristor SCR2 is also at the same potential as the cathode _K2 of the first thyristor _SCR1. It has almost the same potential as the cathode _K1 . Therefore the first thyristor
At the same time that the gate current flows to the gate _G1 of SCR ₁ , the gate current also flows to the gate _G2 of the second thyristor SCR ₂ through the resistor _R6 and the diode _D2 between the anode A ₂ cathode K 2 of the _second thyristor SCR ₂ . is also conductive. In other words, due to conduction between terminals AK, current flows to trip coil TC, and trip coil
The TC operates and opens the disconnector S to disconnect the AC line from the load side. 1st and 2nd thyristor
Second thyristor SCR when SCR ₁ and SCR ₂ are non-conducting
The gate G ₂ of is at approximately the same potential as the cathode K ₂ .
This potential is approximately half that between terminals AK, and if diode D ₂ is not present, it will be connected to the amplifying shaping circuit through resistor R ₆ .
There is a risk that current will flow into the gate _G1 of the AMP and the first thyristor _SCR1 , causing it to malfunction or break. Therefore the diode in this circuit
The role of _D2 is extremely large, and it is required to have diode characteristics with extremely low reverse leakage current, and at the same time, it is required to have performance equal to or higher than the withstand voltage of the first thyristor _SCR1 . The amplifying shaping circuit AMP is supplied with power from the power supply rectifying circuit D through the resistor R, and is considerably lower than the potential of _the gate _G2 of the second thyristor SCR2.
Generally, it has a noise malfunction prevention circuit, etc., so the output terminal G of the amplifying shaping circuit AMP that drives the first and second thyristors SCR ₁ and SCR ₂ is protected against lightning surges and noise flowing from the power line. It has become relatively unaffected.

In this way, the circuit according to the present invention can be used in a high voltage circuit by connecting multiple thyristors in series even if relatively low voltage thyristors are used, and moreover, the circuit constants and element parts can be changed in any way for line voltages of 400V and 200V. You can respond without having to do so. Moreover, since no transformer is used, the installation space is small and manufacturing is possible at low cost. Further, compared to the circuit shown in FIG. 6, it has the advantage of being stable against lightning surges and noise, and having fewer malfunctions. Furthermore, when dealing with a high voltage circuit or when using a thyristor with a low withstand voltage, in addition to the first and second thyristors SCR 1 and _{SCR 2 ,} a third thyristor SCR ₃ or as necessary is used. According to the 4th, 5th...
In addition, a resistor R ₃ corresponding to resistors R ₁ and R ₂ is connected in parallel with the thyristor SCR ₃ , and _{a diode D 3 for} preventing reverse current is connected to the resistor R ₅ ,
It can be used by providing R ₆ diode D ₂ correspondingly.

Effects of the invention As described above, this invention uses a relatively simple circuit configuration to connect thyristors in series up to the desired withstand voltage, making it easy to prevent leakage and disconnection in high-voltage power lines, and to manufacture the circuit at a low cost. be able to.

[Brief explanation of the drawing]

Figure 1 is a circuit configuration diagram of the current leakage and disconnection circuit according to the present invention, Figure 2 is a circuit configuration diagram of the same part and other embodiments, and Figure 3
6 to 6 are diagrams of different conventionally known circuit configurations. In the figure, ZCT is a leakage current detection current transformer, AMP is an amplification shaping circuit, D is a power rectifier circuit, TC is a trip coil, SCR ₁ , SCR ₂ are thyristors, R ₁ , R ₂ , R ₅ ,
R ₆ is a resistor, D ₂ and D ₃ are diodes to prevent reverse current.

Claims (1)

[Scope of claim for utility model registration] (1) Line breaker S that opens and closes the AC line and load
a trip coil TC for driving the trip coil TC; and at least two first and second thyristors SCR connected in series so as to directly connect the anode of the first thyristor and the cathode of the second thyristor to drive the trip coil TC. ₁ , SCR ₂ , a resistor R ₁ connected in parallel to the thyristor SCR ₁ , a resistor R ₂ connected in parallel to the thyristor SCR ₂ , and a leakage current detection current transformer that can detect leakage current.
A leakage detection amplification and shaping circuit AMP amplifies and shapes the detection output of the ZCT, and the output of the leakage current detection amplification and shaping circuit AMP is connected to the thyristor SCR ₁ ,
In order to apply to the gates G ₁ and G ₂ of SCR ₂ respectively, the former is connected through a resistor R ₅ , and the latter is connected to a backflow prevention diode.
Connection circuit to D ₂ and the second thyristor mentioned above
Anode A of SCR ₂ and the first thyristor
A power supply rectifier circuit D that supplies power to the amplifying and shaping circuit AMP for detecting leakage current through the cathode K of the SCR ₁ and a resistor R. (2) The earth leakage or disconnection device as described in claim 1 of the utility model registration claim, which uses three or more thyristors connected in series.