JPS6233484Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an improvement in a current leakage and disconnection limiting device that operates to open the main circuit when the magnitude of the ground fault current in the main circuit exceeds a predetermined value.

A conventional electric leakage and disconnection limiting device is shown in FIG. In the figure, reference numeral 1 denotes an electromagnetic tripping coil, which is energized when a ground fault occurs in external electric circuits 2a and 2b, and opens contact portions 3a and 3b via a shearing mechanism (not shown). Reference numeral 4 denotes a surge absorber, which is connected via the electromagnetic trip coil 1 between the phases of the main circuits 5a and 5b. That is, the electromagnetic trip coil 1 and the surge absorber 4 are connected in series to the main circuits 5a and 5b. 6 is a zero-phase current transformer, which connects the main circuits 5a, 5
This is to detect the ground fault current in the external electric circuits 2a and 2b via the terminal b. 7 is an amplifier circuit, and a zero-phase current transformer 6
Amplifies the ground fault current signal from and outputs it. 8 is a rectifier circuit that supplies direct current to the amplifier circuit 7 and a semiconductor switching element (hereinafter thyristor 9), which will be described later.
It is connected in parallel with the surge absorber 4 described above. Reference numeral 9 denotes a thyristor, which becomes conductive when the output of the amplifier circuit 7 exceeds a predetermined value, and the electromagnetic trip coil 1 is energized.

Next, the operation will be explained. In the device configured as described above, if a ground fault occurs in the external circuit 2a or 2b, the forward current and return current of the main circuits 5a and 5b will be different, and the voltage will be applied to the secondary winding of the zero-phase current transformer 6. is induced. This voltage is amplified by the amplifier circuit 7 and becomes the gate input of the thyristor 9, and if it is equal to or higher than a predetermined value, the thyristor 9 is turned on.

On the other hand, the electromagnetic tripping coil 1 connected to the main circuits 5a and 5b is energized via the rectifier 8 due to the conduction of the thyristor 9, and a shearing mechanism (not shown) operates to close the contact. 3a and 3b are opened. Next, when an excessive shock wave voltage of a very high frequency is applied to the main circuits 5a and 5b, this voltage is divided into electromagnetic trip coils 1 and applied to the surge absorber 4. Therefore, the rise of the shock wave voltage is blunted by the action of the rear aftance component of the electromagnetic trip coil 1, and the voltage limiting action of the surge absorber 4 is effectively performed. At this time, it is clear from the circuit diagram that the current bypassed by the surge absorber 4 flows through the electromagnetic tripping coil 1 and is limited by its impedance. By the way, according to the standards for electric leakage and disconnection (JIS C 8371, JEM 1244, etc.), shock wave inoperability performance is guaranteed.
According to this regulation, when a standard shock wave voltage waveform of 1 x 40us and 6kV is applied, no leakage or disconnection shall occur. However, the surge current bypassed by the surge absorber 4 as described above flows into the electromagnetic tripping coil 1, energizes it and operates the shearing mechanism, and the contact portions 3a, 3
b is released. That is, it has a drawback that it cannot guarantee that shock waves will not operate as specified in the standards. In addition, since the electromagnetic trip coil 1 is generally designed to operate at about 80% of the rated voltage of the main circuits 5a and 5b, even if the duration of the surge current due to shock wave voltage application is short, the peak value is sufficient. Because of its large size, the electromagnetic trip coil 1 has the disadvantage that it operates almost equivalently to when it is excited by an overvoltage.

This invention was made to eliminate the drawbacks of the conventional ones as mentioned above, and the purpose is to add a limiting impedance to the surge current circuit to provide a shock wave non-operating type earth leakage and disconnection. It is something.

An embodiment of this invention will be described below with reference to FIG. In the figure, reference numeral 10 denotes a current limiting impedance, which is connected in series to the surge absorber 4. However, this limiting impedance 10
The series circuit of surge absorber 4 and surge absorber 4 is main circuit 5.
A and 5b are connected in series with the electromagnetic trip coil 1 and in parallel with the rectifier circuit 8. As detailed in FIG. 3, the limiting impedance 10 has a four-terminal structure by dividing the electromagnetic tripping coil 1, L ₁ -L ₄ are used for the electromagnetic tripping coil 1, and L ₂ −L ₃ is used as the limiting impedance 10. Generally, the electromagnetic trip coil 1 has an iron core structure, so that a large inductance of L ₂ -L ₃ can be easily obtained even with a smaller number of turns than an air core. Note that L ₁ -L ₄ are designed so that the electromagnetic trip coil 1 operates at 80% or less of the rated voltage of the main circuits 5a and 5b. Further, the limiting impedance 10 limits the bypass current of the surge absorber 4 when a predetermined shock wave voltage is applied to a peak value at which the electromagnetic tripping coil 1 does not operate.
L ₂ −L ₃ is designed.

Descriptions of other symbols are omitted because they are completely the same as those of the conventional device. In the device configured as described above, when a ground fault occurs in the external circuit 2a or 2b, a voltage is induced in the secondary winding of the zero-phase current transformer 6, similar to the conventional device described above, and the amplifier circuit 7 The signal is amplified by the thyristor 9 and becomes the gate input of the thyristor 9. If this input is above a predetermined value, the thyristor 9 is made conductive, and the electromagnetic trip coil 1 is
energized by the voltage rectified by the rectifier circuit 8, the shearing mechanism (not shown) operates and the contact portion 3
a and 3b are opened. At this time, surge absorber 4 does not operate, so the limiting impedance is 10.
has no effect. Next, although no ground fault has occurred, if an excessive shock wave voltage of a very high frequency is applied to the main circuits 5a and 5b, such as from a lightning surge, that voltage will be applied to the electromagnetic trip coil 1 and the limiting coil. The voltage is divided by the impedance 10 and applied to the surge absorber 4. For this reason,
The rise of the shock wave voltage is blunted by the action of the reactance component of the electromagnetic trip coil 1 and the limiting impedance 10, and the voltage limiting effect of the surge absorber 4 is sufficiently performed. At this time, the current bypassed by the surge absorber 4 is limited by the sum of the impedance of the electromagnetic trip coil 1 and the limiting impedance 10, as is clear from FIG. Since the electromagnetic trip coil 1 is generally designed to operate at 80% or less of the rated voltage, once the specifications are determined, the bypass current of the surge absorber 4 is automatically determined and it is difficult to set it to an arbitrary value. , limiting impedance 1
0 is installed independently of the electromagnetic trip coil 1, so the bypass current can be set to any value. That is, by arbitrarily designing the size of the limiting impedance 10, the bypass current can also be arbitrarily set. Therefore,
For example, it is possible to design a coil in which the electromagnetic trip coil 1 does not operate at a shock wave voltage of 1 x 40 us and 6 kV, but operates at 1 x 40 us and 8 kV. This means that the shock wave voltage is extremely high (e.g. 1×
40 us, 10 kV) enters the main circuits 5a and 5b, the current bypassed by the surge absorber 4 energizes the electromagnetic trip coil 1 with sufficient current, so the trip mechanism (not shown) operates. As a result, the contact portions 3a and 3b are opened, and thermal damage to the surge absorber 4 can be prevented.

Furthermore, the electromagnetic trip coil 1 may become conductive when the surge absorber 4 becomes conductive due to an initial defect or deterioration of the surge absorber 4, or when the rectifier circuit 8, thyristor 9, amplifier circuit 7, etc. malfunction. It goes without saying that the electromagnetic tripping coil 1 will self-protect the device in such a case since it will naturally be energized in such a case.

In the above embodiment, a 4-terminal coil was explained, but as shown in Fig. 4, in the case of a 3-terminal coil, L ₁ - L ₂ are used for the electromagnetic tripping coil 1, and L ₂ - _{L 4} are used for current limiting. The same effect can be obtained even if it is used as an impedance.

In addition, as shown in Fig. 5, the coils L ₂ −L ₃ are
If connected differentially with L ₁ −L ₄ , the coils L ₂ −L ₃ will be
By limiting the bypass current of the surge absorber 4 and at the same time canceling the attractive force of the electromagnetic tripping coil 1, the operation against shock wave voltage can be suppressed more effectively.

As described above, in this invention, between the rectifier circuit and the main circuit, the series circuit of the surge absorber and the limiting impedance is connected in parallel with the rectifier circuit, and in series with the electromagnetic trip coil with respect to the main circuit. When operating against ground fault current in a steady state (rated frequency, rated voltage applied), the current in the electromagnetic tripping coil is not limited by the limiting impedance, and a surge occurs only when sufficient force is obtained and shock wave voltage is applied. Due to the operation of the absorber, it is inserted in series with the electromagnetic tripping coil of the limiting impedance and is configured to limit the coil current (bypass current), so at a predetermined shock wave voltage, the electromagnetic tripping coil is The trip coil is not energized with sufficient current so that the contacts do not open. That is, a shock wave non-operating type earth leakage or disconnection device specified in the standard can be obtained. In addition, if a shock wave voltage that greatly exceeds a predetermined value is applied, the bypass current of the surge absorber will also increase, and the electromagnetic tripping coil will be energized with a sufficient current, causing the disconnection mechanism to operate and close the contact. is opened and thermal damage to the surge absorber can be prevented. In addition, since the bypass current is limited to a small value by the sum of the impedance of the electromagnetic trip coil and the limiting impedance, aging deterioration of the surge absorber is suppressed and its lifespan is greatly improved, which also allows the surge absorber to be made smaller. effective. Furthermore, by using the iron core for the electromagnetic trip coil provided inside the leakage or disconnection circuit as a limiting impedance, a small and large-capacity inductance can be easily obtained, creating a special space for the leakage or disconnection. This has the effect of eliminating the need for the device and allowing it to be made more compact.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing the structure of a conventional earth leakage circuit breaker, Figure 2 is a circuit diagram of an earth leakage circuit breaker that shows one embodiment of this invention, and Figure 3 is a circuit diagram showing the main points of this invention. FIG. 4 is a configuration diagram of a trip coil showing an example of a certain limiting impedance. FIG. 4 is a configuration diagram of a trip coil showing another embodiment. FIG. It is a connection diagram. In the figure, 1 is an electromagnetic trip coil, 4 is a surge absorber, 6 is a zero-phase current transformer, 7 is an amplifier circuit, 8 is a rectifier circuit, 9 is a thyristor, and 10 is a limiting impedance. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims for Utility Model Registration] (1) A semiconductor switching element that conducts when the magnitude of the ground fault current in the main circuit exceeds a predetermined value, and rectifies the current supplied from the main circuit when the semiconductor switching element conducts. a rectifier circuit that energizes the semiconductor switching element; between this rectifier circuit and the main circuit, a series circuit of a surge absorber and a current limiting impedance is connected in parallel to the rectifier circuit and between phases of the main circuit; an electromagnetic tripping coil connected between a series circuit of the surge absorber and the limiting impedance, one end connection of the rectifier circuit and one phase of the main circuit, and dividing the electromagnetic tripping coil. An earth leakage or disconnection device with at least three terminals, one used as an electromagnetic trip coil and the other used as a current limiting impedance. (2) The scope of the above utility model registration claim in which the electromagnetic trip coil is divided into four terminals, one of which is used as the electromagnetic trip coil and the other is used as a current limiting impedance, and both coils are differentially connected. Electrical leakage or disconnection as described in paragraph 1.