JPS6211158Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an earth leakage interrupting device that interrupts a power transmission line when a certain earth leakage current occurs in electrical equipment or electrical wiring to prevent accidents such as fire or electric shock.

FIG. 1 shows a conventional earth leakage interrupter. In FIG. 1, an iron core 1, a coil 2, and power transmission lines 3 and 4 constitute a current transformer that transforms the difference current between the round trip and the transmission current to the coil 2. 6 is a noise absorption capacitor, 7
8 is an amplifier, and 8 is a rectifier, which amplifies and rectifies the output of the coil 2 and leads it to a capacitor 9. The voltage across the capacitor 9 is input to the voltage discriminator 11 via the filter 10, and once the voltage discriminator 11 detects a leakage current, the voltage discriminator 11 maintains the leakage detection operation and interrupts the power transmission line by the relay 5.

However, in this conventional example, when attempting to increase the response speed of the earth leakage cutoff, the filter 10 does not absorb enough noise, resulting in frequent malfunctions, and once a malfunction occurs, the earth leakage cutoff operation must be manually restored. However, it had the disadvantage of being inconvenient to use.

The present invention eliminates the above-mentioned drawbacks of the prior art and provides an earth leakage interrupting device that automatically returns to its original state even if it once performs an interrupting operation in response to instantaneous noise.

The present invention will be explained below using the embodiment shown in FIG. The iron core 1, the coil 2, and the power transmission lines 3 and 4 constitute a current transformer that transforms the difference current between the transmission currents to the coil 2, as shown in FIG. If a current leakage occurs on the power receiving side, a difference will occur in the current flowing back and forth between the power transmission lines 3 and 4. This transformed differential current is applied to the noise absorbing capacitor 6 and simultaneously input to the amplifier 7, rectified by the rectifier 8, and input to the capacitor 9. The charging voltage of capacitor 9 is input to Schmitt trigger circuit 12 . As shown in FIG. 3, this Schmitt trigger circuit 12 has an input characteristic in which it is turned on at level H and turned off at level L. By the output of the input of the Schmitt trigger circuit 12, the power transmission line is cut off by the relay 5, and the capacitor 9 is charged by the current generating circuit 13.

The operation when a leakage occurs will be described using FIG. FIG. 4A shows the voltage across the capacitor 9.
The current generated in the coil 2 due to the leakage is amplified and rectified by the amplifier 7 and the rectifier 8, and the voltage across the capacitor 9 is increased. When this voltage exceeds the first operating level H of the Schmitt trigger circuit 12, its output (FIG. 4B) opens the relay 5, cutting off the power transmission line, and at the same time charging the capacitor 9 from the current generating circuit 13. It will be done. When there is no charging current from this current generating circuit 13, the voltage of the capacitor 9 will change as indicated by the broken line in _FIG . The second operation level L is reached. This cancels the power transmission interruption. However, by providing the current generating circuit 13 as described above, the voltage across the capacitor 9 becomes as shown by the solid line in FIG. 4A, and power transmission interruption is maintained.

Next, the operation against noise will be explained with reference to FIG. Here, a capacitor has the property that a voltage is generated across the capacitor even when there is no charged charge in response to a short pulse, and when the pulse disappears, the voltage across the capacitor disappears. This occurs because the capacitor does not act as an ideal capacitor at high frequencies. Now, pulse noise has entered the capacitor 9 as shown in Figure 5A.
When the voltage across the terminal becomes higher than the first operation level H of the Schmitt trigger circuit 12 due to the above-mentioned reason, the Schmitt trigger circuit 12 operates and generates the power transmission circuit cutoff signal shown in FIG. 5B, and the power transmission is cut off by the relay 5. A charging current flows from the current generating circuit 13 to the capacitor 9. As mentioned above, the voltage across the capacitor due to a short time pulse disappears when the pulse disappears, so when there is no charging current from the current generating circuit 13, the voltage across the capacitor is as shown in FIG. 5A.
It decreases as shown by the broken line. Current generation circuit 1
Even when there is a charging current from 3, it decreases as shown by the solid line, reaches the second operation level L of the Schmitt trigger circuit 12, the power transmission interruption is canceled, and the state returns to the original state. Therefore, even if power transmission is temporarily cut off due to noise, it will return to normal when the noise disappears. When a large current leakage occurs next, the voltage across the capacitor 9 rises quickly. Therefore, when the noise is pulse-like, the voltage across the capacitor 9 drops when the noise disappears, but at this time, the signal current continues to flow, so the voltage across the capacitor 9 continues to rise, and the power transmission is cut off quickly. and maintain the shut-off state.

When the cause of the leakage is removed, the capacitor 9
By discharging the electric charge by an external switch, the output of the Schmitt trigger circuit 12 decreases and returns to its original state.

As explained above, according to the present invention, power transmission is temporarily cut off in response to pulse noise, but it returns to its original state when the noise disappears, so there is no need to manually restore power in response to noise operation. Become a vessel. Further, for the above reasons, when used in electrical appliances, it is effective as a highly sensitive and quick response earth leakage breaker. In the case of electrical appliances, temporary interruption of power transmission is often not a problem. Furthermore, it can be used as a general earth leakage breaker with high sensitivity and quick response. In addition, since the lock state does not occur due to noise malfunction, actual damage is unlikely to occur.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the configuration of a conventional earth leakage interrupter;
Fig. 2 is a diagram showing the configuration of an earth leakage interrupting device in an embodiment of the present invention, Fig. 3 is an input/output characteristic diagram of a Schmitt trigger circuit used in the device, Figs. 4A, B, and 5A, B are FIG. 2 is an explanatory diagram of the operation of the device of the present invention. 1... Iron core, 2... Coil, 3, 4... Transmission line, 7... Amplifier, 8... Rectifier, 9... Capacitor, 12... Schmitt trigger circuit, 13...
Current generation circuit.

Claims (1)

[Scope of utility model registration request] It has an electronic circuit that amplifies and rectifies the output of a current transformer into which a set of AC power transmission lines is input, leads the rectified output to a capacitor, inputs the voltage across this capacitor to a Schmitt trigger circuit, and Inputting the output of the Schmitt trigger circuit to the control terminal of the relay that opens and closes the electric circuit of the power transmission line,
An earth leakage interrupting device comprising a charging circuit that receives an output of the Schmitt trigger circuit and causes a charging current to flow through the capacitor.