KR19980703660A - AC power disconnect device - Google Patents

Abstract

Power cut-off device for AC mains with electrically conductive conductors and neutral conductors including a pair of comparators 10 and 12 for comparing the voltage drop to the electrically conductive conductor L with a threshold value of impedance S1 And the photorelay 15 corresponds to a comparator which turns off the triac 16 for disconnection of the conducting wire from the rod Z1 when the limit value is exceeded.

Description

AC power disconnect device

The present invention relates to an AC power cut-off device.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

1 shows a circuit diagram of an AC power interrupting device.

2 and 3 show a circuit diagram for searching for an alternate current path that is grounded by providing an input to the FIG. 1 circuit. And,

FIG. 4 shows an alternate disconnect circuit in the triac shown in FIG. 1.

According to the present invention, there is provided a power cut-off device for an AC main line having an electrically conducting lead and a neutral conducting wire, and the apparatus of the present invention limits the voltage drop of the electrically conducting or neutral in-conductance impedance. comparison means for comparing with value); And disconnection means responsive to the comparison means for disconnecting the conducting conductor from the neutral conductor when the limit value is exceeded, wherein the comparison means respectively comprises positive and negative input values, and A first and second comparator with outputs providing a signal that is estimated at a predetermined level when the voltage at the positive value exceeds the voltage at the negative input value, one side of the impedance being positive Is connected to the negative input of the second comparator and the negative input of the second comparator, the negative input of the first comparator and the positive input of the second comparator, respectively, via a voltage divider; The output of the second comparator is capable of responding to a predetermined level of signal.

In Fig. 1, the AC main line includes an electrically conducting L and a neutral N lead and a ground lead E having a AC voltage of 240 V supplied from a load Z1. The current detector S1 is inserted in series with the electrical lead L. The detector is designed to be 50 mV through the detector when the current reaches a predetermined overload current, 10 amp, at the electrical lead L, and is preferably disconnected from the load Z1. The current detector may consist of six to twelve winding S. W. G wires or a metal such as aluminum.

The AC power disconnect device includes two comparators 10 and 12, respectively, and may be supplemented by a TLC double comparator. One side of the current detector S1 is connected to the coupling of resistors R2 and R3 and the other side of the detector S1 is connected to the negative input of the comparator 10 and the positive input of the comparator 12, each decoupling. Via capacitor C1 and current limiting resistor R5. The four resistors R1 to R4 are connected between the DC voltage 12V and ground and have the values shown in FIG. These configurations of the threshold voltages at the positive input of comparator 10 and the negative input of comparator 12 have a point P as high as when a voltage of 50 mv is increased through either side of current detector S1 or through comparators 10, 12. To be high, tripping is triggered (depending on the effect of the positive or negative half-cycle).

The output O / P of the 555 timer 14 is in turn triggered and goes low for a predetermined period and from a photo relay 15 comprising a photodiode positioned adjacent to the phototransistor as shown in FIG. The supplied 12V DC voltage is removed. The triac 16 is inserted in series with the electrical conductor L and in the absence of an overload the phototransistor is conductive (since light is applied from the photodiode) and later the triac for controlling the CTL input of the triac for the normal conductor. As soon as (16) is disconnected, connect a voltage to the electrical conductor L. However, the removal of the DC voltage of 12V from the photo relay 15 causes the photodiode to be off and thus the phototransistor becomes non-conductive by removing the control voltage from the triac 16. As a result, the triac 16 is nonconductive and disconnects power from the load Z1. Triac 16 may be of type TIC 246M and may be replaced to handle overload and be a reactive load as well as a switching derivative. The 100mH inductor L1 is connected in series with the electrical lead L to reduce interference at the triac's output.

If a short circuit caused by an increase in the overload current still exists after the 555 timer 14 finishes its timing mode, the power supply is turned off because the P point is still high. However, once the short circuit is corrected and the outputs of the comparators 10 and 12 are low, the timer 14 is stopped and an alternating voltage of 12 V is applied to the photo relay 15 and the triac 16 once again. The switch is switched on again to save power to load Z1.

In addition to disconnecting power from overload currents that can be caused by equipment faults or short circuits, the device also provides a circuit path for alternative currents, that is, if the current path is different for ground rather than through ground wire E. It includes a circuit (Figs. 2 and 3) for turning off the power when the place is to be traversed. This can occur when a person touches a point where electricity flows on the equipment.

Therefore, referring first to FIG. 2, the toroidal ferromagnetic core 20 has three windings W1, W2 and W3. The winding W1 is connected in series with an electrically conducting lead L, the winding W2 is connected in series with the neutral conductor N, and the winding W3 is connected in series with the earth conductor E. The current flow in either of the windings W1 to W3 induces eddy currents in the core 20. However, the windings are designed so that the current in the conducting lead is exactly equal to the sum of the currents of the neutral and earth leads N and E so that the three windings cancel out, leading to an eddy current in the core 20.

However, there must be an alternative current path, such as provided by human contact at the point where the current passes, and the sum of the currents in the neutral and earth leads N and E is less than the current in the live leads L, so that the core 20 Eddy current flows in This net current flow is detected by the Hall effect device 20 located within the toroidal core 20. Hall effect device 20 provides an alternating voltage at output 24 of amplitude approximated in proportion to the amplitude of the eddy current flow in core 20.

The output 24 of the Hall effect device is connected to the circuit shown in FIG. 3 comprising two comparators 28, 30, such as comparators 10, 12 and can be supplemented by a double comparator TLC 272. The four resistors R6 to R9 are connected between DC voltage 12V and ground and form a limit voltage at the positive input of comparator 28 and the negative input of comparator 30. The output 24 from the hall effect device 20 is connected to both the negative input of the comparator 28 and the positive input of the comparator 30, and also to the junction of the resistors R7, R8.

The output of the comparator is connected to point P in FIG. Therefore, the threshold of one of the comparators exceeds the point P that becomes high (according to the positive or negative half period) and the load Z1 power source connected to FIG. 1 is cut off. Since the threshold setting in the comparators 28 and 30 can be set to very small values, only a few micro amps of current in the alternate path is devoted to the trigger of the comparator and the power is cut off.

4 shows an alternate disconnect circuit using a Wheatstone bridge instead of a triac 16.

In FIG. 4, the electrically conducting L and the neutral conductor N are connected to a pair of opposite corners of the Wheatstone bridge. That is, diodes D1 / D4 and D2 / D3 are respectively coupled, and the source-drain path of the n-type field effect transistor FET is connected to the other pair of opposing noses of the Wheatstone bridge. In other words, diodes D1 / D3 and D2 / D4 are respectively coupled. The gate of the FET is controlled by the output of the photo relay 15 similar to the triac control method in FIG.

Normal operation of the FET is normally maintained by the control voltage from the photo relay 15. A path through diodes D1, FET and diode D2 is provided at the positive half period of the FET mains, and a path through diodes D3, FET and diode D4 is provided at the negative half periods of the FET mains. In each case, the FET is in series with the load Z1 and the neutral conductor completes the path for the current from the conducting conductor through the load. As described above, only 0.9 V of voltage falls across each diode pair and FET during normal operation.

When a short circuit occurs, the P point becomes high, thereby removing the control voltage from the FET and turning off the optical relay as before. This prevents current from flowing from the conducting lead through the rod Z1 to the neutral lead.

The n-type FETs can be manufactured integrally with Wheatstone bridge circuits or as discrete components. The latter FET could be a Philips FET with a blocking voltage of 600v, a resistance of 0.1 ohms, and a switch speed of 200ns.

In the previous embodiment, although the current sensor S1 is connected in series to the electrically conducting conductor L, it may instead be connected to the neutral conductor N.

Claims (9)

In the AC mains power cut-off device having a live conductor and a neutral conductor, the device includes a comparison means for comparing the voltage drop of impedance with a limit value in a live or neutral conductor and when the limit value is exceeded. And a disconnection means responsive to the comparison means for disconnecting the conducting conductors from the neutral conductor, wherein the comparison means each comprises a positive input value, a negative input value, and a voltage at a positive value. A first and a second comparator with outputs that provide a signal estimated at a predetermined level when the voltage at a negative input value is exceeded, one side of the impedance being the positive input of the first comparator and the second comparator; The negative input of the first comparator and the second comparator, respectively, connected via a voltage divider Connected to the positive input and disconnection means includes first and second AC power supply, characterized in that in response to a signal of a predetermined level at the output of the second comparator block unit. 2. An AC mains line according to claim 1, wherein the AC mains comprises electrically conducting wires, neutral wires and earth wires, wherein the device is characterized by a difference between the sum of the current flowing in the live wire and the current flowing in the earth wire and the neutral wire. Additional means for providing another signal upon which it depends; And comparing means for comparing the amplitude of the another signal with a limit value, and if the limit value is exceeded, means for disconnecting the conducting conductor from the neutral conductor. 3. The method of claim 2, wherein the additional means comprises a closed loop ferromagnetic core having three windings each connected in series to an electrically conducting conductor, a neutral conductor and an earth conductor, wherein the current of the conducting conductor is a neutral conductor. And the net flow of eddy currents in the core is a predetermined value when equal to the sum of the currents of the earth leads, wherein the means for providing the additional signal corresponds to the net flow of eddy currents in the core. Blocking device. 4. The AC power supply disconnect device according to claim 3, wherein the means for providing an additional signal is a hall effect device. 5. A method according to claim 2, 3 or 4, wherein the further comparison means is estimated at a predetermined level when the voltage of the positive and negative input portions and the positive input portion exceeds the voltage of the negative input portion. A third and fourth comparator with outputs for providing a signal, the signal coming from said further means being connected to the positive input of the third comparator and the negative input of the fourth comparator, The signal is connected via the respective voltage divider to the negative input of the third comparator and the positive input of the fourth comparator, and disconnection means reacts to the signal at the predetermined level of the output of one of the third and fourth comparators. AC power cut off device characterized in that. The photovoltaic device according to any one of claims 1 to 5, wherein the disconnection means is connected to a photosensitive device that is normally maintained in a conductive state by a light source that emits light rays adjacent to the optical sensor, and to a control voltage provided via the conductive photosensitive device. And a switching device in series with an electrically conducting lead that is normally kept closed by the device, wherein the device for emitting light rays blinks in response to a signal from a comparing means such that a control voltage is removed from the switching device and the switching device An AC power cut-off device, characterized in that for disconnecting a conductive wire from a neutral conductive wire. 7. The AC power interrupting device according to claim 6, wherein the switching device is a triac. 7. The method of claim 6, wherein electrically conductive and neutral conductors are connected across the first pair of opposite corners in the Wheatstone bridge, and the switching device is connected across the other pair of opposite corners of the Wheatstone bridge. AC power disconnect device. 9. A timer according to any one of the preceding claims, comprising a timer for providing an output signal which is triggered by a signal from the first comparing means or other comparing means and lasts for a predetermined period of time, wherein the disconnection means comprises the timer output. AC power cut off device, characterized in that for reacting to the signal.