JP2005317218A - Earth leakage breaker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of shortening charging time in a power source capacitor in a configuration for driving a trip coil by energy stored in the power source capacitor for a control circuit in an earth leakage breaker. <P>SOLUTION: In the earth leakage breaker, an AC power supply is applied to a bridge rectifier circuit 7 via a current-limiting resistor 11, and the power source capacitor 10 and an operation control circuit 3 are connected to the output terminal of the bridge rectifier circuit 7. The current-limiting resistor 11 is composed of a circuit element or a means of which the resistance value is rapidly increased in accordance with temperature rise as in a positive temperature coefficient thermistor. As a result, the charging time to the power source capacitor can be shortened while a current consumption in continuous use is suppressed, by changing the value of current supplied to the control circuit from the AC power supply in continuous use when the power source capacitor is charged and that after the charging is completed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a leakage breaker that detects a leakage in a load circuit and cuts off its power supply.

FIG. 2 is a connection diagram disclosed in Japanese Patent Application Laid-Open No. 2-97220 as an example of a conventional earth leakage breaker. The secondary coil of the zero-phase current transformer 2 inserted in the electric circuit 1 is connected to the input terminal of the operation control circuit 3, and the output terminal of the operation control circuit 3 is connected to the gate of the thyristor 4. The thyristor 4 is connected in series with the trip coil 6 of the switching contact 5 inserted in the electric circuit 1. On the other hand, the input end of the bridge rectifier circuit 7 is connected to the electric circuit via the current limiting resistor 8, and the output end of the bridge rectifier circuit is connected to charge the power supply capacitor 10 via the current limit circuit 9. The operating circuit comprising the trip coil and the thyristor is connected to both ends of the power supply capacitor. When a leakage or ground fault occurs on the load side of the circuit, a zero-phase current flows in this circuit, a voltage is generated in the secondary coil of the zero-phase current transformer, and it is amplified by the operation control circuit. When the set value is exceeded, the output voltage is applied to the gate of the thyristor, so that the thyristor is ignited, the trip coil is energized and the switching contact is interrupted. The trip current of the trip coil is mostly the discharge current of the power supply capacitor. The current limit circuit is intended to expand the operating voltage range of the power supply that supplies power to the circuit.By keeping the current consumption almost constant, the power supply voltage rating can be increased without increasing the current capacity of the current limit resistor. A wide range is available.
JP-A-2-97220

  As described above, when the current limiting circuit that makes the charging current to the power supply capacitor almost constant is used, the time required for the charge necessary to drive the trip coil to be stored in the power supply capacitor is the capacity of the power supply capacitor, It is determined by the current value limited by the current limiting circuit. That is, the time required for a certain amount of energy for driving the trip coil to be stored in the power supply capacitor is governed by the current value limited by the current limiting circuit. As a problem that arises from this, it is better that the amount of energy for driving the trip coil stably is better, and for this purpose, it is necessary to increase the amount of charge stored in the power supply capacitor, while on the other hand, In terms of characteristics, there is a conflicting requirement that it is better that the time until the charge amount that can drive the trip coil is completed in the power supply capacitor is shorter. In other words, if an earth leakage occurs immediately after the earth leakage circuit breaker is turned on, it is better to be in a state where the interruption operation can be performed immediately. Therefore, it takes a long time to accumulate a charge amount that can be cut off, and the operation time is delayed. It is very difficult to reduce the charging time until the trip coil can be driven while maintaining the power supply capacitor capacity necessary for stable driving of the trip coil.

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to provide an earth leakage circuit breaker with a short charging time for a power supply capacitor.

  In order to solve the above-described problems, the present invention provides an electric circuit provided with an open / close contact, a bridge rectifier circuit connected to the electric circuit via a current limiting resistor, and an output terminal of the bridge rectifier circuit. Power supply capacitor, an operation control circuit connected in parallel with the power supply capacitor, and a leakage circuit having a trip coil that is connected to the operation control circuit and disconnects the switching contact by the energy accumulated in the power supply capacitor to cut off the electric circuit In this case, the current limiting resistor is constituted by a circuit element or means whose resistance value rapidly increases as temperature rises.

  According to the present invention, when a short circuit occurs immediately after the leakage circuit breaker is turned on, the power supply capacitor that operates the trip coil is rapidly charged, so that the delay of the leakage trip operation time can be improved. Can do. Further, the circuit configuration is simplified, and the cost can be further reduced.

Embodiments will be described below with reference to the drawings. FIG. 1 shows a connection diagram of an earth leakage breaker in one embodiment of the present invention. The earth leakage breaker of the present embodiment is connected to the electric circuit 1 provided with the switching contact 5, the bridge rectifier circuit 7 connected to the electric circuit 1 via the current limiting resistor 11, and the output terminal of the bridge rectifier circuit 7. Power supply capacitor 10, the operation control circuit 3 connected in parallel with the power supply capacitor 10, and the switching contact 5 is pulled off by the energy stored in the power supply capacitor 10 connected to the operation control circuit 3. An earth leakage circuit breaker having a trip coil 6 for interrupting, wherein the current limiting resistor 11 is constituted by a circuit element or means whose resistance value increases rapidly as the temperature rises, such as a positive temperature coefficient thermistor. . A zero-phase current transformer 2 is attached to the electric circuit 1 and its secondary coil is connected to the input terminal of the operation control circuit 3. The output terminal of the operation control circuit 3 is connected to the gate of the switching element 4, and the switching element 4 is connected in series with the trip coil 6. A thyristor or the like is used as the switching element 4.
The operation of the power supply circuit is as follows. When the AC power supply is applied to the bridge rectifier circuit through the current limiting resistor 11 in a state where the power supply capacitor 10 is not charged, a large current due to the initial low resistance of the current limiting resistor 11 flows in the initial period when the voltage is applied, The power capacitor is charged rapidly. In a steady state, the current limiting resistor 11 suddenly becomes high resistance due to temperature rise due to self-heating due to energization, and supplies an operation control circuit current suppressed to a necessary minimum.

Since the charging time of the power supply capacitor is short, it is not necessary to use a component having a large rated power as the circuit component. According to the present embodiment, the current consumption in the continuous use state can be suppressed to the minimum necessary while shortening the charging time of the power supply capacitor. In order to optimize this characteristic, a resistor may be connected in series or in parallel with the current limiting resistor 11.
In addition, since the circuits after the bridge rectifier circuit are driven at a constant voltage regardless of changes in the applied voltage, the bridge rectifier circuit and the like can be configured with low voltage elements, the conductor pattern gap of the printed circuit board can be reduced, and the printed circuit board can be made smaller. it can. Further, since the test circuit can be configured on the primary side of the rectifier circuit, a constant test current can be obtained regardless of the circuit voltage, and a test suitable for the sensitivity current is possible.

It is a circuit diagram of the earth-leakage circuit breaker in one Example of this invention. It is a circuit diagram of the earth-leakage circuit breaker of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric circuit 2 Zero phase current transformer 3 Operation control circuit 4 Switching element 5 Switching contact 6 Trip coil 7 Bridge rectifier circuit 10 Power supply capacitor 11 Current limiting resistor

Claims (1)

An electric circuit provided with a switching contact, a bridge rectifier circuit connected to the electric circuit via a current limiting resistor, a power supply capacitor connected to the output terminal of the bridge rectifier circuit, and a power supply capacitor connected in parallel In an earth leakage circuit breaker having an operation control circuit and a trip coil connected to the operation control circuit and disconnecting the switching contact by the energy stored in the power supply capacitor to interrupt the electric circuit, the temperature of the current limiting resistor is increased. A circuit breaker comprising a circuit element or means whose resistance value suddenly increases with the circuit element.

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