JP2007323991A - Ground-fault interrupter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ground-fault interrupter applying high frequency leakage current measures which can prevent insulation deterioration and occurrence of disconnection of detecting winding of a zero-phase current transformer due to abnormal overheating of the zero-phase current transformer caused by high frequency leakage current. <P>SOLUTION: In the ground-fault interrupter 1 applying high frequency leakage current measures, a temperature detector 61 to detect temperature is installed on a zero-phase current transformer 3. Then, the detected temperature of this temperature detector 61 and a set temperature established beforehand is compared. When the detected temperature exceeds the set temperature, the ground-fault interrupter 1 is cut off by a temperature monitoring circuit 6 which gives a tripping signal to a tripping device 5, thereby, abnormal overheating of the zero-phase current transformer 3 is prevented. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an earth leakage circuit breaker for detecting an electric leakage or a ground fault occurring in a distribution system connected to an electric motor or other various loads, and preventing a ripple in advance, particularly a built-in zero phase current transformer for detecting an electric leakage. The present invention relates to an earth leakage circuit breaker that can protect the device from an abnormal temperature rise.

  The earth leakage breaker is generally configured as shown in FIG.

  The earth leakage breaker 1 shown in FIG. 5 includes a main circuit conductor 12 that connects the power supply side connection terminals R, S, and T and the load side connection terminals U, V, and W, and an open / close unit that opens and closes the main circuit conductor 12. 11 and all phases of the main circuit conductor 12 are inserted, and a zero-phase current transformer 3 for detecting a leakage current or a ground fault current flowing through the main circuit conductor, and a detection winding of the zero-phase current transformer 3 The leakage detection circuit 4 for monitoring the detected current 31 to determine whether there is a leakage or ground fault, and the opening / closing mechanism of the opening / closing portion 11 is tripped by the detection signal indicating the leakage of the leakage detection circuit 4. A tripping device 5 for blocking is provided. The power supply for the leakage detection circuit 4 and the trip device 5 is taken from the main circuit conductor 12.

  In such a leakage breaker 1, when an unbalanced current flows through the main circuit conductor 12 due to a leakage or a ground fault, a zero-phase current is detected from the detection winding 31 of the zero-phase current transformer 3, and is proportional to this current. The applied voltage is applied to the leakage detection circuit 4 via the detection resistor 32. When this detected voltage becomes larger than a preset set voltage, a leakage detection signal indicating the occurrence of leakage or the like is generated from the leakage determination circuit 42, and in response to this, a gate is connected to the thyristor switch 51 of the trip device 5 from the trigger circuit 43. A signal is given. As a result, the thyristor switch 51 is turned on, the electromagnetic trip mechanism 52 is activated, and the open / close section 11 is disconnected and disconnected by the open / close mechanism, and the power supply circuit and the load connected to the main circuit conductor 12 are leaked or leaked. Protect from ground faults.

  When such an earth leakage circuit breaker 1 is connected to a power supply circuit to a load having an inverter such as an induction motor 9 driven via the inverter 8, as shown in Patent Document 1, the inverter 8 As a result of the high-frequency switching operation, a high-frequency leakage current is generated via the stray capacitance of the power supply circuit, which flows through the main circuit conductor 12 and is detected by the zero-phase current transformer 3. When the high-frequency leakage current becomes larger than the set value, the determination circuit 42 detects the occurrence of a leakage, and the load breaker is disconnected even though the switching unit 11 of the leakage breaker 1 has no leakage or ground fault. Will be made.

In order to eliminate such inconvenience, conventionally, as shown in FIG. 5, a low-pass filter 41 is provided at the entrance of the determination circuit 42 of the leakage detection circuit 4 to prevent high-frequency leakage current flowing to the determination circuit, Unnecessary interruption operation due to high-frequency leakage current is prevented from being performed (see Patent Document 1).
Japanese Patent Laid-Open No. 05-015046

  However, if it is used in a power supply circuit to a load equipped with an inverter via a leakage breaker with such a countermeasure against high-frequency leakage current, an unnecessary interruption operation due to high-frequency leakage current can be prevented. Since the high-frequency current flows superimposed on the conductor 12, a large iron loss occurs in the iron core 33 of the zero-phase current transformer 3, and thus the temperature of the zero-phase current transformer 3 may rise abnormally. Leakage detection function is not possible due to deterioration of insulation of detection winding 31 of zero-phase current transformer due to abnormal rise in temperature or disconnection of detection winding due to difference in thermal expansion coefficient between insulating resin and winding Thus, there arises a disadvantage that the earth leakage circuit breaker does not function.

  The present invention eliminates inconveniences in an earth leakage circuit breaker with such a countermeasure against high frequency leakage current, and can prevent occurrence of insulation deterioration and disconnection of a detection winding due to a temperature increase of a zero-phase current transformer. It is an object to provide a circuit breaker.

In order to solve the above problems, the invention according to claim 1 is directed to a three-phase main circuit conductor, an opening / closing part for opening / closing the main circuit conductor, and a zero-phase current transformer for detecting a leakage current of the main circuit conductor. A leakage detection circuit for determining the occurrence of leakage from the output of the detection winding of the zero-phase current transformer, and the main circuit by tripping the open / close unit by an output signal indicating the occurrence of leakage in the leakage detection circuit In the earth leakage circuit breaker provided with the trip device for interrupting
The temperature detector for detecting the temperature of the zero-phase current transformer is compared with the detected temperature of the temperature detector and a preset temperature. When the detected temperature exceeds the preset temperature, the trip device is A temperature monitoring circuit for providing a trip signal is provided.
The invention according to claim 2 is characterized in that, in the invention according to claim 1, the temperature monitoring circuit operates the alarm device when the detected temperature exceeds the set temperature.

  According to the present invention, the temperature detector that detects the temperature of the zero-phase current transformer of the earth leakage breaker is compared with the detected temperature of the temperature detector and a preset temperature, and the detected temperature exceeds the preset temperature. A temperature monitoring circuit that generates a monitoring output at the time, and the output of this temperature monitoring circuit activates a trip device to shut off the load circuit or activates an alarm device to issue an alarm. Therefore, when the high-frequency current flows through the zero-phase current transformer and the temperature rises abnormally, the earth leakage circuit breaker is automatically activated, or the load operation is stopped based on the alarm signal. As a result, the temperature increase of the zero-phase current transformer due to the high-frequency current flowing in the zero-phase current transformer can be suppressed, so that the insulation deterioration of the zero-phase current transformer and the disconnection of the detection winding can be prevented. And this can prevent the leakage detection function of the leakage breaker from stopping.

  Embodiments of the present invention will be described below with reference to examples shown in the drawings.

  FIG. 1 is a block diagram of an earth leakage circuit breaker showing an embodiment of the present invention. Since the basic configuration of the earth leakage breaker of the present invention is the same as that of the conventional earth leakage breaker shown in FIG. 5, the same elements are denoted by the same reference numerals and the description thereof is omitted.

  The earth leakage breaker 1 of FIG. 1 of the present invention is different from the conventional earth leakage breaker of FIG. 5 in that a temperature detection newly attached to the current transformer 3 in order to detect the temperature of the zero-phase current transformer 3. And a temperature monitoring circuit 6 comprising a temperature determination circuit 62 that monitors the detected temperature from the temperature detector 61 and generates an output signal when the detected temperature exceeds a preset temperature. I have just done it. The output signal of the temperature determination circuit 62 of the temperature monitoring circuit 6 is applied to the trigger circuit 43 in parallel with the output signal of the leakage determination circuit 42 of the leakage detection circuit 4. As the temperature detector 61, various thermistors, transistors, diodes, and other various temperature sensors can be used.

  Such an earth leakage breaker 1 of the present invention is installed in a power supply circuit to an induction motor 9 driven via an inverter 8, and a high-frequency leakage current accompanying a high-speed switching operation of the inverter 8 is caused via a stray capacitance of the power supply circuit. When the current flows through the main circuit conductor 12 of the earth leakage circuit breaker 1, a large iron loss occurs due to the formation of a magnetic flux based on this high-frequency current in the iron core 33 of the zero-phase current transformer 3, thereby causing a zero-phase change. Since the flow device 3 is heated, its temperature rises.

  Thus, the temperature of the zero-phase current transformer 3 whose temperature has risen is detected by the temperature detector 61, and the magnitude thereof is compared with a preset temperature set in the temperature determination circuit 62 and exceeds the preset temperature. Sometimes an output signal is generated indicating an abnormal temperature. When this output signal is applied to the trigger circuit 43, a gate signal is applied to the thyristor switch 51 of the trip device 5, so that it is turned on. When the thyristor switch 51 is turned on, the electromagnetic trip mechanism 52 of the trip device 5 is actuated to trip the open / close mechanism of the open / close section 11 and open it to cut off the main circuit conductor 12, and the inverter 8, load The power supply to 9 is stopped.

  As a result, the inverter 8 stops operating, and the high-frequency leakage current flowing through the zero-phase current transformer 3 is interrupted. Therefore, heating of the zero-phase current transformer 3 due to the high-frequency current stops and the temperature becomes higher than that. Insulation deterioration due to overheating of the zero-phase current transformer 3 and disconnection of the detection winding are prevented, and even if the earth leakage breaker 1 is used in an environment where high-frequency leakage current is generated, the high-frequency leakage current Can protect against abnormal overheating.

  FIG. 2 is a circuit configuration diagram showing a specific first embodiment of the leakage detection circuit 4 and the temperature monitoring circuit 6 used in the leakage breaker 1 of the present invention.

  In FIG. 2, a voltage proportional to the zero-phase current is taken out from the detection resistor 32 connected to the detection winding 31 of the zero-phase current transformer 3. The high-frequency component contained in this voltage is blocked by the low-pass filter 41 composed of a resistor and capacitor T-shaped circuit, and only the low-frequency (commercial frequency) component is passed through the amplifier circuit 42-1 composed of the operational amplifier OP 1 by the operational amplifier OP 2. It is added to the configured first determination circuit 42-2. In this determination circuit, the low-frequency (commercial frequency) zero-phase current detection signal is compared with the set value S1, and an output signal is generated only during a period larger than the set value S1, and this signal is constituted by the transistor Tr and the capacitor C. The integrated circuit 42-3 is integrated. The integration value of the integration circuit is compared with the second set value S2 by the second determination circuit 42-4, and when it becomes larger than the set value S2, the trigger circuit 43-1 is driven. The trigger circuit 43-1 gives a gate signal to the gate of the thyristor switch 51 of the trip device 5.

  Thus, since the high-frequency current is blocked by using the low-pass filter 41 in the leakage detection circuit, malfunction due to the high-frequency leakage current is reduced. Then, by using the two determination circuits 42-2 and 42-4 and the integration circuit 42-3, it is possible to prevent malfunction due to a short-lived short-circuit leakage or a current imitating a ground fault current.

  As the temperature detector in the temperature monitoring circuit 6, a resistance temperature measuring element 61 whose resistance value changes according to a change in temperature is used, and this is pasted on the iron core of the zero-phase current transformer 3, and the zero-phase current transformer 3. Detect the temperature. A resistance change due to the temperature of the resistance thermometer element is converted into a voltage signal by a potentiometer including the resistance thermometer element 61 and the resistor R6, and applied to the temperature determination circuit 62 configured by the operational amplifier OP4. The temperature determination circuit compares the voltage signal indicating the temperature with the voltage S6 indicating the set temperature, and the trigger circuit 43-2 is driven when the detected temperature exceeds the set temperature S6. This trigger circuit is connected in parallel to the gate circuit of the thyristor switch 51 of the trip device 5.

  By configuring in this way, the leakage detection circuit 4 drives the tripping device 5 to break the leakage breaker 1 when leakage or ground fault occurs, and power is supplied from the leakage or ground fault to the load and the load. When the zero-phase current transformer of the earth leakage circuit breaker is heated due to high-frequency leakage current generated by an inverter or the like, the temperature monitoring circuit 6 detects this when the temperature rises abnormally. Since the tripping device can be driven to shut off the leakage breaker, the zero-phase current transformer of the leakage breaker can be protected from abnormal overheating.

  FIG. 3 shows a second embodiment. In this embodiment, a temperature alarm device 7 is connected to the output of the temperature monitoring circuit 6. An alarm lamp or an alarm buzzer can be used for the alarm device 72 of the alarm device 7. When the temperature monitoring circuit 6 operates and the trigger circuit 43-2 is driven when the temperature of the zero-phase current transformer 3 rises abnormally, a gate signal is given to the thyristor switch 71 of the temperature alarm device 7, so that this is turned on. Then, by operating the alarm device 72, it is notified that an abnormal temperature has occurred by turning on the alarm lamp or sounding the alarm buzzer. Based on this, it is possible to prevent the zero-phase current transformer from being further overheated by stopping the operation of the invar that is the source of the high-frequency leakage current.

  FIG. 4 shows a third embodiment in which the alarm relay 73 is driven by the temperature monitoring circuit 6 instead of driving the alarm lamp or alarm buzzer 72 of the temperature alarm device 7. By using the alarm relay 73 in this way, the output of the temperature monitoring circuit 6 can be taken out by the relay contact, so that it can be easily taken in as an alarm input of the control device.

It is a block block diagram which shows the earth-leakage circuit breaker of the Example of this invention. It is a circuit block diagram which shows the 1st Example of the internal circuit of the earth leakage circuit breaker by this invention. It is a circuit block diagram which shows the 2nd Example of the internal circuit of the earth leakage circuit breaker by this invention. It is a circuit block diagram which shows the 3rd Example of the internal circuit of the earth leakage circuit breaker by this invention. It is a block block diagram which shows the conventional earth-leakage circuit breaker.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1: Leakage breaker 11: Switch part 12: Main circuit conductor 3: Zero phase current transformer 31: Detection winding 4: Leakage detection circuit 41: Low-pass filter 5: Trip device 6: Temperature monitoring circuit 61: Temperature detection 62: Temperature judgment circuit 7: Temperature alarm device 8: Inverter 9: Induction motor

Claims (2)

A three-phase main circuit conductor, an open / close unit that opens and closes the main circuit conductor, a zero-phase current transformer that detects a leakage current of the main circuit conductor, and an electric leakage from the output of the detection winding of the zero-phase current transformer In an earth leakage breaker comprising an earth leakage detection circuit for determining the presence or absence of occurrence, and a tripping device that trips the open / close portion and shuts off the main circuit by an output signal indicating the occurrence of earth leakage of the earth leakage detection circuit,
The temperature detector for detecting the temperature of the zero-phase current transformer is compared with the detected temperature of the temperature detector and a preset temperature. When the detected temperature exceeds the preset temperature, the trip device is An earth leakage circuit breaker provided with a temperature monitoring circuit for providing a trip signal. The earth leakage circuit breaker according to claim 1, wherein the temperature monitoring circuit activates an alarm device when the detected temperature exceeds a set temperature.

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