JP5166730B2 - Three-phase earth leakage breaker - Google Patents

Description

  The present invention relates to a three-phase circuit breaker having a phase loss protection function.

  In recent years, in the technical field of earth leakage circuit breakers, there is a direction to make the JIS standard consistent with the international standard IEC. For example, the interruption operation time of the earth leakage circuit breaker is defined by the IEC in an inverse time form (the operation time is 0.04 seconds or less at the time of excessive electric leakage). On the other hand, the JIS standard stipulates that it is within 0.1 seconds. In IEC, it is necessary to complete the blocking operation in a very short time compared to the JIS standard, which is a difficult problem. Although not in the JIS standard, the IEC is provided with an earth leakage breaker section that cuts off if there is a leakage on the load side even if one of the three phases is missing. In addition, recently, private power generation such as solar power generation has become widespread, and there are many cases in which voltage remains on the load side even after the earth leakage circuit breaker has been cut off. Therefore, there is a demand for an earth leakage circuit breaker that can be reversely connected.

The following patent documents 1 and 2 are known as conventional three-phase earth leakage circuit breaker technologies that partially satisfy the above requirements.
In Patent Document 1, the power source of the leakage detection unit is taken from two of the three phases, and when the thyristor SCR is turned on, a voltage waveform obtained by half-wave rectifying the commercial voltage is applied to the trip coil TC and tripped with a half-wave rectified current waveform A technique is described in which the coil TC is excited and the contacts S1 to S3 are removed.
Further, in Patent Document 2, when the power supply of the leakage detection unit is taken from three phases, leakage detection is performed, and when the thyristor SCR is turned on, a voltage waveform obtained by rectifying the three-phase full wave of the commercial voltage is applied to the trip coil TC. A technique is described in which the trip coil TC is excited with a waveform to trip the contacts S1 to S3.

JP-A-5-290715 JP 2004-015961 A

However, in Patent Document 1, even if the leakage is detected and the thyristor SCR is turned on, a half-wave rectified voltage is applied, so the time during which the trip coil TC is not excited is the worst half cycle (0.01 seconds at 50 Hz). Strongly generated. Also, since the operating time standard value is within 0.04 seconds, a very large amount of time is wasted, and if one of the three phases is lost, it will not operate even if a leakage occurs.
Further, in Patent Document 2, when a reverse connection is used, or when there is a private power generation facility such as solar power generation on the load side, and voltage remains on the load side even after leakage is interrupted, the thyristor SCR does not turn off and trips. There was a possibility that the exciting current continued to flow through the coil TC and burnt out.

  Therefore, in view of the above problems, the present invention shortens the interruption operation time so that even if one of the three phases is lost, even if there is a leakage on the load side, it can be interrupted, and even if it is reversely connected, it will not break down. An object is to provide a three-phase earth leakage circuit breaker that can be used.

In order to solve the above-mentioned problem, the three-phase circuit breaker according to the invention of claim 1 detects the leakage of the three power lines of the three-phase circuit that can supply power from the private power generation equipment to the load side, and outputs a signal. A tripping circuit that trips the contact of a three-phase circuit with a trip coil that detects the leakage current and outputs a signal based on the output signal of the zero-phase current transformer and outputs a signal. A mechanism, an exciting current generating circuit that generates an exciting current from the three-phase AC power of the three-phase circuit, a switching element that causes the exciting current generated by the exciting current generating circuit based on the output signal of the leakage detection circuit to flow to the trip coil, The exciting current generation circuit rectifies the alternating current obtained by stepping down the excitation current to a predetermined voltage and charges it to a single capacitive element, and the switching element generates a leakage current in the zero-phase current transformer. Single capacitive when detected From the charging state to the child until the discharge completion state by discharging the excitation current configured to channel the trip coil.

  The three-phase leakage circuit breaker according to the invention of claim 2 is a step-down circuit in which the excitation current generating circuit adjusts each phase voltage of the three power lines of the three-phase circuit to a predetermined voltage, and rectifies each output voltage of the step-down circuit. And a capacitor that smoothes the output voltage of the rectifier circuit and charges the excitation current flowing through the trip coil as a capacitive element, and uses the surplus power after charging the capacitor as operating power to the leakage detection circuit Configured to supply.

  The three-phase earth leakage circuit breaker according to the invention of claim 3 is configured such that the trip coil is a negative discharge magnetic type.

  According to the first and third aspects of the present invention, since the power supply voltage of the three-phase circuit is smoothed to a constant DC voltage by the exciting current generating circuit, the interruption operation can be instantaneously performed after the detection of the leakage. The breaking operation time of the circuit breaker can be shortened so as to be closer to the IEC inverse time form. In addition, by adjusting the capacitance of the capacitive element, even if one of the three phases is lost, it is possible to secure an exciting current for performing a cutoff operation and to improve the safety. Even if the connection is reversed or voltage remains on the load side, if the capacitive element is discharged, a large excitation current will not continue to flow through the trip coil. It is possible to prevent failures such as disconnection and short circuit due to burning.

  According to the second aspect of the present invention, the exciting current generating circuit can be configured using highly reliable and inexpensive parts.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described in detail with reference to the drawings. FIG. 1 is a circuit diagram showing an example of a three-phase leakage breaker according to the present invention, wherein 1 is a control unit, 2 is a zero-phase current transformer, 3 is a trip coil, 4 is a contact, and 5 is a three-phase circuit. , 6 is an IC leakage detection circuit, and 8 is a capacitor as a capacitive element. 5a is a power supply side terminal of the circuit breaker, and 5b is a load side terminal of the circuit breaker.

  The zero-phase current transformer 2 is installed by inserting the three power lines of the three-phase electric circuit 5, and the output current of the zero-phase current transformer 2 is converted into a voltage by the control unit 1 and supplied to the leakage detection circuit 6 as a detection signal. Entered. The control unit 1 has three power supply lines that supply operating power to the leakage detection circuit 6 from the R, S, and T phases of the three-phase circuit 5. An excitation current generating circuit 16 that generates an excitation current from the three-phase AC power of the three-phase electric circuit 5 is connected to the three power lines. On the three-phase electric circuit side of the three power supply lines, a step-down circuit 11 is provided in which resistors R1 to R6 corresponding to both ends of the capacitors C5, C6, and C7 are connected in series. A rectifier circuit 12 composed of .about.D6 is provided. The collective end of the power line after rectification by the rectifier circuit 12 is connected to the ground line via a capacitor 8 that smoothes the rectified voltage and charges the excitation current of the trip coil 3. The exciting current generation circuit 16 includes the step-down circuit 11, the full-wave rectifier circuit 12, and the capacitor 8. The trip coil 3 functions as a configuration of a tripping mechanism that trips the contact 4 of the three-phase circuit 5 by passing an exciting current.

  Further, the collective end of the rectified power supply line is connected to the power supply terminal of the leakage detection circuit 6 and one end of the trip coil 3. The other end of the trip coil 3 is connected to the anode end of a thyristor 9 as a switching element that causes the exciting current generated by the exciting current generating circuit 16 to flow to the trip coil 3 based on the output signal of the leakage detection circuit 6. The cathode end is connected to a ground line.

  Here, when the exciting current is not flowing, the trip coil 3 accumulates the spring by the magnetic force of the permanent magnet and holds the contact in the closed state. On the other hand, when the exciting current is flowed, the trip coil 3 cancels the magnetic flux of the permanent magnet. It is composed of a so-called magnetic discharge type that weakens the magnetic force and releases the stored spring to open the contact. The step-down circuit 11 drops the power supply voltage to a voltage value at which an excitation current capable of opening the trip coil 3 can flow, and the capacitor 8 is a voltage that predefines the full-wave rectified voltage of the full-wave rectifier circuit 12. It is comprised so that it may smooth within the fluctuation range. It should be noted that the voltage fluctuation range is preferably set to a value that allows tripping of the trip coil 3 even when only one phase is smoothed by full-wave rectification.

Next, the operation of the above circuit will be described.
When there is no leakage in the three-phase electric circuit 5, the exciting current generation circuit 16 drops and full-wave rectifies the AC voltage of each phase to a predetermined voltage by the step-down circuit 11 and the rectifier circuit 12. Further, at the collective end of the rectifier circuit 12, the capacitor 8 always charges the rectified voltage so as to smooth the rectified voltage to a predetermined DC voltage and output an excitation current sufficient to open the trip coil 3. The surplus power after charging the capacitor 8 is supplied to the leakage detection circuit 6 as operating power, and the leakage detection circuit 6 is operated by a predetermined DC voltage.

  When leakage occurs in any of the three phases, the thyristor is turned on by the detection signal output from the zero-phase current transformer 2 that has detected the leakage. Then, the capacitor 8 is discharged to the ground line via the thyristor 9, and an exciting current is supplied to the trip coil 3 for a predetermined time from the charging state to the discharging completion state. Then, the contact 4 is opened and the three-phase electric circuit 5 is disconnected from the power supply without time difference after the thyristor 9 is turned on. Even when one of the three phases is lost, the DC voltage of a predetermined value is output at the collective end of the rectifier circuit 12 in the same manner, and the cutoff operation is performed.

  According to this earth leakage breaker, the power supply voltage of the three-phase circuit 5 is smoothed to a constant DC voltage by the step-down circuit 11, the rectifier circuit 12, and the capacitor 8, so that the breaking operation is instantaneously performed after the detection of the earth leakage. Therefore, it is possible to shorten the interruption operation time of the earth leakage circuit breaker to the IEC specified value or less. In addition, by adjusting the capacity of the capacitor 8, even if one of the three phases is lost, an exciting current for performing the cutoff operation can be secured, and the cutoff operation can be performed. In addition, if the capacitor 8 is discharged even if it is reversely connected or if the voltage remains on the load side, a large exciting current will not continue to flow through the trip coil 3, so It is possible to eliminate the risk of burnout of the connected parts and prevent failures such as disconnection and short circuit due to the burnout. Moreover, since the surplus power after charging the capacitor 8 is supplied to the leakage detection circuit 6 as operating power, it can be shared with the exciting current generation circuit 16 and the circuit configuration can be simplified. Further, the exciting current generating circuit 16 can be configured using highly reliable and inexpensive parts.

In addition, this invention is not limited to the said embodiment, As shown below, it is also possible to implement by changing suitably the shape and structure of each part in the range which does not deviate from the meaning of this invention.
(1) The excitation current generation circuit may be configured to generate only the excitation current by using a separate power source circuit for the leakage detection circuit.
(2) The trip coil is not limited to a magnetic discharge type, and any trip coil may be used as long as it has a structure in which the contact is pulled off by flowing an exciting current. Alternatively, it may be configured to be removed by flowing an excitation continuous current so as to generate a strong magnetic force.
(3) The switching element is not limited to the thyristor SCR, and may be a so-called transistor or FET.
(4) The step-down circuit only needs to be able to drop to a predetermined voltage, and may be composed of other circuits.

It is a block diagram of the three-phase earth-leakage circuit breaker according to the present invention.

Explanation of symbols

  1 .... Control unit, 2 .... Zero phase current transformer, 3 .... Trip coil, 4 .... Contact, 5 .... Three phase circuit, 6 .... Leakage detection circuit, 8 .... Capacitor, 9 .... Thyristor, 11 .... Voltage drop circuit, 12 .... Excitation current generation circuit.

Claims (3)

A zero-phase current transformer that detects a leakage of three power lines in a three-phase circuit that can supply power from a private power generation facility to the load side, and outputs a signal;
A leakage detection circuit that detects a leakage based on the output signal of the zero-phase current transformer and outputs a signal;
A tripping mechanism that trips the contacts of the three-phase circuit with a trip coil that passes excitation current,
An exciting current generating circuit for generating an exciting current from the three-phase AC power of the three-phase electric circuit;
A switching element that causes the excitation current generated by the excitation current generation circuit to flow through the trip coil based on the output signal of the leakage detection circuit;
With
The exciting current generator circuit
The excitation current is generated by rectifying an alternating voltage that is stepped down to a predetermined voltage and charging it to a single capacitive element.
Switching elements are
When the zero-phase current transformer detects a leakage, a single capacitive element is discharged from the charging state to the discharging completion state, and the exciting current is discharged to the trip coil.
A three-phase earth leakage circuit breaker. The exciting current generator circuit
A step-down circuit that steps down each phase voltage of the three power lines of the three-phase circuit to a predetermined voltage;
A rectifier circuit that rectifies each output voltage of the step-down circuit;
As a capacitive element, a capacitor that smoothes the output voltage of the rectifier circuit and charges an exciting current that flows through the trip coil, and
Supply surplus power after charging the capacitor to the leakage detection circuit as operating power,
The three-phase ground fault circuit breaker according to claim 1. The trip coil is a parallel discharge type,
The three-phase earth leakage circuit breaker according to claim 1 or 2.

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