JP5021439B2 - 3-phase earth leakage circuit breaker - Google Patents

Description

  The present invention relates to a three-phase circuit breaker, and more particularly to a three-phase circuit breaker that operates even if one of the three phases is lost.

Some 3-phase earth leakage circuit breakers are configured to detect an earth leakage and perform a breaking operation even if one of the three phases is lost. For example, Patent Document 1 adopts a power supply for a leakage detection circuit and an operation power supply for a trip coil that performs a cutoff operation from each of three phases, thereby enabling a cutoff operation even if one phase is lost.
On the other hand, in order to save energy and reduce carbon dioxide, an increasing number of households and offices have installed private power generation facilities such as solar power generation. When such a private power generation facility exists, even if the earth leakage breaker shuts down and stops supplying commercial power, a voltage may continue to be generated on the load side. For this reason, it is necessary to use an earth leakage circuit breaker that can be reversely connected, for example, as disclosed in Patent Document 2 so that current does not continue to flow through the circuit breaker that has been cut off even in such a case. The earth leakage breaker disclosed in Patent Document 2 is configured so that the voltage waveform applied to the thyristor is provided with a short time (zero crossing time) for maintaining 0 V so that the thyristor is reliably turned off. In this case, the time for zero crossing is 1/6 cycle of the voltage frequency.

JP 2006-107737 A Japanese Patent Laying-Open No. 2005-302418

In recent years, there has been a demand for speeding up the earth leakage interrupting operation. Specifically, when a relatively large earth leakage occurs with anti-time characteristics, within 0.04 seconds (when the frequency is 50 Hz) Is desired to be shut off within 2 cycles). In this regard, the earth leakage breaker disclosed in Patent Document 1 has excellent characteristics of instantaneously interrupting operation because the trip coil operating power source is taken from all three phases. However, in a place where the reverse connection is not supported and the power generation equipment as described above exists on the load side, there is a problem that the current continues to flow through the trip coil and it cannot be used.
In addition, the leakage breaker disclosed in Patent Document 2 operates well even when reversely connected, and the trip coil does not burn out. However, since the power source of the leakage detection circuit has a zero cross time, In some cases, the shut-off characteristics at the time of turning on the device become unstable, and the shut-off operation time does not satisfy the above requirements, and the thyristor may not turn off due to the capacity component of the power supply circuit.

  Therefore, in view of such problems, the present invention performs an earth leakage interrupting operation even if one phase is lost, performs a high-speed interrupting operation that satisfies the above requirements, and causes a failure such as burning even when reversely connected. An object of the present invention is to provide a three-phase ground fault circuit breaker without any problems.

In order to solve the above-mentioned problems, the invention of claim 1 is characterized in that an open / close unit that opens and closes an electric circuit, a zero-phase current transformer that detects a zero-phase current of the electric circuit, and a leakage current from the detected current of the zero-phase current transformer A three-phase leakage breaker comprising a leakage determination circuit for determining occurrence and a trip coil for opening the switching unit, the three-phase full-wave rectifier circuit supplying operating power to the leakage determination circuit, The first thyristor and the second thyristor that are turned on in response to an output signal of the leakage determination circuit and trip the trip coil, and the trip coil receives supply of operating current from two different phases of the electric circuit. The first and second thyristors are respectively arranged on the two parallel current supply paths.
According to this configuration, power is supplied to the leakage detection circuit from all three phases, and the trip coil operating current is supplied from two phases. Therefore, even if one of the three phases is lost, the leakage is detected. If this occurs, it will shut off. However, since the trip coil is supplied with current from two phases of the electric circuit, the trip coil instantaneously cuts off.
And even if the reverse connection or the situation where the voltage remains on the load side after interruption, the voltage applied to the first and second thyristors can be turned off by providing a zero cross time, It is possible to prevent a situation in which energization of the trip coil is continued after the shut-off operation and the trip coil burns out.

According to a second aspect of the invention, in the first aspect of the invention, the first thyristor is connected in series with a third thyristor that is turned on in conjunction with the on-operation of the first thyristor, The thyristor is characterized in that a fourth thyristor that is turned on in conjunction with the on operation of the second thyristor is connected in series.
According to this configuration, since the thyristors are arranged in two stages between the phases of the electric circuit, it is possible to use a thyristor having a low withstand voltage relative to the interphase voltage. For example, a thyristor having a withstand voltage of 200 V can be used for the 400 V electric circuit. It becomes. Therefore, the rated voltage of the earth leakage breaker can be increased without increasing the withstand voltage of the thyristor.

According to the present invention, power is supplied to the leakage determination circuit from all three phases, and the trip coil operating current is supplied from two phases. Therefore, even if one of the three phases is lost, the leakage is detected. If this occurs, it will shut off. However, since the trip coil is supplied with current from two phases of the electric circuit, the trip coil instantaneously cuts off.
Since the voltage applied to the first and second thyristors has a zero-crossing time, the trip coil does not continue to turn on even when reversely connected, and the trip coil continues to be energized after the shut-off operation. It can prevent the situation of burning.
Further, by arranging the thyristors in two stages between the phases of the electric circuit, it is possible to increase the rated voltage of the earth leakage breaker without increasing the withstand voltage of the thyristor.

  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 circuit breaker according to the present invention, where 1 is an electric circuit composed of three phases to be interrupted (L1, L2, and L3 phases), and 2 is an open / close circuit that opens and closes the electric circuit 1 , 3 is a zero-phase current transformer for detecting the zero-phase current of the electric circuit 1, 4 is a trip coil for opening (opening / closing) the switching unit 2, and 5 is for detecting the occurrence of electric leakage to drive the trip coil 4. This is a leakage detection circuit.

  The leakage detection circuit 5 includes an IC leakage determination circuit 6 that determines the occurrence of leakage from the zero-phase current of the electric circuit, a power supply circuit 7 that supplies power to the leakage determination circuit 6, and a first thyristor that drives the trip coil 4. A trip coil drive circuit 8 comprising S1 and a second thyristor S2 is provided. The trip coil drive circuit 8 is connected to the L1 phase by providing the third thyristor S3 at the anode of the first thyristor S1, and connected to the L2 phase by providing the fourth thyristor S4 at the anode of the second thyristor S2. Has been. That is, the first and third thyristors S1 and S3 are connected in series, and the second and fourth thyristors S2 and S4 are connected in series to form two parallel current supply paths for the trip coil 4.

  Note that the gate of the third thyristor S3 is connected so that the first thyristor S1 is turned on when the first thyristor S1 is turned on, and the fourth thyristor S4 is linked when the second thyristor S2 is turned on. The gate is connected to turn on.

  The cathodes of the first and second thyristors S1 and S2 are connected in parallel to a common line (GND circuit) 10 serving as one end of the trip coil 4, and the other end of the trip coil 4 is connected to the circuit via diodes D7 and D8. 1 is connected to both the L2 phase and the L3 phase. In addition, the power supply circuit 7 takes power from all three phases of the electric circuit 1 and drops the voltage with six capacitors C1 to C6, and rectified by a full-wave rectifier circuit 7a composed of six diodes D1 to D6. The voltage is supplied to the power supply terminal B of the leakage determination circuit 6.

  The leakage detection circuit configured as described above operates as follows. When leakage occurs, the zero-phase current transformer 3 detects this as a change in zero-phase current, and the leakage determination circuit 6 determines the level of leakage. When the detected zero-phase current exceeds a predetermined threshold value, the leakage determination circuit 6 outputs an ON signal from the output terminal A to both the first thyristor S1 and the second thyristor S2, and the signal is input to the gate. The first thyristor S1 and the second thyristor S2 are turned on. By this on operation, the third thyristor S3 and the fourth thyristor S4 are also turned on, and an operating current flows through the trip coil 4. Thus, the tripping operation is performed and the opening / closing part 2 is opened.

  Specifically, when the first thyristor S1 is turned on, the L1 phase of the electric circuit 1, the third thyristor S3, the first thyristor S1, the trip coil 4, the diode D7, the L3 phase of the electric circuit 1, and the electric circuit 1 A current flows through the L2 phase path of the L1 phase, the third thyristor S3, the first thyristor S1, the trip coil 4, the diode D8, and the electric circuit 1 to excite the trip coil 4. When the second thyristor S2 is turned on, current flows through the L2 phase of the electric circuit 1, the fourth thyristor S4, the second thyristor S2, the trip coil 4, the diode D7, and the L3 phase of the electric circuit 1, and the trip coil. 4 is excited. The thyristors S1 to S4 use elements having the same characteristics, and the interphase voltage itself is not applied to the thyristors S1 to S4.

  Further, looking at the voltage waveform at this time, when the electric circuit 1 is in the energized state, the voltage waveform as shown in FIG. 2A is applied to the first thyristor S1, and the second thyristor S2 is applied. A voltage waveform as shown in FIG. 2B is applied. As described above, the first thyristor S1 forms a current supply path between the L1 phase, the L2 phase, and the L3 phase of the electric circuit 1, but the second thyristor S2 is the L2 of the electric circuit 1. This is because the current supply path is formed only between the phase and the L3 phase. As shown in FIG. 2, it can be seen that the first thyristor S1 has a ３ cycle zero-cross time, and the second thyristor S2 has a ½ cycle zero-cross time.

  The voltage applied to the first and second thyristors S1 and S2 disappears in the normal operation in which the three-phase leakage circuit breaker is positively connected, but the switching unit is opened (breaking operation). When connected or when the power generation equipment is provided on the load side, there is a case where the opening / closing section 2 does not disappear even if the opening / closing section 2 is opened. In such a case, that is, when the voltage continues to be applied to the load side even after the interruption operation, the voltage waveform shown in FIG. 2 is applied to the first thyristor S1 and the second thyristor S2 as in the case of the positive connection. The Therefore, a large current continues to flow through the trip coil 4 unless the first thyristor S1 and the second thyristor S2 are turned off.

  However, as shown in the waveform diagram of FIG. 2, there exists at least 1/3 cycle or more of the zero cross time during which no voltage is applied. If the output from the leakage determination circuit 6 to the gates of the first and second thyristors S1 and S2 is stopped by the long zero crossing time, both the thyristors S1 and S2 are surely stopped. Therefore, current does not continue to flow through the trip coil 4.

  Further, when one of the three phases of the electric circuit 1 is lost, when the L2 phase or the L3 phase is lost, the trip coil 4 is excited by the first thyristor S1 to be cut off. Can do. When the phase L1 is lost, the trip coil 4 can be excited by the second thyristor S2 to cut off the electric circuit 1.

In this way, since power is supplied to the leakage detection circuit from all three phases, and trip coil operating current is supplied from two phases, leakage occurs even if one of the three phases is lost. Then shut off. However, since the trip coil is supplied with current from two phases of the electric circuit, the trip coil instantaneously cuts off. And even if the reverse connection or the situation where the voltage remains on the load side after interruption, the voltage applied to the first and second thyristors can be turned off by providing a zero cross time, It is possible to prevent a situation in which energization of the trip coil is continued after the shut-off operation and the trip coil burns out.
Further, since the thyristors are arranged in two stages between the phases of the electric circuit, it is possible to use a thyristor having a low withstand voltage with respect to the interphase voltage. For example, a thyristor having a withstand voltage of 200V can be used for the 400V electric circuit. Therefore, the rated voltage of the earth leakage breaker can be increased without increasing the withstand voltage of the thyristor.

  In the above embodiment, the third thyristor S3 is connected in series to the first thyristor S1, and the fourth thyristor S4 is connected in series to the second thyristor S2, but the third and fourth thyristors S3, S3 are connected. Even if S4 is not present, it is possible to maintain a fast interruption time characteristic, and even when reverse connection is established, a good leakage interruption operation is achieved.

It is a circuit diagram which shows an example of embodiment of the three-phase earth-leakage circuit breaker which concerns on this invention. FIG. 5 shows a thyristor applied voltage waveform, where (a) shows a voltage waveform applied to the first thyristor, and (b) shows a voltage waveform applied to the second thyristor.

Explanation of symbols

  1 .... Electric circuit 2 .... Opening / closing part 3 .... Zero phase current transformer 4 .... Trip coil 5 .... Leak detection circuit 6 .... Leak determination circuit 7 .... Power supply circuit 7a ... All Wave rectifier circuit, 8 .. Trip coil drive circuit (current supply path), S1... First thyristor, S2... Second thyristor, S3... Third thyristor, S4.

Claims (2)

An open / close unit that opens and closes an electric circuit, a zero-phase current transformer that detects a zero-phase current of the electric circuit, a leakage determination circuit that determines occurrence of leakage from the detected current of the zero-phase current transformer, and an opening operation of the switch A three-phase earth leakage circuit breaker having a trip coil
A three-phase full-wave rectifier circuit that supplies operating power to the leakage determination circuit; and a first thyristor and a second thyristor that are turned on in response to an output signal of the leakage determination circuit and cause the trip coil to perform a trip operation. And
The trip coil is supplied with an operating current from two different phases of the electric circuit, and the first and second thyristors are respectively disposed on two parallel current supply lines. vessel. The first thyristor is connected in series with a third thyristor that is turned on in conjunction with the on operation of the first thyristor, and the second thyristor is turned on in conjunction with the on operation of the second thyristor. The three-phase earth leakage circuit breaker according to claim 1, wherein the fourth thyristors are connected in series.

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