JP2009140838A - Circuit breaker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit breaker having high current limiting and breaking performance in a range from a small current to a great current without the need for increasing the withstand pressure strength of a case beyond necessity while suppressing temperature rise along with the flow of a load current in a normal state and suppressing excessive rise of pressure in a breaking chamber during breaking a great current. <P>SOLUTION: The breaking chamber 1e partitioned with a partition wall 1d is defined in the case and a current breaking part stored therein is isolated from an opening/closing mechanism part and an overcurrent tripping device, and then a gas exhaust port 1f is opened to the back of an arc-extinguishing device. A vent hole 1g is formed in the breaking chamber 1e at its end on the opposite side to the gas exhaust port 1f in communication with the external of the case. In the vent hole 1g, a valve mechanism 11 is provided which has a ventilating valve 12 and a pressure release valve 13 combined, the former being operated to be opened at a pressure level or lower where pressure in the breaking chamber rises during breaking a small current, and to be closed at a pressure level not lower than that, and the latter being operated to be closed at a pressure level during breaking a small or medium current and to be opened at a higher pressure level during breaking a great current, to releases excessive pressure to the external of the case. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a circuit breaker for wiring breakers, earth leakage breakers, and the like, and more particularly to a structure of a breaker chamber defined in a main body case.

As is well known, the circuit breaker described above has a structure in which a current circuit breaker, a switching mechanism, and an overcurrent tripping device are mounted in a molded resin case in combination with a main circuit contact mechanism and an arc extinguishing device. When an overload trip device is activated by detecting an overload current in the main circuit, the switching mechanism trips to open the main circuit contact and drive the arc generated between the fixed and movable contacts to the arc extinguishing device. To cut off the current.
Also, in the above circuit breaker, when the molten metal such as contact material evaporated by arc heat at the time of overcurrent interruption is scattered around and adheres to the movable part of the switching mechanism and tripping device, Since the function is impaired, in the conventional circuit breaker, the current interrupting portion is isolated from the switching mechanism portion and the overcurrent tripping device and arranged in the interrupting chamber defined inside the case (for example, FIG. 6 shows an assembly structure thereof.
In FIG. 6, 1 is a molded resin case made up of a lower case 1 a, a middle cover 1 b, and a top cover 1 c, 2 and 3 are power supply side, load side terminals, and 4 is a fixed contact formed integrally with the power supply side terminal 2. 5 is a rotating movable contact, 4a is a fixed contact, 5a is a movable contact, 6 is a contact holder for the movable contact 5, 7 is a grid-type arc extinguishing device, 8 is an opening / closing mechanism, and 9 is an operation. A handle 10 is an overcurrent tripping device. In addition, the case 1 is provided with a partition wall 1d and a pole interval wall (not shown) to define a blocking chamber 1e for each pole, and each pole blocking chamber 1e has a current blocking portion corresponding to each phase of the main circuit. The main circuit contact mechanism (fixed contact 4, movable contact 5) and arc extinguishing device 7 are arranged so as to be isolated from the switching mechanism 8 and the overcurrent tripping device 10. Further, a gas exhaust port 1f is opened behind the arc-extinguishing device 7 in the shut-off chamber 1e, and arc gas generated in the shut-off chamber when the current is interrupted is discharged from the gas exhaust port 1f to the outside of the case. The illustrated circuit breaker is depicted in a horizontal position with the operation handle 9 facing upward. However, when the circuit breaker is installed in a panel such as a control panel, the power supply side terminal 2 is usually placed on the upper side. Attach the circuit breaker to the support rail on the panel side in an upright posture toward the board.

On the other hand, in the circuit breaker having the above-described configuration, Joule heat generated in the conductive members (the stationary contact 4 and the movable contact 5) of the main circuit due to energization of the load current is ensured while ensuring a high current-limiting function at the time of current interruption. As a means of suppressing the excessive temperature rise of the shut-off chamber by exhausting the heat to the outside of the case, the shut-off chamber 1e is provided with a vent opening leading to the outside of the case at the opposite end to the gas exhaust port 1f. A configuration in which a valve mechanism is provided in the vent is known (for example, Patent Document 2).
Further, the valve mechanism opens the valve when a load current is applied during normal times, introduces outside air into the space of the shut-off chamber 1e through the vent, and the joule generated in the current-carrying member of the current interrupting part due to the thermal convection (chimney effect) Promotes heat dissipation. On the other hand, when the current is interrupted, the valve is closed by receiving the pressure of the shut-off chamber 1e that rises as the arc gas is generated, and a rapid decrease in the pressure of the shut-off chamber through the vent is suppressed to ensure a high current-limiting shut-off function. ing. That is, when the current is interrupted, the arc generated between the fixed / movable contacts is narrowed from the surrounding by the gas pressure of the interrupting chamber 1e to increase the arc voltage. In this case, in order to exert a high current-limiting interrupting effect, The larger the breaking current, the higher the pressure in the breaking chamber must be secured.
Japanese Patent Laying-Open No. 2006-236798 (p. 4, FIG. 1) JP2003-217429 (p.5, FIG. 1-2)

By the way, in the breaker chamber structure of the circuit breaker disclosed in Patent Document 2, the heat dissipation of Joule heat accompanying energization of the load current can be promoted, and a high current limiting breakage function can be exhibited at the time of current breakage. There are the following problems from the viewpoint of securing strength.
That is, when the current is interrupted, the valve mechanism provided at the vent of the shut-off chamber is closed to keep the arc gas pressure in the shut-off chamber high. For this reason, especially when a large current such as a short-circuit current is interrupted, the pressure in the shut-off chamber becomes very high. FIG. 7 is a graph showing the relationship between the breaking current value, the pressure necessary for current-limiting breaking of current, and the breaking chamber pressure that rises when the current is cut off due to the occurrence of an arc. Represents the pressure required for current limiting interruption, and the characteristic line Pb represents the pressure of the interruption chamber that rises when the electric current is interrupted. As can be seen from this figure, in the large current interruption region (interruption current: current region exceeding 50 kA), the pressure Pb of the interruption chamber that rises at the time of actual current interruption is far greater than the pressure Pa required for current limiting interruption. To be high. Therefore, in order to design and manufacture a circuit breaker case, it is necessary to have a robust structure with mechanical strength that can sufficiently withstand the sudden increase in the pressure in the breaker chamber.
On the other hand, as for the case of the circuit breaker, the case has been conventionally manufactured using a high-strength thermosetting resin, but recently, a thermoplastic resin capable of recycling resources has been adopted. However, engineering plastics, which are high heat resistance and high strength thermoplastic resins, have high material costs and high product costs.

  The present invention has been made in view of the above points, and during normal times, while suppressing the temperature rise of the current interrupting part due to energization of the load current, the pressure in the interrupting chamber exceeds the pressure required for current interrupting at the time of large current interrupting. A circuit breaker with an improved structure of the breaker chamber that can suppress the excessive rise and can exhibit high current-limiting function from small current to large current without needing to strengthen the case withstand pressure more than necessary. The purpose is to provide.

In order to achieve the above-mentioned object, according to the present invention, a circuit breaker comprising a case made of a molded resin and a current breaker comprising a main circuit contact mechanism and an arc extinguishing device, an opening / closing mechanism, and an overcurrent trip device. A breaker chamber for accommodating a current breaker in the case, the breaker chamber being isolated from the opening / closing mechanism and the overcurrent tripping device with a partition wall therebetween, and an arc extinguishing device for the breaker chamber In what opened the gas exhaust port leading to the outside of the case on the side,
A vent that leads to the outside of the case is formed at the end opposite to the gas exhaust port of the shut-off chamber across the current interrupting portion, and the vent is opened during normal load current energization and shut off when a small current is interrupted A valve mechanism that maintains an open state at the pressure level of the chamber, closes at a pressure level that rises when a medium current is interrupted, and opens at an elevated pressure level when a large current is interrupted is provided (Claim 1). It is configured in a specific manner as described below.
(1) Ventilation valve that operates “open” below the pressure level of the shut-off chamber that rises when a small current is interrupted, and “closes” at a pressure level higher than that, and the pressure when a small current and medium current are interrupted The level is “closed”, and the pressure release valve is operated in combination with a pressure release valve that releases the excessive pressure to the outside of the case by performing an “open” operation at the rising pressure level when a large current is interrupted.
(2) In the preceding item (1), the opening operation pressure of the pressure release valve is set to a level exceeding the pressure necessary for current limiting interruption in the large current region (Claim 3).

With the above-described configuration, it is possible to suppress an increase in the temperature of the current interrupting portion due to the thermal convection effect of the outside air taken into the shut-off chamber through the vent when the load current is supplied during normal times.
In addition, by setting the ventilation valve and the pressure relief valve to close at the pressure level of the shut-off chamber corresponding to the shut-off current exceeding the small current, the shut-off chamber pressure is necessary for current-limiting shut-off when the current is interrupted in the middle current range. The current can be limited and interrupted by maintaining the pressure level above a certain level. In addition, when the current in the small current region is interrupted, the rising pressure of the shut-off chamber is released through the vent, but the pressure necessary for interrupting the small current is extremely low from the beginning, so that the current interrupting performance is hardly affected. .
In addition, by setting the pressure relief valve to open at a pressure level corresponding to the current interruption in the large current region, the circuit breaker is released through the pressure relief valve to release the excessive pressure inside the isolation chamber to the outside of the case. It is possible to avoid applying excessive pressure to the case. As a result, it is possible to exhibit high current-limiting interrupting performance at the time of interrupting current from a small current to a large current region, while reducing the product cost by relaxing the pressure strength required for the circuit breaker case.

Hereinafter, embodiments of the present invention will be described based on the examples shown in FIGS. 1A is a cross-sectional view of the overall structure of the circuit breaker, FIG. 1B is a configuration diagram of the valve mechanism in FIG. 1A, and FIGS. It is a figure showing the operation | movement state of the interruption | blocking part and valve mechanism corresponding to the time of current interruption | blocking at the time of an electric current interruption | blocking, an intermediate | middle electric current interruption | blocking, and a large electric current interruption.
That is, the configuration of the circuit breaker in the illustrated embodiment is basically the same as that of the conventional structure shown in FIG. 6, but a vent 1g and a valve mechanism 11 are newly added to the blocking chamber 1e as compared with the conventional structure. ing. Here, the vent 1g is formed on the bottom surface of the case 1 so as to be defined for each pole, and the end opposite to the gas exhaust port 1f opened on the back side of the arc extinguishing device 7 across the current interrupting portion. Open to the part. Further, the vents 1g of each pole communicate with the load side of the case 1 through a passage 1k provided between the bottom lid 1h of the case 1 and partitioned for each pole.
On the other hand, the valve mechanism 11 includes a ventilation valve 12, a pressure release valve 13, and a valve seat 11a. That is, for each pole, the vent 1g is provided with a valve seat 11a integrally with the case 1, and the valve seat 11a has two vent holes 11m. A ventilation valve 12 and a pressure relief valve 13 are installed in the ventilation hole 11m. In the illustrated embodiment (three-phase circuit breaker), three ventilation valves 12 and three pressure release valves 13 are provided, for a total of six valves. The valve seat 11a may be fixed to the case 1 as an independent part. The ventilation valve 12 is spring-biased in the direction in which the valve is opened by the valve spring 12a (pulling coil spring), and the pressure release valve 13 is spring-biased in the direction in which the valve is normally closed by the valve spring 13a (compression coil spring). ing.

Next, operation settings for the ventilation valve 12 and the pressure release valve 13 will be described with reference to FIGS. 8 is a characteristic diagram of breaking current-breaking chamber pressure according to an embodiment of the present invention, FIG. 9 is a chart of opening / closing operations of a ventilation valve and a pressure relief valve, and A in the characteristic diagram of FIG. B represents a medium current region (approximately 10 kA), and C represents a large current region (short-circuit current exceeding the medium current region B). Here, the blocking chamber pressure corresponding to the blocking current value that shifts from the small current region A to the medium current region B is P1, and the blocking chamber pressure that corresponds to the blocking current value that shifts from the medium current region B to the large current region C is P2. As shown in the chart showing the operation setting in FIG. 9, the ventilation valve 12 maintains an “open” state below the pressure P1 with respect to the pressure P1, and the biasing spring when the pressure in the shut-off chamber exceeds P1 The valve is set to be “closed” against 12a. On the other hand, the pressure release valve 13 maintains the “closed” state below the pressure P2 with respect to the pressure P2, and when the pressure in the shut-off chamber exceeds P2, the valve is opened against the biasing spring 13a. Is set.
With the above configuration, in the closed state where the rated load current is applied to the circuit breaker (see FIGS. 2A and 2B), the stationary contact 4 and the movable contact 5 are The current-carrying conductor is heated by Joule heat and the temperature rises. In this current-carrying state, the pressure in the shut-off chamber 1e is almost the same pressure Po as the ambient pressure outside the case (atmospheric pressure), and the ventilation valve 12 is “open”. The pressure release valve 13 is “closed”, and the upper side (power supply side) of the circuit breaker 1e space of the circuit breaker arranged in the panel in the upright posture is in communication with the outside air through the gas exhaust port 1f. The side (load side) communicates with the outside air through the vent 1g and the passage 1k. As a result, the outside air taken in from the vent 1g through the ventilation valve 12 flows into the shut-off chamber 1e through the shut-off chamber by natural convection (chimney effect) and is discharged outward from the gas exhaust port 1f. The energizing member whose temperature has increased due to Joule heat generation due to heat convection is cooled, and an excessive temperature increase in the current interrupting portion is suppressed.

On the other hand, when the small current is interrupted (see FIGS. 3A and 3B), the arc arc generated between the fixed contact and the movable contact causes the pressure in the interrupting chamber 1e to slightly increase. Since the pressure is equal to or lower than the pressure P1 shown in FIG. 8, the ventilation valve 12 continues to maintain the “open” state. Therefore, the arc gas generated in the shut-off chamber 1e flows out of the case through the gas exhaust port 1f and the vent port 1g to reduce the arc-extinguishing chamber pressure. However, the pressure ( Since the characteristic line Pa) in FIG.
Further, when the medium current is interrupted (see FIGS. 4A and 4B), the arc energy of the arc arc generated between the fixed contact and the movable contact is larger than that in the small current region. The pressure also rises above the pressure P1. As a result, while the pressure release valve 13 is kept in the “closed” state, the ventilation valve 12 that has been opened until now is closed by receiving the rising pressure of the shut-off chamber to be in the “closed” state, and the ventilation leading to the outside of the case The mouth 1g is closed. As a result, since the arc gas exhaust path is only from the gas exhaust port 1f, the pressure in the shut-off chamber 1e (characteristic line Pc in FIG. 8) secures the pressure necessary for current interrupt in the middle current region to limit the current. Can be blocked.
In addition, when the current in the shut-off chamber 1e is greatly increased to the pressure P2 or more when a large current is interrupted such as a short circuit accident (see FIGS. 5A and 5B), the ventilation valve 12 remains “closed”. The pressure release valve 13 which has been closed until now is "open" upon receiving the shut-off chamber pressure, and a part of the high-pressure arc gas is discharged from the shut-off chamber 1e to the outside of the case through the vent 1g, so The rise will be suppressed. As a result, the breaker cuts off the large current at a pressure slightly higher than the pressure (see characteristic line Pa in FIG. 8) required for breaking the current limit, and at the same time for the case 1 of the circuit breaker. Further, it is possible to avoid an excessive pressure from being applied to the partition wall 1d that isolates the blocking chamber 1e from the opening / closing mechanism and the overcurrent tripping device. As a result, the pressure strength imposed on the molded resin case 1 can be reduced as compared with a circuit breaker having a conventional structure, so the conditions such as the selection of the molded resin material and the thickness of the case wall can be relaxed. Product cost can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram of the circuit breaker by the Example of this invention, (a) is sectional drawing of the whole structure of a circuit breaker, (b) is a block diagram of the structure of the valve mechanism in (a) figure It is explanatory drawing of the energization state of the load current in the circuit breaker of FIG. 1, (a) is a figure showing the ventilation path | route of a cutoff room, (b) is an operation state figure of a valve mechanism. FIG. 2 is an operation explanatory diagram when a small current is interrupted in the circuit breaker of FIG. 1, (a) is a diagram showing a discharge path of arc gas from the interrupting chamber, and (b) is an operation state diagram of the valve mechanism. FIG. 2 is an operation explanatory diagram at the time of interruption of a medium current in the circuit breaker of FIG. 1, (a) is a diagram showing a discharge path of arc gas from the interruption chamber, (b) is an operation state diagram of the valve mechanism FIG. 2 is an operation explanatory diagram when a large current is interrupted in the circuit breaker of FIG. 1, (a) is a diagram showing a discharge path of arc gas from the shut-off chamber, (b) is an operation state diagram of the valve mechanism. Cross-sectional view of a conventional circuit breaker The figure showing the relation between breaking current and breaking room pressure in the circuit breaker of the conventional structure The figure showing the relationship between the interruption | blocking current by the circuit breaker of this invention, and the interruption | blocking chamber pressure 1 is a chart showing the opening / closing operation settings of the ventilation valve and the pressure relief valve in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Circuit breaker case 1d Partition inside partition 1e Shut off chamber 1f Gas exhaust 1g Vent 4 Fixed contact 5 Movable contact 7 Arc extinguishing device 8 Opening / closing mechanism 10 Overcurrent trip device 11 Valve mechanism 12 Ventilation valve 13 Relief valve

Claims (3)

A circuit breaker in which a main circuit contact mechanism and an arc extinguishing device, a switching mechanism and an overcurrent tripping device are mounted in a molded resin case, and the current interrupting portion is housed in the case The shut-off chamber is isolated from the opening / closing mechanism and the overcurrent tripping device with a partition wall, and a gas exhaust port leading to the outside of the case is opened on the arc extinguishing device side of the shut-off chamber. In things,
A vent that leads to the outside of the case is formed at the end opposite to the gas exhaust port of the shut-off chamber across the current interrupting portion, and the vent is opened during normal load current energization and shut off when a small current is interrupted A circuit breaker comprising a valve mechanism that maintains an open state at a chamber pressure level, closes at a pressure level that rises when a medium current is interrupted, and opens at an elevated pressure level when a large current is interrupted. The circuit breaker according to claim 1, wherein the valve mechanism is a ventilation valve that operates "open" below the pressure level of the shut-off chamber that rises when a small current is interrupted, and "closes" at a pressure level higher than that. A circuit breaker comprising a pressure release valve that closes at a pressure level when a medium current is interrupted and opens at a rising pressure level when a large current is interrupted to release excessive pressure to the outside of the case . 3. The circuit breaker according to claim 2, wherein an opening operation pressure of the pressure release valve is set to a level higher than a pressure necessary for current limiting interruption in a large current region.

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