WO1997011475A1 - Circuit breaker - Google Patents

Abstract

A circuit breaker suitable for simplifying the constitution of a current detection means. The assignment to be solved by the invention is to provide a circuit breaker that can be easily assembled and mounted in a small space. The above assignment is solved by a constitution in which a magnetoresistive element is disposed close to an electric conductor that runs from a power source terminal to a load terminal, a control means generates an output when a current flowing through the electric conductor relying upon the output of the magnetoresistive element satisfies a predetermined condition, and a trip means opens a switch means relying upon the above output. The circuit breaker is easily assembled and is mounted in a small space.

Description

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Technical field

 The present invention relates to a circuit breaker having current detection means for electromagnetically detecting a current in an electric circuit, and more particularly to a circuit breaker suitable for simplifying the configuration of current detection means.

Background art

 As a conventional technique of this kind, for example, a current transformer is used as a current detection sensor as disclosed in Japanese Patent Application Laid-Open No. H05-236636. As disclosed in Japanese Unexamined Patent Publication No. 57-59426, the use of a Hall element as a current detection sensor is known.

 In the conventional technology, current transformers have a structure in which the main circuit conductor penetrates through the hollow part of the annular iron core (magnetic ring). As pointed out in the Bulletin No. 5 — 594 426, there was a problem when the mounting space became large.

In the case of using a Hall element, a compact and economical current sensor can be obtained.However, the output voltage of the Hall element is small and the main circuit current can be reliably detected in a small current region. There is a problem of difficulty. In order to solve this problem, the main circuit conductor must be penetrated into the hollow using a magnetic ring to increase the output voltage of the Hall element by increasing the magnetic flux density around the main circuit conductor. Weird It is necessary to adopt the same configuration as that using a flow device. Therefore, the workability at the time of assembling is not improved even if the Hall element is used.

Disclosure of the invention

 An object of the present invention is to provide a circuit breaker which is excellent in workability at the time of assembling and has a small mounting space in order to solve the above problems.

 The above purpose is to provide a circuit breaker that has switching means in a current-carrying conductor from a power-supply-side terminal to a load-side terminal and opens the switching means when a current flowing through the current-carrying conductor reaches a predetermined condition. A magnetoresistive element (hereinafter referred to as an MR element) placed close to the current-carrying conductor, and based on the output of this MR element, generates an output when the current flowing through the current-carrying conductor reaches a predetermined condition. This is achieved by providing a control means for performing the operation and a trip means for opening the opening / closing means by being driven by the output of the control means.

 Further, the above object is achieved by adopting a configuration in which a bias magnetic field that can be arbitrarily adjusted is applied to the MR element.

 Since the MR element generally has an order of magnitude higher sensitivity than the Hall element, it is possible to accurately detect the main circuit current in a small current region without using a magnetic ring or the like. When a semiconductor MR element that can be applied up to a high magnetic field is used as the MR element, the main circuit current detection range can be increased as compared with the case where a ferromagnetic MR element is used.

When MR elements are used as a pair for temperature characteristic compensation, both A magnetic bias is added to the MR element, and the magnetic bias strength is controlled according to the magnetic field strength to be detected. This makes it possible to arrange a pair of MR elements at close positions, that is, at substantially the same position. The magnetic bias strength is controlled by adjusting the exciting current of the magnetic bias applying coil.

BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1 is a cross-sectional view showing the overall configuration of a circuit breaker according to one embodiment of the present invention.

 FIG. 2 is a cross-sectional view of a circuit breaker according to one embodiment of the present invention, showing a positional relationship between an MR element and a main circuit conductor, in a direction perpendicular to the direction of conduction of the main circuit conductor.

 FIG. 3 is a perspective view showing a state where the MR element of the circuit breaker according to the embodiment of the present invention is attached to a main circuit conductor.

 FIG. 4 is a waveform diagram illustrating the operation of the current detecting means using the MR element of the circuit breaker according to one embodiment of the present invention. FIG. 4 (a) shows the operation in the low magnetic flux density region, and FIG. Panel b) shows the operation when a bias magnetic field is applied.

 FIG. 5 is a circuit diagram showing a configuration of a current detecting means using an MR element of a circuit breaker according to one embodiment of the present invention. FIG. 5 (a) is a basic circuit configuration, and FIG. It is a figure which shows the circuit structure which compensated, respectively.

FIG. 6 is a circuit diagram of current detection means for generating a differential output by performing temperature compensation using the MR element of the circuit breaker according to one embodiment of the present invention. is there.

 FIG. 7 is a cross-sectional view of a circuit breaker according to one embodiment of the present invention, showing a positional relationship between the MR element and the main circuit conductor when a bias is applied, taken in a direction perpendicular to the direction of current flow in the main circuit conductor. You.

 FIG. 8 is a waveform diagram illustrating the operation of the current detecting means of the circuit breaker according to one embodiment of the present invention.

 FIG. 9 is a waveform diagram illustrating a bias control operation of the current detecting means of the circuit breaker according to one embodiment of the present invention.

 FIG. 10 is a waveform diagram illustrating a bias control operation of the current detecting means of the circuit breaker according to one embodiment of the present invention.

 FIG. 11 is a block diagram showing a circuit configuration of a circuit breaker according to one embodiment of the present invention.

 [Fig. 12] Fig. 12 is a characteristic diagram explaining the time limit characteristics of a general circuit breaker.

 FIG. 13 is a cross-sectional view of the circuit breaker according to one embodiment of the present invention, showing a positional relationship between the MR element housing and the main circuit conductor, in a direction perpendicular to the direction of current flow of the main circuit conductor.

 FIG. 14 is a perspective view showing a state in which the MR element housing of the circuit breaker according to one embodiment of the present invention is mounted on a load-side conductor.

 FIG. 15 is a cross-sectional view of the circuit breaker of one embodiment of the present invention, showing a state in which the MR element housing is fixed to the case, in a direction perpendicular to the direction of current flow of the main circuit conductor.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows the overall configuration of the circuit breaker of this embodiment. In this embodiment, a current sensor using the MR element 30 is attached to a conductor of the main circuit, and the current of the main circuit is detected by the MR element 30. A current-carrying conductor 10 extending from the power supply terminal 4 to the load terminal 6 is provided below the case 1 in the case 3 which is a case 1 and a housing 3. The current-carrying conductor 10 is connected to the fixed conductor 11 provided with the power supply side terminal 4 at one end, the flexible conductor 12 connected to the fixed conductor 11, and the flexible conductor 12, and turned to the pin 14. It has a repulsion contact base 13 that is pivotally supported on its own, a repulsion contact point 15 provided on the repulsion contact base 13, and a movable contact 16 provided opposite to the repulsion contact 15. The movable contact block 17 provided, the flexible conductor 18 connected to the movable contact block 17, and the load-side conductor 19 connected to the flexible conductor 18 and provided with the load-side terminal 6. It depends. An arc extinguishing device 20 is provided around the repulsive contact 15 and the movable contact 16. The movable contact block 17 is operated by an opening / closing mechanism 22 disposed above it to open and close the electric circuit. In this embodiment, the repulsive contact 15, the movable contact 16, and the opening / closing mechanism 22 function as opening / closing means, and the opening / closing mechanism 22 is normally turned ON / OFF by manual operation of the handle 24. When the tripping device 26 as a tripping means operates due to overcurrent or the like, the tripping operation is performed by automatically opening the electric circuit. In this embodiment, the overcurrent is detected by electrically connecting the MR element 30 provided in close proximity to the load-side conductor 19 and the MR element 30. The control is performed by a control circuit 40 as control means connected to the control circuit. The MR element 30 and the control circuit 40 are connected by a lead wire 42. The control circuit 40 is an electronic circuit assembled on a board, and includes an analog circuit, a logic circuit, and It is composed of a micro computer and the like. The control circuit 40 determines that the current detected by the MR element exceeds a predetermined condition, that is, exceeds a certain reference value, is an overcurrent, and generates an output for tripping.

 The state of attachment of the MR element 30 to the load-side conductor 19 will be described with reference to FIGS. The MR element 30 is housed in an MR element housing 34 made of an insulating material to be insulated from the load-side conductor 19, and is fixed to the load-side conductor 19 by a screw 32. Lead wires 42 are drawn out from the MR element housing 34.

There are two types of MR elements: semiconductor MR elements and ferromagnetic MR elements. Generally, a semiconductor MR element has a characteristic that the resistance of the element increases with an increase in the absolute value of the magnetic flux density, and the magnetic flux density is up to 1 Tesla (10,000 Gauss) or more. The resistance value that can obtain this characteristic can be arbitrarily created, for example, a resistance value of several kΩ can be created. The change in the resistance value is also large, for example, about 1 kΩ at 0 Tesla and about 5 kΩ at 1 Tesla, which is about 5 times the change. On the other hand, a ferromagnetic MR element has the characteristic that it has the maximum resistance value at zero magnetic flux density, decreases as the absolute value of magnetic flux increases, and saturates at a certain magnetic flux density. ing. The change in the resistance value is about several percent of the initial value, and the saturation magnetic flux density ranges from several tens of gauss (several milliliters) to several hundred gauss (several tens of milliliters). (Slurry), and the range that can be used as a sensor is much smaller than that of a semiconductor MR element. Therefore, when a semiconductor MR element is used, it can be applied up to a high magnetic field, and the main circuit current detection range can be enlarged, as compared with the case where a ferromagnetic MR element is used.

 The MR element 30 used in the present embodiment is a semiconductor MR element, and its characteristics are such that the element resistance changes in accordance with the applied magnetic flux density as shown in FIG. . As shown in Fig. 4 (a), the MR element 30 has a low sensitivity in the low magnetic flux density region and a small resistance change rate, so that the bias magnetic field is applied by a magnet. As shown in Fig. 4 (b), the operating point is shifted and used in the high sensitivity area. This is possible by applying an arbitrarily adjustable bias magnetic field to the MR element.

Since the sensitivity of the MR element 30 is generally one order of magnitude higher than that of the Hall element, it is possible to reliably detect the main circuit current in a small current region without using a magnetic ring or the like. When the MR element 30 is used as a current sensor, it only needs to be arranged near the conductor to be energized, and the annular magnetic ring used in the case of the ball element need not be used. For this reason, the work of penetrating the conductor through the annular magnetic ring is not required, and the workability at the time of assembly can be improved. Also, since it is only necessary to dispose the MR element 30 near the conductor, the mounting The base can be reduced.

 In addition, as shown in FIG. 5 (a), the MR element 30 basically uses a configuration in which the control voltage Vcc is divided by the external resistor r and the MR element 30 as shown in FIG. 5 (a), and is shown in FIG. Using the fact that the resistance value R2 of the MR element changes according to the magnetic flux density according to the characteristics and the voltage dividing ratio of the control voltage Vcc changes, the output change is used as a detection signal. It is used.

 However, the MR element generally has poor temperature characteristics. In other words, since the element resistance greatly changes due to the change in temperature, two MR elements 30 and 30a are used as a countermeasure as shown in Fig. 5 (b). Generally, the element 30a is used for temperature compensation, and the other MR element 30 is used for magnetic flux detection. Also, as shown in Fig. 6, the output is often extracted in the form of a difference.

However, in the case of current sensor applications, two MR elements are placed close to each other in order to perform temperature compensation, while the temperature compensation MR element side is ideal. Must be protected from the influence of the magnetic field, and it is difficult to realize the arrangement method and the magnetic flux shielding method. In this embodiment, when MR elements are used as a pair for temperature characteristic compensation, a magnetic bias is applied to both MR elements, and the magnetic bias strength is controlled according to the magnetic field strength to be detected. . This makes it possible to arrange a pair of MR elements at a close position, that is, at substantially the same position. To control the magnetic bias strength, a magnetic bias is applied by a coil to adjust the exciting current. It is done by adjusting. That is, in the present embodiment, by applying a magnetic bias in the opposite direction also to the MR element for temperature compensation, a function for magnetic detection is provided and the arrangement at the same position is performed. It is possible.

 Therefore, in this embodiment, as shown in FIG. 7, in order to share functions for temperature compensation and magnetic flux detection for both MR elements, they are arranged in a state in which reverse biases are applied to each other. It is configured so that As shown in Fig. 8, the operation of the MR elements is reversed, as shown in Fig. 8, so that the operating point is in a symmetrical position. In the opposite direction, that is, when one increases, the other decreases, and the voltage division ratio of the control power supply Vcc changes according to the increase and decrease of the detected magnetic flux. Become.

 In Fig. 7, the force applied to the MR element by bias is applied to the MR element by a coil; of course, a magnet may be used. The advantage of using a coil is that, for example, when a detected magnetic flux that is equal to or greater than the set bias is applied as shown in Fig. 9, there is an area where the change in resistance value reverses. As shown in Fig. 10, it is easy to change the amount of the magnetic flux depending on the magnitude of the magnetic flux.

As a matter of course, there is no problem even if the initial setting bias is increased, but if the bias is given by a magnet, it becomes expensive, and If a coil is used, a large amount of control current will be consumed even in the low current detection region. Therefore, it is convenient to change the bias point according to the detection current region. Fig. 11 is a block diagram of the circuit configuration in the embodiment. After the current flowing in the circuit is detected by the MR element, the current is input to the MPU via the AZD converter, and the input is input to the MPU. Based on the signal, the time limit characteristic of the circuit breaker as shown in Fig. 12 is controlled.

When an MR element is used in a 3-pole circuit breaker for three-phase AC, as shown in Fig. 13 and Fig. 15, the MR element 30 for each phase is integrally formed of three phases. Then, it is stored in the MR element housing 36 and fixed to the bottom of the case 1 by screws 32. Figure 14 shows the MR element housing 36 placed on the load-side conductor 19. The MR element housing 36 has a positioning projection 36a formed at the lower portion thereof, and a projection 36b for mounting the control circuit 40 formed thereon at the upper portion thereof. The positioning projections 36a are formed between the load-side conductors 19 of each pole, and between the load-side conductors 19 of both poles and the side surface of the case 1. The protrusions 36b are formed at intervals necessary for mounting the control circuit 40 and fixing the control circuit 40 by screws or elastic engagement. FIG. 13 is a cross-sectional view showing a part of the MR element housing 36 that houses the MR element. As shown in Fig. 13, the MR element 30 is embedded in the insulator so that it is above the load-side conductor 19 and close to the load-side conductor 19, as shown in Fig. 13. It is fixed on the insulating partition between the conductors at the bottom of case 1 by screws 32. FIG. 15 shows a state in which the MR element housing 36 is fixed to the case 1. A lead wire 42 is drawn upward from the MR element housing 36 and connected to the control circuit 40 mounted on the MR element housing 36. In FIGS. 14 and 15, the illustration of the screw 32 is omitted. In the present embodiment, the MR element, which generally has an order of magnitude higher sensitivity than the Hall element, is used as a current sensor for a circuit breaker. The magnetic ring used for main circuit current detection can be eliminated, and the size and weight of the circuit breaker can be reduced.

 In addition, the magnetic ring needs to penetrate the load-side conductor 19, which complicates the manufacturing process and increases the number of manufacturing steps. The current detection sensor can be mounted simply by mounting the body 34 or 36 on the load-side conductor 19, which simplifies the manufacturing process and reduces the number of manufacturing steps. .

 In the present embodiment, the current in the load-side conductor 19 is detected by the MR element 30. However, the position where the current is detected may be the fixed conductor 11 on the power supply side. Further, in this embodiment, as the opening / closing means, a mechanical one composed of a repulsive contact 15, a movable contact 16 and an opening / closing mechanism 22 is used, but a thyristor or the like is used. A non-contact type using a semiconductor for power switching may be used. In this embodiment, the overcurrent is detected, but the vector sum of the current of each pole detected by the microcomputer is calculated to calculate the ground fault current. Or, it may be configured to detect the leakage current.

Industrial applicability

ADVANTAGE OF THE INVENTION According to this invention, the workability | operativity at the time of assembly is excellent,

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Claims

 1. A circuit breaker that has switching means in the current-carrying conductor from the power supply terminal to the load-side terminal, and opens the switching means when the current flowing through the current-carrying conductor reaches a predetermined condition. A magnetoresistive element arranged in close proximity to the current-carrying conductor, and control means for generating an output when a current flowing through the current-carrying conductor meets predetermined conditions based on the output of the magnetoresistive element And a tripping means driven by an output of the control means to open the opening / closing means.  2. The circuit breaker according to claim 1, wherein said magnetoresistive element is housed in a housing means formed of an insulator and arranged at a position close to said conductive conductor.  3. The above-mentioned magnetoresistive elements are configured as a set of two magnetoresistive elements arranged close to each other, and these two magnetoresistive elements each have a reverse bias magnetic field. The circuit breaker according to claim 1, wherein the circuit breaker is configured to be added.  4. The above-mentioned magnetoresistive element is provided with a coil for applying a bias magnetic field, and is configured to be able to control a current flowing through the coil for applying a bias magnetic field. Circuit breaker according to item 3. 5. A circuit breaker which has a switching means in the current-carrying conductor from the power-supply-side terminal to the load-side terminal and opens the switching means when a current flowing through the current-carrying conductor reaches a predetermined condition. A magnetoresistive element arranged close to the current-carrying conductor; Storage means for storing; control means for generating an output when the current flowing through the current-carrying conductor reaches a predetermined condition based on the output of the magnetoresistive element; and output means for the control means. A circuit breaker, further comprising a tripping means that is driven further to open the opening / closing means, wherein the storage means is arranged at a position close to the current-carrying conductor.