JPS6345728A - Circuit breaker - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Industrial Application Field) The present invention relates to a circuit breaker using a shape memory alloy.

(Conventional technology) An example of a conventional circuit breaker is shown in FIG.

This is a so-called static tripping method, and the main circuit 1
The secondary output of the current transformer 2 provided in each phase is rectified by the rectifier circuit 3, converted into voltage by the current/voltage conversion circuit 4, and then manually input to the long time limit circuit 5, short time limit circuit 6, and instantaneous circuit 7. The configuration is such that each circuit 5 to 7 outputs a trip signal in accordance with the respective time-limiting characteristics when a discharge current occurs such as a short circuit or an overload in the main circuit 1. The tripping signal is generated by the rectifier circuit 3.
Thyristor 9 connected in series with tripping coil 8
By turning on the thyristor 9, a secondary current is caused to flow through the current transformer in the tripping coil 8, and the switching mechanism 10 is tripped.

However, in the above configuration, it is not possible to give the long time limit circuit 5 an inverse time limit characteristic such that the main circuit current I and the operating time t are - constant, taking into consideration the thermal characteristics of the load or electric wire. Since this is necessary, there is a drawback that the circuit configuration becomes complicated. However, in recent years, the number of phase control devices such as inverters has been increasing, and in order to properly protect these devices, it is necessary to perform effective value calculations, making the enclosure configuration even more complex and large-scale. This creates the problem of formalization.

On the other hand, in order to avoid such complications, it has been considered to use a shape memory alloy for the tripping operation (for example, Japanese Utility Model Application Publication No. 49945/1983), but this is because the shape memory alloy is not used in the main circuit. Since it is configured to allow a 7u current to flow, there is a problem in that it cannot be used in a circuit breaker with a large rated current.

(Problems to be Solved by the Invention) As stated above, in order to obtain appropriate overcurrent protection characteristics with conventional static tripping systems, the circuit becomes significantly complicated and large. There was also the problem that it was difficult to increase the capacity by simply using a shape memory alloy.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a circuit breaker which can be simplified and downsized in structure, and which can also be configured to a large rated specification.

[Structure of the Invention] (Means for Solving the Problems) The circuit breaker of the present invention applies a secondary current from a current transformer provided in each of the main circuits to a shape memory alloy. The feature is that the overvoltage tripping operation is performed based on the deformation of the memory alloy.

(effect) A current proportional to the main circuit current flows through the shape memory alloy.

For this reason, the shape memory alloy self-heats, and when it reaches a predetermined transformation temperature, it deforms and performs the overflow pulling operation. Here, the calorific value of the shape memory alloy is proportional to if if the secondary current of the current transformer is i, so the larger the main circuit current, the shorter the time to reach the transformation temperature, and therefore the deformation of the shape memory alloy occurs. The time t until this happens is inversely proportional to il, and an inverse time characteristic matching the thermal characteristics of the load, electric wire, etc. can be obtained. Furthermore, since the secondary current of the current transformer is passed through the shape memory alloy, it is possible to accommodate a wide range of rated currents by appropriately setting the current transformation ratio of the current transformer.

(Embodiment) A first embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

A main circuit 14 is provided between the power supply side terminal 11 and the load side terminal 12 for three phases via a main circuit contact group 13 .

A current transformer 15 is provided in each phase of the main circuit 14, and its secondary side is connected to a rectifier circuit 16. 17 is a tripping device, which is constructed as shown in FIG. In the figure, 18 is a permanent magnet, and pole pieces 19 and 20 are provided at both poles of the permanent magnet, respectively. One pole piece 20 has a movable piece 21 rotatably provided at one end,
The other end is allowed to come into contact with and separate from the tip of the other pole piece 19, and is normally attracted to the pole piece 19 by the magnetic force of the permanent magnet 18. This movable piece 21 operates a well-known detachment mechanism (not shown) for the main circuit contact group 12 provided in the main circuit 14, and rotates in the direction of the arrow from the state of adsorption to the pole piece 19. When separated from the pole piece 19, the main circuit 14 is disconnected. 22 is a magnetic flux canceling coil wound around the pole piece 20. 23 is a shape memory alloy formed into a coil spring shape, one end of which is fixed to the case side (not shown);
The other end is connected to the movable piece 21. shape memory alloy 23
In normal iR, the movable piece 21 is elastically extended by adsorption to the pole piece 19, and if the magnetic force of the permanent magnet 18 decreases, the movable piece 21 is rotated in the direction of the arrow due to the elastic force of the white body. can be done. Moreover, this shape memory alloy 23 is set to contract and deform when heated to a predetermined transformation temperature, and this contraction and deformation also causes the movable piece 21 to rotate in the direction of the arrow against the magnetic attraction 6. can be done.

As shown in FIG. It is designed to allow secondary current to flow. The output voltage from the current/voltage conversion circuit 24 is converted to a short time limit circuit 25 and an instantaneous circuit 2, which are well-known static trip circuits.
6, and the main circuit 14 is short-circuited and
In an accident state such as overcurrent, a tripping signal St is applied to the thyristor 27 according to the respective time limit characteristics to turn it on. This thyristor 27 is connected in series with the magnetic east canceling coil 22 of the tripping device 17 on the DC output side of the rectifier circuit 16, and when turned on, current flows through the magnetic flux canceling coil 22 in a direction that weakens the magnetic flux of the permanent magnet 18. .

Next, the operation of the above configuration will be explained. Tripping device during normal operation! As shown in FIG. 2, the movable piece 21 of ¥17 is attracted to the pole piece 19, and the main circuit contact group 13 is in an open state. When an overcurrent flows through the main circuit 14, the current transformer 1
Since the secondary side of 5 is connected to the shape memory alloy 23 and the current φ voltage conversion circuit 24 via the rectifier circuit 16, a current i proportional to the main circuit current flows through the shape memory alloy 23, and the shape memory alloy 23 self-heats. Here, the amount of heat generated in the shape memory alloy 23 is determined by the main circuit current and the current transformer 15.
Since it is proportional to the square of the secondary current i, the shape memory alloy 23
The time t until the current i reaches the transformation temperature is inversely proportional to the square of the current i. That is, the larger the main circuit current, the greater the amount of heat generated, and the faster the transformation temperature is reached. When the overcurrent continues for a certain period of time and the shape memory alloy 23 reaches a transformation temperature, the shape memory alloy 23 contracts and deforms. With this,
The movable piece 21 of the tripping device 17 rotates in the direction of the arrow in FIG. 2 against the magnetic attraction force of the permanent magnet 18, and is pulled away from the pole piece 19 as shown in FIG. 3, thereby tripping the tripping mechanism. The load is protected by opening the main circuit contact group 13.

In addition, when the overcurrent value of the main circuit 14 is large or in the case of a short circuit accident, etc., the voltage signal from the current/voltage conversion circuit 24 becomes large, so the short time limit circuit 25 or the instantaneous circuit 26
A trip signal St is output from the thyristor 27, and the thyristor 27 is turned on. Then, the secondary current of the current transformer 15 flows through the magnetic flux canceling coil 22 of the tripping device 17, thereby canceling the magnetic flux of the permanent magnet 18, so that the magnetic force 1 and the attractive force decrease, and the shape memory alloy 23 Is the temperature higher? Even without waiting for contraction and deformation due to the elastic contraction force, the movable piece 21 still moves to the second
By rotating in the direction of the arrow in the figure, the main circuit 14 is tripped within a short time.

As described above, in this embodiment, the shape memory alloy 23 is caused to generate self-heating in proportion to the main circuit current, and the shape memory alloy 23 is contracted and deformed due to the temperature rise caused by the heat generation, so that the main circuit 1
The first feature is that the tripping of 4 is performed. As a result, the calorific value of the shape memory alloy 23 is proportional to the square of the main circuit current, so it is extremely easy to obtain inverse timing characteristics, leading to simpler structures, lower costs, smaller size, and higher reliability. - become possible all at once. Moreover, since the amount of heat generated in the shape memory alloy 23 is proportional to the effective value of the main circuit current, it essentially becomes an effective value characteristic, and even if the load is a phase control device or the like and the main circuit current has a phase control waveform, This enables ideal protection that matches the thermal characteristics of the load and wires. Furthermore, the feature of TS2 is that the current transformer 1 is attached to the shape memory alloy 23.
As a result, by appropriately setting the current transformation ratio of the current transformer 15, it can be sufficiently applied to a circuit breaker with a large rated current. . In particular, in this embodiment, the magnetic flux canceling coil 22 is energized by the tripping signal St from the short-time circuit 25 and the instantaneous circuit 26, and the elastic force of the shape memory alloy 23 is utilized to move the movable piece 21. Since the tripping operation is performed by rotating the , there is no need to provide a dedicated electromagnetic device for short-term and instantaneous tripping, and the structure can be further simplified. .

4 and 5 show a second embodiment of the invention.

This is an improved version of the tripping device for operating the tripping mechanism. In the figure, 28 is a case made of magnetic material, 29 is a cylindrical permanent magnet fixed inside the case 28,
30 is a ring-shaped pole piece provided on the inner circumference of the permanent magnet 29. A plunger 31 is provided within the case 28 so as to be movable in the direction of protrusion and retraction, and is prevented from being removed by a stopper ring 32. 33 is a seat made of magnetic material provided coaxially with the plunger 31 at the end inside the case 28;
A large diameter portion 31a formed between this and the plunger 31
A shape memory alloy 34 formed into a coil spring shape is provided between the two. Magnetically, permanent magnet 29, case 28
, the catch 33, the plunger 31, and the pole piece 30 in order to form a magnetic circuit that returns to the permanent magnet 29. As a result, the plunger 31 normally compresses the shape memory alloy 34 elastically to generate its elastic force. It is sucked into the catch seat 33 against the force. This shape memory alloy 34 is elastically compressed as described above when the plunger 31 is sucked into the seat 33, but when it reaches a predetermined transformation temperature, it is elongated and deformed against the magnetic attraction force. The rectifier circuit 16 is connected in series with the current/voltage conversion circuit 24 to the DC output side of the rectifier circuit 16, so that the secondary current of the current transformer 15 flows therethrough. 35 is the shape memory alloy 3 inside the case 28.
A magnetic flux canceling coil is provided to surround the permanent magnet 29, and is connected in series with the thyristor 27 on the DC output side of the rectifier circuit 16 as in the first embodiment, and when the thyristor 27 is turned on, the magnetic flux of the permanent magnet 29 is Generates a canceling magnetic field. This embodiment has the same configuration as the first embodiment except for the tripping device described above.

In the above configuration, when an overcurrent flows in the main circuit 14, the secondary current of the current transformer 15 also flows to the shape memory alloy 34 and the shape memory alloy 34 self-heats, so the shape memory alloy 34 undergoes transformation f'1 When it reaches a certain degree, it is elongated and deformed. As a result, the plunger 31 moves in the protruding direction against the magnetic attraction force of the permanent magnet 29, and the main circuit 14 is tripped by a tripping mechanism (not shown). In addition, when the overcurrent value is large or in the event of a short circuit, the thyristor 27 is turned on and the magnetic flux canceling coil 35 is energized, thereby reducing the magnetic attraction force acting on the plunger 31, causing the shape memory alloy 34 to rebound. The force causes the plunger 31 to move in the protruding direction, and a tripping action is also performed. Even with this configuration, it goes without saying that the same effects as in the first embodiment can be achieved. In addition, the present invention is not limited to the embodiments described above and shown in the drawings, but may be modified within the scope of the gist, such as providing an auxiliary current transformer between the current transformer 15 and the shape memory alloy 23, 34. The invention can be implemented with various modifications within the scope of the invention.

[Effects of the Invention] As stated above, the present invention is characterized in that the secondary current from the current transformer is passed through the shape memory alloy, and as a result, the structure is extremely simple. The shape memory alloy has the excellent effect of being applicable even when the rating of the main circuit fX'ttt is large, since it allows the secondary current of the current transformer to flow through the shape memory alloy. It is something that plays.

[Brief explanation of the drawing]

1 to 3 show a first embodiment of the present invention, FIG. 1 is an overall circuit diagram, FIG. 2 is a sectional view showing a tripping device using a shape memory alloy, and FIG. 3 is the same. 4 and 5 are views corresponding to FIGS. 2 and 3 showing the second embodiment of the present invention, and FIG. 6 is a view equivalent to FIG. 1 showing the conventional example. It is. In the drawing, 14 is a main circuit, 15 is a current transformer, 22.degree. 35 is a magnetic flux canceling coil, and 23.34 is a shape memory alloy. Applicant Toshiba Corporation JPll Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. In order to detect a fault current in the main circuit and perform a tripping operation, a secondary current from a current transformer provided in each phase of the main circuit is applied to a shape memory alloy. A circuit breaker characterized in that an overcurrent tripping operation is performed based on the deformation of the circuit.