Patent Description:
In the case where an internal arc occurs due to short-circuit in a distribution board, the internal arc continues occurring until a circuit breaker of a high-order system operates, and therefore there is a possibility that the board is significantly damaged.

Accordingly, an internal arc protection system is developed in which an internal arc in a power reception distribution board is detected at high speed and grounding is performed at high speed so as to eliminate the internal arc, thereby suppressing damage on the board due to the internal arc. As a high-speed grounding switch used in such an internal arc protection system, a high-speed actuator using gunpowder is known, but this can operate only once.

Meanwhile, an internal arc protection system using an electromagnetic actuator capable of operating a plurality of times is known (for example, Patent Document <NUM>).

Also, a circuit breaker provided with an electromagnetic actuator capable of operating contacts at high speed and a plurality of times is described in Patent Document <NUM>, for example. In an opening operation, when a first coil is energized, operation is performed in the opening direction by an electromagnetic force generated on a repulsive plate, a closing spring is compressed, and a movable core connected to a movable shaft is retained by a retention mechanism. In a closing operation, when a second coil is energized, an attracting force from a permanent magnet of the retention mechanism is canceled out so that the retention is released and the movable core moves in the closing direction by the closing spring.

Further, Patent Document <NUM> discloses another electromagnetic actuator for circuit breaker capable of operating at high speed. At the time of operation (opening), first and second coils are excited, and eddy current is generated in a repulsive plate located close to the first coil. Then, a magnetic field of the first coil and a magnetic field due to the eddy current repel each other, whereby a movable shaft connected to the repulsive plate is driven in the closing direction. The distance between a movable core and a fixed core is decreased by the driving of the movable shaft, and the movable core comes into contact with the fixed core by an electromagnetic force of the second coil. Patent Document <NUM>, according to its abstract, states that in a switchgear, by using a spring with a varying spring constant from closing to electrode opening as a loading spring, spring load in the opened electrode state is made smaller than a spring load in the closed electrode state to decrease the energy required from electrode closing up to electrode opening. Moreover, by using a spring in which a load in the opposite direction to a load in the closed electrode state works in the opened electrode state, the opened electrode state can be held securely.

In Patent Document <NUM>, a high-speed closing switch is realized, and in addition, in order to reduce impact and noise that occur at the time of high-speed closing (electrode closing), a damper hole is provided so that the impact is absorbed by gas inside a case. Therefore, a bar-shaped movable electrode and a cylindrical fixed electrode having a damper hole corresponding thereto are provided, leading to a large-sized and complex structure.

In both Patent Document <NUM> and Patent Document <NUM>, to achieve high-speed operation, a power supply for pulse current is increased in size or a rebound between electrodes which occurs at the time of closing becomes great.

In particular, in Patent Document <NUM>, operation mainly refers to interruption (opening), and in the case of application to closing operation, chattering that occurs at the time of closing is not taken into consideration.

The present disclosure has been made to solve the above problems, and an object of the present disclosure is to achieve high-speed operation of a switch with a simple structure and suppress chattering that occurs due to high-speed operation.

There is provided an electromagnetic actuator as defined in claim <NUM>.

There is further provided a switch as defined in claim <NUM>.

There is further provided a switchgear as defined in claim <NUM>.

Owing to the above configurations, high-speed operation of an electromagnetic actuator can be achieved with a simple structure, a switch can be operated at high speed by the electromagnetic actuator, and chattering can be suppressed.

In the drawings, the same reference characters denote the same or corresponding parts.

<FIG> and <FIG> are structure views of a switch according to embodiment <NUM>. <FIG> shows an opened state, and <FIG> shows a closed state.

In <FIG> and <FIG>, a switch <NUM> includes: a vacuum switch <NUM> having, inside a vacuum container, a fixed electrode <NUM> and a movable electrode <NUM> contactable with and separable from the fixed electrode <NUM> to form a closed/opened state; and an electromagnetic actuator <NUM> for driving a first movable shaft <NUM> having an end connected to the movable electrode <NUM> so as to open/close the vacuum switch.

A terminal <NUM> and a terminal <NUM> are provided outside the vacuum switch <NUM>. The terminal <NUM> is connected to a fixed end of the fixed electrode <NUM>, and the terminal <NUM> is connected to the first movable shaft <NUM>. The terminal <NUM> and the terminal <NUM> respectively serve as a high-voltage-side terminal and a ground-side terminal when the vacuum switch <NUM> is used for opening/closing the circuit.

The electromagnetic actuator <NUM> has a second movable shaft <NUM> connected to the first movable shaft <NUM> via an insulating connection rod <NUM>, and in the electromagnetic actuator <NUM>, a repulsive plate <NUM>, a coil <NUM>, a movable core <NUM>, and a disk spring <NUM> which is an elastic member are arranged in this order from the vacuum switch <NUM> side.

The repulsive plate <NUM> is connected to the second movable shaft <NUM> and moves in the axial direction together with the second movable shaft <NUM>. With a hollow part of the coil <NUM> interposed between the repulsive plate <NUM> and the movable core <NUM>, the movable core <NUM> is connected to the second movable shaft <NUM>. The movable core <NUM> also moves in the axial direction together with the second movable shaft <NUM>.

In the opened state shown in <FIG>, the distance between the repulsive plate <NUM> and the coil <NUM> is set to be shorter than the distance between the movable core <NUM> and the coil <NUM>. In the closed state shown in <FIG>, the distance between the repulsive plate <NUM> and the coil <NUM> is set to be longer than the distance between the movable core <NUM> and the coil <NUM>.

The disk spring <NUM> has an outer peripheral end fixed to a spring fixation member 31a, and an inner peripheral end fixed to the second movable shaft <NUM> by a spring fixation member 31b. In the opened state shown in <FIG>, the second movable shaft <NUM> is pressed by the disk spring <NUM> so as to move away from the vacuum switch <NUM>. In the closed state shown in <FIG>, the second movable shaft <NUM> is pressed by the disk spring <NUM> so as to come close to the vacuum switch <NUM>, thus serving to retain the fixed electrode <NUM> and the movable electrode <NUM> in the vacuum switch <NUM> so that they are not separated from each other.

Next, operation of the electromagnetic actuator <NUM> will be described.

First, in the opened state shown in <FIG>, when high-frequency pulse current is applied to the coil <NUM>, a magnetic field is generated, and due to the magnetic field, eddy current is generated in the repulsive plate <NUM> located close to the coil <NUM>. A magnetic field due to the eddy current generated in the repulsive plate <NUM> has such a direction as to cancel out the magnetic field generated on the coil <NUM>, i.e., a direction opposite to the magnetic field generated on the coil. Thus, the repulsive plate <NUM> moves in a direction to separate from the coil <NUM>. Accordingly, by an electromagnetic force generated on the repulsive plate <NUM>, the repulsive plate <NUM> and the second movable shaft <NUM> connected to the repulsive plate <NUM> move in the closing direction. When the repulsive plate <NUM> is separated from the coil, the electromagnetic force on the repulsive plate <NUM> is reduced.

An electromagnetic force from the coil <NUM> acts so as to attract the movable core <NUM> toward the coil <NUM>. In the opened state, since the distance between the movable core <NUM> and the coil <NUM> is great, the electromagnetic force generated on the movable core <NUM> is small, and through movement of the repulsive plate <NUM>, as the distance between the movable core <NUM> and the coil <NUM> decreases, the electromagnetic force generated on the movable core <NUM> increases.

In the opened state, the second movable shaft <NUM> is fixed by the disk spring <NUM>, and after the coil <NUM> is energized, when the movable shaft <NUM> is moved by a predetermined distance, the disk spring <NUM> is reversed and presses the second movable shaft <NUM> toward the closing side as shown in <FIG>.

<FIG> shows changes over time in current flowing through the coil, displacement of the movable electrode, and electromagnetic forces generated on the repulsive plate and the movable core. In <FIG>, <NUM> denotes coil current flowing when the coil <NUM> is energized, <NUM> denotes displacement of the movable electrode <NUM>, <NUM> denotes a repulsive plate electromagnetic force generated on the repulsive plate <NUM>, and <NUM> denotes a movable core electromagnetic force generated on the movable core <NUM>. The displacement <NUM> of the movable electrode corresponds to displacement of the second movable shaft <NUM>.

When current flows through the coil <NUM>, the electromagnetic force <NUM> generated on the repulsive plate <NUM> sharply rises. By the electromagnetic force <NUM>, the movable electrode <NUM>, i.e., the second movable shaft <NUM> starts to move as shown by the displacement <NUM>. Thereafter, the electromagnetic force <NUM> by the repulsive plate <NUM> reaches a peak.

On the other hand, the electromagnetic force <NUM> generated on the movable core <NUM> rises with a lag from the electromagnetic force <NUM> generated on the repulsive plate <NUM>, and then reaches a peak. Therefore, in the vicinity of the closed position, the electromagnetic force <NUM> of the movable core <NUM> becomes great, that is, a force to move the movable electrode <NUM> toward the fixed electrode <NUM> via the second movable shaft <NUM> becomes great, thus suppressing chattering when the movable electrode <NUM> collides with the fixed electrode <NUM>.

In <FIG>, the vicinity of the closed position is the position of the movable electrode <NUM> at the time when the displacement <NUM> becomes flat.

When the movable electrode <NUM> collides with the fixed electrode <NUM>, rebound of the movable electrode <NUM> is suppressed by an elastic force of the disk spring <NUM>, whereby chattering can be further suppressed. At the time of closing, the disk spring <NUM> presses the second movable shaft <NUM> in the moving direction of the second movable shaft <NUM>, thus contributing to suppression of chattering.

As shown in <FIG>, the displacement <NUM> of the second movable shaft <NUM> is kept flat with almost no oscillation, after collision.

Regarding the repulsive plate <NUM>, the electromagnetic force relationship shown in <FIG> can be adjusted by the material, conductivity, the radial-direction size from the movable shaft, the thickness, or the like thereof. Examples of the material include copper and aluminum. In light of rigidity as the driving member, a copper-based material is desirable. The size in the radial direction is set to be approximately equal to the diameter of the coil.

Regarding the movable core <NUM>, the size in the radial direction is set to be approximately equal to or smaller than the diameter of the coil, and can be set together with the thickness thereof in consideration of the weight and drivability as an apparatus.

After it is confirmed that contact-to-contact current conduction between the fixed electrode <NUM> and the movable electrode <NUM> is stopped, an opening operation is performed. As a mechanism for performing an opening operation, a simple manual mechanism may be provided. Although not shown, for example, the movable shaft <NUM> may be provided with a screw portion, and a feed mechanism for driving the movable shaft <NUM> in the opening direction by using the screw portion may be attached. In this case, it is desirable that the mechanism is detachable from the movable shaft <NUM> so as not to influence the closing operation. A link mechanism may be attached to the movable shaft and a handle that allows a manual opening operation may be attached. When the movable shaft <NUM> is moved to an opened-state position by using such a mechanism, the movable shaft <NUM> is kept at the opened position by the disk spring <NUM> which is an elastic member.

As described above, in the present embodiment <NUM>, the electromagnetic actuator <NUM> has the repulsive plate <NUM> and the movable core <NUM> connected to the second movable shaft <NUM> so as to be opposed to each other with the coil <NUM> interposed therebetween. In a first state, the distance between the repulsive plate <NUM> and the coil <NUM> is set to be shorter than the distance between the movable core <NUM> and the coil <NUM>, and the disk spring <NUM> connected to the second movable shaft <NUM> presses the second movable shaft <NUM>. After the coil <NUM> is energized, when the second movable shaft <NUM> is operated so that a second state is established, the distance between the repulsive plate <NUM> and the coil <NUM> becomes longer than the distance between the movable core <NUM> and the coil <NUM>, and the disk spring <NUM> is reversed to press the second movable shaft <NUM>. Thus, by using two electromagnetic forces acting on the repulsive plate <NUM> and the movable core <NUM> in combination, it is possible to provide an electromagnetic actuator capable of high-speed operation with high efficiency as compared to the conventional technology.

In addition, the electromagnetic force on the movable core <NUM> reaches a peak with a lag from the electromagnetic force on the repulsive plate <NUM>. Therefore, the electromagnetic force can be increased in the vicinity of the position to which the second movable shaft <NUM> moves at high speed by a predetermined distance, and thus rebound between the electrodes can be reduced. Further, owing to the elastic force of the disk spring <NUM>, the second movable shaft <NUM> can stop with a small rebound after moving by the predetermined distance.

Only one coil <NUM> is provided for generating the electromagnetic forces on the repulsive plate <NUM> and the movable core <NUM>. Therefore, it is possible to provide a small-sized electromagnetic actuator as compared to the conventional ones.

In embodiment <NUM>, the switch <NUM> is configured such that the movable electrode <NUM> is connected to the second movable shaft <NUM> of the electromagnetic actuator <NUM> described above and the electromagnetic actuator <NUM> is used as a driving device for the vacuum switch <NUM> so that the movable electrode <NUM> collides with the fixed electrode <NUM> to perform a closing operation. Thus, since the electromagnetic force on the movable core <NUM> reaches a peak with a lag from the electromagnetic force on the repulsive plate <NUM>, the electromagnetic force can be increased in the vicinity of the closed position, whereby rebound when the movable electrode <NUM> collides with the fixed electrode can be suppressed and chattering can be suppressed. Further, the elastic force of the disk spring <NUM> also acts, whereby chattering can be further suppressed.

Since the small-sized electromagnetic actuator which generates the electromagnetic forces on the repulsive plate <NUM> and the movable core <NUM> by one coil is used, the switch <NUM> can also be downsized.

In the above embodiment <NUM>, the movable core and the disk spring which is an elastic member are provided separately from each other. On the other hand, in the present embodiment <NUM>, an example in which the movable core and the disk spring which is an elastic member are connected to each other and thus are connected to the second movable shaft will be described.

<FIG> and <FIG> are structure views of a switch according to embodiment <NUM>. <FIG> shows an opened state. <FIG> shows a closed state.

In <FIG> and <FIG>, a switch <NUM> includes: a vacuum switch <NUM> having therein a fixed electrode <NUM> and a movable electrode <NUM> contactable with and separable from the fixed electrode <NUM> to form a closed/opened state; and an electromagnetic actuator <NUM> for driving a first movable shaft <NUM> having an end connected to the movable electrode <NUM> so as to open/close the vacuum switch.

The electromagnetic actuator <NUM> has a second movable shaft <NUM> connected to the first movable shaft <NUM> via an insulating connection rod <NUM>, and in the electromagnetic actuator <NUM>, a repulsive plate <NUM>, a coil <NUM>, and a movable core <NUM> are arranged in this order from the vacuum switch <NUM> side.

As in embodiment <NUM>, the repulsive plate <NUM> is connected to the second movable shaft <NUM> and operates in the axial direction together with the second movable shaft <NUM>. With a hollow part of the coil <NUM> interposed between the repulsive plate <NUM> and the movable core <NUM>, the movable core <NUM> is connected to the second movable shaft <NUM>. The movable core <NUM> also operates in the axial direction together with the second movable shaft <NUM>.

In the present embodiment <NUM>, the movable core <NUM> is connected to the inner peripheral end of the disk spring <NUM>, thereby fixing the disk spring <NUM> to the second movable shaft <NUM>. As in embodiment <NUM>, the outer peripheral end of the disk spring <NUM> is fixed to the spring fixation member 31a, and thus the position of the outer peripheral end is kept even when the second movable shaft <NUM> is moved. In the opened state shown in <FIG>, the second movable shaft <NUM> is pressed at a position away from the vacuum switch <NUM> by the disk spring <NUM>. In the closed state shown in <FIG>, the second movable shaft <NUM> is pressed at a position close to the vacuum switch <NUM> by the disk spring <NUM> reversing from the opened state, thus retaining the fixed electrode <NUM> and the movable electrode <NUM> in the vacuum switch <NUM> so that they are not separated from each other.

Operation of the electromagnetic actuator <NUM> is the same as in embodiment <NUM>. When high-frequency pulse current is applied to the coil <NUM>, a magnetic field is generated. With respect to the electromagnetic force due to the magnetic field, two electromagnetic forces acting on the repulsive plate <NUM> and the movable core <NUM> are used in combination.

First, the electromagnetic force on the repulsive plate <NUM> rises, and the second movable shaft <NUM> is driven by operation of the repulsive plate <NUM>. The electromagnetic force on the movable core <NUM> reaches a peak with a lag from the electromagnetic force on the repulsive plate <NUM>. Therefore, in the vicinity of the position to which the second movable shaft <NUM> moves at high speed by a predetermined distance, i.e., the vicinity of the position where the movable electrode <NUM> comes into contact with the fixed electrode <NUM>, the electromagnetic force can be increased, whereby rebound between the electrodes can be reduced. Further, the second movable shaft <NUM> is held by the elastic force of the disk spring <NUM>, whereby the second movable shaft <NUM> can stop with a small rebound after moving by the predetermined distance.

In embodiment <NUM>, the movable core <NUM> and the disk spring <NUM> are individually connected to the second movable shaft <NUM>, whereas, in embodiment <NUM>, the movable core <NUM> serves also as a fixation member on the inner peripheral end side of the disk spring <NUM>, and therefore the length in the movable shaft direction is shortened, leading to size reduction in the electromagnetic actuator <NUM> and the switch <NUM>.

Meanwhile, in embodiment <NUM>, since the movable core <NUM> serves also as a fixation member on the inner peripheral end side of the disk spring <NUM>, the area of the movable core <NUM> that is opposed to the coil <NUM> is reduced. Therefore, in order to ensure the electromagnetic force generated on the movable core as shown in <FIG>, it is also important to ensure the area of the movable core <NUM>. However, considering the size of the movable core <NUM> as a fixation member for the disk spring <NUM>, increase in the size makes it more difficult to ensure the elastic force of the disk spring <NUM> or leads to increase in the size of the disk spring <NUM>.

Therefore, the size of the movable core <NUM> in the radial direction, i.e., the area thereof opposed to the coil <NUM> is set to the maximum area that can ensure a certain elastic force of the disk spring <NUM> without too much increase in the size of the disk spring <NUM>, while the thickness of the movable core <NUM> is adjusted. The setting is to be made in consideration of the weight and drivability of the apparatus, i.e., the electromagnetic actuator <NUM> or the switch <NUM>, while ensuring the electromagnetic force generated on the movable core <NUM>.

Thus, the configuration of the present embodiment <NUM> provides the same effects as in embodiment <NUM>. Further, the movable core <NUM> and the disk spring <NUM> which is an elastic member are connected to each other and thus are connected to the second movable shaft <NUM>, and the movable core <NUM> is used as a fixation member on the inner peripheral end side of the disk spring <NUM>. Thus, in addition to the effects of embodiment <NUM>, the length in the movable shaft direction is shortened, thereby providing the electromagnetic actuator <NUM> or the switch <NUM> having a further reduced size.

In addition, the member for connecting the disk spring <NUM> which is an elastic member to the second movable shaft <NUM> is integrated with the movable core <NUM> which thus serves also as the connecting member, whereby increase in the weight of the movable part can be suppressed and increase in the size of the power supply (not shown) for energizing the coil <NUM> can also be suppressed.

In the present embodiment <NUM>, another example in which the movable core and the disk spring which is an elastic member are connected to each other and thus are connected to the second movable shaft as shown in embodiment <NUM> will be described.

In the present embodiment <NUM>, the movable core <NUM> includes: a movable core 24a connected to the inner peripheral end of the disk spring <NUM>, thereby serving to fix the disk spring <NUM> to the second movable shaft <NUM>; and a movable core projection 24b projecting toward the coil <NUM> side.

As in embodiments <NUM> and <NUM>, the outer peripheral end of the disk spring <NUM> is fixed to the spring fixation member 31a, and thus the position of the outer peripheral end is kept even when the second movable shaft <NUM> is moved. In the opened state shown in <FIG>, the second movable shaft <NUM> is pressed at a position away from the vacuum switch <NUM> by the disk spring <NUM>. In the closed state shown in <FIG>, the second movable shaft <NUM> is pressed in a closed state of the vacuum switch <NUM> by the disk spring <NUM> reversing from the opened state, thus retaining the fixed electrode <NUM> and the movable electrode <NUM> in the vacuum switch <NUM> so that they are not separated from each other.

In addition, in the opened state shown in <FIG>, the distance between the repulsive plate <NUM> and the coil <NUM> is set to be shorter than the distance between the movable core 24a and the coil <NUM>, and in the closed state shown in <FIG>, the distance between the repulsive plate <NUM> and the coil <NUM> is set to be longer than the distance between the movable core 24a and the coil <NUM>.

Operation of the electromagnetic actuator <NUM> is the same as in embodiments <NUM> and <NUM>. When high-frequency pulse current is applied to the coil <NUM>, a magnetic field is generated. With respect to the electromagnetic force due to the magnetic field, two electromagnetic forces acting on the repulsive plate <NUM> and the movable core <NUM> are used in combination.

Next, the size and the shape of the movable core will be described.

For increasing an attraction force acting on the movable core, it is necessary to consider the following fact so that response is not lowered due to weight increase and coil inductance increase. If the coil inductance is excessively increased, rising of the coil current shown in <FIG> is lowered and thus the electromagnetic force on the repulsive plate is also reduced, so that response might be deteriorated on the contrary.

It is desirable that the diameter of the movable core shown in embodiment <NUM> is approximately equal to the outer diameter of the coil, and if the diameter is excessively large, the weight and the coil inductance increase. The thickness needs to be set considering the intensity for the electromagnetic force.

It is difficult to make the diameter of the movable core shown in embodiment <NUM> approximately equal to the outer diameter of the coil. Therefore, weight increase, coil inductance increase, and the intensity of the electromagnetic force are adjusted by the thickness.

In the movable core <NUM> having the projection shown in the present embodiment <NUM>, it is desirable that the projection height of the movable core projection 24b is set such that the projection end is flush with the coil surface at an opened position. If the projection height is excessively great, the weight and the coil inductance increase. In addition, the outer diameter of the movable core projection 24b is set to be smaller than the inner diameter of the coil <NUM> so that the movable core projection 24b can enter the hollow part of the coil <NUM> at a closed position.

Thus, the configuration of the present embodiment <NUM> provides the same effects as in embodiments <NUM> and <NUM>.

Further, the movable core <NUM> has the movable core projection 24b projecting to the inner-diameter side of the coil <NUM>. Thus, it is possible to increase the electromagnetic force on the movable core <NUM> and increase the entire output of the electromagnetic actuator <NUM>, without increasing the apparatus size.

In embodiments <NUM> to <NUM>, examples in which the disk spring is used as an elastic member have been shown. However, other elastic members may be employed.

<FIG> are views showing the structure of a part of a switch according to embodiment <NUM>, and show an example in which a link mechanism <NUM> is used instead of the disk spring <NUM> which is an elastic member and the spring fixation members 31a, 31b shown in <FIG> and <FIG> in embodiment <NUM>. <FIG> shows an opened state, and <FIG> shows a closed state.

In the drawings, the link mechanism <NUM> includes a spring <NUM>, a fixation member 34a which rotatably fixes one end of the spring <NUM>, and a fixation member 34b which rotatably fixes the other end of the spring <NUM> to the second movable shaft <NUM>. Between the opened position shown in <FIG> and the closed position shown in <FIG>, the direction of the spring <NUM> is changed, and thus the direction of a force acting on the second movable shaft <NUM> is reversed.

For example, in the case where the spring <NUM> is a compression spring, the force of the spring <NUM> acts on the second movable shaft <NUM> so as to press the second movable shaft <NUM> in the opening direction at the opened position and in the closing direction at the closed position.

<FIG> shows an example in a closed state in the case where a plurality of the link mechanisms <NUM> are arranged at positions symmetry with respect to the second movable shaft <NUM>. Such arrangement enables equal forces to be applied in the axial direction of the second movable shaft <NUM>.

As in the case of the disk spring shown in embodiment <NUM>, the fixation member 34b of the spring <NUM> may be provided to the movable core <NUM> connected to the second movable shaft <NUM>. <FIG> show examples in an opened state in the case where the fixation member 34b of the spring <NUM> is provided to the movable core <NUM> connected to the second movable shaft <NUM>.

In <FIG>, as a matter of course, the movable core projection 24b may be provided to the movable core <NUM> as in embodiment <NUM>.

Next, an example in which a magnetic latch mechanism is used will be described.

<FIG> are views showing another structure of a part of the switch according to embodiment <NUM>, and show an example in which a magnetic latch mechanism <NUM> is used instead of the disk spring <NUM> which is an elastic member and the spring fixation members 31a, 31b shown in <FIG> and <FIG> in embodiment <NUM>. <FIG> shows an opened state, and <FIG> shows a closed state.

In the drawings, the magnetic latch mechanism <NUM> is configured such that an attraction plate <NUM> connected to the second movable shaft <NUM> is attracted and retained to the fixed core <NUM> by a magnetic force of a permanent magnet <NUM>, whereby an opened state is kept with a closing spring <NUM> compressed. On the other hand, in a closing operation, when the attraction plate <NUM> is pulled apart, the gap between the permanent magnet <NUM> and the attraction plate <NUM> is expanded, so that the magnetic force is weakened, and the force of the closing spring <NUM> acts on the movable shaft <NUM> in the closing direction.

The attraction plate <NUM> is made of a magnetic material and desirably has a high resistivity. In the present embodiment, an iron-based attraction plate is used.

As described above, an example in which the link mechanism is used and an example in which the magnetic latch mechanism is used have been shown as elastic members other than the disk spring. In either example, it is possible to apply a force to the movable shaft <NUM> in the opening direction at an opened position and in the closing direction at the closed position, as in the case of the disk spring.

Thus, the configuration of the present embodiment <NUM> provides the same effects as in embodiments <NUM> to <NUM>.

Although an opening operation is not shown in the above embodiments <NUM> to <NUM>, as a matter of course, the opening operation can be performed in the same manner as in embodiment <NUM>.

In the present embodiment <NUM>, an example of a switchgear to which the switch described in any of embodiments <NUM> to <NUM> is mounted as a high-speed switch will be described.

<FIG> is a schematic view showing the structure of a switchgear <NUM> according to embodiment <NUM>.

In <FIG>, a circuit breaker <NUM> is provided between a high-order system and the downstream side, and a current sensor <NUM> is connected on the downstream side of the circuit breaker <NUM>. Inputted power is transmitted to the downstream side and leads to a low-order distribution board via downstream circuit breakers <NUM>, <NUM>.

The switch <NUM> is connected in parallel to the downstream circuit breakers <NUM>, <NUM>. When an arc detection unit <NUM> detects an arc occurrence position <NUM>, the switch <NUM> operates in response to the corresponding signal.

An example in which two downstream circuit breakers <NUM>, <NUM> are provided is shown, but the number of downstream circuit breakers is not limited to two.

In <FIG>, the switch <NUM> is any of the switches <NUM> shown in embodiments <NUM> to <NUM>.

In <FIG>, the terminal <NUM> of the switch <NUM> is connected to a terminal 4a and the terminal <NUM> of the switch <NUM> is connected to a terminal 5a, and the terminal 4a serves as a high-voltage-side terminal and the terminal 5a serves as a ground-side terminal. In the case where the switch <NUM> is mounted to the switchgear <NUM>, since the terminal 5a is used as a ground-side terminal, the connection rod <NUM> connecting the first movable shaft <NUM> and the second movable shaft <NUM> does not necessarily need to be an insulating material.

When short-circuit occurs at the arc occurrence position <NUM> and an arc occurs, the current sensor <NUM> detects change in current. When the arc detection unit <NUM> has received information from the current sensor <NUM>, the arc detection unit <NUM> transmits a command for closing to a control system (not shown) for the switch <NUM>, whereby the switch <NUM> is closed. The circuit in the switchgear <NUM> is grounded, short-circuit current flows to the ground, and the arc is immediately eliminated.

In the case where a short-circuit accident has occurred, current is supplied from the upstream side until power is interrupted by the upstream circuit breaker <NUM>, so that damage in the switchgear <NUM> progresses due to the arc. Therefore, it is desired to ground the short-circuit current at high speed by the time when the circuit breaker <NUM> operates. Grounding the short-circuit current at high speed enables reuse of devices in the switchgear <NUM>.

In the present embodiment, since any of the switches <NUM> shown in embodiments <NUM> to <NUM> is mounted as a high-speed switch, grounding can be performed at high speed after occurrence of an arc and chattering at the time of closing is suppressed, thus enabling restoration and plural times of usage as a high-speed switch. Since the switch is mounted inside the board, size reduction is required. The switch <NUM> according to the present embodiment has a reduced size as compared to the conventional ones, and thus satisfies such requirements.

In <FIG>, an example in which current change due to short-circuit current is detected using a known current sensor has been shown as an arc detection method. However, an arc may be detected by means of light, as shown in <FIG>.

<FIG> is a schematic view showing another structure of the switchgear <NUM>. In <FIG>, when a short-circuit accident has occurred, an arc detection sensor <NUM> detects light due to an arc at an arc occurrence position <NUM>, and transmits information thereof to an arc detection unit <NUM>. The arc detection unit <NUM> transmits a command for closing to a control system (not shown) for the switch <NUM>, whereby the switch <NUM> is closed. Short-circuit current flows to the ground, and the arc is immediately eliminated.

Occurrence of an arc may be detected using the current sensor <NUM> in <FIG> and the arc detection sensor <NUM> which detects light in <FIG> in combination. Further, the detection method is not limited to a method using current or light, as long as an arc can be detected.

The arc detection unit <NUM> stores, in advance, the value of current flowing in the switchgear <NUM> in a steady state, an allowable change range thereof, etc., for example. Thus, the arc detection unit <NUM> compares the value detected by the current sensor <NUM> when an arc has occurred, with the above value, range, etc., to perform arc occurrence determination. In addition, the arc detection unit <NUM> stores data of light emission due to an arc, for example, and thus performs arc occurrence determination on the basis of light emission information from the arc detection sensor <NUM>. When the arc detection unit <NUM> determines that an arc has occurred, the arc detection unit <NUM> transmits a closing command to the switch <NUM>.

In <FIG> and <FIG>, a signal from the arc detection unit <NUM> is transmitted to the switch <NUM>. This signal is also transmitted to the circuit breaker <NUM> at the same time. The short-circuit current is grounded by the switch <NUM> which is a high-speed switch, to eliminate the arc, and thereafter, interruption from the upstream side is performed by the circuit breaker <NUM>, whereby the switchgear <NUM> is protected.

Until interruption by the circuit breaker <NUM>, the movable electrode <NUM> of the switch <NUM> is pressed in the closing direction by the electromagnetic force on the movable core or by the elastic member.

An opening operation in a restoration work after the accident is as follows. In a power stopped state, an opening operation can be performed at low speed. Therefore, a manual opening mechanism may be attached to the movable shaft. Although not shown, for example, the movable shaft <NUM> may be provided with a screw portion, and a feed mechanism for driving the movable shaft <NUM> in the opening direction by using the screw portion may be attached. It is desirable that the mechanism is detachable from the movable shaft <NUM> so as not to influence the closing operation. Alternatively, a link mechanism may be attached to the movable shaft and a handle that allows a manual opening operation may be attached.

As described above, in the configuration of the present embodiment <NUM>, any of the switches described in embodiments <NUM> to <NUM> which are high-speed switches is mounted to the switchgear <NUM>. Therefore, the switch has a reduced size and can be provided inside a predetermined board of the switchgear <NUM>. In addition, the electromagnetic actuator of the switch operates at high speed to close the switch. Therefore, when an arc has occurred, the arc is immediately eliminated, whereby damage in the switchgear <NUM> can be reduced. In addition, since chattering is suppressed in the mounted switch, damage on contact surfaces of the movable electrode and the fixed electrode at the time of closing is suppressed, thus enabling plural times of usage.

Further, since an arc occurrence accident can be immediately calmed down, the restoration time after the accident can be shortened and operation confirmation can be performed. Thus, it becomes possible to provide a switchgear with high reliability.

In the above embodiments <NUM> to <NUM>, the case where the switch <NUM> has the vacuum switch <NUM> has been described. Using such a vacuum switch having electrodes provided in a vacuum container has an advantage that the gap at the time of opening can be reduced.

In the case of a switchgear or a distribution board having a comparatively low rated voltage, e.g., about <NUM> V or less, a switch in which gas or air is sealed may be used without having to use a vacuum switch.

Claim 1:
An electromagnetic actuator (<NUM>) comprising:
a repulsive plate (<NUM>), a coil (<NUM>) and a movable core (<NUM>,<NUM>,24a) connected to a movable shaft (<NUM>) penetrating the coil (<NUM>), and provided so as to be opposed to each other with the coil (<NUM>) interposed therebetween; and
an elastic member (<NUM>,<NUM>,<NUM>) having an end connected to the movable shaft (<NUM>) via the movable core(<NUM>,<NUM>,24a), and another end fixed, wherein
in a first state, a distance between the repulsive plate (<NUM>) and the coil (<NUM>) is smaller than a distance between the movable core (<NUM>,<NUM>,24a) and the coil (<NUM>),
when the coil (<NUM>) is energized and the movable shaft (<NUM>) moves with the repulsive plate (<NUM>) repelling the coil (<NUM>) due to an electromagnetic force acting on the repulsive plate (<NUM>) so that a second state is established, the distance between the repulsive plate (<NUM>) and the coil (<NUM>) becomes greater than the distance between the movable core (<NUM>,<NUM>,24a) and the coil (<NUM>), and the movable shaft (<NUM>) is pressed by the elastic member (<NUM>,<NUM>,<NUM>) in a moving direction of the movable shaft (<NUM>) so as to separate the repulsive plate (<NUM>) from the coil (<NUM>),
characterized in that
the movable core (<NUM>) has a projection (24b) projecting toward the coil (<NUM>) along the movable shaft (<NUM>), and an outer diameter of the projection (24b) of the movable core (<NUM>) is smaller than an inner diameter of the coil (<NUM>).