CN218602356U - Drive device for tripping device and circuit breaker - Google Patents

Abstract

Embodiments of the present disclosure relate to a driving apparatus for a trip device and a circuit breaker. The drive device includes: the driving piece is suitable for driving the moving contact of the tripping device to move from a closing position to a tripping position; and an electromagnetic actuator configured to drive the driver and including: a stationary core; a coil; a plunger arranged opposite the stationary plunger and fixedly attached to the driver, wherein the plunger is configured to move towards the stationary plunger to drive the driver to move in response to a change in current of the coil exceeding a current threshold, the current threshold being related to a fault current of the coil, wherein the electromagnetic actuator further comprises a holding device, wherein the holding device is configured to hold the plunger at a predetermined position when the change in current of the coil does not exceed the current threshold. The technical scheme of the utility model can reduce the resistance that the removal of movable iron core during fault current received to this drive arrangement's response speed has been improved.

Description

Drive device for tripping device and circuit breaker

Technical Field

Embodiments of the present disclosure relate generally to electrical protection equipment, and more particularly, to a driving device for a trip device and a circuit breaker including the driving device.

Background

Circuit breakers are an important part of electrical distribution equipment. An actuator (also referred to as an actuating device, commonly referred to as a trip) in a circuit breaker is an important component of the circuit breaker. An actuator is mechanically coupled to the circuit breaker for releasing the retention mechanism and causing the circuit breaker to automatically open. The function of the protection circuit is to cut off the power supply when the circuit is over-current, thereby playing a role of protection.

In certain applications, it is desirable for a circuit breaker to have a very high response speed to ensure line safety. The response speed of the circuit breaker is determined by the actuator. For some conventional circuit breakers, the response speed may not meet this requirement.

Therefore, there is a need for an improved solution to enable improved performance of the actuator.

SUMMERY OF THE UTILITY MODEL

It is an object of the present disclosure to provide a drive arrangement for a trip device that at least partially addresses the above-referenced problems, as well as other potential problems.

In a first aspect, embodiments of the present disclosure provide a drive for a trip device. The driving device includes: the driving piece is suitable for driving the movable contact of the tripping device to move from a closing position to a tripping position; and an electromagnetic actuator configured to drive the driver and including: a stationary core; a coil; a plunger disposed opposite the stationary plunger and fixedly attached to the driver, wherein the plunger is configured to move toward the stationary plunger to drive the driver to move in response to a change in current of the coil exceeding a current threshold related to a fault current of the coil, wherein the electromagnetic actuator further comprises a holding device, wherein the holding device is configured to hold the plunger at a predetermined position when the change in current of the coil does not exceed the current threshold.

In the above embodiment, by providing the holding means in the electromagnetic actuator, the resistance to the movement of the plunger during the fault current can be reduced, thereby improving the response speed of the driving apparatus.

In some embodiments, the holding means includes a permanent magnet configured to attract the plunger by a magnetic force to hold the plunger at a predetermined position, and the permanent magnet is fixedly disposed at a side of the plunger away from the stationary core so that the plunger moves against the action of the magnetic force upon a fault current.

In the above embodiment, the permanent magnet is provided instead of the reaction spring, so that the response speed of the movable iron core is greatly improved in the case of fault current.

In some embodiments, the electromagnetic actuator further includes a spring, wherein the movable core is moved toward the stationary core against an elastic force of the spring when the fault current occurs, and is returned to the predetermined position under the elastic force of the spring when the fault current is eliminated.

In the above embodiment, the spring does not apply a large elastic force to the plunger in the normal state, and is mainly used for returning the plunger to the predetermined position under the elastic force of the spring when the fault current is eliminated. Therefore, the resistance of the movable iron core during the movement of the fault current is reduced, and the response speed of the device is improved.

In some embodiments, the spring is configured to: the spring is in a natural state or substantially in a natural state in a state where the movable iron core is not moved toward the stationary iron core.

In the above-described embodiment, by making the spring in a natural state or substantially in a natural state, rather than in an elastic state, in a state where the movable core is not moving toward the stationary core, it is possible to reduce the resistance to the movement of the movable core during a fault current, contributing to speeding up the movement of the movable core.

In some embodiments, the permanent magnet and the plunger are disposed with a gap therebetween.

In the above-described embodiment, by providing the gap between the permanent magnet and the movable iron core, the attractive force between the permanent magnet and the movable iron core can be adjusted, so that the flexibility of design can be increased.

In some embodiments, the size of the gap is adjustable.

In the above embodiment, by setting the size of the gap to be adjustable, the attractive force between the permanent magnet and the movable iron core can be conveniently adjusted according to actual needs, thereby increasing the flexibility of design.

In some embodiments, the electromagnetic actuator may further include a magnetic medium disposed in the gap.

In the embodiment, the magnetic medium is arranged, so that the distribution of the magnetic field can be changed, and the magnetic force between the permanent magnet and the movable iron core can be adjusted more conveniently and rapidly.

In some embodiments, the electromagnetic actuator further comprises a stopper abutting the plunger to prevent the plunger from moving toward the permanent magnet.

In the above embodiment, by providing the actuator, the gap between the permanent magnet and the movable iron core can be set as needed so that a predetermined magnetic force is maintained therebetween.

In some embodiments, the electromagnetic actuator comprises a linear electromagnetic actuator, wherein the plunger is configured to move linearly to drive the driver in linear motion.

In the above-described embodiment, by providing the linear electromagnetic actuator, the quick response of the trip device can be achieved with a simple structure.

In some embodiments, the electromagnetic actuator comprises a rotary electromagnetic actuator, wherein the plunger is configured to move rotationally to drive rotation of the driver.

In the above embodiment, by providing the rotary electromagnetic actuator, it is possible to realize the activation of the protection mechanism that needs to be rotationally activated as needed.

In a second aspect, embodiments of the present disclosure also provide a circuit breaker including the driving device for a trip device of the first aspect of the present disclosure.

The following detailed description is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. The summary is not intended to identify key features or essential features of the disclosure, nor is it intended to limit the scope of the disclosure.

Drawings

Fig. 1 shows a schematic diagram of a drive arrangement for a trip device according to one embodiment of the present disclosure;

fig. 2 shows a schematic diagram of a drive arrangement for a trip device according to another embodiment of the present disclosure; and

fig. 3 shows a schematic diagram of the driving device for the trip device shown in fig. 2 in a fault current state according to one embodiment of the present disclosure;

like or corresponding reference characters designate like or corresponding parts throughout the several views.

Detailed Description

The principles of the present disclosure will be described with reference to various exemplary embodiments shown in the drawings. It should be understood that these examples are described merely to enable those skilled in the art to better understand and further implement the present disclosure, and are not intended to limit the scope of the present disclosure in any way. It should be noted that where feasible, similar or identical reference numerals may be used in the figures and that similar or identical reference numerals may indicate similar or identical functions. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the invention described herein.

The term "include" and variations thereof as used herein is meant to be inclusive in an open-ended manner, i.e., "including but not limited to". The term "or" means "and/or" unless specifically stated otherwise. The term "based on" means "based at least in part on". The terms "one example embodiment" and "one embodiment" mean "at least one example embodiment". The term "another embodiment" means "at least one additional embodiment". The terms "first," "second," and the like may refer to different or the same objects.

As mentioned above, the known actuators have the drawback of relatively low response speed. Therefore, there is a need for an improved solution to overcome the above-mentioned drawbacks

Embodiments of the present disclosure provide improved drive arrangements for trip devices. In some embodiments of the present disclosure, a driving apparatus for a trip device includes: a drive member and an electromagnetic actuator. Wherein the driving member is suitable for driving the movable contact of the tripping device to move from the closing position to the tripping position. The electromagnetic actuator is configured to drive a driving member, and includes a stationary core, a coil, and a movable core. Wherein the movable iron core is arranged opposite to the stationary iron core and is fixedly attached to the driving member. Wherein the plunger is configured to move towards the stationary core to drive the driver to move in response to a change in current of the coil exceeding a current threshold, the current threshold being related to a fault current of the coil. Wherein the electromagnetic actuator further comprises a holding device, wherein the holding device is configured to hold the plunger at a predetermined position when the change in current of the coil does not exceed the current threshold. In this way, by providing the holding means in the electromagnetic actuator, the resistance to the movement of the plunger during a fault current can be reduced, thereby increasing the speed of movement of the plunger, i.e., the speed of movement of the driving member. Thereby improving the response speed of the driving device.

The trip device may include a device for implementing a trip function in the circuit breaker, such as a trip unit. The trip device is not limited thereto but may include any device having a trip function in case of a fault. Trip units typically structurally include a drive (otherwise known as an actuator or actuator) and a trigger mechanism. The trigger mechanism includes a movable contact which is normally in a closed position and moves to a tripped position in the event of a fault.

Fig. 1 shows a schematic view of a drive device 100 according to one embodiment of the present disclosure. The driving device comprises a driving piece and an electromagnetic actuator. In some embodiments, as shown in FIG. 1, the drive member may be, for example, a ram 110. One end of the stem lifter 110 may include a contact portion 116. The contact portion 116 may be adapted to interact with the movable contact of the trip device during a fault current to cause the movable contact of the trip device to move from a closed position to a tripped position to achieve overcurrent protection. The electromagnetic actuator is configured to drive the driver. The electromagnetic actuator includes a stationary core 102, a coil 106, and a movable core 102. Wherein the plunger 102 is disposed opposite the stationary core and fixedly attached to the driving member. Wherein the plunger 102 is configured to move toward the stationary core 108 to drive the driver to move in response to a change in current of the coil exceeding a current threshold, the current threshold being related to a fault current of the coil. In some embodiments, as shown in FIG. 1, the coil 106 at least partially surrounds the stationary core 108. The aspect of the embodiments of the present disclosure is not limited thereto, but may be variously changed. Wherein the coil 106 is connected in series with the protected circuit. When the protected circuit is operating normally, an electromagnetic field is generated when current flows through the coil 106. The coil 106 and the stationary core 108 may form an electromagnet. The electromagnet generates an electromagnetic force on the plunger 102.

In some embodiments, as shown in fig. 1, the drive device further comprises a spring 104. As shown in fig. 1, the spring 104 is coupled between the stationary core 108 and the movable core 102. However, the connection manner of the spring 104 is not limited thereto, but may be variously changed. In some embodiments, as shown in fig. 1, in the normal state, the plunger 102 receives the elastic force (pushing force) of the spring 104 in addition to the electromagnetic force generated by the coil 106. Since the electromagnetic force generated by the coil 106 is lower than the elastic force of the spring 104 in the normal state, the plunger 102 is held at a predetermined initial position.

When the line is overcurrent, i.e., the current I is greater than or equal to the fault current threshold, the electromagnetic field generated by the current in the coil 106 (which forms an electromagnet with the stationary core 108) is strong enough to attract the movable core 102 to move toward the stationary core 108. In some embodiments, the plunger 102 may be a core or a magnet. Similarly, the stationary core 108 may be a core or a magnet. The present disclosure is not limited thereto as long as it can interact with a magnetic field. In some embodiments, the plunger 102 and the ejector 110 (trip ejector) are connected (e.g., riveted) together, so that the plunger 102 moves the ejector 110 to trigger the moving contact of the trip device, e.g., in some embodiments, the protection mechanism of the circuit breaker. The spring 104 used may be a counter spring, i.e. a spring force against the plunger 102. The plunger 102 moves in the direction of the plunger 108, further compressing the spring 104. In some embodiments, the spring 104 functions to determine the threshold of the plunger 102 motion by varying the magnitude of the force. The stiffness of the spring 104 and the magnitude of the initial force value are positively correlated to the ampere-turns of the coil 106, i.e., NI, where N is the number of turns of the coil 106 and I is the current in the coil 106. For example, the greater the spring 104 has a greater force value on the plunger 102, the greater the corresponding fault current value. I.e., a greater current is required in the coil 106 to generate an electromagnetic force to overcome the spring force of the spring 104 against the plunger 102.

In some embodiments, to ensure a certain threshold of motion, the spring 104 requires a high stiffness and therefore a high spring force against the plunger 102. This results in the plunger 102 being prevented from operating in the presence of a fault current. And as the plunger 102 moves toward the plunger 108, the spring 104 is compressed to a greater degree and, therefore, a greater spring force. Thereby causing the moving speed of the plunger 102 to slow down and affecting the speed of the tripping action. The parameters of the spring 104 can be designed appropriately to minimize the influence on the moving speed of the plunger 102 and improve the response speed. In the design of the entire drive, a relatively large effort is required to calculate the spring 104 parameters. It is desirable to further improve the response speed of the drive apparatus.

Further embodiments of the present disclosure are described further below in conjunction with fig. 2 and 3. Fig. 2 shows a schematic diagram of a drive arrangement for a trip device according to another embodiment of the present disclosure; fig. 3 shows a schematic diagram of the driving apparatus for the trip device shown in fig. 2 in a fault state according to an embodiment of the present disclosure. In which the same structures as in figure 1 are not described in detail.

In some embodiments, as shown in fig. 2, the drive device includes a drive member and an electromagnetic actuator, similar to fig. 1. In some embodiments, the electromagnetic actuator includes a stationary core 108, a coil 106, and a movable core 102. Wherein the plunger 102 is disposed opposite the stationary plunger 108 and is fixedly attached to the driver. Wherein the plunger 102 is configured to move toward the stationary core 108 to drive the driver to move in response to a change in current of the coil 106 exceeding a current threshold, the current threshold being related to a fault current of the coil 106. In some embodiments, as shown in fig. 2, the drive device differs from the embodiment shown in fig. 1 mainly in that the drive device 100 further comprises a retaining device. The holding means comprises a permanent magnet 212. The permanent magnet 212 is configured to attract the plunger 102 by a magnetic force to hold the plunger 102 at a predetermined position, and the permanent magnet 212 is fixedly disposed on a side of the plunger 102 away from the stationary core 108 so that the plunger 102 moves against the action of the magnetic force upon occurrence of a fault current. Under normal operating conditions, the plunger 102 is held at the initial position by the attractive force of the permanent magnet 212. The holding device of the embodiments of the present disclosure is not limited to the permanent magnet, but may be variously changed as long as the permanent magnet can be fixed to an initial position in an initial state and the movable core is released in case of a fault current.

In some embodiments, the plunger 102 moves toward the stationary core 108 against the elastic force of the spring 104 when the fault current occurs, and returns the plunger 102 to the predetermined position under the elastic force of the spring 104 when the fault current is removed. Unlike the previous embodiments, in some embodiments, the spring 104 may employ a return spring rather than a counter force spring. The terms "counter spring" and "return spring" as referred to in this disclosure are terms commonly used in the art. The counter force spring generally has a high stiffness and normally exerts a high spring force on the object during operation. In contrast to the counter spring, the return spring generally has a lower stiffness. The above terms are used herein for ease of description to distinguish between two functions with distinct springs.

In some of the above embodiments using a reaction spring, the reaction spring has two functions, one is to provide a sufficient force value corresponding to the trip threshold (action threshold), and the other is to reset the plunger 102. One disadvantage of this approach is: since the reaction spring has a large elastic force on the movable core 102, the moving speed of the movable core 102 is affected to some extent in the case of a fault current.

In some embodiments, during normal operation, the coil 106 is directly connected in series in the main loop, so that current is always present. When the current I is small, the electromagnetic force in the coil 106 is insufficient to cause the plunger 102 to move. Only when the current reaches a certain threshold, for example, when a fault current occurs in the line, the electromagnetic force of the electromagnetic field generated in the coil 106 on the movable core 102 exceeds the attraction force of the permanent magnet 212 on the movable core 102, and the movable core 102 moves toward the stationary core 108 free from the attraction force of the permanent magnet 212. The attraction of the permanent magnet 212 to the plunger 102 decreases exponentially as the distance from the permanent magnet 212 increases. In addition, the spring 104 resistance experienced by the plunger 102 is significantly reduced because the return spring replaces the conventional reaction spring. Thus, the speed of movement of the plunger 102 is greatly increased compared to conventional designs. When fault protection is complete, i.e. the circuit breaker is open, the current in the coil 106 disappears. After the fault current is eliminated, the plunger 102 returns to a predetermined position by the elastic force of the spring 104. That is, in some embodiments, the spring 104 is used only to reset the plunger 102 and is not used to apply a spring force to the plunger 102 to hold it in a predetermined position. The function of holding the plunger 102 in a predetermined position is accomplished by the permanent magnet 212.

In some embodiments of the present disclosure, by combining the permanent magnet 212 with the spring 104, the disadvantages of the solution using only a counter force spring can be overcome. The spring 104 is equivalent to retaining only the return function of the reaction spring, and removing the function of providing a sufficient force value corresponding to the trip threshold. The force required for the reset function is small, much less than the force that provides the trip threshold. In other words, in some embodiments, the two functions of the counter force spring are split into two parts: the permanent magnet 212 provides the trip threshold function and the return spring provides the plunger 102 return function. In this way, by replacing the reaction spring with the return spring, the influence of the reaction spring on the moving speed of the movable iron core 102 is avoided, and the response speed is further improved.

In some embodiments, the spring 104 is configured to: in a normal state, i.e., a state in which the movable core 102 is not moved toward the stationary core 108, the spring 104 is in a natural state or substantially in a natural state. That is, the plunger 102 may be attracted at a predetermined position only by the magnetic force of the permanent magnet 212 without occurrence of a fault current. Without the spring 104 applying a spring force to the plunger 102. Thus, the spring 104 may be configured to be in a natural state. Of course, if the spring 104 exerts a certain elastic force on the plunger 102 (this state may be referred to as a substantially natural state or a substantially natural state) according to actual needs, the blocking force of the spring 104 on the plunger 102 may be much smaller than the resistance force exerted by the reaction spring in the case of a fault current, as long as the elastic force is smaller than the elastic force of the reaction spring in this state. Therefore, the moving speed of the plunger 102 can be increased.

In some embodiments, the permanent magnet 212 and the plunger 102 are disposed with a gap therebetween. I.e. a gap is provided between the magnet and the plunger 102. The gap may be air between the gaps.

In the above-described embodiment, the attractive force between the permanent magnet 212 and the plunger 102 can be adjusted, so that the flexibility of design can be increased. By varying the magnetic gap 6 or the flux of the permanent magnets 2127, different attractive forces are provided to the plunger 102 to accommodate different current levels or threshold trip curve requirements.

In some embodiments, the size of the gap is adjustable. In the above embodiment, the attractive force between the permanent magnet 212 and the plunger 102 can be conveniently adjusted according to actual needs, thereby increasing the flexibility of design.

In some embodiments, the electromagnetic actuator may also include a magnetic medium 214 disposed in the gap. By providing a magnetic medium 214, the magnetic field distribution can be changed, thereby more conveniently and quickly adjusting the magnetic force between the permanent magnet 212 and the plunger 102.

In some embodiments, the electromagnetic actuator further comprises a stop that abuts the plunger 102 to prevent the plunger 102 from moving toward the permanent magnet 212. In this way, by providing the actuator, the gap between the permanent magnet 212 and the plunger 102 can be set as needed so that a predetermined magnetic force is maintained therebetween.

In some embodiments, the electromagnetic actuator comprises a linear electromagnetic actuator, wherein the plunger 102 is configured to move linearly to drive the driver in linear motion. In this way, a quick response of the trip device can be achieved with a simple structure.

In some embodiments, the electromagnetic actuator comprises a rotary electromagnetic actuator, wherein the plunger 102 is configured to move rotationally to drive rotation of the driver. In this way, by providing a rotary electromagnetic actuator, it is possible to effect triggering of a trip requiring rotational triggering as desired.

In some embodiments, the permanent magnet 212 controls the trip threshold, and when the current in the coil 106 reaches a desired level, the plunger 102 trips off the permanent magnet 212. Since the attraction force of the magnet is reduced obviously after the movable iron core 102 is far away from the permanent magnet 212, the movable iron core is not obstructed, and therefore, the faster tripping speed is obtained. The reset spring force value is very little, only provides the dropout and accomplishes the back and move core reset function, consequently is less than reaction spring's power value far away to moving the hindrance effect of core.

In some embodiments of the present disclosure, a permanent magnet 212 may be used to provide a magnetic force that holds the plunger 102 in a predetermined position. The return spring can be used to provide the elastic force for returning the plunger 102, which can significantly improve the response speed of the driving device in case of fault current. And can reduce the number of designs for the spring 104, e.g., a reaction spring. The requirements on the initial force value and the rigidity of the counter-force spring are obviously reduced, so that the industrial production difficulty is reduced.

The operation of the drive device of some embodiments of the present disclosure is described further below. In the initial state, the plunger 102 is attracted by the permanent magnet 212. Under the condition that the fault current threshold value is exceeded, the movable iron core 102 drives the push rod to move rightwards, and tripping is achieved. The attraction force of the permanent magnet 212 becomes smaller and smaller in the process. In addition, since the spring 104 is a return spring, the stiffness is low and the obstruction to the plunger 102 is small. After tripping, no current flows in the coil 106, and no attraction force exists between the static iron core 108 and the movable iron core 102. At this time, the permanent magnet 212 is relatively far from the plunger 102, the attraction force is small, and the leftward movement of the plunger 102 is mainly realized by the elastic force of the spring 104. For example, the spring force of the spring 104 can push the plunger 102 into proximity with the permanent magnet 212, and the attraction of the permanent magnet 212 can pull it back to its original position in equilibrium. The attraction of the permanent magnet 212 causes the moving core to stop at the initial position. The spring 104 is configured such that its elastic force is much smaller than the attractive force of the permanent magnet first plunger 102.

The right end 116 of the push rod may be coupled to a trigger mechanism of the circuit breaker in some embodiments such that the trigger mechanism causes the movable contact to open in response to the push of the push rod.

In addition, it is to be noted that the operating state of the driving device is not limited to the horizontal direction, but can be applied to various directions. When applied to a non-horizontal direction, although the weight of the movable core 102 theoretically has a certain effect on the movement thereof, in practice, the weight has a much smaller effect than other components during the operation of the movable core 102 and can be ignored.

It should be understood that the spirit and principles of the present disclosure are illustrated in the described embodiments by examples of actuators comprising exemplary structures, shapes, however the scope of the present disclosure is not limited thereto and may include actuators having other structures, shapes.

In the above embodiments, the structure of the driving device of the present disclosure is described with respect to the drawings. The structure of the actuator of the present disclosure is not limited to that shown in the drawings, but may have various other forms.

In some embodiments of the present disclosure, a permanent magnet is disposed behind a movable iron core of a conventional driving device (trip), and a magnetic gap is controlled between the permanent magnet and the movable iron core. The permanent magnet attracts the movable iron core in a normal state, so that a counter force spring is omitted. The action of the movable iron core is accelerated by combining the permanent magnet and the spring, and the response speed is improved.

The driving device is shown in a specific structure in the above embodiment, but the structure of the driving device is not limited to the above-shown structure, and various modifications are possible. For example, the position of the push rod, the connection mode; the shapes and sizes of the permanent magnet 212, the movable core 102 and the stationary core 108 can be changed according to the design requirements. For example, they may be cylindrical, prismatic, and so on.

Some embodiments of the disclosure can achieve the following technical advantages: the technical scheme of the utility model can reduce the resistance that the removal of movable iron core during fault current received to this drive arrangement's response speed has been improved. According to the scheme of the embodiment of the disclosure, through structural improvement and optimization of the driving device, the response speed of the driving device during overcurrent is obviously improved through a simple structure, the design of a large number of reaction springs is reduced, and the difficulty of industrial production is reduced.

In some embodiments of the present disclosure, there is also provided a circuit breaker including the driving apparatus described above. The circuit breaker has improved response speed compared to conventional designs.

The above description has been presented for purposes of illustration and description of the various embodiments of the disclosure, and is not intended to be exhaustive or to limit the disclosure to the precise embodiments disclosed. Although claims have been formulated in this application to particular combinations of features, it should be understood that the scope of the disclosure also includes any novel feature or any novel combination of features disclosed herein either explicitly or implicitly or any generalisation thereof, whether or not it relates to the same aspect as presently claimed in any claim. The applicants hereby give notice that new claims may be formulated to such features and/or combinations of such features during the prosecution of the present application or of any further application derived therefrom.

The terminology used herein is chosen in order to best explain the principles of the embodiments, the practical application, or improvements made to the technology in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein. Various modifications and variations of this disclosure will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present disclosure should be included in the protection scope of the present disclosure.

Claims (10)

1. A drive for a trip device, comprising:

the driving piece is suitable for driving the movable contact of the tripping device to move from a closing position to a tripping position; and

an electromagnetic actuator configured to drive the driver and including:

a stationary core (108);

a coil (106);

a plunger (102) disposed opposite the stationary core (108) and fixedly attached to the driver, wherein the plunger (102) is configured to move toward the stationary core (108) to drive the driver to move in response to a change in current of the coil (106) exceeding a current threshold, the current threshold being related to a fault current of the coil (106),

wherein the electromagnetic actuator further comprises a holding device, wherein the holding device is configured to hold the plunger (102) at a predetermined position when the change in current of the coil (106) does not exceed the current threshold.

2. The drive device for the trip device according to claim 1, characterized in that the holding device comprises a permanent magnet (212), the permanent magnet (212) is configured to attract the plunger (102) by a magnetic force to hold the plunger (102) at a predetermined position, and the permanent magnet (212) is fixedly disposed at a side of the plunger (102) away from the stationary core (108) so that the plunger (102) moves against the magnetic force at the time of the fault current.

3. The driving apparatus for the trip apparatus according to claim 1, wherein the electromagnetic actuator further comprises a spring (204), wherein the plunger (102) moves toward the stationary core (108) against an elastic force of the spring (204) when the fault current occurs, and the plunger (102) is returned to the predetermined position under the elastic force of the spring (204) when the fault current is removed.

4. The drive device for a trip unit according to claim 3, wherein the spring (204) is configured to: the spring (204) is in a natural state or substantially in a natural state in a state where the movable iron core (102) is not moved toward the stationary iron core (108).

5. The drive for a trip device according to claim 2, wherein said permanent magnet (212) and said plunger (102) are arranged with a gap therebetween.

6. The drive for a trip unit according to claim 5, wherein the size of said gap is adjustable.

7. The drive device for the trip unit according to claim 5 or 6, characterized in that the electromagnetic actuator further comprises a stop abutting the plunger (102) to prevent the plunger (102) from moving towards the permanent magnet (212).

8. The drive for a trip device according to any of claims 1-6, wherein the electromagnetic actuator comprises a linear electromagnetic actuator, wherein the plunger (102) is configured to move linearly to drive the drive member in a linear motion.

9. Drive arrangement for a trip device according to any of claims 1-6, characterized in that the electromagnetic actuator comprises a rotary electromagnetic actuator, wherein the plunger (102) is configured for rotational movement to drive the driver in rotation.

10. A circuit breaker, characterized in that it comprises a drive for a trip device according to any one of claims 1 to 9.

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