Short-circuiting device and converter

Abstract

The invention relates to an electrical short-circuiting device (10) having a fixed and a movable contact piece (12, 14), the contact pieces (12, 14) being distanced from one another in a basic position and being electrically conductively connected to one another in a short-circuit position, having a drive (16) for transferring the movable contact piece (14) from the basic position into the short-circuit position, and having a trigger device (18) for triggering the drive (16). According to the invention, the trigger device (18) comprises an electrically driven actuator (24) for the triggering. The invention further relates to a converter which comprises at least one short-circuiting device (10) of this kind. The invention further relates to a corresponding method for short-circuiting contact pieces (12, 14).

Description

[0001] The invention relates to an electrical short-circuiting device with a fixed and a movable contact piece, wherein the contact pieces are spaced apart from each other in a home position and are electrically connected to each other in a short-circuit position, a drive for moving the movable contact piece from the home position to the short-circuit position and a release device for releasing the drive.

[0002] The invention further relates to a converter, in particular a multilevel converter, which has at least one such electrical short-circuiting device.

[0003] Multilevel converters, consisting of power modules connected in series, are used particularly in high-voltage direct current (HVDC) transmission for energy distribution and transmission. If a power module fails, it must be bypassed as quickly as possible, otherwise the entire system may fail. The power module is bypassed using a short-circuiting device.

[0004] Short-circuiting devices are known in the prior art. Document DE 1 094 864 B describes a short-circuiting device with several symmetrically or star-shaped arranged fixed contacts and a movable contact connected to an energy storage device for bridging arc faults in medium- or high-voltage electrical systems. To trigger the short-circuiting device, a strike is provided on a pin coupled to the armature of a holding magnet, the armature being under the action of a breakaway spring. The short-circuiting device is then triggered when the holding magnet is de-energized.

[0005] A short-circuiting device with a similar release mechanism is also described in DE 10 2007 018 344 A1. The release mechanism comprises a permanent magnet, a soft magnetic yoke connected to the permanent magnet, an armature connected to a tensioned contact bolt, and an electric coil. By appropriately energizing the electric coil, the force of the permanent magnet weakens, causing the armature to detach from the soft magnetic yoke or the permanent magnet.

[0006] A challenge with such triggering devices is that they may be susceptible to interfering magnetic fields, which can lead to unintentional triggering.

[0007] With a view to bridging as quickly as possible, pyrotechnically operated short-circuiting devices are usually used, as disclosed for example in DE 10 2015 203 645 A1.

[0008] DE 23 56 516 A1 and DE 198 08 083 C1 disclose further examples of electrical short-circuiting devices.

[0009] Due to the pyrotechnic drive, pyrotechnically operated short-circuiting devices present the challenge that their use must comply with nationally differing import regulations, explosives laws and other regulatory requirements.

[0010] The object of the invention is to provide an electrical short-circuiting device and a converter that allow for the fastest and safest possible short-circuiting. In particular, the short-circuiting device should not require a pyrotechnic drive, and the tripping mechanism of the short-circuiting device should also function without a permanent magnet.

[0011] The problem is solved by the features of independent claim 1.

[0012] Advantageous embodiments are specified in the dependent claims.

[0013] According to the invention, an electrical short-circuiting device is provided with a fixed and a movable contact element, wherein the contact elements are spaced apart from each other in a home position and are electrically connected to each other in a short-circuited position, with a drive for moving the movable contact element from the home position to the short-circuited position, and with a release device for triggering the drive. It is provided that the release device comprises an electrically driven actuator.

[0014] In the electrical short-circuiting device according to the invention, the actuator of the release mechanism is electrically driven. This means that an electric drive is used to generate the mechanical movement of the actuator. Such an actuator exhibits very fast release times. Since no permanent magnet is used in the release unit, the short-circuiting device is also not susceptible to magnetic interference fields, thus enabling reliable release. With the electrical short-circuiting device according to the invention, closing times t of t < 2 ms can be achieved.

[0015] An electrical short-circuiting device constructed in this way is particularly suitable for use in medium and high voltage electrical systems, for example in a converter.

[0016] According to the invention, the actuator comprises a stationary stator and a rotor that is linearly movable along an axis of motion. The stator includes a first coil, and the rotor includes a second coil for interaction with the first coil. The stator and the rotor are arranged along the axis of motion, the two coils are aligned parallel to each other, and both coils are air-core coils that can be actively energized, at least with respect to their interaction. To ensure that the electrical short-circuiting device has short closing times, it is naturally also advantageous if the triggering mechanism is particularly fast. The described actuator is especially well suited for this purpose. The two coils can be energized in such a way that they repel each other. This energizing process generates a magnetic field in each coil.The Lorentz force, generated by the interaction between the magnetic field of one coil and the current in the other, causes the coils to repel each other. Since these are air-core coils, they lack a soft magnetic core and have relatively low inductances compared to coils with a soft magnetic core. The force of such an actuator is effective even when the current in the coil changes slowly, and thus throughout the entire time the coils are energized. By eliminating the soft magnetic material, the actuator's inductance decreases, allowing the current to rise more rapidly. A rapid current rise leads to a rapid force increase. Therefore, this actuator is particularly well-suited for enabling the quick-release mechanism to be triggered quickly.

[0017] According to a further preferred embodiment of the invention, the release device comprises a locking mechanism for locking the drive, wherein the drive can be released by releasing the locking mechanism by means of the electrically driven actuator. The use of such a release device enables a particularly fast movement of the movable contact piece.

[0018] Preferably, the actuator includes a plunger for releasing the locking mechanism. This plunger releases the locking mechanism (latch) upon activation. The plunger transmits the force of the actuator and releases the locking mechanism of the short-circuiting device. Preferably, the plunger is guided in its movement, ensuring controlled movement. The locking mechanism preferably includes a pawl. This pawl is the actual locking element of the locking mechanism. Most preferably, the plunger acts directly on the pawl of the locking mechanism.

[0019] According to a further preferred embodiment of the invention, the short-circuiting device comprises an electrically insulating sheath that encloses the stationary and the movable contact pieces. In the event of a short circuit or an arc occurring between the contact pieces, the insulating housing can significantly increase safety. For example, it can prevent the arc from propagating through the insulating housing. Preferably, the movable contact piece tapers conically towards the stationary contact piece and, upon reaching the short-circuit position, moves into a shape-complementary section of the stationary contact piece. This ensures reliable electrical short-circuiting.

[0020] With a view to reuse after a short circuit, the short-circuiting device preferably includes a return rod to move the movable contact from the short-circuited position to its home position and to (re)charge an energy storage device to power the drive. Pulling the return rod returns the movable contact to its home position. Simultaneously, the energy storage device is recharged. If a spring assembly is used as the energy source, pulling the return rod deflects at least one spring from its rest position and, for example, returns it to its pre-tensioned state.

[0021] The converter according to the invention is provided to have at least one of the aforementioned short-circuiting devices. In particular, the converter is a multilevel converter. Regarding the advantages of such a converter, reference is made to the short-circuiting device described above.

[0022] Exemplary embodiments of the invention are shown schematically in drawings and subsequently described in more detail. The drawings show... Fig. 1 is a schematic representation of an electrical short-circuiting device according to a preferred embodiment of the invention, Fig. 2 is a sectional view through the electrical short-circuiting device according to a specific preferred embodiment, and Fig. 3 is a sectional view through the actuator of the electrical short-circuiting device according to the specific preferred embodiment of the invention.

[0023] The Figure 1Figure 1 shows a schematic representation of an electrical short-circuiting device 10 according to a preferred embodiment of the invention. The short-circuiting device 10 is a short-circuiting switch comprising a fixed contact 12 and a movable contact 14. In a home position (position I shown on the left), the two contacts 12 and 14 are spaced apart. Furthermore, the short-circuiting device 10 has a drive 16 for moving, more precisely, for shifting, the movable contact 14 from its home position to a short-circuiting position (position II shown on the right), in which the movable contact 14 is electrically connected to the fixed contact 12. To trigger the drive 16, the short-circuiting device 10 has an electrically triggerable release mechanism 18. The release mechanism 18, in turn, comprises a locking mechanism 20 with a pawl 22 and an electrically driven actuator 24.

[0024] The processes involved in closing the electrical short-circuiting device 10 are as follows: The electrically driven actuator 24 actuates the locking pawl 22 of the locking mechanism 20, which triggers the drive 16. The drive 16 moves the movable contact piece 14 from its home position (position I) to the short-circuit position (position II), in which the movable contact piece 14 is electrically connected to the stationary contact piece 12.

[0025] The Figure 2Figure 1 shows a sectional view through the electrical short-circuiting device 10 according to a specific embodiment. It is particularly evident that the drive 16 has a mechanical energy storage device 26 for its energy supply, which in the example shown is designed as a spring arrangement 28, more precisely as a stack of disc springs. The corresponding disc springs are stacked alternately on top of each other. The stack thus formed can also be described as a series connection of disc springs. The movable contact piece 14 is in the home position (position I from). Fig. 1), which means that the disc springs are in a pre-tensioned state. The movable contact piece 14 is connected to a return rod 30. The return rod 30 runs centrally through the spring assembly 28 and is operatively connected to the locking mechanism 20. The pre-tension of the spring assembly 28 is connected to the locking mechanism 20 via the return rod 30, which maintains the pre-tension in the initial position. For this purpose, the return rod 30 is connected to an intermediate element 32, which is supported on one side of the spring assembly 28 and holds it in the pre-tensioned state, i.e., compresses it. After the short-circuiting device 10 has been triggered, the movable contact piece 14 is in the short-circuited position (that of position II from Fig. 1(corresponds) and the spring assembly 28 is no longer in the pre-tensioned state or in a less pre-tensioned state (not shown). By pulling on the return rod 30, the movable contact piece 14 can be returned from the short-circuited position to the (in Fig. 2 The basic position shown) is transferred and the spring arrangement 28 is put into the pre-tensioned state.

[0026] The electrically driven actuator 24 has a plunger 34 which acts on the locking mechanism 20 when the short-circuiting device 10 is triggered. The plunger 34 acts on the pawl 22 of the locking mechanism 20. In the pre-tensioned state of the spring assembly 28, the pawl 22 prevents the spring assembly 28 from leaving its pre-tensioned state. Only when the plunger 34 presses on the pawl 22 does the locking mechanism 20 release and free the spring assembly 28. The actuator 24, the locking mechanism 20, the return rod 30, the spring assembly 28, as well as the movable contact piece 14 and the fixed contact piece 12 are all located on one axis, namely a movement axis 36 of the plunger 34 of the actuator 24, which also coincides with the movement axis of the movable contact piece 14 and the return rod 30.

[0027] The spring assembly 28 is enclosed in a housing 38, which also integrates the release mechanism 18. At the upper end of the housing 38 is a contacting element 40, which is attached to the housing 38 by means of screws 42. The contacting element 40 has a central opening in which the movable contact piece 14 is located. In its home position, the movable contact piece 14 forms a positive-locking connection with the contacting element 40. The movable contact piece 14 tapers conically towards the stationary contact piece 12, so that when the short-circuit position is reached, it can retract into a form-complementary section of the stationary contact piece 12. Furthermore, the movable contact piece 12 has a contact extension 44 that extends to approximately the intermediate element 32 of the retraction rod 30.In the short-circuited position, this contact extension 44 conductively connects the movable contact 14 to the contacting element 40. The stationary contact 12 is attached to an end piece 48 by means of a screw device 46. The end piece 48 forms the upper end of the short-circuiting device 10. The stationary contact 12 is connected to an electrically insulating sheath 50 via the end piece 48. The sheath 50 forms the lateral end of the short-circuiting device 10. The stationary contact 12, the movable contact 14, as well as the release mechanism 18 and the actuator 16 are all enclosed by the electrically insulating sheath 50. The housing 38 is positively enclosed by the sheath 50 in the area of ​​the release mechanism. At its lower end, the housing 38 projects beyond the sheath 50 and extends radially outwards.A ring element 52, which encloses the outer casing 50, is attached to this extension of the housing 38 with screws 42. A housing base 54, to which the actuator 24 is attached, is integrated into the lower part of the housing 38. Although the individual components of the actuator 24 are already shown here in . Figure 2 They should only be recognizable in connection with the Figure 3 be discussed.

[0028] The Figure 3Figure 1 shows a sectional view of the actuator 24, which is part of the release mechanism 18. The actuator 24 has a stator 56 and a rotor 58. The rotor 58 is connected to the plunger 34, which extends through a stop element 60. The stop element 60 is connected to the stator 56 via connecting elements 62. The stator 56 consists of a stator body 64 for receiving a first coil 68. The rotor 58 also consists of a rotor body 70 and a second coil 72. The rotor body 70 has two sections 74 and 76. The first section 74 serves to receive the second coil 72, and the second section 76 serves to stiffen the first section 74. The coils 68 and 72 are designed as flat coils, with two coil stacks arranged one above the other. On the side of the runner 58 opposite the pressure plunger 34, it has a runner extension 78 with which it engages in a recess of the stator 56.The runner 58 is guided in its movement via the pressure plunger 34 and also via the runner process 78.

[0029] When the short-circuiting device 10 is activated, the following function results: The two coils 68, 72 are to be considered air coils, at least with regard to their interaction with each other. The effect of the actuator 24 is therefore based solely on the Lorentz force, which is generated reciprocally by the interaction between the coil magnetic field of one coil 68, 72 and the current in the other coil 68, 72, and vice versa.

[0030] To move the plunger 34, the coils 68 and 72 are simultaneously energized in such a way that they repel each other. Since the stator 56 with the first coil 68 is stationary relative to the actuator 24, the rotor 58 with the second coil 72 is moved along the axis of movement 36 in the direction of the stop element 60 (upwards in the figure). The plunger 34, which serves as the actuating element, also moves in this direction with the rotor 58.

Claims

1. Electrical short-circuit device (10) having - a fixed contact piece and a movable contact piece (12, 14), the fixed and movable contact pieces (12, 14) being spaced apart from one another in a basic position and being electrically conductively connected to one another in a short-circuit position, - a drive (16) for transferring the movable contact piece (14) from the basic position to the short-circuit position, and - a trigger device (18) for triggering the drive (16), wherein the trigger device (18), for the purpose of triggering, comprises an electrically driven actuator (24), characterized in that the actuator (24) comprises a fixed stator (56) and a rotor (58) that can be moved linearly along a movement axis (36), wherein the stator (56) comprises a first coil (68), the rotor (58) comprises a second coil (72) for interaction with the first coil (68), the stator (56) and the rotor (58) are arranged along the movement axis (36), and both coils (68, 72) are air-core coils capable of being actively energized at least with respect to the interaction thereof with one another, wherein the action of the actuator (24) is based solely on Lorentz force, which is produced in alternation by the interaction between the coil magnetic field of one coil of the two coils (68, 72) and a current in the other coil of the two coils (68, 72) and vice versa.

2. Short-circuit device (10) according to Claim 1, characterized in that the trigger device (18) comprises a locking mechanism (20) for locking the drive (16), wherein the drive (16) can be triggered when the electrically driven actuator (24) is used to release the locking mechanism (20).

3. Short-circuit device (10) according to Claim 2, characterized in that the actuator (24) comprises a plunger (32) for releasing the locking mechanism (20).

4. Short-circuit device (10) according to any one of Claims 1 to 3, characterized by an electrically insulating jacket (50) that encases the fixed and movable contact pieces (12, 14).

5. Short-circuit device (10) according to any one of Claims 1 to 4, wherein the movable contact piece (14) tapers conically in a direction of the fixed contact piece (12) and, when the short-circuit position is reached, enters a complementarily shaped section of the fixed contact piece (12).

6. Short-circuit device (10) according to any one of Claims 1 to 5, characterized by a retraction rod (30) for transferring the movable contact piece (14) from the short-circuit position to the basic position while energy is supplied to a mechanical energy store (26) at the same time in order to supply energy to the drive (16).

7. Converter, in particular multilevel converter, having a plurality of power modules, characterized by at least one short-circuit device (10) according to any one of Claims 1 to 6.

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