An electromagnetic buffer circuit for fast vacuum switch

Abstract

The present invention discloses an electromagnetic snubber circuit for a fast vacuum switch, wherein the electromagnetic snubber circuit includes: a capacitor, a turn-off power electronic device, a first diode, a second diode, a coil, and a resistor; the collector of the turn-off power electronic device is connected to the positive electrode of the capacitor, the emitter of the turn-off power electronic device is connected to the coil input terminal, and the base of the turn-off power electronic device receives a switch control signal; the coil output terminal is connected to the negative electrode of the capacitor; the first diode is connected in parallel with the capacitor, the positive electrode of the first diode is connected to the negative electrode of the capacitor, and the negative electrode of the first diode is connected to the positive electrode of the capacitor; the positive electrode of the second diode is connected to the coil output terminal, and the negative electrode of the second diode is connected in series with the resistor and then connected to the coil input terminal; the switch control signal is used to adjust the start time and duration of the electromagnetic snubber. By controlling the conduction and shutdown of the turn-off power electronic device, the main discharge circuit of the electromagnetic snubber circuit is turned on and the primary or secondary freewheeling circuit is switched, thereby controlling the intervention time and duration of the snubber.

Description

Technical Field

[0001] The present invention relates to the technical field of power switch equipment, and in particular to an electromagnetic buffer circuit of a fast vacuum switch. Background Art

[0002] Fast vacuum switches operate extremely quickly. If an effective buffer is not added, the high speed at the end of the switch operation will cause severe switch bounce, shorten its service life, and even cause the switch to fail to open or close. Therefore, the design of a reasonable buffer device is of great significance to the development of fast vacuum switches.

[0003] The electromagnetic snubber for fast-acting vacuum switches is a buffering solution based on a bidirectional electromagnetic repulsion mechanism. This works by discharging a coil in the snubber circuit to generate a reverse electromagnetic force, decelerating the switch and achieving a buffering effect. Since the snubber design for fast-acting vacuum switches must match the switch's drive characteristics, and existing electromagnetic snubber solutions cannot freely adjust the snubber strength, changes in the fast-acting vacuum switch's motion characteristics may cause a mismatch between the snubber design and the switch's motion characteristics, resulting in a failure to properly function. Summary of the Invention

[0004] An embodiment of the present invention aims to provide an electromagnetic snubber circuit for a fast vacuum switch. By controlling the on and off of a switchable power electronic device, the main discharge circuit of the electromagnetic snubber circuit can be turned on and the primary freewheeling circuit and the secondary freewheeling circuit can be switched, thereby controlling the timing of buffering intervention and the duration of buffering.

[0005] To solve the above technical problems, a first aspect of an embodiment of the present invention provides an electromagnetic snubber circuit, comprising: a capacitor, a turn-off power electronic device, a first diode, a second diode, a coil, and a resistor;

[0006] The collector of the switchable power electronic device is connected to the positive electrode of the capacitor, the emitter is connected to the input terminal of the coil, and the base receives a switch control signal;

[0007] The coil outlet is connected to the negative electrode of the capacitor;

[0008] The first diode is connected in parallel with the capacitor, with its anode connected to the cathode of the capacitor and its cathode connected to the anode of the capacitor;

[0009] The anode of the second diode is connected to the coil output terminal, and the cathode of the second diode is connected in series with the resistor and then connected to the coil input terminal;

[0010] The capacitor, the turn-off power electronic device and the coil constitute a main discharge circuit, the first diode, the turn-off power electronic device and the coil constitute a primary freewheeling circuit, and the second diode, the coil and the resistor constitute a secondary freewheeling circuit;

[0011] The switch control signal is used to adjust the start time and duration of the electromagnetic buffer.

[0012] Furthermore, the switch control signal includes: an on control signal and an off control signal;

[0013] The sending time of the conduction control signal corresponds to the start time of the electromagnetic buffer;

[0014] The interval between the on-control signal and the off-control signal corresponds to the duration of the current in the coil and the duration of the electromagnetic buffer.

[0015] Furthermore, the capacitor is in a pre-charge state before receiving the switch control signal.

[0016] Furthermore, the switchable power electronic device is a fully controlled power electronic device.

[0017] Furthermore, the resistance value of the resistor is greater than a first preset multiple of the resistance value of the coil.

[0018] Furthermore, the time constant of the primary freewheeling loop is greater than a second preset multiple of the time constant of the secondary freewheeling loop.

[0019] Furthermore, after the switchable power electronic device is turned on and before the capacitor voltage drops to 0, the main discharge circuit of the electromagnetic buffer circuit is an RLC discharge circuit;

[0020] When the capacitor voltage drops to 0 and before the turn-off power electronic device is turned off, the primary freewheeling circuit of the electromagnetic buffer circuit is an RL discharge circuit.

[0021] Accordingly, a second aspect of an embodiment of the present invention provides an electromagnetic buffer circuit control method for controlling the electromagnetic buffer circuit, comprising the following steps:

[0022] Receive a conduction control signal to control the conduction of a power electronic device that can be turned off;

[0023] Control the capacitor in the main discharge circuit to discharge to the coil;

[0024] When the voltage value of the capacitor drops to 0, the first diode in the primary freewheeling circuit, the turn-off power electronic device and the coil are turned on, and the coil current begins to decay;

[0025] When a shutdown control signal is received, the second diode, the resistor and the coil in the secondary freewheeling loop are turned on, the coil current decays to 0, and the electromagnetic buffering process ends.

[0026] Furthermore, the electromagnetic buffer circuit control method further includes:

[0027] By adjusting the sending time of the conduction control signal, the start time of the electromagnetic buffer is correspondingly adjusted;

[0028] By adjusting the interval between the on-control signal and the off-control signal, the duration of the current in the coil and the duration of the electromagnetic buffer are adjusted accordingly.

[0029] Accordingly, a third aspect of an embodiment of the present invention provides a fast vacuum switch, comprising the above-mentioned electromagnetic buffer circuit,

[0030] It also includes: a vacuum interrupter, an insulating pull rod, an electromagnetic repulsion mechanism, a holding device and a buffer device;

[0031] The vacuum interrupter, the insulating pull rod, the holding device, the electromagnetic repulsion mechanism and the buffer device are connected in sequence;

[0032] When the fast vacuum switch performs a closing action, the coil of the electromagnetic buffer circuit serves as the opening coil of the electromagnetic repulsion mechanism, and the capacitor in the electromagnetic buffer circuit serves as the opening capacitor of the electromagnetic repulsion mechanism. The buffering effect is achieved by the opening coil of the electromagnetic repulsion mechanism.

[0033] When the fast vacuum switch performs an opening action, the coil of the electromagnetic buffer circuit serves as the closing coil of the electromagnetic repulsion mechanism, and the capacitor in the electromagnetic buffer circuit serves as the closing capacitor of the electromagnetic repulsion mechanism. The buffering effect is achieved by the closing coil of the electromagnetic repulsion mechanism.

[0034] When the fast vacuum switch performs a closing action, the capacitor of the electromagnetic buffer circuit discharges toward the closing coil, and an electromagnetic repulsive force is generated between the repulsion disk of the electromagnetic repulsion mechanism and the closing coil, which pushes the repulsion disk to move and drives the moving contact in the vacuum interrupter to move, thereby achieving the closing action of the fast vacuum switch. After a first preset time, the turnable power electronic device in the electromagnetic buffer circuit connected to the opening coil of the electromagnetic repulsion mechanism is turned on, and the capacitor discharges toward the opening coil and generates an electromagnetic repulsive force in the opposite direction of the closing movement, thereby decelerating the repulsion disk and achieving buffering.

[0035] When the fast vacuum switch performs an opening action, the capacitor discharges to the opening coil, and an electromagnetic repulsive force is generated between the repulsion disk and the opening coil to push the repulsion disk to move and drive the moving contact in the vacuum interrupter to move, thereby realizing the opening action of the fast vacuum switch. After a second preset time, the turnable power electronic device connected to the closing coil is turned on, and the capacitor discharges to the closing coil and generates an electromagnetic repulsive force in the opposite direction of the opening movement, thereby decelerating the repulsion disk and realizing buffering.

[0036] The above technical solutions of the embodiments of the present invention have the following beneficial technical effects:

[0037] 1. By turning off the on / off control signals of the power electronic device, the start time and duration of the electromagnetic snubber circuit can be precisely controlled. This allows the electromagnetic snubber circuit to intervene at a specific moment as needed and provide buffering force for an appropriate duration, thereby protecting the fast-acting vacuum switch from mechanical shock and electrical stress, extending its service life.

[0038] 2. By reducing the speed of the fast vacuum switch at the end of its movement and reducing the bounce of the switch, it effectively reduces the wear and failure rate of the switch, helps reduce the risk of switch opening and closing failures, improves the reliability of the switch, and ensures the stable operation of the power system;

[0039] 3. The control method of the electromagnetic snubber circuit allows the fast vacuum switch to switch between different operating states to adapt to different snubber requirements, so that the snubber design can match the motion characteristics of the switch, which is conducive to the design optimization of the fast vacuum switch. By controlling the conduction and shutdown of the switchable power electronic device, the intervention time and duration of the snubber can be freely adjusted, making the switch design more flexible and meeting the needs of different application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 1 is a schematic diagram of the structure of an electromagnetic buffer circuit provided by an embodiment of the present invention;

[0041] Figure 2 is a schematic diagram of an electromagnetic buffer circuit provided by an embodiment of the present invention operating in a discharge loop state;

[0042] Figure 3 Schematic diagram of an electromagnetic snubber circuit provided by an embodiment of the present invention operating in a primary freewheeling loop state;

[0043] Figure 4 Schematic diagram of the electromagnetic snubber circuit provided by an embodiment of the present invention operating in a secondary freewheeling loop state. DETAILED DESCRIPTION

[0044] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present invention.

[0045] Please refer to Figure 1 According to a first aspect of an embodiment of the present invention, an electromagnetic buffer circuit is provided, comprising: a capacitor, a turn-off power electronic device, a first diode, a second diode, a coil, and a resistor. The collector of the turn-off power electronic device is connected to the positive electrode of the capacitor, the emitter of the turn-off power electronic device is connected to the coil input terminal, and the base of the turn-off power electronic device receives a switch control signal. The coil output terminal is connected to the negative electrode of the capacitor. The first diode is connected in parallel with the capacitor, with the positive electrode of the first diode connected to the negative electrode of the capacitor and the negative electrode of the second diode connected to the positive electrode of the capacitor. The positive electrode of the second diode is connected to the coil output terminal, and the negative electrode of the second diode is connected in series with the resistor and then connected to the coil input terminal. The capacitor, the turn-off power electronic device, and the coil constitute a primary freewheeling circuit, the first diode, the turn-off power electronic device, and the coil constitute a primary freewheeling circuit, and the second diode, the coil, and the resistor constitute a secondary freewheeling circuit. The switch control signal is used to adjust the start time and duration of the electromagnetic buffer.

[0046] The turn-off power electronic device has a controllable turn-off current. By controlling the on and off of the turn-off power electronic device, the main discharge circuit of the electromagnetic buffer circuit can be turned on and the primary freewheeling circuit and the secondary freewheeling circuit can be switched, thereby controlling the intervention time and duration of the buffer.

[0047] Specifically, the switch control signal includes: an on-control signal and an off-control signal; the sending time of the on-control signal corresponds to the start time of the electromagnetic buffer; the interval between the on-control signal and the off-control signal corresponds to the current duration of the coil and the electromagnetic buffer duration, and the current duration is synchronized with the electromagnetic buffer duration.

[0048] The buffering force generated by the electromagnetic snubber circuit can reduce the terminal speed of the fast vacuum switch and reduce the bounce of the switch, thereby extending the service life of the switch and reducing the failure rate of the switch opening and closing. By controlling the conduction and shutdown of the switchable power electronic device, the electromagnetic snubber circuit can switch between three different working states, and then freely adjust the intervention time and duration of the buffer, making it easy to match the buffer design with the movement characteristics of the switch, which is beneficial to the design of the fast vacuum switch.

[0049] Optionally, the coil can be of the following types: solenoid coil, rectangular coil, Helmholtz coil, or superconducting coil. In the electromagnetic buffer circuit of a fast vacuum switch, a solenoid coil can generate a magnetic field through current, interacting with the moving parts of the switch to generate a buffering force; a rectangular coil can better adapt to the structure and spatial limitations of the switch, facilitating installation and integration; a Helmholtz coil can generate a wide, uniform magnetic field near the midpoint of its common axis, and the current and magnetic field have a good linear relationship. The Helmholtz coil can provide a stable and uniform magnetic field, providing precise buffering control of the switch's movement, and is particularly suitable for applications requiring a high buffering effect; a superconducting coil can provide a strong buffering force, effectively reducing the speed of the switch at the end of its movement and reducing switch bounce.

[0050] like Figure 1 As shown, the resistance R and inductance L in the coil are the equivalent resistance and equivalent inductance of the coil respectively.

[0051] Furthermore, the capacitor is in a precharged state before receiving the switch control signal. The precharged state of the capacitor in the electromagnetic snubber circuit means that the capacitor has been charged to a certain voltage level before the circuit begins operation. In the electromagnetic snubber circuit, the precharged state of the capacitor ensures that when the switchable power electronic device is turned on, the capacitor can quickly release its stored energy, generating electromagnetic force through the coil to achieve a buffering effect on the fast vacuum switch. This precharged state helps reduce the speed of the switch at the end of the movement and reduce switch bounce, thereby extending the service life of the switch and reducing the failure rate of switch opening and closing.

[0052] Furthermore, the turn-off power electronic device is a fully controlled power electronic device, and specifically, an IGBT (insulated gate bipolar transistor) or a GTR (power transistor) can be selected.

[0053] The IGBT is a fully controlled, voltage-driven, composite power semiconductor device that combines the advantages of the high input impedance of a MOSFET with the low on-state voltage drop of a GTR. The IGBT consists of an N-channel MOSFET and a PNP bipolar transistor, and its on and off states are controlled by controlling the gate voltage. Under the action of a positive gate voltage, the MOSFET forms a channel, allowing current to flow between the P+ base and the N- layer, thereby providing base current to the PNP transistor and turning on the IGBT. When the gate voltage is zero or reversed, the channel collapses, cutting off the base current of the PNP transistor and turning off the IGBT. IGBTs are widely used in inverters, electric vehicles, power transmission, and other fields, particularly in power conversion systems with DC voltages of 600V and above.

[0054] A GTR, also known as a giant transistor, is a high-voltage, high-current bipolar junction transistor (BJT). The structure and operating principle of a GTR are similar to those of a conventional bipolar junction transistor, but its most important characteristics are high voltage resistance, high current, and excellent switching characteristics. A GTR is a bipolar device with high current gain and high voltage blocking capability, enabling rapid switching via gate signals. Applications for GTRs include motor control and high-voltage switching power supplies.

[0055] In electromagnetic snubber circuits, both IGBTs and GTRs act as turn-off power electronic devices, controlling the current in the circuit by controlling their on and off states. IGBTs, which combine the advantages of MOSFETs and GTRs, are particularly suitable for applications requiring high input impedance and low on-state voltage drop, while GTRs, due to their high withstand voltage and high current characteristics, have unique advantages in high-voltage and high-current applications. By precisely controlling these devices, precise control of the electromagnetic snubber circuit can be achieved to achieve the desired snubbering effect.

[0056] Furthermore, the resistance of the resistor is greater than a first preset multiple of the coil resistance, and the time constant of the primary freewheeling circuit is greater than a second preset multiple of the time constant of the secondary freewheeling circuit. The resistor R1 is much greater than the coil resistance R, shutting down the turnoff power electronic device. The second diode causes the electromagnetic snubber circuit to switch from the primary freewheeling circuit to the secondary freewheeling circuit. The time constant τ1 of the secondary freewheeling circuit is much smaller than the time constant τ of the primary freewheeling circuit, causing the coil current to rapidly decay to zero, and electromagnetic snubbering ends.

[0057] By precisely designing the resistance values ​​of the resistor and coil, as well as their time constants, the electromagnetic snubber circuit can achieve more precise control over the timing and duration of snubber intervention. This not only helps protect the circuit from damage caused by excessive current, but also allows the circuit state to be quickly switched as needed, achieving effective electromagnetic snubbering.

[0058] Furthermore, after the turn-off power electronic device is turned on and before the capacitor voltage drops to 0, the main discharge circuit of the electromagnetic snubber circuit is an RLC discharge circuit, where R is the equivalent resistance of the coil, L is the equivalent inductance of the coil, and C is the capacitor; and when the capacitor voltage drops to 0 and before the turn-off power electronic device is turned off, the primary freewheeling circuit of the electromagnetic snubber circuit is an RL discharge circuit, where R is the equivalent resistance of the coil and L is the equivalent inductance of the coil.

[0059] An RLC discharge circuit consists of the coil's equivalent resistance R, equivalent inductance L, and capacitor C. In an electromagnetic snubber circuit, when the capacitor is charged to a certain voltage, the power electronics are turned off, and the capacitor begins to discharge through the coil. During the discharge process, the capacitor's voltage gradually decreases, current flowing through the coil generates a magnetic field, and the resistor dissipates electrical energy, converting it into heat. RLC circuits exhibit oscillating discharge characteristics, generating an oscillating current when the capacitor discharges. The interaction between the inductance and capacitance causes electromagnetic oscillations.

[0060] In an RL discharge circuit, when the capacitor voltage drops to zero, the power electronic components can be turned off, and the circuit transforms into an RL discharge circuit consisting only of a resistor and a coil. In this RL discharge circuit, the magnetic field energy in the coil begins to be released through the resistor, and the current gradually decays. Without the capacitor, the circuit no longer exhibits an oscillating discharge characteristic, but instead exhibits a monotonic decay of the current. The discharge process in an RL discharge circuit is typically a non-periodic decay process. The coil's inductance decreases rapidly under the action of the DC voltage, causing the current to decay rapidly.

[0061] Please refer to Figure 2 At the preset moment, the switchable power electronic device is controlled to be turned on, the electromagnetic snubber circuit starts working, and the pre-charged capacitor begins to discharge. The current path in the circuit is from the capacitor through the switchable power electronic device, into the coil, and finally back to the capacitor. Both diodes are reversely cut off. At this time, the working circuit is an RLC discharge circuit. The coil current continues to increase, and the resulting reverse electromagnetic force continues to increase, which begins to play a buffering role for the fast vacuum switch.

[0062] Please refer to Figure 3 After continuous discharge, the capacitor in the electromagnetic snubber circuit gradually drops to 0, and no current flows. At this time, the first diode begins to conduct, forming a primary freewheeling loop with the turn-off power electronic device and the coil. The coil current begins to decay, and the decay rate is related to the time constant τ of the loop. The buffering effect of the electromagnetic snubber circuit on the fast vacuum switch continues, but gradually weakens.

[0063] Please refer to Figure 4 At the appropriate time, the turn-off power electronic device is controlled to be turned off, the working state of the electromagnetic snubber circuit is switched, and the second diode begins to conduct, forming a secondary freewheeling circuit with the resistor and coil in series with the freewheeling circuit. Because the series resistor R1 is much larger than the resistance R of the coil, the time constant τ1 of the secondary freewheeling circuit is much smaller than the time constant τ of the primary freewheeling circuit. The coil current decays rapidly in the secondary freewheeling circuit and drops to 0. The buffering effect of the electromagnetic snubber circuit on the fast vacuum switch weakens rapidly until it disappears.

[0064] By controlling the on and off state of the switchable power electronic device, in conjunction with the first and second diodes, the electromagnetic snubber circuit can be switched between different operating states. The longer the switchable power electronic device is on, the longer the coil current in the snubber circuit persists, and the correspondingly longer the electromagnetic snubber force persists. The electromagnetic snubber circuit of the present invention allows for flexible adjustment of the snubber engagement timing and duration, effectively matching its snubber characteristics with the motion characteristics of a fast-acting vacuum switch.

[0065] Accordingly, a second aspect of an embodiment of the present invention provides an electromagnetic buffer circuit control method for controlling the electromagnetic buffer circuit, comprising the following steps:

[0066] Step S100: receiving a conduction control signal and controlling a power electronic device that can be turned off to conduct.

[0067] By receiving and responding to the conduction control signal of the shut-off power electronic device, the start-up timing of the electromagnetic snubber circuit can be accurately controlled to ensure that the snubber force is provided when needed.

[0068] Step S200: Control the capacitor in the main discharge circuit to discharge toward the coil.

[0069] The capacitor in the main discharge circuit is controlled to discharge into the coil, so that the energy stored in the capacitor can be effectively converted into electromagnetic energy in the coil to drive the load or provide buffering force.

[0070] Step S300: When the voltage value of the capacitor drops to 0, the first diode, the turn-off power electronic device and the coil in the primary freewheeling loop are turned on, and the coil current begins to decay.

[0071] When the capacitor voltage drops to 0, the conduction of the primary freewheeling circuit achieves a smooth transition from capacitor discharge to coil current maintenance, which helps to reduce current shock and electromagnetic interference in the circuit.

[0072] Step S400: receiving a shutdown control signal, the second diode, the resistor and the coil in the secondary freewheeling loop are turned on, the coil current decays to 0, and the electromagnetic buffering process ends.

[0073] By receiving the shutdown control signal of the shutoff power electronic device, the secondary freewheeling circuit is quickly activated, so that the coil current quickly decays to 0, thereby quickly ending the electromagnetic buffering process, reducing energy loss and improving response speed.

[0074] Furthermore, the electromagnetic buffer circuit control method further includes:

[0075] Step S510 , adjusting the start time of the electromagnetic buffering by adjusting the sending time of the conduction control signal.

[0076] Step S520 , by adjusting the interval between the on control signal and the off control signal, the duration of the coil current and the duration of the electromagnetic buffer are correspondingly adjusted.

[0077] The above control method can reduce the speed of the fast vacuum switch at the end of its movement and reduce switch bounce by controlling the electromagnetic snubber circuit, thereby extending the switch's service life and reducing the switch opening and closing failure rate. It enables the electromagnetic snubber circuit to switch between three different operating states (main discharge, primary freewheeling, and secondary freewheeling) to adapt to different snubbering requirements, making it easy to match the snubber design with the switch's movement characteristics. By precisely controlling the on and off of the switchable power electronic devices, the electromagnetic snubber circuit can provide necessary protection at critical moments, avoiding damage to circuit components due to current surges or overvoltage, thereby improving the safety of the entire system.

[0078] Accordingly, a third aspect of an embodiment of the present invention provides a fast vacuum switch, comprising the above-mentioned electromagnetic buffer circuit, and further comprising: a vacuum interrupter, an insulating pull rod, an electromagnetic repulsion mechanism, a retaining device and a buffer device; the vacuum interrupter, the insulating pull rod, the retaining device, the electromagnetic repulsion mechanism and the buffer device are connected in sequence.

[0079] When the fast vacuum switch closes, the coil of the electromagnetic snubber circuit serves as the opening coil of the electromagnetic repulsion mechanism, and the capacitor in the electromagnetic snubber circuit serves as the opening capacitor of the electromagnetic repulsion mechanism. The snubber function is achieved by the opening coil of the electromagnetic repulsion mechanism. When the fast vacuum switch closes, the capacitor in the electromagnetic snubber circuit discharges into the closing coil. This generates an electromagnetic repulsive force between the repulsion disk of the electromagnetic repulsion mechanism and the closing coil, pushing the repulsion disk and the moving contact within the vacuum interrupter, thus closing the fast vacuum switch. After a first preset duration, the turnoff power electronic device in the electromagnetic snubber circuit connected to the opening coil of the electromagnetic repulsion mechanism turns on. The capacitor discharges into the opening coil, generating an electromagnetic repulsive force in the opposite direction of the closing motion, decelerating the repulsion disk and achieving snubbering.

[0080] When the fast vacuum switch performs an opening action, the coil of the electromagnetic snubber circuit serves as the closing coil of the electromagnetic repulsion mechanism, and the capacitor in the electromagnetic snubber circuit serves as the closing capacitor of the electromagnetic repulsion mechanism. The buffering effect is achieved by the closing coil of the electromagnetic repulsion mechanism. When the fast vacuum switch performs an opening action, the capacitor discharges into the opening coil, generating an electromagnetic repulsive force between the repulsion disk and the opening coil, which drives the repulsion disk and the moving contact in the vacuum interrupter, achieving the opening action of the fast vacuum switch. After a second preset time, the power electronic device connected to the closing coil turns on, and the capacitor discharges into the closing coil, generating an electromagnetic repulsive force in the opposite direction of the opening motion, slowing the repulsion disk and achieving buffering.

[0081] The insulating pull rod connects the vacuum interrupter and the electromagnetic repulsion mechanism and acts as an insulator; the holding device provides holding force to stabilize the fast vacuum switch in the open or closed state; the buffer device can reduce the terminal speed of the opening action of the fast vacuum switch and cooperate with the electromagnetic buffer circuit to buffer the opening action of the fast vacuum switch.

[0082] Fast-acting vacuum switches, through the use of electromagnetic snubber circuits, can achieve higher breaking capacities, with rated short-circuit breaking currents up to 100kA and rated voltages up to 242kV. Furthermore, advancements in operating mechanism technology have shortened the breaking time of vacuum circuit breakers. Vacuum circuit breakers employing electromagnetic repulsion mechanisms can reduce the breaking time of short-circuit fault currents to less than half a cycle. Electromagnetic snubber circuits address the buffering challenges inherent in fast-acting vacuum switches. Electromagnetic snubbers are the most suitable buffering method for fast-acting switches, ensuring a "soft landing" of moving parts in fast-acting vacuum switches, resulting in a smooth travel characteristic curve and avoiding the intense mechanical impact associated with high-voltage fast-acting switch operation.

[0083] The embodiment of the present invention aims to protect an electromagnetic buffer circuit and its control method, and a fast vacuum switch, wherein the electromagnetic buffer circuit includes: a capacitor, a turn-off power electronic device, a first diode, a second diode, a coil, and a resistor; the collector of the turn-off power electronic device is connected to the positive electrode of the capacitor, its emitter is connected to the coil input terminal, and its base receives a switch control signal; the coil output terminal is connected to the negative electrode of the capacitor; the first diode is connected in parallel with the capacitor, its positive electrode is connected to the negative electrode of the capacitor, and its negative electrode is connected to the positive electrode of the capacitor; the positive electrode of the second diode is connected to the coil output terminal, and its negative electrode is connected in series with the resistor and then connected to the coil input terminal; the capacitor, the turn-off power electronic device, and the coil constitute a main discharge circuit, the first diode, the turn-off power electronic device, and the coil constitute a primary freewheeling circuit, and the second diode, the coil, and the resistor constitute a secondary freewheeling circuit; the switch control signal is used to adjust the start time and duration of the electromagnetic buffer. The above technical solution has the following effects:

[0084] 1. By turning off the on / off control signals of the power electronic device, the start time and duration of the electromagnetic snubber circuit can be precisely controlled. This allows the electromagnetic snubber circuit to intervene at a specific moment as needed and provide buffering force for an appropriate duration, thereby protecting the fast-acting vacuum switch from mechanical shock and electrical stress, extending its service life.

[0085] 2. By reducing the speed of the fast vacuum switch at the end of its movement and reducing the bounce of the switch, it effectively reduces the wear and failure rate of the switch, helps reduce the risk of switch opening and closing failures, improves the reliability of the switch, and ensures the stable operation of the power system;

[0086] 3. The control method of the electromagnetic snubber circuit allows the fast vacuum switch to switch between different operating states to adapt to different snubber requirements, so that the snubber design can match the motion characteristics of the switch, which is conducive to the design optimization of the fast vacuum switch. By controlling the conduction and shutdown of the switchable power electronic device, the intervention time and duration of the snubber can be freely adjusted, making the switch design more flexible and meeting the needs of different application scenarios.

[0087] It should be understood that the above-described specific embodiments of the present invention are merely illustrative or illustrative of the principles of the present invention and do not constitute limitations of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included within the scope of protection of the present invention. In addition, the appended claims are intended to cover all variations and modifications that fall within the scope and metes and bounds of the appended claims, or equivalents thereof.

Claims

1. An electromagnetic buffer circuit, characterized in that: include: A capacitor, a turn-off power electronic device, a first diode, a second diode, a coil, and a resistor; The collector of the switchable power electronic device is connected to the positive electrode of the capacitor, the emitter is connected to the input terminal of the coil, and the base receives a switch control signal; The coil outlet is connected to the negative electrode of the capacitor; The first diode is connected in parallel with the capacitor, with its anode connected to the cathode of the capacitor and its cathode connected to the anode of the capacitor; The anode of the second diode is connected to the coil output terminal, and the cathode of the second diode is connected in series with the resistor and then connected to the coil input terminal; The capacitor, the turn-off power electronic device and the coil constitute a main discharge circuit, the first diode, the turn-off power electronic device and the coil constitute a primary freewheeling circuit, and the second diode, the coil and the resistor constitute a secondary freewheeling circuit; The switch control signal is used to adjust the start time and duration of the electromagnetic buffer.

2. The electromagnetic snubber circuit according to claim 1, wherein: The switch control signal includes: an on control signal and an off control signal; The sending time of the conduction control signal corresponds to the start time of the electromagnetic buffer; The interval between the on-control signal and the off-control signal corresponds to the duration of the current in the coil and the duration of the electromagnetic buffer.

3. The electromagnetic snubber circuit according to claim 1, wherein: The capacitor is in a pre-charge state before receiving the switch control signal.

4. The electromagnetic snubber circuit according to claim 1, wherein: The switchable power electronic device is a fully controlled power electronic device.

5. The electromagnetic snubber circuit according to claim 1, wherein: The resistance of the resistor is greater than a first preset multiple of the resistance of the coil.

6. The electromagnetic snubber circuit according to claim 1, wherein: The time constant of the primary freewheeling loop is greater than a second preset multiple of the time constant of the secondary freewheeling loop.

7. The electromagnetic buffer circuit according to any one of claims 1 to 6, characterized in that: When the switchable power electronic device is turned on and before the capacitor voltage drops to 0, the main discharge circuit of the electromagnetic buffer circuit is an RLC discharge circuit; When the capacitor voltage drops to 0 and before the turn-off power electronic device is turned off, the primary freewheeling circuit of the electromagnetic buffer circuit is an RL discharge circuit.

8. A method for controlling an electromagnetic buffer circuit, characterized in that: The method for controlling the electromagnetic buffer circuit according to any one of claims 1 to 7 comprises the following steps: Receive a conduction control signal to control the conduction of a power electronic device that can be turned off; Control the capacitor in the main discharge circuit to discharge to the coil; When the voltage value of the capacitor drops to 0, the first diode in the primary freewheeling circuit, the turn-off power electronic device and the coil are turned on, and the coil current begins to decay; When a shutdown control signal is received, the second diode, the resistor and the coil in the secondary freewheeling loop are turned on, the coil current decays to 0, and the electromagnetic buffering process ends.

9. The electromagnetic snubber circuit control method according to claim 8, wherein: Also includes: By adjusting the sending time of the conduction control signal, the start time of the electromagnetic buffer is correspondingly adjusted; By adjusting the interval between the on-control signal and the off-control signal, the duration of the current in the coil and the duration of the electromagnetic buffer are adjusted accordingly.

10. A fast vacuum switch, characterized in that: The electromagnetic buffer circuit according to any one of claims 1 to 7 further comprises: a vacuum interrupter, an insulating pull rod, an electromagnetic repulsion mechanism, a holding device and a buffer device; The vacuum interrupter, the insulating pull rod, the holding device, the electromagnetic repulsion mechanism and the buffer device are connected in sequence; When the fast vacuum switch performs a closing action, the coil of the electromagnetic buffer circuit serves as the opening coil of the electromagnetic repulsion mechanism, and the capacitor in the electromagnetic buffer circuit serves as the opening capacitor of the electromagnetic repulsion mechanism. The buffering effect is achieved by the opening coil of the electromagnetic repulsion mechanism. When the fast vacuum switch performs an opening action, the coil of the electromagnetic buffer circuit serves as the closing coil of the electromagnetic repulsion mechanism, and the capacitor in the electromagnetic buffer circuit serves as the closing capacitor of the electromagnetic repulsion mechanism. The buffering effect is achieved by the closing coil of the electromagnetic repulsion mechanism. When the fast vacuum switch performs a closing action, the capacitor of the electromagnetic buffer circuit discharges toward the closing coil, and an electromagnetic repulsive force is generated between the repulsion disk of the electromagnetic repulsion mechanism and the closing coil, which pushes the repulsion disk to move and drives the moving contact in the vacuum interrupter to move, thereby achieving the closing action of the fast vacuum switch. After a first preset time, the turnable power electronic device in the electromagnetic buffer circuit connected to the opening coil of the electromagnetic repulsion mechanism is turned on, and the capacitor discharges toward the opening coil and generates an electromagnetic repulsive force in the opposite direction of the closing movement, thereby decelerating the repulsion disk and achieving buffering. When the fast vacuum switch performs an opening action, the capacitor discharges to the opening coil, and an electromagnetic repulsive force is generated between the repulsion disk and the opening coil to push the repulsion disk to move and drive the moving contact in the vacuum interrupter to move, thereby realizing the opening action of the fast vacuum switch. After a second preset time, the turnable power electronic device connected to the closing coil is turned on, and the capacitor discharges to the closing coil and generates an electromagnetic repulsive force in the opposite direction of the opening movement, thereby decelerating the repulsion disk and realizing buffering.

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