A pressure withstand bypass contactor

Abstract

The utility model discloses a kind of pressure-resistant bypass contactors, it relates to bypass contactor technical field, comprising: insulating shell, inside cavity and cavity inner wall center position are provided with partition, the cavity is divided into high-pressure cavity, isolation cavity and low-pressure cavity by partition from top to bottom, the outside wall of the insulating shell is provided with multiple arc separation plates;Static contact point assembly, including static contact point fixed in the top of insulating shell;Moving contact point assembly, install in the high-pressure cavity, the moving contact point assembly includes dynamic contact bridge, contact head support rod and contact spring, the dynamic contact bridge is floatingly installed on the upper portion of the contact head support rod, the contact spring is arranged between the bottom of the dynamic contact bridge and the center position of the contact head support rod;The utility model realizes reliable isolation of high and low voltage side by umbrella skirt structure, embedded connection and shell partition design, and electromagnet adopts standard low-voltage general piece, compact structure, convenient integration.

Description

Technical Field

[0001] This utility model relates to the field of bypass contactor technology, specifically a pressure-resistant bypass contactor. Background Technology

[0002] In unit-series multilevel high-voltage frequency converters, the contactor bypass function is one of the core technologies to ensure high system reliability. Its necessity is rooted in the inherent characteristics and operational requirements of this topology.

[0003] Multi-level high-voltage frequency converters (typically with AC output voltage levels of 1kV to 35kV) achieve high-voltage output by superimposing multiple independent low-voltage PWM frequency converter power units in series. Each power unit is a complete AC-DC-AC voltage source inverter, including rectification, filtering, and inversion stages. The inverter input side employs a multi-phase-shifting, multi-isolation transformer with multiple secondary sides to supply power to each power unit separately, simultaneously achieving harmonic cancellation, improving the input current waveform, and increasing the input power factor. While this modular design offers advantages such as simple control and good output waveform quality, it also means that the system's reliability largely depends on each power unit connected in series. Due to the large number of power units and the presence of vulnerable electronic components such as IGBTs, capacitors, and drive circuits, their failure rate is the highest in the entire frequency converter system. Statistical data shows that power unit failure is one of the main causes of high-voltage frequency converter downtime.

[0004] In a series configuration, a failure in any power unit (such as IGBT breakdown, capacitor aging, or drive malfunction) will, if left unaddressed, cause the entire series branch to shut down, forcing the entire frequency converter system to halt and severely impacting production continuity. For critical auxiliary equipment in power plants, such as fans and pumps, this could lead to reduced unit output or even unplanned shutdowns. Therefore, a mechanism is essential to quickly and safely disconnect one or more power units from the main circuit in the event of a failure, allowing the remaining healthy units to reorganize and continue operation.

[0005] Currently, there are two main types of bypass methods for high-voltage frequency converter power units: one is electronic bypass technology, which uses power electronic devices such as thyristors as bypass switches, and the other is mechanical bypass technology, which uses contactors as bypass switches. While electronic bypass offers the advantage of rapid turn-on, it also has significant drawbacks: when the inverter bridge's power module begins to conduct, the initial voltage across the thyristor is zero, and the DC voltage of the power unit is directly applied to the anode and cathode of the thyristor, causing it to withstand dv / dt exceeding its tolerance, easily leading to false turn-on and short-circuit faults in the power unit. Furthermore, electronic bypass devices are often integrated with the inverter unit; when overvoltage burns out the inverter unit, the electronic bypass device is also susceptible to damage. In contrast, mechanical contactor bypass offers significant advantages such as strong anti-interference capability, high reliability, clear physical isolation points, and the ability to withstand larger currents. By adding a changeover contactor (containing one normally open and one normally closed contact) at the output of the power unit, when a unit fault is detected, the contactor is controlled to operate, short-circuiting the output terminal of the faulty unit and physically isolating it from the series chain, while directly connecting adjacent units. In this way, the system can continue to operate by sacrificing some output voltage capability (derating) or maintaining a higher output through control algorithms such as neutral point drift, greatly improving the availability and reliability of the entire variable frequency speed control system.

[0006] However, the centralized control bypass scheme commonly used in existing technologies has a significant drawback. Because the contacts of the bypass contactor are connected in series with the high-voltage main circuit, while its drive coil is typically powered by a unified low-voltage control power supply, there is a potential difference of tens of thousands of volts between the two. This necessitates that the contactor itself possess an extremely high "contact-coil" insulation withstand voltage rating (usually matching the inverter's output voltage level, such as 10kV or 20kV). To meet this requirement, existing technologies have had to use expensive and structurally complex special insulation contactors. This not only significantly increases manufacturing costs, leading to a substantial increase in the total cost of the high-voltage inverter; but also, the large size of this high-voltage bypass contactor, to ensure the insulation withstand voltage requirements, results in larger electrical clearances between phase units, ultimately increasing the overall system size, the difficulty of cabinet assembly, and processing costs. The introduced additional structural complexity also potentially reduces the long-term operational reliability of the equipment.

[0007] To address the reliability issues of high-voltage isolated power supply, distributed power supply solutions have emerged in existing technologies. In this approach, each contactor's coil is powered by a corresponding power unit, ensuring that the contactor contacts and coils are essentially at a low voltage potential difference, eliminating the need for high-voltage insulation between them. However, this solution places higher demands on system architecture and control logic and is not universally applicable to all inverter topologies.

[0008] Therefore, how to achieve a highly reliable and low-cost power unit bypass solution without using high-insulation special contactors is a technical problem that urgently needs to be solved in this field. Utility Model Content

[0009] (a) Technical problems to be solved In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a pressure-resistant bypass contactor to solve the problems mentioned in the background art.

[0010] (II) Technical Solution To achieve the above objectives, this utility model provides the following technical solution: a pressure-resistant bypass contactor, comprising: An insulating shell has an internal cavity with a partition wall at the center of the cavity's inner wall. The cavity is divided into a high-pressure chamber, an isolation chamber, and a low-pressure chamber from top to bottom by the partition wall. Multiple arc-blocking plates are provided on the outer wall of the insulating shell. A stationary contact assembly, including a stationary contact fixed to the top of an insulating housing; A moving contact assembly is installed in the high-pressure chamber. The moving contact assembly includes a moving contact bridge, a contact support rod, and a contact spring. The moving contact bridge is floatingly installed on the upper part of the contact support rod, and the contact spring is disposed between the bottom of the moving contact bridge and the center position of the contact support rod. An insulating top rod is installed in the isolation cavity. An insertion hole is provided at the upper end of the insulating top rod. The contact support rod is interference-fitted into the insertion hole. Multiple umbrella skirts are provided on the side surface of the insulating top rod. The electromagnet assembly includes a vertically movable iron core inserted into the low-pressure chamber, a coil, and a reaction spring in the high-pressure chamber. The coil is disposed on the inner wall of the low-pressure chamber. The iron core passes through the coil and its upper end is fixedly connected to the lower end of the insulating top rod. The reaction spring is disposed between the top wall of the high-pressure chamber and the top of the contact support rod. When energized, the iron core moves upward, pushing the insulating top rod upward, which in turn pushes the contact support rod, causing the moving contact bridge to close with the stationary contact. When de-energized, the reaction spring force pushes the contact support rod downward, thereby separating the moving contact bridge from the stationary contact.

[0011] Furthermore, a guide sleeve is provided at the mating part of the isolation cavity and the insulating top rod, and the insulating top rod passes through the guide sleeve.

[0012] Furthermore, the guide sleeve is made of alloy steel.

[0013] Furthermore, the insulating shell is made of fiber-reinforced thermosetting resin.

[0014] Furthermore, the fiber-reinforced thermosetting resin is nylon plastic or bulk molding compound.

[0015] Furthermore, the insulating shell is a one-piece structure formed by injection molding.

[0016] Furthermore, the electromagnet assembly is a low-voltage standard general-purpose electromagnet assembly.

[0017] Furthermore, the insulating top rod is made of high-strength insulating material.

[0018] Furthermore, the multiple umbrella skirts on the side surface of the insulating top rod include large umbrella skirts and small umbrella skirts, which are distributed alternately.

[0019] (III) Beneficial Effects This utility model provides a pressure-resistant bypass contactor, which has the following advantages: 1. This utility model significantly increases the creepage distance through the umbrella skirt structure of the insulating top rod, the embedded connection, and the partitioned cavity design of the shell, ensuring reliable isolation between the high and low voltage sides and meeting the industry standards of DC 1500V and power frequency withstand voltage of 25000V and above. 2. The electromagnet of this utility model uses standard low-voltage universal components, and the insulation function is undertaken by the molded push rod and housing, eliminating the need to select expensive special high-voltage contactors; 3. The insulating top rod of this utility model is limited by a guide sleeve, which can prevent swaying and reduce wear. The shell material is resistant to high temperature and electric arc, and the arc-blocking plate prevents the spread of electric arc, which together ensures long-term stable operation, reliability and long service life. 4. The integrated housing of this utility model reduces the number of parts, has a small external size, requires no additional insulation treatment, can be directly installed in the frequency converter cabinet, reduces the difficulty of system assembly, has a compact structure, and is easy to integrate. Attached Figure Description

[0020] Figure 1 This is a schematic front cross-sectional view of a pressure-resistant bypass contactor according to the present invention; Figure 2 This is a schematic diagram of a pressure-resistant bypass contactor push rod according to the present invention.

[0021] In the diagram: 1. Stationary contact assembly; 11. Stationary contact; 2. Moving contact assembly; 21. Moving contact bridge; 22. Contact support rod; 23. Contact spring; 3. Insulating top rod; 31. Umbrella skirt; 32. Insertion hole; 4. Insulating housing; 41. Arc blocking plate; 42. Partition wall; 5. Electromagnet assembly; 51. Iron core; 52. Coil; 53. Reaction spring; 6. Guide sleeve; 7. High-pressure chamber; 8. Isolation chamber; 9. Low-pressure chamber. Detailed Implementation

[0022] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0023] The present invention will now be described in detail through specific embodiments, as follows: Figures 1 to 2 As shown, this utility model provides a pressure-resistant bypass contactor, including an insulating housing 4, a stationary contact assembly 1, a moving contact assembly 2, an insulating push rod 3, and an electromagnet assembly 5.

[0024] The insulating housing 4 is a one-piece structure formed by injection molding. The insulating housing 4 is made of fiber-reinforced thermosetting resin, preferably nylon plastic (PA) or bulk molding compound (BMC). The BMC material uses unsaturated polyester resin as a matrix, combined with glass fiber and various functional fillers, and is manufactured through precise formulation design and strict process control. The glass fiber length of this material is typically 3-25mm, with a heat distortion temperature of 200-280℃, low shrinkage (0-0.5%), excellent arc resistance (up to 190 seconds), and high insulation performance. The insulating housing 4 made of this material has extremely high insulation resistance, arc resistance, flame retardancy (e.g., V-0 rating), and mechanical strength, and a high heat distortion temperature (long-term temperature can reach above 150℃), enabling it to adapt to the high-temperature environment inside the frequency converter.

[0025] The insulating housing 4 has an internal cavity with a partition wall 42 at the center of the cavity's inner wall. The cavity is divided into a high-voltage chamber 7, an isolation chamber 8, and a low-voltage chamber 9 from top to bottom via the partition wall 42. The high-voltage chamber 7 houses the stationary contact 11 and the moving contact bridge 21 when closed. This chamber is connected to the external main circuit copper busbar or copper screw and has a high voltage. The low-voltage chamber 9 houses the electromagnet assembly 5 (coil 52, iron core 51) and the lower part of the insulating top rod 3. This chamber is the low-voltage control side. The isolation chamber 8, located between the high-voltage chamber 7 and the low-voltage chamber 9, is a relatively sealed sliding chamber through which the insulating top rod 3 passes. The contact support rod 22 of the moving contact assembly 2 slides within this chamber, which is the potential transition zone. Multiple arc-damping plates 41 are provided on the outer wall of the insulating housing 4. These arc-damping plates 41 effectively prevent insulation degradation or short circuits caused by internal arc propagation.

[0026] The stationary contact assembly 1 includes a stationary contact 11 fixed to the top of the insulating housing 4. The stationary contact 11 is made of a copper alloy with high conductivity, and its fixed end extends out of the top of the insulating housing 4 for connection with an external main circuit copper busbar or copper screw.

[0027] The moving contact assembly 2 is installed within the high-pressure chamber 7. The moving contact assembly 2 includes a moving contact bridge 21, a contact support rod 22, and a contact spring 23. The moving contact bridge 21 is floatingly mounted on the upper part of the contact support rod 22, and the contact spring 23 is positioned between the bottom of the moving contact bridge 21 and the center of the contact support rod 22. When the moving contact bridge 21 moves upward under the push of the insulating top rod 3 and closes with the stationary contact 11, the contact spring 23 provides appropriate contact pressure to ensure reliable electrical contact between the moving contact bridge 21 and the stationary contact 11. The lower end of the contact support rod 22 is interference-fitted into the insertion hole 32 opened at the upper end of the insulating top rod 3.

[0028] The insulating rod 3 is installed inside the isolation cavity 8. The insulating rod 3 is made of high-strength insulating material, preferably epoxy resin or special engineering plastic. An insertion hole 32 is provided at the upper end of the insulating rod 3, and the contact support rod 22 is interference-fitted into the insertion hole 32. This embedded connection method can further increase the creepage distance and improve the insulation strength.

[0029] The side surface of the insulating top rod 3 is provided with multiple umbrella skirts 31. The umbrella skirts 31 include large umbrella skirts and small umbrella skirts, which are alternately distributed along the axial direction of the insulating top rod 3. By setting the alternating large umbrella skirts and small umbrella skirts, the creepage distance on the surface of the insulating top rod 3 can be significantly increased, effectively preventing surface flashover in high humidity and polluted environments.

[0030] A guide sleeve 6 is provided at the mating part between the isolation cavity 8 and the insulating top rod 3, and the insulating top rod 3 passes through the guide sleeve 6. The guide sleeve 6 is made of alloy steel, preferably an alloy steel bushing or gasket. The guide sleeve 6 can radially position the insulating top rod 3, ensuring the straightness of the movement trajectory of the insulating top rod 3, avoiding wear caused by swaying during movement, reducing friction, and thus improving the service life and reliability of the entire insulating top rod 3.

[0031] Electromagnet assembly 5 is a low-voltage standard general-purpose electromagnet assembly. Electromagnet assembly 5 includes an iron core 51 vertically movable and inserted into the low-voltage chamber 9, with the upper end of the iron core 51 fixedly connected to the lower end of the insulating top rod 3. Electromagnet assembly 5 also includes a coil 52 wound around the outside of the iron core 51 and a reaction spring 53 at the top of the contact support rod 22. The coil 52 is disposed on the inner wall of the low-voltage chamber 9, the iron core 51 passes through the coil 52 and its upper end is fixedly connected to the lower end of the insulating top rod 3, and the reaction spring 53 is disposed between the top wall of the high-voltage chamber 7 and the top of the contact support rod 22. When the coil 52 is energized, a magnetic field is generated, causing the iron core 51 to move upward, pushing the insulating top rod 3 upward along the guide sleeve 6 within the isolation chamber 8, thereby pushing the contact support rod 22 upward, causing the moving contact bridge 21 to close with the stationary contact 11. When the coil 52 is de-energized, under the action of the reaction spring 53, the iron core 51 drives the insulating top rod 3 and the moving contact assembly 2 to reset, and the moving contact bridge 21 disconnects from the stationary contact 11.

[0032] In this utility model, the stationary contact assembly 1, the moving contact assembly 2, and the electromagnet assembly 5 are all existing technologies, and the connection methods and working principles are fully understood by those skilled in the art.

[0033] In this embodiment, the coil 52 of the electromagnet assembly 5 is powered by a low-voltage control power supply when the withstand voltage bypass contactor is in operation. When it is necessary to disconnect the power unit from the main circuit, the control system energizes the coil 52 of the electromagnet assembly 5. The iron core 51 moves upward under the action of the magnetic field, pushing the insulating top rod 3 to slide upward along the guide sleeve 6 in the isolation cavity 8. The insulating top rod 3 is connected to the contact support rod 22 through the insertion hole 32 with an interference fit, transmitting the thrust to the moving contact assembly 2, pushing the contact support rod 22 to move upward, so that the moving contact bridge 21 overcomes the force of the contact spring 23 and closes with the stationary contact 11. At this time, the bypass contactor short-circuits the output terminal of the faulty power unit, physically isolating it from the series chain, while directly connecting the adjacent units.

[0034] During this process, the alternating large and small umbrella skirts on the side surface of the insulating top rod 3 significantly increase the creepage distance; the insulating shell 4 isolates the high-voltage chamber 7, the isolation chamber 8, and the low-voltage chamber 9 from each other through the partition wall 42, and the arc-damping plate 41 on the outer wall effectively prevents arc propagation; the embedded plug-in connection between the insulating top rod 3 and the contact support rod 22 further increases the creepage distance. The above-mentioned composite insulation structure together ensures reliable insulation isolation between the high-voltage main circuit (the high-voltage chamber 7 where the stationary contact 11 and the moving contact bridge 21 are located) and the low-voltage control circuit (the low-voltage chamber 9 where the electromagnet assembly 5 is located), enabling the contactor to stably withstand the full voltage isolation between the high-voltage frequency converter main circuit (such as 10kV / 20kV) and the low-voltage control circuit, and the insulation performance can meet the industry's high standard requirements of DC 1500V and power frequency withstand voltage of 25000V and above.

[0035] When it is necessary to restore the normal operation of the power unit, the control system cuts off the power supply to the coil 52 of the electromagnet assembly 5. The iron core 51 is reset under the action of the reaction spring 53, which drives the insulating top rod 3 and the moving contact assembly 2 to move downward. The moving contact bridge 21 is disconnected from the stationary contact 11, completing the disconnection operation of the bypass contactor.

[0036] The electrical insulation strength between the stationary contact and the coil was measured using a YDJZ-5kVA / 50kV high-voltage tester. The existing product's power frequency withstand voltage test value was 6kV AC / 1min, while the present invention's power frequency withstand voltage test value was 25kVAC / 1min. The experiment demonstrates that the present invention, through the umbrella-shaped structure of the insulating top rod, the embedded connection, and the partitioned cavity design of the housing, significantly increases the creepage distance, ensuring reliable isolation between the high and low voltage sides.

[0037] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any modifications, alterations, substitutions, and variations made by those skilled in the art to the above embodiments are within the scope of the present invention.

Claims

1. A withstand voltage bypass contactor, characterized in that, include: An insulating shell (4) has an internal cavity and a partition wall (42) is provided at the center of the inner wall of the cavity. The cavity is divided into a high-pressure cavity (7), an isolation cavity (8) and a low-pressure cavity (9) from top to bottom through the partition wall (42). Multiple arc-blocking plates (41) are provided on the outer wall of the insulating shell (4). The stationary contact assembly (1) includes a stationary contact (11) fixed to the top of the insulating housing (4); The moving contact assembly (2) is installed in the high-pressure chamber (7). The moving contact assembly (2) includes a moving contact bridge (21), a contact support rod (22), and a contact spring (23). The moving contact bridge (21) is floatingly installed on the upper part of the contact support rod (22). The contact spring (23) is located between the bottom of the moving contact bridge (21) and the center position of the contact support rod (22). An insulating top rod (3) is installed in the isolation cavity (8). An insertion hole (32) is provided at the upper end of the insulating top rod (3). The contact support rod (22) is interference-fitted into the insertion hole (32). Multiple umbrella skirts (31) are provided on the side surface of the insulating top rod (3). The electromagnet assembly (5) includes an iron core (51) vertically inserted into the low-pressure chamber (9), a coil (52), and a reaction spring (53) in the high-pressure chamber (7). The coil (52) is disposed on the inner wall of the low-pressure chamber (9). The iron core (51) passes through the coil (52) and its upper end is fixedly connected to the lower end of the insulating top rod (3). The reaction spring (53) is disposed between the top wall of the high-pressure chamber (7) and the top of the contact support rod (22). When energized, the iron core (51) moves upward, pushing the insulating top rod (3) upward, thereby pushing the contact support rod (22) to close the moving contact bridge (21) with the stationary contact (11). When de-energized, the reaction spring (53) pushes the contact support rod (22) downward, thereby separating the moving contact bridge (21) from the stationary contact (11).

2. The withstand voltage bypass contactor according to claim 1, characterized in that, A guide sleeve (6) is provided at the mating part of the isolation cavity (8) and the insulating top rod (3), and the insulating top rod (3) passes through the guide sleeve (6).

3. A withstand voltage bypass contactor according to claim 2, characterized in that, The guide sleeve (6) is made of alloy steel.

4. A withstand voltage bypass contactor according to claim 1, characterized in that, The insulating shell (4) is made of fiber-reinforced thermosetting resin.

5. A withstand voltage bypass contactor according to claim 4, characterized in that, The fiber-reinforced thermosetting resin is nylon plastic or bulk molding compound.

6. A withstand voltage bypass contactor according to claim 1, characterized in that, The insulating shell (4) is a one-piece structure formed by injection molding.

7. A withstand voltage bypass contactor according to claim 1, characterized in that, The multiple umbrella skirts (31) on the side surface of the insulating top rod (3) include large umbrella skirts and small umbrella skirts, which are distributed alternately.

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