A Simulation Method for the Combined Model of Arcing and Repulsive Force Mechanism Movement of a Mechanical Switch

Abstract

The present invention discloses a simulation method for the combined motion of the arcing and repulsive force mechanism of a mechanical switch, comprising the following steps: establishing a two-dimensional axisymmetric magnetohydrodynamic (MHD) arc model according to an experimental model, the model including cup-shaped transverse and longitudinal magnetic contact copper electrodes, copper electrodes, and a fluid domain; setting a flow field module, a thermal field module, an electric field module, and a magnetic field module according to the MHD arc model; setting a motion field model of the repulsive force mechanism, including an electromagnetic field module and a solid mechanics field module; simulating a repulsive force metal disc, an insulator pull rod laminated spring, an armature for closing and opening holding, and a moving contact in a magnetohydrodynamic arc extinguishing chamber connected to the pull rod according to the actual motion process of the mechanical switch; performing a mesh generation operation on the MHD arc model and the motion field model of the repulsive force mechanism established in the above steps. According to the technical solution of the present invention, the simulation results can reflect the arcing characteristics in the arc extinguishing chamber during the opening process of the switch, which affects whether the switch can extinguish the arc and reliably turn off within the specified time.

Description

Technical Field

[0001] The invention belongs to the technical field of DC circuit breaker interruption, and particularly relates to a simulation method for the combined model of mechanical switch arc burning and repulsive force mechanism movement. Background Art

[0002] With the rapid development of renewable energy technologies, the power system has continuously increased requirements for power transmission capacity and power supply reliability. The flexible DC transmission technology has many advantages such as good controllability, large transmission capacity, and low line loss, and can effectively solve the problem of new energy grid connection. However, compared with the traditional AC system, the DC power grid has the characteristics of small impedance and fast rising speed of short-circuit current. Therefore, high requirements are put forward for the fast and reliable interruption of high-voltage DC circuit breakers used for control and protection.

[0003] The research on the interruption characteristics of DC circuit breakers is of crucial significance in multiple fields. In the high-voltage DC transmission system, the performance of DC circuit breakers directly affects the power transmission efficiency and system stability. In the field of industrial automation, DC circuit breakers are used to control various electric devices, and their performance is closely related to the continuity and reliability of the production process.

[0004] During the opening and closing processes of the repulsive force mechanism, the stress distribution on the key components of the mechanism is uneven, and corresponding impact deformations are generated, which directly affect the reliability and stability of the repulsive force mechanism. The research on the arc burning characteristics of DC circuit breakers involves multiple complex factors, including the thermodynamic behavior of the arc, the dynamic characteristics of the arc, the stability of the arc, the arc energy release mechanism, the control of the arc length, the temperature distribution of the arc, and the arc extinguishing process, etc. These factors are directly related to the performance, life, and stable operation of the circuit breaker.

[0005] Therefore, it is of great significance to analyze the key components by using the combined simulation model method of the arc burning model coupling multiple physical fields of fluid field, thermal field, electric field, and magnetic field and the movement model of the repulsive force mechanism coupling electromagnetic field, solid mechanics field, and field-circuit coupling, and to study the interruption characteristics of the overall mechanism linkage of the mechanical switch of the DC circuit breaker. Currently, there is a lack of research in this area. For the research on the repulsive force mechanism part, most of them analyze the single electromagnetic field, and few perform field-circuit coupling multi-physical field calculations by combining the electromagnetic field with other physical fields and circuits. Regarding the characteristics and mechanisms of the arc, with the wide use of various detectors, although the physical process of hot plasma can be understood. However, in the closed vacuum arc chamber system, the measurable vacuum arc parameters are limited, and the experimental environment is extremely harsh. Therefore, simulation modeling is needed to reveal the mechanism and characteristics of the vacuum arc. In summary, using an accurate model to study the action process of the electromagnetic repulsive force mechanism and the principles of arc plasma change and particle dynamic behavior is the key factor for evaluating the breaking ability of fast mechanical switches. Summary of the Invention

[0006] In view of the above problems and technical requirements, the present invention proposes a simulation method for the combined movement of the arcing and repulsive force mechanism of a mechanical switch, including the following steps: S110, establish a two-dimensional axisymmetric magnetohydrodynamic (MHD) arc model according to the experimental model, and the MHD arc model includes a cup-shaped transverse and longitudinal magnetic contact copper electrode, a copper electrode, and a fluid domain; S120, set the flow field module, the thermal field module, the electric field module, and the magnetic field module according to the established MHD arc model above; S130, set the motion field model of the repulsive force mechanism, and the motion field model of the repulsive force mechanism includes an electromagnetic field module and a solid mechanics field module. The electrical parameter results of this model are input as the parameters of the electromagnetic field domain of the discharge coil in the motion field model of the repulsive force mechanism, that is, the circuit current is coupled with the discharge coil under the electromagnetic field domain setting to form a field-circuit coupling; S140, according to the actual motion process of the mechanical switch, simulate the repulsive force metal disc, the insulator pull rod laminated spring, the armature for closing and opening holding, and the moving contact in the magnetohydrodynamic arc extinguishing chamber connected by the pull rod, and simulate the motion process of the above moving parts; S150, perform the necessary mesh generation operation in the finite element software on the MHD arc model and the motion field model of the repulsive force mechanism established in the above steps.

[0007] In the above method, the simulation in step S110 includes: forming a magnetohydrodynamic equation set that conforms to the characteristics of arc plasma, and the equation set includes:

[0008] Mass conservation equation:

[0009] (1)

[0010] Radial momentum conservation equation:

[0011] (2)

[0012] Axial momentum conservation equation:

[0013] (3)

[0014] Energy conservation equation:

[0015] (4)

[0016] Wherein, is the density, is the radial distance, is the height, is the heat transfer coefficient, is the radial current density, is the axial current density, - dynamic viscosity coefficient, - constant pressure heat capacity, - thermal conductivity, - Electrical conductivity, - Plasma pressure, - Radial velocity, - Axial velocity, - Temperature, where 、 、 、 The four parameters are all non - linear functions of temperature, 、 、 、 are the four basic variables of the temperature field, is the Boltzmann constant, is the elementary charge, and are the Lorentz force terms. The left - hand side of Equation (4) is the convection term, and the right - hand side, in order from left to right, is the Joule heat term, the radiation term, the heat conduction term, the heat conduction term, and the electron enthalpy transport term caused by electron drift. The radiation term is represented by the net radiation source term built into the software.

[0017] Current continuity equation:

[0018] (5)

[0019] Maxwell's equations:

[0020] 6)

[0021] Ohm's law:

[0022]

[0023] (7)

[0024] In Equation (5), - Electrical conductivity, - Electric potential. In Equation (6), is the vacuum permeability. In Equations (2) to (4), the current density 、 、the self - induced magnetic field are obtained using Equations (6) and (7).

[0025] In the above method, the step "S120. According to the established MHD arc model above, set the flow field module, the thermal field module, the electric field module, and the magnetic field module" includes: setting the moving contact, the static contact, the fluid domain, the central axis, and the physical field boundary.

[0026] In the above method, the setting of the fluid domain includes: setting the two electrodes in the arc extinguishing chamber as solids and air as the fluid domain; the setting of the physical field boundary includes: setting thermal insulation in the boundary setting, and at the same time setting the initial temperatures of the two electrodes and the fluid domain to normal temperature.

[0027] In the above method, in the electric field module, set electrical insulation and grounding, and set the normal current density at the boundary of the copper electrode; in the magnetic field module, set all boundaries except the central axis as magnetic insulation.

[0028] In the above method, step “S140. According to the actual movement process of the mechanical switch, simulate the repulsive metal disk, the insulator pull rod stack spring, the armature for closing and opening holding, and the moving contact in the magnetohydrodynamic arc extinguishing chamber connected to the pull rod, and simulate the movement processes of the above moving components” includes:

[0029] The total body load force of the upper pull rod connected to the moving contact is the axial stack spring elastic force F p_contact , the total body load force of the repulsive metal disk is the axial electromagnetic force Fz given by the field-circuit coupled discharge coil to the repulsive disk, and the total body load force of the lower pull rod is the resultant force of the axial stack spring elastic force F p_bar and the magnetic force F B of the holding armature:

[0030] (11)

[0031] Equation (11) is the axial stack spring elastic force of the lower pull rod, where k p is the elastic coefficient, s p is the stack spring deformation, s p0 is the initial compression of the stack spring, s c is the moving contact displacement, k r is the rigidity coefficient;

[0032] (12)

[0033] (13)

[0034] Equation (12) is the force on the moving contact, that is, the total body load force of the upper pull rod connected to the moving contact, and equation (13) is the magnetic force of the permanent magnet that keeps the switch in the state on the armature, k B is the magnetic force coefficient.

[0035] In the above method, step "S150. Perform the necessary mesh generation operation in the finite element software on the MHD arc model and the motion field model of the repulsive force mechanism established in the above steps" includes: for the fluid domain in the MHD arc model, the range of the mesh generation element size is: 0.025 - 0.875 cm; for the boundary of the electrode, the mesh is divided into an element size range of: 0.01 - 0.7 cm, and the shapes are all triangular; for the motion field model of the repulsive force mechanism, the range of the mesh generation element size is: 0.1 - 0.2 cm.

[0036] The beneficial effects of the present invention are as follows:

[0037] (1) Simplify according to the basic theoretical model and apply it to the dynamic process of the mechanical switch opening, which is beneficial to the study of the mechanical switch stress;

[0038] (2) Simulate the opening dynamic process of the mechanical switch in the DC circuit breaker. The simulation results can reflect the arc burning characteristics in the arc extinguishing chamber during the switch opening process, such as the electrical signal characteristics such as current and voltage, as well as the temperature field and magnetic field characteristics, which affect whether the switch can extinguish the arc and turn off reliably within the specified time;

[0039] (3) Simulate the repulsive force mechanism process of the mechanical switch in the DC circuit breaker. The simulation results can reflect the motion characteristics of the repulsive force mechanism during the actual switch opening process, such as the moving distance and speed of the switch moving contact and the repulsive force disk, the circuit parameter results of the discharge circuit, and the stress conditions borne by each component, which directly affect the reliability and stability of the repulsive force mechanism. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 FIG. shows a schematic flow chart of a simulation method for the combined model of mechanical switch arc burning and repulsive force mechanism movement according to an embodiment of the present invention.

[0041] Figure 2 FIG. shows a schematic diagram of a combined simulation model of a repulsive force mechanism and arc burning in an arc extinguishing chamber according to an embodiment of the present invention.

[0042] Figure 3 FIG. shows a setting diagram of the boundary conditions of an arc extinguishing chamber constrained by a control equation according to an embodiment of the present invention.

[0043] Figure 4 FIG. shows an equivalent circuit diagram of the discharge of a repulsive force mechanism according to an embodiment of the present invention.

[0044] Figure 5 FIG. shows a setting diagram of the boundary conditions of the moving parts of a mechanical switch according to an embodiment of the present invention.

[0045] REFERENCE SIGNS:

[0046] 210 - The copper electrode of the cup-shaped transverse and longitudinal magnetic contact at one end, 220 - Copper electrode, 230 - Fluid domain other than the copper electrode, 310 - Central axis, 320, 330 - Two boundaries of the electrode, 340 - Boundary, 350 - Copper electrode, 360 - Copper electrode, 370 - Gas domain, 510 - Upper pull rod, 520 - Lower pull rod, 530 - Repulsive metal disc. Detailed implementation manners

[0047] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be fully conveyed to those skilled in the art.

[0048] Figure 1 A schematic flowchart showing a simulation method for the combined model of arc burning and repulsive mechanism movement of a mechanical switch according to an embodiment of the present invention. Figure 2 A schematic diagram showing a two-dimensional axisymmetric model of a mechanical switch according to an embodiment of the present invention. The following will be combined with Figure 1 and Figure 2 to describe this method. As Figure 1 shown, this method includes the following steps:

[0049] S110, establish a two-dimensional axisymmetric magnetohydrodynamic (MHD) arc model according to the experimental model, and this arc model includes a cup-shaped transverse and longitudinal magnetic contact copper electrode, a copper electrode, and a fluid domain. Figure 2 A schematic diagram showing a combined simulation model of a repulsive mechanism and an arc burning in an arc extinguishing chamber according to an embodiment of the present invention. In Figure 2 , the part above the axial direction of the upper pull rod is the MHD arc model established in this step. As Figure 2 shown, 210 represents the copper electrode of the cup-shaped transverse and longitudinal magnetic contact at one end, 220 represents the copper electrode, and 230 represents the fluid domain other than the copper electrode. Among them, the experimental model refers to the arc extinguishing chamber model of the mechanical switch breaking test, and Figure 3 shown is the two-dimensional axisymmetric schematic diagram of this experimental model. Establishing the MHD arc model according to the experimental model means establishing the MHD arc simulation model based on the physical object of the arc extinguishing chamber of the mechanical switch prototype.

[0050] To facilitate the convergence of simulation calculations and reduce the complexity of simulation, the following assumptions can be introduced during the simulation to constrain the arc model in the arc extinguishing chamber. The constraints include: (1) Assume that the solved arc plasma is in equilibrium, that is, it satisfies the local thermodynamic equilibrium state; (2) Assume that the arc plasma is axisymmetric and the flow of the arc plasma generated by the electromagnetic force is laminar; (3) The density, conductivity, thermal conductivity, constant-pressure heat capacity, and dynamic viscosity coefficient of the plasma are only functions of temperature; (4) The influence of the arc on the contact ablation and the near-pole sheath is ignored in the simulation.

[0051] The simulation in step S110 also includes: Combining the actual situation of the arc plasma to form a magnetohydrodynamic equation set that conforms to the characteristics of the arc plasma. This equation set includes:

[0052] Mass conservation equation:

[0053] (1)

[0054] Radial momentum conservation equation:

[0055] (2)

[0056] Axial momentum conservation equation:

[0057] (3)

[0058] Energy conservation equation:

[0059] (4)

[0060] In equations (1) to (4), is the fluid density, is the radial distance of the model, is the height of the model, is the heat transfer coefficient of the fluid, is the radial current density of the model current, is the axial current density of the model current, - The dynamic viscosity coefficient of the model material, - The constant-pressure heat capacity of the model material, - The thermal conductivity of the model material, - The conductivity of the model material, - Plasma pressure, - The radial velocity of the fluid, - The axial velocity of the fluid, - The temperature of the fluid. Among them 、 、 、 All four parameters are non-linear functions of temperature, , , , are the four basic variables of the temperature field. is the Boltzmann constant, is the elementary charge. and are the Lorentz force terms. The left side of Equation (4) is the convection term, and the right side of the equation, in order from left to right, is the Joule heat term (the main cause of the arc rise), the radiation term, the heat conduction term, the heat conduction term, and the electron enthalpy transport term caused by electron drift. The radiation term is represented by the net radiation source term built into the software.

[0061] Current continuity equation:

[0062] (5)

[0063] Maxwell's equations:

[0064] (6)

[0065] Ohm's law:

[0066] ,

[0067] (7)

[0068] In Equation (5), - conductivity, - potential. In Equation (6),

[0069] is the vacuum permeability. In Equations (2) to (4), the current density , , the self-induced magnetic field are obtained using Equations (6) and (7).

[0070] The system of partial differential equations composed of the above Equations (1) to (7) is the formula used for simulation calculations. Using the above formulas, the flow field, temperature, electric field, and magnetic field of the plasma can be solved. The calculation results are related to the selection of boundary conditions and plasma parameters (conductivity, thermal conductivity, constant pressure heat capacity, dynamic viscosity coefficient, density).

[0071] S120. According to the established MHD arc model above, set the flow field module, thermal field module, electric field module, and magnetic field module in the MHD simulation model. As Figure 3 shown, the flow field module includes the entire arc extinguishing chamber, i.e., the moving and static electrodes and the arc extinguishing chamber. The thermal field module includes the entire arc extinguishing chamber. The electric field module includes the entire arc extinguishing chamber. The magnetic field module includes the entire arc extinguishing chamber.Figure 3 A setup diagram showing the boundary conditions of the arc extinguishing chamber constrained by the control equations according to an embodiment of the present invention. As Figure 3 shown, the arc extinguishing chamber includes: a central axis 310, two boundaries 320 and 330 of the electrode, a boundary 340, a copper electrode 350, a copper electrode 360, and a gas domain 370. The relationships between the reference numerals 310 - 370 shown above and Figure 2 the cup-shaped transverse and longitudinal magnetic contact copper electrodes 210, copper electrode 220, and fluid domain 230 in the above are as follows: The reference numerals 310 - 370 refer to the boundary regions in the simulation model, and some physical field conditions need to set boundary conditions with the boundary as the target. While the reference numerals 210, 220, and 230 shown are domain regions, which are the material bodies. The reference numerals 310 - 370 shown are the boundary selection objects of the reference numerals 210 - 230 shown.

[0072] The following describes the settings in the simulation:

[0073] Settings are made for the flow field, thermal field, electric field, and magnetic field modules in the MHD arc model. The objects to be set include the moving and static contacts, the fluid domain, the central axis, and other physical field boundaries.

[0074] First, describe the settings of the fluid domain: The flow state of the fluid is divided into two types: laminar flow and turbulent flow. When the fluid velocity is large enough, its flow state will change from laminar flow to turbulent flow. In this simulation, the arc is a free arc, assuming that the fluid is in a laminar state, and the gas flow field is selected as a single-phase model in laminar flow. The entire air domain is affected by the body force (Lorentz force). In fluid heat transfer, since the electrode and air are two types of substances, and the heat transfer modes of the two types of substances are different, these two parts are separately set in the simulation. The two electrodes (the copper electrode 350 as the static contact and the copper electrode 360 as the moving contact) are set as solids, and the air (gas domain 370) is set as a fluid, and different formulas are used to process them respectively. Due to the settings of the boundary conditions of the central axis for the moving and static contacts and the fluid domain, the boundary conditions are replaced by the moving and static contacts and the fluid domain.

[0075] The following describes the settings of the physical field boundary:

[0076] Set thermal insulation in the boundary setting, that is (n is the unit area, q is the conductive heat flux), and at the same time, set the initial temperatures of the electrodes (copper electrode 350 and copper electrode 360) and the gas domain 370 to normal temperature.

[0077] Both the electric field module and the magnetic field module belong to the AC / DC module. In the electric field module, the entire calculation region follows the law of conservation of current. Set electrical insulation, that is (where n is the unit area and J is the current density). With the ground set (V = 0), the normal current density is set at the boundary 320 of the electrode 350, enabling coupling with the circuit. In the magnetic field module, except for the central axis 310, all boundaries including those of the two electrodes (copper electrode 350 and copper electrode 360) are set as magnetically insulated.

[0078] Electrodes are divided into cathodes and anodes. Therefore, the temperature coupling at the plasma-electrode interface is divided into two categories: one is the temperature coupling at the anode-electrode interface, and the other is the temperature coupling at the cathode-electrode interface. In arc plasma, there are two types of particles: positively charged ions and negatively charged electrons. When a suitable voltage is applied across the electrodes, the cathode emits electrons towards the anode. At the same time, the positive ions in the plasma move towards the cathode with a certain acceleration, which causes the electrode temperature to rise. As the temperature increases, the hot cathode emits more electrons, which is also the reason for cathode cooling. This is the mechanism of cathode thermionic emission adopted in this simulation. So, in the temperature coupling at the plasma-electrode boundary, the formula used for the cathode is:

[0079] (8)

[0080] (9)

[0081] (10)

[0082] The left - hand side term of equation (8) is the heat flux. The first term on the right - hand side is the heat flux generated by electrons, and the second term is the heat flux generated by ions. n is the unit area, k is the correction coefficient, ▽T is the temperature gradient, is the electron current density, is the work function of the electrode surface, is the ion current density, is the ionization potential. Equation (9) is the calculation formula for the electron current density, which adopts the calculation formula for the saturated emission current density of the cathode. Among them, is the effective Richardson constant (Richardson constant), 𝑞 is the electron charge, is the work function of the electrode surface, is the Boltzmann function. Equation (10) is the calculation formula for the ion current density, where, is the normal current density at the interface.

[0083] S130, set the motion field model of the repulsive mechanism. The motion field model of the repulsive mechanism includes an electromagnetic field module and a solid mechanics field module. The electrical parameter results of this model are input as the parameters of the discharge coil electromagnetic field domain in the motion field model of the repulsive mechanism, that is, the circuit current is coupled with the discharge coil under the electromagnetic field domain setting to form a field - circuit coupling. The equivalent circuit of the field - circuit coupling discharge is asFigure 4 as shown, where C is the opening energy storage capacitor and L eq is the equivalent inductance model of the coil.

[0084] S140. According to the actual movement process of the mechanical switch, simulate the repulsive metal disk, the insulator pull rod laminated spring, the armature for opening and closing holding, and the moving contact in the magnetohydrodynamic arc extinguishing chamber connected by the pull rod, and simulate the movement process of the above moving components. The boundary conditions of the above moving components not only include the solid mechanics domain, and the movement of the components is the result of the coupling of multiple physical fields. The solid mechanics domain represents the movement process, which refers to: setting the body load quantity of the movement of the moving components (the total axial force of the body load of the upper pull rod connected to the moving contact is set as the axial laminated spring elastic force F p_contact , the total axial force of the body load of the repulsive metal disk is set as the axial electromagnetic force Fz given by the field-circuit coupled discharge coil to the repulsive disk, and the total axial force of the body load of the lower pull rod is set as the axial laminated spring elastic force F p_bar and the resultant force of the magnetic force F B of the holding armature. )

[0085] Figure 5 shows the boundary condition setting diagram of the mechanical switch moving components according to the embodiment of the present invention. As Figure 5 shown, the total axial force of the body load of the upper pull rod 510 connected to the moving contact is the axial laminated spring elastic force F p_contact , the total axial force of the body load of the repulsive metal disk 530 is the axial electromagnetic force Fz given by the field-circuit coupled discharge coil to the repulsive disk, and the total axial force of the body load of the lower pull rod 520 is the resultant force of the axial laminated spring elastic force F p_bar and the magnetic force F B of the holding armature.

[0086] (11)

[0087] Equation (11) is the axial laminated spring elastic force of the lower pull rod, where k p is the elastic coefficient, s p is the laminated spring deformation, s p0 is the initial compression of the laminated spring, s c is the displacement of the moving contact, k r is the rigidity coefficient.

[0088] (12)

[0089] (13)

[0090] Equation (12) is the force on the moving contact, that is, the total axial force of the body load of the upper pull rod 510 connected to the moving contact, and equation (13) is the magnetic force of the permanent magnet that keeps the switch in the on state on the armature, k B is the magnetic force coefficient.

[0091] S150. Perform the necessary mesh generation operation in the finite element software on the MHD arc model and the motion field model of the repulsive mechanism established in the above steps.

[0092] According to the embodiments of the present invention, two modes of mesh generation can be adopted: one is to divide according to the default element shape and size of the software, and the whole process is controlled by the physical field; the other is to divide according to the user-defined element shape and element size.

[0093] Regarding the division according to the user-defined element shape and element size, the following need to be considered: In the calculation of the finite element software, the mesh generation is very important. The number, quality, refinement degree, and density distribution of the meshes all have a crucial impact on the convergence of the system of equations to be solved. Slight defects in the mesh will affect the calculation process, resulting in non-convergence of the results and thus unable to complete the simulation calculation. The finer the mesh generation is not necessarily the better. The finer the mesh is divided, the more system resources will be occupied during the calculation process, and the calculation time will be longer, but the accuracy of the calculation results is not greatly improved. From this perspective, in fact, the denser the mesh is not necessarily the better, and it should be set in combination with the actual situation of the model.

[0094] In the embodiments of the present invention, in combination with the actual situation of the model operation, for the fluid domain in the MHD arc model, the mesh is divided into refined meshes, and for the electrode boundary, the mesh is divided into relatively refined meshes. The refined element size range is: 0.025 - 0.875 cm, the relatively refined element size range is: 0.01 - 0.7 cm, and the shape is triangular; in the repulsive mechanism, the mesh is divided into user-defined mapped quadrilateral meshes, and the mesh size is (the element size range is: 0.1 - 0.2 cm).

[0095] According to an embodiment of the present invention, the process of division may further include dynamic mesh setting: when the local mesh is elongated and deformed as the contact moves, and the mesh quality coefficient at the last time step before the solver stops is lower than a preset threshold, the solution process is paused, and a set of meshes is re-meshed according to the initial mesh parameters for this moment. After the mesh adaptation is completed, the solution calculation continues until the next mesh re-meshing. After several such re-meshing processes, the calculation of the entire time domain is completed. The time when the solver stops depends on the criterion of the finite element simulation solution process. For example, the calculation will end at the previous moment when the model error is too large and does not converge and reports an error. Among them, the local mesh of this model is the mesh of the moving part of the model, namely the simulation repulsive metal disk, the insulator pull rod laminated spring, the armature for closing and opening holding, and the mesh of the moving contact in the magnetohydrodynamic arc extinguishing chamber connected by the pull rod. The solver is a method tool for solving the model by finite element simulation software. The MUMPS solver can be selected. The time step is the time step for solving the transient result of the model. The mesh quality coefficient is the threshold for the distortion of the mesh during movement. When the mesh quality is lower than this value, the calculation under this mesh division will stop. The threshold is selected as 0.2. The initial mesh parameters are the corresponding parameters of the mesh division part before the solution. The object for re-meshing a set of meshes is the part where the mesh quality is lower than the threshold. The entire time domain refers to the transient result time of the solution. The solution calculation includes all physical field results of the entire model. The following describes the dynamic mesh setting with an example. For example, when the switch opens the circuit, the static contact is fixed, the moving contact opens, and the moving parts of the repulsive mechanism move. Specifically in the implementation of the simulation, the dynamic mesh technology is selected to make the simplified moving contact move with the solution time. The movement of the moving contact will inevitably affect the mesh quality around it. When the mesh is elongated and deformed to a certain extent, the calculation result will be incorrect and the calculation cannot continue. This requires updating the mesh with a mesh quality lower than the mesh quality threshold according to the real-time mesh quality during the simulation calculation, that is, the automatic re-meshing of the mesh. When the local mesh is elongated and deformed as the contact moves, and the mesh quality coefficient at the last time step before the solver stops is lower than the preset threshold of 0.2, the solution process is paused and a set of meshes is re-meshed according to the initial mesh parameters for the mesh with a mesh quality lower than the threshold. After the mesh adaptation is completed, the solution calculation continues until the next mesh re-meshing. After several such re-meshing processes, the calculation of the entire time domain is completed. Different from the previous dynamic mesh using the specified mesh velocity, since the specified mesh displacement option is adopted, it is necessary to make the material coordinates of the moving contact move together with the geometric coordinates to meet the calculation requirements of the circumferential opening of the contact. This requires that the simulation calculation must relate the material coordinate system and the geometric coordinate system through a mathematical expression and move simultaneously.

[0096] Based on the simulation results of the co-simulation model, namely the MHD arc model and the moving field model of the repulsive mechanism, the DC breaking process of the moving and static contacts of the mechanical switch can be studied, and certain simulation methods and theoretical references can be provided for the optimal design of the fast mechanical switch.

[0097] According to the technical solution of the present invention, the separation process of the moving and static contacts of the model is expressed by the movement of the moving contact. The input quantity of the movement process part of the moving contact is the result calculated by the solid mechanics part of the field-circuit coupling model of the repulsive mechanism. The field-circuit coupling model of the repulsive mechanism part includes the electromagnetic field, the solid mechanics field and the circuit. Under the combined action, the movement of the moving part of the repulsive mechanism drives the movement of the moving contact of the arc extinguishing chamber. Therefore, the simulation method of the combined model of the MHD arc model and the moving field model of the repulsive mechanism is realized.

[0098] In the specification provided herein, a large number of specific details are described. However, it can be understood that the embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures and technologies are not shown in detail so as not to obscure the understanding of this specification.

[0099] Although the present invention has been described based on a limited number of embodiments, those skilled in the art in this technical field will understand, based on the above description, that other embodiments can be conceived within the scope of the present invention thus described. In addition, it should be noted that the language used in this specification is mainly selected for the purpose of readability and teaching, rather than for the purpose of interpreting or limiting the subject matter of the present invention.

Claims

1. A method for simulating the joint model of arcing and repulsion mechanism motion of a mechanical switch, characterized in that: The following steps are involved: S110, establishing a two-dimensional axisymmetric magnetohydrodynamic (MHD) arc model according to the experimental model, wherein the MHD arc model includes a cup-shaped transverse and longitudinal magnetic contact copper electrode, a copper electrode, and a fluid domain; S120, according to the MHD arc model established above, setting a flow field module, a thermal field module, an electric field module, and a magnetic field module; S130, setting a repulsion mechanism motion field model, wherein the repulsion mechanism motion field model includes an electromagnetic field module and a solid mechanics field module, and the electrical parameter results of the model are used as parameter inputs of the electromagnetic field domain of the discharge coil in the repulsion mechanism motion field model, that is, coupling the circuit current with the discharge coil under the electromagnetic field domain setting to form field-circuit coupling; S140, according to the actual movement process of the mechanical switch, simulate the repulsive metal disk, the insulator pull rod stack spring, the armature for opening and closing retention, and the moving contact in the magnetohydrodynamic arc extinguishing chamber connected by the pull rod, and simulate the movement process of the above moving parts; S150, performing a meshing operation in finite element software on the MHD arc model and the repulsion mechanism motion field model established in the above steps; Step S120 includes: Set the moving contact, static contact, fluid domain, central axis and physical field boundary; The setting of the fluid domain includes: setting two electrodes in the arc extinguishing chamber as solids and setting air as the fluid domain; The settings of the physical field boundary include: setting thermal insulation in the boundary settings, and setting the initial temperatures of the two electrodes and the fluid domain to normal temperature; In the electric field module, electrical insulation and grounding are set, and the normal current density is set on the boundary of the copper electrode; in the magnetic field module, all boundaries except the central axis are set to magnetic insulation.

2. The method for simulating the joint model of arcing and repulsion mechanism motion of a mechanical switch according to claim 1, characterized in that: The simulation of step S110 includes: forming a set of magnetohydrodynamic equations that conform to the characteristics of arc plasma, the set of equations including: The mass conservation equation: （1） Radial momentum conservation equation: （2） Axial momentum conservation equation: （3） Energy conservation equation: （4） in, is the density, is the radial distance, is the height, is the heat transfer coefficient, is the radial current density, is the axial current density, - dynamic viscosity coefficient, -Heat capacity at constant pressure, - thermal conductivity, - electrical conductivity, - plasma pressure, - radial velocity, - axial speed, - Temperature, where , , , All four parameters are nonlinear functions of temperature. , , , There are four basic variables about the temperature field. is the Boltzmann constant, is the elementary charge, and is the Lorentz force term, the left side of the equation in equation (4) is the convection term, and the right side of the equation is, from left to right, the Joule heat term, the radiation term, the thermal conduction term, the thermal conduction term, and the electron enthalpy transport term caused by electron drift, where the radiation term is represented by the net radiation source term built into the software: Current continuity equation: （5） Maxwell's equations: （6） Ohm's Law: ， （7） In formula (5) - electrical conductivity, -potential, in formula (6), is the vacuum permeability, and the current density in equations (2) to (4) is , , self-induced magnetic field Use equations (6) and (7) to find .

3. The method for simulating the joint model of arcing and repulsion mechanism motion of a mechanical switch according to claim 1, characterized in that: Step "S140, according to the actual movement process of the mechanical switch, simulating the repulsive metal disk, the insulator pull rod stack spring, the armature for opening and closing, and the moving contact in the magnetohydrodynamic arc extinguishing chamber connected by the pull rod, and simulating the movement process of the above moving parts" includes: The total load force of the upper pull rod connected to the moving contact is the axial spring force F p_contact The total body load force of the repulsive metal disk is the axial electromagnetic force Fz given to the repulsive disk by the field-circuit coupling discharge coil, and the total body load force of the lower pull rod is the axial lap spring force F p_bar and the armature holding force F B The combined force: F p_bar = （11） Equation (11) is the axial spring force of the lower tie rod, where k p is the elastic modulus, s p is the deformation of the lap spring, s p0 is the initial compression of the spring, s c is the displacement of the moving contact, k r is the stiffness coefficient; F p_contact = （12） F B = （13） Equation (12) is the force on the moving contact, that is, the total body load force of the upper pull rod connected to the moving contact, and equation (13) is the magnetic force of the permanent magnet on the armature to maintain the switch state, k B is the magnetic coefficient.

4. The method for simulating the joint model of arcing and repulsion mechanism motion of a mechanical switch according to claim 1, characterized in that: Step "S150, performing the necessary meshing operation in the finite element software on the MHD arc model and the repulsion mechanism motion field model established in the above steps" includes: For the fluid domain in the MHD arc model, the mesh unit size range is: 0.025-0.875 cm, for the electrode boundary, the mesh unit size range is: 0.01-0.7 cm, and the shape is all triangular; for the repulsive mechanism motion field model, the mesh unit size range is: 0.1-0.2 cm.

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