Abstract : Visualization simulation technology is a new technological field integrating multiple fields such as computer graphics, image processing, computer-aided design, and human-computer interaction. This paper studies the application of this new technology in low-voltage electrical appliances. Based on the physical process of the arc during the opening of a low-voltage circuit breaker, an arc model based on magnetohydrodynamics (MHD) and a back-side breakdown physical model mainly based on thermal breakdown are established. This simulation algorithm is combined with three-dimensional visualization technology to conduct a visual simulation study of the arc motion during the opening process of a low-voltage circuit breaker. Keywords: Circuit breaker, visualization simulation 1 Overview Visualization simulation is a new technological field that emerged in the 1990s. It involves multiple fields such as computer graphics, graphics processing, computer-aided design, computer vision, and human-computer interaction. In the field of engineering design, visualization simulation or scientific computing visualization is defined as the visualization processing or three-dimensional graphic and animation display of data obtained from scientific computing or simulation calculations, allowing users to interactively change parameters to observe the overall picture and changes of the calculation results. Because scientific computing visualization has extremely important significance and practical value for the development of various disciplines and engineering technologies, this technology has received great attention since its inception. Achieving visualization in scientific computing has many important implications. It can greatly accelerate data processing speed, enabling the effective utilization of massive amounts of data; it can transform engineering phenomena that are difficult or impossible to observe into physical mechanisms that allow people to discover and understand the objects being designed and studied, thereby proposing specific measures to improve the design; it can guide and control the calculation process, allowing for convenient and rapid changes to the original data and conditions of the design and calculation through graphical interaction, and displaying and observing the impact of changes to the original data on the basic characteristics of the design and research object through 3D graphics or animation, thus achieving the goal of optimizing the design. (Source: Power Transmission and Distribution Equipment Network) The arc-extinguishing chamber of low-voltage electrical appliances is generally a small chamber formed by the wall of the appliance. The arc breaking process takes place inside the arc-extinguishing chamber and is very short, making it difficult to observe with the naked eye. Quantitatively grasping and understanding the changes in physical parameters such as arc temperature, ion concentration, gas pressure, and airflow velocity within the arc-extinguishing chamber is even more challenging. In recent years, advancements in magnetohydrodynamic (MHD) numerical analysis have made it possible to simulate the breaking process of low-voltage electrical appliances using physical and mathematical models of electric arcs. Combining this simulation algorithm with 3D visualization technology allows the breaking process of the arc within the arc-extinguishing chamber to be displayed on a computer screen, enabling observation of the arc's movement within the chamber, as well as the distribution and changes in temperature and flow field. This has significant implications for the future design of low-voltage electrical appliance arc-extinguishing chambers. Currently, the rapid development of graphics and computer technology has made 3D spatial visualization simulation on microcomputers possible. This paper, based on magnetohydrodynamics and integrating calculations of flow field, electromagnetic field, and temperature field, establishes a dynamic mathematical model for the breaking arc of a low-voltage circuit breaker. Developed using Visual C++ on the Windows 98 platform, and utilizing the Windows 98-based 3D graphics module, a user-friendly interface is created. This interface displays the arc's movement in 3D space during breaking and represents parameters such as temperature and airflow graphically, thus realizing a visualization simulation software system for low-voltage circuit breaker breaking. 2. Mathematical Model of Arc Breaking in Low-Voltage Circuit Breakers The arc breaking in a circuit breaker satisfies the following equations: Mass continuity equation; Momentum conservation equation: Mass force; v: Velocity; P: Pressure; Energy equation: ρ: Density; h: Enthalpy; T: Temperature (K); t: Time (s); K: Thermal conductivity; s: Heat source term. The current density in each element of each layer is: where G is conductivity, determined by the temperature of element i,k in that layer. The energy emitted by the arc radiation is: QR = A.ε.K.(T₄-T₄₀) A: Surface area; ε: Emissivity; K: Boltzmann radiation constant; T: Temperature; T₀: Ambient temperature; The arc plasma in the magnetic field is driven by the magnetic force: When the arc plasma moves in the magnetic field, it generates an induced current and is subjected to a force from the magnetic field, opposite to the direction of fluid motion, thus resisting the fluid's movement. 3. Visual Simulation of Arc Breaking Process Visualization is defined as the visualization processing or 3D graphical and animated display of data obtained from scientific or simulation calculations. The 3D visualization simulation software for low-voltage circuit breaker breaking developed in this paper is written in Visual C++ on the Windows 98 platform. Utilizing a system-based 3D graphics module, it displays the arc movement during the breaking process in 3D space in an animated manner and plots the simulated breaking voltage and current waveforms. In the simulation of the low-voltage circuit breaker breaking process, it is necessary to calculate the current in the circuit where the circuit breaker model is located and the coupling field of the arc to understand the changes in physical parameters such as arc temperature, ion concentration, gas pressure, and airflow velocity within the arc-extinguishing chamber. The simulated voltage and current waveforms are shown in Figure 1. The arc voltage gradually increases, and when the arc enters the grid, the voltage rapidly rises to a higher value, the current is limited, and then back-side breakdown occurs, causing the arc voltage to drop. The calculation results are basically consistent with the experimental results. The temperature distribution and flow field within the arc-extinguishing chamber at 0.85 ms are shown in Figure 2. Figure 1 shows the simulated circuit breaker breaking voltage and current waveforms. Figure 2 shows the calculated temperature distribution and flow field inside the arc-extinguishing chamber at t=0.85ms. This visualization system is based on database technology. With the continuous improvement of automation, integration, and intelligence, data management in the system has become increasingly complex. The data management system is required to support data transfer and sharing between application layers. Engineering data types are complex, including not only vectors and dynamic arrays, but also engineering data objects with complex structures. Engineering objects may have different definition patterns at different design stages, thus requiring modification and expansion of the definition pattern according to actual needs. Data management adapted to engineering characteristics is required. Therefore, the powerful DAO database class provided in Visual C++ MFC is adopted. DAO-based data classes in MFC are more powerful than ODBC-based data classes. DAO-based data classes obtain data through the Microsoft Jet database engine. It supports Data Definition Language (DDL) operations, such as creating databases, adding new tables to databases, or defining new fields in tables. Three-dimensional graphics can be divided into wireframe, surface, and solid model models. Solid modeling is an advanced technology, and several commercial systems are now available. It is particularly suitable for studying interference and collision checks of complex mechanisms, calculating the mass characteristics of objects, and realistic display of objects. Therefore, it has become the main geometric modeling method in CAD systems. Microsoft proposed a universal 3D graphics specification for Windows 98 & NT and X-Windows platforms. However, this 3D graphics specification is geared towards low-level operations and only provides operations on points, lines, and surfaces, which is far from sufficient for the development of a visualization simulation CAD system for electrical appliances. This visualization simulation system requires solid display and frequently requires 3D drawing. Therefore, an object-oriented programming technique was used to create a class library suitable for this system. The CGLWnd class inherits from the MFC window CWnd class and is mainly used for initializing the drawing device for 3D drawing. class CGLWnd: public CWnd {…… public: void Init(); Initializes the 3D display device protected: afx-msg void OnMouseMove(UINT nFlags, CPoint point); Responds to mouse events……}; The CMcb class is used to encapsulate the circuit breaker as an object, and its member functions are responsible for the visualization display. The normal vector of the 3D computational object, the brightness of the material, determines the light intensity, and a solid representation with shadows is drawn. `void DrawT();` draws the temperature field distribution of the circuit breaker; `void DrawFlow();` draws the airflow field; `void DrawI();` draws the circuit breaker breaking current waveform; `void DrawU();` draws the breaking voltage waveform; `void DrawArc();` draws the 3D arc during circuit breaker breaking; `void Draw3D();` draws the 3D of the circuit breaker. The 3D simulation of a low-voltage circuit breaker breaking is shown in Figure 3. The arc is just generated at 0.14ms, and by 0.9ms, the arc has fully developed and advanced to the entrance of the arc-extinguishing grid; at 2.7ms, the arc exits the arc-extinguishing chamber, resulting in back-end breakdown and a drop in arc voltage. Afterward, the arc burns relatively stably within the arc-extinguishing chamber until it is extinguished. The entire arc-ignition time during breaking is 4.8ms. Figure 3. Three-dimensional simulation of arc motion during low-voltage circuit breaker opening. 4. Conclusion This paper discusses the visualization simulation system, a novel technical field integrating computer graphics, image processing, computer-aided design, and human-computer interaction. It highlights the significant role of visualization simulation technology in the design of low-voltage electrical products. A low-voltage circuit breaker visualization simulation system was implemented in Visual C++ on the Windows 98 platform. Based on magnetohydrodynamics (MHD), a physical and mathematical model of the arc was established to simulate the low-voltage electrical breaking process. Combining this simulation algorithm with three-dimensional visualization technology allows the arc breaking process within the arc-extinguishing chamber to be displayed on the computer screen, observing the arc's movement within the chamber, as well as the distribution and changes in temperature and flow field. Applying this technology in the design of low-voltage electrical products can significantly improve the technical level of low-voltage electrical appliances and promote the development of low-voltage electrical appliances in China.