Abstract : This paper uses Ansoft software to assist in the design and analysis of a linear induction motor, and presents simulation results on the magnetic field distribution and operating performance of the motor. A brief explanation of the simulation method is also provided. Keywords: linear induction motor; Ansoft; performance analysis CLC Number: TM 359.4 Document Code: A [align=center]FEM Inductances of the Electromagnetic Field of Linear Motors Chen Hongyan, Zhang Konglun (Maglev Research Institute, Southwest Jiaotong University, Chengdu610031, Sichuan Province, China) Abstract : The process of design and analysis of linear induction motor can be directed by Ansoft. The distribution of magnetic field and the running performance are described by simulation figures. Key words : linear induction motor; Ansoft; performance analysis 1 Introduction Linear motors are similar to rotary motors. When a three-phase symmetrical current is passed through the primary winding of a linear motor, a traveling wave magnetic field similar to a rotating magnetic field is generated in the air gap, moving in a straight line. Under the action of this magnetic field, the secondary motor will produce directional linear motion. However, linear motors differ from rotary motors in that their cores are discontinuous, unlike the closed circular shape of rotary motors. Instead, the core is long and straight, discontinuous at both ends. Because the core and its windings in the slots are discontinuous, the mutual inductance between phases is unequal. This means that even with a three-phase symmetrical AC voltage applied to the primary winding, the current generated in each phase winding is actually asymmetrical. Using the method of symmetrical components, the three-phase currents of the motor can be decomposed into positive-sequence, negative-sequence, and zero-sequence currents. These three currents correspond to three magnetic fields in the air gap: a positive traveling wave magnetic field, a reverse traveling wave magnetic field, and a pulsating magnetic field. The effects of the reverse traveling wave magnetic field and the pulsating magnetic field exist regardless of whether the secondary reaction is considered; this is known as the first type of edge effect. On the other hand, when the secondary conductor plate of a short-primary linear induction motor moves at high speed relative to the primary, magnetic field distortion occurs at the entry and exit ends of the primary winding. This is due to the eddy currents in the secondary conductor plate weakening the magnetic field at the entry end and strengthening the magnetic field at the exit end. This type of magnetic field distortion is called the second type of longitudinal edge effect. For general electric motors, the ratio of the electromagnetic air gap to the width of the primary core is relatively small, and the width of the secondary core is larger than that of the primary core, so the first type of transverse edge effect can be disregarded. However, due to the influence of the width and conductivity of the secondary conductor plate, the transverse magnetic field distribution becomes uneven, i.e., the second type of edge effect, which also needs to be considered. Because of its special structure, its performance indicators differ significantly from those of traditional rotary induction motors. The existence of transverse edge effects, especially end effects, makes the transient characteristic analysis of linear induction motors much more difficult than that of rotary induction motors. In recent years, the finite element method has been widely used in solving electromagnetic field problems of electric motors. Commercial finite element software has become an important tool for motor design and analysis. Among them, Ansoft's MAXELL 2D software has excellent performance in low-frequency two-dimensional electromagnetic field simulation. This software is used to analyze and study a single-sided linear induction motor. 2. Introduction to MAXELL 2D Software Ansoft is the world's largest provider of professional EDA solutions centered on electromagnetic technology. Ansoft's software suite includes the Maxwell 2D module, a powerful, accurate, and easy-to-use two-dimensional electromagnetic finite element analysis software. Maxwell 2D analyzes systems where eddy currents, displacement currents, skin effects, and proximity effects play a significant role, providing overall characteristics of electromagnetic components such as motors, buses, transformers, and coils. It automatically calculates parameters such as power loss, coil loss, impedance, force, torque, inductance, and energy storage at a specific frequency. It also provides graphical results for the entire phase, including magnetic field lines, magnetic field strength (H), magnetic flux density (B), energy density, and temperature distribution. Furthermore, it automatically calculates force, torque, inductance, and saturation problems in various linear, nonlinear, and anisotropic materials. The transient field module is used when the voltage and current sources are non-sinusoidal, or when the object in the model is in translational or rotational motion, or when physical quantities such as magnetic field, energy, force, power loss, and velocity are functions of time. This feature is particularly convenient for modeling, analyzing, and calculating linear induction motors. Maxwell 2D/3D software is widely used in fields such as electrical engineering, electronics, automotive, aerospace, biomedicine, and defense. Major companies and institutions in these fields worldwide, including Siemens, General Motors, and NASA, are widely involved. 3. Electromagnetic Analysis of Linear Induction Motors . Compared to other commercial finite element analysis software, Maxwell 2D software is relatively simple to use. Users only need to answer the question being calculated as input to obtain the desired results; they do not need to understand the detailed process of the finite element method. Using Maxwell 2D software to simulate and analyze linear induction motors, the most important step is to build a simulation model. The process is as follows: 1. First, select the solver; here we choose Transient solver. 2. Draw the two-dimensional geometric model of the motor based on the design dimensions of each part. 3. Determine the material properties of each part of the linear induction motor. 4. Determine the boundary conditions and external power supply for the finite element calculation. 5. Select the execution parameters, such as force, torque, and losses. 6. Determine the dynamic parameters. This includes determining the motion boundary, applied load, and time step. After completing the above six steps, Maxwell 2D software can perform instantaneous parameter scanning and solving on this model. 4 Modeling and Solving Based on the above steps, this paper conducts a simulation analysis of the no-load starting of a flat, single-sided composite secondary linear induction motor. The motor design parameters are shown in Table 1. [align=center]Table 1 Linear Induction Motor Example Parameters[/align] The geometric model in Ansoft is shown in Figure 1. [align=center]Figure 1 Linear Induction Motor Model in ANSOFT Maxwell 2D[/align] 4.1 Magnetic Field Analysis Figure 2 is the two-dimensional finite element mesh of the linear induction motor. [align=center]Figure 2 Finite Element Mesh Result[/align] Figure 3 shows the magnetic field distribution at t=0.325 seconds. [align=center]Figure 3 Magnetic Field Distribution at t=0.325s[/align] Figure 4 shows the distribution of magnetic flux density in the air gap with position at t=0.325 seconds. [align=center]Figure 4 Distribution of magnetic flux density in the air gap with position (t＝0.325s)[/align] 4.2 Simulation Results The curves of thrust and normal force during the start-up of the linear induction motor are shown in Figure 5. [align=center]Figure 5 Simulation results of the linear induction motor[/align] These curves are consistent with common experimental curves. In addition, coil current, voltage, induced electromotive force, rotor flux linkage, etc. can also be observed. Using Maxell2D to conduct electromagnetic analysis and simulation studies on the linear induction motor, the electromagnetic field distribution of the motor can be obtained, and the transient performance of the linear induction motor can be reflected. Through simulation analysis, the complex process of "design-prototype-correction" can be avoided. For designers, software analysis can help to discover design defects in a timely manner, adjust design parameters appropriately, and optimize the performance of the motor. References : 1. Liu Guoqiang, Zhao Lingzhi, Jiang Jiya. Finite Element Analysis of Engineering Electromagnetic Fields using Ansoft [M], Beijing: Electronic Industry Press, 2005: 133-143. 2. Qiu Changli, Zhang Hongmei, Liu Shaoke. Performance Analysis of Linear Induction Motor Based on Ansoft, Micromotors, 2006.11:22-26. 3. Zhang Hongmei. Simulation of Traction System of Linear Induction Motor and Calculation of Electromagnetic Force in Maglev Transportation. Master's Thesis, National University of Defense Technology, 2005. Author Biography : Chen Hongyan, (1982-), female, Master's student. P.O. Box 242, Jiuli Campus, Southwest Jiaotong University, Postcode: 610031