The Study, Based On The Finite Element Method For High-speed Cylindrical Linear Induction Motor Performance

This thesis is a research on the performance of cylindrical linear induction motor based on a numerical method-finite element method (FEM).In the beginning, it introduces the basic principles of FEM. It makes a mathematical analysis of cylindrical linear induction motor and presented electromagnetic hypothetic condition, solution region and boundary conditions from the field point of view. And derives the nonlinear time-stepping finite element equations of two-dimensional electromagnetic field under the voltage source excitation. Selects the electromagnetic simulation software Ansoft Maxwell as the research tool, and introduces the simulation processes and parameters-setup methods. It builds the motor's simulation model, and calculates the starting force and current, showing the correctively of simulation model compared with experimental results.Then, it makes a research on the air gap magnetic field of cylindrical linear induction motors. The thesis gives a mathematical description of the motor's no-load air-gap magnetic field, simulates the motor's transient characteristics. Obtained many curves such as thrust, primary current and flux density, and analysis the influence of the air-gap length variation on the magnetic field distribution and the starting performance.After that, it makes a research on the edge effect of cylindrical linear induction motors. As the linear motor iron core's breaking, causes the discontinuous magnetic circuit and longitudinal edge effect, it makes the magnetic field distortion and its performance significantly lower than the normal rotating induction motor. This thesis gives the equations of air gap field strength under the influence of edge effects. And the magnetic field distribution under the influence of edge effects is analyzed. The results show that edge effects make the into end magnetic filed weakening and the leaving end magnetic field strength.Finally, it analyzes the influence of different secondary materials and excitation power on the performance of motor. It presents the thrust curve along with secondary material's thickness, conductivity and the thrust curve along with power's frequency and voltage. The results showed that the thickness and conductivity's influence on the thrust are not monotonic, more over, the relationship between motor thrust and power frequency, voltage value in a certain range has a good linearity. The results above provide a basis to determine the best secondary material and to design the motor operation control system.The result of study shows that the finite element method used to study cylindrical linear induction motor performance can get more accurate results.