The Structure Design And Electromagnetic Analysis Of Permanent Magnet Linear Switched Reluctance Motor

Linear switched reluctance motor is a type of new special motor which combine the characteristic of switched reluctance motor and principle of linear motor. It can not only achieve linear motion with high speed and high precision, but also has the advantages of simple structure and easy maintenance. However, due to the fact that linear switched reluctance motor has the advantages of switched reluctance motor, and at the same time, inherits its own shortcomings, the energy conversion density of LSRM is generally lower than that of the electromagnetic linear motor or magnetic track linear motor, and the running thrust ripple is large, which lead to the outstanding noise issues and the resonance problems in motor at the particular frequency. Usually in the electromagnetic field, the magnetic resistance force of motor is larger than the ampere force, therefore, the magnetic resistance is the main motive force of LSRM, which can obtain greater electromagnetic force. Ampere force usually has a linear relationship with the coil current, and the conditions of magnetic resistance force lead to the difficulty of control of ampere force, which result in the shortcomings above. In view of the existing prototype model, this paper introduced high performance permanent magnet in the motor structure, which increased the power density ratio of motor, reduced the magnetic reluctance thrust pulsation and reduced the influence of noise on the operation of the motor. After the improvement, and because of the change of operation principle and structure of prototype model, the permanent magnet linear switched reluctance motor has been designed.The main research contents and achievements of this paper are as follows:1. In view of the existing linear switched reluctance motor, the 3D model was built in ANSYS/Maxwell, on the basis of finite element analysis model, the change of electromagnetic force in the process of rotor motion were analyzed by software module of analysis of dynamic changes of transient magnetic field, the waveform electromagnetic thrust variation within a single period was gotten. The high performance permanent magnet materials were embedded in sub teeth and yoke of single phase of rotor respectively, and under the same excitation conditions, the electromagnetic thrust variation waveform was gotten in the motion process. Finally, permanent magnets were embedded in sub teeth and yoke at the same time, and the model of PMLSRM was built based on transient analysis.2. Based on the 3D model of PMLSRM designed, the distribution of magnetic field of rotor and stator under different location conditions was analyzed by using module of static magnetic field in software, so did the air gap magnetic flux density. The change waveforms of coil flux and inductance within the case of no-load and load in one period were gotten with transient magnetic field analysis module. The effects of electrical excitation and permanent magnet excitation mode for the operating performance of the motor was observed, the reason the waveform of electromagnetic force changed was derives and analyzed.3. The Schwarz Christoffel transformation analysis and calculation were made for the air gap magnetic field of improved motor model, and the influence of both side end effect and cogging effect were taken care of, the analytical expressions of linear motor magnetic field distribution were derived. On the basis of which, electromagnetic force was calculated by Maxwell stress tensor method, the results of which were compared with that from finite element method. The feasibility and accuracy of Schwarz Christoffel transformation method in magnetic field analysis were verified.4. The motor control strategy was summarized. A constant off time peak current control PWM method was proposed. The simulation of constant off time module and peak current control module were did respectively, the current waveforms of both were obtained. Analysis showed that this type of motor control method can ensure the constant power switching frequency, so as to the rapidity and stability of current control, which validated that this control strategy is feasible and superior in the servo system of permanent magnet linear switched reluctance motor.