| Permanent magnet synchronous linear motor is a device which can directly convertthe electrical energy into linear motive force energy.Compared with conventional rotary motor, it can deliver the motor thrust to the workbench without using intermediate transmission machine, thus driving the load for linear motion.At the same time, with the advantages ofthe simple structure,large thrust, high reliability and fine dynamic performance, it has a bright prospect of applyingin high-speedtrain, industrial automation, electromagnetic gun and many other fields.However,because of the end effect and the cogging effect caused by its structure, disturbance in magnetic resistance force, load and system parameter may exist. These factors can wave the motor’s output thrust, which is directly related to its stability and positioning accuracy, making the application oflinear motor in industry constrained.Permanent magnet synchronous air-core linear motor, whose stator windings are air-core, can avoid the cogging effect and weaken the side effect. Stability of motor thrust can be improved at the sacrifice of its maximum force, thus making the control easier. When using the motor in high-speed transport, the train can run more smoothly and without electricity, reducing the harm of electromagnetic radiation to human. In this paper, the thrust performance of permanent magnet synchronous air-core linear motor is studied as the core, the motor structure and its thrust are analyzed. Then simulation in ANSYS, one finite element software, is carried out to validate the results.Firstly, motor thrust is calculated using circuit theory. Based on its air-core feature, permanent magnet is regarded as electrical coils under the excitation equivalent method, and the mutual inductance between the excitation coil and primary winding coil is calculated. Then, by using virtual work principle, horizontal thrust is obtained, and the relationship between horizontal thrust and motor’s main structure parameters is analyzed.Secondly, simulation on electromagnetic field distribution of the permanent magnet synchronous air-core linear motor is carried out using finite element software ANSYS. Then, the horizontal thrust is calculated. In the two-dimensional model created, horizontal thrust under different structure parameters are simulated to verify the analytical calculation results.Finally, considering that there is no iron gap in the air-core windings, the cogging force has already been weakened. If replacing the conventional radial permanent magnet array by the Halbach permanent magnet array, which shows unilateral assembled magnetic, thrust can be more stable. Using ANSYS, influences on horizontal thrust by the two different structureof magnet array are analyzed. Meanwhile, by adopting the fractional slot in the primary windings, the ripple in output thrust can be reduced. |
