Analysis of the eddy current and transmission characteristics in asynchronous magnetic coupling with double-layer solid rotor

In order to know the loading condition of double-layer solid rotor asynchronous magnetic coupling, finite element software were used to conduct a transient analysis of the distributions of air gap flux density, eddy current and torque transmission. The results showed that the eddy current presents vortex distribution on the copper layer and that the circuits are divided into 14 by pole pairs. Changing from axle hole to the boundary of the copper layer on the radial direction of the inner rotor, the eddy current distribution is basically constant at the beginning, and then increases gradually. Moreover, the highest eddy current density is in the boundary of the copper layer so that the skin effect of the current is verified. On the circumferential direction of the copper layer, the eddy current periodically changes poles in a cycle, and the number of periods equals the number of permanent magnet pairs of poles. The primary optimal design project was obtained by researching the effect of the asynchronous magnetic coupling characteristics on the different parameters. The eddy current density and torque increased firstly, and then decreased gradually with the increasing thickness of the permanent magnet. The eddy current density and torque achieves maximum simultaneously when the thickness of the permanent magnet is 10 mm. The torque increases firstly, then decreases and the eddy current decreases gradually with the increasing number of pole pairs. When the number of pole pairs is 8, the torque achieves maximum. In order to improve the utilization rate of the permanent magnet and save cost, the thickness of the permanent magnet should be from 9 mm to 11 mm and the number of pole pairs should be 8. The eddy current density and torque decrease gradually with the increasing thickness of the air gap. When magnetic coupling installed, the thickness of the air gap can be from 1 mm to 5 mm. The torque increases firstly, and then decreases gradually with the increasing thickness of the copper layer. The torque achieves maximum when the thickness of the copper layer is 3 mm. Taking depth of penetration, cost of production, dimensions and weight into consideration, the thickness of the copper layer can vary from 2 mm to 5 mm. The torque increases with the increasing axial length ratio of the copper layer and the permanent magnet. Taking the cost of production and torque requirements into consideration, the axial length ratio of the copper layer and the permanent magnet should be from 1.025 to 1.1. Because of its high conductivity, copper is usually chosen as a conductor layer. The results of the simulation and the experimental value were compared to verify the correctness of the simulation analysis. The torque increases with the increasing slip and speed, and it can provide a basis for choosing the appropriate structure size of high power magnetic coupling.