Design and Analysis of an Improved Tubular Permanent Magnet Linear Machine with a T-type Magnet Array

The surface-mounted tubular permanent magnet linear machine (SM-TPMLM) is widely used in many industrial applications. However, the PMs are fragile and easily fall off when linear machines are operated at reciprocating oscillation speed over long periods or encounter harsh environments, the exposed PMs are susceptible to corrosion, which reduces the service life of linear machines. To solve this problem, an improved tubular permanent magnet linear machine with a T-type magnet array (T-TPMLM) is proposed. The axial and radial magnets are combined in a magnetic pole array to increase the thrust force, power and protect the PMs. First, an equivalent analytical model of T-TPMLM is established to predict the magnetic field, the subdomain method with Schwarz-Christoffel mapping method is introduced to consider slotting effect and end effect. Then, to verify the merit of the proposed T-TPMLM, a quantitative electromagnetic performance comparison with two traditional SM-TPMLM including radial magnetization and Halbach magnetization is performed through the finite element analysis method (FEM). Besides, the mechanical strength of three linear machines is discussed briefly. Finally, a prototype of proposed T-TPMLM is manufactured and tested to validate the effectiveness of the analytical model and the FEA predicted results. The results show that the proposed machine offers high electromagnetic performance.