Analysis of Overhang Effects Using Conductor Separation Method in Coreless-Type PM Linear Machines

The axial overhang of the permanent magnet (PM) has widely been used to enhance the thrust per loss, particularly in air-core structure where the radial flux density is low. This communication investigates PM overhang effects in coreless-type PM linear machines. To analyze the structure where the magnet length exceeds the active length of the mover coil, a new approach using the conductor separation method is introduced and developed to calculate the electromagnetic thrust of the linear machine designed with the overhang magnet. The proposed method is based on an extended 3-D winding factor and a lumped parameter magnetic circuit model to take end effects into account. It is noted that presented overhang analysis can be applicable to any configurations of wound copper coil. The validity of analytical results derived by the proposed method is confirmed by 3-D finite element and experimental results.