Materials and Fabrication

Stator cores of AFPM brushless machines are made of laminated steels or soft magnetic powder materials. Soft magnetic powders simplify the manufacturing process and reduce the cost of AFPM machines.

Most laminated cores for stators of AFPM brushless machines are made of nonoriented (isotropic) silicon steel ribbons with standard thickness from 0.12 to 0.64 mm. Nonoriented steels are Fe-Si alloys with a random orientation of crystal cubes. Magnetic properties are practically the same in any direction in the plane of the sheet or ribbon. A secondary recrystallization process is not needed and high temperature annealing is not essential. Nonoriented grades contain between 0.5% and 3.25% Si with up to 0.5% Al addition to increase the resistivity and lower the temperature of the primary recrystallization.