3D FEA based investigation of the cogging torque of a claw pole transverse flux permanent magnet machine

The paper is devoted to a 3D finite element analysis based investigation of the cogging torque developed by a three phase claw pole transverse flux permanent magnet machine. Following a discussion of different combinations of the 120°-electrical angle shift between the three axially-arranged phases, we have found that the topology where the 120°-electrical angle shift is applied to the stator magnetic circuits is the most interesting from the point of view of the cogging torque minimization. A deep investigation of this concept shows that the axially arranged phases are magnetically coupled leading to unbalanced contributions to torque of the three phases and therefore to high values of the resulting cogging torque. To overcome this problem, aluminum barriers have been inserted in between the phases.