An investigation of the effect of three-dimensional tooth top protrusions magnet overhang in radial flux motors

The use of end winding flux with overhanging magnets to improve torque density is well known. Recently, claim is made that protruding the tooth top over the end winding can further increase the end winding torque as a three-dimensional flux flow is introduced. The argument against this practice is, the protruded tooth top on the end winding will divert the fringing flux from overhanging magnets to the tooth core creating a funnel effect. This paper investigates the validity and the argument against the claim by analyzing the effect of tooth top protrusion on magnet overhang in stators made with soft magnetic composite materials. Finite element simulations are validated through performance testing done on two sets of prototypes, one built with lamination and no top extrusion, the other with soft magnetic composites with top protrusion