Topology and preliminary design of slotless brushless DC motor

A brushless DC motor with cup-shaped windings fixed on the cylindrical iron core without using slots, so-called slotless brushless DC (SLBLDC) motor, can reduce the cogging torque to negligible value. This paper describes the preliminary design of a sinusoidally fed SLBLDC motor, including the geometry of winding and magnets, a novel approach to calculating the major dimension and the airgap flux density based method (AFDBM) for determining each dimension of the motor structure and especially optimizing the magnets.