Topology and preliminary design of slotless brushless dc motor

A brushless de motor with cup-shaped windings fixed on the cylindrical iron core without using slats, 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.