Influence of Stator Structure on Electromechanical Parameters of Torus-Type Brushless DC Motor

Five torus-type brushless dc motors, each with a different version of the stator core structure, are analyzed. The first one is a slotless stator core, and the four others have the space between the adjacent coils of stator winding filled with the material made either of iron powder composite or laminated iron. An analysis of the motor performance is based on a three-dimensional (3-D) field motor model as well as on the circuit model of the inverter plus the motor set supplied from the battery. The toothed stator core versions show a significant increase of the average torque and also an increase of torque ripple caused mainly by the rise of cogging torque. The analysis based on the simulation results is backed by measurements carried out on the prototype of slotless stator version of the motor.