Performance of torus-type brushless DC motor with toothed and toothless stator core

摘要

In a traditional torus motor, the stator has a slotless winding. If the empty space between the adjacent coils is filled with ferromagnetic material (an iron powder composite or laminated iron), then the magnetic flux density increases significantly. Primarily, this influences the rotor speed (at a given, constant supply voltage), and the electromagnetic torque. To obtain the same speed as for the toothless stator the magnetic flux should be reduced to the previous level by reducing the thickness of the permanent magnets. Otherwise, leaving the increased flux density in the air gap requires that the number of turns in the stator winding has to be reduced. In this paper the authors address the questions concerning what is gained and what effects on the motor performance are achieved if the magnet volume, or the number of turns are reduced after the space between the coils has been filled with magnetic material.