Performance and Drive Characteristics of Slotless Axial Flux Motors

Axial Flux Motors (AFM) can be more suitable for some applications than radial flux motors due to volume density characteristic. Slotless motors can facilitate the manufacturing process that requires core lamination in the same direction as the motor rotation. Removing the slots from the motor and placing the windings in the air gap (air gap winding) have an important impact on motor performance and drive characteristics, mainly due to the low winding inductances values. The behavior of a motor with a low inductance value driven by a frequency inverter was evaluated. The motor was tested with and without an output filter for comparative purposes. The behavior of the motor in the laboratory test was also observed by finite elements analysis.As a solution for the design, a switching frequency of 15 kHz was proposed instead of the standard 4 kHz, reducing the current harmonic by 51,2%. Also, an external inductor can reduce the current harmonic by 43,7%. In both alternatives, the temperature and motor losses were significantly reduced.For an application study, a coreless motor was dimensioned for a ventilation application. To fulfill the specification. With the proposed motor, it was possible to reduce 51% of the motor axial length.