Low inductance axial flux BLDC motor drive for more electric aircraft

As the aircraft technology is moving towards more electric architecture, use of electric motors in aircraft is increasing. Axial-flux BLDC motors are becoming popular in aero application because of their ability to meet the demand of light weight, high power density, high efficiency and high reliability. Axial-flux BLDC motors in general and ironless axial flux BLDC motors in particular, come with very low inductance. Because of this they need special care to limit the magnitude of ripple current in motor winding. In most of the new more electric aircraft applications, BLDC motor needs to be driven from 300Vdc or 600Vdc bus. In such cases, particularly for operation from 600Vdc bus, IGBT based inverters are used for BLDC motor drive. IGBT based inverters have limitation on increasing the switching frequency, and hence they are not very suitable for driving BLDC motors with low winding inductance. In this paper, three-level NPC inverter is proposed to drive axial flux BLDC motors. Operation of BLDC motor driven from three-level NPC inverter is explained and experimental results are presented.