Optimized Structure of Axial Flux Permanent Magnet Motors used as Submarine's Propulsion in Order to Reduce Torque Ripple

Today, the permanent magnet motors are widely used in various industries especially military applications due to such characteristics as high efficiency, low weight and high energy density. Torque ripple is an inherent characteristic of this type of motors. Time and space harmonics produced by the motor drive and the motor structure itself give rise to torque ripples in these motors. Geometric structure of the magnets and stator slots lead to cogging torque (one of the causes of torque ripple) in these motors. This unwanted torque component causes noise, vibration and motor starting issues. It also creates bubbles in the application of these motors as the submarine's propulsion. It should be noted that bubbles could lead to submarine detection which is undesirable in military application. This paper provides analytical formulations and validation by threedimensional finite element analysis to reduce this unwanted torque. This is an important step in achieving the goals of the country's marine industries organization.