Steps towards a sinusoidal back EMF for a claw pole transverse flux permanent magnet synchronous machine

This paper presents a new method to achieve an almost sinusoidal back EMF for a claw pole transverse flux permanent magnet synchronous machine (TFPM) using some appropriate geometrical modifications. To fulfill this goal, instead of using a constant length for the air gap, a rotor position dependent air gap is suggested. Air gap facing surfaces of the stator teeth and rotor flux concentrators are modified to build this variable air gap. It will be shown that in addition to proper shaping of the rotor poles, the air gap facing surface of the stator teeth should be curved to achieve a sinusoidal back EMF. Based on the obtained results from finite element analysis of the machine under no load condition, the proper shape of these surfaces is determined.