Analytical force calculation in brushless-DC motors I: An alternative approach

In this paper, we focus on the analytical calculation of the tangential forces that generate the armature and the cogging torque in brushless DC machines. We extend previously presented methods using conformal mapping to (i) avoid the singularity of the magnetic flux density at the tooth tip during the transformation and thereby overcome the limitations of this approach with respect to the calculation of the cogging and armature torques developed in electric machines, and (ii) calculate the forces at the slot sides so that the influence of the machine design parameters on the result is directly available.