Effect of pole embrace on the cogging torque and unbalanced magnetic forces of BLDC motors

One of the important objects in Submarines is reducing or eliminating acoustic noise, where results Submarines hidden from scopes of enemies. BLDC motors are used in submarines, and Cogging torque and unbalanced magnetic forces in BLDC motors are important source of acoustic noise. This paper is a study on the Cogging torque for BLDC motors, with 14 poles and 12 slots. Cogging torque is calculated for various pole embrace by using the finite element method (FEM). The results show that there is optimal pole embrace for minimizing Cogging torque. Unbalanced magnetic forces are introduced by eccentricity between stator and rotor during magnetic process, this paper investigates effect of Pole embrace on the unbalanced magnetic force when rotor eccentricity exists.