Influence of the slot opening width and rotor pole radius on the cogging torque and total torque developed by a three-phase permanent magnet synchronous motor (PMSM) is investigated. The number of motor poles and number of stator slots are fixed. Finite element technique is used for the computation of machine characteristic. Core saturation is directly considered in the magnetic field calculation. Formulation based on two methods, virtual work and Maxwell stress tensor is used to find the torque.