The interior permanent magnet synchronous motor (IPMSM) has many advantages like high torque density, high efficiency, and a wide range of operation area since the reluctance torque and magnetic torque can be
applied simultaneously. However, cogging torque that is generated by difference in magnetic resistance due to salient rotor topology and its position is one of the most important factors to be considered while designing an IPMSM as it causes vibration and noise. This paper presents a method for reduction of cogging torque in IPMSM by using random optimization. Random optimization is a constrained stochastic approximation procedure that uses random-direction finite difference gradient estimates. Random optimization is advantageous in cases where the objective function is unclear or cannot be differentiated. In this paper, the use of improved random optimization technique than the existing one for optimal design of IPMSM with minimized cogging torque is proposed.