Permanent Magnet Synchronous Motors (PMSM) have higher torque to weight ratio as compared to other AC motors. At high speeds p.m. machines also retain higher efficiencies because of reduced iron losses. Hence they have been used for high performance and highspeed applications. However, the unit cost has restricted its use in large numbers in industrial applications. A cost-effective design will be able to achieve a wide spread use of the motor. Of the various rotor architectures, such as, exterior permanent magnet (EPM) and interior permanent magnet (IPM) types, a cost-effective design needs to be evaluated. In this paper we evaluate the rotor architectures on basis of various performance criteria. A finite element method (FEM) of analysis for the design evaluation and optimisation for both EPM and IPM is discussed and the results are presented.