This paper presents a detail analysis of flux control for high performance and high speed operation of an interior permanent magnet synchronous motor (IPMSM). In this work, an algorithm for flux control is proposed to achieve optimum efficiency over the wide speed range of IPMSM. Improved figures are presented to analyze the performances of the IPMSM. The operating speed limit of the motor can be expanded efficiently with the proposed field control. The complete drive incorporating proposed flux control is successfully implemented in real time for a laboratory 5 hp motor using digital signal processor (DSP) board DS1104. The performance of the proposed flux control technique is tested both in simulation and experiment at different operating conditions. A performance comparison of a drive with proposed field control and a drive without field control is also provided. The effectiveness of the proposed flux control algorithm is evidenced by the results.