An improved algorithm for direct computation of optimal voltage and frequency for induction motors

Owing to the constant v/f operation of induction motors which are commonly employed in conveyor belt drives, the core and copper losses are generally high. The load cycles of the drives are mostly limited to light and medium load conditions with full speed range. Hence any effort to minimize the losses can bring significant savings in energy and therefore in running costs. In this paper a unique loss minimization algorithm is proposed for an Induction Motor Drive (IMD) whereby the input voltage and frequency of the motor are optimized to minimize the total losses. The proposed algorithm is based on the steady state model of induction machine. Hence the analysis and the applications are restricted to steady state operating conditions. A comprehensive analysis of the drive performance under different operating conditions and a Loss Minimization Control (LMC) algorithm for the determination of the optimal input voltage and frequency are presented. Further, a comparison of steady state performance of the proposed LMC and that with the Field Oriented Control (FOC) is carried out. Results of MATLAB simulations and laboratory tests on the drive under study reveal that the drive efficiency is increased, especially at light load condition.