Effectiveness of Induction Motor Model Order for Machine Parameters Estimation in Sensorless Control Drive

In speed sensorless induction motor drive, motor model with detailed information assumes paramount importance. The use of reduced order model reduces the computation time which is more desirable when on-line estimation of machine parameters is required. The reduced order models give sufficiently accurate results in some cases, but they cannot be used in general with all the machine ratings. Performance of the machine is evaluated by eigenvalue analysis. In this paper, a detailed comparative analysis of reduced order and full order models of 3-phase induction motor is presented. The eigenvalue analyses of linearized models are carried out for different inputs and outputs under variable speed condition. Effect of change in input frequency, slip and stator resistance is demonstrated for different machine ratings ranging from 3 HP to 2250 HP. Our findings suggest that, the choice of full order and reduced order models are based on the HP rating of the machine. This simplifies the decision of algorithm of estimation and the implementing device. The study was carried out in MATLAB environment