Parameter estimation of induction motors using a spreadsheet program on a personal computer

Abstract

Abstract Induction motors are used widely in process industries and for domestic applications owing to their simplicity, ruggedness, and low cost. The model parameters of these motors are required in system analysis, fault calculations, sizing of cables, circuit-breakers, voltage drop calculations, transient analysis, and power factor correction calculations. One of the major stumbling blocks is the general lack of design and application data. The design data are generally restricted and are not commonly available to all users. Furthermore, the parameter values are difficult to obtain by field tests. In this paper, a mathematical model is presented to estimate the equivalent circuit parameters from a manufacturer's catalog data. The data used in the estimation include full load speed, rated torque, starting torque, efficiency, and the power factor values at the rated load, 75% and 50% of the rated load. The equations are derived from well-known performance and equivalent circuit models, and solved using a spreadsheet program available for a personal computer. All four main NEMA designs may be taken into account. The estimated parameters include the equivalent circuit values and constant losses. There is good agreement between the estimated values and the limited data obtained from manufacturers. Finally, the usefulness and the limitations of this procedure are discussed.