Monitoramento wireless de eficiência e condição de operação de motores de indução trifásicos

Abstract

Researches conducted by energy distribution companies on several industry segments showed that about 30%of inductionmotors are operating undersized, i.e. with less than 70%of the rated load. Under these conditions induction motors have low efficiency. Due to the characteristics of industrial processes, traditional methods of efficiency and operation analysis can not be used. In order to meet the requirements of these applications, several methods have been proposed. Most of these methods require only the measurement of voltages, currents and in some cases rotor speed. Often these methods estimate, using different techniques, the shaft torque and calculate the output power and efficiency. The purpose of this study is to develop and implement a real-time method to monitor operating conditions and efficiency of induction motors operating at steady state. The proposed method, by means of measured three-phase voltages and currents and the equivalent circuit of the machine, estimates the shaft torque and speed. Then, based on these estimations, calculates the power output and efficiency. The machine equivalent circuit is estimated by an iterative algorithm that uses only the machine nameplate data and the stator resistance. According to present tendencies a wireless system was developed were a central computer can monitor in real time the efficiency and the operational conditions of one or more motors in a industrial plant. This document presents the theoretical development of the proposed method and the results of computer simulations under different situations. Finally it presents an experimental implementation of the method where its performance is evaluated for different motors.