Avaliação de parâmetros técnicos e econômicos na substituição de motores de indução trifásicos de 1CV a 10CV

Abstract

This dissertation presents a strategy to determine when to replace motors, focusing on technical and economic analysis. The main objective of this strategy is the conservation of energy in the use of three-phase induction motors in industrial consumers due to the increasing usage of these motors in recent decades. In Brazil, the electricity consumption in 2007 was 376.90 TWh in various sectors of the economy, and induction motors consume about 25%, or 94.22 TWh. Having such a significant share of energy consumption, the need to improve the energy efficiency of these motors became evident. The procedure for energy efficiency improvement originated in 2002, mainly due to electricity rationing in 2001-2002, when the President of the Republic sanctioned decreenumber 4508 (2002), which deals with the specific regulation of the minimum energy efficiency of three-phase squirrel cage induction motors. The decree described the motors in both standard and high yield, and set their performance. Subsequently, ministerial decreenumber 553 (2005), published in December 8, 2005, established the minimum levels of nominal performance, without distinction between standard lines and high yield. The Ministry of Mines and Energy, electric utilities and motor manufacturers have developed intense campaigns to acquire high performance motors or replace the standard motors companies with high-performance motors. However, one should consider in advance whether the acquisition or replacement is advantageous for the end user. In this dissertation, the feasibility of acquisition and replacement of motors was checked, based on an analysis of technical and economic parameters. The motors haveanalyzed powers of 1, 5 and 10 CV, because the track 0 -10 CV represents approximately 86% of motors sold on the Brazilian market over the past twenty years. The analysis of technical parameters consists in checking the conditions of operation of the motors when they operate outside their nominal conditions, such as loading, voltage unbalance, overvoltage, undervoltage, harmonicas, operating temperature and environmental factors. These parameters alter the internal losses of the motors, varying their operating temperatures and changing the motors operational life. The analysis of economic parameters consists in determining the time of return on investment and cost per hour of operation, where costs of the motors, the interest rate market, income, energy rates and demand rates are used in the calculations. In conclusion, the operational lifetime and the time of return on investment are simulated in a computerized environment, using Matlab, for specific conditions related to motor use, and these values are then compared, thus defining the feasibility of the acquisition or replacement of these motors.