Estudo comparativo entre a utilização de cabo comum ou cabo de dupla blindagem na instalação de um conversor de frequência relativo à atenuação de ruídos eletromagnéticos

Abstract

In industrial plants the target is to maximize the processes through automation in order to obtain higher quality products at lower cost. In this context, AC induction motors are widely used for these processes due facility of operation, durability and relatively low maintenance costs. In order to control the motor speed, a frequency converter is used in the circuit. This speed control technology developed on recent decades has been consolidated with numerous manufacturers. However, what is not yet well known, is that kind of devices may be a source of electromagnetic interference, especially in data communication cables from the industrial plant that are close to the power cables which connect motors to converters. This paper aims to present a comparative study of the use of standard cables (unshielded), and a double shielded cable as connection between an induction motor and its associated frequency converter, related to of electromagnetic waves emission that are potentially interference agents. In this document comparisons are shown between electrical and magnetic interference that occur in three types of analog signals: square wave, voltage signal from 0 to10 volts and current signal from 4 to 20 mA, there was used only one control cable model, disposed therein together with the power cables. The analyzes proposed are qualitative due to the difficulty to measure the intensity of the interference. To outline the topic and take in the goal, the results are presented as a comparative measurement between the power cables. Measurements were performed in an industrial environment, so the results presented contain noise from other equipment, the final analysis and conclusion do not allow establishing the best power cable to be used in this type of installation.