Interferência eletromagnética em redes digitais industriais

Abstract

The use of digital networks and frequency inverters is increasingly common in an industrial environment. The digital network is widely used due to its ease of communication with field devices such as I/O modules (inputs and outputs), sensors, actuators, and even programmable logic controllers. The frequency inverter is widely used due to better efficiency and control of equipment (especially motors) and also better utilization of electrical energy. Inverters have switching devices operating in high frequencies, which produce harmonic distortion in the circuit to which it is attached. This distortion produces electromagnetic induction in circuits that are close to the inverter circuits. As in an industrial environment the proximity between circuits is usual, sensitive circuits become often subjected to eletromagnetic interference, which compromises its operation. Due to their low operating voltages, digital networks are one most sensitive systems in the industry. This text presents a case study of electromagnetic induction in industrial digital networks, caused by frequency inverters. Electromagnetic theory is used to explain this phenomenon and to propose techniques to minimize it. The proposed procedure consists of analyzing the frequency spectrum of inverter currents. Using crosstalk theory, electromagnetic induction due to each frequency component was evaluated in a neighboring circuit. Complete response was obtained using superposition.