Projeto de circuitos e metodologia para análise preliminar dos efeitos do envelhecimento magnético em transformadores eletrônicos de baixa potência

Abstract

This project aims to develop a control circuit and analyze preliminarily any possible alteration on the physical characteristics of a low power transformer’s core. This study is a great contribution to the field due to the vast utilization of transformers in multiple applications, as well as the fact that magnetic aging is the main cause of the decrease of magnetic efficiency on transformers, and its effects are often overlooked in the studies of low power transformers. Magnetic aging can be caused either by the time effect or high stress levels in magnetic materials, and can be verified by analyzing four different parameters: hysteresis loop, magnetization current, the magnetization time of the core and the efficiency. For the current project, transformers were submitted to different tests, operating below rated current, at rated current, above rated current and in short circuit. For the tests at rated current and below it the transformers were directly connected to the AC power supply during the whole testing time. On the other hand, the short circuit test and the test above rated current needed to be controlled by an external circuit in order to prevent any injuries to the coils. The external circuit controls the time that each transformer is energize and the time of rest for each one. This control circuit was made by a power circuit that uses a TRIAC (semiconductor device that works as a switch in alternated current circuits) along with a microcontroller based on the Arduino platform.