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Design and Construction of a Variable Autotransformer for Laboratory Applications

Abstract:

A three-phase autotransformer with a variable output voltage was built for the Electrical Machines Laboratory of the National Polytechnic School. The study for the selection of each of the components of the autotransformer is carried out based on theoretical and practical knowledge of electromechanical technology, bibliographic references and with the experimental support of a transformer factory. The autotransformer is built on a ferromagnetic core, with an approximate power of 3 (kVA) between the windings of the autotransformer in which the connections will be made, in addition to using it for open and short circuit tests in transformers, the primary winding it supplies 208 (V) between phases and has a variable output voltage between 0 (V) to 311 (V). Through the calculations based on the dimensions of the core and the voltages that need to be obtained, the three coils are built and subsequently mounted on the columns of the ferromagnetic core of the three-phase autotransformer. Furthermore, a mobile mechanism is implemented to obtain the variable output voltage, by means of three brushes that slide on the windings of the columns of the three-phase autotransformer. Said manual mechanism is based on the translational movement of a linear rheostat, which by varying its position slides the brushes on the turns of the windings and a variable voltage is obtained at the output of the autotransformer terminals.