Design and Construction of a Three-phase Transformer for Voltage Control in the Electrical Power Systems Laboratory

Abstract

This paper presents the design and construction of a three-phase dry type transformer of 5 kVA with voltages of 220 V in both primary and secondary windings, with the capacity to vary the transformation ratio by means of fixed taps in a variation range of +/- 5% with steps of 2.5% in the primary winding and with a load tap changer for manual operation and a variation range of +/- 5% with steps of 1% in the secondary winding. The process to size transformer using technical criteria and manufactures experience is detailed. Using the software MATLAB, a graphic interface that allows the user to design three-phase dry-type transformers based on input variables such as power, voltages, type of connection and taps requirement for each winding is developed. The user will obtain the required parameters for the transformer construction, of both core and coil. The program also delivers the equivalent circuit obtained with the design parameters, which are used to build a transformer for the Electrical Power Systems Laboratory, on which electrical tests are performed to corroborate that its operation is adequate and that it is under built norms. From the short circuit and open circuit tests results, the equivalent transformer circuit is obtained.