Análisis de desequilibrios en transformadores y máquinas de inducción trifásicos

Identifier:  TDX:2985

Handle: https://hdl.handle.net/20.500.11797/TDX2985

Authors:  García Ríos, Sara

Abstract:
This thesis analyses the effect of the unbalance of the three-phase voltage system in induction machines and in three-phase transformers, by means of unbalance factors. First, a voltage unbalance was characterized by four parameters: type of unbalance (q), positive-sequence voltage (V1), VUF and angle of the complex factor of voltage unbalance. To analyse the effects of unbalances in induction motors, simulations were carried out in two motors, and laboratory tests and simulations in a third motor. It was observed that the unbalance voltage and angle parameters of the CVUF have no influence on the CUF and the TRF. It was also observed that there is a linear trend between the CUF and the TRF versus VUF (for constant values of V1) and that there is a linear tendency between the CUF and the TRF versus V1 (for constant values of VUF). Small voltage unbalances can generate large current unbalances and strong torque ripple. In the laboratory tests, results very close to those obtained by the simulation of motor 3 were obtained. These results were qualitatively equal to those obtained for motors 1 and 2. Unbalances were simulated in a three-phase transformer. It was observed that the voltage unbalance in the primary winding causes unbalance in the secondary voltages and in the primary and secondary currents. Linear trends were also observed among the same factors as those analysed with motors. Finally, a new method for estimating the parameters of the single-phase transformer was developed from load tests using an algorithm that minimized the error of electrical power losses and voltage drop of the secondary winding. More precise parameters of the equivalent Gamma circuit of the single-phase transformer were estimated than those obtained with the open-circuit and short-circuit tests.