Irvin Lopez-Garcia

Experimental and numerical analysis of shorted interlaminations in transformer cores

This paper presents an experimental and numerical analysis regarding shorted electrical steel laminations of core of a small transformer core (120 VA single-phase shell-type transformer). Experimental tests were performed to measure the core losses of the transformer with and without shorted electrical steel laminations. Soft solder was utilized to produce the shorted region in the transformer core. Furthermore, 3-D Finite Element (FE) simulations were carried out to compute the eddy current losses in the core of transformer with shorted electrical steel laminations. The laminations of the core and their insulation were taken into account in the transformer model. Finally, several FE simulations were performed to calculate the eddy current losses for several cases, where the location and size of the shorted lamination region was varied in the core of transformer.

Analytical solution to the diffusion, sorption and decay chain equation in a saturated porous medium between two reservoirs.

The diffusion and distribution coefficients are important parameters in the design of barrier systems used in radioactive repositories. These coefficients can be determined using a two-reservoir configuration, where a saturated porous medium is allocated between two reservoirs filled by stagnant water. One of the reservoirs contains a high concentration of radioisotopes. The goal of this work is to obtain an analytical solution for the concentration of all radioisotopes in the decay chain of a two-reservoir configuration. The analytical solution must be obtained by taking into account the diffusion and sorption processes. Concepts such as overvalued concentration, diffusion and decay factors are employed to this end. It is analytically proven that a factor of the solution is identical for all chains (considering a time scaling factor), if certain parameters do not change. In addition, it is proven that the concentration sensitivity, due to the distribution coefficient variation, depends of the porous medium thickness, which is practically insensitive for small porous medium thicknesses. The analytical solution for the radioisotope concentration is compared with experimental and numerical results available in literature.

Analysis of the power coefficient for a wind generation system

This paper presents an analysis of the conditions and problems that occur when Wind Generation Systems operates in different mode of tracking maximum power. The analysis focuses on the effect of the power coefficient of the wind turbine in the condition of balance of power between the wind generation systems and the electrical network. In the specialized literature there are not enough papers that address this problem. Therefore, in the present paper this problem is solved, showing that there are two desired mechanical speeds for the one particular operating condition of the wind generation systems when this is interacting with the electrical network for each wind speed value.