INVESTIGATING THE MALFUNCTION OF A HYDRO- GENERATOR'S COOLING-SYSTEM
Electro-magnetic losses within a hydro-generator are sources of heat which heat the generator, and then have to be conducted away. This may, however, cause a temperature rise of the stator bars thus reducing the life-span of the insulation materials. Therefore, any temperature rise of the stator windings is limited. In order to inspect the operation of a cooling-system, several temperature sensors have to be integrated into the stator core in order to measure its temperature, which should not exceed 80 0 C. Temperature measurements performed on a generator showed some deviations from the design temperatures, especially at full-power operation. Thus, an attempt was made to analyse the operation of a cooling-system, and to eventually increase its cooling capacity. It was impossible to perform any complex measurements during the generator’s operation, due to safety reasons. Therefore, our work was limited to 3D CFD simulations using ANSYS CFX 11 solver. The simulations were partly supported by the measurements of some main integral parameters, such as mass-flow rate and pressure drop across the cooling ducts and radiators, as performed during generator idling. The results are presented and discussed in this paper.
Finite element modeling of the temperature distribution in the stator of a synchronous generator
In this paper, we applied the finite element modeling to the stator temperature distribution of a hydroelectric generator. The electrical losses produce a temperature distribution in the stator of a synchronous generator. For the calculation and optimization of the temperature distribution, a full parameterized thermal model of the stator was created using the finite element method. Now it is possible to calculate the thermal effects of different parameter modifications and additionally we can optimize the heat transfer for the stator with variant calculations. The most important bar fitting systems and its thermal efforts are included in this thermal stator model. Our targets are to decrease the expensive and time‐consuming laboratory measurements in the future and improve the accuracy of the standard calculation software. To estimate the accuracy of the finite element model we build an additional laboratory model.
Finite-element modeling of thermal contact resistances and insulation layers in electrical machines
Small transition layers with a significant temperature drop, such as thermal contact resistances and thin insulation layers, are difficult to consider in coupled finite-element thermal/magnetic models of electrical machines. A novel approach using mesh cuts and duplicated nodes at the thin-layer position is derived and discussed here. Results are compared to classical methods involving the use of nonscaled and scaled finite elements. Practical examples demonstrate the features and implementation aspects of the methods used.