On-site measurement of load and no-load losses of GSU transformer
Present development and production of power transformers with lower losses in addition to replacement of outdated transformers assume regular measurement of losses in both load and no-load regime. These measurements are very demanding especially in the case of on-situ measurements. The complexity of the measurements grows with the size of transformer. This paper presents one typical test of losses measuring in load and no-load regime of power transformer with nominal power of 40 MVA in HPP Perucica.
Limitations of Grundy & Kabaila ’ s simplified method and its repercussion 1 on the safety and serviceability of successively shored building structures 2
10 One of the most critical stages for a structure’s safety is precisely its construction process, 11 and this problem is even more acute in buildings with reinforced concrete structures. These 12 structures are usually built by shoring successive floors, so that the most recently poured floor 13 rests on the lower floors by means of shores. It is therefore vitally important to have calculation 14 tools available to estimate the loads to which the shores and slabs are subjected in each stage 15 of construction. A number of calculation methods have been proposed to date, of which the 16 one proposed by Grundy & Kabaila in 1963 is the best known and most frequently used. This 17 paper analyses the limitations of Grundy & Kabaila’s method by means of a parametric study 18 of FEM simulations, which found a large number of situations in which this method presented 19 unsafe results as regards the estimated loads on the slabs. In many situations, therefore, 20 applying this method could gravely affect a building’s in-service behavior and durability. The 21 paper’s final objectives are to make the reader aware of the limitations of Grundy & Kabaila’s 22 method and the need to use the more refined methods now available to estimate the loads on 23 shores and slabs in reinforced concrete buildings under construction. 24
Effects of reservoir volume on performance of pulse tube cooler.
A pulse tube cooler has the advantages of long-life and low-vibration over conventional cryocoolers such as G-M and Stirling coolers because of the absence of moving parts at low temperature. On the other hand, the combination of a reservoir and orifice is indispensable to optimize the performance of pulse tube coolers. In order to make the pulse tube cooler compact for practical applications, the volume of reservoir should be minimized. This paper analyzes the effects of the reservoir volume on the thermodynamic performance of various components in a simple orifice and a double-inlet pulse tube cooler by combining a linearized model with a thermodynamic analysis. Expressions of entropy production for those components are presented. The results show that the reservoir volume has a significant influence on the entropy production in the various components when the reservoir to pulse tube volume ratio is smaller than about 5. The ratio is important to determine the minimum reservoir volume for a pulse tube cooler. Optimum settings for a double-inlet pulse tube cooler are also discussed.