Applied Mechanics and Materials Vol. 492

Abstract: In this research document, an attempt has been made to come across the effect of double glazing on the efficiency of a solar thermal collector. Experiments were performed on an active solar energy demonstration system (ET 200). Commercial glass pane of 3 mm thick having the same dimensions as that of the apparatus was placed above the collector at a distance of 2 cm. Tests were done with and without the added glass. Experiments were performed for double glazing with two positions of the light meter. In one position, it was placed in the middle of the collector surface. While, in the other, the light meter was placed in the middle of the added glass. To study the effect of double glazing on the performance of the solar collector ET200, the correct position of the light meter was to place it exactly in the middle of the additional pane under the lamp. Double glazing decreased the efficiency of the collector of 15%.

Abstract: Principle aim in standard Selective Harmonic Elimination pulse wide modulation (SHE-PWM) is elimination of low-order harmonics as well as production of desired fundamental component. To accomplish this objective, a set of N switching angles should be determined. In fact, N-1 angles are hired to remove N-1 harmonics from voltage waveform and one angle is allotted to produce the fundamental. This paper presents a solution in order to remove low order harmonics as much as possible. It suggests eliminating next harmonic instead of highest order harmonic in infeasible points. A genetic algorithm is employed to solve the new transcendental equation for finding the switching angles. The proposed method is experimentally applied to a seven-level cascaded H-bridge inverter. The results confirm the validity and effectiveness of the proposed method in extending modulation index range.

Abstract: Because of its high dynamic response speed and acceleration, high rigidity and positioning accuracy, the permanent magnet linear synchronous motor (PMLSM) is able to meet the requirements of high-speed precision CNC machine tools. However, its thermal problems have seriously hampered its development. This paper establishes a PMLSM temperature field model, designs a cooling structure, determines the boundary conditions of the finite element model and conducts computer simulation of the model. The result shows that the designed cooling structure can effectively alleviate the motors thermal problems.

Abstract: This paper presents investigation of the performance and efficiency characteristic of the five-parameter model of photovoltaic module at desert environment. Experimental data under outdoor conditions can be given by the realistic mono-crystalline PV-panel operations in desert climate in the region of Adrar (0.18 W, 27.82 N), Algeria, and was studied. The available technical data over a period of three consecutive days include solar radiation, ambient temperature, open circuit voltage, short circuit current, maximum power point voltage, maximum power point current and the actual electrical output power. Finally, we compared and analyzed the modeled results and the actual experimental measurements. A good agreement between the simulated results and the field data are found.

Abstract: A two floor residential building in Tianjin as the research object was studied in this paper. The software eQUEST was carried out to simulate residential buildings energy consumption, and to explore the annual total energy consumption of the residential building, which was influenced by air conditioning heating modes and the building orientations. The air conditioning and heating system modes used to simulate including the heat pump air conditioning, air conditioner & heat sink and radiant heating & heat sink. The simulated building orientations include east, west, south and north. The transformation of the sunshade direction could be obtained by changing the building orientation. The indoor design temperature in summer was set at 26°C, while winter design temperature was set at 18°C. As the result of the energy consumption simulation study showed that, the annual total energy consumption achieved the minimum when heat pump type air conditioning heating system was adopted. When the effected factors such as air conditioning heating system, indoor heat source condition, window size and some other factors which influenced energy consumption were constant, the simulation results might be found that the building orientation had a small influence on the building energy consumption.

Abstract: Battery state of charge (SOC) can directly reflect its sustainable power supply capacity and health. It is important basis to formulate balance and energy management strategy for battery management system (BMS). In this paper, a second-order RC battery model with factors affected battery characteristics was established based on the Gauss-Hermite quadrature filter (GHQF) theory. According to Kirchhoffs law a state space model was established and the parameters in the model were identified. The GHQF algorithm and model were verified, and comparison was made to an extended Kalman filter (EKF) algorithm on the Matlab and Simulink simulation platform.

Abstract: To obtain a mathematical model capable of predicting the 50% discharge voltage of air-gap under high-altitude conditions, we used the test results of air-gap in high altitude areas to establish the 50% discharge voltage BP neural network model of air-gap under high-altitude conditions. We used the model to forecast the 50% discharge voltage of air-gap under high-altitude conditions. The result shows that the maximum error between forecast voltage and test voltage is 1.42%, which certificates the possibility of using the neural network to build the multidimensional and nonlinear relationship between the environmental factors and discharge voltage. At the same time, we can simulate and analyze the effect of environmental factors on discharge voltage of air-gap with the help of model that we established, analysis showed that there was a positive correlation between the environmental factors, such as temperature, humidity and atmosphere pressure, and discharge voltage of air-gap.

Abstract: In order to optimize the design of UHV substation and reduce its construction investment, it is necessary to take further research of UHV substation air-gap discharge characteristics. In this paper, by using sub-conductor and tower to simulate UHV substation air-gap, lightning and switching impulse discharge characteristics tests of UHV substation are taken in the UHV AC test base of SGCC. The results show that, when the distance of conductor between tower is in range of 4m to 7m, the 50% lightning impulse and switching impulse discharge voltage rise along with the rise of air gap distance. As the air-gap increases, the switching impulse discharge voltage presents the trend of saturation. According to the analysis of test results, we can draw a conclusion that the gap factor of switching impulse discharge can be 1.22 when the minimum distance between conductors and tower is 5~8m.

Abstract: According to IEC60060-1, IEC60060-2 requirements, the large transformer should take impulse voltage test in site. However, this test is not performed in the field for the impulse voltage generator huge and difficult to operate. To solve this problem, IEC60060-3 propose using oscillating impulse voltage for equipment on-site impulse withstand voltage test. Oscillating impulse voltage has higher generation efficiency and close to the actual voltage waveform that electrical equipment bear. For the transformer, the oscillating impulse voltage can generated through inductive method. In order to study the generation of oscillating impulse voltage through inductive method for transformer, the simulation circuit is established using ATP soft and the oscillating switching impulse voltage characteristics is studied in this paper. The result show that the oscillating switching impulse voltage waveform that accordance with IEC requirements can be generated through inductive method for transformer.

Abstract: This paper mainly studies one kind of failure prediction method on electrical connectors at high temperature. One scheme of high temperature reliability test was provided based on the theory of constant stress accelerated life test. The test device was designed; the test data was analyzed. It can be seen that 1) both the absolute change and the relative change of contact resistance are small for each temperature stress; 2) there is a tendency toward slightly higher value of contact resistance for each low temperature stress; 3) the higher the test temperature stress, the larger the value of contact resistance, but the difference in contact resistance is not very big. 4) The data prediction method such as the gray theory model is helpful for rapid failure prediction of electrical connectors at high temperature.