Hysteresis Effect in Operation of Small Wind Power Generators
Mathematical models of operating of horizontal-axis and vertical-axis wind turbines (HAWTs and VAWTs) are considered describing both aerodynamic load and electric generator. This model allows describing steady regimes and transient processes. Using the model, the hysteresis phenomenon is described arising during change of the external resistance in the electric circuit. It is shown that the preferable working regimes of the devices belong to the range of external load where the hysteresis effect appears.
Theoretical and experimental study on the aerodynamic characteristics of a horizontal axis wind turbine
The aerodynamic performance characteristics of a horizontal axis wind turbine (HAWT) were investigated theoretically by an analysis involving a combination of momentum, energy and blade element theory by means of the strip element method, and experimentally by the use of a subscale demonstration model. In this study, two approaches involving combination analysis are made use of, namely, the thrust–torque and the thrust–energy methods. Although both approaches yield identical results, the latter is superior for elucidating the relationship of the kinetic energy of the flows on the blades. Scale experiments are performed with three types of wing aerofoil involving different arrangements with the free stream velocity, U∞=0.8–4.5m/s, and for the open type of wind tunnel with an outlet duct diameter of 0.88m. The experimental and theoretical characteristics of the HAWT using the different three types of the HAWT blades are discussed by reference to the power, torque and thrust coefficients, CP, CT, Cth, and the tip speed ratio λ from the point of view of variable pitch control and fixed pitch stall control methods for the output regulation. The aeronautical characteristics predicted by means of the present numerical approaches, for large units involving large power generation at high efficiency, are discussed, and it is clear how to obtain optimized design parameters that play a significant role in the overall performance.
Testing digital circuits using a Mixed-Signal Automatic Test Equipment
This paper presents the results of parametric testing of digital ICs using a dedicated Mixed Signal Automatic Testing Equipment. Due to the prohibitive price of the ATE equipment and dedicated Device Interface Board (DIB) for digital Integrated Circuits (ICs), a DIB for analog circuits was used to perform the testing. Despite the challenges presented by the experiments, the results prove to be accurate for the performed tests, according to the data sheet of the digital ICs and production test data provided by the manufacturer.