Selection of the Filter Capacitor for Power Supplies using 1-Phase Diode Rectifier
Diode bridge rectifiers with capacitor-input filters are commonly used at the input stage for power supplies operating from the single phase mains input, as they provide a cost effective solution in the lower power range. However, as there is no simple design rule existing in published literature that gives a reasonable prediction based on real-life conditions, the design of the rectifier-capacitor stage is still a trial and error or based upon experience. This paper presents an approximate (but simple) solution based upon empirical relations, for the prediction of the currents involved and specifies the capacitor, so that it can be selected.
Input-Series Output-Equivalent-Parallel Multi-Inverter System for High-Voltage and High-Power Wireless Power Transfer
This article presents an input-series output-equivalent-parallel (ISOEP) multi-inverter system for high-power wireless power transfer (WPT), where preisolation dc/dc converter is concealed to achieve higher efficiency, and the number of inverter modules is allowed to be flexibly adjusted to satisfy different voltage and power requirements. The main contribution of this article is to analyze the possible factors that may lead to voltage unbalance in the series inverters of the proposed ISOEP multi-inverter topology. At the same time, the dividing capacitor suppression and duty cycle adjustment are adopted to achieve input voltage sharing. To confirm and validate the effectiveness and merit of the proposed WPT system, a prototype consisting of three inverters connected in series was designed, built, and tested. Experiments show that the proposed topology achieved both high-power output and effective input voltage sharing. The maximum output power is 38.37 kW with an efficiency of 89.31%.
Numerical tools applied to power reactor noise analysis
In order to be able to calculate the space- and frequency-dependent neutron noise in real inhomogeneous systems in two-group theory, a code was developed for the calculation of the Green's function (dynamic transfer function) of such systems. This paper reports on the development as well as the test and application of the numerical tools employed. The code that was developed yields the space-dependence of the fluctuations of the neutron flux induced by fluctuating properties of the medium in the two-group diffusion approximation and in a two-dimensional representation of heterogeneous systems, for both critical systems and non-critical systems with an external source. Some applications of these tools to power reactor noise analysis are then described, including the unfolding of the parameters of the noise source from the induced neutron noise, measured at a few discrete locations throughout the core. Other concrete applications concern the study of the space-dependence of the Decay Ratio in Boiling Water Reactors, the noise-based estimation of the Moderator Temperature Coefficient of reactivity in Pressurized Water Reactors, the modeling of the beam- and shell-mode core-barrel vibrations in Pressurized Water Reactors, and the investigation of the validity of the point-kinetic approximation in subcritical systems driven by an external source. In most of these applications, calculations performed using the code are compared with at-power plant measurements. Power reactor noise analysis applications of the above type, i.e. core monitoring without disturbing plant operation, is of particular interest in the framework of the extensive program of power uprates worldwide.