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%.
Labour Law in a Globalising World
At the opening of the 21st century it is clear that increasing globalisation will remain one of the most important long term influences on the evolution of the international economy and international political structures. The controversial nature of globalisation is self-evident from the increasing intensity of antiglobalisation demonstrations at meetings of international bodies such as the World Trade Organisation. While the actual nature of globalisation, the direction in which it will take the world and the costs and benefits that will result are still contestable, it is clear that the main, and certainly the most effective, drivers are economic. Nations are primarily concerned to set in place structures that promote the free movement of capital including the freedom of multinational companies to locate and relocate around the world, and to promote free trade in goods and services. While non-economic values such as environmental protection and social and labour rights are not excluded from the debates setting these structures in place, they are largely marginal to it. One symbol of this marginalisation is that the ILO, unlike the World Bank, IMF and OECD, does not enjoy observer status at the WTO in spite of the rhetoric of concern for such rights from member states of the Organisation. As McCrudden and Davies explain,1 this exclusion is the result of a major and continuing division between developed and developing countries within the WTO that in the 1990s prevented agreement on any tangible measures in the Marrakesh agreements and that has continued to block subsequent progress. The stark divisions between these groups became even more apparent at the Singapore Ministerial meeting in 1996 when an invitation to the head of the ILO to speak was withdrawn. The only tangible result was a weak statement to the effect that members agreed that labour standards should be upheld but that this should be done through the ILO and not the WTO. The suspicion of developing countries that any link between trade and labour standards will lead to increased protectionism is almost certainly justified. Experience within the WTO to date provides little reason for developing countries to have any great faith in the undertakings of the developed world. Developing countries have seen the promises of movement toward freer trade that might benefit them fade into the distance while at the same time the undertakings they entered into are increasingly used to their disadvantage.2