A Cost-Effective Design Approach for Permanent Magnet Brushless Machines

Small-power electric machines that use permanent magnets for providing field excitation are becoming increasingly attractive for use in various industrial applications, including those with high-torque requirements andspace limitations. There exists a wide range of designs based on different topologies and different types of magnetic materials. The cost-effectiveness of permanent magnet (PM) machine designs couldbe affected to a great extent by the choice of the magnet material, the overall size of the machine, and the selection of the most appropriate materials, taking into consideration their relative costs and properties. This paper presents an analytical approach to design a surface-magnet electric machine with optimum use of materials on cost basis. Influence of major design parameters is examined, as well using sensitivity analysis. The results show that the optimum split ratio is inversely related to the remanence of the chosen magnet. Also, the impact of the core saturation level on the overall machine cost is investigated.     

Dual-Mechanism Quenched Fluorogenic Probe Provides Selective and Rapid Detection of Cathepsin L Activity**

Cathepsin L (CTL) is a cysteine protease demonstrating upregulated activity in many disease states. Overlapping substrate specificity makes selective detection of CTL activity difficult to parse from that of its close homologue CTV and the ubiquitous CTB. Current probes of CTL activity have limited applications due to either poor contrast or extra assay steps required to achieve selectivity. We have developed a fluorogenic probe, CTLAP, that displays good selectivity for CTL over CTB and CTV while exhibiting low background fluorescence attributed to dual quenching mechanisms. CTLAP achieves optimum CTL selectivity in the first 10 min of incubation, thus suggesting that it is amenable for rapid detection of CTL, even in the presence of competing cathepsins.     

Long-term testing of a low-loss 800 kV PPLP insulated SCFF cable

This paper describes the dielectric and accelerated aging tests on an 800 kV AC polypropylene laminated paper (PPLP) insulated low-loss SCFF cable prototype. The test program was developed to validate the PPLP technology for future Hydro-Quebec 765 kV St-Lawrence under-river crossings. The paper reports on the cable and accessories characteristics, the test line construction, the test program, and the main results obtained. The successfully completed program has shown the overall very good performance of the cable and its accessories     

An adaptive utility interactive photovoltaic system based on a flexible switch matrix to optimize performance in real-time

Reconfigurable architectures are of great interest to system designers to improve the system’s operation and efficiency. In this paper, we propose an adaptive utility interactive photovoltaic (PV) system based on a novel Flexible Switch array Matrix topology. This proposed system maximizes the generated power in real-time in response to operational conditions such as shading, soiling, mismatches, and module failure among others. The proposed system is a compromise in the utilization of power conditioning equipment to maximize energy capture and system efficiency. Simulation results demonstrate an average 13% improvement in efficiency when compared with the central inverter topology performance. A prototype system has been designed and tested. The experimental results validate the proposed topology and its benefits for a wide range of applications.     

Evaluation of the Hall parameter of electrolyte solutions in thermosyphonic MHD flow

The objective of this work is to determine experimentally the Hall parameter of electrolyte solutions using a closed loop thermosyphonic magnetohydrodynamic flow. The upper and lower parts of the loop, which represent the heat sink and heat source of the system respectively, are constructed from copper pipe coated with varnish on the inside surface. The middle region, connecting the upper and lower parts of the loop, is made from plastic vertical pipes, with segmented copper electrodes placed vertically opposite to each other on each side of the loop plastic walls and connected as a Hall generator to measure the open circuit voltage. A transverse magnetic field is imposed in the middle non-conducting plastic-wall region by a set of permanent magnets. The magnets provide a magnetic field strength of up to 0.225 T, whereas the driving temperature difference between the hot and cold portion of the loop ranges from 10 to 80 °C. Measurements of the induced flow rate and induced open circuit voltage are reported as a function of driving temperature difference and magnetic field strength.The analytical one-dimensional model of Ghaddar [Int. J. Heat Mass Transfer 41 (8-9) (1998) 1075] is extended to account for the electrode design and the Hall effect pertinent to electrolyte solutions. The open circuit voltage is related to the driving temperature difference, flow characteristic, magnetic field strength, electrolyte electric properties and electrode design. The developed 1-D model and the measured open circuit voltage are used to evaluate the Hall parameter (ωτ), which is a property of the fluid of the electrolyte liquid. It is found that ωτ can be as large as 100 for electrolytes and causes a significant loss in power output at the electrodes due to electron drift in the fluid leading to generation of current in an axial direction at the expense of the current flowing in the transverse direction between the electrodes.     

Transferring Power Sectors from Aging Utilities into Smart Grids—The Case of Lebanon

The substantial increases in the energy consumption during the second half of the last century have amplified the use of fossil fuels in various economic sectors, mainly the power sector. Also, the low-efficient technologies still adopted in many countries have mounted the losses associated with various energy conversion processes to substantial levels. Tasks and challenges associated with transferring power sectors from energy-wasting utilities into advanced smart grid-based utilities are discussed in this article. To transfer the Lebanese dilapidated and aging electrical power sector into a modern economically profitable sector, adopted two major projects have been adopted: the Lebanese Electrical Network Control Center and the Advanced Metering Infrastructure. This article explains the outcomes and impacts of the major components of these two projects; it article also discusses the problems encountered during the implementation process of the Lebanese Electrical Network Control Center, where several original software packages have been modified by the research team to properly integrate the Lebanese Electrical Network Control Center with the aging Lebanese power sector. Finally, the article describes the controlled design project, which also has been implemented as part of the Lebanese Electrical Network Control Center project and highlights problems associated with upgrading the high-voltage transmission lines.     

Numerical study of parameters affecting the temperature distribution in a disc-type transformer winding

In this paper, the effect of the numerical model, mass flow rate and inlet boundary conditions on the flow and temperature distributions in a disc-type transformer winding is investigated using a commercial CFD code. For the winding under investigation, it was found that the results obtained with simplified models are quite different from those computed with a complete Conjugate Heat Transfer model that considers the individual copper conductors forming the disc. The temperature profile (uniform or non-uniform) specified at the inlet of the winding is another parameter having a significant influence on the hot-spot temperature prediction and the paper stresses that a refined model is needed to capture this effect. The numerical results also indicate that a higher flow rate gives a more efficient cooling of the winding since the temperature distribution is more uniform and the hot-spot factor is reduced.     

Assessment of energy efficiency measures: The case of the Lebanese energy sector

This paper examines in detail the electric energy sector in Lebanon on the levels of both the supply and end‐use sides. The aim of the study is to assess the feasibility of implementing some energy efficiency options in the country. For this purpose, baseline scenarios will be first developed to examine the effects of government policies with regard to the energy balance, and then energy efficiency scenarios will be built for the residential, commercial and industrial sectors. Feasible options will be highlighted and recommendations to remove barriers hindering the fast penetration of energy efficiency programmes in the Lebanese energy sector will be provided. Throughout the analysis, uncertainties related to factors such as discount rates, demand growth and technology penetration rates will be treated by defining lower and upper bounds on their variations, and will be accommodated through scenario‐type analysis. Copyright © 2001 John Wiley & Sons, Ltd.     

Solar heating—Ventilating system using a solar chimney

This paper presents the theoretical and experimental studies of a modified Trombe wall collector. As it is well known, the Trombe wall collector is a self convective flow solar air heating collector with thermal energy stored in the mass of the wall. One of the major problems of this system is the excessive heat losses from the wall, which is insulated from outside with only a double window. The objective of this study was to investigate the possibilities of reducing these excessive heat losses by separating the heat collector panel from the heat storage mass. Thus, a collector panel with a minimum thermal inertia is used to collect the solar energy which is transferred to the inside of the house for storage. During the night time operation, the well insulated collector panel with no thermal inertia serves as a thermal buffer, to reduce the heat losses from the house. An analytical study has been carried out and the results have been verified with the experimantal studies obtained at the Solab, the Solar Research House of Ecole Polytechnique.