1,721,053 research outputs found
Flow microcalorimetry in stepwise equilibriums of metal complexes. Reactions of N,N'- and N,N-diethylethylenediamine with hydrogen and copper(II) ions
No full textEnthalpy values assocd. with the stepwise reactions of H+ and Cu2+ with N,N'-diethylethylenediamine [111-74-0] and N,N-diethylethylenediamine [100-36-7] were detd. by flow microcalorimetry at 25° and 0.5M (NaClO4) ionic strength. Combination with reported free energy values gave appropriate entropy values. Comparison with results for ethylenediamine shows that Et substitution causes a decrease in exothermicity of protonation and complexation and leads to a larger entropy change. Generally, reactions with the sym. ligand are more exothermic than those with the asym. one
Design of motor/generator for Flywheel Batteries
Full text linkEnergy storage is an emerging technology that can enable the transition towards renewable-energy-based distributed generation, reducing peak power demand and the time difference between production and use. The energy storage could be implemented both at grid level (concentrated) or at user level (distributed). Chemical batteries represent the de facto standard of storage systems for performance and maturity; however, batteries feature a quite large environmental footprint and use precious raw materials. Mechanical storage technologies could represent a viable alternative to chemical batteries, because of their reduced impacts on the environment and on raw materials. This paper presents the design of a motor/generator for a flywheel energy storage at household level. Three reference machines were compared by means of Finite Element Analysis (FEA): a traditional iron-core surface permanent-magnet (SPM) synchronous machine, a synchronous reluctance machine (SynchRel) and an ironless SPM synchronous machine. Simulation show that the ironless machine is good candidate for distributed energy storage, because of its high efficiency, high discharge duration and low losses. A prototype ironless machine was designed and manufactured. Experiments confirm the simulation results
Influence of MTPA Trajectory Evaluation on Synchronous Machines Performance
No full textInterior permanent magnet machines are characterized by high efficiency over a wide speed range. The optimal performance of these motors can be achieved by implementing the appropriate control strategies: Maximum Torque per Ampere (MTPA), Flux Weakening (FW) and Maximum Torque per Volt (MTPV). The optimal MTPA control trajectories can be found with different methods employing an inductance based model or a flux based model. In principle, the two methods are the equivalent, however, the different numerical method for the evaluation of the control trajectory can lead to slightly different results. Four motors are chosen for the analysis: an IPM machine, a pure reluctance machine, a SPM machine and a reluctance assisted machine. The results obtained from the two the models are compared with 2D-FEA simultion results
Performance Assessment of a Flywheel Energy Storage System for Households
No full textThis paper presents a tool for the optimal sizing of a flywheel for a residential photovoltaic plant. The model is based on an effective control of the power flow and allows to change the value of the parameters involved in the design of the system. Different sizing scenarios are simulated over a period of one year and performance is assessed by means of quantitative indicators on energy savings
Fault Tolerance Analysis of Multiphase Ironless PMSM for Flywheel Batteries
No full textThis paper investigates the performances of an Ironless PMSM with two phase faults: open circuit of a phase and short circuit of a phase. The machine was specifically designed for a Flywheel Energy Storage System (FESS) and is reconfigurable as 3-Phase, 6-Phase and 12-Phase. The machine is meant to be used in domestic applications with a photovoltaic panel and grid connectsion. The performances of each multiphase configuration under faulty and healhty conditions are compared on the basis of annual energy savings, in order to state the optimal configuration for fault toleance
Fault detection of a five-phase permanent-magnet motor
No full textThe paper focuses on the fault detection of a five-phase Permanent-Magnet (PM) machine. This machine has been de- signed for fault tolerant applications, and it is characterised by a mutual inductance equal to zero and a high self inductance, with the purpose to limit the short circuit current. The effects of a limited number of short-circuited turns were investigated by theoretical and Finite Element (FE) analysis, and then a procedure for fault detection has been proposed, focusing on the severity of the fault (i.e. the number of short- circuited turns and the related current)
Improvement on Flux Weakening Control Strategy for Electric Vehicle Applications
Full text linkThis paper proposes an optimized flux weakening (FW) control strategy for interior permanent-magnet synchronous electric motor to address the critical issues that could occur under torque setpoint transition in flux weakening region, due, for example, to an emergency braking. This situation is typical in electric vehicles where the electrical machines operate over a wide speed range to reach high power density and avoid gearboxes. Two modified traditional flux weakening strategies are proposed in this paper to improve torque control quality during high speed torque transition. The proposed modified control strategies were validated both by Matlab/Simulink simulations, modeling the power train of a light vehicle application, and extensive experimental tests on a dedicated test bench
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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