1,721,043 research outputs found
Sensitivity analysis of magnetizing inductance in solid rotor induction machine
No full textSolid Rotor Induction Machines (SRIM) gained lot of interesting in the last decades due to the increasing demand for high speed drives. The low manufacturing cost, the rotor robustness and the capability operating in of harsh environments comes along with the drawbacks of difficult design process, necessity of multi-physics analysis and poor power factor. The magnetizing inductance play an important role for what concerns the power factor. In this work the impact of the solid rotor material properties and the air gap of the machine on the magnetizing inductance is investigated
Development and testing aspects of high speed induction machines
No full textThis paper reviews the development and testing aspects of high speed induction machines, through a case study involving a 120 [kW], 25000 [rpm] Induction Machine for a power generation application. In the first part, developments in materials and components including electrical steels and copper alloys are discussed, and their impact on the machines' design and construction is investigated. In the second part of this paper, the testing aspects and test results of the prototyped Induction Machines are reported
Sensitivity analysis of rotor parameters in solid rotor induction machine
No full textSolid Rotor Induction Machines (SRIM) gained lot of interesting in the last decades due to the increasing demand for high speed drives. The low manufacturing cost, the rotor robustness and the capability operating in of harsh environments comes along with the drawbacks of difficult design process, necessity of multi-physics analysis and poor power factor. The single phase lumped parameter equivalent circuit is widely adopted for design and analysis purposes. The impact of the solid rotor material properties as saturation flux density, relative permeability and electrical resistivity are discussed in this work for what concerns mainly the rotor resistance and rotor leakage inductance. Finite Element simulations are performed to determine the equivalent circuit parameters dependencies on the solid material selected for the rotor structure
Thermal-Electromagnetic Analysis of Solid Rotor Induction Machine
No full textThe increasing demand for high speed, direct drive systems is driving a significant research effort on high speed electrical machines. Thermal management becomes a significant aspect to deal with as power loss per cooling surface area reduces as speed increases. Solid rotor induction machines are often considered at the high end of the speed spectrum as they offer a mechanically robust rotor structure. The current density distribution within their rotor structure typically results in high rotor losses and a significant portion of the total machine losses. In such machines the current distribution in the rotor itself is highly dependent on the rotor resistance and hence on the rotor temperature distribution. This paper will detail an effective model coupling both the electromagnetic and thermal domains to simulate operation of solid rotor induction machines
The BPS limit of rotating AdS black hole thermodynamics
Full text linkWe consider rotating, electrically charged, supersymmetric AdS black holes in four, five, six and seven dimensions, and provide a derivation of the respective extremization principles stating that the Bekenstein-Hawking entropy is the Legendre transform of a homogeneous function of chemical potentials, subject to a complex constraint. Extending a recently proposed BPS limit, we start from finite temperature and reach extremality following a supersymmetric trajectory in the space of complexified solutions. We show that the entropy function is the supergravity on-shell action in this limit. Chemical potentials satisfying the extremization equations also emerge from the complexified solution
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
Fast Analytical-Numerical Modelling of Rotor Eccentricity for Radial Active Magnetic Bearing
No full textRadial Active Magnetic Bearings (R-AMBs) have become an attractive alternative to other type of bearings in an increasing spectrum of applications. Optimum design and fine control strategies play an important role in the overall performance of such type of electro-magneto-mechanical devices. In order to achieve a quick yet accurate estimation of the main parameters that affect the behaviour of R-AMBs, a numerical-analytical model is here proposed. The analytical expression are firstly introduced. The model is implemented in a digital environment and used to numerically evaluate the inductance matrix and its variation with respect the rotor eccentricity coordinates. The results are validated through FEM and final considerations for both electromagnetic design and control design can be drawn
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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