11 research outputs found
Detection of Field Winding Faults in Synchronous Motors via Analysis of Transient Stray Fluxes and Currents
(c) 2021 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.[EN] The detection of rotor failures in synchronous motors is a matter of primordial interest in many industrial sites where these machines are critical assets. However, due to the particular operation of these motors, most conventional techniques relying on steady-state analysis, commonly used in other electric machines, are not applicable to such motors. In this context, it has been recently proven that the analysis of different quantities under transient operation of the motor and, more specifically, under motor starting can provide crucial information for the diagnosis of many faults. This work proposes the time-frequency analysis of stray fluxes and currents to detect field winding faults in synchronous motors. The potential consequences of this fault can be catastrophic for the motor integrity, so that the detection of its presence in its early stages can be of critical importance for the industry. The results included in this paper prove the usefulness of the transient analysis of such non-invasive quantities not only to detect the presence of the field winding fault but also to set a starting point to determine its severity.This work was supported by the Spanish Ministerio de Ciencia Innovación
y Universidades and FEDER program in the framework of the Proyectos de
I+D de Generación de Conocimiento del Programa Estatal de Generación
de Conocimiento y Fortalecimiento Científico y Tecnológico del Sistema
de I+D+i, Subprograma Estatal de Generación de Conocimiento (ref:
PGC2018-095747-B-I00).Tian, P.; Antonino Daviu, JA.; Platero, C.; Dunai, L. (2021). Detection of Field Winding Faults in Synchronous Motors via Analysis of Transient Stray Fluxes and Currents. IEEE Transactions on Energy Conversion. 36(3):2330-2338. https://doi.org/10.1109/TEC.2020.3041643S2330233836
Voltage dip generator for testing wind turbines connected to electrical networks
This paper describes a new voltage dip generator that allows the shape of the time profile of the voltage generated to be configured. The use of this device as a tool to test the fault ride-through capability of wind turbines connected to the electricity grid can provide some remarkable benefits: First, this system offers the possibility of adapting the main features of the time–voltage profile generated (dip depth, dip duration, the ramp slope during the recovery process after clearing fault, etc.) to the specific requirements set forth by the grid operation codes, in accordance with different network electrical systems standards. Second, another remarkable ability of this system is to provide sinusoidal voltage and current wave forms during the overall testing process without the presence of harmonic components. This is made possible by the absence of electronic converters. Finally, the paper includes results and a discussion on the experimental data obtained with the use of a reduced size laboratory prototype that was constructed to validate the operating features of this new device
Dynamical control of correlated states in a square quantum dot
In the limit of low particle density, electrons confined to a quantum dot
form strongly correlated states termed Wigner molecules, in which the Coulomb
interaction causes the electrons to become highly localized in space. By using
an effective model of Hubbard-type to describe these states, we investigate how
an oscillatory electric field can drive the dynamics of a two-electron Wigner
molecule held in a square quantum dot. We find that, for certain combinations
of frequency and strength of the applied field, the tunneling between various
charge configurations can be strongly quenched, and we relate this phenomenon
to the presence of anti-crossings in the Floquet quasi-energy spectrum. We
further obtain simple analytic expressions for the location of these
anti-crossings, which allows the effective parameters for a given quantum dot
to be directly measured in experiment, and suggests the exciting possibility of
using ac-fields to control the time evolution of entangled states in mesoscopic
devices.Comment: Replaced with version to be published in Phys. Rev.
Charge Transport Through Open, Driven Two-Level Systems with Dissipation
We derive a Floquet-like formalism to calculate the stationary average
current through an AC driven double quantum dot in presence of dissipation. The
method allows us to take into account arbitrary coupling strengths both of a
time-dependent field and a bosonic environment. We numerical evaluate a
truncation scheme and compare with analytical, perturbative results such as the
Tien-Gordon formula.Comment: 14 pages, 6 figures. To appear in Phys. Rev.
Low temperature transport in AC-driven Quantum Dots in the Kondo regime
We present a fully nonequilibrium calculation of the low temperature
transport properties of a quantum dot in the Kondo regime when an AC potential
is applied to the gate voltage. We solve a time dependent Anderson model with
finite on-site Coulomb interaction. The interaction self-energy is calculated
up to second order in perturbation theory in the on-site interaction, in the
context of the Keldysh non-equilibrium technique, and the effect of the AC
voltage is taken into account exactly for all ranges of AC frequencies and AC
intensities. The obtained linear conductance and time-averaged density of
states of the quantum dot evolve in a non trivial way as a function of the AC
frequency and AC intensity of the harmonic modulation.Comment: 30 pages,7 figure