M.G. Melero
University of Oviedo
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Featured researches published by M.G. Melero.
IEEE Transactions on Industrial Electronics | 2014
Joaquín G. Norniella; José Manuel Bermúdez Cano; Gonzalo Alonso Orcajo; C.H. Rojas; Joaquín Francisco Pedrayes; M.F. Cabanas; M.G. Melero
Virtual flux (VF)-oriented control (VFOC) and VF-based direct power control (DPC) (VF-DPC) have been developed to improve voltage-oriented control and DPC of three-phase active rectifiers. The VF space vector is utilized in transformations between stationary and rotating coordinates in VFOC and in obtaining instantaneous power in VF-DPC. The VF space vector is calculated by integrating the grid voltage space vector. This integration is usually performed using a first-order low-pass (LP) (FOLP) filter, which counteracts the saturation and dc-drift problems associated with pure integrators. However, the dynamics of FOLP filters can be enhanced to a great extent. This paper presents a new, simple, and fast integration algorithm for VF-based control methods. Simulations and experimental tests on a VF-DPC-based system showed that the proposed algorithm leads to rapid recoveries after grid voltage sags occur. Moreover, the performance of VF-DPC under nonideal grids is discussed.
ieee international symposium on diagnostics for electric machines power electronics and drives | 2003
M.G. Melero; M.F. Cabanas; C.H. Rojas; Gonzalo Alonso Orcajo; J. M. Cano; J. Solares
Research has proven that several methods are able to detect shorted turns in the stator winding of operating motors, even in cases in which few turns are involved. One important aspect of these methods is its ability to be applied to condition-based maintenance systems; moreover it has the sensitivity to predict how far the machine is from the end of its useful life. Any information that contributes to establishing an alarm level to predict the remaining life of the motor would be very useful. This paper presents the results of a study carried out on a motor working under a turn to turn short condition. In this condition, interesting results about the behaviour of the motor are obtained and a comparison between the sensitivity of some diagnostic methods to detect shorted turns is made.
IEEE Transactions on Instrumentation and Measurement | 2011
M.F. Cabanas; F. Pedrayes; M.G. Melero; Carlos H. Rojas Garcia; J. M. Cano; Gonzalo Alonso Orcajo; Joaquín G. Norniella
Different techniques have been developed to detect rotor asymmetries in asynchronous motors. Although the reliability and the amount of information these techniques provide about a machines state are indubitable, they still have a serious limitation: failure detection when the motor is driving a variable load torque. In this case, the motor phase currents are modulated by torque oscillations, and the information they contain about the integrity of bars and end rings is altered. This paper reports a new diagnostic method, based on the measurement of the magnetic flux linked by one stator tooth, which allows perfect simple discrimination between the actual presence of rotor asymmetries and the spurious effects caused by the oscillations in the load torque off the driven machine even when it is part of an adjustable speed drive and the motor is operating under a variable supply frequency.
IEEE Transactions on Power Delivery | 2007
M.F. Cabanas; M.G. Melero; F. Pedrayes; C.H. Rojas; Gonzalo Alonso Orcajo; J. M. Cano; J.G. Iglesias
Power transformers figure to be amongst the most costly pieces of equipment used in electrical systems. A major research effort has therefore focused on detecting failures of their insulating systems prior to unexpected machine outage. Although several industrial methods exist for the online and offline monitoring of power transformers, all of them are expensive and complex, and require the use of specific electronic instrumentation. For these reasons, this paper will present online analysis of transformer leakage flux as an efficient alternative procedure for assessing machine integrity and detecting the presence of insulating failures during their earliest stages. A 12-kVA 400-V/400-V power transformer was specifically manufactured for the study. A finite-element model of the machine was designed to obtain the transient distribution of leakage flux lines in the machines transversal section under normal operating conditions and when shorted turns are intentionally produced. Very cheap and simple sensors, based on air-core coils, were built in order to measure the leakage flux of the transformer, and nondestructive tests were also applied to the machine in order to analyze pre and post failure voltages induced in the coils. Results point to the ability to detect very early stages of failure, as well as locating the position of the shorted turn in the transformer windings.
IEEE Transactions on Industrial Electronics | 2011
M.F. Cabanas; F. Pedrayes; C.H. Rojas; M.G. Melero; Joaquín G. Norniella; Gonzalo Alonso Orcajo; J. M. Cano; F. Nuno; David R. Fuentes
The detection of rotor asymmetries in squirrel-cage induction motors has been an important research topic during the last two decades that has given rise to the development of various diagnostic techniques. Despite these techniques being reliable and providing much information about a machines state, they still lack the capability to detect a failure when the motor is driving a machine, producing oscillations in the load torque. If this happens, then the motor phase currents are modulated by torque oscillations and the information that they contain about the integrity of the bars and endrings is no longer correct. Currently, the authors are not aware of a simple and reliable method that exists for the industrial diagnosis of rotor asymmetries in working cage motors under arbitrary load conditions. This paper describes a new diagnostic method and a new portable electronic instrument that are based on the measurement of the magnetic flux linked by one stator tooth, which allows for an optimal simple discrimination between the actual presence of rotor asymmetries and the spurious effects that are caused by the oscillations in the load torque of the driven machine.
ieee international symposium on diagnostics for electric machines power electronics and drives | 2003
Montserrat Cabanas; J.L. Ruiz Gonzalez; J.L.B. Sampayo; M.G. Melero; C.H. Rojas; F. Pedrayes; A. Arguelles; J. Vina
The rotor bars of squirrel cage asynchronous motors are subject to mechanical forces and electrical and thermal transient processes. During the transient operation of the machine, especially during its start up, the high values of current flowing through the cage produce small deformations in bar and end rings. These deformations, combined with the expansions and contractions caused by transient thermal processes and the presence of unavoidable manufacturing defects, lead to rotor bar fatigue. The fatigue starts with small cracks in the junction between rotor bar and endrings and ends with the complete breaking of the bars. In this paper, the causes of fatigue in squirrel cage rotors are studied. By means of several finite element models of low and medium voltage machines the forces applied on the rotor during motor start up are calculated. These forces are used as loads on mechanical models of the rotor bars. By applying the finite element method the stress distribution caused by the forces on the bars is calculated. Once this stress distribution is known fatigue analysis is also performed. The results obtained are then validated by means of destructive tests on real specimens and by the analysis of models including intentional manufacturing defects.
IEEE Transactions on Industrial Electronics | 2015
Joaquín G. Norniella; J. M. Cano; Gonzalo Alonso Orcajo; C.H. Rojas; Joaquín Francisco Pedrayes; M.F. Cabanas; M.G. Melero
Coupling inductors are the most commonly utilized filtering option in grid-connected direct power control (DPC)-based active front-end rectifiers integrated into three-phase adjustable-speed drives (ASDs). Inductor faults, e.g., common interturn short circuits, can drive the whole system to failure. In this paper, a novel strategy is proposed for the early detection of incipient faults in the coupling inductors of the aforementioned ASDs. The proposed method enables a fast identification of the defective phase. The strategy also provides an accurate estimation of the inductance value of the coupling inductors that improves the performance of the DPC method. Simulations and experimental tests demonstrate the validity of this detection and estimation strategy.
IEEE Transactions on Power Delivery | 2012
Gonzalo Alonso Orcajo; José Manuel Bermúdez Cano; M.G. Melero; M.F. Cabanas; C.H. Rojas; Joaquín Francisco Pedrayes; Joaquín G. Norniella
This paper proposes a short-circuit diagnosis tool for electrical low-voltage (LV) distribution networks. The tool relies on analyzing Parks vector representation of the LV phase voltage in the sag produced by a short circuit. Parks vector representation is considered to be an identification mark for the type of short circuit that the installation is exposed to and the phases that it affects. In addition, it shows whether the fault is located in the medium voltage or LV network. The characteristics of the vector representation corresponding to the different types of short circuits are analyzed in this paper. Finally, the relationship between Parks vector representation and the location of the defect is also studied. The results can be used as part of an expert system for the automatic classification of disturbances.
ieee international symposium on diagnostics for electric machines, power electronics and drives | 2007
F. Pedrayes; C.H. Rojas; M.F. Cabanas; M.G. Melero; Gonzalo Alonso Orcajo; J. M. Cano
The growing application of asynchronous motors in industrial processes that require high security and reliability levels has led to the development of multiple methods for early fault detection. The design and verification of these methods imply the use of complex mathematical models that allow the study of the influence produced by the machine operating conditions over the diagnosis procedure. The present paper describes a model for asynchronous motors based on a network of magnetically coupled reluctances. The aim of this model is its application to the study of the typical failures of this type of machine i. e. rotor asymmetries, air gap eccentricity, operation with an open phase etc. The dynamic properties of the model allow the simulation of the spatial evolution of all the motor variables, without neglecting complex phenomena such as magnetic saturation. Time domain analysis of air gap torque, as well as the calculation of current harmonic components is also possible. This initial study is aimed to check the accuracy and computation economy of the model. To do this, the model will be used to analyse a new diagnosis method for rotor fault detection. Simulations of healthy and faulty motors will be presented and the evolution of the machines main electrical and mechanical variables will be obtained.
ieee industry applications society annual meeting | 2005
M.F. Cabanas; F.P. Glez; M.R. Gonalez; M.G. Melero; Gonzalo Alonso Orcajo; J. M. Cano; C.H. Rojas
Different techniques have been developed for the early detection of rotor asymmetries in squirrel cage asynchronous motors over the last two decades. Although their reliability and the amount of information they provide about the a machines state is indubitable, they still have a serious limitation: failure detection when the motor is driving a machine capable of producing oscillations in the load torque. In this case, the motor phase currents are modulated by torque oscillations and the information they contain about the integrity of bars and end rings is hidden or altered. In fact, it can be affirmed that almost all diagnosis methods based on spectral analysis of external electrical variables are affected by this phenomenon. In order to overcome this drawback, attempts have been made to find new procedures leading to new indicators to discriminate between the influence of the load and the rotor failure. Although certain complex systems applied to specific motors for on-line diagnosis have been successfully designed, as far as the authors know, no simple and reliable method exists for industrial diagnosis of rotor asymmetries in working cage motors under arbitrary load conditions. This paper describes a new diagnosis method, based on the measurement of the magnetic flux linked by one stator tooth, which allows perfect, simple discrimination between the actual presence of rotor asymmetries and the spurious effects caused by the oscillations in the load torque of the driven machine.