International and National Journals
O. Bottauscio, M. Chiampi, A. Manzin
Transient analysis of thin layers for the magnetic field shielding
IEEE Transactions on Magnetics, Vol. 42, no. 4, pp. 871-874, 2006.
The thin layer technique is extended to the analysis of passive shields for the mitigation of pulsed magnetic fields. The interface conditions between the two sides of the shell are determined by discretizing the diffusion equation along the shell thickness. The proposed formulation is validated by comparison with a standard hybrid finite element-boundary element method solution. Finally, some applications on problems related to industrial and laboratory environments are presented.
O. Bottauscio, P.P. Capra, F. Durbiano, A. Manzin
Modeling of cells for electrolytic conductivity measurements
IEEE Transactions on Magnetics, Vol. 42, no. 4, pp. 1423-1426, 2006.
This paper deals with the modeling of cells for electrolytic conductivity measurements. The characteristics of these equipments have to be accurately determined in order to perform reliable measurements, traceable to the units of the International System (SI). A numerical three-dimensional model, based on the boundary element method, is developed and applied here to different cell geometries for evaluating the electric/current field inside the solution and, consequently, the cell impedance.
G. Crotti, M. Chiampi, D. Giordano
Estimation of stray parameters of coils for reference magnetic field generation
IEEE Transactions on Magnetics, Vol. 42, no. 4, pp. 1439-1442, 2006.
The paper focuses on the numerical computation of the stray parameters of coils for reference magnetic field generation. The coils are modeled by the multiconductor transmission line approach, where the inter-turn capacitances are evaluated through a hybrid finite element/boundary element method. The influence of the turn arrangement and the support dielectric characteristics is investigated with the aim of evaluating the system performance with the increase of frequency.
M. Zucca, G. Crotti, O. Bottauscio, X. Li, M. Di Pardo, M. Chiampi
3D modeling for magnetic field shielding in a high electric power process
Journal of Applied Physics, Vol. 99, 08P503-1/3, 2006.
A modeling approach is used to investigate the shielding efficiency of ferromagnetic shields for the reduction of magnetic fields produced by industrial high electric power devices. Different ferromagnetic materials and their behavior in combination with pure conductive screens is analyzed and quantified. A comparison with experimental results performed in proximity to an actual device is finally reported to validate the modeling analysis.
O. Bottauscio, M. Chiampi, A. Manzin
Element-free Galerkin method in eddy current problems with ferromagnetic media
IEEE Transactions on Magnetics, Vol. 42, no. 5, pp. 1577-1584, 2006.
This paper focuses on the application of the element-free Galerkin method to the solution of eddy-current problems in ferromagnetic media. The method is first validated by comparison with an analytical linear solution, discussing the role of the numerical parameters that affect the solution accuracy. Then, the application is extended to nonlinear and hysteretic media, adopting the fixed point iterative scheme and the classical Preisach model. The proposed method is also tailored for nonhomogenous structures. The merits and drawbacks with respect to a finite-element approach are discussed for all the considered problems.
C. Beatrice, O. Bottauscio, M. Chiampi, F. Fiorillo, A. Manzin
Magnetic loss analysis in Mn-Zn ferrite cores
Journal of Magnetism and Magnetic Materials, Vol. 304, pp. e740-e745, 2006.
Magnetic losses have been measured and analyzed upon a wide range of frequencies in Mn-Zn ferrite ring cores. Exploiting the concept of loss separation and modeling the conductivity process in the heterogeneous material as a function of frequency, the role of the different energy dissipation mechanisms has been elucidated. It is shown, in particular, that eddy current effects can be appreciated, in standard materials and cores, only on approaching and overcoming the MHz range. The basic mechanism for hysteresis and low-frequency losses is therefore identified with the domain wall relaxation engendered by spin damping processes. Resonant absorption of energy associated with magnetization rotation is in turn deemed to chiefly contribute to the loss upon the practical range of frequencies going from a few 104 Hz to a few MHz.
O. Bottauscio, M. Chiampi
Hysteresis and eddy currents effects in ferroresonant LCR circuits
Journal of Magnetism and Magnetic Materials, Vol. 304, pp. e801-e803, 2006.
Ferroresonance conditions are analyzed in a LCR circuit including nonlinear inductor. The effect of the ferromagnetic model (single valued curve, static hysteresis, dynamic hysteresis) and of the eddy currents are deepened by means of a coupled circuit-field equations. It is found that all the dissipative effects reduce or avoid ferroresonance and, in this paper, this influence is quantified and discussed, making reference to different material models.
O. Bottauscio, M. Chiampi, A. Manzin
Eddy Current problems in nonlinear media by the element-free Galerkin method
Journal of Magnetism and Magnetic Materials, Vol. 304, pp. e823-e825, 2006.
The element-free Galerkin method is applied to the solution of eddy current problems in nonlinear and hysteretic media. The method is first validated by comparison with an analytical linear solution and successively applied to different nonlinear problems discussing merits and drawbacks with respect to a Finite Element approach.
O. Bottauscio, M. Chiampi, A. Manzin
Influence of constitutive parameters in soft ferrites: a modeling analysis by homogenization technique
Journal of Magnetism and Magnetic Materials, Vol. 304, pp. e746-e748, 2006.
A numerical procedure, based on a mathematical homogenization technique, is applied to investigate the influence of microstructure on the impedance and classical loss behavior versus frequency in soft ferrites. It is found that classical losses result to be mainly affected by grain resistivity and by grain boundary thickness.
O. Bottauscio, M. Chiampi, P.E. Roccato, M. Zucca
1-100 kHz magnetic shielding efficiency by metallic sheets: modeling and experiment by a laboratory test bed
IEEE Transactions on Magnetics, Vol. 42, no. 10, pp. 3533-3535, 2006.
The purpose of this paper is to investigate the shielding mechanisms of low-cost metallic sheets in a frequency range from 1 to 100 kHz. The analysis is performed through a specific experimental test-bed, using a numerical model for better understanding and predicting the shield behavior and efficiency.
O. Bottauscio, M. Chiampi, A. Manzin
Nonlinear ferromagnetic shield modeling by the thin-shell approximation
IEEE Transactions on Magnetics, Vol. 42, no. 10, pp. 3144-3146, 2006.
This paper proposes an extension of the thin-shell formulation, based on the Fixed Point iterative scheme, to the analysis of nonlinear and hysteretic ferromagnetic shields. The method is validated by a detailed comparison with a standard hybrid Finite Element - Boundary Element technique.
A. Bellini, O. Bottauscio, M. Chiampi, C. Tassoni, M. Zucca
Induction motor rotor quantities at load conditions: finite Element analysis and experimental validation
IEEE Transactions on Magnetics, Vol. 42, no. 10, pp. 3476-3478, 2006.
The knowledge of induction motor rotor quantities is essential to precisely define the machine energy efficiency and it is useful for the implementation of diagnostic techniques. This paper aims at investigating rotor quantities measured on an actual device and computed by a model reproducing the machine. Results were compared and discussed.
O. Bottauscio, F. Casaro, M. Chiampi, S. Giors, C. Maccarrone, M. Zucca
High-speed drag-cup induction motors for turbo-molecular pumps applications
IEEE Transactions on Magnetics, Vol. 42, no. 10, pp. 3449-3451, 2006.
This paper deals with the performances of high-speed induction motors for turbo-molecular pump applications. A comparison between squirrel-cage and drag-cup motors is performed by a modeling and experimental analysis. Possible improvements to increase the drag-cup motor efficiency and to reduce rotor losses are investigated acting on the rotor design.
O. Bottauscio, V. Chiadò Piat, M. Chiampi, M. Codegone, A. Manzin
Electromagnetic phenomena in heterogeneous media: effective properties and local behavior
Journal of Applied Physics, Vol. 100, 044902-1/8, 2006.
The purpose of this paper is the use of a mathematical homogenization approach based on the multiple scale expansion theory for modeling the electromagnetic phenomena arising in heterogeneous media under an imposed magnetic flux. The attention is focused on the analysis and discussion of the merits and limits of this theoretical approach in reproducing not only the effective macroscopic properties but also the local behavior, under a wide frequency range and considering different constitutive and geometrical parameters. The results show that the proposed method is able to predict local and integral physical quantities, ranging from a substantially global behavior in the whole media to significantly localized effects determined by the microscopic structure.
P. Sergeant, M. Zucca, L. Dupré, P. E. Roccato
Magnetic shielding of a cylindrical shield in nonlinear hysteretic materials
IEEE Transactions on Magnetics, Vol. 42, no. 10, pp. 3189 - 3191, 2006.
The magnetic shielding efficiency of a cylindrical shield is studied starting from the experimentally determined hysteresis loops of the nonlinear shielding material. The magnetic transfer relation model is used in the frequency domain. This analytical model can be evaluated very fast, but works only for linear material. Therefore, the nonlinear shield is divided into a number of linear sublayers with constant complex permeability, which is modelled by an analytical complex function, fitted from the experimental hysteresis loops. The shielding factors are calculated by the analytical model as a function of the imposed field amplitude. They are validated by a finite element model and compared with measured shielding factors of cylindrical tubes. The correspondence is good for the three considered shields: a shield in aluminium (shielding by induced currents), a shield in Fe-Si steel (mainly shielding by flux shunting) and a multilayered shield in aluminium and Fe-Si steel.
Conference Proceedings
M. Borsero, G. Vizio, B. Audone, V. Ormezzano
The problem of traceability for EMC and environmental electromagnetic fields measuring equipment
EMC Europe 2006, pp. 185-190, Barcelona (Spain), September 2006 (poster session).
In the area of electromagnetic compatibility measurements it is not easy to find accredited laboratories capable of performing suitable calibrations for many pieces of equipment. Moreover, in this field test-station checks are sometimes necessary too. The paper reviews a document on this subject, born from the cooperation of the national metrological institute and the Italian accreditation body for testing laboratories (SINAL). The purpose of the document is to provide testing laboratories interested in getting an accreditation in the EMC area with guidelines regarding calibration and check procedures for instruments used in EMC measurements. Furthermore, it gives some practical indications on when in-house calibrations are allowed or EA (European co-operation for Accreditation) accredited calibrations are recommended, on the instrument parameters that need to be verified and finally on the recommended calibration intervals.
G. Crotti, M. Zucca
Experimental evaluation of earth currents generated by a DC traction network
EMC Europe 2006, pp. 783-787, Barcelona (Spain), September 2006 (poster session).
Earth currents generated by a DC traction network, causing interference with the functioning of sensitive apparatuses and plants located in the surrounding area, are experimentally investigated. Measurements of the potential variation of a lighting plant earthing network are made at the same time with significant railway load variations. The presence and the amount of earth current with respect to that flowing in the overhead line are experimentally evaluated through measurements of voltage drops across rail sections, when a defined current is imposed on the supply line for a short time.
P. Mazza, N. Kuljaca, G. Crotti, A. Sardi, G. De Donà, U. Brandm, A. Anderssons
On-site live verification of HV instrument transformer accuracy
2006 CIGRÉ Session, Paris (France), August 2006 (on cd rom).
The availability of a tools aimed to asses instrument transformers accuracy on-site are highly desirable, since reliable and precise energy metering is of essence to achieve electricity market correctness and transparency. CTs and VTs can be verified against a reference measuring system, which consists of current and voltage transducers, optical data links and a data acquisition system. This new reference measurement system includes a high precision split core Rogowski coil as a current transducer, a precision low inductance resistive-capacitive voltage divider and a high precision Optically Powered Data Link (OPDL). The mechanical design is relatively light and can easily be moved and repositioned. Metrological procedures include laboratory characterisation of the reference measurement systems. These procedures take into account the different operating conditions, evaluation of the measurement uncertainty associated with the on-site operation, definition and adaptation of suitable measurement procedures. Traceability of the measuring system to the national standards is assured through an unbroken chain of calibrations.
P. Mazza, N. Kuljaca, G. Crotti, A. Sardi, G. De Donà, U. Brandm, A. Anderssons
Live installation of HV equipment for instrument accuracy check
8th Live Working Conference ICOLIM 2006, Session S3.10, Prague (Czech Republic), June 2006 (on cd rom).
Live working is not useful for line or substation maintenance activities only, although this is the more common application: other practices are made possible too, such as measurement devices installation. Besides well known donuts for line temperature measurement, other new, important applications are currently being developed, such as the one here presented: the live working installation of a reference measuring system for on-site accuracy check of instrument transformers. The reference system is composed by live-installable transducers for voltage and current (a capacitive-resistive voltage divider and a split-core, openable Rogowski coil), optical data transmission and a data acquisition and analysis system. The reference voltage divider can be installed using a hand operated "distance" technique, by means of a copper plait inserted in a reel connected to a short-circuit device, while the Rogowski coil can be positioned with a bare-hand technique. The innovative methodology was set up and successfully experimented in Italian Rondissone HV substation in the frame of a research project led by CESI S.p.A. Innovation is not related to intervention typology, common to a lot of live working activities, but to to installed measurement apparatus features, allowing to avoid service interruption during insertion operations.
A. Cherbaucich, N. Kuljaca, P. Mazza, G. Crotti, A. Sardi, G. de Donà
Verifica in campo e sotto tensione dei trasduttori di misura AT
Atti del XXIII Congresso Nazionale "Gruppo Misure Elettriche ed Elettroniche (GMEE 2006)", pp. 395-403, L'Aquila (Italia), settembre 2006.
La memoria descrive le metodologie sviluppate per la verifica, in campo e sotto tensione, dell'accuratezza dei trasduttori di misura utilizzati in esercizio nelle reti AT, nonché i primi risultati ottenuti nel corso della sperimentazione, in laboratorio e in campo, delle apparecchiature realizzate allo scopo. Questo lavoro è stato finanziato con il Fondo Ricerca di Sistema per il settore elettrico nazionale istituito con Decreto Ministero dell'Industria DM 26/1/2000.
A. Trinchero, C. Catalano, E. Ghione, C. Arnelli, I. Borghi, P. Campana, M. Borsero, G. Vizio, S. Adda, L. Anglesio, A. Benedetto, S. Trinchero, G. Cortiana, M. Marabelli
Verifica sperimentale delle prestazioni di misura di strumenti, sensori e centraline di monitoraggio, in presenza di segnali a radiofrequenza digitali e a larga banda
Atti del 3º Convegno Nazionale "Controllo ambientale degli agenti fisici: dal monitoraggio alle azioni di risanamento e bonifica", Biella (Italia), giugno 2006 (on cd rom).
Questo lavoro illustra i risultati ottenuti durante la caratterizzazione della risposta di sensori di campo a larga banda, in presenza di segnali radio modulati secondo standard IEEE 802.11x (Wi-Fi) e IEEE 802.16x (Wi-Max). L'attivita' e' stata svolta dai componenti di un gruppo di lavoro interdisciplinare istituito dal Sotto-Comitato 106B del CEI e incaricato di predisporre un metodo per la misura dei segnali a larghissima banda. E' stata condotta un' indagine di tipo sperimentale, valutando le prestazioni di un grande numero di sensori, strumenti di misura e centraline di monitoraggio in presenza di segnali digitali. Lo studio e' stato effettuato variando frequenza, potenza, larghezza di banda e profondità di modulazione, in modo tale da ottenere un'analisi non legata ad una particolare tipologia di segnali attualmente in uso, ma utilizzabile come riferimento anche per segnali di futura introduzione.
A. Agosto, G. Crotti, D. Giordano
Misura di campi magnetici a bassa e media frequenza
Atti del 3º Convegno Nazionale "Controllo ambientale degli agenti fisici: dal monitoraggio alle azioni di risanamento e bonifica", Biella (Italia), giugno 2006 (on cd rom).
Nel lavoro viene descritto il nuovo sistema di generazione di campi magnetici campione (da 1 kHz a 100 kHz) realizzato presso l'I.N.RI.M (ex IEN) di Torino, che permette la taratura e la verifica della strumentazione utilizzata in particolare per le misure di campi alternati a frequenze diverse da quella di rete e di campi magnetici pulsati o con ampio contenuto spettrale. Utilizzando il sistema realizzato viene analizzato il comportamento nel dominio della frequenza di alcuni strumenti di misura disponibili in commercio. Inoltre, con riferimento alle misure in campo e tenuto conto delle indicazioni ICNIRP riguardanti la protezione della popolazione e dei lavoratori dall'esposizione ai campi elettromagnetici, recepite in sede di Comunità Europea, sono analizzate e discusse le prestazioni di misuratori di campo in grado di elaborare il risultato di misura e di presentarlo direttamente in relazione alla conformità ai livelli di riferimento (o valori di azione) prescritti per la popolazione e i lavoratori dai suddetti organismi.
M. Zucca, P. Roccato, M. Chiampi, O. Bottauscio
Caratteristiche della mitigazione passiva del campo magnetico nella gamma di frequenza 1 kHz - 100 kHz
Atti del 3º Convegno Nazionale "Controllo ambientale degli agenti fisici: dal monitoraggio alle azioni di risanamento e bonifica", Biella (Italia), giugno 2006 (on cd rom).
Lo scopo dello studio, focalizzato sulla gamma di frequenza tra 1 kHz e 100 kHz, è lo studio dei meccanismi che determinano la mitigazione del campo magnetico mediante l'utilizzo di lastre magnetico-conduttive, comunemente reperibili sul mercato. I risultati di un'analisi sperimentale, eseguita con un setup di laboratorio specificatamente realizzato per tale studio, sono stati confrontati con le soluzioni di un modello numerico al fine di ottenere una migliore comprensione dei fenomeni fisici che sono alla base della mitigazione e al fine di validare i modelli numerici previsionali dell'efficienza schermante.