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Disciplinary area: ELECTROTECHNICS ELECTROMAGNETIC
COMPATIBILITY Research
topics Electromagnetic
interferences produced by static converters Objectives:
Development of a model for predicting effects of power converter parasitic
components on conducted electromagnetic interferences and application to an
inverter-fed ac motor. The research concerns a model for a switching cell that is the basic structure of most power converters. The proposed equivalent circuit takes into account parasitic parameters (inductances and capacitances) and emphasizes their different influence on both differential- and common-mode components of the conducted emission produced by the switching cell. The model, which can be used in the time and frequency domain, was validated experimentally. This
model together with the high-frequency model proposed for windings of an ac
motor (see research “High-frequency circuit modelling for wound components”)
allows one to predict conducted interferences in inverted-fed ac motors, at
both input and output sides of the inverter. The overall circuit model was
verified by experimental tests carried out on a prototype of an ac motor
drive. Modelling
and optimal design of multilayered shielding structures for magnetic fields Objectives:
Development of a methodology for the design and optimization of
multilayered shields for magnetic fields An
analytical model for the calculation of the shielding effectiveness of
magnetic multilayered shields has been developed.
Planar and cylindrical shields in a source of rectilinear and circular
sinusoidal currents have been considered.
The shielding properties of every shield layer are taken into account
by means of a matrix that can be built by grouping transfer relations
between continuous components of the magnetic field at the two interfaces
of the same layer. Such components
are obtained by solving the magnetic diffusion equation in the domain
of interest through appropriate series expansions or transforms.
In such a way, a transfer function that represents the shield in
the spectral domain of the series expansion or transform is obtained.
The transfer function allows one to derive the field components
in the shielded region from those in the source region.
The methodology is applicable in the frequency range in which the
quasi-stationary approximation holds.
Non sinusoidal currents can also be taken into account with the
methodology. An aspect of
the research concerns the optimization, by means of heuristic and nonlinear
programming algorithms, of the number and thickness of the layers that
provide the desired shielding effectiveness with the minimum total thickness
of the shield, composed of materials with known physical characteristics. Radiated
disturbances from switching converters Objectives:
Development of models for predicting radiated electromagnetic field The
research concerns the development of models to predict the radiated
electromagnetic field from switching converters
built on a printed circuit board (PCB) and from a couple of straight
parallel interconnecting conductors that carry high-frequency currents.
The equivalent lumped circuit of the PCB strips is obtained by
assembling lumped-Pi, -L and -T
circuits appropriately. The strip currents and their spectral content are
determined with a circuit simulator. The
magnetic and electrical components of the near field are calculated by
representing the strips with the Hertzian dipole model.
The results are compared with those obtained from numerical codes and
from experimental measurements. The
straight interconnecting conductors carry high-frequency currents (sinusoidal
and periodic nonsinusoidal) and are modeled as two Hertzian dipoles and
as a chain of short electrical dipoles.
Configurations of two parallel cables
at various distances from a ground plane have been considered.
The radiated field is calculated and measured in the far field
region. This last activity has been carried out in collaboration with
researchers of the Electromagnetics Research Group of the University of
Nottingham, United Kingdom. Study
of compact cells for electromagnetic compatibility testing Objectives:
Analysis of design solutions for compact cells for pre-compliance
electromagnetic compatibility testing. The
research concerns the study of possible design solutions of compact cells
for pre-compliance electromagnetic compatibility testing.
In particular, GTEM cells with transverse cross sections other
than the rectangular one have been considered in order to obtain a more
uniform electric field distribution inside the cell volume.
Cubical cells in which the electromagnetic field is radiated from
a broadband antenna are also curremtly studied. Metodi innovativi per il
calcolo e la misura dei campi
magnetici a bassa frequenza L'attività in questo settore ha
portato alla definizione di una procedura di calcolo mediante la quale è
possibile esprimere immediatamente il valore efficace dell’induzione
magnetica in funzione della geometria di un elettrodotto (spaziatura media
tra i conduttori), della corrente di esercizio, e della distanza dal punto
considerato alla linea. Tale procedura, basata sull’applicazione della
teoria delle sequenze ai vettori che descrivono la posizione dei conduttori
di fase rispetto al loro baricentro, consente di calcolare esattamente
l’andamento asintotico del campo magnetico. E' stato mostrato che i valori
calcolati rappresentano quelli effettivi con un errore inferiore al 10%, già
per distanze superiori a circa due/tre volte la spaziatura media tra i
conduttori. Un’ulteriore attività di ricerca ha riguardato lo
studio di un particolare trasduttore di campo magnetico basato
sull’impiego in catena chiusa di sensori magnetici (tipicamente
dispositivi ad effetto Hall o magneto-resistivi). Il principio di
funzionamento, del tutto simile a quello di alcuni trasduttori di corrente,
è basato sull’annullamento del campo in corrispondenza del sensore
mediante una bobina coassiale. La corrente che percorre la bobina è
pilotata dal segnale in tensione fornito dal sensore stesso, opportunamente
amplificato. In questo modo si realizza un sistema in retroazione in grado
di inseguire l’andamento istantaneo del campo magnetico con un segnale in
corrente ad esso proporzionale. Main publications G. Grandi, I. Montanari, U.Reggiani “Effects of Power Converter Parasitic Components on Conducted EMI” Proceedings 12th International Zurich Symposium and Technical Exhibition on EMC (EMC '97), Zurich (CH), February 18-20, 1997, pp.499-504 G.
Grandi, D. Casadei, U. Reggiani “Analysis of Common- and
Differential-Mode HF Current Components in PWM Inverter-Fed AC Motors”
Proceedings IEEE Power Electronics Specialist Conference (PESC’98),
Fukuoka (Japan), May 17-22, 1998, Vol. 2, pp. 1146-1151 L.
Sandrolini, A. Massarini, U. Reggiani “Transform Method for
Low-Frequency Shielding Effectiveness Calculation of Planar Linear
Mutilayered Shields” IEEE Trans. on Magnetics, Vol. 36, No. 6,
November 2000, pp. 3910-3919 L.
Sandrolini, A. Massarini, U. Reggiani “Magnetic Shielding of Long Wires
with Multilayered Cylinders” Proceedings 4th Symposium on
Electromagnetic Compatibility (EMC 2000), Brugge, September 11-15, 2000, pp.
263-267 L.
Sandrolini, A. Massarini, U. Reggiani “Low-Frequency Multilayered
Magnetic Shielding of Circular Loops” 14th International
Zurich Symposium and Technical Exhibition on EMC (EMC 2001), Zurich (CH),
February 20-22, 2001, pp.17-22 A.
Massarini, U. Reggiani, L. Sandrolini “Optimization
of Magnetic Multilayered Shields” Proceedings IEEE 2001 International Symposium on Electromagnetic
Compatibility (EMC 2001), Montreal, Canada, August 13-17, 2001, Vol. 1, pp.161-166 A.
Massarini, U. Reggiani, L. Sandrolini “Shielding Effectiveness of
Multilayred Shields for Magnetic Field Nonsinusoidal Sources”
Proceedings 3rd International Symposium on Electromagnetic
Compatibility, May 21-24, 2002, Beijing, (China), pp.605-608 A.
Massarini, U. Reggiani, L. Sandrolini “Frequency Dependence of Shieding
Effectiveness of Multilayred Magnetic Shields” Proceedings 6th
International Wroclaw Symposium and Exibition on Electromagnetic
Compatibility” June 25-28, Wroclaw, (Poland), 2002, Part. 1, pp. 409-414 A. Massarini, U. Reggiani, L. Sandrolini “Multifrequency Optimization of Multilayered Shields” Proceedings 2002 IEEE International Symposium on Electromagnetic Compatibility (EMC 2002), Minneapolis, Minnesota (USA), Aug. 19-23, 2002, pp.134-139 U.
Reggiani, A. Massarini, L. Sandrolini, M. Ciccotti, X. Liu, D.W.P. Thomas, C. Christopoulos,
“Experimental verification of predicted electro-magnetic field radiated
by straight connecting cables carrying high-frequency currents”
Proceedings IEEE Bologna Power Tech
2003, Bologna (Italy), June 23-26 2003 G.L.
Giuliattini Burbui, A. Massarini, U. Reggiani, L. Sandrolini “Analysis of design solutions for a GTEM cell”
Proceedings V International Symposium on Electromagnetic Compatibility and
Electromagnetic Ecology, St. Petersburg (Russia), September 16-19, 2003, pp.319-322 A. Massarini, U. Reggiani, L. Sandrolini “Radiated emissions from switching converters” Proceedings XIII International Conference on Electromagnetic Disturbances 2003, Bialystok (Poland), September 24-26 2003, pp. 1.4-1,1.4-6 G.
Grandi, A. Santi: “Campi magnetici a bassa frequenza (50 Hz) in
ambiente lavorativo. Gli uffici: individuazione, principali sorgenti e
contromisure”, Le Giornate di Corvara, 7° Convegno di Igiene
Industriale: Elettrosmog etc., Corvara (Italia), 21-23 marzo 2001 G. Grandi: “A Simple Method to Approximate
the Magnetic Field in the Vicinity of Overhead Power Lines”, 5th
IASTED International Conference on Power and Energy Systems, PES 2001,
Tampa, FL, (USA), November 19-22, 2001 G. Grandi, M. Landini: “A
Magnetic Field Transducer
Based on Closed-Loop Operation of Magnetic Sensors”,
IEEE
International Symposium on Industrial Electronics, IEEE-ISIE, L’Aquila (IT),
July 8-11, 2002 |