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Experimental High-Frequency Parameter Identification of AC Electrical Motors
Full text linkIn order to predict conducted electromagnetic interference in inverter-motor drive systems, high-frequency (HF) motor models are requested and the involved parameters have to be available. In previous studies, the authors have presented an accurate HF model for induction motors and they have defined the procedures to identify the model parameters. In this paper, these results are extended to several types and sizes of industrial ac motors such as induction, synchronous reluctance (without interior permanent magnets), and brushless motors. The model parameter-identification procedure has been improved, and it is based on a least-squares data fitting applied to the measured magnitude and phase-frequency-response curves of the phase-to-ground and the phase-to-neutral impedances. The aim of this paper is to provide quick indications to select the suitable values of the HF model parameters, with reference to the size and type of the ac motor, to evaluate the HF voltage and current components in inverted-fed ac motor system
A recursive algorithm to resolve the skin effects in rotorbars of squirrel cage induction motor
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A simplified method for the iron losses prediction in soft magnetic materials with arbitrary voltage supply
No full textThe aim of this work is to propose a new approach for the iron losses prediction, in soft magnetic materials with any voltage supply, starting from the knowledge of the iron losses with sinusoidal supply. The model is based on the separation of the loss contributions due to hysteresis, eddy currents and excess losses with sinusoidal supply. Since any contribution depends on the voltage supply characteristics, it is possible to find a direct mathematical relationship between the iron loss contribution and the voltage supply characteristics. As a consequence, an iron loss prediction can be obtained with any voltage supply, which does not produce hysteresis minor loop. The energetic model is based on coefficients that depend on the material characteristic. An accurate analysis of the model on eight magnetic materials, of different thickness and alloy, has been made, so the main coefficients for a large spread of magnetic materials, used for the electrical machines construction, have been found. The paper can be a useful support for electrical machine designers when the energetic performances of magnetic material, have to be predicted with the voltage supply different from the sinusoidal on
Breve storia del tessuto italiano dal Medioevo al XVIII secolo
No full textIl saggio prende in esame la storia della produzione tessile italiana dalle prime produzioni siciliane allo sviluppo dell'arte tra fine XIII - inizio XIV secolo, quando i tessitori lucchesi si imposero internazionalmente per capacità tecniche e originalità dei motivi decorativi. A partire dalle opere tessili presenti all'interno della collezione Lazzari e Martini, si prende in rassegna l'evoluzione dell'arte tessile italiana fino al Settecento, epoca durante la quale viene introdotto il telaio meccanico. Il capitolo è corredato di un glossario che spiega e armature tessili impiegate nell'arco cronologico esaminato e presenti nel catalogo del volume
A simplified thermal model for variable speed self cooled industrial induction motor
No full textIn this paper, a simplified thermal model for variable speed self cooled induction motors is proposed and experimentally verified. The thermal model is based on simple equations that are compared with more complex equations well known in literature. The proposed thermal model allows to predict the over temperature in the main parts of the motor, starting from the measured or the estimated losses in the machine. In the paper the description of the thermal model set up is reported in detail. Finally, the model is used to define the correct power derating for a variable speed PWM induction motor drive
Energy-efficient motors
Full text linkThe use of a copper-squirrel cage in induction motors has been analyzed testing a prototype rated 1.1 kW and comparing the performances with a twin machine with an aluminum cage. The comparison has been made using torque, efficiency, starting torque, and starting current. For the considered machine size, the obtained results show that the simple substitution of the aluminum with copper can improve the efficiency of no more than 1.5% at rated load. Taking into account the copper market cost trend, the use of copper cage increases the break-even time due to the higher cost of copper rotor respect to the aluminum one. For this reason, the discussion about the use of copper cage can be still considered ope
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