242 research outputs found
Fault-tolerant operation of single-phase SR generators
No full textThis paper studies fault-tolerant operation of multipole single-phase switched reluctance generators (SRGs), in particular, an 8/8-pole switched reluctance machine. The multipole single-phase SRG system is advantageous for reduced cost and higher efficiency compared to polyphase equivalents. However, using the classical phase-leg topology, a phase fault may prevent generating operation completely, since redundancy in the number of phases does not exist like polyphase systems. A new power converter topology which connects two coil banks in parallel is proposed for higher fault tolerance with minimum additional cost. Faulty coils can be disconnected with the proposed converter and the SRG can continue generating operation after coil faults with reduced output power. Output power per coil current under faults is studied. Open- and short-circuit coils are studied through linear analysis, finite-element analysis and static torque measurement. Generated currents under faults with the proposed converter are measured. The capability of the system to disconnect faulty coils dynamically is also shown
Multiple sets of solutions for harmonic elimination PWM bipolar waveforms: Analysis and experimental verification
No full textMultiple sets of solutions for the selective harmonic elimination pulse-width modulation method for inverter control exist. These sets present an independent solution to the same problem but further investigation reveals that certain sets may offer an improved overall harmonic performance. In this paper, a minimization method is discussed as a way to obtain these multiple sets of switching angles. A simple distortion harmonic factor that takes into account the first two most significant harmonics present in the generated waveform is considered in order to evaluate the performance of each set. The bipolar waveform is thoroughly analyzed and two cases are considered; single-phase patterns which eliminate all odd harmonics and three-phase counterparts which eliminate only the nontriplen odd harmonics from the line-to-neutral pattern but such harmonics are naturally eliminated from the line-to-line waveform. Experimental results support the theoretical considerations reported in the paper
A general magnetic-energy-based torque estimator: validation via a permanent-magnet motor drive
No full textThis paper describes the use of the current–flux-linkage ( ) diagram to validate the performance of a general magnetic-energy-based torque estimator. An early step in the torque estimation is the use of controller duty cycles to reconstruct the average phase-voltage waveform during each pulsewidth-modulation (PWM) switching period. Samples over the fundamental period are recorded for the estimation of the average torque. The fundamental period may not be an exact multiple of the sample time. For low speed, the reconstructed voltage requires additional compensation for inverter-device losses. Experimental validation of this reconstructed waveform with the actual PWM phase-voltage waveform is impossible due to the fact that one is PWM in nature and the other is the average value during the PWM period. A solution to this is to determine the phase flux-linkage using each waveform and then plot the resultant loops. The torque estimation is based on instantaneous measurements and can therefore be applied to any electrical machine. This paper includes test results for a three-phase interior permanent-magnet brushless ac motor operating with both sinusoidal and nonsinusoidal current waveforms
La casa di Tito Macro presso i Fondi Cossar
No full textIl contributo illustra le più recenti ricerche condotte presso i fondi ex Cossar di Aquileia dove sono tornati alla luce i resti di una delle più grandi e sfarzose case private di IV secolo dopo Crist
Embedded finite-element solver for computation of brushless permanent-magnet motors
No full textThis paper describes the theory underlying the formulation of a “minimum set” of finite-element solutions to be used in the design and analysis of saturated brushless permanent-magnet motors. The choice of finite-element solutions is described in terms of key points on the flux–MMF diagram. When the diagram has a regular shape, a huge reduction in finite-element analysis is possible with no loss of accuracy. If the loop is irregular, many more solutions are needed. This paper describes an efficient technique in which a finite-element solver is associated with a classical – -axis circuit model in such a way that the number of finite-element solutions in one electrical half-cycle can be varied between 1 and 360. The finite-element process is used to determine not only the average torque but also the saturated inductances as the rotor rotates
Le mura. Le infrastrutture urbane
No full textIl contributo illustra e commenta gli esiti delle indagini archeologiche condotte tra il 2009 e il 2015 nell'area dei Fondi Cossar di Aquileia. In particolare il contributo discute gli esiti delle ricerche condotte lungo la linea delle fortificazioni repubblicane e nei settori delle strade urbane che fiancheggiavano la grande domus dei Fondi Cossar. Il contributo mette in luce i caratteri tecnico-costruttivi delle mura repubblicane e gli apporti progettali di maestranze greche, rivelati dalle forme costruttive, dai materiali utilizzati e dagli standard metrologici impiegati. Grazie allo studio delle infrastrutture il quadro urbano definito dalla linea fortificata viene a definirsi nel suo evolversi nel tempo, dal I secolo a.C. fino alla tarda antichità
Appendice. Analisi in sezione sottile di ceramiche comuni grezze ad Aquileia, fondi ex Cossar
No full textA General Model of the Laminated Steel Losses in Electric Motors with PWM Voltage Supply
No full textA general model for estimating the laminated steel losses under PWM voltage supply
No full textThe new model is based on a modified Steinmetz equation and employs a hysteresis-loss multiplicative coefficient and a combined coefficient for eddy-current and excess losses, both coefficients being variable with induction and frequency. The material model coefficients are first identified through multifrequency tests with sine-wave excitation. The iron-loss increase due to pulsewidth-modulation supply is estimated using global waveform parameters of the nonsinusoidal voltage. The study includes three different grades of non-grain-oriented electric steel. The data cover a wide range of fundamental frequency from 10 to 600 Hz and induction from 0.05 to 2 T. The errors of the computational model are small at relatively low fundamental frequency and increase thereafter. The main advantages of the model are its simplicity of use and minimal data requirements
Line-start permanent-magnet motor single-phase steady-state performance analysis
No full textThis paper describes an efficient calculating procedure for the steady-state operation of a single-phase line-start capacitor-run permanent-magnet motor. This class of motor is beginning to be applied in hermetic refrigerator compressors as a high-efficiency alternative to either a plain induction motor or a full inverter-fed drive. The calculation relies on a combination of reference-frame transformations including symmetrical components to cope with imbalance, and dq axes to cope with saliency. Computed results are compared with test data. The agreement is generally good, especially in describing the general properties of the motor. However, it is shown that certain important effects are beyond the limit of simple circuit analysis and require a more complex numerical analysis method
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