1,721,533 research outputs found
Direct torque control of induction motor drives
No full textDirect torque control (DTC) is an emerging technique for controlling PWM inverter-fed induction motor (IM) drives. It allows the precise and quick control of the IM flux and torque without calling for complex control algorithms. In principle, moreover, it requires only the knowledge of the stator resistance. The tutorial starts by reviewing the basic operation of an IM and of a PWM inverter using the space vector theory. The field-oriented (FO) control of an IM drive is also reviewed. Then the concept of DTC is illustrated and three DTC-based strategies [i.e. switching table (ST), direct self control (DCS), space vector modulation (SVIM)] are described. The ST strategy is dealt with in detail, discussing the results which can be obtained with different choices of the switching table. Problems associated with the selection of the amplitude of the hysteresis bands of the flux and torque controllers are illustrated by means of experimental data. Merits and limits of DTC are reported and a comparison with FO control is give
Il modello multidimensionale dell'assessment e sue applicazioni
No full textIl Modello Multidimensionale dell’Assessment intende promuovere una psicologia che si occupi non solo delle sintomatologie e delle patologie, ma anche della qualità di vita del malato. Esso prevede la raccolta di dati clinici attraverso tre canali: cognitivo verbale, comportamentale e psicofisiologico. In ambito ostetrico-ginecologico si sofferma sulla qualità di vita, l’umanizzazione e la personalizzazione
Direct stator flux and torque control of an induction motor: theoretical analysis and experimental results
No full textDirect stator flux and torque control (DSFTC) is a novel technique for the control of a voltage inverter-fed induction motor (IM). It carries out a precise and quick control of the stator flux and the electromagnetic torque of an IM without calling for coordinate transformation, speed measurement and stator current control. In principle, moreover, DSFTC operation requires only the knowledge of the stator resistance. The tutorial starts by reviewing the operation of an IM and of a voltage inverter using the space vector theory. The concept of DSFTC is then introduced, illustrating the action of an inverter supply on the stator flux and the electromagnetic torque of an IM. Afterwards, implementation of DSFTC according to the switching table (ST) strategy is focused. Different STs are considered and their influence on the torque response is shown by means of calculated and experimental data. The relationships between the drive performance, such as losses and switching frequency, and the amplitude of the hysteresis bands of the flux and torque controllers are given. Sensitivity to errors in the control system is also investigated. Solutions which improve the torque characteristic and the low-speed performance of the drive are presented. Finally, the DSFTC strategy, termed direct self control, and a scheme based on the space vector modulation are described, explaining how they can be interpreted as either a particular case or an extension of the ST strateg
DTC-based strategies for induction motor drives
No full textDirect torque control (DTC) is an emerging technique for controlling the PWM inverter-fed induction motor (IM) drives. It allows the precise and quick control of the IM flux and torque without calling for complex control algorithms. In principle, moreover, DTC requires only the knowledge of the stator resistance. The tutorial starts by reviewing the basic operation of an IM and of a PWM inverter using the space vector theory. The field-oriented (FO) control is also reviewed. Then the concept of DTC is illustrated and three DTC-based strategies (i.e. switching table (ST), direct self control (DSC), space vector modulation (SVM)) are described. The ST strategy is dealt with in depth, illustrating by means of experimental data the flux and torque responses generated with different choices of the switching table and the influence of the amplitude of the hysteresis bands of the flux and torque controllers on the drive performance. Furthermore, an improved stator flux estimator is presented which allows the system under to be kept under control even at standstill. Finally the sensitivity of the control system to parameter variations is presente
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
