118,276 research outputs found
International Standards for the Induction Motor Efficiency Evaluation: a Critical Analysis of the Stray-Load Losses Determination
No full textMotor efficiency has to be measured or calculated in accordance with international standards. The most important standards are the IEEE 112-B, IEC 34-2, and JEC 3 . In this paper, a comparison of the measurement procedures defined by these international standards is reported, together with some comments on the prescribed methodologies. The comparison is based on experimental results obtained by tests on four general-purpose three-phase induction motors. The stray-load loss measurement represents a critical key for the correct evaluation of the motor efficiency. For this reason, a critical analysis of this type of losses has been performed. In particular, in order to understand which are the most critical quantities that influence their evaluation, the stray-load loss sensitivity to the measurement errors is analyzed. In the final part of the paper the temperature influence, on the conventional iron losses, is experimentally analyzed. The performed tests show that the temperature difference between the no-load test and the motor real operative conditions is not negligible
Position-sensorless control of permanent-magnet-assisted synchronous reluctance motor
No full textThe sensorless control of permanent-magnet-assisted synchronous reluctance (PMASR) motors is investigated, in order to conjugate the advantages of the sensorless control with full exploitation of the allowed operating area, for a given inverter. An additional pulsating flux is injected in the d-axis direction at low and zero speed, while it is dropped out, at large speed, to save voltage and additional loss. A flux-observer-based control scheme is used, which includes an accurate knowledge of the motor magnetic behavior. This leads, in general, to good robustness against load variations, by counteracting the magnetic cross saturation effect. Moreover, it allows an easy and effective correspondence between the wanted torque and flux and the set values of the chosen control variables, that is d-axis flux and q-axis current. Experimental verification of the proposed method is given, both steady-state and dynamic performance are outlined. A prototype PMASR motor will be used to this aim, as part of a purposely assembled prototype drive, for light traction application (electric scooter
Cross-Saturation Effects in IPM Motors and Related Impact on Sensorless Control
No full textPermanent-magnet-assisted synchronous reluctance motors are well suited to zero-speed sensorless control because of their inherently salient behavior. However, the cross-saturation effect can lead to large errors on the position estimate, which is based on the differential anisotropy. These errors are quantified in this paper as a function of the working point. The errors that are calculated are then found to be in good accordance with the purposely obtained experimental measurement
Impact of cross-saturation in sensorless control of transverse-laminated synchronous reluctance motors
No full textSynchronous reluctance (SyR) motors are well suited to a zero-speed sensorless control, because of their inherently salient behavior. However, the cross-saturation effect can lead to large errors on the position estimate, which is based on the differential anisotropy. These errors are quantified in the paper, as a function of the working point. The so-calculated errors are then found in good accordance with the purposely obtained experimental measurements. The impact of the amplitude of the carrier voltage is then pointed out, leading to a mixed (carrier injection plus electromotive force estimation) control scheme. Last, a scheme of this type is used, with a commercial transverse-laminated SyR motor. The robustness against cross-saturation is shown, in practice, and the obtained drive performance is pointed out proving to be effective for a general-purpose applicatio
Determinarción de la tolerancia a la salinidad en híbridos de girasol [Helianthus annuus l.] mediante la cuantificación de parámetros morfofisiológicos
No full textFil: Pastorelli, Joaquín Eduardo. Universidad Nacional del Litoral; Argentina
The mediational role of prosocial behaviours in the association between parent-child relationship quality and school performance
No full textTHE MEDIATIONAL ROLE OF PROSOCIAL BEHAVIOURS IN THE ASSOCIATION BETWEEN PARENT-CHILD RELATIONSHIP QUALITY AND SCHOOL PERFORMANCE
E. Basili, M. Gerbino, L. Di Giunta, E. Thartori, C. Lunetti, A. Favini, C. Pastorelli
Sapienza University of Rome (ITALY)
School performance and attainment play a major role in individuals’ development, therefore it is crucial to investigate the mechanisms by which children’s academic adjustment is influenced. Several studies have stressed the relevance of Prosocial Behaviour (PB) - defined as voluntary actions aimed at benefiting others such as helping, consoling, donating (Eisenberg et al., 2006)- in predicting several adjustment outcomes, including school achievement (Caprara et al. 2000; Closson, 2009). Prosocial behaviour has been considered a relatively “malleable” variable that can be strengthened through appropriate educational actions (e.g., Caprara, Luengo Kanacri et al., 2015) and some studies have found that parental warmth, responsiveness, support, and involvement being positively related to children’s prosociality (Eisenberg et al., 2015). Although the relevance of parents as social agents in children’s interaction with their environment, few studies have focused on the specific associations between parent-child relationship and school performance. For example, Diener et al. (2008) found that quality of parent–child emotional relationship is linked to the child’s self-perception of competence, suggesting the potential role of family relational climate on school achievements. The present study aims to examine the relation between Parent- Child Relationship Quality - intended as the parents’ capacity to show affection and support toward their children (parental warmth) and to express interest and solicitude to their children’s needs (parental involvement) (Pastorelli et al. 2015) -, children’s prosocial behaviours and school performance. Our hypothesis is that parental warmth and involvement may influence children’s school performance through their engagement in prosocial behaviours. Interviews were conducted in Italy-Rome with 8 to 12 years old children (mean age=9.33, DS=.87; 51% boys), their mothers and their fathers, all involved in an ongoing longitudinal study (e.g. Lansford et al., 2014). Parent-child relationship quality was assessed via parent- and child-reports (The Parental Acceptance-Rejection/Control Questionnaire-Short Form; Rohner, 2005), prosocial behaviour was child reported (Children’s Prosocial Behaviour Scale; Pastorelli,1996), school performance was assessed via parent-reports (Child Behaviour Checklist; Achembach,1991). Structural equation models revealed that child prosocial behaviour significantly mediated the associations between parent-child relationship quality and school performance. Specifically, a responsive and involving parent-child relationship tends to promote children prosocial behaviours and, in turn, a better school performance. These findings suggest that teachers, scholars and professionals in the field of education could take advantage of considering the relevance of prosocial behaviour as key mechanism through which children’s school performance could be ameliorated.
keywords: prosocial behaviours, school performance, parent-child relationship
- …
