Analytical prediction of the electromagnetic torques in single-phase and two-phase AC motors

The single-phase and two-phase versions of AC motors can be modelled by means of the two-axis (d-q) theory with sufficient accuracy when the equivalent circuit parameters are correctly estimated. This work attempts to present a unified approach to the analytical prediction of the electromagnetic torque of these machines. Classical d-q axes formulation requires that the reference frame should be fixed on the frame where the asymmetries arise, i.e. the stator and rotor. The asynchronous torques that characterize the induction motors are modelled in a stationary reference frame, where the d-q axes coincide with the physical magnetic axes of the stator windings. For the permanent magnet motors, that may exhibit asymmetries on both stator and rotor, the proposed solution includes: a series of frame transformations, followed by symmetrical components decomposition. As in single-phase and two-phase systems the homopolar component is zero; each symmetrical component – negative and positive – is further analysed using d-q axes theory. The superposition principle is employed to consider the magnets and rotor cage effects. The developed models account for the most important asymmetries of the motor configuration. These are, from the stator point of view, different distribution, conductors' dimensions and number of effective turns, non-orthogonal magnetic axes windings and from the rotor point of view, asymmetrical rotor cage, variable reluctance, and permanent magnets effect. The time and space harmonics effect is ignored. Test data are compared with the computed data in order to observe how the simplifying assumptions affect the level of accuracy. The analytical prediction methods make possible torque computation according to the nature of the torque being computed, namely, induction, reluctance and excitation (permanent magnet). The results are available for quasi steady-state, steady-state (rated or synchronous speed) and dynamic analyses. All the developed mathematical models can be used in preliminary design for further optimisation and accurate estimation in complex numerical models. Another important feature of the analytical models for single-phase and two-phase AC motors, is that they can be directly implemented in any suitable electrical drives control strategy.reviewe

Study on Optical Fiber Insertion in Underground Telecommunication Networks Using Hydraulic Similarity

AbstractThe European regulations require a new approach of cities facilities networks, including the communication ones. In this respect, the communication providers generalize the underground networks, following the streets trails. The transmission support consists in a network of tubes, protecting a number of micro-tubes/microducts, which protect the real transmission facilitators made by optical fibers. Presently, the producers of this type of devices promote special norms of information on characteristics and installation of the product, but there are not reliable accepted standardized methods for optical fibers insertion in pre-installed micro-tubes/microducts and for the devices forces computation, necessary for underground communication networks. The micro-tubes are already installed in the protection cables and together are buried in the ground on different routes. It appears the necessity to introduce the fibers in the micro-tubes in this situation. Generally, it is a significant difference between the practical reality and the producers norms and indicators. In order to explain this situation, and considering the optical fibers dimensions, and the necessity to insert the fibers using specific lubricants, the paper propose a similarity model of the optical fibers insertion in the micro-tubes with the hydraulic model of laminar incompressible fluids flow in parallel or concentric micro- layers. In this phase, there are presented the results of experimental measurements and tests on in situ networks, composed by different types of materials and lubricants, as support for the hydraulic similitude

I romeni nella "Guerra d'Attila" di Nicoló da Casola

Conservatosi in un único manoscritto autógrafo della Biblioteca Estense di Modena, mutilo e alquanto corroso, e che per di piü non riporta la redazione definitiva, ma presenta varié cancellature e aggiunte, e manca di una terza parte, finale, forse solo progettata, il lunghissimo poema di 16 canti e ben 37.535 versi alessandrini misti ad endecasillabi "Líber. . . Atile fragelum dei translatattus de crónica in lingua Francie”, scritto dal notaio bolognese Nicoló da Casóla tra il 1358 e presumibilmente il 1368, mentre era esule nel Veneto e poi a Ferrara, se ha avuto qualche fortuna ai suoi tempi e ancora fino al sec. XVI, non é stato altrettanto fortunato in seguito e a livello, non piü e non soltanto popolare, ma scientifico.Facultad de Humanidades y Ciencias de la Educació

Optimal Control Applications in the Study of Production Management

A mathematical model for an economic problem of production management is proposed. The continuous optimal control problem is solved, by using the Pontryagin Maximum Principle at the level of a new space, called Lie algebroid. The controllability of the economic system is studied by using Lie geometric methods and involves restrictions on the final stock quantities. Finally, a numerical application is given