1,721,056 research outputs found
Novel Diagnostic Techniques for Rotating Electrical Machines—A Review
No full textThis paper aims to update the review of diagnostic techniques for rotating electrical machines of different type and size. Each of the main sections of the paper is focused on a specific component of the machine (stator and rotor windings, magnets, bearings, airgap, load and auxiliaries, stator and rotor laminated core) and divided into subsections when the characteristics of the component are different according to the type or size of the machine. The review considers both the techniques currently applied on field for the diagnostics of the electrical machines and the novel methodologies recently proposed by the researchers in the literature
Neural networks for energy flows prediction in facility systems
Full text linkA procedure for the short–term prediction of the thermal energy consumption of an hospital is shown in this paper. At first, linear ARX models are built to get information on the influence of the input variables on the output of the system. Therefore, non-linear models based on feedforward neural networks (NNARX) are built using the information provided by the linear estimate. The results obtained from the ARX and NNARX models are compared, concluding that NNARX models provide better results than ARX models, but the analysis of ARX models is necessary to obtain guidelines in the choice of the best regression vector as input for neural models
Dynamic behaviour of a four-poles turbo generator with rotor eccentricity
No full textSmooth-poles generators of electrical power
plants are flexible and this causes the eccentricity of the rotor with respect to the stator. The consequent air-gap asymmetrical distribution causes the phenomenon of the unbalanced magnetic pull (UMP). In this paper a non-linear model for the calculation of the UMP in synchronous electric machines is applied to a four-poles turbo-generator of 900 MVA, by taking into account not only the radial component of the electromagnetic stresses but also the tangential one
System identification for the prediction of the electric energy consumption of a dairy firm
Full text linkA system identification method based on black-box techniques for the prediction of the electric energy consumption in a dairy firm is presented in this paper. This prediction is required by the Italian free energy market where the energy sellers aim at selling energy according to a load flow scheduled some days in advance
Unbalanced magnetic pull modelling in a two poles three phase generator
No full textIn rotating electrical machines with eccentric rotor, an imbalance of the electromagnetic forces acting upon rotor and stator surfaces occurs, so that a net radial force, known as Unbalanced Magnetic Pull (UMP), is developed. In case of large size machines, such as turbo-generators supported by oil-film bearings, the approximation of circular orbit normally used in literature for the geometric centre of the rotor is not acceptable. Nevertheless, the authors who have dealt with UMP in big size generators have disregarded that these rotor filtered orbits are elliptical and generally the orbit centre is not concentric with the stator. A more
realistic model is introduced in this work and the actual distribution of the air-gap length during the rotation is determined in analytical terms, by taking into account the effects produced by the actual rotor orbit. The actual UMP is calculated by using the air-gap permeance approach and the simulation of the dynamical behaviour of a 320 MW generator is presented, showing the harmonic content of the UMP and the presence of non-linearities
How to define and control the significant environmental and energy aspects of combined-cycle energy production utilities
No full textIndagine sulla soddisfazione dei clienti e benchmarking: due strumenti della qualità totale
No full textBlack-box identification of the electromagnetic torque of induction motors: polynomial and neural models
Full text linkIn this paper we examine the problem of knowing the value of steady-state electromagnetic torque in induction motors installed in industrial plants. The models derived from two parametric black-box identification techniques (polynomial and neural) are implemented and tested for two motors and compared with the analytical model provided by the equivalent circuit theory. Both provide better performances when compared to the latter; the best performance is given by the neural model
Calcolo dello sbilanciamento magnetico nelle macchine rotanti elettriche
No full textNelle macchine elettriche rotanti con rotore eccentrico si ha uno sbilanciamento delle forze elettromagnetiche agenti tra rotore e statore che produce una forza radiale netta nota come Unbalanced Magnetic Pull (UMP). Nel caso di macchine di elevata potenza e velocità, quali i turbo-alternatori supportati da cuscinetti lubrificati, non è accettabile l’approssimazione di orbita circolare per il centro geometrico del rotore, normalmente usata in letteratura. La memoria introduce un modello più realistico mediante il quale si determina analiticamente la distribuzione reale del traferro durante la rotazione, tenendo conto degli effetti prodotti dall’orbita del rotore. L’UMP è calcolato con l’approccio della permeanza al traferro e la simulazione del comportamento dinamico di un generatore da 320 MVA mostra il contenuto armonico dell’UMP e la presenza di non-linearità
Detection and modelling of rotor eccentricity in electrical machines - an overview
No full textRotor eccentricity in electrical machines determines the non-uniformity of the air-gap and gives rise to an unbalanced magnetic pull (UMP), which causes vibrations and noise emission, speeds up the bearing wear and can produce a rub between rotor and stator. In the paper, an overview about this subject is presented, by classifying the researches according to the type of machine (induction, synchronous, brushless), the type of eccentricity (static or dynamic) and the type of studied effect (definition of the fault indicators, calculation of the UMP, modelling the dynamic behaviour of the machine)
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