Search results for "FREQUENCY"
showing 10 items of 2158 documents
Rotor-bar breakage mechanism and prognosis in an induction motor
2015
© 1982-2012 IEEE. This paper proposes a condition-based maintenance and prognostics and health management (CBM/PHM) procedure for a rotor bar in an induction motor. The methodology is based on the results of a fatigue test intended to reproduce in the most natural way a bar breakage in order to carry out a comparison between transient and stationary diagnosis methods for incipient fault detection. Newly developed techniques in stator-current transient analysis have allowed tracking the developing fault during the last part of the test, identifying the failure mechanism, and establishing a physical model of the process. This nonlinear failure model is integrated in a particle filtering algor…
Capacity and safety analysis of hard-shoulder running (HSR). A motorway case study
2016
Abstract Operational motorway conditions can be improved by introducing traffic flow management and control systems, such as ramp metering (RM), high occupancy vehicle (HOV) lanes, real-time variable speed limits (VSLs), reversible lanes (RL), automated highway systems (AHS) and hard-shoulder running (HSR). The effects of such devices need to be examined in terms of capacity and safety. This paper examines the case study of the Italian motorway A22, which is supposed to be equipped with an HSR system implemented along 128 km in order to reduce congestion with consequent improvement in levels of service (LOS). We studied the traffic processes (capacity, flow distribution between lanes, relia…
Vibration signature analysis for monitoring rotor broken bar in double squirrel cage induction motors based on wavelet analysis
2014
Purpose – The purpose of this paper is to present a diagnosis technique, for rotor broken bar in double cage induction motor, based on advanced use of wavelet transform analysis. The proposed technique is experimentally validated. Design/methodology/approach – The proposed approach is based on a combined use of frequency sliding and wavelet transform analysis, to isolate the contribution of the rotor fault components issued from vibration signals in a single frequency band. Findings – The proposed technique is reliable for tracking the rotor fault components over time-frequency domain. The quantitative analysis results based on this technique are the proof of its robustness. Research limit…
A novel approach to current transformer characterization in the presence of harmonic distortion
2009
The current transformer (CT) performance under distorted waveform conditions is usually characterized by means of the frequency-response test. In this paper, a new way to characterize CTs, closer to real operation conditions, is proposed. The harmonic phase-angle and ratio errors are measured using a nonsinusoidal current composed of fundamental and one harmonic with adjustable phase shift. The new method was tested by determining the performance of two metering class CTs commonly used by the Italian power company. The errors measured using the proposed approach are larger than the ones obtained with the frequency response. This result suggests that the frequency-response approach for the e…
An Investigation of the Cutting Process for Chip Breaking Monitoring in Turning of Steels
1998
This paper presents some results of an experimental study on chip breaking monitoring when turning steels with chip forming inserts. In the first part of this study the recognition of chip forms by means of cutting force analysis in the frequency domain is described. Generally, the present work is concerned with the use of the interface control factor for determining the transition from unacceptable chip forms to the chip breaking. For this purpose experiments under approximately orthogonal machining conditions including measuring the shear strain, the cutting energy and the average interface temperature are carried out. The obtained results confirmed that the initiation of acceptable chip …
Performance analysis of Alamouti coded OFDM systems over wideband MIMO car-to-car channels correlated in time and space
2014
In this paper, the performance of Alamouti coded orthogonal frequency division multiplexing (OFDM) systems over car-to-car (C2C) fading channels correlated in time and space is analyzed. Taking different geometrical scattering models into account, a generalized expression of the time-variant transfer function (TVTF) is derived for wideband multiple-input multiple-output (MIMO) C2C channels. We present a generalized expression for the bit error probability (BEP), which will be used to describe the performance of Alamouti coded OFDM systems over different types of C2C channel models, such as the rectangle model, the tunnel model, the street model, and the curve model. The effect of the maximu…
Oil filled MV/LV Power Transformer Behavior in Narrow Band Power Line Communication Systems
2012
The aim of this paper is to characterize oil-filled power transformers in the narrow-band power-line communication (PLC) frequency range of 50-150 kHz. A new model is proposed for such type of a transformer, in the aforementioned frequency range of interest, in order to study its influence on the signal transmission and to investigate the possibility that the PLC signal can cross the power transformer itself. The new model is simpler than those previously proposed in literature, and it can be used in the whole frequency range available for NB PLC according to the CENELEC EN 50065-1 A-band. In order to validate the model, simulation and measurement results are compared for four oil-filled po…
Fatigue life under non-Gaussian random loading from various models
2004
Fatigue test results on the 10HNAP steel under constant amplitude and random loading with non-Gaussian probability distribution function, zero mean value and wide-band frequency spectrum have been used to compare the life time estimation of the models proposed by Bannantine, Fatemi–Socie, Socie, Wang–Brown, Morel and Łagoda–Macha. Except the Morel proposal which accumulates damage step by step with a proper ethodology, all the other models use a cycle counting method. The rainflow algorithm is used to extract cycles from random histories of damage parameters in time domain. In the last model, where a strain energy density parameter is employed, additionally spectral method is evaluated for …
A novel frequency domain method for predicting fatigue crack growth under wide band random loading
2007
This work deals with the evaluation of the fatigue crack growth rate of structural components subjected to uniaxial Gaussian stationary wide band random loading. In detail, a new frequency domain method that allows the user to estimate the expected crack growth rate directly from the PSD data is proposed. Using a stochastic mean function properly, introduced and described by simple closed form relationships implemented by systematic numerical simulations of a high number of wide band random processes, the proposed method permits to avoid the onerous time domain simulations and provides in general crack growth rate predictions in a good accordance with the so-called time domain method. Pract…
Static and dynamic policies with RFID for the scheduling of retrieval and storage warehouse operations
2013
Warehouses are essential components of logistics and supply chains. The performance of warehouse operations significantly affects the efficiency of the whole chain it belongs to. Radio frequency identification (RFID) is an emerging technology capable of providing real-time information about the location and properties of tagged object(s), such as people, equipment or products. The objective of this article is threefold, to propose and compare different offline and online policies for the scheduling of warehouse operations, to design a tool that allows the decision maker to compare policies and environments without putting them into practice, and to study the benefits that can be obtained if…