IMEKO Event Proceedings

Page 851 of 855 Results 8501 - 8510 of 8545

Vicente León-Martínez, Joaquím Montañana-Romeu, José Roger-Folch, Antonio Cazarola-Navarro
WHY REACTIVE COMPENSATORS DO NOT IMPROVE THE EFFICIENCY CORRECTLY IN UNBALANCED CIRCUITS

This paper shows utility of phasor total unbalance power as a tool to explain working of unbalanced power systems. Conditions under shunt capacitors used to compensate reactive power can deteriorate the efficiency in three-phase four-wire unbalanced at loads power systems are described. Reactive phenomenon is studied using Emanuel´s positive-sequence fundamental-frequency reactive power, included in the IEEE Standard 1459-2000. Unbalance phenomenon is analyzed using the phasor total unbalance power. This quantity measures unbalance power due to the active loads by separating of those caused by the reactive loads. Results of this analysis show that reactive phenomenon in three-phase power systems can be compensated by single or three-phase capacitor banks, but undesirable effects on the system efficiency are consequence of the unbalance phenomenon and they can be increased by an inadequate reactive-compensator topology. It can have unbalance power due to the reactive loads even thought the reactive power has been compensated.

Tom Kuperij
WIB - WORKING-PARTY ON INSTRUMENT BEHAVIOUR

In 1962, five leading Dutch process industries (BPM now Shell, Algemene Kunstzijde Unie now AKZO, DSM, Hoogovens now Corus and Unilever) got together to explore combining tests and sharing the results on process instrumentation. Companies were at the time carrying out these activities individually at very high costs. The five concluded that sharing instrument evaluation reports, even with direct competitors, would be to the benefit of all.
A follow-up meeting held on the 16th December 1963 resulted in the formation of a co -operation panel under the Dutch name "Werkgroup voor Instrument Beoordeling", shortened to WIB. An independent laboratory, the Institute for Applied Physical Research -TNO, was approached and asked to carry out testing on behalf of WIB. TNO was also made responsible for the administration of the association, supervised by a Board of WIB members.
WIB activities attracted high interest from companies abroad wanting to join and a few years later the official language became English. WIB was translated into "Working-party on Instrument Behaviour". It was officially registered as a non- profit association in 1968.

Andrei Marinescu, Ionel Dumbravă, Lucian Mandache
Wide Band Current Transformer with Sensitivity Depending on the Measuring Signal Frequency

In many electrical engineering applications it is necessary to measure some complex current signals containing high frequency periodic components (MHz) or short duration pulses (ns) superimposed on a low frequency carrier signal (usually power line frequency). For the overall measurement of such complex signals, wide band current transformers (WBCT) are currently used. The paper refers to the achievement of a wide band current transformer whose sensitivity changes automatically with the frequency of the measuring current, so as it does not reach saturation at low frequency large signals.

Zbigniew Staroszczyk
WIDE FREQUENCY BAND POWER SYSTEM LINEAR AND LINEAR TIMEVARIANT MODEL IDENTIFICATION - SIGNAL PROCESSING PROBLEMS

The paper deals with the LTI/LTV power system models and their experimental verification. The frequency dependent system impedance is used for power system harmonics studies. As a voltage/current power system transfer function it explains well harmonics related phenomena observable in real systems. With very accurate impedance measurements power system nonlinearity can be observed. The nonlinearity manifest as system time-variance for which LTV (linear time varying) model can be used. New model improves power system description. The problems of such the model identification and verification are discussed in the paper.

Satoshi Takagi, Kazuyuki Kamijo, Takashi Usuda, Haruo Kawachi, Kazutomi Hanaki
WIDE-RANGE VERIFICATION OF THE GEOMETRY OF VICKERS DIAMOND INDENTERS

The three different methods, the NRLM-type Vickers indenter verification instrument, the scanning white light interferometry and the atomic force microscope, are used for the wide-range verification of a Vickers indenter. Those methods are available in different range of indenter surface and it was found that the integration of different instruments are helpful for the better understanding of the thorough geometry of a Vickers indenter. In addition, an improved instrument is developed for low-force and microhardness range and evaluated its availability. The results show that it can indicate the similar value to the most reliable instrument even in the smaller range of indenter and it suggests that the range of the reliable verification may be expanded to low-force and microhardness.

Umberto Pogliano, Bruno Trinchera
WIDEBAND TWO-PHASE GENERATOR FOR TESTING MULTIPLE ADCS IN MEASUREMENT SYSTEMS

A two-phase generator board has been investigated as a mean to perform precision tests on the ADCs of measurement system for wideband distorted power measurement. To overcome the limitation of the commercial generator in the lower frequency band, a design modification has been introduced. Verification of the characteristics of the generator shows the possibility of operation for in the low frequency range and the a phase shift is contained within 10 mrad up to 2 MHz. A characterization in terms of spectral purity and voltage stability of single tone synthesized are reported.

Tomasz Twardowski
WILL USB BE A STANDARD OF PC - INSTRUMENTATION COMMUNICATION?

The goal of this paper is to provide analysis of Universal Serial Bus, multipurpose communication interface, in application to laboratory measurement systems. This interface is compared with others, established measurement interface standards, especially IEEE-488, in a view of requirements in this specific application. The current market offer and trends in software and hardware design are reviewed. Obstacles to common use of USB in measurements are pointed out and projections to the future use are made.

R. Calaudi, T. Lo Feudo, E. Avolio, D. Gullì, M.F. De Pino, C. R. Calidonna
Wind Climatology in South Italy by Comparing Satellite Data and Ground Base Stations and a Correlation with NAO (North Atlantic Oscillation) Index

This study addresses preliminary results about the seasonal wind variability, especially during the winter season, in South Italy. Wind climate for the coastal waters off South Italy was estimated based on images of the Advanced Synthetic Aperture Radar (ASAR) onboard the ENVISAT satellite during the period from March 2002 to April 2012.

Will Almeida, Bruno Costa, Raimundo Freire, Francisco Santos, Sebastian Catunda
WIND TUNNEL FOR TEST OF SENSORS APPLIED TO ANEMOMETRYN

The wind tunnel development with wind speed control is presented in this paper using an ultrasonic anemometer. It were used the Time Difference and Phase Difference methods in the measurement of the air speed, and the circuit used for the measurement as for the speed control it was based on a microcontroller and an motor (fan). The experimental results obtained from the proposed circuit are compared with a commercial anemometer. The analysis of temporal response performance of the fan speed control circuit was developed to validate the proposed system.

Marcantonio Catelani, Lorenzo Ciani, Susanna Papini, Andrea Rindi
Wind turbine vibration monitoring based on finite-element (FE) simulation

The design of wind turbines evolved over time, with the scope of becoming less expensive and producing energy more efficiently. This paper deals with a FEM model for the representation of vertical axis wind turbine (VAWT) functioning for diagnostic and monitoring studies, which can provide fundamental data that can optimize the design of the monitoring system and an improvements in fault diagnosis related to vibration effects. In particular in this paper will discuss a monodimensional VAWT model, in order to reduce the computational time and, at the same, by using low computational resources to analyze several load cases. Growing usage of wind turbines has made maintenance a priority, and diagnosing potential faults is crucial to maintaining the turbine's desired availability. The simulation data obtained by the proposed approach allows to optimize condition monitoring and fault diagnostic techniques by the analysis of the wind turbine behavior before the real use on the field with both time and costs reduction.

Page 851 of 855 Results 8501 - 8510 of 8545