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Article
Publication date: 28 September 2010

Mohammad Asaduzzaman Chowdhury

The purpose of this paper is to investigate experimentally the effect of natural frequency of the experimental set‐up on wear rate of glass fiber‐reinforced plastic (GFRP).

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Abstract

Purpose

The purpose of this paper is to investigate experimentally the effect of natural frequency of the experimental set‐up on wear rate of glass fiber‐reinforced plastic (GFRP).

Design/methodology/approach

Experimental and dimensional analysis. A pin‐on‐disc apparatus having facility of vibrating the test samples at different directions, amplitudes and frequencies was designed and fabricated. The natural frequency of the set‐up was varied by adding dead loads of the set‐up from 0 to 50 kg. At each added load, the wear rate has been measured.

Findings

The presence of natural frequency of vibration indeed affects the wear rate considerably. The values of wear rate increase with the increase of natural frequency of vibration of the experimental set‐up. As the wear rate increases with increasing natural frequency of vibration, therefore, maintaining appropriate level of natural frequency vibration wear may be kept to some lower value to improve mechanical processes. The empirical formula of wear rate is derived from the dimensionless analysis. The wear rate obtained from the correlation shows better relationship with experimental results.

Practical implications

It is expected that the applications of these results will contribute to the improvement of different concerned mechanical systems and machines.

Originality/value

Considering the lack of correlation among wear rate, natural frequency of the experimental set‐up and other operating parameters, the present research was started to find out suitable correlation and a way of reducing wear rate by applying known natural frequency of vibration at a particular direction. Therefore, in this paper, an attempt is made to investigate the wear behavior of GFRP under natural frequency of the experimental set‐up. It is expected that the applications of these results will contribute to the improvement of different concerned mechanical systems.

Details

Industrial Lubrication and Tribology, vol. 62 no. 6
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 1 June 2003

Mayela Zamora, Manus Henry and Christian Peter

The use of frequency output for measurement transmission remains common in the design of smart transmitters. Conventional methods of frequency generation, based on…

Abstract

The use of frequency output for measurement transmission remains common in the design of smart transmitters. Conventional methods of frequency generation, based on counting clock cycles, have a precision which is inversely proportional to the frequency to be generated. Consequently, frequency output precision could be much lower than the measurement precision. This paper describes a simple frequency generation technique which, when implemented in low‐cost hardware, provides a precision of 10−6 per cent for all frequencies. The method represents an intermediate non‐available frequency by dithering between two exact frequencies. Averaging over some reasonably short timescale provides the desired frequency to high precision.

Details

Sensor Review, vol. 23 no. 2
Type: Research Article
ISSN: 0260-2288

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Article
Publication date: 9 January 2007

Fatma Ben Salem and Ahmed Masmoudi

This paper aims to discuss a comprehensive analysis of the effects of torque and flux hysteresis bands on the inverter average switching frequency considering an induction…

Abstract

Purpose

This paper aims to discuss a comprehensive analysis of the effects of torque and flux hysteresis bands on the inverter average switching frequency considering an induction machine drive under the control of the Takahashi DTC strategy.

Design/methodology/approach

The analysis of the effects of torque and flux hysteresis bands on the inverter average switching frequency is carried out taking into account the speed range and the sampling period.

Findings

It has been found that the inverter average switching frequency could be more or less taken down according to the speed range and the sampling period by selecting suitable flux and torque hysteresis bands.

Research limitations/implications

This work should be extended by an experimental validation of the established results.

Practical implications

The reduction of the inverter switching frequency is of great importance in direct torque controlled induction motor drive as far as it leads to a decrease of the torque ripple and an increase of the efficiency.

Originality/value

For given torque and flux hysteresis bands, the inverter average switching frequency presents nonlinear shape. Given the fact that the flux switching frequency is a linear function of the speed, one can conclude that the nonlinearity of the inverter average switching frequency is due to the torque switching frequency. This statement has been proven by the introduction of the so‐called focal speeds for the torque switching frequency turns to be null.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 26 no. 1
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 29 March 2011

Kirubakaran Dhandapani and Rama Reddy Sathi

The purpose of this paper is to present, a novel boost‐active clamp bridge single stage high‐frequency zero voltage soft‐switching‐pulse width modulation (ZVS‐PWM…

Abstract

Purpose

The purpose of this paper is to present, a novel boost‐active clamp bridge single stage high‐frequency zero voltage soft‐switching‐pulse width modulation (ZVS‐PWM) inverter, which converts the utility frequency AC power into high‐frequency AC power with an embedded controller. This single stage high‐frequency inverter is composed of a single‐phase diode bridge rectifier, a non‐smoothing filter, a boost‐active clamp bridge type ZVS‐PWM high‐frequency inverter, and an induction‐heated load with planar type litz wire working coil assembly. Also, the paper discusses how to extend the soft‐switching operation ranges and improve power conversion efficiency.

Design/methodology/approach

The proposed converter is simulated and it is implemented using embedded controller.

Findings

It was found that the single stage high‐frequency induction heating (IH) inverter using boosted voltage function can eliminate the DC and low‐frequency components of the working coil current and reduce the power dissipation of the circuit components and switching devices.

Originality/value

The paper shows that the PWM HF inverter is preferred for IH, since it has reduced switching losses and switching stresses. The paper can be extended to PC‐based wireless control, which can be part of a distributed control system in major industrial heating systems.

Details

Journal of Engineering, Design and Technology, vol. 9 no. 1
Type: Research Article
ISSN: 1726-0531

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Article
Publication date: 29 April 2014

Michał Lewandowski and Janusz Walczak

A highly accurate method of current spectrum estimation of a nonlinear load is presented in this paper. Using the method makes it possible to evaluate the current…

Abstract

Purpose

A highly accurate method of current spectrum estimation of a nonlinear load is presented in this paper. Using the method makes it possible to evaluate the current injection frequency domain model of a nonlinear load from previously recorded time domain voltage and current waveforms. The paper aims to discuss these issues.

Design/methodology/approach

The method incorporates the idea of coherent resampling (resampling synchronously with the base frequency of the signal) followed by the discrete Fourier transform (DFT) to obtain the frequency spectrum. When DFT is applied to a synchronously resampled signal, the spectrum is free of negative DFT effects (the spectrum leakage, for example). However, to resample the signal correctly it is necessary to know its base frequency with high accuracy. To estimate the base frequency, the first-order Prony's frequency estimator was used.

Findings

It has been shown that the presented method may lead to superior results in comparison with window interpolated Fourier transform and time-domain quasi-synchronous sampling algorithms.

Research limitations/implications

The method was designed for steady-state analysis in the frequency domain. The voltage and current waveforms across load terminals should be recorded simultaneously to allow correct voltage/current phase shift estimation.

Practical implications

The proposed method can be used in case when the frequency domain model of a nonlinear load is desired and the voltage and current waveforms recorded across load terminals are available. The method leads to correct results even when the voltage/current sampling frequency has not been synchronized with the base frequency of the signal. It can be used for off-line frequency model estimation as well as in real-time DSP systems to restore coherent sampling of the analysed signals.

Originality/value

The method proposed in the paper allows to estimate a nonlinear load frequency domain model from current and voltage waveforms with higher accuracy than other competitive methods, while at the same time its simplicity and computational efficiency is retained.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 33 no. 3
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 1 June 2005

Sergey Y. Yurish, Nikolay V. Kirianaki and Ramon Pallàs‐Areny

To provide detailed information about the novel universal frequency‐to‐digital converter UFDC‐1, which can help engineers and researchers to design new digital sensors and…

Abstract

Purpose

To provide detailed information about the novel universal frequency‐to‐digital converter UFDC‐1, which can help engineers and researchers to design new digital sensors and transducers, as well as smart sensors and sensor systems.

Design/methodology/approach

The high performance of the UFDC‐1 is achieved by using four novel measuring methods for frequency‐time parameters. All existing integrated frequency‐to‐digital converters and frequency (time) output sensors have been reviewed and current design requirements for the UFDC‐1 have been formulated.

Findings

The UFDC‐1 enables the transition from traditional analog (voltage and current) sensors output to frequency‐time output. This yields a lot of benefits due to the properties of frequency as informative parameter. No output standardization is necessary, as opposed to the case of analog output sensors. Users can now work with the UFDC‐1, the same as with traditional ADCs. Sensor manufacturers can simply integrate the UFDC‐1 in microsystems and digital output sensors in order to produce serial output or bus capability.

Practical implications

The UFDC‐1 has many applications: obtaining a digital output from any frequency, period, duty‐cycle, time interval, phase‐shift, pulse number output sensors, up to one chip digital sensors design and smart (self‐adaptive) sensors, thanks to its programmable relative error and non‐redundant conversion time. The UFDC‐1 can work with any existing frequency‐time domain sensor to produce a digital output or create multiparametric smart sensors and systems.

Originality/value

This paper fulfils an identified information need and offers practical help to engineers and researchers in designing new digital sensors and transducers, as well as smart sensors and systems using a minimum of hardware.

Details

Sensor Review, vol. 25 no. 2
Type: Research Article
ISSN: 0260-2288

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Article
Publication date: 1 March 1997

Chongbin Zhao, G.P. Steven and Y.M. Xie

Extends the evolutionary structural optimization method to the solution for the natural frequency optimization of a two‐dimensional structure with additional…

Abstract

Extends the evolutionary structural optimization method to the solution for the natural frequency optimization of a two‐dimensional structure with additional non‐structural lumped masses. Owing to the significant difference between a static optimization problem and a structural natural frequency optimization problem, five basic criteria for the evolutionary natural frequency optimization have been established. The inclusion of these criteria into the evolutionary structural optimization method makes it possible to solve structural natural frequency optimization problems for two‐dimensional structures with additional non‐structural lumped masses. Gives two examples to demonstrate the feasibility of the extended evolutionary structural optimization method when it is used to solve structural natural frequency optimization problems.

Details

Engineering Computations, vol. 14 no. 2
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 19 August 2021

Morteza Ghaseminezhad, Aref Doroudi, Seyed Hossein Hosseinian and Alireza Jalilian

Voltage fluctuation (flicker) is a power quality disturbance that can produce several undesirable effects on industrial equipment. This paper aims to present the…

Abstract

Purpose

Voltage fluctuation (flicker) is a power quality disturbance that can produce several undesirable effects on industrial equipment. This paper aims to present the methodology and results of investigations undertaken to examine the speed and torque of an induction motor (IM) under voltage fluctuation conditions.

Design/methodology/approach

The IM response to different characteristics of voltage fluctuations is presented. It will be shown that under a special condition the IM torque can even reach two times the rated torque. To show how this occurs, a qualitative discussion is given on the motor response by linearized equations.

Findings

The small-signal analysis was used to determine the frequency which leads to maximum speed fluctuations. It was shown that, if the motor is excited with a modulation frequency (resonant frequency) which is one of its natural frequencies (modes), the mode will act as a fluctuating amplifier and greatly increase the amplitude of torque and speed fluctuations. Sensitivity analysis is also carried out to evaluate the influence of motor parameters on the resonance frequency. The results show that the resonance frequency is not affected at all by the changes in magnetizing reactance. This has been shown that magnetic saturation does not have any impact on the resonance frequency. The most effective parameters are rotor and stator resistances.

Originality/value

With the increasing popularity and use of arc furnace loads in the metallurgy industry and due to the wide application of large IMs in the industry, it is possible that the frequency of torque pulsation locates near a natural frequency and then will create an oscillation with a large magnitude, potentially leading to accelerated fatigue or severe damage of shaft. However, if this phenomenon occurs in industries, the resonance frequency must be filtered from the input voltage. Experimental results on a 1.1 kW, 380 V, 50 Hz, 2 pole IM are used to validate the accuracy of simulation results.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering , vol. 40 no. 4
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 5 July 2021

Shuzhen Zhu, Xiaofei Wu, Zhen He and Yining He

The purpose of this paper is to construct a frequency-domain framework to study the asymmetric spillover effects of international economic policy uncertainty on China’s…

Abstract

Purpose

The purpose of this paper is to construct a frequency-domain framework to study the asymmetric spillover effects of international economic policy uncertainty on China’s stock market industry indexes.

Design/methodology/approach

This paper follows the time domain spillover model, asymmetric spillover model and frequency domain spillover model, which not only studies the degree of spillover in time domain but also studies the persistence of spillover effect in frequency domain.

Findings

It is found that China’s economic policy uncertainty plays a dominant role in the spillover effect on the stock market, while the global and US economic policy uncertainty is relatively weak. By decomposing realized volatility into quantified asymmetric risks of “good” volatility and “bad” volatility, it is concluded that economic policy uncertainty has a greater impact on stock downside risk than upside risk. For different time periods, the sensitivity of long-term and short-term spillover economic policy impact is different. Among them, asymmetric high-frequency spillover in the stock market is more easily observed, which provides certain reference significance for the stability of the financial market.

Originality/value

The originality aims at extending the traditional research paradigm of “time domain” to the research perspective of “frequency domain.” This study uses the more advanced models to analyze various factors from the static and dynamic levels, with a view to obtain reliable and robust research conclusions.

Details

Kybernetes, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0368-492X

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Book part
Publication date: 6 January 2016

Lukas Koelbl, Alexander Braumann, Elisabeth Felsenstein and Manfred Deistler

This paper is concerned with estimation of the parameters of a high-frequency VAR model using mixed-frequency data, both for the stock and for the flow case. Extended…

Abstract

This paper is concerned with estimation of the parameters of a high-frequency VAR model using mixed-frequency data, both for the stock and for the flow case. Extended Yule–Walker estimators and (Gaussian) maximum likelihood type estimators based on the EM algorithm are considered. Properties of these estimators are derived, partly analytically and by simulations. Finally, the loss of information due to mixed-frequency data when compared to the high-frequency situation as well as the gain of information when using mixed-frequency data relative to low-frequency data is discussed.

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