Vol. 12, No. 3, October 2015


Muhammad Sakir Hossain, Muhammad Abdus Samad
The Tropospheric Scintillation Prediction of Earth-to-Satellite Link for Bangladeshi Climatic Condition
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DOI: 10.2298/SJEE1503263H
Abstract: The performance of earth-to-satellite link largely depends on various environmental factors like rain, fog, cloud, and atmospheric effects like ionospheric and tropospheric scintillation. In this paper, the tropospheric scintillation of Bangladesh, a subtropical country, is predicted based on measured climatic parameters, like relative humidity, temperature. In this prediction, ITU scintillation model are used. Four major cities, named Dhaka, Chittagong, Rajshahi and Sylhet, of Bangladesh are selected for prediction of scintillation. From the simulation result, Rajshahi is found to be the most badly affected region by the scintillation fade depth (SFD), which is followed by Chittagong and the SFD is minimum in Dhaka and Sylhet. The difference in SFDs among the considered cities does not vary heavily. It is also found that the SFD varies from 3 dB to 13 dB depending on the frequency in used. Moreover, higher scintillation is found in rainy season of Bangladesh. During this period, the scintillation becomes double of the average figure.
Keywords: Troposphere, Scintillation, Bangladesh, Satellite link, Attenuation.

Dušan N. Grujić, Lazar Saranovac
Broadband Power Amplifier Limitations due to Package Parasitics
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DOI: 10.2298/SJEE1503275G
Abstract: Limitations of CMOS broadband power amplifiers due to package parasitics have been explored in this paper. The constraints of power amplifier matching network, realized as a third-order Chebyshev filter, have been derived, and a new power amplifier design flow has been proposed. As an example of a proposed design flow, an UWB power amplifier has been designed. Transistor level large signal simulation results are in excellent agreement with theoretical predictions.
Keywords: Broadband, CMOS, Package, Power amplifier.

Komlen Lalović, Milan Milosavljević, Ivan Tot, Nemanja Maček
Device for Biometric Verification of Maternity
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DOI: 10.2298/SJEE1503293L
Abstract: Biometry is the scientific discipline and technology that measures and analyzes physiological or behavioral characteristics of people and is widely deployed in modern society security systems. Device for biometric identification of maternity is a dual fingerprint scanner that acquires fingerprint templates of the mother and the child at the very moment of birth, generates unique ID reference, and further guarantees mother-child relationship with that reference. Technical issue that is solved with this work and the proposed device is scanning, processing, and storing encrypted biometric templates with a goal to provide a 100% guarantee maternity for each new born child. Scanning the fingerprints of both mother and the child simultaneously, at moment of birth, and pairing them with unique ID reference removes potential fears occurring from hospital negligence to malicious activities, while the data encryption raises the whole process to the highest level of security and confidentiality. The main contribution of the device that removes the fear that almost every mother has in this period as it provides an answer to the question: “Is this my baby?” with a 100% guarantee “It’s certainly yours!”
Keywords: Biometry, Fingerprint, Minutiae, Child, Patent.

Miloje M. Kostić
Calculation Improvement of No-load Stray Losses in Induction Motors with Experimental Validation
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DOI: 10.2298/SJEE1503303K
Abstract: On the basis of the known fact that all air gap main flux density variations are enclosed by permeance slot harmonics, only one component of stray losses in rotor (stator) iron is considered in the new classification, instead of 2 components: rotor (stator) pulsation iron losses, and rotor (stator) surface iron losses. No-load rotor cage (high-frequency) stray losses are usually calculated. No-load stray losses are caused by the existence of space harmonics: the air-gap slot permeance harmonics and the harmonics produced by no-load MMF harmonics. The second result is the proof that the corresponding components of stray losses can be calculated separately for the mentioned kind of harmonics. Determination of the depth of flux penetration and calculations of high frequency iron losses are improved. On the basis of experimental validation, it is proved that the new classification of no-load stray losses and the proposed method for the calculation of the total value is sufficiently accurate.
Keywords: High frequency no-load losses, Rotor (stator) iron no-load stray losses, Rotor cage high-frequency losses, Permeance slot harmonics, MMF harmonics.

Vladimir Gurevich
Protecting Power Equipment Against Magnetohydrodynamic Effects (MHD) of Electromagnetic Pulses (EMP)
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DOI: 10.2298/SJEE1503321G
Abstract: The article is devoted to the effects of geomagnetic-induced currents (GIC) on electrical equipment of power systems and analyzes technical measures for protection against such effects. It is noted that the difference between high-altitude nuclear detonation and solar storm GICs forces applying different methods of electrical equipment protection. It also illustrates that enhancement of transformer immunity to GICs without saturation prevention is not an effective measure to protect the power system. The article offers a special relay designed for fast disconnection of the transformer under GICs.
Keywords: EMP, magnetohydrodynamic effect, Nuclear detonation, E3 component, Geomagnetic induced current, GIC.

Dahmani Aissa, Rachid Abdessemed
Study of Applying a Hybrid Standalone Wind-Photovoltaic Generation System
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DOI: 10.2298/SJEE1503333A
Abstract: The purpose of this paper is the study of applying a hybrid system wind/photovoltaic to supply a community in southern Algeria. Diesel generators are always used to provide such remote regions with energy. Using renewable energy resources is a good alternative to overcome such pollutant generators. Hybrid Optimization Model for Electric Renewable (HOMER) software is used to determine the economic feasibility of the proposed configuration. Assessment of renewable resources consisting in wind and solar potentials, load profile determination and sensitivity of different parameters analysis were performed. The cost of energy (COE) of 0.226 $/kWh is very competitive with those found in literature.
Keywords: Hybrid system, HOMER, Sensitivity analysis, Cost of energy.

Radojle Radetić, Marijana Pavlov-Kagadejev, Nikola Milivojević
The Analog Linearization of Pt100 Working Characteristic
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DOI: 10.2298/SJEE1503345R
Abstract: The most exact temperature measurement can be made by using platinum sensors. Temperatures from –254.3 °C up to +850 °C can be measured with Pt100 sensor. The relationship between resistance and temperature is relatively linear, but for measurements of very high precision, Pt100 working curve should be a little bit improved. The paper describes an efficient way of measurement characteristic linearization by using the analogue electric circuits. The obtained results proved the initial considerations and the Pt100 becomes rather transducer than pure sensor.
Keywords: Temperature measurement, Pt100 temperature sensor, Measurement working characteristic, Transfer function linearization.

Reza Ghanaee, Ahmad Darabi, Arash Kiyoumarsi, Mohammad Reza Baghayipour, Mohammad Javad Morshed
A Nonlinear Equivalent Circuit Model for Flux Density Calculation of a Permanent Magnet Linear Synchronous Motor
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DOI: 10.2298/SJEE1503359G
Abstract: In this paper, a nonlinear magnetic equivalent circuit is presented as an analytical solution method for modeling of a permanent magnet linear synchronous motor (PMLSM). The accuracy of the proposed model is verified via comparing its simulation results with those obtained by two other methods. These two are the Maxwell’s Equations based analytical method and the well-known finite elements method (FEM). Saturation and any saliency e.g. slotting effects can be considered properly by both nonlinear magnetic equivalent circuit and FEM, where it cannot be taken into account easily by the Maxwell’s Equations based analytical approach. Accordingly, as the simulation results presented in this paper confirm, the proposed nonlinear magnetic equivalent circuit is compatible with FEM regarding the accuracy while it requires very shorter execution time. Therefore, the magnetic equivalent circuit model of the present paper can be considered as a preferable substitute for the time consuming FEM and approximated analytical method built on Maxwell’s Equations in particular when required to be applied for a design optimization problem.
Keywords: Finite Elements Method, Flux Density, Maxwell’s Equations, Nonlinear Magnetic Equivalent Circuit, Permanent Magnet Linear Synchronous Motor.

Dejan M. Petković, Milica D. Radić
Generalization of Helmholtz Coil Problem
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DOI: 10.2298/SJEE1503375P
Abstract: The primary intent of this work is to propose a simple analytical method for designing coil systems for homogeneous and gradient magnetostatic field generation. Coil system consists of two identical coaxial (regular) polygonal current loops. In the space between the loops, there is nearly homogeneous or nearly linear distribution of the magnetic field along the axes depending on the currents' direction. First, we derived a suitable, simple and general expression for the magnetic field along the axes due to a polygonal current loop. We emphasize the importance of the role of this expression for further analysis. The total on-axes magnetic field is the result of superposition of the magnetic fields that each loop generates separately. The proper distance between the loops and the current orientation make the system to become either Helmholtz coil or anti-Helmholtz coil. In this paper we give exact, analytical and general expression for this optimal distance that provides the magnetic field to be homogeneous (linear) as much as possible. We based our study on Taylor series expansion of the total magnetic field, demanding that the first contaminating term must be canceled, in both, symmetric and asymmetric case.
Keywords: Analytical models, Magnetic fields, Taylor series, Polygonal coils.

©2015 Serbian Journal of Electrical Engineering