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Step-Up Asymmetrical Nine Phase Delta-Connected Transformer for HVDC Transmission
Ammar, Arafet Ben,Ammar, Faouzi Ben The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.6
In order to provide a source for nine phases suitable for 18-pulse ac to dc power, this paper proposes a new structure for a step-up asymmetrical delta-connected transformer for converting three-phase ac power to nine-phase ac power. The design allows for symmetry between the nine output voltages to improve the power quality of the supply current and to minimize the THD. The results show that this new structure proves the equality between the output voltages with $40^{\circ}-{\alpha}$ and $40^{\circ}+{\alpha}$ phase shifting and produces symmetrical output currents. This result in the elimination of harmonics in the network current and provides a simulated THD that is equal to 5.12 %. An experimental prototype of the step-up asymmetrical delta-autotransformer is developed in the laboratory and the obtained results give a network current with a THD that is equal to 5.35%. Furthermore, a finite element analysis with a 3D magnetic field model is made based on the dimensions of the 4kVA, 400 V laboratory prototype three-phase with three-limb delta-autotransformer with a six-stacked-core in each limb. The magnetic distribution flux, field intensity and magnetic energy are carried out under open-circuit operation or load-loss.
Step-Up Asymmetrical Nine Phase Delta-Connected Transformer for HVDC Transmission
Arafet Ben Ammar,Faouzi Ben Ammar 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.6
In order to provide a source for nine phases suitable for 18-pulse ac to dc power, this paper proposes a new structure for a step-up asymmetrical delta-connected transformer for converting three-phase ac power to nine-phase ac power. The design allows for symmetry between the nine output voltages to improve the power quality of the supply current and to minimize the THD. The results show that this new structure proves the equality between the output voltages with 40°- α and 40°+ α phase shifting and produces symmetrical output currents. This result in the elimination of harmonics in the network current and provides a simulated THD that is equal to 5.12 %. An experimental prototype of the step-up asymmetrical delta-autotransformer is developed in the laboratory and the obtained results give a network current with a THD that is equal to 5.35%. Furthermore, a finite element analysis with a 3D magnetic field model is made based on the dimensions of the 4kVA, 400 V laboratory prototype three-phase with three-limb delta-autotransformer with a six-stacked-core in each limb. The magnetic distribution flux, field intensity and magnetic energy are carried out under open-circuit operation or load-loss.
Design and Implementation of a New Multilevel DC-Link Three-phase Inverter
Ammar Masaoud,Hew Wooi Ping,Saad Mekhilef,Ayoub Taallah,Hamza Belkamel 전력전자학회 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.2
This paper presents a new configuration for a three-phase multilevel voltage source inverter. The main bridge is built from a classical three-phase two-level inverter and three bidirectional switches. A variable DC-link employing two unequal DC voltage supplies and four switches is connected to the main circuit in such a way that the proposed inverter produces four levels in the output voltage waveform. In order to obtain the desired switching gate signals, the fundamental frequency staircase modulation technique is successfully implemented. Furthermore, the proposed structure is extended and compared with other types of multilevel inverter topologies. The comparison shows that the proposed inverter requires a smaller number of power components. For a given number of voltage steps N, the proposed inverter requires N/2 DC voltage supplies and N+12 switches connected with N+7 gate driver circuits, while diode clamped or flying capacitor inverters require N-1 DC voltage supplies and 6(N-1) switches connected with 6(N-1) gate driver circuits. A prototype of the introduced configuration has been manufactured and the obtained simulation and experimental results ensure the feasibility of the proposed topology and the validity of the implemented modulation technique.
AMMAR BIN YOUSAF,Muhammad Imran,MAJID KHAN,Muhammad Usman,MUHAMMAD ASGHAR JAMAL 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2014 NANO Vol.9 No.8
The infuence of particle size on density, ultrasonic velocity and viscosity of magnetite nanofuids have been determined at (298.15 K, 303.15 K, 308.15 K and 313.15 K). Two diferent sized nanoparticles (commercially procured D=20–30 nm and synthesized D=9± 3 nm in the laboratory by co-precipitation method) were dispersed in a citric acid base fuid. The desired parameters have been experimentally determined by loading diferent concentrations of nanoparticles. It has been found that the infuence of particle size and temperature on measured physical parameters (density, ultrasonic velocity and viscosity) is not negligible and can also be taken into account in any practical application. The analyzed physical parameters can describe qualitatively and quantitatively the particle size distribution of nanofuids at a specifc temperature. Results are interpreted in terms of particle–particle and particle–fuid interactions.
Effect of Four Flavonoids on Blood Glucose of Rats
Ammar, Nagwa M.,Al-Okbi, Sahar Y. The Pharmaceutical Society of Korea 1988 Archives of Pharmacal Research Vol.11 No.2
The effects of aglycones moring and quercetin and their corresponding glycosides quercitrin and rutin were studied on the blood glucose levels of rats. Quercetin and quercetrin caused hypoglycaemia in rats while rutin and morin showed almost no difference. Quercetin, which showed 50% pronounced hypoglycaemic effects, reduced significantly the blood glucose level of alloxan diabetic rats.
The Effect of Inflation on Performance
Ammar Yaser ALMANSOUR,Haitham Mohammad ALZOUBI,Bashar Yaser ALMANSOUR,Yaser Mansour ALMANSOUR 한국유통과학회 2021 The Journal of Asian Finance, Economics and Busine Vol.8 No.6
This paper aims to investigate the effect of inflation trends on the performance of the banking sector in Jordan., with data from five Jordanina listed banks in Amman Stock Exchange over the period of 2009–2019. The performance indicators employed in this study are return on assets, return on investment, and margin of net interest. Our empirical strategy for this quantitative approach employ regression analysis to explore th influential of inflation on banks’ performance. The results of descriptive statistics show that the banks’ performance in Jordan has increased gradually during the period 2015 to 2018, meaning that banking sector had performed of this study effeciantly during the period of study regardless of the increasing of inflation rate in the country. Generally, our results show that there is a strong and negative relationship between inflation rate and banks’ performance. In addition, the results show that the Banks’ performances are significantly affected by inflation. Interested parties may pay attention to other macroeconomic variables to investigate the impact of the macroeconomic factors on Banks’ performance. Future research shall consider not only bankin sector but other sectors in the financial market.
A CONVERGENCE RESULTS FOR ANTIPLANE CONTACT PROBLEM WITH TOTAL SLIP RATE DEPENDENT FRICTION
AMMAR, DERBAZI The Korean Society for Computational and Applied M 2021 Journal of applied mathematics & informatics Vol.39 No.5
In this work, we present the classical formulation for the antiplane problem of a eletro-viscoelastic materialswith total sliprate dependent friction and write the corresponding variational formulation. In the second step, we prove that the solution converges to the solution of the corresponding electro-elastic problem as the viscosity converges to zero.
A Class of Bivariate Linear Failure Rate Distributions and Their Mixtures
Ammar M. Sarhan,A. El-Gohary,A. H. El-Bassiouny,N. Balakrishnan 한국신뢰성학회 2009 International Journal of Reliability and Applicati Vol.10 No.2
A new bivariate linear failure rate distribution is introduced through a shock model. It is proved that the marginal distributions of this new bivariate distribution are linear failure rate distributions. The joint moment generating function of the bivariate distribution is derived. Mixtures of bivariate linear failure rate distributions are also discussed. Application to a real data is given.