http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Loss Analysis of Nanocrystalline Cores for High Frequency Transformer in Power Electronics Circuits
Munir Muhammad Umair,Ehab Muhammad,Tawfik Mohamed Atef,Ahmed Ashraf,Park Joung-Hu 대한전기학회 2024 Journal of Electrical Engineering & Technology Vol.19 No.3
Nanocrystalline cores have a superior higher permeability, which makes them smaller size and weight compared to conventional cores. This makes nanocrystalline more suitable to many applications, such as electrical vehicles, EMI flters, so on. This paper compares power-conversion performance between nanocrystalline and conventional ferrite cores of similar volume. A 1 kW dual-active bridge converter is used for testing the transformers at 50–80 kHz. Theoretical losses are calculated from datasheets and compared with the experimental losses for both the nanocrystalline and ferrite. Results reveal that the theoretical and experimental losses match for ferrite transformer but there exists a signifcant diference in case of the nanocrystalline transformers. Further investigation is needed to explain this mismatch. Therefore, FEM analysis using COMSOL Multiphysics is performed. Due to the nonlinearity of the material, a homogenized anisotropic confguration is adopted. The experimental and FEM results suggest that the mismatch is possibly because of the circulating eddy currents between the ribbons, which must be taken into consideration during the modeling of the losses for nanocrystalline cores.
Wardah Anam,Munir Ashraf,Muhammad Bilal Qadir,Khurram Shehzad Akhtar,Sheraz Ahmad,Ali Afzal,Tehseen Ullah 한국섬유공학회 2019 Fibers and polymers Vol.20 No.12
In this research work, we have studied the dyeing behaviour of fabrics made from ring, rotor and MVS yarns. Thediscrete structure of respective yarns made by different spinning techniques have significant effect on dyeing behaviour offabrics. The fabrics were investigated for K/S values of polyester dyed, cotton dyed and polyester+cotton dyed fabrics andtheir colour fastness to crocking. The analysis of dyeing behaviour revealed that yarn manufacturing technique hassubstantial effect on the colour strength of their respective fabrics. Due to unique distribution of fibers within the crosssectionof yarn, the cotton dyed and polyester+cotton dyed fabrics made from MVS yarns exhibited better K/S values ascompared to other fabrics. The fabrics also exhibited a difference in colour fastness to crocking in dry and wet form. Thecolor fastness of fabrics to crocking in dry form were found higher than in wet form. The polyester dyed and polyester+cottondyed fabrics made from MVS yarns have shown higher color fastness to crocking.
Nasir Sarwar,Munir Ashraf,Muhammad Mohsin,Abdur Rehman,Ayesha Younus,Amjed Javid,Kashif Iqbal,Shagufta Riaz 한국섬유공학회 2019 Fibers and polymers Vol.20 No.11
Importance of multifunctional finishing of textiles is increasing day by day due to greater consumer demand. Cross-linker is one of the commonly used finishes agent to impart functionality in textiles. In this research work theperformance of the formaldehyde free carboxylic acid based eco-friendly cross-linkers; citric acid (CA) and maleic acid(MA) was enhanced by incorporating three different types of metal oxides nanoparticle (ZnO, MgO and CaO). Two differentfixation methods of pad-dry-cure with and without UV irradiation were used. ZnO along with CA and MA was found to bemost effective in increasing crease recovery performance of the cotton fabric followed by MgO while CaO was found to beineffective. Fabric tear strength was also improved by the incorporation of these nanoparticles. Additionally, incorporation ofthese nanoparticles exhibited improvement in the fabric handle and antimicrobial properties.
Muhammad Zaman Khan,Vijay Baheti,Munir Ashraf,Tanveer Hussain,Azam Ali,Amjed Javid,Abdur Rehman 한국섬유공학회 2018 Fibers and polymers Vol.19 No.8
In this research work, multifunctional cotton fabric comprising of UV protection, superhydrophobicity and antibacterial activity has been developed using facile pad-dry-cure method. In the first step, the concentration of repellent chemical has been optimized. Then, formulations containing nanoparticles of ZnO or TiO2 along with optimized concentration of repellent chemical and organic-inorganic binder have been applied to cotton fabric followed by the evaluation of functional properties. The surface morphology and elemental composition of treated fabric has been characterized through SEM and EDX, respectively. The treated samples have shown promising UV protection, superhydrophobicity and antibacterial properties durable upto 20 washing cycles.
Jung-Hwan Park,Kyoung-Tak Kim,Chun-Gu Lee,Mohamed Atef Tawfik,Muhammad Ehab,Muhammad Umair Munir,Ashraf Ahmed,Joung‑Hu Park 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.11
With the advancement of carbon material science, there have been attempts to apply carbon nanotubes in various engineering fields. In power electronics, application research has been conducted on using carbon nanotube (CNT) yarn in inductors, transformers, and motor windings, because CNT yarns show promising mechanical and electrical characteristics when compared with conventional conduction materials. This paper evaluates the feasibility of CNT yarn-based inductor applications with respect to higher-frequency power converter circuits, especially focusing on the ISM (Industry–Science–Medical) frequency range. Inductors are fabricated using two kinds of CNT yarns with different conductivity values. These inductors are compared with copper and lead coiled inductors, since they have a relatively high conductivity with respect to CNT yarns, and due to their popularity in the industry. The small-signal impedance data of each inductor according to the frequency variation are measured using a network analyzer, and the measurements were compared with a COMSOL simulation. One of the main results of this research is that the CNT yarn-based inductors were shown to have a better normalized AC resistance characteristic than the conventional conductor inductors, which have higher conductivity. It was found that CNT inductors have a similar AC resistance when compared to that of metallic conductors with nearly 1.85 times higher conductivity. A 100 W differential class-E resonant converter is implemented to test the inductors and to verify the small-signal measurement results. Efficiencies and thermal images are obtained at 6.78-MHz and 13.56-MHz ISM frequencies.