Enhancing performance for three-phase induction motor by changing the magnetic flux density and core material using COMSOL

This paper presents a proposed design and analysis of a three-phase squirrel cage induction motor when changing of internal characteristic design for the three-phase induction motor. Two situations have been applied to enhancing the performance of the three-phase induction motor. The first situation has been implemented by changing the magnetic flux density (MFD) via the build of the six-phase for the same induction motor. The second situation has been implemented by changing core materials of the rotor part of the induction motor, like aluminum (AL) and cast iron (CI). The finite element method (FEM) has been used to analyze the rotor part, also to obtain the representation and simulation of the realty cylindrical rotor part of motor. The frequency domain (FD) analysis using to obtain the results within the environment of the COMSOL multiphysics 5.5 version.

Equivalent circuit of a ferrite-wound inductor in a wide frequency range (0 Hz – 500 MHz)

Based on the measured impedance of the inductors wound on various ferrite cores and with a different number of turns, an equivalent high frequency (0 Hz 500 MHz) circuit model was built. The equivalent circuit model was built taking into account the physical processes occurring in the inductor: effect of wire resistance, effect of core material, mutual effect of wire and core material. The attempt explaining why the frequency characteristics (modulus and phase) of the inductor complex impedance have such a character in a wide frequency band (up to 500 MHz) was made. It was shown that for constructing an equivalent circuit model (structure and parameters), measuring only the inductors resistance modulus is not enough. It is also necessary to measure the phase of the inductor complex resistance, which is ignored in many works on the synthesis of an e inductor equivalent circuit.

Ferrites and Nanocrystalline Alloys Applied to DC–DC Converters for Renewable Energies

The medium frequency transformer (MFT) with nanocrystalline alloys is quintessential in new DC–DC converters involved in various front-end applications. The center piece to achieve high-performance, efficient MFTs is the core. There are various options of core materials; however, no deep information is available about which material characteristics and design procedure combo are best to get high performance MFTs while operating at maximal power density. To provide new insights about interrelation between the selection of the core material with the compliance technical specifications, differently to other proposals, this research work aims to design and build, with the same methodology, two MFT prototypes at 20 kHz, with nanocrystalline and ferrite cores, to highlight power density, and overall performance and cost, as matching design criteria. As the experimental results show, a nanocrystalline core has the highest power density (36.91 kW/L), designed at 0.8 T to obtain low losses at 20 kHz, achieving an efficiency of 99.7%. The power density in the ferrite MFT is 56.4% lower than in the nanocrystalline MFT. However, regarding construction cost, the ferrite MFT is 46% lower, providing this a trend towards low-cost DC–DC converters. Finally, high power density in MFTs increases the power density of power DC–DC converters, which have relevant applications in fuel cell-supplied systems, renewable energies, electric vehicles, and solid-state transformers.

Experimental Analysis of Viscoelastic Properties of Room Temperature Vulcanized Silicone based Magnetorheological Elastomer

Magnetorheological Elastomers (MRE) endure a change in mechanical properties with the application of an externally applied magnetic field. It consists of an elastomeric matrix reinforced with ferromagnetic powdered particles. This paper focuses on the investigation of viscoelastic properties of Room Temperature Vulcanized (RTV) silicone based isotropic MRE in sandwich beam configuration by varying the volume percentage of Carbonyl Iron Powdered (CIP) reinforcement. Viscoelastic properties of the MRE core material were calculated by following the ASTM E756-05 standard. The magnetic field was applied by employing a Halbach array which was numerically analyzed using Finite Element Method Magnetics (FEMM). The magnetic field was varied up to 0.15 T. Loss factor and shear modulus were found to be strongly influenced by the percentage content of CIP. The loss factor and shear modulus of 30% MRE at 0.15 T were higher than other tested samples. The variation of natural frequency with respect to the addition of CIP was validated numerically using Modal analysis conducted in Hyperworks.

The Compressive Behavior and Crashworthiness of Cork: A Review

Cork, a natural material from renewable resources, is currently attracting increasing interest in different industrial fields because of its cellular structure and the presence of the flexible suberin as its main chemical component. In an agglomerated form, it proved to be a compelling product not only as a thermal and acoustic insulator, but also as core material in sandwich structures and as a liner or padding in energy absorbing equipment. From this perspective, the assessment of its compressive response is fundamental to ensure the right out-of-plane stiffness required to a core material and the proper crashworthiness in the safety devices. Considering the complex nature of cork and the resulting peculiar compressive response, the present review article provides an overview of this paramount property, assessing the main parameters (anisotropy, temperature, strain rate, etc.) and the peculiar features (near-zero Poisson’s ratio and unique dimensional recovery) that characterize it in its natural state. Furthermore, considering its massive exploitation in the agglomerated form, the design parameters that allow its compressive behavior to be tailored and the operating parameters that can affect its crashworthiness were assessed, reporting some potential industrial applications.

Peculiarities of Stratigraphic Distribution and Paleoecology of Jurassic Bivalve Mollusks of the Pre-Сarpathian Foredeep

Pre-Carpathian region is one of the oldest oil and gas producing regions of our country, which is attracting more and more attention of scientists. In the Outer zone of the Pre-Carpathian Foredeep, Jurassic deposits occur at considerable depths (up to 3,000 m), so we obtain almost all geological information about them exclusively during the study of core material selected during drilling. A comprehensive and detailed study of the Jurassic deposits of this zone during exploration drilling in the 1950s contributed to the discovery of the Kokhanivske and Sudovovyshnianske oil deposits and Rudkivske gas deposit, as well as a number of oil and gas manifestations. After that, the interest in the conditions of formation and stratification of Jurassic deposits increased. Researchers have begun to treat them as the promising objects for oil and gas exploration. Jurassic deposits in the Pre-Сarpathian Foredeep fill a single depression – the Stryi Jurassic deflection, covered by a thick layer of Cretaceous and Neogene rocks. The study of their geology and stratigraphy has acquired important applied and scientific significance, because stratigraphic research serves as a basis for clarifying the history of geological development of the region, performing tectonic constructions, reconstruction of paleogeographic and paleoecological conditions, comparison of productive horizons and specification of their stratigraphic position, search for new objects promising for hydrocarbons. Extremely rare finds of paleontological remains (which are not always well preserved) do not allow to unambiguously determining the age of the host rocks. It is still not always possible to clearly stratigraphically distinguish and correlate these rocks due to weak paleontological study and partial uncertainty in the interpretation of the geological structure of these strata. Despite the significant amount of research we have done, there are some debatable issues regarding the completeness of the section of these rocks and the presence of separate stratigraphic units in them. For many years, we have studied in detail and comprehensively bivalve mollusks found in the core of wells drilled in the Outer zone of the Pre-Carpathian Foredeep. As a result, the age of the host strata was specified and confirmed, as well as the thickness of individual stratigraphic units.

Determine the Optimum Efficiency of Transformer Cores Using Comparative Study Method

The transformer is one of the most discussed and important components of electrical power systems because of its reliability, durability and energy conversion capability. It is also useful in load sharing, which reduces system burden, but is also responsible for a sufficient number of losses, as it is used in different types of electric appliances that require voltage conversion. The no-load losses of transformers have gained much attention from research perspective because of its operating cost throughout its lifetime. Many studies were carried out to achieve the highest possible efficiency, decreasing certain losses by using different methods and materials. However, the local market in Pakistan is far behind in the field of efficient core material manufacturing of transformers, which is why consumers are unable to obtain efficient electric appliances. Due to these loss-making appliances, the overall residential load increases and the consumers are charged with heavy electricity bills. This proposed study discusses core losses, different core comparisons, T/F efficiency and advancement in the core material. To accomplish a core comparison, two locally available core materials are used to fabricate two different T/F, and some tests such as open-circuit and short-circuit tests are performed to discover their losses, thermal degradation, and output efficiencies.

Novel Reactive Flex Configuration in Kiwi Wing Foil Surfboard

The creation of an ideal surfboard is art. The design and construction depend on the individual surfer’s skill level and type of the required performance. In this research, four fuselage concepts were carefully explored to meet the following unique needs: lightweight, strong, and a fast-manufacturing process. The fuselages were manufactured by compression moulding using skin and core materials. The skin material was selected to be unidirectional (UD) carbon fibre, discontinuous carbon fibre (SMC) and Filava quadriaxial fibre impregnated with epoxy, while the core material was selected to be lightweight PVC foam. To assess the mechanical performance, three-point bending has been performed according to BS-ISO 14125 and validated using Finite Element Analysis (FEA) using Ansys software. As expected, the flexural test revealed that the UD carbon fibre fuselage was the strongest and SMC was the weakest, while large deflection was seen in Filava fibre fuselages before failure, showing great reactive flex that promotes projection during surfing. The experimental results show good agreement with FEA simulation, and the locations of the physical failure in the fuselage matches the location of maximum flexural stress obtained from FEA simulation. Although all fuselages were found to carry a surfer weight of 150 kg, including a factor of safety 3, except the SMC fuselage, due to shrinkage. The Filava fibre fuselages were seen to have a large deflection before failure, showing great flexibility to handle high ocean waves. This promotes the potential use of reactive flex in high performance sports equipment, such as surfing boards. A large shrinkage must be taken under consideration during compression moulding that depends on fibre orientation, resin nature, and part geometry.

OVERCOMING CHALLENGES IN VIRTUAL CLASSROOM TO MAINTAIN EFFECTIVE CLASSROOM MANAGEMENT AND CLASSROOM CULTURE: A CASE STUDY AT ONE VOCATIONAL SCHOOL

Effective classroom management supports the teacher classroom teaching profoundly. During Pandemic COVID 19 most classroom teachings are conducted in virtual classroom that have been greatly affected the way how teacher manage his or her own classroom. This causes some challenges for teachers in managing his or her virtual classroom. This study was conducted in the form of a case study in one vocational school in West Bandung region, West Java, Indonesia in which one English teacher was purposively selected as the participant of the research and one class consisted of 27 students. The objectives of this study are: (1) to find out the challenges of teacher in classroom management in virtual classroom (2) to find out what classroom management the teacher used in her virtual classroom. The researchers employed a qualitative case study which used classroom observation and teacher interview as main instrument. Data from classroom observation and interview transcript were analyzed according to the themes, coding and categorizing to answer the research questions. The results indicate that the teacher experienced many challenges in the virtual classroom, such as the students’ unreadiness to join the virtual class, internet connection problem, restricted time so that the teacher immediately taught the core material, students turned off the camera and sound, students learnt unattentively, less interaction and inappropriate class control. Some suggestions are given to the challenges occurred in their virtual classroom such as, by a) joining the virtual classroom earlier; b) checking the students’ attendance first; c) optimizing the teacher-students interaction during whilst- learning and post learning activity; and d) giving quizzes at the end of the lesson to make the students are more enthusiastic in learning. In this study, it is found that the teacher employed a combination of democratic and leisurely classroom management style. This finding leads to the point where a new style for virtual classroom management called Maye’s Conceptualization Model is proposed.