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1 – 10 of 217Ali Muhammad, Faisal Khan, Muhammad Yousuf and Basharat Ullah
The purpose of this paper is to modernize the generator system of wind turbine concept that not only improves the efficiency and power density but also reduces the system cost…
Abstract
Purpose
The purpose of this paper is to modernize the generator system of wind turbine concept that not only improves the efficiency and power density but also reduces the system cost making design simpler and less expensive, especially in large-scale production.
Design/methodology/approach
This paper presents a new permanent magnet transverse flux generator (PMTFG) for wind energy production. The key feature of its composition is the double armature coil in a semi-closed stator core. The main structural difference of the presented design is the use of double coil in the same space of semi-closed stator core and reduced number of stator pole pairs and rotor magnets from 12/24 to 10/20. 3D simulations are performed using finite element analysis (FEA) to measure induced voltage and magnetic field distribution at no load. The FEA is performed to quantify the change in flux linkage, induced voltage and output power as a function of different speeds and load current.
Findings
Results show that PMTFG with double coil configuration has improved electromagnetic performance in terms of flux linkage, induced voltage, output power and efficiency. The power density of 10/20 PMTFG with the double coil is 0.0524 KW/Kg, about an 18% increase compared to the conventional design.
Research limitations/implications
The proposed PMTFG is highly recommended for direct drive applications such as wind power.
Originality/value
Four models are simulated by FEA with single and double coil configuration, and load analysis is performed on all simulated models. Finally, results are compared with conventional PMTFG.
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Viktor N. Antipov, Anna V. Ivanova and Andrei D. Grozov
The purpose of this study is to investigate a novel rotor design model to improve the technical performance of a superconducting synchronous generator.
Abstract
Purpose
The purpose of this study is to investigate a novel rotor design model to improve the technical performance of a superconducting synchronous generator.
Design/methodology/approach
Superconducting synchronous generators with a modular rotating cryostat for a single coil of the superconducting winding instead of an old-style single cryostat in which all rotor components are cold are briefly discussed. Subsequently, a new method of cryostat arrangement in the magnetic system of a rotor is considered. Different options were compared for the cryostat placement. The advantages of the novel rotor design model are noted.
Findings
In the novel rotor design model, the leakage coefficient of the excitation winding decreases, and the air gap magnetic flux increases, which will save on a superconductor material.
Research limitations/implications
For the purposes of this investigation, a finite element study of flux distribution in the cross section of a superconducting synchronous generator with a 10 MW rating at 10 rpm was conducted, and the magnetic fluxes and air gap flux densities were obtained for different modes. For direct-drive superconducting synchronous generators with distributed winding and different pole numbers, the calculations of magnetic fluxes were carried out by calculating the magnetic conductivities.
Originality/value
A new method of the cryostat arrangement in the magnetic system of a rotor has been classified as an invention and was protected by a patent. This paper is directly applicable to the field of superconducting synchronous generators.
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The paper aims to analyze the behavior of the Galfenol rods under bending conditions that are employed in a vibration energy harvester by illustrating the spatial variations in…
Abstract
Purpose
The paper aims to analyze the behavior of the Galfenol rods under bending conditions that are employed in a vibration energy harvester by illustrating the spatial variations in stress and magnetic field.
Design/methodology/approach
This paper describes a 3‐D static finite element model of magnetostrictive materials, considering magnetic and elastic boundary value problems that are bidirectionally coupled through stress and field dependent variables. The finite element method is applied to a small vibration‐driven generator of magnetostrictive type employing Iron‐Gallium alloy (Galfenol).
Findings
The 3‐D static finite element modeling presented here highlights the spatial variations in magnetic field and relative permeability due to the corresponding stress distribution in the Galfenol rods subjected to transverse load. The numerical calculations show that about 1.1 T change in magnetic flux density is achieved which demonstrates the effectiveness of the inspected vibration‐driven generator in voltage generation and energy harvesting. The model predictions agree with the experimental results and are coherent with the magnetostriction phenomenon.
Originality/value
This paper fulfils the behavior analysis of Galfenol rods under transverse load that includes both compression and tension. The compressive and tensile stresses contributions to change in magnetic flux densities in the Galfenol rods were calculated by which the effectiveness of the inspected vibration‐driven generator in voltage generation and energy harvesting is demonstrated.
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The purpose of this paper is to introduce an aid for teaching transverse flux permanent magnet machines (TFPMs) with emphasis on their torque production.
Abstract
Purpose
The purpose of this paper is to introduce an aid for teaching transverse flux permanent magnet machines (TFPMs) with emphasis on their torque production.
Design/methodology/approach
The Lorentz force law is applied to fictitious current loops emulating the permanent magnets (PMs) mounted on the rotor according to different arrangements; the air gap flux density is created by the armature current.
Findings
Implemented in a master lecture on special AC machines, the proposed approach has revealed a renewed interest in electromagnetic fundamentals for pedagogical purposes. It makes simple the explanation of the principle of operation of a class of AC machines reputed by the complexity of their magnetic circuits. The latter incorporates axially stacked decoupled sub-circuits, one per phase generating alternating magnetic fields. More specifically, there is common air gap, shared by the machine phases, in which a rotating magnetic field is created by the superposition of the PM contribution and the armature one.
Research limitations/implications
Accounting for the complexity of the magnetic circuits and the three-dimensional (3D) flux paths characterizing TFPMs, a 3D finite element analysis (FEA) is required for the validation of the analytical predictions. Nevertheless, such a 3D FEA validation is far from being obvious to be carried on within a master lecture.
Originality/value
While the basis of Lorentz forces resulting from fictitious current loops emulating PMs has been considered in some referenced papers, its simple and pedagogical application to assess the torque production of several TFPM concepts represents the added value of the present paper.
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Jikai Si, Zuoguang Yan, Rui Nie, Shuai Xu, Chun Gan and Wenping Cao
To improve the power density and generation efficiency of the tubular permanent magnetic linear generators (TPMLGs) under realistic sea-stator condition, a TPMLG with 120° phase…
Abstract
Purpose
To improve the power density and generation efficiency of the tubular permanent magnetic linear generators (TPMLGs) under realistic sea-stator condition, a TPMLG with 120° phase belt toroidal windings (120°-TPMLG) for wave energy conversion is proposed in this paper.
Design/methodology/approach
First, the structure of the 120°-TPMLG is introduced and its operation principle is analyzed. Second, the design process of the 120°-TPMLG is described. Meanwhile, the finite-element models of the 120°-TPMLG and the TPMLG with traditional fractional pitch windings (T-TPMLG) are established based on the similar overall dimensions. Then, the electromagnetic characteristics of the 120°-TPMLG are analyzed, such as air gap flux density, back electromotive force and load voltage. Finally, a comparative analysis of the magnetic flux density, flux linkage, load and no-load performance of the two generators are conducted.
Findings
The result shows that the 120°-TPMLG has higher power density and generation efficiency than the T-TPMLG.
Originality/value
This paper proposes a TPMLG with 120° phase belt toroidal windings (120°-TPMLG) to improve the power density and generation efficiency.
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The purpose of this paper is to highlight the effect of combined heat and mass transfer characteristics of magnetohydrodynamic (MHD) free convection flow of an electrically…
Abstract
Purpose
The purpose of this paper is to highlight the effect of combined heat and mass transfer characteristics of magnetohydrodynamic (MHD) free convection flow of an electrically conducting Newtonian fluid on circular cylinder with uniform heat/mass flux, taking into consideration the effects of uniform transverse magnetic field and thermal radiation.
Design/methodology/approach
An analysis is performed to study the momentum, combined heat and mass transfer characteristics of MHD free convection flow past a circular cylinder surface under the effect of thermal radiation with uniform heat and mass flux. By using Lie group method, the infinitesimal generators of governing equations are calculated. Using the resulting generators for the boundary value problem, the equations are transformed into an ordinary differential system. Numerical solutions of the outcoming non‐linear differential equations are found by using a combination of a Runge–Kutta algorithm and shooting technique.
Findings
Application of a magnetic field normal to the flow of an electrically conducting fluid gives rise to a resistive force that acts in the direction opposite to that of the flow. This resistive force tends to slow down the motion of the fluid along the cylinder and causes increases in its temperature and concentration and hence the respective changes in the wall shear stress, local Nusselt and Sherwood numbers as the magnetic parameter, respectively are changed with various values of angle which is measured in degrees from the front stagnation point on the surface. It is noted that these coefficients reduced as the magnetic parameter increases. Also, the effect of thermal radiation works as a heat source and so the quantity of heat added to the fluid increases, therefore the local Nusselt number reduced as the radiation parameter increases.
Research limitations/implications
An analysis is performed to study the momentum, combined heat and mass transfer characteristics of MHD free convection flow of an electrically conducting Newtonian fluid on circular cylinder with uniform heat/mass flux with the effects of uniform transverse magnetic field and thermal radiation.
Practical implications
This paper provides a very useful source of coefficient of heat and mass transfer values for engineers planning to transfer heat and mass by using electrically conducting gases with uniform heat/mass flux.
Originality/value
The combined heat and mass transfer of an electrically conducting gases on free convection flow in the presence of magneto and thermal radiation effects are investigated and can be used by different engineers working on industry, geothermal, geophysical, technological and engineering applications.
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Cristian Demian, Raphael Romary, Gilles Vogt and Valentin Costan
The axial magnetic field occurs in the end-region of large turbo-generators is known to induce hot points or voltages between laminations, that may cause insulation breakdown and…
Abstract
Purpose
The axial magnetic field occurs in the end-region of large turbo-generators is known to induce hot points or voltages between laminations, that may cause insulation breakdown and thus stator faults.
Design/methodology/approach
It is important to dispose of simple methods for estimating the axial flux rapidly with regard to the operating point of the machine.
Findings
The authors provide a practical model of the axial magnetic field based on a simplified vector diagram. The parameters required to build the vector composition of the flux densities are assessed with a limited number of finite element method simulations of the whole end-region of the machine. These simulations were validated by an experimental test on a real turbo-generator. Then the axial flux density was simply estimated for various operating points.
Originality/value
The originality of the paper concerns the practical model of the axial magnetic field based on a simplified vector diagram.
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Renuganth Varatharajoo and Ralph Kahle
To compare the conventional reaction wheel and battery systems with the combined energy and attitude control system. The system mass, volume and power requirements are revealed…
Abstract
Purpose
To compare the conventional reaction wheel and battery systems with the combined energy and attitude control system. The system mass, volume and power requirements are revealed corresponding to the small satellite missions.
Design/methodology/approach
All the relevant system parametric equations are established. The system mass, volume and power are estimated accordingly for the conventional and the combined systems. Then, both systems are compared with respect to the typical small satellite missions.
Findings
The combined system outperforms the conventional system in most small satellite missions. However, there are some small satellite missions where the conventional systems are better in terms of the mass and volume budgets.
Research limitations/implications
This research work is exclusively for small satellites in the LEO orbits.
Practical implications
A reasonable information for sizing the combined energy and attitude control system is established. The system mass, volume and power budgets can be extracted from this research work.
Originality/value
The results provide an instant answer regarding the feasibility of the combined energy and attitude control system for small satellites.
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Ryoko Minehisa, Yasuhito Takahashi, Koji Fujiwara, Norio Takahashi, Masafumi Fujita, Kazuma Tsujikawa and Ken Nagakura
This paper aims to propose a homogenization method considering magnetic anisotropy for a magnetic field analysis of a turbine generator. To verify the validity of the proposed…
Abstract
Purpose
This paper aims to propose a homogenization method considering magnetic anisotropy for a magnetic field analysis of a turbine generator. To verify the validity of the proposed method, the effects of magnetic anisotropy and a space factor on a no-load saturation curve and no-load iron loss of the turbine generator are discussed.
Design/methodology/approach
The proposed method was derived from the combination of the homogenization of microscopic fields in a laminated iron core with the modelling of two-dimensional magnetic properties based on free energy. To verify the validity, the proposed method was applied to a finite-element analysis of a simple ring core model. Finally, a no-load saturation curve and iron loss of the turbine generator was investigated by using the proposed method.
Findings
The computational accuracy of the homogenization method considering magnetic anisotropy is almost the same as that of the detailed modelling of the laminated structure in the magnetic field analysis of the laminated iron core. Furthermore, it is clarified that magnetic anisotropy does not have a large influence on the no-load saturation curve of the turbine generator because of the large air gap. On the other hand, the space factor affects the shape of the no-load saturation curve.
Originality/value
This paper verifies the validity of the homogenization method considering magnetic anisotropy method and elucidates the effects of magnetic anisotropy and a space factor on no-load characteristics of the turbine generator.
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V. Fireteanu, T. Tudorache, A. Geri and G.M. Veca
This paper presents two numerical methods, which will be able to predict the temperature distribution in the thin moving conducting sheet, which is caused by the eddy‐current…
Abstract
This paper presents two numerical methods, which will be able to predict the temperature distribution in the thin moving conducting sheet, which is caused by the eddy‐current losses in transverse flux inductive heating devices (TFIH). The first method is based on a finite element calculation, while the second one is based on a circuit approach. The main aim of this paper is the validation of the circuit model by comparison with the more accurate and sophisticate finite element model. In addition, the results of both numerical models have also been compared with those obtained by experimental measurements.
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