Top PDF Permanent magnet structure for generation of magnetic fields

Permanent magnet structure for generation of magnetic fields

Permanent magnet structure for generation of magnetic fields

A permanent magnet structure for maximizing the flux density per weight of magnetic material comprising a hollow body flux source for generating a magnetic field in the central gap of the hollow body, the magnetic field having a flux density greater than the residual flux density of the hollow body flux source. The hollow body flux source has a generally elliptic-shape, defined by unequal major and minor axis. These elliptic-shaped permanent magnet structures exhibit a higher flux density at the center gap while minimizing the amount of magnetic material used. Inserts of soft magnetic material proximate the central gap, and a shell of soft magnetic material surrounding the hollow body can further increase the strength of the magnetic field in the central gap by reducing the magnetic flux leakage and focusing the flux density lines in the central gap.
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Generation of magnetic fields by large-scale vortices in rotating convection

Generation of magnetic fields by large-scale vortices in rotating convection

In summary, we have proposed a new self-consistent dynamo mechanism to explain the generation of system-size magnetic fields by turbulent rotating convection. The dynamo involves two steps: the formation of LSVs from small-scale convective flows, and the generation of large- scale magnetic fields by the action of the LSVs. The large-scale fields concentrate in the shear layers surrounding the LSVs and are essentially horizontal. The dynamo operates for small Pm (i.e. moderate Rm in our simulations, where Re is roughly constant), below the threshold for small-scale dynamo action. The competition between the generation of large-scale magnetic fields in the presence of LSVs, which leads to the amplification of small-scale magnetic field by the convective flows, and the subsequent suppression of the LSVs by these small-scale fields, yields the fluctuating behavior of this dynamo. Above the small-scale dynamo threshold, the small-scale magnetic field acts on the convective flows so as to prevent the formation of LSVs. In our numerical model, at Ek = 5 × 10 − 6 , this threshold occurs for Pm ≥ 1, i.e. Rm ≥ 765.
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Permanent magnet array for the magnetic refrigerator

Permanent magnet array for the magnetic refrigerator

Usually the magnetic refrigerant materials are either packed in a magnetocaloric bed as small spheres 6 attached around a disk as a ribbon 7 or separated in a pile of thin, equally spaced sheets. 8 Along with a large MCE magnitude, a strong applied magnetic field is critical to the efficiency of MR. The simplest permanent magnet design would be to place two rectangular-shaped permanent magnets parallel to each other separated by a certain distance, but this does not provide the necessary field strength for MR. 7 To enhance the magnetic flux density, soft magnetic material with a high permeability can be attached to both ends of the permanent magnets, therefore becoming a yoke-shaped permanent magnet. 8 These are easily fabricated but the generation of magnetic fields well above the remanence of the permanent magnet material is difficult.
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Design and Optimization of a Permanent Magnet Rotating Machine for Power Cooling Generation

Design and Optimization of a Permanent Magnet Rotating Machine for Power Cooling Generation

From the definition of MCE, it is clear that MR generator operates by submitting an MCE material to a varying magnetic field between a high level and a low level with ∆B = B high − B low as shown in Fig. 2. This paper presents the design and optimization of a rotating permanent magnet machine for cooling power generation by studying the influence of different factors on its performance using the classical parametric method and the statistical design of experiment method. Both electromagnetic and thermal studies are performed. Electromagnetic computations are undertaken to maximize the ∆B in order to get the best MR performance (temperature span and cooling power) and to limit mechanical efforts (forces and torque). Furthermore, the conducted thermal study aims to evaluate the cooling performance of such machines.
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Performance Analysis of Composite Magnetic Circuit Permanent Magnet Wind Generator

Performance Analysis of Composite Magnetic Circuit Permanent Magnet Wind Generator

In order to reduce the starting wind speed of the wind wheel and improve the efficiency of the wind wheel, this paper proposes a new type of composite magnetic circuit permanent magnet generator, which changes the relation- ship between the magnetic induction intensity and the air gap by changing the structure of the main magnetic circuit. The structure greatly improves the air gap sensitivity of the generator, which makes the structural design of the permanent magnet generator easier to implement. Finally, the effectiveness and feasibility of the method are verified by simulation.
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Effect of Rotor Eccentricity Faults on Noise Generation in Permanent Magnet Synchronous Motors

Effect of Rotor Eccentricity Faults on Noise Generation in Permanent Magnet Synchronous Motors

in transportation. However, the operation of theses motors is accom- panied by unavoidable production of noise especially in the presence of faults which are caused by tolerance in manufacture and assembly. Faults such as eccentricities causes a uniform air gap, corresponding non uniform air gap magnetic field and unbalanced magnetic force on stator producing noise and vibrations. Several works was published in last years about noise and vibration of PM motors [1, 3, 4], however, less research has been observed in vibroacoustic behavior of these mo- tors in relation with eccentricities faults [2]. Authors in [2] demonstrate that eccentricities can contribute to the generation of force with low mode number; however the model is based on a simple calculation of mechanical and acoustic quantity and the authors did not indicate how to validate experimentally the model of eccentricity. The aim of this research is to consider the effect of eccentricities faults on the noise radi- ated from the permanent magnet machine, this faults are characterized by a signature in the motor sound power level spectrum. For this pur- pose an analytical electromagnetic vibroacoustic approach to calculate the sound power level radiated from the PM motor is presented. The effect of eccentricity is introduced through the expression of the rela- tive permeance. The analytic approach adopted in this work consider that the magnetic flux density in the air gap of PMSM machine is the product of magnetic flux density generated by rotor magnet (or sta- tor winding) and the relative permeance which take into account the effect of slots [6, 7], the model calculates also the natural frequency of the stator and frame, stator yoke and frame displacements correspond- ing to the frequency of forces, and noise in the surrounding medium. All parts of the analytical model are validated by FEM simulations, this allows us to adjust and improve the model. The paper propose also a technique to validate the model of eccentricity experimentally, for this purpose the rotor is unbalanced by mounting a slotted disk on the shaft of the PMSM.
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Magnetic Properties of Mechanically Milled Sm Co Permanent Magnetic Materials with the TbCu7 Structure

Magnetic Properties of Mechanically Milled Sm Co Permanent Magnetic Materials with the TbCu7 Structure

using the Scherrer formula. Scanning electron microscopy (SEM) measurements were performed to study the morphol- ogy of the samples. Magnetic measurements at 300 K were performed using a vibrating sample magnetometer (VSM) with a maximum applied field of 2 T by fixing the samples in wax. Thermomagnetization (TM) measurements were per- formed in Ar atmosphere using a Perkin Elmer thermogravi- metric analyzer (TGA) and a small horse shoe magnet with a field strength of 4 mT.

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No Load Performance of a Novel Synchronous Permanent Magnet Generator with Soft Magnetic Composite

No Load Performance of a Novel Synchronous Permanent Magnet Generator with Soft Magnetic Composite

Direct drive generator (DDG) are gaining more and more attention. Due to gearless functioning they reduce the maintenance and operational costs. [9] Generators with permanent magnet excitation have special place among DDGs. Caricchi and coauthors proposed a simple disk shape stator without any slot, and put permanent magnets on the stator disk directly. Although this structure is easy to construct, but due to the created comparatively large air gaps reduced the efficiency of the generator. [10] In this research we constructed our recently proposed novel axial flux synchronous permanent magnet (AFSPM) generator. [11] This machine has single stator and double rotors. Finally, after several different structure which tried, we reached to this present design for a simpler stator segments which are both easy to take from the mold and avoiding any complicated mold for pressing the SMC powder. Permanent magnets or located between the stator segments which is depicted in the Figure 1. The windings are placed on the middle, part of the drawing, or on the stator.
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Investigative study of a novel permanent magnet flux switching machine employing alternate circumferential and radial permanent magnet

Investigative study of a novel permanent magnet flux switching machine employing alternate circumferential and radial permanent magnet

polarity is being reversed from one magnet to another (Hoang et al. 1997). The stator armature winding consists of concentrated coils and each coil being wound around the stator tooth formed by two adjacent laminated segments and a magnet. Similarly, all the armature phases employ the similar winding configuration and embedded in the stator core to form 12 winding slots. In this revision, the salient pole rotor is similar to that of switch reluctant machines (SRMs), which is more robust and suitable for high speed applications. The main drawbacks of these types of motors are the magnetic flux leakage at the outmost tip of PM which limits the distribution of flux and also separated stator structure from one segment to another - that is hardly to be fabricated and assembled.
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Analytical Modeling of Magnetic Field Distribution in Inner Rotor Brushless Magnet Segmented Surface Inset Permanent Magnet Machines

Analytical Modeling of Magnetic Field Distribution in Inner Rotor Brushless Magnet Segmented Surface Inset Permanent Magnet Machines

In [10], the 1D airgap magnetic fields of multiple multilayer 2D finite element simulations are combined to a 2D airgap magnetic field using static simulations. The introduced multilayer-2D - 2D coupled model is used to study the effect of segmentation on the eddy- current loss in the permanent magnets of an axial-flux PM machine simulating different segmentation grades. The axial segmentation of the PMs is employed to cut off the eddy-current axial paths in axial flux permanent magnet motor [11]. A nodal method based network-field coupled multislice time-stepping finite element method (TS-FEM) is proposed to analyze the steady-state and dynamic characteristics of the high-speed PM machine. Segmentation of magnets was proposed to reduce magnet eddy current loss, and finally a new structure based on segmentation was proposed to optimize the eddy current loss [12].
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Application of Halbach magnet array in designing a permanent magnet synchronous machine

Application of Halbach magnet array in designing a permanent magnet synchronous machine

rotation of the shaft to produce mechanical energy this energy can then be converted into electrical energy by using a generator [5]. At present there are two generally used configurations of wind turbines which are horizontal-axis and vertical-axis turbines. But the most common one used is the horizontal-axis type this is because in this case the rotating blades are in parallel to the wind stream. In horizontal axis wind turbines, the rotating axis is parallel to the ground. On the other hand, in a vertical wind turbine the rotating axis is perpendicular to the ground. Horizontal axis can produce a lot more energy compared to the vertical axis wind turbines mainly because of the size of the propellers. But both these designs have their application for small scale application a horizontal axis turbine is recommended but for electricity generation in power plants the best choice would be the horizontal axis turbine [6]. In a typical turbine design the blades are connected to an axle which is connected to a gear box. This gearbox steps up the rotational speed of the shaft from the propeller to the shaft that goes inside the generator because to produce electricity high rotational speed is required. The speed of the generator can vary causing fluctuation in the electricity produced due to unpredictable wind speed. Therefore, to overcome this problem a constant speed turbine should be used that can adjust to the extreme conditions. A generator is a device that converts mechanical energy to electrical energy. The generator does not create electricity it simply converts the mechanical energy acquired from an external source into electrical energy. Basically Inside an electrical generator either AC or DC the operation depends upon the Faraday’s magnetic induction principle. Inside a generator the coil is rotated by an external force this motion cuts the flux generated by the magnet
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Permanent Magnet DC Motor

Permanent Magnet DC Motor

Rotating machines such as electrical motors and generators (or alternators) are found in almost every sector of the industry. The basic principles of operation of rotating machines have been known for almost two centuries. Rotating machines operate due to the interaction between magnetic fields and current-carrying conductors, and are split into two basic categories: motors and generators. Permanent magnet dc motors are rotating machines that operate using direct current (i.e., they are dc powered). They can be used as either generators or motors. Permanent magnet dc motors are rugged components that are easy to connect and require little maintenance. They are found in a variety of applications, such as battery charging, small electric vehicles, windmill technology, mobility scooters, pumps, machine tools, kitchen appliances, optical equipment, etc.
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Magnetic Field Produced by a Tile Permanent Magnet Whose Polarization Is Both Uniform and Tangential

Magnetic Field Produced by a Tile Permanent Magnet Whose Polarization Is Both Uniform and Tangential

Abstract—This paper presents the exact 3D calculation of the magnetic field produced by a tile permanent magnet whose polarization is both tangential and uniform. Such a calculation is useful for optimizing magnetic couplings or for calculating the magnetic field produced by alternate magnet structures. For example, our 3D expressions can be used for calculating the magnetic field produced by a Halbach structure. All our expressions are determined by using the coulombian model. This exact analytical approach has always proved its accuracy and its usefulness. As a consequence, the tile permanent magnet considered is represented by using the fictitious magnetic pole densities that are located on the faces of the magnet. In addition, no simplifying assumptions are taken into account for calculating the three magnetic field components. Moreover, it is emphasized that the magnetic field expressions are fully three-dimensional. Consequently, the expressions obtained are valid inside and outside of the tile permanent magnet, whatever its dimensions. Such an approach allows us to realize easily parametric studies.
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Sensorless Permanent Magnet Drive Design

Sensorless Permanent Magnet Drive Design

During the electromagnetic machine, the electrical power converter and the software based control design process a lot of high sophisticated simulations take place in order to verify the desired performance behavior in advance [3]. The applied Finite Element method with directly coupled exter- nal electrical circuits is very beneficially for those tasks [4]. It takes implicit account of important geometric and crucial nonlinear magnetic properties of the machine, as well as the converter topology, which mainly govern the relevant drive performance aspects [5,6]. Moreover, the inclusion of basic control features within the circuit approach allows the simulation of the complete drive system in advance. A deeper insight into the 4.5 kW permanent magnet machine and the according power converter with the implemented control algorithm is given in Fig. 2, where the typical interior permanent magnet structure as well as the DC-link capacitors of the power module are obvious. The
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Research on Magnetic Pole Shifting Equivalent Model of Interior Permanent Magnet Synchronous Servo Motor

Research on Magnetic Pole Shifting Equivalent Model of Interior Permanent Magnet Synchronous Servo Motor

Comparing Figure 7 (a) (b), it can be clearly seen that the amplitude of the cogging torque in the IPMSM is slightly larger than that of the CTEM. This situation is due to the symmetry of the IPMSM rotor structure, the q axis magnetic circuit is wider, resulting in relatively small magnetoresistance, thereby reducing the cogging torque. But after the magnetic pole is shifted, the q axis magnetic circuit becomes narrower, magnetic resistance becomes larger, resulting in cogging torque becomes larger.

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A Novel Double-Stator Permanent Magnet Generator Integrated with a Magnetic Gear

A Novel Double-Stator Permanent Magnet Generator Integrated with a Magnetic Gear

Abstract—This paper presents a double-stator permanent magnet generator (DSPMG) integrated with a novel magnetic gear structure which is proposed to be used as a direct drive generator for low speed applications. Torque transmission is based on three rotors consisting of prime permanent magnet poles on the middle rotor and field permanent magnet poles on the inner and outer rotors, respectively. The proposed machine combines the function of a triple rotor magnetic gear and electrical power generator. The operating principle of the generator is discussed, and its performance characteristics are analyzed using 2-dimensional finite-element method (2D-FEM). Analysis results about its magnetic gear ratio, transmission torque, cogging torque and electrical power performance are reported. The 2-D finite element analysis results verify the proposed generator design.
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Magnetic Field Created by a Uniformly Magnetized Tile Permanent Magnet

Magnetic Field Created by a Uniformly Magnetized Tile Permanent Magnet

Abstract—This paper presents a general analytical formulation for calculating the three-dimensional magnetic field distribution produced by Halbach structures with radial or axial polarization directions. Our model allows us to study tile permanent magnets of various magnetization directions and dimensions. The three magnetic field components are expressed in terms of analytical and semi-analytical parts using only one numerical integration. Consequently, the computational cost of our model is lower than 1 s for calculating the magnetic field in any point of space. All our expressions have been checked with previous analytical models published in the literature. Then, we present two optimized permanent magnet structures generating sinusoidal radial fields.
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Analytical Expression of the Magnetic Field Created by a Permanent Magnet with Diametrical Magnetization

Analytical Expression of the Magnetic Field Created by a Permanent Magnet with Diametrical Magnetization

To eliminate/reduce the aforementioned error due to the approximation and improve the computation costs, this paper presents the work leading to an exact analytical expression of the magnetic field created by a diametrically magnetised cylindrical- and ring-shaped permanent magnet at any point of interest in 3D space, based on the Coulombian approach [30] which has been used to analytically model the magnetic fields created by arc-shaped permanent magnets with radial magnetization [31, 32], ring-shaped permanent magnets with axial and radial magnetization [24, 33], tile permanent magnets with radial magnetization [25] and tangential magnetization [34, 35]. The exact final model of the magnetic field was analytically derived, based on geometrical analysis without the need to calculate the scalar potential; and there was no approximation in the derivation steps. All three components of the magnetic field can be expressed using complete and incomplete elliptic integrals that are robust and their computational efforts are minimal [22, 36–39]. The accuracy of the developed analytical model was validated against 3D FEA results.
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The Study of Optimal Structure and Value of Dump Resistance in Direct Drive Permanent Magnet Synchronous Generators

The Study of Optimal Structure and Value of Dump Resistance in Direct Drive Permanent Magnet Synchronous Generators

2) Due to the buffering effect of the inductor, Chopper circuit with Buck Chopper circuit has more excellent results of low voltage ride through than that with only resistance. Accordingly, the use of direct-drive wind power generation system with dumping Buck circuit or dual resistance is more significant to the improvement of low voltage ride through capability.

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Permanent magnet actuation for magnetic bead-based DNA extraction

Permanent magnet actuation for magnetic bead-based DNA extraction

Molecular diagnostics is widely adapted in various fields such as disease detection and health monitoring. This method evaluates the nucleic acids (e.g., DNA, RNA, or a vari- ation of both) for human samples as well as bacteria or virus which are the causes of many diseases [1–6]. The process examines the nucleic acids to determine the status of diseases and investigate the agent responsible for the infections. Molecular diagnostics follows four basic steps of sample collection, gene extraction from the collected sample, gene amplification by polymerase chain reaction (PCR), and analysis. The gene ampli- fication step enables the diagnosis to be extremely accurate with high sensitivity and specificity.
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