Simulation and Experimental Research of Magnetic Field Produced by Permanent Magnet Used in Magnetic Localization
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The mathematical model of magnetic field produced by the permanent magnet is a key problem on magnetic localization of micro-medical devices in human body.Magnetic dipoles model and equivalent magnetic monopoles model are two often used models for obtaining static magnetic field distribution.The two models were used to simulate the magnetic field of cylinder magnet used in the drug delivery capsule.The calculation results of the two models are very close when the distance between the field point and the magnet is larger as 10 times of the magnet's size.The real experiments on the experimental device approved the simulation results,which mean that the magnetic dipoles model is suitable for magnetic localization of micro-medical devices in human body when the distance between the magnet and the magnetic sensor is larger as 10 times of the magnet's size.Keywords:
Force between magnets
Dipole magnet
Electropermanent magnet
Pole piece
Electrodynamic suspension
Electromagnet
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The paper presents the magnetic field calculation of permanent magnets, homogeneously magnetized in known direction. Method used in the paper is based on a system of equivalent magnetic dipoles. The results that are obtained using this analytical method are compared with results obtained using FEMLAB software. Magnetic field and magnetic flux density distributions of permanent magnet are shown in the paper.
Force between magnets
Dipole magnet
Electromagnet
Electropermanent magnet
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To solve the conflict between separation space and magnetic field intensity, an original magnetic circuit structure system of permanent magnet magnetic filter is designed by utilizing multi-dimensional magnet extrusion technologies, with multi-block NdFeB magnets of different structures and magnetization directions. The inside diameter of the ring magnets and ring soft iron is taken as separating space. To inspect the distribution of the magnetic field characteristics of magnetic circuit system, mathematical model is established, and the designed magnetic circuit system is simulated, taking advantage of the electromagnetic software Magnet. The simulation results show that a larger separating space and higher background magnetic density can be achieved simultaneously by means of the organic magnetic circuit system design, when the thickness of ring soft iron is 4mm and the diameter ratio (outside diameter to the diameter) of ring magnets is 10/3. The highest magnetic induction intensity of 29.2 mm separating space is 1.5T, which provides the basis for permanent magnet magnetic circuit design.
Neodymium magnet
Magnetic circuit
Pole piece
Electromagnet
Magnetic separation
Electropermanent magnet
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Problems of obtaining a homogeneous magnetic field in a spectrometer magnet are considered. The 0.15-T magnetic field in a 57-mm gap is produced by means of permanent SmCo/sub 5/ magnets. Results of calculations and measurements of the magnetic field are presented. On the basis of these results the dimensions and location of ferromagnetic shunts, correcting the magnetic field, have been calculated.< >
Dipole magnet
Force between magnets
Electropermanent magnet
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Electropermanent magnet
Magnetostatics
Pole piece
Halbach array
Force between magnets
Electromagnet
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In this paper, the three-dimensional magnetic field created by non-periodic magnet arrays is calculated analytically. The analytical expression of magnetic field is derived by using magnetic charge model. The influence of ferromagnetic boundaries is formulated with image method. Finally, we compare the results determined by analytical calculation to those from finite element simulation.
Force between magnets
Electropermanent magnet
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To verify the rationality of the magnetic field equivalent of adjacent magnets which have the same properties as a single magnet,a calculation model for the magnetic field of adjacent magnetized magnets is established based on the theory of circular-current magnet.The objective function is determined according to the minimum absolute modulus error between the magnetic field of adjacent magnetized magnets and that of equivalent single magnet at identical points.The genetic pattern search algorithm is used to obtain the inversion parameters.The results show that the long-distance magnetic field of the fitting single-magnet is identical to that of adjacent magnets,the relative error of magnetic flux density modulus decreases as the spherical radius increases,and the relative error of the same sphere initially increases and then decreases with an increase in field angle.Furthermore,the relative error has no relation with the magnetic anisotropy and the absolute length of magnet unit.Studies verify the rationality of combined magnetic field calculation,which can provide a theoretical basis for merging units and an evaluation criterion for fitting error estimates as far as the numerical simulation of magnetic anomaly induced by latent ferromagnetic objects is concerned.
Force between magnets
Dipole magnet
Electropermanent magnet
Electromagnet
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Lorentz force evaluation (LFE) is a technique to reconstruct defects in electrically conductive materials. The accuracy of the forward and inverse solution highly depends on the applied model of the permanent magnet. The resolution of the technique relies upon the shape and size of the permanent magnet. Furthermore, the application of an existing forward solution requires an analytic integral of the magnetic flux density. Motivated by these aspects, we propose a magnetic dipoles model (MDM), in which the permanent magnet is substituted with an assembly of magnetic dipoles. This approach allows modeling of magnets of arbitrary shape by appropriate positioning of the dipoles, and the integral can be expressed by elementary mathematical functions. We apply the MDM to cuboidal-shaped and cylindrical-shaped magnets and evaluate the obtained magnetic flux density by comparing it to reference solutions. We consider distances of 2-6 mm to the permanent magnet. The representation of a cuboidal magnet with 832 dipoles yields a maximum error of 0.02% between the computed magnetic field of the MDM and the reference solution. Comparable accuracy for the cylindrical magnet is achieved with 1890 dipoles. In addition, we embed the MDM of the cuboidal magnet into an existing forward solution for LFE and find that the errors of the magnetic flux density are partly compensated by the forward calculations. We conclude that our modeling approach can be used to determine the most efficient MDMs for LFE.
Force between magnets
Dipole magnet
Lorentz force
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A novel method to control a magnetic field distribution in a magnet is devised with use of inter-poles made of anisotropic magnet material. One can generate a gradient field in a constant gapped magnet with this technique; the effective length of the magnet can be constant, independent of the entrance position. Such a magnet can have not only constant gap but also smaller fringing field compared with a conventional one that controls its field distribution by changing the gap height
Constant (computer programming)
Electropermanent magnet
Force between magnets
Pole piece
Position (finance)
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The permanent magnet is considered as a component for changing the form of energy, and a brief review of the basic physics of the permanent magnet is included with emphasis on the nature of the magnetization process and how the permanent magnet functions in establishing external magnetic field energy. Presently availabIe characteristics of permanent magnets and future possibilities for improving the efficiency of the permanent magnet are discussed as well as the relationships between audio device performance and the unit properties of permanent magnets. In using the permanent magnet, the choice of unit properties, volume, geometry, and magnetic circuit arrangement greatly influence the end performance and efficiency of audio devices. As an aid in exploiting the optimum combination of these variables an electrical analog system using lumped constants is introduced. Data on leakage permeance are presented for the more widely used permanent magnet arrangements in audio work. The analog technique is of general interest from the viewpoint of understanding the energy relationships involved in the efficient application of the permanent magnet and as an aid in predicting permanent magnet performance on a firm engineering basis.
Electropermanent magnet
Permeance
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Magnetic dipole model is significant to calculate the magnetic strength of the magnet source. However, a restriction is that the distance from the testing position to the magnet's position must be much farther than the size of the magnet. The magnetic dipole model is not suitable for the near-filed around the magnet. Here, we propose a modified method for the correction of the near-field by introducing some coefficients to correct the magnetic dipole model. We divide the magnet's field into several regions according to the distance respect to the magnet size. We carried out experiments to measure the magnet's field, and then searched the suitable coefficients for each region to minimize the errors which between the measurements of magnetic strength and the presumed model values. In this paper, we investigated the magnetic field distribution for three types of magnets, Hollow Cylindrical Magnet Magnetized in Axially, Filled Cylindrical Magnet Magnetized in Axially and Hollow Cylindrical Magnet Magnetized in Radial. We use the modified magnetic dipole model to calculate the magnetic strength distribution for these magnets. Experimental results show that the modified method is effective to improve the accuracy of the magnet's near-field model.
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