Field Distribution Of Permanent Magnet Research Articles

Three-Dimensional Analytical Modeling of Axial-Flux Permanent Magnet Drivers

In this paper, the axial-flux permanent magnet driver is modeled and analyzed in a simple and novel way under three-dimensional cylindrical coordinates. The inherent three-dimensional characteristics of the device are comprehensively considered, and the governing equations are solved by simplifying the boundary conditions. The axial magnetization of the sector-shaped permanent magnets is accurately described in an algebraic form by the parameters, which makes the physical meaning more explicit than the purely mathematical expression in general series forms. The parameters of the Bessel function are determined simply and the magnetic field distribution of permanent magnets and the air-gap is solved. Furthermore, the field solutions are completely analytical, which provides convenience and satisfactory accuracy for modeling a series of electromagnetic performance parameters, such as the axial electromagnetic force density, axial electromagnetic force, and electromagnetic torque. The correctness and accuracy of the analytical models are fully verified by three-dimensional finite element simulations and a 15 kW prototype and the results of calculations, simulations, and experiments under three methods are highly consistent. The influence of several design parameters on magnetic field distribution and performance is studied and discussed. The results indicate that the modeling method proposed in this paper can calculate the magnetic field distribution and performance accurately and rapidly, which affords an important reference for the design and optimization of axial-flux permanent magnet drivers.

Efficient modelling of permanent magnet field distribution for deep learning applications

Permanent magnets are essential components in a range of applications from robotics to energy harvesting devices. Computing the field distribution of permanent magnets is crucial for designing and optimising these devices, but currently existing techniques, such as the Finite Element Method (FEM), are very time-consuming. Deep learning (DL) has been widely utilised to solve regression and classification problems and could enable an efficient computation of permanent magnet field distributions. However, deep learning requires large amounts of training data, which is difficult to obtain with current methods. In this work we represented the axial, azimuthal and radial components of the magnetic field created by permanent magnets and uniform magnetisations in semi-analytical expressions (SAE). These forms can be further simplified, and we validated these against the FEM for individual geometries such as an elliptical cylinder and a cone. The computational efficiency of the semi-analytical forms enables the generation of training datasets. Finally, we built a machine learning model using the training data generated by the SAEs and demonstrate that the machine learning model can predict the field distributions of permanent magnets in various configurations. The predicted magnetic field using the machine learning model is in good agreement with the ground-truth, with r2 for the axial, azimuthal and radial components being 0.999, 0.997 and 0.998, respectively for the magnetised elliptical cylinders, and 0.999, 0.999, 0.998 for the magnetised cones. Furthermore, the computational times of the machine learning models when executed on a CPU are more than 28 and 12 times faster than the SAEs of the elliptical cylinders and cones, respectively; the models are very fast to execute on a GPU with 22.7 s for the elliptical cylinders and 36.8 s for the cones. This work shows that it is possible to train a machine learning model to predict permanent magnet field distributions based on a training with semi-analytical expressions of various magnet geometries. The code for generating the training data, constructing the machine learning model and applying the model to new data is made openly available (https://github.com/vantainguyen/MagField_DataGen_Deep-learning).

The effect of the magnetic field distribution of permanent magnets on the trapped field properties of a single domain GdBCO bulk superconductor

The trapped field properties of a single domain GdBCO bulk superconductor with a diameter of 32 mm after being magnetized with different permanent magnets under a field cooling state at 77 K have been investigated. The results show that the maximum trapped field of the sample (Bmtr) is nearly saturated when the diameter of the permanent magnet d ≥ 20 mm, but the trapped magnetic flux of the sample (Φs) is nearly saturated when d ≥ 30 mm. This indicates that the largest trapped magnetic flux can be obtained when the size of the permanent magnet is close to that of the sample, and it is not necessary to use a more permanent magnet. In addition, a new and unusual phenomenon is found in that Φs is greater than the magnetic flux of the permanent magnet (ΦPM) when the diameter ratio between the permanent magnet and the sample is less than a certain value, such as 0.63 in this experiment. The relationship between Φs and ΦPM was well expressed as These results can provide a new method to design and control the trapped field properties of a single domain REBCO bulk superconductor during practical applications.

Wide-Field Planar Magnetic Imaging Using Spins in Diamond

The nitrogen-vacancy color centers in diamond can be used as an excellent magnetic sensor. In this work, we present a wide-field planar magnetic imaging technique based on nitrogen-vacancy color centers. Through optically detected magnetic resonance (ODMR) which is readout from a scientific CMOS camera to extract resonance frequency, we experimentally reconstruct the magnetic field distribution of permanent magnets and particles of magnetite (Fe3O4). Moreover, by using this method we imagined the magnetic field distribution of one integrated cell heater widely used in temperature control with magnetic field suppression. And the experiment shows that this technique can be applied in engineering. The imaging field of this technology can reach the sub-millimeter level and the spatial resolution can reach the optical diffraction limit. The presented wide-field NV imaging technique offers wide-field imaging, high spatial resolution, and high magnetic sensitivity.

Field-calibrated magneto-optic sensor based on off-axis optical probing of intense magnetic fields.

We present a magneto-optic sensing system based on the "off-axis" optical probing technique to control the measurement sensitivity of magnets with various field strengths. The magnetic field is experimentally investigated in the absolute scale through a photonic calibration method with a standard electromagnet. Our all-dielectric magnetic field probe has a wide dynamic range (20 mT-3 T) with good responsivity and low probe invasiveness against the magnetic field being measured. Utilizing this magnetic-field-calibrated probing system, we obtain the magnetic field distribution of permanent magnets. Subsequently, we compare our results with numerical analyses to confirm the effectiveness of the probing system. Finally, we measure the intense magnetic field inside the bore of a 3.0-T clinical magnetic resonance imaging system with our probe.

Modeling and validation of magnetic field distribution of permanent magnets

The results of three-dimensional modeling of the magnetic field distribution of permanent magnets were presented. The developed method for modeling the magnetic field distribution of the permanent magnet with the set geometric parameters was also given. For three-dimensional modeling, open source software ElmerFem, where calculations were performed by the finite element method was used. Experimental studies of the distribution of the magnetic field, originating from real magnets, in order to verify the model used in modeling were conducted. Correction of the model used in modeling was carried out based on the experimental studies. Verification of the developed method by modeling and measurement of permanent magnets was also performed. The results of experimental studies and theoretical modeling were almost identical, which validated the developed method for modeling the magnetic field distribution of permanent magnets. The developed method can be used in solving applied problems of calculating the three-dimensional distribution of magnetic fields of permanent magnets, which are used in designs of electric machines, electromagnetic transducers.

Simulation and testing of a micro electromagnetic energy harvester for self-powered system

This paper describes a low cost and efficient electromagnetic vibration energy harvester (EVEH) for a self-powered system. The EVEH consists of a resistant (copper) spring, a permanent magnet (NdFeB35) and a wire-wound copper coil. The copper spring was fabricated by the laser precision cutting technology. A numerical model was adopted to analyze magnetic field distribution of a rectangle permanent magnet. The finite element (FEM) soft ANSYS was used to simulate the mechanical properties of the system. The testing results show that the micro electromagnetic vibration energy harvester can generate the maximal power 205.38 μW at a resonance frequency of 124.2 Hz with an acceleration of 0.5 g (g = 9.8 ms−2) across a load the 265 Ω and a superior normalized power density (NPD) of 456.5 μW cm−3 g−2. The magnetic field distribution of the permanent magnet was calculated to optimize geometric parameters of the coil. The proposed EVEH has a high efficiency with the lower cost.

Magnetic Field Distribution of Permanent Magnet Magnetized by Static Magnetic Field Generated by HTS Bulk Magnet

Demagnetized rare earth magnets (Nd-Fe-B) can be fully magnetized by scanning them in the intense static fields over 3 T of a HTS bulk magnet which was cooled to the temperature range lower than 77K with use of cryo-coolers and activated by the field of 5 T. We precisely examined the magnetic field distributions of magnetized permanent magnets. The magnetic poles were ` in the narrow space on the surface of the permanent magnet with varying gap distances between the tracks of the HTS magnetic pole. Steep magnetic transitions between N and S were observed in the magnetic field distribution maps after the HTS magnetic poles were alternatively scanned for several times. The magnetizing method has been proposed for designing novel electromagnetic devices including magnetically excellent rare earth magnets which require intense magnetic fields over 3 T.

Non-Contact Driving Device of Artificial Heart and Its Magnetic Field Analysis

In order to fundamentally overcome the fatal shortcomings of the existing artificial heart that it needs a passageway through the skin for the energy supply, and the energy conversion components giving out heat in the human body, we use the permanent magnet located outside human body as a non-contact driving device of a blood pump. Only the blood pump is implanted into the body and the remaining parts are outside the human body. The blood pump located in the body and the drive unit located outside the body have a pair of permanent magnet. When the active magnet outside of the body rotates, its magnetic field changes, so that the passive magnet in the body follows the rotating active magnet. Because the device's operating performance depends on the magnetic field distribution of the permanent magnets in space, so we have to do the study in-depth on the permanent magnet magnetic field distribution, as well as the interaction between the two permanent magnets. In this paper, we analyse and calculate the magnetic field distribution and drive-torque characteristics of permanent magnet using finite element method. This research on the drive mechanism and drive characteristics of the non-contact permanent magnet power transmission system has laid a theoretical foundation for the optimal design of an artificial heart with the permanent magnet driving device.