A Theoretical Solution for the Magnetic Field in the Vicinity of a Recording Head Air Gap [Letter to the Editor]

1962 ◽  
Vol 6 (2) ◽  
pp. 260-262 ◽  
Author(s):  
E. E. Francis ◽  
T. C. Ku
Keyword(s):  
Magnetic Field ◽  
Air Gap ◽  
Theoretical Solution ◽  
Recording Head ◽  
Letter To The Editor ◽  
The Magnetic Field

scholarly journals Design of a New 1D Halbach Magnet Array with Good Sinusoidal Magnetic Field by Analyzing the Curved Surface

Sensors ◽  
2021 ◽  
Vol 21 (7) ◽  
pp. 2522
Author(s):  
Guangdou Liu ◽  
Shiqin Hou ◽  
Xingping Xu ◽  
Wensheng Xiao
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Permanent Magnet ◽  
Flux Density ◽  
Permanent Magnets ◽  
Air Gap ◽  
Curved Surface ◽  
Magnetic Flux Density ◽  
Sinusoidal Magnetic Field ◽  
The Magnetic Field

In the linear and planar motors, the 1D Halbach magnet array is extensively used. The sinusoidal property of the magnetic field deteriorates by analyzing the magnetic field at a small air gap. Therefore, a new 1D Halbach magnet array is proposed, in which the permanent magnet with a curved surface is applied. Based on the superposition of principle and Fourier series, the magnetic flux density distribution is derived. The optimized curved surface is obtained and fitted by a polynomial. The sinusoidal magnetic field is verified by comparing it with the magnetic flux density of the finite element model. Through the analysis of different dimensions of the permanent magnet array, the optimization result has good applicability. The force ripple can be significantly reduced by the new magnet array. The effect on the mass and air gap is investigated compared with a conventional magnet array with rectangular permanent magnets. In conclusion, the new magnet array design has the scalability to be extended to various sizes of motor and is especially suitable for small air gap applications.

Optimization of magnetic hat for quartz flexible accelerometer

Sensor Review ◽  
2016 ◽  
Vol 36 (1) ◽  
pp. 71-76 ◽  
Author(s):  
Cuo Wang ◽  
Xingfei Li ◽  
Ke Kou ◽  
Chunguo Long
Keyword(s):  
Magnetic Field ◽  
Field Distribution ◽  
Cylindrical Symmetry ◽  
Air Gap ◽  
Magnetic Sensors ◽  
Magnetic Field Distribution ◽  
Navigation Systems ◽  
Pole Piece ◽  
Content Type ◽  
The Magnetic Field

Purpose – This study aims to ameliorate the strength and uniformity of the magnetic field in the air-gap of quartz flexible accelerometers. Quartz flexible accelerometers (QFAs), a type of magneto-electric inertial sensors, have wide applications in inertial navigation systems, and their precision, linearity and stability performance are largely determined by the magnetic field in operation air-gap. To enhance the strength and uniformity of the magnetic field in the air-gap, a magnetic hat structure has been proposed to replace the traditional magnetic pole piece which tends to produce stratiform magnetic field distribution. Design/methodology/approach – Three-dimensional analysis in ANSYS workbench helps to exhibit magnetic field distribution for the structures with a pole piece and a magnetic hat, and under the hypothesis of cylindrical symmetry, two-dimensional finite element optimization by ANSYS APDL gives an optimal set of dimensions of the magnetic hat. Findings – Three structures of the QFA with a pole piece, a non-optimized magnetic hat and an optimized magnetic hat are compared by the simulation in ANSYS Maxwell and experiments measuring the electromagnetic rebalance force. The results show that the optimized hat can supply stronger and more uniform magnetic field, which is reflected by larger and more linear rebalance force. Originality/value – To the authors ' knowledge, the magnetic hat and its dimension optimization have rarely been reported, and they can find significant applications in designing QFAs or other similar magnetic sensors.

Design of the Superconducting Excitation Winding for 12 MW Direct-Drive Wind Generator

2014 ◽  
Vol 672-674 ◽  
pp. 217-221
Author(s):  
Lu Shun Su ◽  
Qing He ◽  
Jing Shi ◽  
Li Ren ◽  
Jie He ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Power Generation ◽  
Air Gap ◽  
Offshore Wind ◽  
Direct Drive ◽  
Offshore Wind Turbines ◽  
Superconducting Coils ◽  
The Stability ◽  
The Magnetic Field ◽  
Excitation Winding

Due to the high JC of the superconductor, the volume and the weight of the generator can be significantly reduced if the superconducting coils are used. This paper has designed a 40-pole racetrack excitation winding for the 12MW offshore wind turbines generator. The excitation winding are wound by Nb-Ti superconductor, running at the temperature of 4.2K. In order to ensure the stability and reliability of the magnetic field, some optimizers for the design of the excitation winding are adopted. As a result, the fundamental magnetic field at the air-gap center of the armature winding could reach 2.1T, thereby the 12MW power generation could be achieved.

Analytical calculation of magnetic field in surface-mounted permanent-magnet machines with air-gap eccentricity

2019 ◽  
Vol 38 (2) ◽  
pp. 893-914
Author(s):  
Jawad Faiz ◽  
Mohammadreza Hassanzadeh ◽  
Arash Kiyoumarsi
Keyword(s):  
Magnetic Field ◽  
Permanent Magnet ◽  
Field Distribution ◽  
Analytical Calculation ◽  
Air Gap ◽  
Magnetic Field Distribution ◽  
Magnetic Flux Density ◽  
Content Type ◽  
Air Gap Magnetic Field ◽  
The Magnetic Field

Purpose This paper aims to present an analytical method, which combines the complex permeance (CP) and the superposition concept, to predict the air-gap magnetic field distribution in surface-mounted permanent-magnet (SMPM) machines with eccentric air-gap. Design/methodology/approach The superposition concept is used twice; first, to predict the magnetic field distribution in slot-less machine with eccentric air-gap, the machine is divided into a number of sections. Then, for each section, an equivalent air-gap length is determined, and the magnetic field distribution is predicted as a concentric machine model. The air-gap field in the slot-less machine with eccentricity can be combined from these concentric models. Second, the superposition concept is used to find the CP under eccentricity fault. At this end, the original machine is divided into a number of sections which may be different from the one for slot-less magnetic field prediction, and for each section, the CP is obtained by equivalent air-gap length of that section. Finally, the air-gap magnetic field distribution is predicted by multiplying the slot-less magnetic field distribution and the obtained CP. Findings The radial and tangential components of the air-gap magnetic flux density are obtained using the proposed method analytically. The finite element analysis is used to validate the proposed method results, showing good agreements with the analytical results. Originality/value This paper addresses the eccentricity fault impact upon the air-gap magnetic field distribution of SMPM machines. This is done by a combined analysis of the complex permeance (CP) method and the superposition concept. This contrasts to previous studies which have instead focused on the subdomain method.

scholarly journals Analysis of Magnetic Forces in Axial-Flux Permanent-Magnet Motors with Rotor Eccentricity

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Xiaoting Zhang ◽  
Bingyi Zhang
Keyword(s):  
Magnetic Field ◽  
Permanent Magnet ◽  
Air Gap ◽  
Computational Time ◽  
End Effect ◽  
Permanent Magnet Motors ◽  
Axial Flux ◽  
Magnetic Forces ◽  
Rotor Eccentricity ◽  
The Magnetic Field

In this study, an analytical model is established to efficiently compute the magnetic field and unbalanced magnetic pull (UMP) in axial-flux permanent-magnet motors (AFPMMs). The effects of stator slotting, end effect, and rotor eccentricity on the magnetic field and forces were investigated. Static and dynamic eccentricities are analyzed and considered in the model. An effective function of the air gap permeance was introduced for effect of the stator slots to compute the flux density. A specific coefficient function is defined to calculate the end effect. A Fourier transform is used to compute the variations of the permanent-magnet remanence and the air gap permeance due to the slotted stator opposite to a slotless stator. The unbalanced magnetic forces were evaluated as a function of the air gap magnetic field using analytical equations. The proposed analytical method dramatically reduces the model size and computational time. It can be applied to the analysis of AFPMMs and is much faster than the three-dimensional finite element method (FEM). By comparing with the obtained using the FEM, the model results are validated.

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