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Magnetic flux
Published in William Bolton, Engineering Science, 2020
Lines of magnetic flux form closed paths; for example, for the iron ring shown in Figure 14.3(a) any one line of flux forms a closed path with, in this case, the entire flux path being in iron. The complete closed path followed by magnetic flux is called a magnetic circuit. The magnetic flux Φ in a magnetic circuit is analogous to the electric current I in an electric circuit (Figure 14.3(b)), a closed path being necessary for an electric current. The magnetic flux density B is the flux per unit cross-sectional area (B = Φ/A) and is analogous to the current per unit cross-sectional area of conductor (I/A).
Magnetostatic Field in Material Media
Published in Branislav M. Notaroš, Conceptual Electromagnetics, 2017
A magnetic circuit in general is a collection of bodies and media that form a way along which the magnetic field lines close upon themselves, i.e., it is a circuit of the magnetic flux flow. The name arises from the similarity to electric circuits. In practical applications, including transformers, generators, motors, relays, magnetic recording devices, etc., magnetic circuits are formed from ferromagnetic cores of various shapes, that may or may not have air gaps, with current-carrying windings wound about parts of the cores. Figure 5.13(a) shows a typical magnetic circuit. With assumptions that the field is restricted to the branches of the magnetic circuit including air gaps (flux leakage and fringing are negligible) and is uniform in every branch (air gap), we now apply the law of conservation of magnetic flux [Eq. (4.16)] to a closed surface S placed about a node (junction of branches) and the generalized Ampère’s law [Eq. (5.3)] to a contour C placed along a closed path of flux lines in a magnetic circuit, as indicated in Figure 5.13(b), to obtain ∮SB⋅dS =0→∑i=1MBiSi=0,∮CH ⋅dl =IC→∑j=1PHjlj=∑k=1QNkIkKirchhoff'slaws for magnetic circuits),
Multi-channel non-destructive testing of steel strip stress based on magneto-elastic effect
Published in Nondestructive Testing and Evaluation, 2023
Mingyang Yu, Bin Wang, Bo Li, Boyang Zhang, Qingdong Zhang
The change in the magnetisation state of some materials is accompanied by a change in the size of the material, a phenomenon known as the magnetostrictive effect. By contrast, the phenomenon in which such materials deform under the action of external force, changing their magnetisation accordingly is called the inverse magnetostriction effect, also known as the magneto-elastic effect [24]. The detection principle of using the magneto-elastic effect to detect the tensile stress state of steel strip is depicted in Figure 1. When the strip is under an unknown stress state, the magnetic parameters, such as permeability and magnetoresistance of the material, change according to the magneto-elastic effect. When the excitation probe has a constant magnetomotive force, the change in the magnetic resistance in the magnetic circuit causes the magnetic field distribution around the detection probe to change. According to the principle of electromagnetic induction, the electromotive force induced by the detection coil also changes. Therefore, changes in strip tensile stress are eventually converted into measurable electrical signals for non-destructive stress testing.
The Research on Correlated Sensitivity Factors of Flux-Regulation Capability for Axial–Radial Flux-Type Synchronous Motor with Hybrid Poles
Published in IETE Journal of Research, 2018
Hongbo Qiu, Wenfei Yu, Wei Wang, Yuanqing Mu, Weili Li, Cunxiang Yang
As shown in Figure 13, the thickness of PPMs (Wppm) has a small effect on air-gap flux density when the axial exciting current is 0 A. In addition, the flux-regulation capability of negative If was limited by the bypass effect. Therefore, the air-gap flux densities of motor with different Wppm are close. With the increase of positive exciting current, the bypass effect was completely counteracted. After the bypass effect was completely counteracted, the positive excitation flux started to provide the air-gap flux. In this stage, the saturation of rotor magnetic circuit is the key factor that affects the flux-regulation capability. The magnetic reluctance of rotor magnetic circuit is reduced by reducing the Wppm. Therefore, the reduction of Wppm could improve the adjusting ability. As shown in Figure 13, the motor-adjusting range with Wppm of 5 mm increased by 0.1 T from the situation of 8 mm. The adjusting multiple K is 1.41, 1.35, 1.3, and 1.27, when the Wppm is 5, 6, 7, and 8 mm, respectively.
Improvement of magnetic induction-wire sawing process using a magnetic system
Published in Materials and Manufacturing Processes, 2018
Wei Zhang, Chunyan Yao, Xuefeng Xu, Hejie Li, Kuangwei Li
The permeability of ferromagnetic material is larger than that of nonmagnetic material. In particular, the magnetic flux mainly walks along the path created by the substances with large magnetic permeability.[13] This provides a basic thought for the establishment of magnetic circuit concept. Permanent magnetic circuit uses a permanent magnet material that has strong magnetism as the energy source of magnetic field, then it provides a constant homogeneous magnetic field in a certain region. It takes up a small space, and its structure is simple because it does not need drive coil and power supply system. Hence, the energy consumption is very low.