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Magnetic Circuit
Published in Warsame Hassan Ali, Samir Ibrahim Abood, Matthew N. O. Sadiku, Fundamentals of Electric Machines, 2019
Warsame Hassan Ali, Samir Ibrahim Abood, Matthew N. O. Sadiku
Magnetic circuits are those parts of devices that employ magnetic flux due to inducing a voltage. Such devices include generators, transformers, motors, and other actuators as solenoid actuators and loudspeakers. In such devices, it is necessary to produce magnetic flit. This is usually done with pieces of ferromagnetic. In this sense, the magnetic circuits are like the electric circuits in which conductive material such as aluminum or copper has high electric conductivity and are used to guide electric current. The analogies between electric and magnetic circuits are two: the electric circuit quantity of current is analogous to magnetic circuit quantity flth. The electric circuit quantity of voltage or electromotive force (EMF) is analogous to the magnetic circuit quantity of magnetomotive force (MMF). EMF is the integral of electric field E, and MMF is the integral of magnetic field H.
M
Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
magnetoimpedance the change in impedance of a ferromagnetic conductor experiencing a change in applied magnetic field. magnetomotive force (MMF) a magnetic circuit term referring to that phenomenon that pushes magnetic flux through the reluctance of the circuit path. MMF is analogous to the concept of electromotive force (voltage) in an electric circuit. For a magnetic core with a single coil of N turns, carrying current I , the MMF is N I , with units of amperes (sometimes expressed as ampere-turns). magnetoresistance the change in electrical resistance in a conducting element experiencing a change in applied magnetic field. This is most pronounced when the magnetic field is perpendicular to current flow. magnetostriction a change in the length of a ferromagnetic material as the flux changes under the influence of an applied magnetic field, or resulting from domain formation after cooling from above Curie temperature. In an AC device, the steel in the core expands and contracts twice each cycle, creating audible noise (e.g., transformer hum). magnetostrictive smart material one of a class of materials with self-adaptively modifiable elastic properties in response to a magnetic field applied in proportion to sensed stress-strain information. magnetotransport motion of electrons or holes in a conducting material in the presence of an applied magnetic field. magnetron any arrangement of magnets in a sputter deposition or etch system that provides the magnetic field required to trap electrons in closed loops near the cathode, thus enhancing deposition/etch rates.
Linear and Ideal Transformers
Published in Nassir H. Sabah, Electric Circuits and Signals, 2017
A useful analogy can be made between a magnetic system and an electric circuit. This analogy, developed in some detail in Section ST6.1 is summarized in Table 6.1.1. Magnetic flux is analogous to electric current, and magnetomotive force (mmf), which equals Ni, is analogous to voltage excitation, also known as electromotive force (emf). The concept of mmf is fundamental and will be used below. In fact, Ampere’s circuital law relates the line integral of magnetic field intensity H over a closed path to the mmf: ∮lHdl = Ni, where N is also the number of times the current is crossed in going around the closed path. Flux is the product of permeance and mmf, just as current is the product of conductance and voltage.
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.
Study on external magnetic field improving the capture of Fe-based fine particles by magnetic fibers with different arrangement structures
Published in Particulate Science and Technology, 2022
Li’an Zhang, Yongfa Diao, Minghao Chu, Fashan Zhou, Zihang Li, Henggen Shen
From these equations, the following can be determined.When r = 0, the magnetomotive force = 0 at the axis. Substituting this into Equation (6-1) reveals that A1 = 0.When r → ∞, the magnetomotive force generated by the magnetic fibers at infinity can be ignored, which is consistent with the magnetomotive force caused by the external magnetic field H. At this time = = 0. Substituting this into Equation (6-2) reveals that C2 = 0.When located on the surface of the magnetic fiber cylinder, because the magnetic field has a certain continuity, when r = a, H1r = H2r, = (1 represents the inside of the magnetic fiber, 2 represents the outside of the magnetic fiber).
Comparison of Electrical Quantity Characteristics with or without Neural Point on Load Side of 1400MVA Nuclear Power Turbo-generator
Published in Electric Power Components and Systems, 2019
Pin Lv, Baojun Ge, Peng Lin, Hongsen Zhao
Where E+, E̶ ,and E0 are the effective value of the positive sequence magnetomotive force, the negative sequence magnetomotive force and the zero sequence magnetomotive force, respectively, U+, U̶ ,and U0 are the effective value of the stator fundamental positive sequence voltage, the stator fundamental negative sequence voltage and the stator fundamental zero sequence voltage, respectively, X+, X̶ ,and X0 are the stator positive sequence reactance, the stator negative sequence reactance and the stator zero sequence reactance respectively, and I0 is the effective value of the stator fundamental zero sequence current. The three-sequence resistance and reactance is shown respectively as