Magnetic loss

Magnetic heat generation results

Magnetic loss refers to magnetic material stay magnetization or Reverse magnetization In the process Work convert to heat Of phenomenon 。 It contains hysteresis 、 vortex And surplus loss Three types. In strong magnetic field In the process of magnetization, the former two types are dominant; In weak magnetic field magnetization When, some Material Science (e.g Ferrite ）The residual loss of accounts for a large proportion.

Hysteresis loss Irreversible magnetization from magnetic materials process 。 On static state Magnetic loss and Hysteresis loop Areal composition Proportional 。 In AC magnetic field magnetization At one cycle, divide the magnetic loss Eddy current loss In addition, there are Domain wall The consumption of acceleration and missile performance.

Under the action of AC magnetic field conductor Internal cause magnetic induction produce vortex , make magnet Heat, i.e Eddy current loss 。 At the same time, the eddy current generates a magnetic field opposite to the original AC magnetic field, and shield Has Magnetizing field stay magnet And make communication Magnetizing field strength Press index Attenuation Skin effect 。 In order to reduce eddy current loss and improve efficiency, it is necessary to increase the resistivity And make it into very thin sheets.

surplus Loss is in magnetization Relaxation process Caused by. his mechanism More complex, because Material Science Different.^[1]

Chinese name: Magnetic loss
Ferrite: Mainly residual loss and hysteresis loss
Metallic magnetic material: Mainly eddy current loss and hysteresis loss

Low frequency and weak magnetic field: Richter and Jordan losses
High frequency: Resonance loss
Abbreviation: Wm

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Basic concepts

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Magnetic loss Means magnetic material There is a part of energy Irreversibly transformed into heat The energy lost is called magnetic loss. Magnetic loss W m Including eddy current loss W e Hysteresis loss W h And other magnetic Relaxation Or residual loss caused by magnetic aftereffect W r , i.e W m = W e + W h + W r 。 In general, the magnetic loss is Ferrite Mainly including residual loss and Hysteresis loss ； In metallic magnetic materials, eddy current loss and hysteresis loss are the main ones.^[2]

Eddy current loss

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In an alternating magnetic field, the magnetic conductor electromagnetic induction Resulting in Eddy current , which causes magnetic field intensity H and Magnetic induction B Of amplitude and phase Uneven inside the material distribution , and make B Phase behind H And increase a part energy loss , called eddy current loss. The experimental study of some metallic magnetic materials shows that the measured magnetic loss is higher than the theoretical calculation Eddy current loss And quasi-static loss. experiment And theory The extra loss of the difference is called abnormal loss. Part of the abnormal loss comes from Domain wall Pass when moving electromagnetic induction Induced micro eddy current near domain wall; The other part is due to the pinning or deformation of domain walls. It is worth noting that the abnormal loss occurs in some metallic magnetic materials (such as Silicon steel sheets ）The total loss accounts for a large part.^[2]

Hysteresis loss

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Hysteresis loss It is due to the irreversible magnetization process (irreversible displacement of domain wall, Magnetic domain Irreversible rotation). In the case of quasi-static magnetization, the hysteresis loss and Hysteresis loop Of the measure of area become Proportional 。 In medium and strong alternating Under magnetic field, the hysteresis loss of some metal magnetic materials is suitable for Steinmetz type Empirical formula 。^[2]

Residual loss

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Residual loss refers to Eddy current loss All losses other than hysteresis loss. It is composed of magnetism with different mechanisms Relaxation process Caused by. stay Low frequency And weak magnetic field The residual loss is mainly the magnetic aftereffect loss, and frequency irrelevant. high frequency The lower residual loss mainly includes Dimensional resonance 、 Domain wall resonance And nature resonance Loss caused by, etc. stay Ferrite The residual loss is dominant.^[2]

Low frequency and weak magnetic field

Residual loss and frequency caused by magnetic aftereffect Domain wall displacement And magnetization vector Rotational Damping coefficient become proportion 。 There are roughly two types of losses: Richter type and Jordan type. The former and temperature Frequency related; The latter has little dependence on temperature and frequency. Richter type losses are mainly caused by impurity Diffusive Induction anisotropy Caused by. Jordan type loss is mainly caused by Thermal fluctuation Caused by. Ferrite Richter loss is due to valence electron stay Ions between spread Caused by.^[2]

HF and UHF

At 10 four Suprahertz high frequency And UHF regions, ferrite Magnetic spectrum Magnetic loss related Permeability Imaginary component μ "There may be several absorption peak , they correspond to resonance loss, which is also a kind of Relaxation Losses. As the frequency increases, these absorption peak Are caused by dimensional resonance Domain wall resonance , natural resonance and natural exchange resonance.^[2-3]

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