The effect of magnetic shaking on nonoriented silicon steel rings
The effect of magnetic shaking on the incremental permeability of nonoriented silicon steel rings was studied. 50H470 silicon steel is a very popular and cheap material, but does not have a high incremental permeability. However, we achieved a value of 27 000 for the target field of 10 Hz, 0.05 A/m, which is comparable to commercial PC permalloy. We also measured the target field, which ranged from 0.05-5 A/m, 1 Hz-1 kHz. Magnetic shaking was effective at 60 Hz is effective at shaking field amplitudes 40-60 A/m, corresponding to a flux density of 0.2-0.6 B/sub s/. We also made ring samples from 50H470 steel plates produced by a nibbling machine and evaluated the effect of stress on their magnetic properties.
Low‐frequency characteristic of the enhanced incremental permeability by magnetic shaking
In order to analyze the mechanism of magnetic shaking, the permeability and the energy losses for a small amplitude, low‐frequency exciting field are studied under magnetic shaking in comparison with those under the normal condition (without shaking). The permeability and the energy losses were measured for a Metglas 2705M amorphous ribbon wound core by a lock‐in technique in the frequency range of 1–20 Hz under both magnetic shaking (2.7 A/m, 1 kHz) and the normal condition. The effects of the magnetic shaking on the domain wall pinning, the mean wall velocity, and the number of the active walls are described. The strong frequency dependence of the enhanced incremental permeability even at low frequency is explained as a result of these effects.
Multipole shaking field for magnetic shielding
The authors propose a novel method of magnetic shaking for enhancing the performance of ferromagnetic shielding. The method employs a new type of planar coil which generates higher-order multipole fields. Ferromagnetic shielding walls placed close to the planar coil can be suitably shaken by its field, whereas unwanted leakage of the shaking field into the shielded space can be avoided due to the highly localized nature of the multipole field. The configuration of the novel planar coil is similar to a square mesh in which alternating cells are clockwise or counterclockwise current loops. The shaking effect on the shielding performance and the leakage of the shaking field are evaluated using cylindrical shields and compared with results obtained with toroidal shaking coils. >