• Electrical & Electronic Materials
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• v.9 no.9
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• pp.891-899
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• 1996

A model for predicting the characteristics of elastic ferromagnetic materials having a moving gap was presented. Based on the model parameters concerning behavior of material, such as the instantaneous field intensity, attractive force between the poles, length of gap, and the induced current/ emf in the circuit can be determined from the numerical integrations of the governing equations derived. From the results of the model it is found that when dc emf is imposed on the circuit the current sharply rise and fall for very short duration then stabilize at extremely low level which depends mainly on elasticity, permeabilities and ratio of resistivity. Subsequently output emf is shown stabilized at constant value which depends on the previous parameters as well as the resistivity ratio of primary to secondary circuit after sufficient progress of time.

• Journal of the Korean Magnetics Society
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• v.12 no.5
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• pp.174-178
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• 2002

Ac magnetic field was changed in the vicinity of a flaw because of the distribution of eddy current within a conductor, when the magnetic field was applied to a conductor having a flaw. The flaw detection was performed by using Co-based amorphous wire sensor head. The wire has almost 0 magneto-striction and high permeability. An comparative uniform magnetic field was applied to a 1㎜ thick copper plate and a 25㎛ thick aluminum sheet conductor using spiral typed coil. The size of the coil has 40㎜$\times$40㎜ outer width and 8㎜$\times$8㎜ inner width. The copper plate and the aluminum sheet has 0.5㎜ and 0.1㎜ wide gap, respectively. The frequency range of applied field was 100㎑∼600㎑. The induced voltage difference of 2.5㎷ was obtained in the maximum voltage and minimum one measured across the gap of the 1mm thick conductor. In the case of aluminum sheet, 0.4㎷ was obtained. From this results, the effectiveness of Co-based amorphous wire was confirmed in the ECT technique.