Magnetic Permeability Of Core Research Articles

Permeability of Magnetic Cores with Air Gaps.

The influence of the geometric dimensions of the cut core and the number and size of air gaps on the effective permeability was investigated. Using dimensional analysis, an equation was obtained that relates the permeability of the cut core to the simplest dimensionless combination of the mean magnetic flux length l, single air gap length lg1, the cross-sectional area S of the core, and gap number ng. Permeability calculated from the geometric parameters of the cut core was compared with the effective permeability obtained using a two-dimensional FEMM simulation. Simulation has shown that the equation derived from dimensional analysis provides the best fit. The influence of each significant parameters l, lg1, ng, and S on cut core permeability is demonstrated. Experimental results have shown that an equation derived from dimensional analysis can be used to predict cut core permeability. In this case, one should take into account the residual air gap that forms after cutting the core. A method for assessing the residual air gap is proposed.

Investigation the influence of structure parameters on giant-magnetoimpedance effect measured by non-contact method

Purpose This paper aims to investigate the influence of structure parameters on giant-magnetoimpedance (GMI) effect measured by non-contact method. Design/methodology/approach The GMI sensor contains a Co-based internal magnetic core fabricated by laser cutting and an external solenoid. The influences of magnetic permeability of magnetic core and structure parameters on GMI effect were calculated in theoretical model. The output impedance, resistance, reactance and GMI ratio were measured by non-contact method using impedance analyzer. Findings Enhancing external magnetic field intensity can decrease the magnetic permeability of core, which has vital influences on the magnetic property and the output response of GMI sensor. In addition, increasing the width of magnetic core and the number of solenoid turns can increase the maximum GMI ratio. The maximum GMI ratio is 3,230% with core width of 6 mm and solenoid turns of 200. Originality/value Comparing with traditional contact-measured GMI sensor, the maximum GMI ratio and the magnetic field sensitivity are improved and the power consumption is decreased in non-contact measured GMI sensor. GMI sensor measured by non-contact method has a wide range of potential applications in ultra-sensitive magnetic field detection.

Trigger Method Based on Secondary Induced Overvoltage for Linear Transformer Drivers

In this paper, a triggering method based on secondary induced overvoltage for a linear transformer driver (LTD) is proposed and investigated by simulation. A detailed circuit model established for the LTD is chosen to study the effect of some factors on the feasibility of this triggering method. The considered factors include the permeability, equivalent resistance of energy loss, saturation of magnetic cores, and the delay of gas switches in LTD cavities. Simulation results indicate that high equivalent resistance and high permeability of magnetic cores are helpful in realizing this trigger method. However, the resistance plays a leading role. An equivalent resistance of more than 1.5 Ω favors the realization of this trigger. However, a relative permeability of even 25 has not produced a fatal menace to this triggering method. The feasibility of this triggering necessitates the available volt-second product of the present magnetic cores to be expanded twice. As for gas switches, the interval given by secondary induced overvoltage would likely be long enough to complete their breakdown. From simulation results, it is shown that LTD switches could be rapidly closed under the action of such an overvoltage pulse with a rise time of less than 10 ns.