• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.2
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• pp.137-142
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• 2011

In this paper, the fault current limiting and the hysteresys characteristics of a superconducting fault current limiter (SFCL) using magnetic coupling of two coils on the iron core with an air-gap were analyzed. The introduction of the air-gap in the SFCL with magnetically coupled two coils can suppress the saturation of the iron-core and, on the other hand, make the limiting impedance of the SFCL decreased, which results from the increase of the exciting current. To analyze the effect of the aig-gap on the fault current limiting characteristics of the SFCL, the hysteresys curves of the iron core comprising the SFCL were derived from the short-circuit experiment and the variation in the voltage-current trace of the SFCL during the fault period was analyzed. Through the comparison with the current limiting characteristics of the SFCL without air-gap, the air-gap could be confirmed to contribute to the suppression of the iron core's saturation through the increase of the SFCL's burden from the short-circuit current.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.1
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• pp.52-57
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• 2008

In the transformer that is used for the contactless power transmission system, the primary and secondary sides are separated structurally unlike general transformers. When the contactless transformer is built, it forms relatively bigger air gap than the general transformer. Thus it is difficult to transfer energy from the primary side input to the secondary side output with high power efficiently because of low coupling coefficient. This paper proposes a contactless transformer using the rectangular type core that maintains high coupling coefficient even when it has relatively large air gap. The performance characteristics of the proposed transformer are compared with the transformer using general EE core to the air gap variation. The proposed contactless system using rectangular type core and dc-dc full bridge converter, and the system using EE core type and dc-dc full bridge converter are respectively implemented and their performance characteristics are verified by the simulation and experiment.

• Journal of Magnetics
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• v.21 no.3
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• pp.374-378
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• 2016

The transformer used in an inverter type arc welding machine is designed to use high frequency in order to reduce its size and cost. Also, selecting core materials that fit frequency is important because core loss increases in a high frequency band. An inrush current can occur in the primary coil of transformer during arc welding and this inrush current can cause IGBT, the switching element, to burn out. The transformer design was carried out in $A_P$ method and amorphous core was used to reduce the size of transformer. In addition, sheet coil was used for primary winding and secondary winding coil considering the skin effect. This paper designed the transformer core with an air gap to prevent IGBT burnout due to the inrush current during welding and proposed the optimum air gap length.

• Transactions on Electrical and Electronic Materials
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• v.16 no.1
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• pp.37-41
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• 2015

The most common structure of the current transformer (CT) consists of a length of wire wrapped many times around a silicon steel ring passed over the circuit being measured. Therefore, the primary circuit of CT consists of a single turn of the conductor, with a secondary circuit of many tens or hundreds of turns. The primary winding may be a permanent part of the current transformer, with a heavy copper bar to carry the current through the magnetic core. However, when the large current flows into a wire, it is difficult to measure its magnitude of current because the core is saturated and the core shows magnetic nonlinear characteristics. Therefore, we proposed a newly designed CT which has an air gap in the core to decrease the generated magnetic flux. Adding the air gap in the magnetic path increases the total magnetic reluctance against the same magnetic motive force (MMF). Using a ferrite core instead of steel also causes the generation of low magnetic flux. These features can protect the magnetic saturation of the CT core compared with the steel core. This technique can help the design of the CT to obtain a special shape and size.

• Journal of the Korean Society of Industry Convergence
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• v.17 no.3
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• pp.103-112
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• 2014

BY the Transformers and reactors, the input electrical energy is converted into magnetic energy. At the end through the magnetic energy was passed at the output parameter. Specially At the flyback transformer or a reactor airgap were designed to contain more magnetic energy. But that work is very difficult for the optimal design. It is that Contradictions are between the length of the Air-gap, Winding inductance, DC bias. As to e Several conflicting conditions in order to determine the optimum Air-gap has a lot of experience and trial & error is necessary. The approach proposed in this paper, the auxiliary winding on the core attached to part of primary core, that by applying a DC voltage has a dramatic effect like Core with designed Air-gap. This inventiveness and advantage is to regulate arbitrarily the Saturation Flux Quantity by the input signal to secondary winding. Accordingly obtained the biggest effect is that increasing limits of the saturation current destined by the material and shape of the conventional core. In other words, that can decreas the size of the transformer and reactor, While maintaining the current saturation capacity. This paper, prove its effect as using the local flux saturation in transformers and reactors for research by the computer program using the finite element method (FEM) simulation, followed by actual experiment to verify

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.181-183
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• 1996

A novel model of an inductive superconducting fault current limiter with an inductive superconducting fault current limiter with the air-gap core was fabricated and tested. If its impedance is not high enough to limit the fault current, then destructive damage occurs in the power system. We attained a magnetic saturation under higher current by an effective air gap introduced in the core. The fault current was successfully limited to two times as much as the nominal current at a 60 Hz source having an effective voltage of 70 V. The fault current flowing under such conditions can be limited to a desired value without any fault current peak within 1/4 cycles.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.3
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• pp.125-132
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• 1993

On this study, magnetic force versus input currents is analyzed by modeling taper plunger type proportional electromagnet of ISC valve using the permernce method. And, the reliabiliy of simulation is verified by comparing the experimental values with the calaulate magnetic force. From the result of this study, it is found that the taper angles at plunger and core, the length of air gap between plunger and yoke are the prumary factors in designing taper plunget type proportional electromagnet. Magnetic force is decreased as a whole according to increasing the air gap between pluger and yoke, and vise versa. But, the magnetic force is not proportional to current, when the air gap is very small. In case of decreasing the taper angle of pluger, the stroke range of plunger where magnetic force is proportional to current becomes farther from core.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.2
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• pp.77-81
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• 2009

Air-gap was introduced to suppress the saturation of the iron core comprising the flux-lock type superconducting fault current limiter (SFCL) with parallel connection of two coils. However, the air-gap makes the impedance of this SFCL decreased and can result in unusefulness of the SFCL. To analyze the current limiting characteristics of the SFCL with the air-gap, the experimental circuit for short-circuit test was constructed. Through the comparison with the current limiting characteristics of the SFCL without air-gap, the merit and the demerit of the flux-lock type SFCL with the air-gap were discussed.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.678-681
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• 2000

Contactless battery charger with a "더" type core is proposed in this paper. The proposed take-apart transformer maintain a high coupling coefficient in spite of air gap. The ZV-ZCS method is used for the efficiency and stable opeation of the system.he system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.4
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• pp.759-765
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• 2011

This paper proposes an effective assistant model for considering the stator slot-opening effect on air gap flux density distribution in conventional interior-type permanent magnet (IPM) motor. Different from the conventional slot-opening effect analysis in surface-type PM (SPM) motor, a composite effect of slot-opening uniquely existing in IPM motor, which additionally causes enhancement of air gap flux density due to magnet flux path distortion in iron core between the buried PM and rotor surface. This phenomenon is represented by a proposed assistant model, which simply deals with this additional effect by modifying magnetic pole-arc using an effective method. The validity of this proposed analytical model is applied to predict the air gap flux density distribution in an IPM motor model and confirmed by finite element method (FEM).