• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.851_852
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• 2009

Shrink fitting which is assembling process to fix stator core on the motor frame is widely used at the mass production line of motors because of cost and productivity. This process produces compressive stress on a stator core, which causes negative effect for example, core and copper losses on motor performance. Magnetic properties of electrical steel are effected by both compressive and tensile and thermal stresses. Electromagnetic field analysis is considered one of the effective process since one can predict motor performance including core loss precisely. This method can consider non linear magnetic property with magnetic saturation which is typical electrical steel behavior. However this method is strongly depended on non linear magnetic data, one may have different calculation result whether considering mechanical stress or not. This study describes magnetic field analysis of a motor considering mechanical stress from shrink fitting. Analysis results are compared with each stress-free and stressed condition.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.27 no.2
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• pp.175-181
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• 2017

In the present work, to achieve high braking performance with restricted size, characteristics of magneto-rheological (MR) fluid brake is numerically investigated considering different magnetic core shapes. As a first step, structural configuration of the MR brakes are proposed with four different magnetic core shapes, such as single flat, single inclined, dual flat and dual inclined. To estimate braking performance of the proposed MR brakes, electromagnetic analysis is carried out and the results of magnetic field intensity distribution are observed. Based on the electromagnetic analysis results, braking torque of the MR brake is estimated according to magnitude of current input and results are discussed. It is observed that enhanced braking torque can be achieved by adopting the modified magnetic core shape under limited small size of the MR brake.

• Electrical & Electronic Materials
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• v.10 no.8
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• pp.813-818
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• 1997

In this study the thin film air core and magnetic core inductors consisting of planar coil and/or CoNbZr amorphous magnetic layers on a Si substrate were fabricated as spiral type by using rf magnetron sputtering and wet etching methods. The etchant solution was achieved by iron chloride solution(17.5 mol%) mixed with HF (20 mol%) during 150 sec which etched Cu films and CoNbZr/Cu/CoNbZr multi-layer films. They were about 10${\mu}{\textrm}{m}$ of thickness and 10$\times$10 mm$^2$of size. The properties of thin film magnetic core inductor were 400 nH of Q value at 10 MHz and the resonance frequency was about 300 MHz.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1191-1192
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• 2006

Eventhough Fe-6.5 wt.% Si alloy shows excellent magnetic properties, magnetic components made of the alloy are not totally because of its extremely low ductility. In order to overcome this demerit of alloy, 6.7 wt.% Si alloy powders were produced by gas atomization and then post-processed to form magnetic cores. By doing so, the total core loss could be minimized by reducing both hysteresis and eddy current loss. From our experiments, we were able to achive a core loss of $390mW/cm^3$ at 0.1 T and 50 kHz through proper processes and a permeability $\mu_{eff}$ of 68 at low frequency.

• Proceedings of the KIPE Conference
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• 2015.11a
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• pp.217-218
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• 2015

Two axial flux permanent magnet (AFPM) machines using soft magnetic composite (SMC) and lamination steel are studied. Generally stator cores of AFPM machines are manufactured using SMC because AFPM machines need 3 dimensional core structures. However, SMC cores have very disadvantages in magnetic properties. Especially permeability value is much lower than that of lamination steel, so magnetic field density is also lower. In terms of core losses, SMC cores have much larger loss values than lamination steel cores because SMC core can't be laminated. In this study, AFPM machine was designed using laminated steel, and iron losses in two machines using SMC and laminated steel were studied. Simulations were carried out by a commercial 3-D FEM tool.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.5
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• pp.351-356
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• 2018

Commonly, a live-line alarm can be used to measure the electric field strength of a high-voltage system to calculate its current, but it is hard to detect the electric field of shielded cables or concealed structures, such as underground distribution cables. Current sensors can detect the magnetic field in a single core wire, but they cannot determine the magnetic field about a double-core wire because the currents flow in opposite directions. Therefore, it is very difficult to detect certain current problems, such as a fault current in an extension line comprised of a double line. In this paper, to ultimately develop a sensor that can detect the current regardless of line conditions, we used a simulation to determine the concentration of the magnetic field dependent on the distribution of the external magnetic field and the path of each line's core.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.151-155
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• 2002

This paper presents a micro fluxgate magnetic sensor in printed circuit board (PCB). The fluxgate sensor consists of five PCB stack layers including one layer magnetic core and four layers of excitation and pick-up coils. The center layer as a magnetic core is made of a micro patterned amorphous magnetic ribbon with extremely high DC permeability of ∼100,000 and the core has a rectangular-ring shape. The amorphous magnetic core is easily saturated due to the low coercive field and closed magnetic path for the excitation field. Four outer layers as an excitation and pick-up coils have a planar solenoid structure. The chip size of the fabricated sensing element is 7.3${\times}$5.7m㎡. Excellent linear response over the range of -100${\mu}$T to +100${\mu}$T is obtained with 540V/T sensitivity at excitation square wave of 3V$\_$P-P/ and 360kHz. The very low power consumption of ∼8mW was measured. This magnetic sensing element which measures the lower fields than 50${\mu}$T, is very useful for various applications such as: portable navigation systems, military research, medical research, and space research.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.8
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• pp.977-983
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• 2007

Recently, the number of systems which utilize wireless power transmission to a receiving module in a short distance is increasing. For efficient use of receiving space, coils are wound around the ferrite core to produce electromotive force(emf) in suppling power by wireless transmission. This paper analyzed the magnetic flux density distribution in the ferrite core in magnetic field environment which is uniformly oriented along to a single axis at 125kHz. For numerical analysis, Ansoft Maxwell which is applying the FEM(Finite Element Method) method was used. We studied the variations of the gathered magnetic fluxes to the changes of the relative permeabilities of the ferrite cores. Also we calculated the magnetic flux variation by shaving the ferrite core off for the groove of coil winding. Results showed that using a small ferrite core in magnetic field at 100kHz band can increase the amount of magnetic flux $3{\sim}4 times$ than without the core. The magnetic flux decreased 23% by shaving the core 0.5 mm on the periphery of 4.75 mm radius core with the relative permeability 800.

• Proceedings of the Korean Magnestics Society Conference
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• 1997.11a
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• pp.48-49
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• 1997

• Journal of Magnetics
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• v.19 no.2
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• pp.146-150
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• 2014

The objective of this paper is to provide a comparison between two transverse flux rotary machines (TFRM) with different topologies of stator cores. Depending on how to make stator core with laminated steel sheets, the one topology is 'perpendicular stacking core' and the other is 'separated core'. Both of the two cores have been designed considering 3-dimensional (3-D) magnetic flux path with the same output power conditions, but the core losses are quite different and it causes different magnetic and thermal characteristics. For comparison of these two topologies of stator cores, therefore, core losses have been calculated and used as a heat source in no-load conditions, and the thermal stress has been also calculated. 3-D finite element method has been used for the magnetic field, thermal, and stress analysis to consider the 3-D flux path of the TFRM. After comparing the analysis results of the two topologies, experimental results are also presented and discussed.