• Journal of Magnetics
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• v.4 no.3
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• pp.73-75
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• 1999

By appliying an slternate pulsed magnetic field -generated by using a sequential ignition circuit and a magnet exciting circuit- with peak value of about 10 T to the rod type Nd based magnet Nd2Fe12.7Cr1.3B with length of 5 mm and diameter of 3.6 mm, the basic magnetic properties such as saturation magnetization, residual magnetization, coercivity, maximum energy products, magnetic anisotropy and anisotropic field are investigated with obtaining the major and minor J-H loops of the magnet. The increase in coercivity due to eddy currents in ac measurement of coercivity is calculated considering eddy current loss by analyzing a wave of generating magnetic field. The average coercivity calculated for the magnet is about 12.2 kOe, anisotropy magnetic field and anisotropic constant are measured as 60 kOe 2.43 Mj/$m^3$, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.5
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• pp.473-477
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• 2005

A Bi-2223 tape has been developed for power applications such as a fault current limiter, a power cable and a superconducting magnetic energy storage system. In such applications, the Bi-2223 tape carries time varying transport current and in addition experiences time varying external magnetic field. It is well known that the external magnetic field not only causes magnetization loss in the Bi-2223 tape, but also drastically increases transport loss due to a so-called 'dynamic resistance' We developed an evaluation setup, which can measure transport loss in external at magnetic fields. Using this equipment, we measured the dynamic resistances for various amplitudes and frequencies of an external at magnetic field perpendicular to the face in the tape. Simultaneously we investigated the effect of an external ac field on transport loss with different experimental conditions. This paper describes test results ana discussions on correlation between the dynamic resistance and the transport loss for the Bi-2223 tape.

• Journal of Magnetics
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• v.19 no.4
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• pp.399-403
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• 2014

We designed an ultra-high frequency (UHF: 300MHz to 3 GHz) ferrite circulator to investigate magnetic parameters, which are suitable for a self-biased GHz circulator design. The size of the ferrite disk was 1.58 mm in thickness and 13.5 mm in diameter. The saturation magnetization ($4{\pi}M_s$) of 3900 Gauss, internal magnetic field ($H_{in}$) of 1 kOe, and ferromagnetic linewidth (${\Delta}H$) of 354 Oe were used in circulator performance simulation. The simulation results show the isolation of 36.4 dB and insertion loss of 2.76 dB at 2.6 GHz and were compared to measured results. A Ni-Zn ferrite circulator was fabricated based on the above design parameters. An out-of-plane DC magnetic field ($H_0$) of 4.8 kOe was applied to the fabricated circulator to measure isolation, insertion loss, and bandwidth. Experimental magnetic parameters for the ferrite were $H_{in}$ of about 1.33 kOe and $4{\pi}M_s$ of 3935 Gauss. The isolation 43.9 dB and insertion loss of 5.6 dB measured at 2.5 GHz are in close agreement with the simulated results of the designed ferrite circulator. Based on the simulated and experimental results, we demonstrate that the following magnetic parameters are suitable for 2 GHz self-biased circulator design: $4{\pi}M_r$ of 3900 Gauss, $H_a$ of 4.5 kOe, $H_c$ greater than 3.4 kOe, and ${\Delta}H$ of 50 Oe.

• Transactions on Electrical and Electronic Materials
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• v.9 no.6
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• pp.265-272
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• 2008

In this paper, AC losses of long wire Bi-2223 tapes with different twist pitch of superconducting core were fabricated, measured and analyzed. These samples produced by a powder-in-tube method are multi-filamentary tape with Ag matrix. Also, it's produced by non-twist. The critical current measurement was carried out under the environment in Liquid nitrogen and in zero field by 4-prob method. And the Magnetic measurement was carried out under the environment of applied time-varying transport current by transport method. From experiment, the susceptibility measurements were conducted while cooling in a magnetic field. Flux loss measurements were conducted as a function of ramping rate, frequency and field direction. The AC flux loss increases as the twist-pitch of the tapes decreased, in agreement with the Norris Equation. Neutron-diffraction measurements have been carried out investigate the crystal structure, magnetic structures, and magnetic phase transitions in Bi-2223([Bi, Pb]:Sr:Ca:Cu:O).

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1021-1022
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• 2011

This paper presents the double side PM synchronous motor/generator for core loss reduction in flywheel energy storage system. The use of double PM rotor causes the elimination of core loss in no-load state of machine. Because flywheel rotational speed is reduced by core loss, double PM rotor is very effective in flywheel system. This paper suggests two types of double side PM rotor, Halbach magnetized array and parallel magnetized array. And characteristic comparison according to thickness of rotor back core is performed.

• Progress in Superconductivity and Cryogenics
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• v.6 no.4
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• pp.32-36
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• 2004

AC loss is one of the important parameters in HTS (High Temperature Superconducting) AC devices. Among the HTS AC power devices, the transformer is an essential part in electrical power system. But, AC loss is one of the most serious problems of the HTS transformer, especially with pancake windings, because high alternating magnetic field is applied perpendicularly to the surface of BSCCO wire in HTS windings of that, comparing with the other HTS AC power devices. For the reason above the calculation of AC loss generated in the HTS windings should be carried out in advance when designing the HTS transformer. In the paper we performed study for optimization of winding design to minimize the magnetization loss of HTS winding such as the spaces between pancake windings and operating temperature of HTS wire. The calculation of the AC loss was accomplished by 2-demensional Finite Element Method.

• Progress in Superconductivity and Cryogenics
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• v.9 no.1
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• pp.43-46
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• 2007

Solenoid coil is one of the commonly used one in superconducting power machines because it can produce uniform magnetic field at the center of the coil. Most of the AC loss in a solenoid coil is magnetization loss which is generated by the perpendicular magnetic field. This paper compares the electrical characteristics of two solenoid coils made of YBCO wire and BSCCO wire. We made and tested the BSCCO solenoid coil and YBCO solenoid coil which had the same number of turns and inner diameter. Number of turns and inner diameter of both coils were 30 turns and 10cm, respectively. AC loss of both coils were calculated by using the finite element method. Result shows that AC loss of YBCO coil was about 1/7 of that of the BSCCO coil when the current was 40A.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.851-853
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• 2002

Bi-2223도체의 종자계 손실에 대하여 실험적으로 조사하였으며, Bi-2223도체의 종자계 손실은 주파수에는 의존하지 않으며, 이는 수직 수평방향의 자장에 대한 자화손실처럼 히스테리시스손실이 지배적임을 의미한다. 또한 측정된 자계 손실은 절충 본수에도 그다지 의존하지 않으며, 필라멘트들 사이가 완전히 비결합된 모델로부터 계산된 손실에 더 유사하고, 수평방향의 자장에 대한 자화손실의 약 1/5정도로 작으며, 따라서 종자계 손실은 전력기기에서 그다지 중요하지 않음을 알수 있었다.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.15-17
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• 1995

Hysteresis motor is a synchronous machine which has simple structure and self-start characteristic but also has serious difficulties in numerical analysis. In this study, a finite element analysis for hysteresis motor considering the hysteresis characteristics is presented. The hysteresis model is the magnetization-dependent Preisach model which explains hysteresis phenomena very well. From this, we estimate the instantaneous torque, average torque and hysteresis loss of the rotor, considering slot and winding distribution.

• Journal of Magnetics
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• v.13 no.4
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• pp.170-172
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• 2008

Fe-6.5% Si alloys have good magnetic properties due to their high electrical resistivity, very low magneto-striction, and low crystalline anisotropy. Despite their strong potential, these alloys have seldom been used in magnetic applications because of the very poor ductility of Si-steel above 3.0 wt% Si [1-4]. It is difficult to achieve compressed Fe-6.5% Si powder cores with excellent properties because of the low density due to poor ductility. In compressed powder cores, high density is essential in order to obtain high magnetization and permeability. In this study, an attempt was made to produce Fe-3%Si powder cores because the Fe-3.0 wt% Si alloys have relatively good magnetic properties and room temperature ductility. Gas atomized Fe-3.0 wt% Si powder was compressed into toroid shape cores. By reducing the Si content to 3.0 wt%, the hysteresis loss could be greatly reduced and thus the total core loss could be minimized. The total core loss is 600 mW/$cm^3$ at 0.1 T and 50 kHz.