• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.801-803
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• 2001

On this study the motor design method with fairly good characteristics and control capability as well as cooling capability is presented with considering the magnetic effect due to ventilation hole, which is installed to prevent the temperature rise. When the input voltage rises due to critical variation in traction power supply system, the final ventilation hole is presented by checking the inductance parameter with clarifying the relation between saturation of the motor core and the ventilation hole.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.768-770
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• 2001

The topology optimizations of electromagnetic systems with the nonlinear and the eddy current effects are studied using the finite element method. The topology design sensitivity formulations of nonlinear magnetostatics and eddy current systems are derived using the adjoint variable method. A computer program is developed using object orient programming and applied to the topology optimization of a C-core actuator. A numerical study shows the effects of saturation and eddy current by comparing results of topology optimizations.

• Proceedings of the KIEE Conference
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• 1989.11a
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• pp.33-36
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• 1989

In designing reluctance motor, it is important to know the flux distribution of the inside of the motor. The reluctance motor which has axially laminated anisotropic(a.l.a.) rotor was proved to have high efficiency. To analyze this motor, it needs to consider the anisotropic characteristic of the rotor. This paper shows the flux distribution of the a.l.a. reluctance motor by finite element method (FEM) considering the anisotropic characteristic and the saturation of the core. And this paper shows the static torque for the variation of the stator dimension. This will be helpful to design the a.l.a. switched reluctance motor.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.7
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• pp.379-386
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• 2002

This paper deals with dynamic analysis method of a slotless type permanent magnet linear synchronous motor(PMLSM) using 3-dimensional space harmonic method. The results are good agreement with FEA results because that slotless type PMLSM has simple structure and no saturation of core. And then, Under open-loop control, starting characteristic is analyzed by voltage equation combining with dynamic equation. In order to obtain more accuracy results, this paper use instantaneous back-EMF and thrust instead of back-EMF constant and thrust constant.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1346-1348
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• 2001

Generally, Invar alloy shows very low thermal expansion characteristics, lower than $2{\times}10^{-6}$/K approximately. To apply Fe-Ni-Co-C Invar alloy as a core material for large ampacity transmission line we studied the effects of magnetic properties on coefficient of thermal expansion. The coefficient of thermal expansion(CTE) suddenly decreases with addition of a little carbon(0.08%), increases with the increasing carbon and has a constant value at the composition over than 1.0%C. The trend of Curie temperature change with carbon is similar with that of CTE. Therefore, the CTE has a linear relationship with Curie temperature. However, the CTE linearly decreases with the ratio of saturation magnetization and Curie temperature(${\sigma}_s/T_c$).

• Journal of the Korean Ceramic Society
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• v.38 no.6
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• pp.506-508
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• 2001

The ferrite plating with applying power ultrasound waves of 19.5 kHz and 600W enabled us to encapsulate entirely MnZn ferrite cores for transformers with Ni$\sub$x/Zn$\sub$y/Fe$\sub$3-x-y/O$_4$coating. Supplying a NH$_4$OH solution during the plating broke the limit of the solubility of Ni ions to ferrite-plated films. The electrical resistivity of the NiZn ferrite coating increased with increasing the Ni and Zn content, reaching 2.3${\times}$10$\^$5/Ωcm at the composition of Ni$\sub$0.24/Zn$\sub$0.30/Fe$\sub$2.46/O$_4$. The saturation magnetization was 540 emu/㎤. As a result, the MnZn ferrite cores were successfully encapsulated with the NiZn ferrite coatings for an insulation layer.

• Journal of Magnetics
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• v.20 no.4
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• pp.387-393
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• 2015

Torque ripple is necessarily generated in interior permanent magnet synchronous motors (IPMSMs) due to the non-sinusoidal distribution of flux density in the air gap and the magnetic reluctance by stator slots. This paper deals with an asymmetric rotor shape to reduce torque ripple which can make sinusoidal flux density distribution in the air gap. Meanwhile the average torque is relatively increased by the asymmetric rotor. Response surface method (RSM) is applied to find the optimum position of the permanent magnets for the IMPSM with improved torque performance. Consequently, an asymmetric structure is the result of RSM and the structure has disadvantage of a mechanical stiffness. Finally, the performance of suggested shape is verified by finite element analysis and structural analysis is conducted for the mechanical stiffness.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.11a
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• pp.389-394
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• 1996

The conceptual design of Korea Next Generation Reactor (KNGR), which is 3914 MWt PWR, includes the safety depressurization system (SDS) to comply with U.S. NRC's severe accident policy. In this analysis, it is assumed that three Monobloc Sebim valves are adopted for the SDS bleed valves of KNGR. The characteristic of Monobloc Sebim are modeled in the CE-FLASH-4AS/REM code for this analysis. The various feed and bleed (F&B) procedures with Sebim valves are investigated for total loss of feedwater (TLOFW) event. It is found that if operators open two out of three Sebim valves in conjunction with four HPSI pumps before hot leg temperature reaches saturation condition, the decay heat removal and core inventory make-up function can be successfully accomplished. Therefore, this F&B procedure can be used for mitigating the TLOFW event of the KNGR. This result also demonstrates the feasibility of adopting the Monobloc Sebim valves for the SDS of KNGR.

• Journal of the Korean Society of Safety
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• v.15 no.4
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• pp.56-61
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• 2000

The precise and reliable loss model for induction motor and converter system is very important in order to predict the efficiency performance of variable speed drives. This paper proposes an accurate loss model of induction motor and converter system. The motor losses, such as stator and rotor copper loss, core loss and stray loss, are considered for fundamental and harmonic frequencies. Also considered are the skin effect on rotor resistance, temperature effect on bath stator and rotor resistance, magnetizing inductance saturation, and friction and windage loss. All the above features are incorporated in a synchronous frame dynamic d-q equivalent circuit. The converter system, consisting of a diode rectifier and PWM transistor inverter, is modeled accurately for conduction and switching losses. Validity of the models, in both steady state and transient conditions, is verified by simulations.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.609-612
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• 2001

Rogowski coil is made having no ferromagnetic material in a core. So the coil cannot be driven into saturation. This result in that Rogowski coils may be calibrated at relatively low currents. and used with confidence at very high currents. However the lowest level of current that can be measured is limited by the sensitivity of the voltage measuring instrument and system noise. Therefore. geometrical effects were investigated in order to measure high sensitivity of low level current and the significant source of error was examined as well. In the results, the source of error was associated with coil designs. i.e. shape and uniformity of coil and a geometrical location of current source inside and outside of the Rogowski coil.