• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.12
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• pp.1828-1835
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• 2012

In this paper, a conceptual design and a detailed design of novel cylindrical magnetic levitation stage is introduced. This is came from planar-typed magnetic levitation stage. The proposed stage is composed of cylinder-typed permanent magnet array and semi-cylinder-typed 3 phase winding module. When a proper current is induced at winding module, a magnetic levitation force between the permanent magnet array and winding module is generated. The proposed stage can precisely move the cylinder to rotations and translations as well as levitations with the magnetic levitation force. This advantage is useful to make a nano patterning on the surface of cylindrical specimen by using electron beam lithography under vacuum. Two methods are used to calculate required magnetic levitation forces. The one is 2D FEM analysis, the other is mathematical modeling. This paper shown that results of two methods are similar. An assistant plate is introduced to reduce required currents of winding module for levitations in vacuum. The mathematical model of cylindrical magnetic levitation stage is used for dynamic simulation of magnetic levitations. A lead-lag compensator is used for control of the model. Simulation results shown that the detail designed model of the cylindrical magnetic levitation stage with the assistant plate can be controlled very well.

• Proceedings of the KIEE Conference
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• 2007.04c
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• pp.150-152
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• 2007

The stator faults yield asymmetrical operation of induction machines, such as irregular current, torque pulsation, increased losses and decreased average torque. So it is necessary to detect the stator faults and develope the monitoring system for detecting faults including vibration and noise. This paper describes the method to analysis the induction motors with the stator winding inter-turn short for investigation of the asymmetrical operation during normal and transient states. And a simple method is used for the simulation and analysis of the induction machines with stator asymmetries. Finally, simulation results, finite element analysis and experimental ones are presented. The results can be useful for real-time on-line monitoring of an induction motor.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.586-588
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• 2001

Inner part of FRP specimen was made unidirectionally by pultrusion method and outer part of FRP was made by filament winding method to study the effect of fiber orientatons on the strength of FRP. The strength of bending and compression was simulated and evaluated. The results of simulated strength and evaluated strength were different greately each other. The stress which affect the feature of FRP was simulated to investigate the difference of the results between simulation and evaluation Shear stresses were investigated to the main stress to affect the fracture of FRP.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.402-405
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• 2002

This paper presented the characteristic of Heat-transfer on the winding composed with Epoxy-resin in a 50 kVA cast-resin dry type transformer The resin cast transformer is used widely in supplying electricity systems. However, to know the thermal characteristics of that is very useful in designing, manufacturing, and maintaining, there is no pertinent method to calculate this. In this paper, Based on the results of the physical characteristics and the simulation by commercial software using FEM method, we established the Prototype Model for this. According to that Model, an analysis on a variation of the hottest spot temperature was discussed as a function of thermal conductivity for the individual windings composed with Epoxy-resin. The thermal conductivity of the individual windings with reference to upper way was discussed.

• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.180-181
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• 2013

This paper represents an analysis of a leakage inductance for a toroidal type flyback transformer. The equation to calculate the leakage inductance is derived using its MMF diagram. The analysis for the different types of the cores and winding structures is also provided using the Maxwell 3D simulation. The winding structures minimizing the leakage inductance are finally discussed, from the simulation results.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.7
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• pp.1050-1060
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• 1994

This paper is a study on the computer simulation of the characteristics of the superconducting fault current limiter. Input variable parameters are apparent power, load resistance value, line resistance value and so on. Initial fault current 2 times larger than the trigger current is required to reduce the switching time of SFCL. The propagation velocity increases abruptly, the transport current is several times larger than the ciritical current. In this paper, the switching time is calculated to be 323$\mu$ sec, and the initial fault current is 19 times larger than the critical current. Because the trigger coils are bifilar winding, they have little impedance in superconducting state. After fault occurred, the limiting coil acts as a superconducting reactor and the trigger coils quench at a critical current. Without the SFCL in the circuit, fault current after the load impedence is shorted might be increased to 1100A. The fault current is, therefore, successfully limited by the superconducting limiting coil to 100A determined by the coil inductance.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.4
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• pp.247-255
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• 2018

This paper proposes a transformer design of a direct cell-to-cell active cell balancing circuit with a multi-winding transformer for battery management system (BMS) applications. The coupling coefficient of the multi-winding transformer and the output capacitance of MOSFETs significantly affect the balancing current transfer efficiency of the cell balancing operation. During the operation, the multi-winding transformer stores the energy charged in a specific source cell and subsequently transfers this energy to the target cell. However, the leakage inductance of the multi-winding transformer and the output capacitance of the MOSFET induce an abnormal energy transfer to the non-target cells, thereby degrading the transfer efficiency of the balancing current in each cell balancing operation. The impacts of the balancing current transfer efficiency deterioration are analyzed and a transformer design methodology that considers the coupling coefficient is proposed to enhance the transfer efficiency of the balancing current. The efficiency improvements resulting from the selection of an appropriate coupling coefficient are verified by conducting a simulation and experiment with a 1 W prototype cell balancing circuit.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.5
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• pp.229-237
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• 2001

Until recent years, most of the researches for motor drives focus on the high performance drive of the three phase induction motor, and that of the single phase induction motor(SPIM) is out of interest. The SPIM is widely used at low power level because it has the simple construction and economic advantage. In general such machine has both main winding and auxiliary winding. Conventionally, these winding are fed by only one single phase source, and the speed of the motor is not controlled. The SPIM with an auxiliary winding can be treated as an asymmetrical two phase machine. In this paper the space vector Equivalent circuit of SPIM is derived. For vector control of the SPIM the stator current must be decoupled into the flux producing component and the torque producing component. To accomplish decoupling control, the conventional method requires complex calculation and large computation time. We proposed the equivalent circuit referred to the rotor side, in this case only the stator resistances in the direct axis and the quadrature axis are different each other and the other parameters are represented to be equal. Thus the decoupling of the stator current is similar to that of the three phase induction motor. In this paper, the novel vector control system of the single phase induction motor is proposed. To verify the feasibility of this scheme, simulation and experimentation are carried out. The results prove the excellent characteristics for the dynamic response, which confirms the validity of the proposed system.

• Journal of IKEEE
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• v.27 no.4
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• pp.587-600
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• 2023

This paper presents an optimal design of the slim type high frequency transformer used in the LLC DC to DC resonant converter for 65-inch UHD-TV with the rated power of 315W. This paper also performs an optimal design of the slim type high frequency through core loss analysis, AC winding loss analysis, and optimization design of the winding arrangement of the LLC resonant transformer. Particularly, the high-efficiency and slim type high frequency transformer based on the obtained results from theoretical analysis in this paper is constructed in the interleaved and vertical winding structures of its transformer to realize the winding method of automatic type and minimize AC winding loss. The primary and secondary windings of the slim type high frequency transformer the vertical winding structure proposed in this paper used the Litz-wire windings, PCB and copper plate windings, respectively. Finally, an optimal design of the slim type high frequency transformer proposed in this paper was carried out through the experimental results to confirm the validity of theoretical analysis based on the simulation results using Maxwell 2D and 3D tool.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.6
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• pp.321-327
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• 2000

FRP has been used very much as high strength and electrical insulation materials. The fiber contributes the high strength and modulus to the composite. The main roles of the matrix in composite materials like FRP are to transmit and distribute stresses among the individual fibers. The fiber orientation in FRP has a great effect on the strength of FRP because the strength of FRP mainly depends on the strength of fiber. In this study, compressive and bending stresses of FRP rods were simulated and measured according to the winding orientation of glass fiber. Inner part of FRP was made unidirectionally by pultrusion method and outer part of FRP was made by filament winding method to give fiber orientation to the FRP. The shear stresses had great effect on the strength of FRP although the stress of parallel direction of FRP was much higher. The tendency of compressive and bending strengths with glass fiber orientation was different each other.