• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.61-63
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• 1999

This paper presents an efficient method for analysis of magnetodynamic system using frequency-dependent parameters. In equivalent electric circuit of linear magnetodynamic system, parameters of inductance and resistance are not constant since they vary with its driving frequency. Once frequency-dependent parameters of equivalent electric circuit for a given system are extracted, they can be used to analyze various characteristics of system. We use the Fourier transform, the high-order sensitivity method and Taylor series in order to efficiently extract the frequency-dependent parameters of magnetodynamic system. The proposed algorithm is applied to an induction heating system to validate its numerical efficiency.

• Proceedings of the KIEE Conference
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• 1989.07a
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• pp.522-526
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• 1989

Recently developments of high-speed Semi-conductor Switches as Power MOSFETS, Power IGBT, power SIT have enwidened the performance of classical inverter configuration, and also allowed the practical applications of new inverter configuration, with improved performance and wider operating zones. Static power converters are now used in a great variety of applications including induction heating, high-frequency generation, DC/DC power converter, etc.

• Korean Journal of Metals and Materials
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• v.47 no.11
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• pp.754-758
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• 2009

Dense $5Cu_{0.6}Fe_{0.4}-Al_{2}O_{3}$ composite was consolidated from mechanically synthesized powders by high frequency induction heating method within 2 min. Consolidation was accomplished under the combined effects of a induced current and mechanical pressure. Dense $5Cu_{0.6}Fe_{0.4}-Al_{2}O_{3}$ with relative density of up to 95% was produced under simultaneous application of a 80 MPa pressure and the pulsed current. Fracture toughness and hardness of the composite are $7.6MPa{\cdot}m^{1/2}$ and $844kg/mm^{2}$ respectively.

• Korean Journal of Metals and Materials
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• v.48 no.11
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• pp.974-980
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• 2010

Various types of steel, namely, 0.35C, 0.2C-Cr, and 0.2C-Cr-Mo steels, were quenched and tempered by high-frequency induction heat treatment. The type, size, and spheroidization of the carbides varied depending on the tempering temperatures ($450{\sim}720^{\circ}C$). During the tempering process, the carbide was precipitated in the martensite matrix. The 0.35C, 0.2C-Cr, and 0.2C-Cr-Mo steels contained carbides that were smaller than 120 nm. The carbide was spheroidized as the tempering temperature increased. Owing to the fine microstructure and spheroidization of the carbides, all three steels had a high tensile strength as well as yield ratio and reduction of area. In the case of the 0.2C-Cr steel, the use of Cr as an alloying element facilitated the precipitation of alloyed carbides with an extremely small particle and resulted in an increase in the spheroidization rate of the carbides. As a result, a large reduction of area was achieved (>70%). The 0.2C-Cr-Mo steel had the highest tensile strength because of the high hardenability that can be attributed to the presence of alloying elements (Cr and Mo). Quenching and tempering steels by induction heat treatment resulted in a high strength of over 1 GPa and a large reduction of area (>70%) because of the rapid heating and cooling rates.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1190-1192
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• 2003

This paper presents a novel single-stage high frequency resonant inverter link type DC-DC converter using zero voltage switching with high input power factor. The proposed high frequency resonant converter integrates half-bridge boost rectifier as power factor corrector (PFC) and half-bridge resonant converter into a single stage. The input stage of the half-bridge boost rectifier is working in discontinuous conduction mode(DCM) with constant duty cycle and variable switching frequency. So that boost converter make the line current follow naturally the sinusoidal line voltage waveform. Experimental results have demonstrated the feasibility of the proposed DC-DC converter. This proposed converter will be able to be practically used as a power supply in various fields as induction heating applications, DC-DC converter etc.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.364-367
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• 2000

This paper describes a Push-Pull type high fre-quency resonant inverter conposed of consolidation of boost converter circuit and resonant circuit. By using a boost converter circuit the proposed inverter can obtain a twice input voltage of reson ant circuit and reduce a secondary turn ratios. By using both boost-converter and switching device can be reduce by half. Also the ana-lysis of the proposed circuit was described by using normalized parameter and operating characteristics have been evaluated as to switching frequency and parameters. In the future this pro-posed inverter shows that it can be practically used as a power source system for the lighting equipment of discharge lamp induction heating applications.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.1108-1113
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• 1992

In this paper, the high frequency twin resonant inverter using MOSFET is presented. The output control is excellent and the EMI noise is reduced, because the output appear as the vector sum of current in each unit inverter. The output voltage and the output current of the inverter are controlled by PLL. In this paper, the principle of the twin resonant method is described. And computer simulations and experimental results are shown.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.1154-1157
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• 1992

This paper presents a study on the current control method of the cycloconverters with high frequency LC resonant tank circuits for induction heating. The current control algorithms of the cycloconverters are proposed. Since the current waveforms of the cycloconverters have ripple, we proposed the compansation methods for that effects. And the performance of the current control system is considered with the results of the simulation by using the proposed current control algorithms.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.776-780
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• 2002

This paper describes the concept and the characteristics of hyper interfacial bonding developed as a new concept joining process for UFG (ultra-fine grained) steel. Hyper interfacial bonding process is characterized by instantaneous surface melting bonding which involves a series of steps, namely, surface heating by high frequency induction, the rapid removing of heating coil and joining by pressing specimens. UFG steels used in this study have the average grain size of 1.25 ${\mu}{\textrm}{m}$. The surface of specimen can be rapidly heated up and melted within 0.2s. Temperature gradient near heated surface is relatively steep, and peak temperature drastically fell down to about 1100K at the depth of 2~3mm away from the heated surface of specimen. Bainite is observed near bond interface, and also M-A (martensite-austenite) islands are observed in HAZ. Grain size increases with increasing heating power, however, the grain size in bonded zone can be restrained under 11 ${\mu}{\textrm}{m}$. Hardened zone is limited to near bond interface, and the maximum hardness is Hv350~Hv390.

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.271-279
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• 2015

Induction cooking application with multiple loads need high power inverters and appropriate control techniques. This paper proposes an inverter configuration with buck-boost converter for multiple load induction cooking application with independent control of each load. It uses one half-bridge for each load. For a given dc supply of $V_{DC}$, one more $V_{DC}$ is derived using buck-boost converter giving $2V_{DC}$ as the input to each half-bridge inverter. Series resonant loads are connected between the centre point of $2V_{DC}$ and each half-bridge. The output voltage across each load is like that of a full-bridge inverter. In the proposed configuration, half of the output power is supplied to each load directly from the source and remaining half of the output power is supplied to each load through buck-boost converter. With buck-boost converter, each half-bridge inverter output power is increased to a full-bridge inverter output power level. Each half-bridge is operated with constant and same switching frequency with asymmetrical duty cycle (ADC) control technique. By ADC, output power of each load is independently controlled. This configuration also offers reduced component count. The proposed inverter configuration is simulated and experimentally verified with two loads. Simulation and experimental results are in good agreement. This configuration can be extended to multiple loads.