Earticle

전기를 이용한 가열 방식 중에 유도가열 방식은 다른 가열 방식에 비해 빠른 시간에 높은 효율로 원하는 온도를 얻을 수 있는 방식으로 수 십년 동안 산업 분야, 의료 분야 등에 사용되고 있다. 따라서 성능을 예측할 수 있도록 멀티 코일을 가진 유도가열 열해석이 필요하다. 단순한 형태의 코일이나 피가열체가 아닌 복잡한 형태의 유도 가열 밥솥에 대해 유한요소 해석법을 이용하여 열해석을 수행 하였다. 또한 열해석의 정확성을 입증하기 위해 기존모델에 대한 해석을 진행하여, 해석값과 실험값을 비교 하였고, 열해석 방법이 정확성을 확인하였다. 이 후, 피가열체의 재질 두께 변화와 멀티코일의 턴수 변화에 따른 온도변화를 통해 유도가열 밥솥 설계시 재질 혼용 사용 과 턴 수 최적화의 필요성을 확인하였다.

An induction heating technology in the group of electric heating methods have advantages of quick and accurate heating with high efficiency. It is widely used in a variety of home appliances, industrial, medical applications, etc. Therefore, thermal analysis of induction heating with multiple coils is needed to method for predict performance. Finite element analysis was used to induction heating cooker with complicated coil or jar shape that is not a simple shape to be studied. In addition, to verify the accuracy of the thermal analysis, the thermal analysis method confirmed the accuracy by comparing the analysis and the experiment Afterwards, the necessity of using mixed materials and optimizing the number of turns in the design of the induction cooker was confirmed by changing the thickness of the material to be heated and the temperature according to the change in the number of turns of the multi coil.

Due to its excellent processability, thermal conductivity and high corrosion resistance, copper tubes applied to heat exchangers are being joined through brazing to increase heat exchange efficiency. In order to improve performance, the issue of joint quality of copper tubes, a major member of heat exchangers, is emerging, so research is needed to obtain excellent joint quality of brazing joints that may be damaged. In this study, the quality change of joints according to process variables was studied through induction heating brazing experiments using high frequency. The depth of penetration, which indicates the quality of the junction, was measured, and the center position of the high-frequency electrode and the height of the electrode, which change the location of the heat source applied to the junction, were selected as process variables. Lastly, the thermal image data obtained between the brazing experiments were obtained and the joint quality according to the temperature gradient of the joint was analyzed.

The fabrication of curved hull plates is a critical process in shipbuilding, affecting both the structural integrity and hydrodynamic performance of vessels. This study investigates a hybrid forming method that combines induction heating and multi-point press forming to improve the accuracy and efficiency of curved plate production. The forming experiments were performed under various heating and pressing conditions to examine their effects on deformation behavior, forming accuracy, and surface quality. The results indicate that the hybrid forming approach effectively reduces processing time, minimizes spring-back, and enhances the precision of the formed geometry compared with conventional mechanical forming. These findings demonstrate the potential of hybrid forming as an efficient and reliable technique for manufacturing complex hull structures in modern shipbuilding.

건식 접합방법에 비하여 시멘트계 접합방법은 건축물의 다양한 접합시스템 가운데 가장 범용적으로 사용되며 조립성이 우수한 반면, 해체 등의 역공정에서 각 부재 및 부품의 분리･분해가 어려운 실정이다. 따라서 본 연구에서는 건축 부재 및 재료의 결합방법으로서 범용적으로 이용되는 시멘트계 접합부에 분해성을 부여하는 것을 목적으로 유도가열 메커니즘의 적용을 도모하였다. 연구결과, 유도가열에 의해 도전성 저항체가 삽입된 시멘트계 접합부의 분해효과를 확인할 수 있었으며, 철제망, 펀칭메탈, 강섬유가 혼입된 시멘트 모르타르는 고주파 출력 2.25kW 조건에서 약 60초 이내에 계면의 취약화가 가능하였다. 그러나 모르타르 내부 함수상태 및 폴리머 함유율에 따라 유도가열에 의한 폭렬현상이 나타나는 경우가 있었다.

Efficient maintenance and upgrading of a building during its lifecycle are difficult because a cementitious finish uses materials and parts with low disassembly properties. Additionally, the reuse and recycling processes during building demolition also present numerous problems from the perspective of environmental technology. In this study, an induction heating (IH) method was used to disassemble cementitious finish joints, which are widely used to join building members and materials. The IH rapidly and selectively heated and weakened these joints. The temperature elevation characteristics of the cementitious joint materials were measured as a function of several resistor types, including wire meshes and punching metals, which are usually used for cementitious finishing. The disassembly properties were evaluated through various tests using conductive resistors in cementitious joints such as mortar. When steel fiber, punching metal, and wire mesh were used as conductive resistors, the cementitious modifiers could be weakened within 60 s when high frequency output conditon is 2.25kW. But spalling phenomenon of mortar was occurred by induction heating according to moisture condition and polymer contens.

An induction plasma generator is very attractive for several industrial applications especially in material processing, so a high-frequency power supply class-E inverter is required to generate the magnetic field at frequency ranging from hundreds of kilohertz to tens of megahertz offer high efficiencies at high power densities. A resonant inverter based on zero voltage switching and an adaptive control via a backstepping based on Lyapunov theory and tuning functions control is used as a power supply for inductively Plasma generator. A second technique is applied as a linear quadratic regulator is used as a power supply for plasma generator. This type of control does not only keep the output current and the voltage in phase but also makes the system operating in zero-voltage-switching mode for constant and variable load. On the strategy design of the gains which are determined by minimizing a cost function which reduces the tracking error and the control signal. A recursive least squares (RLS) estimator identifies the plant parameters at different load conditions. The evaluation of the state variables is obtained by estimation using Kalman Filter. Simulation results verified that the proposed strategy has good performance to variable loads providing fast transient response.

On heavy load, the energy supplement in the starting process of Thyristor Power Supply for Parallel Resonant Induction Heating (TPSPRIH) has trouble in catching up its consumption which makes the system start more difficultly. Aimed at the puzzle, this paper proposes a starting strategy based on the analysis of parameters of heating inductor and starting circuit. Considered the process complexity in commonly used pre-charged circuit, it analyzed relationship among the parameters of heating inductor, the iron material and its filling status. Compared the supply speed with the decay characteristic of load circuit, the critical starting conditions of TPSPRIH on heavy load has been gotten, then derived the solving space of trigger angle of rectifier on energy providing. Based on the rated parameters of a typical system, the starting strategy of rectifier angle has been proposed. The simulation on different regions in the solving space has been made. The simulation result demonstrated the rationality and correctness. It probably provides a reference way for the reliable starting of TPSPRIH.

Owing to flat plate induction heating can’t guarantee to heat equally, especially the existence of no heated zone, it haven’t been used in these industrial fields like SMD which require high accuracy and easy to control while heating. But some places need its characteristic of contact heating, eco-friendly and high efficiency, for this reason, it is fundamental to research the heating style further as well as the no heating zone. Because induction heating is based on eddy current, firstly, the relationship between eddy current and induction heating is explained and several factors which would influence the eddy current are put forward. Then finite element analysis and calculation of eddy current field is mainly done. At last, the conclusion is obtained by analyzing the results of calculation. Due to the analysis above, after improving the structure of the iron plate, the problem of no heating zone is solved. At the same time, the efficiency evaluation is brought out. It can make the following research more easily.

기존 Induction Heating용 인버터의 경우, 일반적인 Half-Bridge 인버터를 사용하여 낮은 효율이 발생하기 때문에 고효율 구동이 어렵고, Single Switch 인버터를 사용할 경우 높은 전압 스트레스로 인해 고효율 및 고출력 IH 인버터 구동이 어려운 문제점이 있다. 본 논문은 Induction Heating용 인버터의 원가를 감소시키고 고효율/고출력을 낼 수 있는 스위치 내압 저감용 ZVS Signle Switch 인버터를 제안한다. 기존의 IH 구동용 인버터를 사용할 경우에는 낮은 효율 및 높은 스위치의 전압 스트레스 때문에, 회로의 전체적인 부피가 커지고 제작단가가 증가하는 단점이 있다. 반면 제안된 회로는 IH 구동용 스위치 내압 저감이 가능한 ZVS Single Switch 인버터로써, 단일 스위치 회로 구현과 영전압 스위칭을 통해 높은 효율로 인버터 구동이 가능하고, 스위치 내압을 감소하였기 때문에 회로의 부피 및 원가를 감소시킬 수 있는 장점을 갖는다. 본 논문에서는 제안된 회로의 이론적이 특성을 분석하고 모의실험을 통해 확인하였으며, 2.6kW급 IH 구동 인버터 회로에 적용하여 실험을 통해 우수성을 검증하였다.

기존 Induction Heating(IH) 인버터의 경우, 파라미터의 변화가 매우 크기 때문에 높은 Turn-off 전류에서 스위칭 하여 전력 손실이 매우 커지는 문제점이 있다. 본 논문은 고효율 IH 인버터를 위한 공진점 추적 제어 기법을 제안한다. 기존의 IH 직렬 공진형 인버터의 경우에는 높은 Turn-off 전류를 가지고 있기 때문에 손실이 매우 크고, Heat-sink 크기가 커지는 단점이 있다. 반면 제안된 공진점 추적 제어 기법을 적용한 IH 직렬 공진형 인버터는 Turn-off 전류가 매우 낮은 상태에서 영전압 스위칭을 하기 때문에, 전력 손실이 매우 작고 Heat-sink 최소화 및 고효율화가 가능한 장점을 갖는다. 본 논문에서는 제안된 공진점 추적 제어 기법의 이론적인 특성을 분석하고 모의실험을 통해 확인하였으며, 3.6kW급 IH 직렬 공진형 인버터회로에 적용하여 실험을 통해 우수성을 검증하였다.

In this paper, an all-metal domestic induction heating (IH) system that can quickly identify ferromagnetic and non-ferromagnetic pots considering temperature changes in the working coil is designed. Load modeling is performed after analyzing the parameters of the pot material and the central misalignment of the working coil. To improve the performance and stability of the all-metal IH cooking heater, a power curve-fitting model is used to design a control system that quickly responds to load parameter fluctuations. In addition, a power control algorithm is established to compensate for the reference value by reflecting the increase in working coil temperature during heating of the non-ferromagnetic pot. The validity of the proposed control algorithm for the all-metal IH is verified by experiments using a 3.2 kW all-metal IH cooking heater.

Heating by RF wave is divided into dielectric heating and induction heating. Dielectric heating and induction heating from outside the body have the compensatory heating pattern. While surface fat layer is heated by dielectric heating, it is not heated by induction heating. While the peripheral part at the middle of the electrodes is not heated by dielectric heating, it is heated by induction heating. By the simultaneous application both modalities, heating pattern seems to be more uniform and improved. Computer simulation of Finite Element Method (FEM) using ANSYS was conducted to dielectric heating with the results of above-mentioned feature. Theoretical considerations by the uniform RF magnetic field in a cylinder and textbooks support the feature of the above-mentioned heating pattern of induction heating. Further computer simulation of FEM using ANSYS will be conducted to simultaneous application of dielectric heating and induction heating to verify and will be reported.

In this Paper are described the indirect induction heated boiler and induction heated hot air producer using the voltage-fed series resonant high-frequency inverter which can operate in the frequency range from 20kHz to 50kHz. A specially designed induction heater, which is composed of laminated stainless assembly with many tiny holes and interconnected spot welding points between stainless plates, is inserted into the ceramic type vessel with external working coil. This working coil is connected to the inverter and turbulence fluid through this induction heater to moving fluid generates in the vessel. The operating performances of this unique appliance in next generation and its effectiveness are evaluated and discussed from a practical point of view.

Since the curved hull plate was made by a series of manufacturing process including cold bending, manual local heating and correction work, the accuracy of curved plate strongly depends on the proficiency of worker. So the demands on the automatic local heating system for curved hull plate have continuously increased and the various researches relevant to it have been performed. Generally, the heat sources used for local heating were flame and induction heat. In terms of initial cost, flame heating is in a better favorable position than induction heating. However, from the viewpoint of the control of heat, induction heating has more advantage. So the various researches related to apply the induction heating to the automatic forming system has been performed. The purpose of this study is to establish the proper capacity of high frequency induction heating system for forming the curved hull plate. In order to do it, the proper coil shape for local heating was designed and the efficiency of induction heating system was determined by comparing of temperature results obtained by FEA and experiment. With the results, the extensive FEA was performed to identify the effect of heated plate dimension, cooling method and the capacity of induction heating system on the amount of heat loss introduced by induction heating. Based on the results, the proper capacity of high frequency induction heating system was proposed.

본 논문에서는 Induction Heating(IH) 시스템에서 WBG 소자인 SiC MOSFET과 GaN Transistor의 Performance 비교를 통해서 소자의 적합성을 분석한다. SiC 및 GaN 소자를 직렬 공진형 컨버터로 구성된 IH 시스템에 적용하여 온도, 전압, 전류, Gate 저항 등을 고려한 도통 손실, 스위칭 손실, 역방향 도통 손실과 열 해석 프로그램을 통한 열 성능 등의 비교가 수행되며, 이를 통해 소자 적합성이 분석된다. 각 소자에 따른 IH 시스템에 대한 시뮬레이션을 수행하여, 이론적 손실 비교를 통한 소자 적합성 분석에 대한 타당성을 검증한다.

This research presents a new active auxiliary resonant snubber with for induction heating PWM high frequency inverter solving the problem of induction heating PWM high frequency inverter circuit which is using widely in the practical application of an induction heating apparatus, the soft switching operation and power control are impossible when the lowest power supply in the active auxiliary resonant snubber with for induction heating PWM high frequency inverter. The inverter circuit which is attempted by the on-off operation of a switch has the effect of reducing the power loss due to soft switching and high frequency switching. This confirms that power regulation is possible on a continuous basis from 0.25[kW] to 2.84[kW] where the duty factor(D) changes from 0.08 to 0.3 under zero current switching which operates by an asymmetrical pulse width modulating control. The power conversion efficiency is 95[%]. Due to these results, the active auxiliary resonant snubber for an induction heating PWM high frequency inverter is considered effective as a source of induction heating.

$\textbullet$ INTRODUCTION $\textbullet$ PRINCIPLE AND THEORY $\textbullet$ DESIGN OF THE SYSTEM $\textbullet$ EXPERIMENT RESULT $\textbullet$ CONCLUSION $\textbullet$ REFERENCE

In this paper, a novel type auxiliary active edge resonant snubber assisted zero current soft switching pulse modulation Single-Ended Push Pull (SEPP) series load resonant inverter using IGBT power modules is proposed for cost effective consumer high-frequency induction heating (IH) appliances. Its operating principle in steady state is described by using each switching mode's equivalent operating circuits. The new multi resonant high-frequency inverter with series load resonance and edge resonance can regulate its high frequency output power under a condition of a constant frequency zero current soft switching (ZCS) commutation principle on the basis of the asymmetrical pulse width modulation (PWM) control scheme. Brand-new consumer IH products using the proposed ZCS-PWM series load resonant SEPP high-frequency inverter using IGBTs is evaluated and discussed as compared with conventional high-frequency inverters on the basis of experimental results. In order to extend ZCS operation ranges under a low power setting PWM as well as to improve efficiency, the high frequency pulse density modulation (PDM) strategy is demonstrated for high frequency multi-resonant inverters. Its practical effectiveness is substantially proved from an application point of view.