Research on the Induction Heating Technology using Load Temperature Estimation and High-Voltage Output

다국어 초록 (Multilingual Abstract)

The induction heater directly applies electrical energy to the target and heats it by thermal energy conversion, unlike the conventional heating method. There are advantages of heating performance, high efficiency, and cleanliness through this. Unlike the existing fossil fuel combustion type, a current of AC frequency is generated through a coil to generate a magnetic field. This magnetic field forms an eddy current at the target, and heat is generated in the part where the current inside the target is generated. This operation procedure is different from making carbon gas such as coal and petroleum LPG as by-products. It has the advantage of not making flames and by-products accordingly, and safe heating is possible through electrical control.
Application is roughly divided into domestic and industrial applications, and the research directions of the two fields are different. First of all, home applications focus on user convenience technology. For example, various studies have been conducted, such as a technology that enables operation in all-metal containers, a technology that reduces EMC emission caused by high frequency during operation, and estimating the temperature of the load. Among them, measuring the impedance of the load and estimating the temperature based on the impedance has expectations for automatic cooking in the future. Automatic cooking is a technique that informs the user of the recipe for the desired food and helps put the right ingredients at the right time. Estimating load impedance in the domestic cooker IH field to predict the state or temperature of cooking will serve as the basis for automatic cooking technology. In addition, it can be applied to secure safety by creating an alarm that informs water boiling alarm or overheating of the contents. In this thesis, user convenience technology has been studied for home applications by applying the above research direction.
In industrial applications, research is being conducted to increase output power and speed up the heating of loads. The industry is demanding a method of increasing the temperature of the load by increasing output power rather than user convenience technology. To achieve a high output IH, an output voltage should be increased, and a device capable of operating at a constant frequency should be used. When a full-bridge inverter is implemented using a MOSFET device, there is a limitation in manufacturing high-power IH due to manufacturing a withstand voltage protection circuit and an increase in the unit price of a switching device. Using more switching elements, it is difficult to reconstruct a system suitable for the output power to expand the output capacity. This thesis proposes a method of stabilizing the system and easily extending the output by manufacturing an induction heating inverter in a modular manner and connecting input-parallel output-series.
In this thesis, this study would like to present a design method for analyzing and producing induction heaters used as home cooking containers in the industry. In addition, for home cooking containers, user convenience technology was studied by adding impedance estimation technology. Industrial induction heaters constructed a modular inverter and increased the output voltage to study how to quickly heat and increase the range of operations that can be output. The above study was verified by simulation and experiment through a 2kW class induction heater.

목차 (Table of Contents)

• I. Introduction 1
• 1.1 Components of the Induction Heating System 3
• 1.2 Classifications of the IH System 6
• 1.3 The Contents of Thesis 8
• II. Design and Analysis of the IH System 10
• 2.1 Series Resonant Inverter 10
• 2.2 Effects of Operating Frequency and Temperature 13
• 2.3 Mathematical Analysis of IH Loads 16
• 2.4 Experiment Online and Offline Load 21
• 2.5 Conclusion 24
• III. Impedance Estimation for Domestic IH Applications 25
• 3.1 Impedance Estimation Method 26
• 3.2 Improving Estimation Accuracy 34
• 3.3 Analysis of Impedance-Temperature Correlation 40
• 3.4 Conclusion 46
• IV. High Power IH System Design for Industrial Applications 47
• 4.1 IH System with the Proposed IPOS Connection 47
• 4.2 Theoretical Backgrounds of IPOS-IH System 52
• 4.3 Analysis of IPOS-IH Operating Modes 54
• 4.4 Simulation & Experimental Results 58
• 4.5 Conclusion 64
• V. Conclusion of Thesis 66
• REFERENCES 68