Research On 20kW Electromagnatic Induction Heating Equipment Based On IGBT

Electromagnetic induction heating technology is different from traditional heating method, such as electro-thermal wire heating technology, far-infrared heating technology, and microwave heating technology. It has advantages in the aspects of contactless heating, energy-efficiency, pro-environment, and security. These advantages of induction heating make electromagnetic induction heating equipment not only popular in household appliances, but also in industrial field such as quenching, smelting. With the revolution of power semiconductor devices, electromagnetic induction heating gradually makes its direction towards higher-frequency, higher-capacity, and intellectualization in recent years. This thesis does a research on high-power, high-frequency induction heating equipment, which works at 20kHz/20 kW, based on half-bridge structure and shunt-resonant circuit, and this thesis study both on hardware circuit and software design.Though power devices such as MOSFET can work on higher frequencies, its output power is limited, as its conduction loss is high. To solve this problem, the IGBT, which makes higher-powered supplies possible, is produced. The IGBT(Insulated Gate Bipolar Translator),which is composed of BJT and MOSFET, is a kind of full-controlled and voltage-driven power semiconductor, and its merits are not only on high input impedance, as same as MOSFET, but also on low conduction voltage drop, as same as GTR. Using IGBT as the key switching device, this thesis analyzes the process of induction heating. The circuits consist of gear and temperature sensing part, PLL, shunt-resonant part,et.ac. The protecting circuits can realize intelligent monitoring and guarantee the induction heating equipment operates safely. Besides, this device can provide multi power gear, and the PLL can lock the IGBT at the resonant frequency. To the software design, S3F9454, the core chip, samples five analog signals, including signals of power gear, voltage gear, and temperature. Nixie tubes display the grade of every signal and the current temperature of the IGBT. The controlling system can shut down the device by turning off the driving signals, and make buzzer alarm when abnormal things happen. Furthermore, the relay will be opened when the gear of temperature is out of range, in case that the local temperature is over high. At last, the code can adjust the duty ratio to realize soft start.Finally, after testing the whole design, the results show that this design is reasonable. The induction heating equipment has stable output power, high efficiency, and satisfy the design index request.