Study On The Mid-Frenquency Induction Furnace System Of Parallel Resonance And Principle Of Energy Saving

Intermediate frequency induction heating equipment has basically replaced traditional cupola in foundry industry, its heating speed and emissions small. At present, parallel resonant intermediate frequency electric furnace with low input voltage are produced by most domestic factory. The voltages of 380V outputted by rectifier transformer can be shared with other equipment, low costs. Its defects are energy consumption high, more content of 5,7 times harmonic in input current and power factor lower. Aiming at the faults, through study of parallel resonant electric furnace, the author improved the main circuit of rectifier, control and protection circuitry, using rectifier-series rising-voltage circuitry, completed the energy-saving electric furnace transformation of low harmonic 800Kw, assembled proto and debugged, got good results. Mainly work:1、Studying the traditional three-phase input voltage of parallel resonant electric furnace system. That study:three-phase rectifier circuit input current harmonic content high, power factor low.2、Analysis the work principle of parallel resonant inverter circuit. Study and analysis the sweep frequency start-up circuit of parallel resonant electric furnace.3、Using the characteristics of energy distribution of parallel resonant electric furnace, analyses how to reduce losses of induction coil. Research the matching relation of induction coil number and frequency voltage, induction coil no-load current and load current, etc. The author proposes rectifier series circuit for rising DC voltage, then improving intermediate frequency voltag. Reduce the induction coil currents in the same power conditions.4、Using MATLAB/SIMULINK, drawing that 12 pulse rectifier series circuit.Study its characteristics of rising-voltage, and the problem of current harmonics. According to the changes of main circuit, improve rectifier control, inverter control, sweep frequency start and protection circuit. Completed the design of protection control principle diagram and assembly of power the cabinet, commissioning, and deliver the users.5、Contrast test of energy saving and harmonic. Compared with traditional three-phare rectifier parallel resonant,12-pulse rectifier paralllel resonant furnace saves the electricity about 10～15%. The 5、7times harmonic of current was greatly reduced, and in some extent, improve the power factor.