Research On Vacuum Furnace Closed Loop Control System Based On Induction Heating Power

Induction heating is a new kind of energy saving, no pollution, high efficiency heating mode. It is applied in more and more industrial fields with the advance of the induction heating technology. It has been widely used in the automobile manufacturing especially. A vacuum furnace closed loop control system based on induction heating is designed in this thesis in order to realize the surveillance and control in the vacuum environment of the casting process of the motor shell used in the new electric car.Firstly, the characters and application of the induction heating are discussed in brief. The current situation and trend of the induction heating power technology’s development are introduced. Basic principle of induction heating is explained. In the designing of the system series resonant induction heating power is determined as the foundation by contrasting and analyzing the series resonant induction heating power and the parallel resonant induction heating power. After contrasting and introducing the ways of power regulated for induction heating power, the phase-shifted PWM is chosen for regulating the system power and analyzed in detail. The feasibility of this power regulated mothed was confirmed through the MATLAB/SIMULINK.Advanced high-power insulated fate bipolar transistors is chosen as the inverter switching device in this thesis. The hardware and software of the control system was designed based on DSP TMS320F2812. The fast frequency automatic tracking the control is realized by using digital phase locked loop. The phase-shifted PWM and a close loop software PLL were designed to generate the adjustable phase shift of driving pulse for realizing the closed-loop control of the temperature in the casting process. The real-time data communication between the computer and DSP can be achieved by CAN bus. A long-range control of the casting process and displaying and recording temperature curve can be realized by building the monitoring interface using LabVIEW soft.This system has now been used in actual production which is intuitive and easy to control, has high control accuracy and overall efficiency and achieved good effect.